Sample records for early cambrian time

  1. An early Cambrian greenhouse climate.

    PubMed

    Hearing, Thomas W; Harvey, Thomas H P; Williams, Mark; Leng, Melanie J; Lamb, Angela L; Wilby, Philip R; Gabbott, Sarah E; Pohl, Alexandre; Donnadieu, Yannick

    2018-05-01

    The oceans of the early Cambrian (~541 to 509 million years ago) were the setting for a marked diversification of animal life. However, sea temperatures-a key component of the early Cambrian marine environment-remain unconstrained, in part because of a substantial time gap in the stable oxygen isotope (δ 18 O) record before the evolution of euconodonts. We show that previously overlooked sources of fossil biogenic phosphate have the potential to fill this gap. Pristine phosphatic microfossils from the Comley Limestones, UK, yield a robust δ 18 O signature, suggesting sea surface temperatures of 20° to 25°C at high southern paleolatitudes (~65°S to 70°S) between ~514 and 509 million years ago. These sea temperatures are consistent with the distribution of coeval evaporite and calcrete deposits, peak continental weathering rates, and also our climate model simulations for this interval. Our results support an early Cambrian greenhouse climate comparable to those of the late Mesozoic and early Cenozoic, offering a framework for exploring the interplay between biotic and environmental controls on Cambrian animal diversification.

  2. Calibrating rates of early Cambrian evolution.

    PubMed

    Bowring, S A; Grotzinger, J P; Isachsen, C E; Knoll, A H; Pelechaty, S M; Kolosov, P

    1993-09-03

    An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began at approximately 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.

  3. Calibrating rates of early Cambrian evolution

    NASA Technical Reports Server (NTRS)

    Bowring, Samuel A.; Grotzinger, John P.; Isachsen, Clark E.; Knoll, Andrew H.; Pelechaty, Shane M.; Kolosov, Peter

    1993-01-01

    An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began about 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.

  4. Reconstruction of early Cambrian ocean chemistry from Mo isotopes

    NASA Astrophysics Data System (ADS)

    Wen, Hanjie; Fan, Haifeng; Zhang, Yuxu; Cloquet, Christophe; Carignan, Jean

    2015-09-01

    The Neoproterozoic-Cambrian transition was a key time interval in the history of the Earth, especially for variations in oceanic and atmospheric chemical composition. However, two conflicting views exist concerning the nature of ocean chemistry across the Precambrian-Cambrian boundary. Abundant geochemical evidence suggests that oceanic basins were fully oxygenated by the late Ediacaran, while other studies provide seemingly conflicting evidence for anoxic deep waters, with ferruginous conditions [Fe(II)-enriched] persisting into the Cambrian. Here, two early Cambrian sedimentary platform and shelf-slope sections in South China were investigated to trace early Cambrian ocean chemistry from Mo isotopes. The results reveal that early Cambrian sediments deposited under oxic to anoxic/euxinic conditions have δ98/95Mo values ranging from -0.28‰ to 2.29‰, which suggests that early Cambrian seawater may have had δ98/95Mo values of at least 2.29‰, similar to modern oceans. The heaviest and relatively homogeneous δ98/95Mo values were recorded in siltstone samples formed under completely oxic conditions, which is considered that Mn oxide-free shuttling was responsible for such heavy δ98/95Mo value. Further, combined with Fe species data and the accumulation extent of Mo and U, the variation of δ98/95Mo values in the two studied sections demonstrate a redox-stratified ocean with completely oxic shallow water and predominantly anoxic (even euxinic) deeper water having developed early on, which eventually became completely oxygenated. This suggests that oceanic circulation at the time became reorganized, and such changes in oceanic chemistry may have been responsible for triggering the "Cambrian Explosion" of biological diversity.

  5. A suspension-feeding anomalocarid from the Early Cambrian.

    PubMed

    Vinther, Jakob; Stein, Martin; Longrich, Nicholas R; Harper, David A T

    2014-03-27

    Large, actively swimming suspension feeders evolved several times in Earth's history, arising independently from groups as diverse as sharks, rays and stem teleost fishes, and in mysticete whales. However, animals occupying this niche have not been identified from the early Palaeozoic era. Anomalocarids, a group of stem arthropods that were the largest nektonic animals of the Cambrian and Ordovician periods, are generally thought to have been apex predators. Here we describe new material from Tamisiocaris borealis, an anomalocarid from the Early Cambrian (Series 2) Sirius Passet Fauna of North Greenland, and propose that its frontal appendage is specialized for suspension feeding. The appendage bears long, slender and equally spaced ventral spines furnished with dense rows of long and fine auxiliary spines. This suggests that T. borealis was a microphagous suspension feeder, using its appendages for sweep-net capture of food items down to 0.5 mm, within the size range of mesozooplankton such as copepods. Our observations demonstrate that large, nektonic suspension feeders first evolved during the Cambrian explosion, as part of an adaptive radiation of anomalocarids. The presence of nektonic suspension feeders in the Early Cambrian, together with evidence for a diverse pelagic community containing phytoplankton and mesozooplankton, indicate the existence of a complex pelagic ecosystem supported by high primary productivity and nutrient flux. Cambrian pelagic ecosystems seem to have been more modern than previously believed.

  6. Early Cambrian oxygen minimum zone-like conditions at Chengjiang

    NASA Astrophysics Data System (ADS)

    Hammarlund, Emma U.; Gaines, Robert R.; Prokopenko, Maria G.; Qi, Changshi; Hou, Xian-Guang; Canfield, Donald E.

    2017-10-01

    The early Cambrian succession at Chengjiang contains the most diverse Cambrian fossil assemblage yet described, and contributes significantly to our understanding of the diversification of metazoans in the Cambrian ;explosion;. The Cambrian Period occupies a transitional episode of global ocean chemistry, following the oxygenation of the surface ocean and of shallow marine environments during the Ediacaran Period, but prior to the establishment of a predominantly oxygenated deep ocean in the mid-Paleozoic. Despite recent attention, a detailed understanding of the chemical conditions that prevailed in early Cambrian marine settings and the relationship of those conditions to early metazoan ecosystems is still emerging. Here, we report multi-proxy geochemical data from two drill cores through the early Cambrian (Series 2) Yu'anshan Formation of Yunnan, China. Results reveal dynamic water-column chemistry within the succession, which progressively shifted from euxinic to oxic conditions during deposition of the Yu'anshan Formation. The Chengjiang biota occurs in strata that appear to have been deposited under an oxygen-depleted water column that may have supported denitrification, as in modern oxygen-minimum zones. The oxygenated benthic environments in which the Chengjiang biota thrived were proximal to, but sharply separated from, the open ocean by a persistent anoxic water mass that occupied a portion of the outer shelf. Oxygen depletion in the lower water column developed dynamically in response to nutrient availability and possibly at lower thresholds of productivity due to lower atmospheric oxygen concentrations in Cambrian. These findings suggest that the frequent development of oxygen-limiting conditions in continental margin settings provided an environmental barrier that may have affected biogeographic, ecological and evolutionary development of early metazoan communities.

  7. Lower Cambrian polychaete from China sheds light on early annelid evolution

    NASA Astrophysics Data System (ADS)

    Liu, Jianni; Ou, Qiang; Han, Jian; Li, Jinshu; Wu, Yichen; Jiao, Guoxiang; He, Tongjiang

    2015-06-01

    We herein report a fossilized polychaete annelid, Guanshanchaeta felicia gen. et sp. nov., from the Lower Cambrian Guanshan Biota (Cambrian Series 2, stage 4). The new taxon has a generalized polychaete morphology, with biramous parapodia (most of which preserve the evidence of chaetae), an inferred prostomium bearing a pair of appendages, and a bifid pygidium. G. felicia is the first unequivocal annelid reported from the Lower Cambrian of China. It represents one of the oldest annelids among those from other early Paleozoic Lagerstätten including Sirius Passet from Greenland (Vinther et al., Nature 451: 185-188, 2008) and Emu Bay from Kangaroo island (Parry et al., Palaeontology 57: 1091-1103, 2014), and adds to our increasing roll of present-day animal phyla recognized in the early Cambrian Guanshan Biota. This finding expands the panorama of the Cambrian `explosion' exemplified by the Guanshan Biota, suggesting the presence of many more fossil annelids in the Chengjiang Lagerstätte and the Kaili Biota. In addition, this new taxon increases our knowledge of early polychaete morphology, which suggests that polychaete annelids considerably diversified in the Cambrian.

  8. Early Cambrian origin of modern food webs: evidence from predator arrow worms.

    PubMed

    Vannier, J; Steiner, M; Renvoisé, E; Hu, S-X; Casanova, J-P

    2007-03-07

    Although palaeontological evidence from exceptional biota demonstrates the existence of diverse marine communities in the Early Cambrian (approx. 540-520 Myr ago), little is known concerning the functioning of the marine ecosystem, especially its trophic structure and the full range of ecological niches colonized by the fauna. The presence of a diverse zooplankton in Early Cambrian oceans is still an open issue. Here we provide compelling evidence that chaetognaths, an important element of modern zooplankton, were present in the Early Cambrian Chengjiang biota with morphologies almost identical to Recent forms. New information obtained from the lowermost Cambrian of China added to previous studies provide convincing evidence that protoconodont-bearing animals also belonged to chaetognaths. Chaetognaths were probably widespread and diverse in the earliest Cambrian. The obvious raptorial function of their circumoral apparatuses (grasping spines) places them among the earliest active predator metazoans. Morphology, body ratios and distribution suggest that the ancestral chaetognaths were planktonic with possible ecological preferences for hyperbenthic niches close to the sea bottom. Our results point to the early introduction of prey-predator relationships into the pelagic realm, and to the increase of trophic complexity (three-level structure) during the Precambrian-Cambrian transition, thus laying the foundations of present-day marine food chains.

  9. Early Cambrian origin of modern food webs: evidence from predator arrow worms

    PubMed Central

    Vannier, J; Steiner, M; Renvoisé, E; Hu, S.-X; Casanova, J.-P

    2006-01-01

    Although palaeontological evidence from exceptional biota demonstrates the existence of diverse marine communities in the Early Cambrian (approx. 540–520 Myr ago), little is known concerning the functioning of the marine ecosystem, especially its trophic structure and the full range of ecological niches colonized by the fauna. The presence of a diverse zooplankton in Early Cambrian oceans is still an open issue. Here we provide compelling evidence that chaetognaths, an important element of modern zooplankton, were present in the Early Cambrian Chengjiang biota with morphologies almost identical to Recent forms. New information obtained from the lowermost Cambrian of China added to previous studies provide convincing evidence that protoconodont-bearing animals also belonged to chaetognaths. Chaetognaths were probably widespread and diverse in the earliest Cambrian. The obvious raptorial function of their circumoral apparatuses (grasping spines) places them among the earliest active predator metazoans. Morphology, body ratios and distribution suggest that the ancestral chaetognaths were planktonic with possible ecological preferences for hyperbenthic niches close to the sea bottom. Our results point to the early introduction of prey–predator relationships into the pelagic realm, and to the increase of trophic complexity (three-level structure) during the Precambrian–Cambrian transition, thus laying the foundations of present-day marine food chains. PMID:17254986

  10. Early Cambrian Pentamerous Cubozoan Embryos from South China

    PubMed Central

    Han, Jian; Kubota, Shin; Li, Guoxiang; Yao, Xiaoyong; Yang, Xiaoguang; Shu, Degan; Li, Yong; Kinoshita, Shunichi; Sasaki, Osamu; Komiya, Tsuyoshi; Yan, Gang

    2013-01-01

    Background Extant cubozoans are voracious predators characterized by their square shape, four evenly spaced outstretched tentacles and well-developed eyes. A few cubozoan fossils are known from the Middle Cambrian Marjum Formation of Utah and the well-known Carboniferous Mazon Creek Formation of Illinois. Undisputed cubozoan fossils were previously unknown from the early Cambrian; by that time probably all representatives of the living marine phyla, especially those of basal animals, should have evolved. Methods Microscopic fossils were recovered from a phosphatic limestone in the Lower Cambrian Kuanchuanpu Formation of South China using traditional acetic-acid maceration. Seven of the pre-hatched pentamerous cubozoan embryos, each of which bears five pairs of subumbrellar tentacle buds, were analyzed in detail through computed microtomography (Micro-CT) and scanning electron microscopy (SEM) without coating. Results The figured microscopic fossils are unequivocal pre-hatching embryos based on their spherical fertilization envelope and the enclosed soft-tissue that has preserved key anatomical features arranged in perfect pentaradial symmetry, allowing detailed comparison with modern cnidarians, especially medusozoans. A combination of features, such as the claustrum, gonad-lamella, suspensorium and velarium suspended by the frenula, occur exclusively in the gastrovascular system of extant cubozoans, indicating a cubozoan affinity for these fossils. Additionally, the interior anatomy of these embryonic cubozoan fossils unprecedentedly exhibits the development of many new septum-derived lamellae and well-partitioned gastric pockets unknown in living cubozoans, implying that ancestral cubozoans had already evolved highly specialized structures displaying unexpected complexity at the dawn of the Cambrian. The well-developed endodermic lamellae and gastric pockets developed in the late embryonic stages of these cubozoan fossils are comparable with extant pelagic

  11. High-precision Temporal Calibration of the Early Cambrian Biotic and Paleoenvironmental Records: New U-Pb Geochronology from Eastern Yunnan, China.

    NASA Astrophysics Data System (ADS)

    Tsukui, K.; Ramezani, J.; Zhu, M.; Maloof, A. C.; Porter, S.; Moore, J.; Eddy, M. P.; Bowring, S. A.

    2016-12-01

    The Terreneuvian Epoch of the early Cambrian marks the global diversification of early animal life, as well as major perturbations to Earth's geochemical cycles. Understanding possible links between biotic evolution (e.g., emergence of skeletal animals) and the recognized changes in ocean chemistry requires a high fidelity chronostratigraphic framework for the early Cambrian records. One such chronostratigraphy was built by mapping local early Cambrian carbon isotope profiles onto a U-Pb age-calibrated marine carbonate δ13C record from Morocco, assuming global synchroneity of the observed δ13C trends. Here we present a direct test of this assumption using high-precision U-Pb geochronology (CA-ID-TIMS method) of ash beds from key lower Cambrian horizons throughout eastern Yunnan Province in South China. Preliminary age results from ash beds near the top of the Dengying Formation (Fm.) and the basal Daibu Member (Mb.) of the Zhujiaqing Fm. in multiple sections place the basal Cambrian negative δ13C excursion (BACE) in China at ca. 540.7-539.6 Ma. Our new U-Pb dates from the overlying Zhongyicun Mb. at the Meishucun and nearby sections improve significantly upon previous in situ U-Pb geochronology and constrain the onset of high-frequency δ13C oscillations in some sections to between 533.5 and 532.9 Ma. Most importantly, a new U-Pb date of ca. 526 Ma from the basal Shiyantou Fm. in the Xiaotan Section marks the termination of a >1 million year-long period of consistently positive (≥+4‰) δ13C values (ZHUCE) that is characteristic of many early Cambrian records worldwide. This date establishes a robust time correlation between ZHUCE in South China and its equivalent 5p excursion in Morocco and Siberia, and constrains the timing and duration of the largest positive δ13C anomalies in the Cambrian.

  12. Early Cambrian sipunculan worms from southwest China.

    PubMed

    Huang, Di-Ying; Chen, Jun-Yuan; Vannier, Jean; Saiz Salinas, J I

    2004-08-22

    We report the discovery of sipunculan worms from the Lower Cambrian Maotianshan Shale, near Kunming (southwest China). Their sipunculan identity is evidenced by the general morphology of the animals (sausage-shaped body with a slender retractable introvert and a wider trunk) and by other features, both external (e.g. perioral crown of tentacles, and hooks, papillae and wrinkle rings on the body surface) and internal (U-shaped gut, and the anus opening near the introvert-trunk junction). The three fossil forms (Archaeogolfingia caudata gen. et sp. nov., Cambrosipunculus tentaculatus gen. et sp. nov. and Cambrosipunculus sp.) have striking similarities to modern sipunculans, especially the Golfingiidae to which their evolutionary relationships are discussed. This study suggests that most typical features of extant sipunculans have undergone only limited changes since the Early Cambrian, thus indicating a possible evolutionary stasis over the past 520 Myr.

  13. Early Cambrian sipunculan worms from southwest China.

    PubMed Central

    Huang, Di-Ying; Chen, Jun-Yuan; Vannier, Jean; Saiz Salinas, J. I.

    2004-01-01

    We report the discovery of sipunculan worms from the Lower Cambrian Maotianshan Shale, near Kunming (southwest China). Their sipunculan identity is evidenced by the general morphology of the animals (sausage-shaped body with a slender retractable introvert and a wider trunk) and by other features, both external (e.g. perioral crown of tentacles, and hooks, papillae and wrinkle rings on the body surface) and internal (U-shaped gut, and the anus opening near the introvert-trunk junction). The three fossil forms (Archaeogolfingia caudata gen. et sp. nov., Cambrosipunculus tentaculatus gen. et sp. nov. and Cambrosipunculus sp.) have striking similarities to modern sipunculans, especially the Golfingiidae to which their evolutionary relationships are discussed. This study suggests that most typical features of extant sipunculans have undergone only limited changes since the Early Cambrian, thus indicating a possible evolutionary stasis over the past 520 Myr. PMID:15306286

  14. Early and middle(?) Cambrian metazoan and protistan fossils from West Africa

    USGS Publications Warehouse

    Culver, S.J.; Repetski, J.E.; Pojeta, J.; Hunt, D.

    1996-01-01

    Supposed Upper Proterozoic strata in the southwest Taoudeni Basin, Guinea and Senegal, and from the Mauritanide fold belt, Mauritania, have yielded mostly poorly preserved small skeletal fossils of metazoan and protistan origin. Problematic, but possible echinoderm material and spicules of the heteractinid sponge Eiffelia dominate the Taoudeni Basin assemblage. The age of the material is not certain but the paleontologic data suggest an Early Cambrian age for the stratigraphically lowest faunas, and a Middle Cambrian age is possible for the stratigraphically highest collections.

  15. Armored kinorhynch-like scalidophoran animals from the early Cambrian.

    PubMed

    Zhang, Huaqiao; Xiao, Shuhai; Liu, Yunhuan; Yuan, Xunlai; Wan, Bin; Muscente, A D; Shao, Tiequan; Gong, Hao; Cao, Guohua

    2015-11-26

    Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period.

  16. Armored kinorhynch-like scalidophoran animals from the early Cambrian

    PubMed Central

    Zhang, Huaqiao; Xiao, Shuhai; Liu, Yunhuan; Yuan, Xunlai; Wan, Bin; Muscente, A. D.; Shao, Tiequan; Gong, Hao; Cao, Guohua

    2015-01-01

    Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period. PMID:26610151

  17. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia

    NASA Astrophysics Data System (ADS)

    Lee, Michael S. Y.; Jago, James B.; García-Bellido, Diego C.; Edgecombe, Gregory D.; Gehling, James G.; Paterson, John R.

    2011-06-01

    Despite the status of the eye as an ``organ of extreme perfection'', theory suggests that complex eyes can evolve very rapidly. The fossil record has, until now, been inadequate in providing insight into the early evolution of eyes during the initial radiation of many animal groups known as the Cambrian explosion. This is surprising because Cambrian Burgess-Shale-type deposits are replete with exquisitely preserved animals, especially arthropods, that possess eyes. However, with the exception of biomineralized trilobite eyes, virtually nothing is known about the details of their optical design. Here we report exceptionally preserved fossil eyes from the Early Cambrian (~515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized `bright zone'. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.

  18. Proterozoic and early Cambrian protists: evidence for accelerating evolutionary tempo

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.

    1994-01-01

    In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was part of a broader radiation of "higher" eukaryotic phyla. Observed diversity levels for protistan microfossils increased significantly at this time, as did turnover rates. Coincident with the Cambrian radiation of marine invertebrates, protistan microfossils again doubled in diversity and rates of turnover increased by an order of magnitude. Evidently, the Cambrian diversification of animals strongly influenced evolutionary rates, within clades already present in marine communities, implying an important role for ecology in fueling a Cambrian explosion that extends across kingdoms.

  19. Carbon isotopic evidence for photosynthesis in Early Cambrian oceans

    NASA Astrophysics Data System (ADS)

    Surge, Donna M.; Savarese, Michael; Dodd, J. Robert; Lohmann, Kyger C.

    1997-06-01

    Were the first metazoan reefs ecologically similar to modern tropical reefs, enabling them to persist under oligotrophic conditions? We tested the hypothesis of ecological similarity by employing a geochemical approach. Petrography, cathodoluminescence, trace elements, and stable isotope analyses of primary precipitates of the Lower Cambrian Ajax Limestone, South Australia, indicate preservation of original C isotopic composition. All primary carbonate components exhibit C isotopic values similar to the composition of inorganically precipitated fibrous marine cements, suggesting that archaeocyaths and the calcimicrobe Epiphyton precipitated skeletal carbonate in equilibrium with ambient seawater in the absence of vital effects. Such data do not support the contention that archaeocyaths possessed photosymbionts. However, a +0.55‰ shift in δ13C occurs in reefs developed under shallower-water conditions relative to deeper reefs. This shift suggests the stratification of primary production in Early Cambrian oceans. The pattern is similar to that seen in the modern ocean, whereby significant photosynthesis modulates the C isotopic composition of the photic zone.

  20. The impact of deep-tier burrow systems in sediment mixing and ecosystem engineering in early Cambrian carbonate settings

    PubMed Central

    Zhang, Li-Jun; Qi, Yong-An; Buatois, Luis A.; Mángano, M. Gabriela; Meng, Yao; Li, Da

    2017-01-01

    Bioturbation plays a substantial role in sediment oxygen concentration, chemical cycling, regeneration of nutrients, microbial activity, and the rate of organic matter decomposition in modern oceans. In addition, bioturbators are ecosystem engineers which promote the presence of some organisms, while precluding others. However, the impact of bioturbation in deep time remains controversial and limited sediment mixing has been indicated for early Paleozoic seas. Our understanding of the actual impact of bioturbation early in the Phanerozoic has been hampered by the lack of detailed analysis of the functional significance of specific burrow architectures. Integration of ichnologic and sedimentologic evidence from North China shows that deep-tier Thalassinoides mazes occur in lower Cambrian nearshore carbonate sediments, leading to intense disruption of the primary fabric. Comparison with modern studies suggest that some of the effects of this style of Cambrian bioturbation may have included promotion of nitrogen and ammonium fluxes across the sediment-water interface, average deepening of the redox discontinuity surface, expansion of aerobic bacteria, and increase in the rate of organic matter decomposition and the regeneration of nutrients. Our study suggests that early Cambrian sediment mixing in carbonate settings may have been more significant than assumed in previous models. PMID:28374857

  1. Proterozoic and early Cambrian protists: evidence for accelerating evolutionary tempo.

    PubMed Central

    Knoll, A H

    1994-01-01

    In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was part of a broader radiation of "higher" eukaryotic phyla. Observed diversity levels for protistan microfossils increased significantly at this time, as did turnover rates. Coincident with the Cambrian radiation of marine invertebrates, protistan microfossils again doubled in diversity and rates of turnover increased by an order of magnitude. Evidently, the Cambrian diversification of animals strongly influenced evolutionary rates, within clades already present in marine communities, implying an important role for ecology in fueling a Cambrian explosion that extends across kingdoms. Images PMID:8041692

  2. The origin of crustaceans: new evidence from the Early Cambrian of China.

    PubMed Central

    Chen, J. Y.; Vannier, J.; Huang, D. Y.

    2001-01-01

    One of the smallest arthropods recently discovered in the Early Cambrian Maotianshan Shale Lagerstätte is described. Ercaia gen. nov. has an untagmatized trunk bearing serially repeated biramous appendages (long and segmented endopods and flap-like exopods), a head with an acron bearing stalked lateral eyes and a sclerite and two pairs of antennae. The position of this 520 million-year-old tiny arthropod within the Crustacea is supported by several anatomical features: (i) a head with five pairs of appendages including two pairs of antennae, (ii) highly specialized antennae (large setose fans with a possible function in feeding), and (iii) specialized last trunk appendages (segmented pediform structures fringed with setae). The segmentation pattern of Ercaia (5 head and 13 trunk) is close to that of Maxillopoda but lacks the trunk tagmosis of modern representatives of the group. Ercaia is interpreted as a possible derivative of the stem group Crustacea. Ercaia is likely to have occupied an ecological niche similar to those of some Recent meiobenthic organisms (e.g. copepods living in association with sediment). This new fossil evidence supports the remote ancestry of crustaceans well before the Late Cambrian and shows, along with other fossil data (mainly Early Cambrian in China), that a variety of body plans already coexisted among the primitive crustacean stock. PMID:11674864

  3. A highly redox-heterogeneous ocean in South China during the early Cambrian (˜529-514 Ma): Implications for biota-environment co-evolution

    NASA Astrophysics Data System (ADS)

    Jin, Chengsheng; Li, Chao; Algeo, Thomas J.; Planavsky, Noah J.; Cui, Hao; Yang, Xinglian; Zhao, Yuanlong; Zhang, Xingliang; Xie, Shucheng

    2016-05-01

    The ;Cambrian Explosion; is known for rapid increases in the morphological disparity and taxonomic diversity of metazoans. It has been widely proposed that this biological event was a consequence of oxygenation of the global ocean, but this hypothesis is still under debate. Here, we present high-resolution Fe-S-C-Al-trace element geochemical records from the Jinsha (outer shelf) and Weng'an (outer shelf) sections of the early Cambrian Yangtze Platform, integrating these results with previously published data from six correlative sections representing a range of water depths (Xiaotan, Shatan, Dingtai, Yangjiaping, Songtao, and Longbizui). The integrated iron chemistry and redox-sensitive trace element data suggest that euxinic mid-depth waters dynamically coexisted with oxic surface waters and ferruginous deep waters during the earliest Cambrian, but that stepwise expansion of oxic waters commenced during Cambrian Stage 3 (∼ 521- 514 Ma). Combined with data from lower Cambrian sections elsewhere, including Oman, Iran and Canada, we infer that the global ocean exhibited a high degree of redox heterogeneity during the early Cambrian, consistent with low atmospheric oxygen levels (∼ 10- 40% of present atmospheric level, or PAL). A large spatial gradient in pyrite sulfur isotopic compositions (δ34Spy), which vary from a mean of - 12.0 ‰ in nearshore areas to + 22.5 ‰ in distal deepwater sections in lower Cambrian marine units of South China imply low concentrations and spatial heterogeneity of seawater sulfate, which is consistent with a limited oceanic sulfate reservoir globally. By comparing our reconstructed redox chemistry with fossil records from the lower Cambrian of South China, we infer that a stepwise oxygenation of shelf and slope environments occurred concurrently with a gradual increase in ecosystem complexity. However, deep waters remained anoxic and ferruginous even as macrozooplankton and suspension-feeding mesozooplankton appeared during

  4. Late Cambrian - Early Ordovician turbidites of Gorny Altai (Russia): Compositions, sources, deposition settings, and tectonic implications

    NASA Astrophysics Data System (ADS)

    Kruk, Nikolai N.; Kuibida, Yana V.; Shokalsky, Sergey P.; Kiselev, Vladimir I.; Gusev, Nikolay I.

    2018-06-01

    The Cambrian-Ordovician transition was the time of several key events in the history of Central Asia. They were the accretion of Mariana-type island arc systems to the Siberian continent, the related large-scale orogeny and intrusions of basaltic and granitic magma and the formation of a huge turbidite basin commensurate with the Bengal Gulf basin in the western part of the Central Asian orogenic belt (CAOB). The structure of the basin, as well as the sources and environments of deposition remain open to discussion. This paper presents new major- and trace-element data on Late-Cambrian-Early Ordovician turbidites from different parts of the Russian Altai and a synthesis of Nd isotope composition and ages of detrital zircons. The turbidites share chemical similarity with material shed from weathered continental arcs. Broad variations of CIA (39-73) and ICV (0.63-1.66) signatures in sandstones suggest origin from diverse sources and absence of significant sorting. Trace elements vary considerably and have generally similar patterns in rocks from different terranes. On the other hand, there are at least two provinces according to Nd isotope composition and age of detrital zircons. Samples from eastern Russian Altai contain only Phanerozoic zircons and have Nd isotope ratios similar to those in Early Cambrian island arcs (εNdt + 4.4… + 5.4; TNd(DM)-2-st = 0.8-0.9 Ga). Samples from central, western, and southern parts of Russian Altai contain Precambrian zircons (some as old as Late Archean) and have a less radiogenic Nd composition (εNdt up to -3.6; TNd(DM)-2-st up to 1.5 Ga). The chemical signatures of Late Cambrian to Early Ordovician turbidites indicate a provenance chemically more mature than the island arc rocks, and the presence of zircons with 510-490 Ma ages disproves their genetic relation with island arcs. The turbidite basin formed simultaneously with peaks of granitic and alkali-basaltic magmatism in the western Central Asian orogen and resulted from

  5. Three-dimensionally preserved minute larva of a great-appendage arthropod from the early Cambrian Chengjiang biota

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Melzer, Roland R.; Haug, Joachim T.; Haug, Carolin; Briggs, Derek E. G.; Hörnig, Marie K.; He, Yu-yang; Hou, Xian-guang

    2016-05-01

    A three-dimensionally preserved 2-mm-long larva of the arthropod Leanchoilia illecebrosa from the 520-million-year-old early Cambrian Chengjiang biota of China represents the first evidence, to our knowledge, of such an early developmental stage in a short-great-appendage (SGA) arthropod. The larva possesses a pair of three-fingered great appendages, a hypostome, and four pairs of well-developed biramous appendages. More posteriorly, a series of rudimentary limb Anlagen revealed by X-ray microcomputed tomography shows a gradient of decreasing differentiation toward the rear. This, and postembryonic segment addition at the putative growth zone, are features of late-stage metanauplii of eucrustaceans. L. illecebrosa and other SGA arthropods, however, are considered representative of early chelicerates or part of the stem lineage of all euarthropods. The larva of an early Cambrian SGA arthropod with a small number of anterior segments and their respective appendages suggests that posthatching segment addition occurred in the ancestor of Euarthropoda.

  6. Paleomagnetism of Early Cambrian Itabaiana mafic dikes (NE Brazil) and the final assembly of Gondwana

    NASA Astrophysics Data System (ADS)

    Trindade, Ricardo I. F.; D'Agrella-Filho, Manoel S.; Epof, Igor; Brito Neves, Benjamim B.

    2006-04-01

    Paleomagnetic analysis on 15 early Cambrian mafic dikes from Itabaiana (Paraíba State) yielded a southern (northwestern) direction with steep upward (downward) inclination ( Dm = 167.5°, Im = - 63.7°, α95 = 7.3°). AF and Thermal demagnetization, thermomagnetic curves, and hysteresis results suggest that this component is dominantly carried by fine-grained SD magnetite. The high stability of this component and positive baked contact tests on three dikes indicate it represents a primary thermoremanent magnetization. Ar-Ar analysis on whole-rock samples from two sites provides a strong constraint on the age of the Itabaiana paleomagnetic pole (134.6° E, 34.9° S; A95 = 7.3, K = 28) defined by plateau ages of 525 ± 5 and 526 ± 4 Ma. This pole completely satisfies six out of the seven quality criteria proposed by Van der Voo [R. Van der Voo, The reliability of paleomagnetic data, Tectonophysics 184 (1990) 1-9.] and permits a tight constraint on the Early Cambrian sector of the Gondwana apparent polar wander path. Paleogeographic reconstructions consistent with the available paleomagnetic and geological record show that Gondwana was sutured along three major orogenies, the Mozambique (Brasilano/Pan-African) Orogeny (800-650 Ma), the Kuunga Orogeny (570-530 Ma) and the Pampean-Araguaia Orogeny (540-520 Ma). We suggest that after rifting away from Laurentia at the end of the Neoproterozoic, opening the Iapetus ocean, the Amazonian craton and minor adjoining blocks, such as Rio Apa and Pampia, collided with the proto-Gondwana by Cambrian times at ca. 530-520 Ma. Unless for small adjustments, Gondwana was completely formed by 525 Ma whose paleogeography is defined by the Itabaiana pole.

  7. Early Cambrian wave-formed shoreline deposits: the Hardeberga Formation, Bornholm, Denmark

    NASA Astrophysics Data System (ADS)

    Clemmensen, Lars B.; Glad, Aslaug C.; Pedersen, Gunver K.

    2017-09-01

    During the early Cambrian, the Danish island Bornholm was situated on the northern edge of the continent Baltica with palaeolatitudes of about 35°S. An early Cambrian (Terreneuvian) transgression inundated large areas of Baltica including Bornholm creating shallow marine and coastline environments. During this period, wave-formed shoreline sediments (the Vik Member, Hardeberga Formation) were deposited on Bornholm and are presently exposed at Strøby quarry. The sediments consist of fine- and medium-grained quartz-cemented arenites in association with a few silt-rich mudstones. The presence of well-preserved subaqueous dunes and wave ripples indicates deposition in a wave-dominated upper shoreface (littoral zone) environment, and the presence of interference ripples indicates that the littoral zone environment experienced water level fluctuations due to tides and/or changing meteorological conditions. Discoidal structures (medusoids) are present in the quarry, but due to the relative poor preservation of their fine-scale structures it is difficult to determine if the discoids represent true medusae imprints or inorganic structures. The preservation of the shallow-water bedforms as well as the possible medusae imprints is related to either the formation of thin mud layers, formed during a period of calm water when winds blew offshore for a longer period, or to the growth of bacterial mats. The orientation of the wave-formed bedforms indicates a local palaeoshoreline trending NE-SW and facing a large ocean to the north.

  8. Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda

    PubMed Central

    Ou, Qiang; Shu, Degan; Mayer, Georg

    2012-01-01

    Cambrian lobopodians are important for understanding the evolution of arthropods, but despite their soft-bodied preservation, the organization of the cephalic region remains obscure. Here we describe new material of the early Cambrian lobopodian Onychodictyon ferox from southern China, which reveals hitherto unknown head structures. These include a proboscis with a terminal mouth, an anterior arcuate sclerite, a pair of ocellus-like eyes and branched, antenniform appendages associated with this ocular segment. These findings, combined with a comparison with other lobopodians, suggest that the head of the last common ancestor of fossil lobopodians and extant panarthropods comprized a single ocular segment with a proboscis and terminal mouth. The lack of specialized mouthparts in O. ferox and the involvement of non-homologous mouthparts in onychophorans, tardigrades and arthropods argue against a common origin of definitive mouth openings among panarthropods, whereas the embryonic stomodaeum might well be homologous at least in Onychophora and Arthropoda. PMID:23232391

  9. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

    PubMed Central

    Yang, Jie; Ortega-Hernández, Javier; Gerber, Sylvain; Butterfield, Nicholas J.; Hou, Jin-bo; Lan, Tian; Zhang, Xi-guang

    2015-01-01

    We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion. PMID:26124122

  10. First U-Pb geochronology on detrital zircons from Early-Middle Cambrian strata of the Torgau-Doberlug Syncline (eastern Germany) and palaeogeographic implications

    NASA Astrophysics Data System (ADS)

    Abubaker, Atnisha; Hofmann, Mandy; Gärtner, Andreas; Linnemann, Ulf; Elicki, Olaf

    2017-10-01

    LA-ICP-MS U-Pb data from detrital zircons of the Ediacaran to Cambrian siliciclastic sequence of the Torgau-Doberlug Syncline (TDS, Saxo-Thuringia, Germany) are reported for the first time. The majority of 203 analysed zircon grains is Proterozoic with minor amount of Archean and Palaeozoic grains. The U-Pb ages fall into three groups: 2.8-2.4 Ga (3%), Neoarchean to earliest Palaeoproterozoic; 2.3-1.6 Ga (46%), early to late Palaeoproterozoic; 1.0-0.5 Ga (47%), Neoproterozoic to Cambrian. This age distribution is typical for the West African Craton as the source area and for Cadomian orogenic events in northwestern Gondwana. The samples show an age gap between 1.6 and 1.0 Ga, which is characteristic for West African provenance and diagnostic in distinguishing this unit from East Avalonia and Baltica. The dataset shows clusters of Palaeoproterozoic ages at 2.2-1.7 Ga, that is typical for western Gondwana, which was affected by abundant magmatic intrusions (ca. 2.2-1.8 Ga) during the Eburnean orogeny (West African craton). Neoarchean zircon ages (3%) point to recycling of magmatic rocks formed during the Liberian and Leonian orogenies. Ediacaran to earliest Cambrian rocks of the TDS originated in an active margin regime of the Gondwanan shelf. The following early Palaeozoic overstep sequence was deposited within rift settings that reflects instability of the West-Gondwanan shelf and the separation of terranes from Ordovician onward. The results of this study demonstrate distinct northwestern African provenance of the Cambrian siliciclastics of the TDS. Due to Th-U ratios from concordant zircon analysis, igneous origin from felsic melts is concluded as the source of these grains.

  11. Soft-part anatomy of the Early Cambrian bivalved arthropods Kunyangella and Kunmingella: significance for the phylogenetic relationships of Bradoriida

    PubMed Central

    Hou, Xianguang; Williams, Mark; Siveter, David J.; Siveter, Derek J.; Aldridge, Richard J.; Sansom, Robert S.

    2010-01-01

    Bradoriids are small bivalved marine arthropods that are widespread in rocks of Cambrian to Early Ordovician age. They comprise seven families and about 70 genera based on shield (‘carapace’) morphology. New bradoriid specimens with preserved soft-part anatomy of Kunmingella douvillei (Kunmingellidae) are reported from the Early Cambrian Chengjiang Lagerstätte of China together with, for the first time to our knowledge, a second bradoriid species with preserved soft parts, Kunyangella cheni (Comptalutidae). Kunmingella douvillei has a 10-segmented limb-bearing body with uniramous ninth and tenth appendages and a series of homogeneous, apparently (proximal parts not preserved) unspecialized post-antennal biramous limbs with setose leaf-shaped exopods. Each endopod consists of five podomeres. A presumed penultimate instar of Ky. cheni preserves remnants of three head and two trunk appendages, and the adult is reconstructed as having four head appendages. This material allows testing of the affinity of the Bradoriida. Kunmingella is identified as a stem crustacean in character-based analyses, through both morphological comparisons and cladistic reconstructions. Global parsimony analysis recovers a monophyletic Bradoriida as the sister group to crown crustaceans. PMID:20181565

  12. Origin and hydrology of a large, intact Early Cambrian paleocave system and its role in overlying fluidisation structures, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Mathieu, Jordan; Turner, Elizabeth C.; Rainbird, Robert H.

    2017-04-01

    Paleokarst is most commonly expressed as subtle stratigraphic surfaces rather than large void systems penetrating deeply into the paleo-subsurface. In contrast, a regional Precambrian-Cambrian unconformity on Victoria Island (NWT, Canada), is associated with exceptional exposure of large, intact Cambrian paleocaverns (100 m diameter; tens of m high). The paleocaves are distributed along a paleo-horizontal plane, and an associated gryke network is present in the 30-60 m of Neoproterozoic dolostone between cave rooves and the base of overlying Cambrian sandstone; both are filled by Cambrian sandstone. The formation and preservation of such karst features require aggressive dissolution along a stable paleo-water-table shortly before transgression and deposition of shallow-marine sand over the dolostone. During the transgression, the karst network acted as a conduit for flowing groundwater that was discharged through overlying, unconsolidated Cambrian shallow-marine sand, producing water-escape structures (sand volcanoes and their conduits). The conduits are preserved as cylindrical remnants of the sand volcanoes' feeder pipes. Sediment fluidisation was probably caused by variations in the hydraulic-head gradient in a meteoric lens near the Cambrian coastline under a tropical climate with abundant, probably seasonally variable rainfall that caused pulses in subsurface fluid flow. Spatial distribution of the paleocaves and sand volcanoes suggests their formation on the southeast side of a recently faulted horst of Proterozoic carbonate bedrock that formed a nearshore island during early Cambrian sea-level rise. Fluidisation structures such as those reported here have generally been difficult to interpret owing to a lack of data on the fluid hydraulics of the underlying aquifer. This is the first report linking the hydraulics of a well-characterised paleokarst to development of fluid-escape structures. Such structures are widely known from sandstones overlying the sub-Cambrian

  13. Tropical shoreline ice in the late Cambrian: Implications for earth's climate between the Cambrian Explosion and the Great Ordovician Biodiversification Event

    USGS Publications Warehouse

    Runkel, Anthony C.; MacKey, T.J.; Cowan, Clinton A.; Fox, David L.

    2010-01-01

    Middle to late Cambrian time (ca. 513 to 488 Ma) is characterized by an unstable plateau in biodiversity, when depauperate shelf faunas suffered repeated extinctions. This poorly understood interval separates the Cambrian Explosion from the Great Ordovician Biodiversification Event and is generally regarded as a time of sustained greenhouse conditions. We present evidence that suggests a drastically different climate during this enigmatic interval: Features indicative of meteoric ice are well preserved in late Cambrian equatorial beach deposits that correspond to one of the shelf extinction events. Thus, the middle to late Cambrian Earth was at least episodically cold and might best be considered a muted analogue to the environmental extremes that characterized the Proterozoic, even though cooling in the two periods may have occurred in response to different triggers. Such later Cambrian conditions may have significantly impacted evolution preceding the Ordovician radiation.

  14. Compilation and network analyses of cambrian food webs.

    PubMed

    Dunne, Jennifer A; Williams, Richard J; Martinez, Neo D; Wood, Rachel A; Erwin, Douglas H

    2008-04-29

    A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple "niche model," which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid diversification of species, body

  15. Earth's magnetic field strength in the Early Cambrian: Thellier paleointensity estimates of Itabaiana mafic dykes, Northeast Brazil

    NASA Astrophysics Data System (ADS)

    Trindade, R. I. F.; Macouin, M.; Poitou, C.; Chauvin, A.; Hill, M.

    2012-04-01

    Thellier's paleointensity and microwave paleointensity experiments were carried out in Early Cambrian dykes from Itabaiana (NE Brazil) dated at 525 ±5 Ma. A previous paleomagnetic study on these dykes reveals a very stable characteristic component, whose thermoremanent nature is confirmed by positive baked contact tests performed in three different dykes. The main magnetic carrier is Ti-poor to pure magnetite in the PSD to SD domain state. Hysteresis parameters and first-order reversal curve (FORC) diagrams will be presented in order to apprehend the two different behaviors that characterize the samples during paleointensity experiments. From the 96 samples (from 13 dykes) analyzed in two laboratories using slightly different Thellier's experimental protocols, we have retained 12 samples (3 dykes) for paleointensity estimates. Paleointensity values range from 18.1 up to 40 μΤ. This corresponds to equivalent VDMs of 4.3 ± 0.5, 4.4 ± 1.4 and 5.3 ± 0.9 x 1022 Am2, for the three dykes respectively. These results, the first obtained for rapidly cooled Cambrian rocks, document a moderate Earth field in the Precambrian-Cambrian transition.

  16. Fossils, molecules and embryos: new perspectives on the Cambrian explosion

    NASA Technical Reports Server (NTRS)

    Valentine, J. W.; Jablonski, D.; Erwin, D. H.

    1999-01-01

    The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period. Evidence of metazoan activity in both trace and body fossils then increased during the 13 million years leading to the explosion. All living phyla may have originated by the end of the explosion. Molecular divergences among lineages leading to phyla record speciation events that have been earlier than the origins of the new body plans, which can arise many tens of millions of years after an initial branching. Various attempts to date those branchings by using molecular clocks have disagreed widely. While the timing of the evolution of the developmental systems of living metazoan body plans is still uncertain, the distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian. However, it is likely that much genomic repatterning occurred during the Early Cambrian, involving both key control genes and regulators within their downstream cascades, as novel body plans evolved.

  17. Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil.

    PubMed

    Parry, Luke A; Boggiani, Paulo C; Condon, Daniel J; Garwood, Russell J; Leme, Juliana de M; McIlroy, Duncan; Brasier, Martin D; Trindade, Ricardo; Campanha, Ginaldo A C; Pacheco, Mírian L A F; Diniz, Cleber Q C; Liu, Alexander G

    2017-10-01

    The evolutionary events during the Ediacaran-Cambrian transition (~541 Myr ago) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in the Early Cambrian. Molecular clocks and biomarkers provide independent estimates for the timing of animal origins, and both suggest a cryptic Neoproterozoic history for Metazoa that extends considerably beyond the Cambrian fossil record. We report an assemblage of ichnofossils from Ediacaran-Cambrian siltstones in Brazil, alongside U-Pb radioisotopic dates that constrain the age of the oldest specimens to 555-542 Myr. X-ray microtomography reveals three-dimensionally preserved traces ranging from 50 to 600 μm in diameter, indicative of small-bodied, meiofaunal tracemakers. Burrow morphologies suggest they were created by a nematoid-like organism that used undulating locomotion to move through the sediment. This assemblage demonstrates animal-sediment interactions in the latest Ediacaran period, and provides the oldest known fossil evidence for meiofaunal bilaterians. Our discovery highlights meiofaunal ichnofossils as a hitherto unexplored window for tracking animal evolution in deep time, and reveals that both meiofaunal and macrofaunal bilaterians began to explore infaunal niches during the late Ediacaran.

  18. Rise to modern levels of ocean oxygenation coincided with the Cambrian radiation of animals.

    PubMed

    Chen, Xi; Ling, Hong-Fei; Vance, Derek; Shields-Zhou, Graham A; Zhu, Maoyan; Poulton, Simon W; Och, Lawrence M; Jiang, Shao-Yong; Li, Da; Cremonese, Lorenzo; Archer, Corey

    2015-05-18

    The early diversification of animals (∼ 630 Ma), and their development into both motile and macroscopic forms (∼ 575-565 Ma), has been linked to stepwise increases in the oxygenation of Earth's surface environment. However, establishing such a linkage between oxygen and evolution for the later Cambrian 'explosion' (540-520 Ma) of new, energy-sapping body plans and behaviours has proved more elusive. Here we present new molybdenum isotope data, which demonstrate that the areal extent of oxygenated bottom waters increased in step with the early Cambrian bioradiation of animals and eukaryotic phytoplankton. Modern-like oxygen levels characterized the ocean at ∼ 521 Ma for the first time in Earth history. This marks the first establishment of a key environmental factor in modern-like ecosystems, where animals benefit from, and also contribute to, the 'homeostasis' of marine redox conditions.

  19. Marine redox stratification during the early Cambrian (ca. 529-509 Ma) and its control on the development of organic-rich shales in Yangtze Platform

    NASA Astrophysics Data System (ADS)

    Zhang, Yuying; He, Zhiliang; Jiang, Shu; Gao, Bo; Liu, Zhongbao; Han, Bo; Wang, Hu

    2017-06-01

    High resolution geochemical data from nine sections representing shelf to basinal environments in the Yangtze Platform were analyzed to reconstruct the marine redox environment during early Cambrian. Based on Fe species and Mo/TOC ratios, we have supplemented marine redox stratification during Stage 4 (late Canglangpuian-Longwangmiaoan, ˜514-509 Ma) on basis of the previously studied Stage 2-Stage 3 (Meishucunian-Qiongzhusian, ˜529-514 Ma). A new proposed marine stratified redox model indicates that the middepth "euxinic wedge" developed at the base of slope during ˜514-509 Ma in contrast to that the "euxinic wedge" prevailed at the shelf margin during ˜529-514 Ma, even though these middepth euxinic waters both occurred between the oxic surface waters and ferruginous deep waters. This marine redox stratification resulted in high production and good preservation of organic matter during early Cambrian. TOC values in euxinic waters in the middle are generally higher than in ferruginous waters due to upwelling in slope. Therefore, the lower Cambrian organic-rich shales in the Yangtze Platform are inferred to be deposited under the anoxic-ferruginous and euxinic bottom waters with moderate-strong restriction.

  20. Rise to modern levels of ocean oxygenation coincided with the Cambrian radiation of animals

    PubMed Central

    Chen, Xi; Ling, Hong-Fei; Vance, Derek; Shields-Zhou, Graham A.; Zhu, Maoyan; Poulton, Simon W.; Och, Lawrence M.; Jiang, Shao-Yong; Li, Da; Cremonese, Lorenzo; Archer, Corey

    2015-01-01

    The early diversification of animals (∼630 Ma), and their development into both motile and macroscopic forms (∼575–565 Ma), has been linked to stepwise increases in the oxygenation of Earth's surface environment. However, establishing such a linkage between oxygen and evolution for the later Cambrian ‘explosion' (540–520 Ma) of new, energy-sapping body plans and behaviours has proved more elusive. Here we present new molybdenum isotope data, which demonstrate that the areal extent of oxygenated bottom waters increased in step with the early Cambrian bioradiation of animals and eukaryotic phytoplankton. Modern-like oxygen levels characterized the ocean at ∼521 Ma for the first time in Earth history. This marks the first establishment of a key environmental factor in modern-like ecosystems, where animals benefit from, and also contribute to, the ‘homeostasis' of marine redox conditions. PMID:25980960

  1. Arthropod eyes: The early Cambrian fossil record and divergent evolution of visual systems.

    PubMed

    Strausfeld, Nicholas J; Ma, Xiaoya; Edgecombe, Gregory D; Fortey, Richard A; Land, Michael F; Liu, Yu; Cong, Peiyun; Hou, Xianguang

    2016-03-01

    Four types of eyes serve the visual neuropils of extant arthropods: compound retinas composed of adjacent facets; a visual surface populated by spaced eyelets; a smooth transparent cuticle providing inwardly directed lens cylinders; and single-lens eyes. The first type is a characteristic of pancrustaceans, the eyes of which comprise lenses arranged as hexagonal or rectilinear arrays, each lens crowning 8-9 photoreceptor neurons. Except for Scutigeromorpha, the second type typifies Myriapoda whose relatively large eyelets surmount numerous photoreceptive rhabdoms stacked together as tiers. Scutigeromorph eyes are facetted, each lens crowning some dozen photoreceptor neurons of a modified apposition-type eye. Extant chelicerate eyes are single-lensed except in xiphosurans, whose lateral eyes comprise a cuticle with a smooth outer surface and an inner one providing regular arrays of lens cylinders. This account discusses whether these disparate eye types speak for or against divergence from one ancestral eye type. Previous considerations of eye evolution, focusing on the eyes of trilobites and on facet proliferation in xiphosurans and myriapods, have proposed that the mode of development of eyes in those taxa is distinct from that of pancrustaceans and is the plesiomorphic condition from which facetted eyes have evolved. But the recent discovery of enormous regularly facetted compound eyes belonging to early Cambrian radiodontans suggests that high-resolution facetted eyes with superior optics may be the ground pattern organization for arthropods, predating the evolution of arthrodization and jointed post-protocerebral appendages. Here we provide evidence that compound eye organization in stem-group euarthropods of the Cambrian can be understood in terms of eye morphologies diverging from this ancestral radiodontan-type ground pattern. We show that in certain Cambrian groups apposition eyes relate to fixed or mobile eyestalks, whereas other groups reveal concomitant

  2. Transient deep-water oxygenation in the early Cambrian Nanhua Basin, South China

    NASA Astrophysics Data System (ADS)

    Cheng, Meng; Li, Chao; Zhou, Lian; Feng, LianJun; Algeo, Thomas J.; Zhang, FeiFei; Romaniello, Stephen; Jin, ChengSheng; Ling, HongFei; Jiang, ShaoYong

    2017-08-01

    Many late Neoproterozoic to early Cambrian fossils of multicellular eukaryotes, including those of benthic animals, are found preserved under anoxic and even euxinic bottom-water conditions, which is contradictory to the consensus that oxygen is essential to eukaryotes. To investigate this conundrum, we conducted an integrated study of iron speciation, redox-sensitive trace elements, and Mo isotopes (δ98Mo) on the black shale interval of the lower Cambrian Hetang Formation (∼535-521 Ma) at Lantian, South China, in which benthic sponge fossils are abundant in the lower member (LM) but absent in the upper member (UM). Iron speciation data point to uniformly anoxic-ferruginous conditions in the LM and euxinic conditions in the UM, whereas the trace-element and δ98Mo data show greater secular variation in redox conditions. The LM shows higher mean trace element concentrations (Mo: 108 ppm, U: 36 ppm, V: 791 ppm) and lower and more variable δ98Mo (+0.13 to +1.76‰) relative to the UM (Mo: 45 ppm, U: 18 ppm, V: 265 ppm, δ98Mo: +1.59 to +1.67‰), and ratios of redox-sensitive trace element concentrations to total organic carbon are significantly more variable and higher on average in the LM relative to the UM. The appearance of sponge fossils and lower δ98Mo values correlate strongly with gray (i.e., lighter-colored) layers in the LM. These patterns can best be interpreted as recording mainly euxinic conditions throughout deposition of the study units, with more intense background euxinia in the LM relative to the UM, but also with frequent transient oxygenation events in the LM that do not appear in the UM. The transient oxygenation events of the LM led to the initial colonization of the deep Nanhua Basin by sponges, and the termination of these events in the UM caused sponge faunas to disappear until a general rise in O2 levels later in the Cambrian permitted their return to deeper-water habitats. Our study also illustrates that multiple geochemical and

  3. The oceanic carbon cycle implicated in the d13Ccarb and the d13Corg variations from the terminal Ediacaran to the Early Cambrian

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Ueno, Y.; Komiya, T.; Shu, D.; Li, Y.; Yoshida, N.; Maruyama, S.

    2009-04-01

    The terminal Neoproterozoic and its transition into the Cambrian witnessed major evolutionary and geochemical changes (e.g. Knoll, 1994). Evolutionary features include extinction and subsequent radiation events (e.g. Brasier, 1994; Knoll, 1994; Knoll and Carroll, 1999; Shu 2008). Geochemical changes comprise secular variations of the global carbon cycle expressed as variations of the d13C isotope records. A representative d13C curve for inorganic carbon (d13Ccarb) across the Precambrian/Cambrian boundary (Pc/C boundary) shows the existence of large fluctuations (e.g. Kirschvink et al., 1991; Narbonne et al., 1994; Kaufman et al., 1995; Amthor et al., 2003; Maloof et al., 2005, Ishikawa et al., 2008). This indicates a significant change of the oceanic carbon cycle at that time. On the other hand, the d13C values for total organic carbon (d13Corg) have rarely been reported together with the d13Ccarb across the boundary. Therefore, the precise relation between the d13Ccarb and the d13Corg and the global carbon cycle at the Pc/C boundary are still ambiguous. This work presents a first high-resolution d13Corg chemostratigraphy of drill core samples across the Pc/C boundary in the Three Gorges area, South China. Based on the results, this work additionally proposes variations of the sizes of the oceanic carbon reservoirs by a calculation of the carbon cycle model at the Pc/C boundary. The Three Gorges section extends from the uppermost Ediacaran dolostone (Dengying Formation), through the lowermost Early Cambrian muddy limestone (Yanjiahe Formation) to the middle Early Cambrian calcareous black shale (Shuijingtuo Formation). The ^13Corg values exhibit relatively invariant values averaging at -31 permil. By comparison between the d13Ccarb and d13Corg, we recognize two different terms in this period. The first term from the Pc/C boundary to the early Nemakit-Daldynian (ND) is characterized by the decoupling of d13Corg and d13Ccarb, stable d13Corg and the significant

  4. Exceptionally preserved Cambrian loriciferans and the early animal invasion of the meiobenthos.

    PubMed

    Harvey, Thomas H P; Butterfield, Nicholas J

    2017-01-30

    Microscopic animals that live among and between sediment grains (meiobenthic metazoans) are key constituents of modern aquatic ecosystems, but are effectively absent from the fossil record. We describe an assemblage of microscopic fossil loriciferans (Ecdysozoa, Loricifera) from the late Cambrian Deadwood Formation of western Canada. The fossils share a characteristic head structure and minute adult body size (~300 μm) with modern loriciferans, indicating the early evolution and subsequent conservation of an obligate, permanently meiobenthic lifestyle. The unsuspected fossilization potential of such small animals in marine mudstones offers a new search image for the earliest ecdysozoans and other animals, although the anatomical complexity of loriciferans points to their evolutionary miniaturization from a larger-bodied ancestor. The invasion of animals into ecospace that was previously monopolized by protists will have contributed considerably to the revolutionary geobiological feedbacks of the Proterozoic/Phanerozoic transition.

  5. Palaeogeography of late Cambrian to early Ordovician sediments in the Amadeus Basin, central Australia

    NASA Astrophysics Data System (ADS)

    Gorter, John D.

    The depositional history of 6 sequences encompassing 18 parasequence of the Late Cambrian to Early Ordovician age in the Amadeus Basin is presented in a seried of generalized paleogeographic maps. As some of the parasequence sets are known to host large deposits of oil and gas, a thorough understanding of the potential reservoir-source rock combinations in the Amadeus Basin is essential for the discovery of further oil and gas reserves in this vast, under-explored basin. The best reservoir rocks in the Pacoota Sandstone are concentrated above the major sequence boundary between the Wallaby and Tempe Vale sequences on the Central Ridge. Poorer reservoirs occur within other sequences (e.g., parasequence set 3 and 13). Parasequence set 3 reservoirs, localized on the Central Ridge, are generally poor but owe their reservoir character to weathering at the pre-Tempe Vale sequence unconformity. Parasequence set 13 reservoirs are also concenterated along the Central Ridge, where small-scale shoaling clastic cycles are better developed. Basal Stairway Sandstone reservoirs in the Mereenie area on the Central Ridge are generally very poor, due to the cementation of the clean sandstone, but should improve to the southwest due to lesser burial-induced silicification. The source potential of the major Arenig organic-rich sediments is concentrated in the transitional zone between parasequence sets 15 and 16. East of West Waterhouse 1 well, these parasequence sets have been eroded and there is no remaining source potential. The transitional source-rich zone is better developed on the Central Ridge than in the Missionary Plain Trough. The Central Ridge is therefore of prime importance in the localization of both reservoir and source rocks in the Late Cambrian and Early Ordovician section of the Amadeus Basin.

  6. Precambrian Time - The Story of the Early Earth

    USGS Publications Warehouse

    Lindsey, D.A.

    2007-01-01

    The Precambrian is the least-understood part of Earth history, yet it is arguably the most important. Precambrian time spans almost nine-tenths of Earth history, from the formation of the Earth to the dawn of the Cambrian Period. It represents time so vast and long ago that it challenges all comprehension. The Precambrian is the time of big questions. How old is the Earth? How old are the oldest rocks and continents? What was the early Earth like? What was the early atmosphere like? When did life appear, and what did it look like? And, how do we know this? In recent years, remarkable progress has been made in understanding the early evolution of the Earth and life itself. Yet, the scientific story of the early Earth is still a work in progress, humankind's latest attempt to understand the planet. Like previous attempts, it too will change as we learn more about the Earth. Read on to discover what we know now, in the early 21st century.

  7. Paleo-environmental conditions of the Early Cambrian Niutitang Formation in the Fenggang area, the southwestern margin of the Yangtze Platform, southern China: Evidence from major elements, trace elements and other proxies

    NASA Astrophysics Data System (ADS)

    Li, Jin; Tang, Shuheng; Zhang, Songhang; Xi, Zhaodong; Yang, Ning; Yang, Guoqiao; Li, Lei; Li, Yanpeng

    2018-06-01

    The Precambrian/Cambrian transition was a key time in Earth history, especially for marine biological evolution and oceanic chemistry. The redox-stratification with oxic shallow water and anoxic (even euxinic) deeper water in the Early Cambrian Yangtze Sea, which gradually became completely oxygenated, has been suggested as a possible trigger for the "Cambrian explosion" of biological diversity. However, for some areas in northern Guizhou where the exploration and research are lacking, identifying this pattern of redox-stratification by paleo-environmental analysis from borehole data is still in need. Here, we report a remarkable variation range in trace elements (Mo, V, U, Ni, Th, Co, Sc, Zn and Cu), molar Corg:P ratios and pyrite morphology from 27 core samples from one new drill hole (XY1, located in the Fenggang area, northern Guizhou) on the Yangtze Platform, South China. High levels of Ba (from 3242 ppm to 33,800 ppm) and total organic carbon (TOC; from 4% to 9.36%) in 15 core samples in the Lower Member (LM) of the Niutitang Formation indicated elevated primary productivity in the study area. Redox change was recorded based on enrichment factors (EFs) for RSTEs (Mo, U, and V), redox proxies (V/(V + Ni), Ni/Co, V/Sc and Th/U), Corg:P ratios and particle size of framboidal pyrite. These signatures demonstrate that the LM was deposited under anoxic conditions with sulfidic episodes, whereas the Upper Member (UM) of the Niutitang Formation was deposited under suboxic/oxic conditions with intermittently anoxic episodes. Mo/TOC ratios (from 3.72 to 39.86, mean 18.76) suggest weak-moderate water mass restriction. Mo-U covariation patterns (strong but variable enrichment of Mo and U; MoEF ranging from 31.45 to 257.97; UEF ranging from 4.68 to 39.07) in the LM show alternation of particulate shuttling and redox conditions occurred in the Early Cambrian Yangtze Sea, whereas Mo-U covariation patterns (moderate Mo enrichment but depletion or non-enrichment of U; mean Mo

  8. Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western USA

    PubMed Central

    Kurkewicz, Richard; Shinogle, Heather; Kimmig, Julien; MacGabhann, Breandán Anraoi

    2017-01-01

    The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician Discophyllum Hall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to as another clade, the eldonids, which includes the enigmatic Eldonia Walcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio- or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process. PMID:28603667

  9. Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western USA.

    PubMed

    Lieberman, Bruce S; Kurkewicz, Richard; Shinogle, Heather; Kimmig, Julien; MacGabhann, Breandán Anraoi

    2017-01-01

    The morphology and affinities of newly discovered disc-shaped, soft-bodied fossils from the early Cambrian (Series 2: Stage 4, Dyeran) Carrara Formation are discussed. These specimens show some similarity to the Ordovician Discophyllum Hall, 1847; traditionally this taxon had been treated as a fossil porpitid. However, recently it has instead been referred to as another clade, the eldonids, which includes the enigmatic Eldonia Walcott, 1911 that was originally described from the Cambrian Burgess Shale. The status of various Proterozoic and Phanerozoic taxa previously referred to porpitids and eldonids is also briefly considered. To help ascertain that the specimens were not dubio- or pseudofossils, elemental mapping using energy dispersive X-ray spectroscopy (EDS) was conducted. This, in conjunction with the morphology of the specimens, indicated that the fossils were not hematite, iron sulfide, pyrolusite, or other abiologic mineral precipitates. Instead, their status as biologic structures and thus actual fossils is supported. Enrichment in the element carbon, and also possibly to some extent the elements magnesium and iron, seems to be playing some role in the preservation process.

  10. The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China)

    PubMed Central

    Chen, Feiyang; Hu, Shixue; Zhang, Zhifei

    2017-01-01

    The early Cambrian Guanshan biota of eastern Yunnan, China, contains exceptionally preserved animals and algae. Most diverse and abundant are the arthropods, of which there are at least 11 species of trilobites represented by numerous specimens. Many trilobite specimens show soft-body preservation via iron oxide pseudomorphs of pyrite replacement. Here we describe digestive structures from two species of trilobite, Palaeolenus lantenoisi and Redlichia mansuyi. Multiple specimens of both species contain the preserved remains of an expanded stomach region (a “crop”) under the glabella, a structure which has not been observed in trilobites this old, despite numerous examples of trilobite gut traces from other Cambrian Lagerstätten. In addition, at least one specimen of Palaeolenus lantenoisi shows the preservation of an unusual combination of digestive structures: a crop and paired digestive glands along the alimentary tract. This combination of digestive structures has also never been observed in trilobites this old, and is rare in general, with prior evidence of it from one juvenile trilobite specimen from the late Cambrian Orsten fauna of Sweden and possibly one adult trilobite specimen from the Early Ordovician Fezouata Lagerstätte. The variation in the fidelity of preservation of digestive structures within and across different Lagerstätten may be due to variation in the type, quality, and point of digestion of food among specimens in addition to differences in mode of preservation. The presence and combination of these digestive features in the Guanshan trilobites contradicts current models of how the trilobite digestive system was structured and evolved over time. Most notably, the crop is not a derived structure as previously proposed, although it is possible that the relative size of the crop increased over the evolutionary history of the clade. PMID:28934290

  11. The oldest known digestive system consisting of both paired digestive glands and a crop from exceptionally preserved trilobites of the Guanshan Biota (Early Cambrian, China).

    PubMed

    Hopkins, Melanie J; Chen, Feiyang; Hu, Shixue; Zhang, Zhifei

    2017-01-01

    The early Cambrian Guanshan biota of eastern Yunnan, China, contains exceptionally preserved animals and algae. Most diverse and abundant are the arthropods, of which there are at least 11 species of trilobites represented by numerous specimens. Many trilobite specimens show soft-body preservation via iron oxide pseudomorphs of pyrite replacement. Here we describe digestive structures from two species of trilobite, Palaeolenus lantenoisi and Redlichia mansuyi. Multiple specimens of both species contain the preserved remains of an expanded stomach region (a "crop") under the glabella, a structure which has not been observed in trilobites this old, despite numerous examples of trilobite gut traces from other Cambrian Lagerstätten. In addition, at least one specimen of Palaeolenus lantenoisi shows the preservation of an unusual combination of digestive structures: a crop and paired digestive glands along the alimentary tract. This combination of digestive structures has also never been observed in trilobites this old, and is rare in general, with prior evidence of it from one juvenile trilobite specimen from the late Cambrian Orsten fauna of Sweden and possibly one adult trilobite specimen from the Early Ordovician Fezouata Lagerstätte. The variation in the fidelity of preservation of digestive structures within and across different Lagerstätten may be due to variation in the type, quality, and point of digestion of food among specimens in addition to differences in mode of preservation. The presence and combination of these digestive features in the Guanshan trilobites contradicts current models of how the trilobite digestive system was structured and evolved over time. Most notably, the crop is not a derived structure as previously proposed, although it is possible that the relative size of the crop increased over the evolutionary history of the clade.

  12. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) 'The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia'.

    PubMed

    Briggs, Derek E G

    2015-04-19

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  13. The early Cambrian fossil embryo Pseudooides is a direct-developing cnidarian, not an early ecdysozoan.

    PubMed

    Duan, Baichuan; Dong, Xi-Ping; Porras, Luis; Vargas, Kelly; Cunningham, John A; Donoghue, Philip C J

    2017-12-20

    Early Cambrian Pseudooides prima has been described from embryonic and post-embryonic stages of development, exhibiting long germ-band development. There has been some debate about the pattern of segmentation, but this interpretation, as among the earliest records of ecdysozoans, has been generally accepted. Here, we show that the 'germ band' of P. prima embryos separates along its mid axis during development, with the transverse furrows between the 'somites' unfolding into the polar aperture of the ten-sided theca of Hexaconularia sichuanensis , conventionally interpreted as a scyphozoan cnidarian; co-occurring post-embryonic remains of ecdysozoans are unrelated. We recognize H. sichuanensis as a junior synonym of P. prima as a consequence of identifying these two form-taxa as distinct developmental stages of the same organism. Direct development in P. prima parallels the co-occuring olivooids Olivooides, and Quadrapyrgites and Bayesian phylogenetic analysis of a novel phenotype dataset indicates that, despite differences in their tetra-, penta- and pseudo-hexa-radial symmetry, these hexangulaconulariids comprise a clade of scyphozoan medusozoans, with Arthrochites and conulariids, that all exhibit direct development from embryo to thecate polyp. The affinity of hexangulaconulariids and olivooids to extant scyphozoan medusozoans indicates that the prevalence of tetraradial symmetry and indirect development are a vestige of a broader spectrum of body-plan symmetries and developmental modes that was manifest in their early Phanerozoic counterparts. © 2017 The Authors.

  14. The early Cambrian fossil embryo Pseudooides is a direct-developing cnidarian, not an early ecdysozoan

    PubMed Central

    2017-01-01

    Early Cambrian Pseudooides prima has been described from embryonic and post-embryonic stages of development, exhibiting long germ-band development. There has been some debate about the pattern of segmentation, but this interpretation, as among the earliest records of ecdysozoans, has been generally accepted. Here, we show that the ‘germ band’ of P. prima embryos separates along its mid axis during development, with the transverse furrows between the ‘somites’ unfolding into the polar aperture of the ten-sided theca of Hexaconularia sichuanensis, conventionally interpreted as a scyphozoan cnidarian; co-occurring post-embryonic remains of ecdysozoans are unrelated. We recognize H. sichuanensis as a junior synonym of P. prima as a consequence of identifying these two form-taxa as distinct developmental stages of the same organism. Direct development in P. prima parallels the co-occuring olivooids Olivooides, and Quadrapyrgites and Bayesian phylogenetic analysis of a novel phenotype dataset indicates that, despite differences in their tetra-, penta- and pseudo-hexa-radial symmetry, these hexangulaconulariids comprise a clade of scyphozoan medusozoans, with Arthrochites and conulariids, that all exhibit direct development from embryo to thecate polyp. The affinity of hexangulaconulariids and olivooids to extant scyphozoan medusozoans indicates that the prevalence of tetraradial symmetry and indirect development are a vestige of a broader spectrum of body-plan symmetries and developmental modes that was manifest in their early Phanerozoic counterparts. PMID:29237861

  15. New uppermost Cambrian U-Pb date from Avalonian Wales and age of the Cambrian-Ordovician boundary

    USGS Publications Warehouse

    Davidek, K.; Landing, E.; Bowring, S.A.; Westrop, S.R.; Rushton, A.W.A.; Fortey, R.A.; Adrain, J.M.

    1998-01-01

    A crystal-rich volcaniclastic sandatone in the lower Peltura scarabaeoides Zone at Ogof-odi near Criccieth, North Wales, yields a U-Pb zircon age of 491 ?? 1 Ma. This late Late Cambrian date indicates a remarkably young age for the Cambrian-Ordovician boundary whose age must be less than 491 Ma. Hence the revised duration of the post-Placentian (trilobite-bearing) Cambrian indicates that local trilobite zonations allow a biostratigraphic resolution comparble to that provided by Ordovician graptolites and Mesozoic ammonites.

  16. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia’

    PubMed Central

    Briggs, Derek E. G.

    2015-01-01

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750235

  17. Preservation of Early Cambrian animals of the Chengjiang biota

    NASA Astrophysics Data System (ADS)

    Gabbott, Sarah E.; Xian-Guang, Hou; Norry, Michael J.; Siveter, David J.

    2004-10-01

    The Chengjiang biota of Yunnan, China, documents the earliest extensive radiation of the Metazoa recorded in the fossil record. Gauging preservational bias is crucial in providing an assessment of the completeness of this biota and thereby elucidating whether it represents a comprehensive depiction of Early Cambrian life. We here present a model to explain the nature of the exceptional preservation of the Chengjiang biota and details of the decay process. This study indicates that Chengjiang fossils were preserved through two taphonomic pathways that may have captured tissues of distinct compositions, and this finding should provide a foundation for the interpretation of Chengjiang fossils. Many Chengjiang fossils are preserved by pyrite (later pseudomorphed by iron oxides); the clay-rich host sediment was deficient in organic carbon but replete in available Fe, and this composition ensured that a decaying carcass acted as a local substrate for Fe- and S-reducing bacteria. Pyrite morphology probably reflects contrasts in the decay rate, and hence the H2S production rate, of different tissues in a carcass. Reactive, rapidly decaying tissues would have quickly supplied H2S, producing many pyrite nuclei, resulting in framboidal habits. More recalcitrant tissues would have produced H2S more slowly, so that crystal growth operated on fewer nuclei, resulting in larger euhedral pyrite crystals. Reflective films, especially common on Chengjiang arthropods, represent the remains of degraded carbon.

  18. Trace fossils and substrates of the terminal Proterozoic–Cambrian transition: Implications for the record of early bilaterians and sediment mixing

    PubMed Central

    Droser, Mary L.; Jensen, Sören; Gehling, James G.

    2002-01-01

    The trace fossil record is important in determining the timing of the appearance of bilaterian animals. A conservative estimate puts this time at ≈555 million years ago. The preservational potential of traces made close to the sediment–water interface is crucial to detecting early benthic activity. Our studies on earliest Cambrian sediments suggest that shallow tiers were preserved to a greater extent than typical for most of the Phanerozoic, which can be attributed both directly and indirectly to the low levels of sediment mixing. The low levels of sediment mixing meant that thin event beds were preserved. The shallow depth of sediment mixing also meant that muddy sediments were firm close to the sediment–water interface, increasing the likelihood of recording shallow-tier trace fossils in muddy sediments. Overall, trace fossils can provide a sound record of the onset of bilaterian benthic activity. PMID:12271130

  19. Latest Cambrian-Early Ordovician rift-related magmatic activity in the Kouřim Unit, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Soejono, Igor; Machek, Matej; Sláma, Jiří; Janoušek, Vojtěch

    2017-04-01

    inherited from the source, represented most likely by recycled immature arc-related material (?metagraywackes). The real tectonic setting of this Late Cambrian magmatic activity seems rather indicated by the within-plate geochemistry of the metadiorite. These results bring further evidence for the presence of the Late Cambrian-Early Ordovician extensional event documented throughout the basement of the European Variscan Belt. Together with other occurrences of bimodal magmatism, as well as metamorphic and sedimentary record, indicate an important period of lithospheric thinning. This overall Early Palaeozoic rift-related architecture is often considered as a consequence of the Rheic Ocean opening.

  20. Diversity partitioning during the Cambrian radiation

    PubMed Central

    Na, Lin; Kiessling, Wolfgang

    2015-01-01

    The fossil record offers unique insights into the environmental and geographic partitioning of biodiversity during global diversifications. We explored biodiversity patterns during the Cambrian radiation, the most dramatic radiation in Earth history. We assessed how the overall increase in global diversity was partitioned between within-community (alpha) and between-community (beta) components and how beta diversity was partitioned among environments and geographic regions. Changes in gamma diversity in the Cambrian were chiefly driven by changes in beta diversity. The combined trajectories of alpha and beta diversity during the initial diversification suggest low competition and high predation within communities. Beta diversity has similar trajectories both among environments and geographic regions, but turnover between adjacent paleocontinents was probably the main driver of diversification. Our study elucidates that global biodiversity during the Cambrian radiation was driven by niche contraction at local scales and vicariance at continental scales. The latter supports previous arguments for the importance of plate tectonics in the Cambrian radiation, namely the breakup of Pannotia. PMID:25825755

  1. Late Precambrian-Cambrian sediments of Huqf group, Sultanate of Oman

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gorin, G.E.; Racz, L.G.; Walter, M.R.

    1982-12-01

    The Huqf Group is the oldest known sedimentary sequence overlying crystalline basement in the Sultanate of Oman. It crops out on a broad regional high, the Huqf Axis, which forms a dominating structural element on the southeastern edge of the Arabian peninsula. Subsurface and outcrop evidence within and outside of Oman suggests that the sediments of the Huqf Group lie within the age span of late Precambrian to Early-Middle Cambrian. The Huqf Group is subdivided into five formations corresponding to an alternation of clastics (Abu Mahara and Shuram Formations) and carbonates (Khufai and Buah Formations) deposited in essentially shallow marinemore » to supratidal (or fluviatile) conditions and terminated by an evaporitic sequence (Ara Formation). Evaporites are absent on the Huqf Axis, but they are thickly developed to the west over a large part of southern and central Oman, where they acted as the major structure former of most of Oman's fields, and even locally pierced up to the surface. Regional correlations suggest that the predominantly carbonate-evaporitic facies of the Huqf Group was widely distributed in late Precambrian-Early Cambrian time: the Huqf basin is tentatively considered part of a belt of evaporitic basins and intervening carbonate platforms, which stretched across the Pangea landmass from the Indian subcontinent (Salt Range of Pakistan) through South Yemen, Oman, and Saudi Arabia into the gulf states and Iran (Hormuz Series and carbonate platform north of the Zagros).« less

  2. Ichnologic evidence of a Cambrian age in the southern Amazon Craton: Implications for the onset of the Western Gondwana history

    NASA Astrophysics Data System (ADS)

    Santos, Hudson P.; Mángano, M. Gabriela; Soares, Joelson L.; Nogueira, Afonso C. R.; Bandeira, José; Rudnitzki, Isaac D.

    2017-07-01

    Colonization of the infaunal ecospace by burrowing bilaterians is one of the most important behavioral innovations during the Ediacaran-Cambrian transition. The establishment of vertical burrows by suspension feeders in high-energy nearshore settings during Cambrian Age 2 is reflected by the appearance of the Skolithos Ichnofacies. For the first time, unquestionable vertical burrows typical of the Skolithos Ichnofacies, such as Skolithos linearis, Diplocraterion parallelum and Arenicolites isp., are recorded from nearshore siliciclastic deposits of the Raizama Formation, southeastern Amazon Craton, Brazil. Integration of ichnologic and sedimentologic datasets suggests that these trace fossils record colonization of high-energy and well-oxygenated nearshore sandy environments. Chronostratigraphically, the presence of these vertical burrows indicates an age not older than early Cambrian for the Raizama Formation, which traditionally has been regarded as Ediacaran. Therefore, the Raizama ichnofauna illustrates the advent of modern Phanerozoic ecology marked by the Agronomic Revolution. The discovery of the Skolithos Ichnofacies in these shallow-marine strata suggests possible connections between some central Western Gondwana basins.

  3. Multiple Controls on the Paleoenvironment of the Early Cambrian Marine Black Shales in the Sichuan Basin, SW China: Geochemical and Organic Carbon Isotopic Evidence

    NASA Astrophysics Data System (ADS)

    Wang, S.; Zhang, G.; Dong, D.; Wang, Y.

    2016-12-01

    In order to understand the paleoenvironment of the Early Cambrian black shale deposition in the western part of the Yangtze Block, geochemical and organic carbon isotopic studies have been performed on two wells that have drilled through the Qiongzhusi Formation in the central and southeastern parts of Sichuan Basin. It shows that the lowest part of the Qiongzhusi Formation has high TOC abundance, while the middle and upper parts display relative low TOC content. Redox-sensitive element (Mo) and trace elemental redox indices (e.g., Ni/Co, V/Cr, U/Th and V/(V+Ni)) suggest that the high-TOC layers were deposited under anoxic conditions, whereas the low-TOC layers under relatively dysoxic/oxic conditions. The relationship of the enrichment factors of Mo and U further shows a transition from suboxic low-TOC layers to euxinic high-TOC layers. On the basis of the Mo-TOC relationship, the Qiongzhusi Formation black shales were deposited in a basin under moderately restricted conditions. Organic carbon isotopes display temporal variations in the Qiongzhusi Formation, with a positive excursion of δ13Corg values in the lower part and a continuous positive shift in the middle and upper parts. All these geochemical and isotopic criteria indicate a paleoenvironmental change from bottom anoxic to middle and upper dysoxic/oxic conditions for the Qiongzhusi Formation black shales. The correlation of organic carbon isotopic data for the Lower Cambrian black shales in different regions of the Yangtze Block shows consistent positive excursion of δ13Corg values in the lower part for each section. This excursion can be ascribed to the widespread Early Cambrian transgression in the Yangtze Block, under which black shales were deposited.

  4. Reconstruction of the Paleoenvironment of the Early Cambrian Yurtus Black Shale in the Tarim Basin, Northwestern China, and Its Control on Organic Matter Accumulation

    NASA Astrophysics Data System (ADS)

    Li, J.; Ding, W.; Dong, L.

    2017-12-01

    The black shale in the early Cambrian Yurtus Formation (>521 Ma) in the Tarim basin, northwestern China, is characterized by its high TOC value (up to 16%) andgreat lateral continuity. It has been proven to be high-quality hydrocarbon source rocks. Abundant phytoplanktons and small shelly fossils have been reported from the lower Yurtus chert. However, recent biomarker discovery of aryl isoprenoid hydrocarbons suggests the existence of green sulfur bacteria, which indicates that the water column was stratified and the photic zone was prevailingly euxinic. These seemingly contradictory observations hamper our further understanding of the paleoenvironment in which the Yurtus shale was deposited and its control on the accumulation of organic matter. In this study, we systematically collected samples from the Yurtus Formation at the Kungaikuotan Section, and measured the organic carbon and nitrogen isotopic compositions and the content of trace element Barium (Ba). The strong negative excursions of nitrogen isotope ( -13‰) in the lower and upper parts of the Yurtus Formation are likely attributed to the biological activity of green and purple sulfur bacteria, which is consistent with our organic carbon isotope data as well as previous biomarker discovery. As green sulfur bacteria can only live in euxinic photic zone, it may indicate that the water column above this euxinic zone contains prolific organic matters which consume all the dissolved oxidants in surface ocean. It is well accepted that Ba flux can be used as an indicator for surface ocean primary productivity. Significant increase of barium content (from <100 to 2000 ppm) is observed at the same horizon as where the negative excursion of δ15Norg occurs, suggesting the substantive organic matter in the early Cambrian surface ocean mainly result from extremely high primary productivity. The abundant phytoplankton fossil record from this time period also supports this interpretation. In summary, high TOC in the

  5. The origin of decoupled carbonate and organic carbon isotope signatures in the early Cambrian (ca. 542-520 Ma) Yangtze platform

    NASA Astrophysics Data System (ADS)

    Jiang, Ganqing; Wang, Xinqiang; Shi, Xiaoying; Xiao, Shuhai; Zhang, Shihong; Dong, Jin

    2012-02-01

    The early Cambrian (ca. 542-520 Ma) strata in South China record two prominent negative carbonate carbon isotope (δ13Ccarb) excursions of early Nemakit-Daldynian (N-D) and early Tommotian ages. Across each of these excursions, carbonate and organic carbon isotopes (δ13Ccarb and δ13Corg) are strongly decoupled. Regional correlation across a shelf-to-basin transect shows lateral heterogeneity of δ13Corg during the early-middle N-D but more homogenized δ13Corg values across the basin during the late N-D and Tommotian. The temporal and lateral variations in δ13Corg suggest that decoupled δ13Ccarb and δ13Corg across the N-D δ13Ccarb excursion were possibly caused by diagenetic alteration of organic matter and/or amplification of detrital organic carbon isotope signature in low-TOC carbonates. In contrast, decoupled δ13Ccarb and δ13Corg of the upper N-D and Tommotian were likely resulted from chemoautotrophic-methanotrophic biomass contribution to TOC in organic-rich black shale and carbonates. The decoupled δ13Ccarb-δ13Corg pattern from the lower N-D strata (ca. 542 Ma) shows striking similarities with those from the basal (ca. 635 Ma) and upper (ca. 551 Ma) Doushantuo Formation. In all three cases, decoupled δ13Ccarb-δ13Corg are seen in organic-poor carbonates (TOC ≤ 0.1‰) and coupled δ13Ccarb-δ13Corg occur in organic-rich black shale and carbonates at the end of the negative δ13Ccarb excursion. These similarities suggest that the shift from decoupled to coupled δ13Ccarb-δ13Corg has no causal link with the terminal oxidation of a large oceanic DOC reservoir. Given the pervasive anoxia/euxinia in Ediacaran-early Cambrian oceans, local DOC-rich environments may have been common, but a large oceanic DOC reservoir capable of buffering the δ13C of marine organic matter requires independent evidence.

  6. Gas potential of the Rome Trough in Kentucky: Results of recent Cambrian exploration

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harris, D.C.; Drahovzal, J.A.

    1996-09-01

    A recent gas discovery in the Rome Trough suggests the need to re-evaluate the deep Cambrian potential of eastern Kentucky. A new phase of Cambrian exploration began in mid-1994 with a new pool discovery by the Carson Associates No. 1 Kazee well in Elliott County, Ky. This well blew out and initially flowed 11 MMcfd of gas from the upper Conasauga Group/Rome Formation at 6,258 to 6,270 feet. After this discovery, a second exploratory well (the Blue Ridge No. 1Greene) was drilled on a separate structure in Elliott County in late 1995. The Blue Ridge well was temporarily abandoned, butmore » had shows of gas and condensate. In early 1996, Carson Associates offset their initial discovery well with the No. 33 Lawson Heirs well. This activity follows a frustrating exploration history in the Rome Trough that is marked by numerous gas and oil shows, but rare commercial production. Only three single-well pools have produced commercial gas from the trough, including the recent Kazee well. Stratigraphic units below the Cambrian-Ordovician Knox Group in the Rome Trough are dramatically thicker than their equivalents on the shelf to the north. The interval in the trough is thought to include rocks as old as Early Cambrian, consisting of a basal sandstone, equivalents of the Shady/Tomstown Dolomite, the Rome Formation, and the Conasauga Formation. Sandstones and fractured shales have been responsible for most of the production to date, but dolostone intervals may also have potential. Limited seismic data indicate possible fan-delta and basin-floor fan deposits that may have reservoir potential.« less

  7. Minerals in the gut: scoping a Cambrian digestive system

    NASA Astrophysics Data System (ADS)

    Strang, K. M.; Armstrong, H. A.; Harper, D. A. T.

    2016-11-01

    The Sirius Passet Lagerstätte of North Greenland contains the first exceptionally preserved mat-ground community of the Cambrian, dominated, in terms of abundance, by trilobites but particularly characterized by iconic arthropods and lobopods, some also occurring in the Burgess shale. High-resolution photography, scanning electron imaging and elemental mapping have been carried out on a variety of specimens of the non-mineralized arthropod Campanamuta mantonae (Budd 2011 J. Syst. Palaeontol. 9, 217-260 (doi:10.1080/14772019.2010.492644)) which has three-dimensional gut and muscle preservation. Results show that the guts contain a high concentration of calcium phosphate (approximating to the mineral francolite), whereas the adjacent muscles are silicified. This indicates a unique, tissue-specific taphonomy for this Cambrian taxon. We hypothesize that the precipitation of calcium phosphate in the guts occurs rapidly after death by `crystal seed' processes in suboxic, slightly acidic conditions; critically, the gut wall remained intact during precipitation. We postulate that the calcium phosphate was derived from ingested cellular material. Silicification of the muscles followed as the localized water chemistry became saturated in silica, high in Fe2+, and low in oxygen and sulfate. We document here the unique occurrence of two distinct but mechanistically similar taphonomic pathways within a diverse suite of possibilities in an Early Cambrian Lagerstätte.

  8. A Cambrian mixed carbonate-siliciclastic platform in SW Gondwana: evidence from the Western Sierras Pampeanas (Argentina) and implications for the early Paleozoic paleogeography of the proto-Andean margin

    NASA Astrophysics Data System (ADS)

    Ramacciotti, Carlos D.; Casquet, César; Baldo, Edgardo G.; Galindo, Carmen; Pankhurst, Robert J.; Verdecchia, Sebastián O.; Rapela, Carlos W.; Fanning, Mark

    2018-05-01

    The Western Sierras Pampeanas (WSP) of Argentina record a protracted geological history from the Mesoproterozoic assembly of the Rodinia supercontinent to the early Paleozoic tectonic evolution of SW Gondwana. Two well-known orogenies took place at the proto-Andean margin of Gondwana in the Cambrian and the Ordovician, i.e., the Pampean (545-520 Ma) and Famatinian (490-440 Ma) orogenies, respectively. Between them, an extensive continental platform was developed, where mixed carbonate-siliciclastic sedimentation occurred. This platform was later involved in the Famatinian orogeny when it underwent penetrative deformation and metamorphism. The platform apparently extended from Patagonia to northwestern Argentina and the Eastern Sierras Pampeanas, and has probable equivalents in SW Africa, Peru, and Bolivia. The WSP record the outer (deepest) part of the platform, where carbonates were deposited in addition to siliciclastic sediments. Detrital zircon U-Pb SHRIMP ages from clastic metasedimentary successions and Sr-isotope compositions of marbles from the WSP suggest depositional ages between ca. 525 and 490 Ma. The detrital zircon age patterns further suggest that clastic sedimentation took place in two stages. The first was sourced mainly from re-working of the underlying Neoproterozoic metasedimentary rocks and the uplifted core of the early Cambrian Pampean orogen, without input from the Paleoproterozoic Río de la Plata craton. Sediments of the second stage resulted from the erosion of the still emerged Pampean belt and the Neoproterozoic Brasiliano orogen in the NE with some contribution from the Río de la Plata craton. An important conclusion is that the WSP basement was already part of SW Gondwana in the early Cambrian, and not part of the exotic Precordillera/Cuyania terrane, as was previously thought.

  9. Relationship between the Neoproterozoic snowball Earth and Cambrian explosion

    NASA Astrophysics Data System (ADS)

    Maruyama, S.; Yoshihara, A.; Isozaki, Y.

    2007-12-01

    Origin of snowball Earth has been debated in terms of greenhouse gas (e.g., Hoffman and Schrag), obliqueness of Earth's rotation axis (Williams, 1975), true polar wander (Evans, 2003), Galactic cosmic ray radiation (Shaviv and Veizer, 2003; Svensmark, 2006), or weakened geomagnetism (Maruyama and Yoshihara, 2003). A major difficulty for the greenhouse gas hypothesis is the on-off switch causing decrease and increase of appropriate amounts of CO2 by plume- and plate tectonics, and also in available amount of CO2 in atmosphere to be consistent with the observations. In contrast, the cosmic ray radiation models due to the star burst peaked at 2.5- 2.1 Ga and 1.4-0.8 Ga can explain on-off switch more easily than the greenhouse gas model. Cosmic ray radiations, however, must be modified by the geomagnetic intensity, fluctuating 150"% to < 10"% of the present-day level through geologic time. Our compilation suggests the idea of extensive glaciation appeared when the intensity decreased below 50% of the present-day value, as typically seen in the Neoproterozoic time. This proposes the idea of extensive cloudiness by increased cosmic rays in the Neoproterozoic to cause the snowball Earth. Time difference between the Neoproterozoic snowball Earth and Cambrian explosion is as large as 250 millions years, and this refuses their direct close-relationship. Role of frequent mass extinctions, i.e., 8 times during 100 m.y. from 585 Ma to 488 Ma, during the Ediacaran and Cambrian, has been proposed (Zhu et al., 2007). This frequency is one order of magnitude higher compared to that in the post-Ordovician time. Yet, the Cambrian explosion cannot be explained by mass extinction which replaced the vacant niches shortly after the mass extinction and never created a new animal with a new body plan. A new model proposed herein is derived from weakened geomagnetism and resultant extensive cosmic radiation to alter gene and genome for a long period over advancement of low magnetic

  10. 3D-Mapping of Dolomitized Structures in Lower Cambrian Phosphorites

    NASA Astrophysics Data System (ADS)

    Hippler, Dorothee; Stammeier, Jessica A.; Brunner, Roland; Rosc, Jördis; Franz, Gerhard; Dietzel, Martin

    2016-04-01

    Dolomitization is a widespread phenomenon in ancient sedimentary rocks, particularly close to the Precambrian-Cambrian boundary. Dolomite can form in synsedimentary or hydrothermal environments, preferentially via the replacement of solid carbonate precursor phases. Synsedimentary dolomite formation is often associated with microbial activity, such as bacterial sulfate reduction or methanogenesis. In this study, we investigate dolomitic phosphorites from the Lowermost Cambrian Tal Group, Mussoori Syncline, Lesser Himalaya, India, using micro-CT 3D-mapping, in order to unravel the complex diagenetic history of the rocks. The selected sample shows alternating layering of phosphatic mudstones and sparitic dolostone, in which brecciated layers of phosphorite or phosphatic mudstones are immersed in a dolomite-rich matrix. Lamination occurs on a sub-millimetre scale, with lamination sometimes wavy to crinkly. This fabric is interpreted as former microbial mats, providing the environment for early diagenetic phosphatization. Preliminary electron backscatter imaging with scanning microscopy revealed that dolomite crystals often occur in spherical to ellipsoidal structures, typically with a high porosity. This dolomite is associated with botryoidal apatite, organic matter and small amounts of calcite. Micro-CT 3D-mappings reveal that dolomite structures are cigar-shaped, elongated and up to 600 μm long. They are further arranged in a Mikado-like oriented framework spanning a layer thickness of a few millimetres. Analyses of ambient pore space, with similar elongated outlines and filled with organic matter, suggest a potential coherence of ambient pore space and shape of the dolomite structures. Allowing for other associated mineral phases, such as pyrite and silicates, and their spatial distribution, the present approach can be used to unravel distinct diagenetic reaction pathways, and might thus constrain the proxy potential of these Lower Cambrian dolomitic phosphorites

  11. Oxygen, ecology, and the Cambrian radiation of animals

    PubMed Central

    Sperling, Erik A.; Frieder, Christina A.; Raman, Akkur V.; Girguis, Peter R.; Levin, Lisa A.; Knoll, Andrew H.

    2013-01-01

    The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator–prey “arms races” can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an analog for Proterozoic oceans, we explore the effect of low oxygen levels on the feeding ecology of polychaetes, the dominant macrofaunal animals in deep-sea sediments. Here we show that low oxygen is clearly linked to low proportions of carnivores in a community and low diversity of carnivorous taxa, whereas higher oxygen levels support more complex food webs. The recognition of a physiological control on carnivory therefore links environmental triggers and ecological drivers, providing an integrated explanation for both the pattern and timing of Cambrian animal radiation. PMID:23898193

  12. Oxygen, ecology, and the Cambrian radiation of animals

    NASA Astrophysics Data System (ADS)

    Sperling, Erik A.; Frieder, Christina A.; Raman, Akkur V.; Girguis, Peter R.; Levin, Lisa A.; Knoll, Andrew H.

    2013-08-01

    The Proterozoic-Cambrian transition records the appearance of essentially all animal body plans (phyla), yet to date no single hypothesis adequately explains both the timing of the event and the evident increase in diversity and disparity. Ecological triggers focused on escalatory predator-prey "arms races" can explain the evolutionary pattern but not its timing, whereas environmental triggers, particularly ocean/atmosphere oxygenation, do the reverse. Using modern oxygen minimum zones as an analog for Proterozoic oceans, we explore the effect of low oxygen levels on the feeding ecology of polychaetes, the dominant macrofaunal animals in deep-sea sediments. Here we show that low oxygen is clearly linked to low proportions of carnivores in a community and low diversity of carnivorous taxa, whereas higher oxygen levels support more complex food webs. The recognition of a physiological control on carnivory therefore links environmental triggers and ecological drivers, providing an integrated explanation for both the pattern and timing of Cambrian animal radiation.

  13. Recognition of Macluritella ( Gastropoda) from the Upper Cambrian of Missouri and Nevada ( USA).

    USGS Publications Warehouse

    Yochelson, E.L.; Stinchcomb, B.L.

    1987-01-01

    Open-coiled euomphalacean gastropods have been identified for the first time in the Upper Cambrian Eminence Dolomite of Missouri. These gastropods have a triangular whorl profile and are conspecific with Hyolithes walcotti described from the Upper Cambrian of Nevada. That species is questionably reassigned to the gastropod genus Macluritella, hitherto known only from the Lower Ordovician of Colorado. -Authors Ordovician Colorado

  14. Depositional Architecture of Late Cambrian-Early Ordovician Siliciclastic Barik Formation; Al Huqf Area, Oman

    NASA Astrophysics Data System (ADS)

    Abbasi, Iftikhar Ahmed

    2017-04-01

    Early Paleozoic siliciclastics sediments of the Haima Supergroup are subdivided into a number of formations and members based on lithological characteristics of various rock sequences. One of the distinct sandstone sequence, the Barik Formation (Late Cambrian-Early Ordovician) of the Andam Group is a major deep gas reservoir in central Oman. The sandstone bodies are prospective reservoir rocks while thick shale and clay interbeds act as effective seal. Part of the Barik Formation (lower and middle part) is exposed in isolated outcrops in Al Huqf area as interbedded multistoried sandstone, and green and red shale. The sandstone bodies are up to 2 meters thick and can be traced laterally for 300 m to over 1 km. Most of sandstone bodies show both lateral and vertical stacking. Two types of sandstone lithofacies are identified on the basis of field characteristics; a plane-bedded sandstone lithofacies capping thick red and green color shale beds, and a cross-bedded sandstone lithofacies overlying the plane-bedded sandstone defining coarsening upward sequences. The plane-bedded sandstone at places contains Cruziana ichnofacies and bivalve fragments indicating deposition by shoreface processes. Thick cross-bedded sandstone is interpreted to be deposited by the fluvial dominated deltaic processes. Load-casts, climbing ripples and flaser-bedding in siltstone and red shale indicate influence of tidal processes at times during the deposition of the formation. This paper summarizes results of a study carried out in Al Huqf area outcrops to analyze the characteristics of the sandstone-body geometry, internal architecture, provenance and diagenetic changes in the lower and middle part of the formation. The study shows build-up of a delta complex and its progradation over a broad, low-angle shelf where fluvial processes operate beside shoreface processes in a vegetation free setting. Keywords: Andam Group, Barik Formation, Ordovician sandstone, Al Huqf, Central Oman,

  15. Cambrian stem-group annelids and a metameric origin of the annelid head.

    PubMed

    Parry, Luke; Vinther, Jakob; Edgecombe, Gregory D

    2015-10-01

    The oldest fossil annelids come from the Early Cambrian Sirius Passet and Guanshan biotas and Middle Cambrian Burgess Shale. While these are among the best preserved polychaete fossils, their relationship to living taxa is contentious, having been interpreted either as members of extant clades or as a grade outside the crown group. New morphological observations from five Cambrian species include the oldest polychaete with head appendages, a new specimen of Pygocirrus from Sirius Passet, and an undescribed form from the Burgess Shale. We propose that the palps of Canadia are on an anterior segment bearing neuropodia and that the head of Phragmochaeta is formed of a segment bearing biramous parapodia and chaetae. The unusual anatomy of these taxa suggests that the head is not differentiated into a prostomium and peristomium, that palps are derived from a modified parapodium and that the annelid head was originally a parapodium-bearing segment. Canadia, Phragmochaeta and the Marble Canyon annelid share the presence of protective notochaetae, interpreted as a primitive character state subsequently lost in Pygocirrus and Burgessochaeta, in which the head is clearly differentiated from the trunk. © 2015 The Authors.

  16. Upper Lower Cambrian depositional sequence in Avalonian New Brunswick

    USGS Publications Warehouse

    Landing, E.; Westrop, S.R.

    1996-01-01

    The Hanford Brook Formation (emended) is a thin (up to 42+ m), upper Lower Cambrian depositional sequence that is unconformably bounded by the lower Lower Cambrian (Random Formation) and the middle Middle Cambrian (Fossil Brook Member of the Chamberlain's Brook Formation). These stratigraphic relationships of the trilobite-bearing Hanford Brook Formation indicate deposition on the Avalonian marginal platform in the Saint John, New Brunswick, region and provide more evidence for a uniform, latest Precambrian-Cambrian epeirogenic history and cover sequence in Avalon. The Hanford Brook Formation is a deepening - shoaling sequence with (i) lower, transgressive sandstone deposited in episodically high-energy environments (St. Martins Member, new); (ii) highstand-regressive, dysaerobic mudstone - fine-grained sandstone with volcanic ashes (Somerset Street Member, new); and (iii) upper, regressive, planar and hummocky cross-stratified sandstone (Long Island Member, new). Trilobites are common in the distal Somerset Street Member, and ostracodes and brachiopods dominate the St. Martins and Long Island members. Condensation of the St. Martins Member and absence of the Long Island Member where the Random Formation and Fossil Brook Member are thinnest suggest onlap of the Hanford Brook and pronounced, sub-Middle Cambrian erosion across epeirogenically active blocks in southern New Brunswick.

  17. Antarctica, supercontinents and the palaeogeography of the Cambrian 'explosion'

    NASA Astrophysics Data System (ADS)

    Dalziel, Ian

    2014-05-01

    Laurentia is bordered by latest Precambrian-Cambrian rifted margins and must therefore have been located within a Precambrian supercontinent. Geochronologic and geochemical evidence indicates that it was attached to parts of the East Antarctic craton within the Rodinian supercontinent in the late Mesoproterozoic. The Mawson craton of Antarctica rifted from the proto-Pacific margin of Laurentia during the Neooproterozoic, colliding with the present 'southern cone' of Laurentia at ~600 Ma along the Shackleton Range suture zone as Gondwana and Laurentia amalgamated to form the ephemeral Pannotia supercontinental assembly at the end of the Precambrian. The abrupt appearance of almost all animal phyla in the fossil record is often colloquially referred to as the Cambrian 'explosion' of life on Earth. It is also named 'Darwin's dilemma,' as he appreciated that this seemingly mysterious event posed a major problem for his theory of evolution by natural selection. It coincided with a time of major marine transgression over all the continents. Although the metazoan 'explosion' is now seen as more protracted than formerly recognized, it is still regarded one of the most critical events in the history of the biosphere. One of the most striking aspects of the earliest Cambrian fossils is geographic differentiation. In particular, the first benthic trilobite faunas on Laurentia, ancestral North America, and the newly amalgamated southern supercontinent of Gondwana are distinctly different. This has led to the suggestion of an unknown vicariant event intervening between an ancestral trilobite clade and higher members that are represented in the fossil record, possibly one related to the breakup of a supercontinent. Igneous rocks along the Panthalassic margin of Gondwana, including South America, southernmost Africa and the Ellsworth-Whitmore crustal block of Antarctica, and along the proto-Appalachian margin of Laurentia indicate that final separation of Laurentia from

  18. Gut Contents as Direct Indicators for Trophic Relationships in the Cambrian Marine Ecosystem

    PubMed Central

    Vannier, Jean

    2012-01-01

    Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5) Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways. PMID:23300612

  19. The controversial "Cambrian" fossils of the Vindhyan are real but more than a billion years older.

    PubMed

    Bengtson, Stefan; Belivanova, Veneta; Rasmussen, Birger; Whitehouse, Martin

    2009-05-12

    The age of the Vindhyan sedimentary basin in central India is controversial, because geochronology indicating early Proterozoic ages clashes with reports of Cambrian fossils. We present here an integrated paleontologic-geochronologic investigation to resolve this conundrum. New sampling of Lower Vindhyan phosphoritic stromatolitic dolomites from the northern flank of the Vindhyans confirms the presence of fossils most closely resembling those found elsewhere in Cambrian deposits: annulated tubes, embryo-like globules with polygonal surface pattern, and filamentous and coccoidal microbial fabrics similar to Girvanella and Renalcis. None of the fossils, however, can be ascribed to uniquely Cambrian or Ediacaran taxa. Indeed, the embryo-like globules are not interpreted as fossils at all but as former gas bubbles trapped in mucus-rich cyanobacterial mats. Direct dating of the same fossiliferous phosphorite yielded a Pb-Pb isochron of 1,650 +/- 89 (2sigma) million years ago, confirming the Paleoproterozoic age of the fossils. New U-Pb geochronology of zircons from tuffaceous mudrocks in the Lower Vindhyan Porcellanite Formation on the southern flank of the Vindhyans give comparable ages. The Vindhyan phosphorites provide a window of 3-dimensionally preserved Paleoproterozoic fossils resembling filamentous and coccoidal cyanobacteria and filamentous eukaryotic algae, as well as problematic forms. Like Neoproterozoic phosphorites a billion years later, the Vindhyan deposits offer important new insights into the nature and diversity of life, and in particular, the early evolution of multicellular eukaryotes.

  20. Growth patterns of the Cambrian microbialite: Phototropism and speciation of Epiphyton

    NASA Astrophysics Data System (ADS)

    Woo, J.; Chough, S. K.

    2010-07-01

    Microbes started constructing shallow marine stromatolitic bioherms in the Archean, but they transferred their role as a major buildup maker to metazoans in Phanerozoic. Microbial buildups often recovered their predominance in the carbonate platform when reefal metazoan communities collapsed. Epiphyton, an extinct taxon of calcified microbe that possessed branching filamentous trichomes, was an important reef builder in the shallow marine carbonate platform during Middle Cambrian, aftermath of an extinction of archaeocyath sponges which were major reef-building sessile organisms in the Early Cambrian. Here we present direct evidence of phototropism of Epiphyton, found from fossilized behavior in micro- and macro-structures of meter-scale microbial bioherms of the Zhangxia Formation (Middle Cambrian), North China Platform, Shandong Province, China. The bioherms consist of stacked growth layers with the inner and outer divisions divided by distinct boundary. The inner division of growth layers of the Epiphyton bioherm is dominated by dense uniform bush-shaped Epiphyton thalli, whereas the curved outer division has layered texture normal to the surface, comprised of elongated and chambered thalli. It suggests that photosynthetic Epiphyton reacted actively to the spatial changes in intensity of sunlight, controlled by angle of illumination on the curved growth surface of the bioherm. The inner and the outer divisions comprise different morpho-types of Epiphyton. The spatial distributions of different morpho-types in variously illuminated divisions of Epiphyton might have caused further speciation of Epiphyton.

  1. Neoproterozoic–Cambrian stratigraphic framework of the Anti-Atlas and Ouzellagh promontory (High Atlas), Morocco

    USGS Publications Warehouse

    Alvaro, Jose Javier; Benziane, Fouad; Thomas, Robert; Walsh, Gregory J.; Yazidi, Abdelaziz

    2014-01-01

    In the last two decades, great progress has been made in the geochronological, chrono- and chemostratigraphic control of the Neoproterozoic and Cambrian from the Anti-Atlas Ranges and the Ouzellagh promontory (High Atlas). As a result, the Neoproterozoic is lithostratigraphically subdivided into: (i) the Lkest-Taghdout Group (broadly interpreted at c. 800–690 Ma) representative of rift-to-passive margin conditions on the northern West African craton; (ii) the Iriri (c. 760–740 Ma), Bou Azzer (c. 762–697 Ma) and Saghro (c. 760?–610 Ma) groups, the overlying Anezi, Bou Salda, Dadès and Tiddiline formations localized in fault-grabens, and the Ouarzazate Supergroup (c. 615–548 Ma), which form a succession of volcanosedimentary complexes recording the onset of the Pan-African orogeny and its aftermath; and (iii) the Taroudant (the Ediacaran–Cambrian boundary lying in the Tifnout Member of the Adoudou Formation), Tata, Feijas Internes and Tabanite groups that have recorded development of the late Ediacaran–Cambrian Atlas Rift. Recent discussions of Moroccan strata to select new global GSSPs by the International Subcommissions on Ediacaran and Cambrian Stratigraphy have raised the stratigraphic interest in this region. A revised and updated stratigraphic framework is proposed here to assist the tasks of both subcommissions and to fuel future discussions focused on different geological aspects of the Neoproterozoic–Cambrian time span.

  2. Sophisticated digestive systems in early arthropods.

    PubMed

    Vannier, Jean; Liu, Jianni; Lerosey-Aubril, Rudy; Vinther, Jakob; Daley, Allison C

    2014-05-02

    Understanding the way in which animals diversified and radiated during their early evolutionary history remains one of the most captivating of scientific challenges. Integral to this is the 'Cambrian explosion', which records the rapid emergence of most animal phyla, and for which the triggering and accelerating factors, whether environmental or biological, are still unclear. Here we describe exceptionally well-preserved complex digestive organs in early arthropods from the early Cambrian of China and Greenland with functional similarities to certain modern crustaceans and trace these structures through the early evolutionary lineage of fossil arthropods. These digestive structures are assumed to have allowed for more efficient digestion and metabolism, promoting carnivory and macrophagy in early arthropods via predation or scavenging. This key innovation may have been of critical importance in the radiation and ecological success of Arthropoda, which has been the most diverse and abundant invertebrate phylum since the Cambrian.

  3. Middle to late Cambrian shallow marine trace fossils from the Imfout Syncline (Western Meseta, Morocco): Palaeoecological and palaeoenvironmental significance in NW-Gondwana

    NASA Astrophysics Data System (ADS)

    Oukassou, Mostafa; Lagnaoui, Abdelouahed; Raji, Mohammed; Michard, André; Saddiqi, Omar

    2017-05-01

    The present research provides the first evidence of invertebrate activity assigned to the ichnogenus Selenichnites occurring together with moderately diverse ichnofossils from the middle to late Cambrian of the Moroccan Meseta. The invertebrate traces occur in sandstone strata of the El Hank Formation within the Imfout Syncline, in the northern part of the Rehamna Massif (Coastal Block, western Moroccan Meseta). Bedding surfaces from the top of the El Hank Formation near the Imfout Dam show diverse forms of current ripples and distincts crescentic ichnofossils in concave epirelief scattered on the surface. In this section, the traces provide evidence of the ethology of an organism inhabiting the relatively shallow waters of the area during this time. Selenichnites co-occurs with the ichnogenera Arenicolites, Diplocraterion, Lingulichnus, Monocraterion, Skolithos and unidentified burrows, and the ichnoassemblage is referred to the Skolithos ichnofacies. These traces can be referred to arthropods (e.g. polychaete worms and amphipod crustaceans), lingulid brachiopods, annelids and/or phoronids. The Imfout Selenichnites represents the first occurrence of this ichnogenus from the Cambrian of the Moroccan Meseta, and the second from the Cambrian deposits of Morocco. The potential tracemakers are still questionable, but were most likely xiphosurans, trilobites, euthycarcinoids or crustaceans. If so, the Imfout traces could be among the oldest pieces of evidence for the presence of horseshoe crabs during the Cambrian. The combination of sedimentological and ichnological data indicates that the El Hank Formation was deposited in a sublittoral soft ground environment next to a sandy shore. It was originally part of an early Palaeozoic shallow marine epicontinental platform in west-central Morocco. In addition to the equivalent Cambrian deposits from the Anti-Atlas, the El Hank Formation constituted a part of the northern Gondwana platform domain during the transgression

  4. The Cambrian Ross Orogeny in northern Victoria Land (Antarctica) and New Zealand: A synthesis

    USGS Publications Warehouse

    Federico, L.; Capponi, G.; Crispini, L.; Bradshaw, J.D.

    2007-01-01

    In the Cambrian, the paleo-Pacific margin of the Gondwana supercontinent included East Antarctica, Australia, Tasmania and New Zealand and was affected by themajor Ross-Delamerian Orogeny. In Antarctica, evidence suggests that this resulted from oblique subduction and that in northern Victoria Land it was accompanied by the opening and subsequent closure of a back-arc basin. Comparison of the type and timing of sedimentary, magmatic and metamorphic events in areas noted above shows strong similarities between northern Victoria Land and New Zealand. In both regions Middle Cambrian volcanites are interpreted as arc/back-arc assemblages produced by west-directed subduction; sediments interbedded with the volcanites show provenance both from the arc and from the Gondwana margin and therefore place the basin close to the continent. Back-arc closure in the Late Cambrian was likely accomplished through a second subduction system

  5. Cambrian ophiolite complexes in the Beishan area, China, southern margin of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Shi, Yuruo; Zhang, Wei; Kröner, Alfred; Li, Linlin; Jian, Ping

    2018-03-01

    We present zircon ages and geochemical data for Cambrian ophiolite complexes exposed in the Beishan area at the southern margin of the Central Asian Orogenic Belt (CAOB). The complexes consist of the Xichangjing-Xiaohuangshan and Hongliuhe-Yushishan ophiolites, which both exhibit complete ophiolite stratigraphy: chert, basalt, sheeted dikes, gabbro, mafic and ultramafic cumulates and serpentinized mantle peridotites. Zircon grains of gabbro samples yielded 206Pb/238U ages of 516 ± 8, 521 ± 4, 528 ± 3 and 535 ± 6 Ma that reflect the timing of gabbro emplacement. The geochemical data of the basaltic rocks show enrichment in large-ion lithophile elements and depletion in the high field strength elements relative to normal mid-oceanic ridge basalt (NMORB) in response to aqueous fluids or melts expelled from the subducting slab. The gabbro samples have higher whole-rock initial 87Sr/86Sr ratios and lower positive εNd(t) values than NMORB. These geochemical signatures resulted from processes or conditions that are unique to subduction zones, and the ophiolites are therefore likely to have formed within a supra-subduction zone (SSZ) environment. We suggest that the Cambrian ophiolite complexes in the Beishan area formed within a SSZ setting, reflecting an early Paleozoic subduction of components of the Paleo-Central Asian Ocean and recording an early Paleozoic southward subduction event in the southern CAOB along the northern margin of the Tarim and North China Cratons.

  6. Reconstructing the Avalon continent: Marginal to inner platform transition in the Cambrian of southern New Brunswick

    USGS Publications Warehouse

    Landing, E.

    1996-01-01

    A west to east, marginal to inner Avalonian platform transition, comparable to that in southeast Newfoundland and southern Britain, is present in the Cambrian of southern New Brunswick. The Saint John - Caton's Island - Hanford Brook area lay on the marginal platform, and its thick, uppermost Precambrian - lower Lower Cambrian is unconformably overlain by trilobite-bearing, upper Lower Cambrian. An inner platform remnant is preserved in the Cradle Brook outlier 60 km northeast of Saint John. In contrast to the marginal platform sequences, the Cradle Brook outlier has a very thin lower Lower Cambrian and has middle Lower Cambrian strata (Bonavista Group) not present on the marginal platform. The Cradle Brook Lower Cambrian closely resembles inner platform successions in eastern Massachusetts and Trinity and Placentia bays, southeast Newfoundland. A limestone with Camenella baltica Zone fossils on Cradle Brook seems to be the peritidal limestone cap of the subtrilobitic Lower Cambrian known in Avalonian North America (Fosters Point Formation) and England (Home Farm Member).

  7. The Cambrian Evolutionary Explosion: Novel Evidence from Fossils Studied by X-ray Tomography

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Jun-Yuan

    The Cambrian explosion (from 542 million years to 488 million years ago) is one of the greatest mysteries in evolutionary biology. It wasn't until this period that complex organisms became common and diverse. the magnitude of the event can be understood based on the contrast between the biota and the degree of diversity of the fossils from both sides. great advances have been made in Cambrian palaeontology over the past century, especially the discovery of the well-preserved soft-bodied fauna from the Middle Cambrian Burgess Shale and the Lower Cambrian Maotianshan Shale deposits. The Cambrian side of the "Cambrian explosion" ismore » richly illustrated and contrasts greatly with the Precambrian side. The study of these extraordinarily preserved fossil biota is extremely difficult. A major challenge is 3-D reconstruction and determining the patter of the cell organization in Weng'an embryos and their buried structures in Maotianshan Shale fossils. This talk will show that two recent technological approaches, propagation phase contrast synchrotron x-ray microtomography and microtomography, provide unique analytical tools that permit the nondestructive computational examination and visualization of the internal and buried characters in virtual sections in any plane, and virtual 3-D depictions of internal structures.« less

  8. Darwin's dilemma: the realities of the Cambrian ‘explosion’

    PubMed Central

    Conway Morris, Simon

    2006-01-01

    The Cambrian ‘explosion’ is widely regarded as one of the fulcrum points in the history of life, yet its origins and causes remain deeply controversial. New data from the fossil record, especially of Burgess Shale-type Lagerstätten, indicate, however, that the assembly of bodyplans is not only largely a Cambrian phenomenon, but can already be documented in fair detail. This speaks against a much more ancient origin of the metazoans, and current work is doing much to reconcile the apparent discrepancies between the fossil record, including the Ediacaran assemblages of latest Neoproterozoic age and molecular ‘clocks’. Hypotheses to explain the Cambrian ‘explosion’ continue to be generated, but the recurrent confusion of cause and effect suggests that the wrong sort of question is being asked. Here I propose that despite its step-like function this evolutionary event is the inevitable consequence of Earth and biospheric change. PMID:16754615

  9. Development, triploblastism, physics of wetting and the Cambrian explosion.

    PubMed

    Fleury, Vincent

    2013-09-01

    The Cambrian explosion is characterized by the sudden outburst of organized animal plans, which occurred circa 530 M years ago. Around that time, many forms of animal life appeared, including several which have since disappeared. There is no general consensus about "why" this happened, and why it had any form of suddenness. However, all organized animal plans share a common feature: they are triploblastic, i.e., composed of 3 layers of tissue, endoderm, ectoderm and mesoderm. I show here that, within simple hypotheses, the formation of the mesoderm has intrinsically a physical exponential dynamics, leading rapidly to triploblastism, and eventually, to animal formation. A novel physico-mathematical framework including epithelium-mesenchyme transition, visco-elastic constitutive equations, and conservation laws, is presented which allows one to describe gastrulation as a self-wetting phenomenon of a soft solid onto itself. This phenomenon couples differentiation and migration during gastrulation, and leads in a closed form to an exponential scaling law for the formation of the mesoderm. Therefore, the Cambrian explosion might have started, actually, by a true viscoelastic "explosion": the exponential run-away of mesenchymal cells.

  10. Decoupling biogeochemical records, extinction, and environmental change during the Cambrian SPICE event

    PubMed Central

    Schiffbauer, James D.; Huntley, John Warren; Fike, David A.; Jeffrey, Matthew Jarrell; Gregg, Jay M.; Shelton, Kevin L.

    2017-01-01

    Several positive carbon isotope excursions in Lower Paleozoic rocks, including the prominent Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE), are thought to reflect intermittent perturbations in the hydrosphere-biosphere system. Models explaining these secular changes are abundant, but the synchronicity and regional variation of the isotope signals are not well understood. Examination of cores across a paleodepth gradient in the Upper Cambrian central Missouri intrashelf basin (United States) reveals a time-transgressive, facies-dependent nature of the SPICE. Although the SPICE event may be a global signal, the manner in which it is recorded in rocks should and does vary as a function of facies and carbonate platform geometry. We call for a paradigm shift to better constrain facies, stratigraphic, and biostratigraphic architecture and to apply these observations to the variability in magnitude, stratigraphic extent, and timing of the SPICE signal, as well as other biogeochemical perturbations, to elucidate the complex processes driving the ocean-carbonate system. PMID:28275734

  11. The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

    USGS Publications Warehouse

    Dong, X.-P.; Bengtson, S.; Gostling, N.J.; Cunningham, J.A.; Harvey, T.H.P.; Kouchinsky, A.; Val'Kov, A.K.; Repetski, J.E.; Stampanoni, M.; Marone, F.; Donoghue, P.C.J.

    2010-01-01

    Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem-scalidophoran or a stem-priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val'kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia. ?? The Palaeontological Association.

  12. New zircon ages on the Cambrian-Ordovician volcanism of the Southern Gemericum basement (Western Carpathians, Slovakia): SHRIMP dating, geochemistry and provenance

    NASA Astrophysics Data System (ADS)

    Vozárová, Anna; Rodionov, Nickolay; Šarinová, Katarína; Presnyakov, Sergey

    2017-09-01

    The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian-Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U-Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian-Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650-550 Ma), Tonian-Stenian (1.1-0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian-Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.

  13. Decoupling of body-plan diversification and ecological structuring during the Ediacaran-Cambrian transition: evolutionary and geobiological feedbacks.

    PubMed

    Mángano, M Gabriela; Buatois, Luis A

    2014-04-07

    The rapid appearance of bilaterian clades at the beginning of the Phanerozoic is one of the most intriguing topics in macroevolution. However, the complex feedbacks between diversification and ecological interactions are still poorly understood. Here, we show that a systematic and comprehensive analysis of the trace-fossil record of the Ediacaran-Cambrian transition indicates that body-plan diversification and ecological structuring were decoupled. The appearance of a wide repertoire of behavioural strategies and body plans occurred by the Fortunian. However, a major shift in benthic ecological structure, recording the establishment of a suspension-feeder infauna, increased complexity of the trophic web, and coupling of benthos and plankton took place during Cambrian Stage 2. Both phases were accompanied by different styles of ecosystem engineering, but only the second one resulted in the establishment of the Phanerozoic-style ecology. In turn, the suspension-feeding infauna may have been the ecological drivers of a further diversification of deposit-feeding strategies by Cambrian Stage 3, favouring an ecological spillover scenario. Trace-fossil information strongly supports the Cambrian explosion, but allows for a short time of phylogenetic fuse during the terminal Ediacaran-Fortunian.

  14. Decoupling of body-plan diversification and ecological structuring during the Ediacaran–Cambrian transition: evolutionary and geobiological feedbacks

    PubMed Central

    Mángano, M. Gabriela; Buatois, Luis A.

    2014-01-01

    The rapid appearance of bilaterian clades at the beginning of the Phanerozoic is one of the most intriguing topics in macroevolution. However, the complex feedbacks between diversification and ecological interactions are still poorly understood. Here, we show that a systematic and comprehensive analysis of the trace-fossil record of the Ediacaran–Cambrian transition indicates that body-plan diversification and ecological structuring were decoupled. The appearance of a wide repertoire of behavioural strategies and body plans occurred by the Fortunian. However, a major shift in benthic ecological structure, recording the establishment of a suspension-feeder infauna, increased complexity of the trophic web, and coupling of benthos and plankton took place during Cambrian Stage 2. Both phases were accompanied by different styles of ecosystem engineering, but only the second one resulted in the establishment of the Phanerozoic-style ecology. In turn, the suspension-feeding infauna may have been the ecological drivers of a further diversification of deposit-feeding strategies by Cambrian Stage 3, favouring an ecological spillover scenario. Trace-fossil information strongly supports the Cambrian explosion, but allows for a short time of phylogenetic fuse during the terminal Ediacaran–Fortunian. PMID:24523279

  15. Early animal evolution: emerging views from comparative biology and geology

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.; Carroll, S. B.

    1999-01-01

    The Cambrian appearance of fossils representing diverse phyla has long inspired hypotheses about possible genetic or environmental catalysts of early animal evolution. Only recently, however, have data begun to emerge that can resolve the sequence of genetic and morphological innovations, environmental events, and ecological interactions that collectively shaped Cambrian evolution. Assembly of the modern genetic tool kit for development and the initial divergence of major animal clades occurred during the Proterozoic Eon. Crown group morphologies diversified in the Cambrian through changes in the genetic regulatory networks that organize animal ontogeny. Cambrian radiation may have been triggered by environmental perturbation near the Proterozoic-Cambrian boundary and subsequently amplified by ecological interactions within reorganized ecosystems.

  16. Upper Cambrian chitons (Mollusca, polyplacophora) from Missouri, USA

    USGS Publications Warehouse

    Pojeta, J.; Vendrasco, M.J.; Darrough, G.

    2010-01-01

    Numerous new specimens reveal a greater presence of chitons in Upper Cambrian rocks than previously suspected. Evidence is presented showing that the chiton esthete sensory system is present in all chiton species in this study at the very beginning of the known polyplacophoran fossil record. The stratigraphic occurrences and paleobiogeography of Late Cambrian chitons are documented. The 14 previously-named families of Cambrian and Ordovician chitons are reviewed and analyzed. Aulochitonidae n. fam. is defined, based on Aulochiton n. gen.; A. sannerae n. sp. is also defined. The long misunderstood family Preacanthochitonidae and its type genus Preacanthochiton Bergenhayn, 1960, are placed in synonymy with Mattheviidae and Chelodes Davidson & King, 1874, respectively; Eochelodes Marek, 1962, also is placed in synonymy with Chelodes, and Elongata Stinchcomb & Darrough, 1995, is placed in synonymy with Hemithecella Ulrich & Bridge, 1941. At the species level, H. elongata Stinchcomb & Darrough, 1995, and Elongata perplexa Stinchcomb & Darrough, 1995, are placed in synonymy with H. eminensis Stinchcomb & Darrough, 1995. The Ordovician species H. abrupta Stinchcomb & Darrough, 1995, is transferred to the genus Chelodes as C. abrupta (Stinchcomb & Darrough, 1995). The Ordovician species Preacanthochiton baueri Hoare & Pojeta, 2006, is transferred to the genus Helminthochiton as H. ? baueri (Hoare & Pojeta, 2006). The Ordovician species H. marginatus Hoare & Pojeta, 2006, is transferred to the genus Litochiton as L. marginatus (Hoare & Pojeta, 2006). Matthevia walcotti Runnegar, Pojeta, Taylor, & Collins, 1979, is treated as a synonym of Hemithecella expansa Ulrich & Bridge, 1941. In addition, other multivalved Cambrian mollusks are discussed; within this group, Dycheiidae n. fam. is defined, as well as Paradycheia dorisae n. gen. and n. sp. Cladistic analysis indicates a close relationship among the genera here assigned to the Mattheviidae, and between Echinochiton Pojeta

  17. Cambrian Series 3 carbonate platform of Korea dominated by microbial-sponge reefs

    NASA Astrophysics Data System (ADS)

    Hong, Jongsun; Lee, Jeong-Hyun; Choh, Suk-Joo; Lee, Dong-Jin

    2016-07-01

    Metazoans have been considered as negligible components of Cambrian Series 3 and Furongian microbial-dominated reefs, in contrast to their presence in earlier Terreneuvian-Cambrian Series 2 microbial-archaeocyath reefs. However, recent discoveries of sponges in Cambrian Series 3-Furongian reefs of Australia, China, Iran, USA, and Korea have raised question regarding their contribution in terms of carbonate platform development, which have never been assessed. This study examines Cambrian Series 3 deposits of the Daegi Formation, Korea to elucidate this question. The 100-m-thick middle part of the Daegi Formation is dominated by boundstone facies, which occupies 45% of the study interval, as well as bioclastic wackestone to packstone, bioclastic grainstone, and ooid packstone to grainstone facies. The Daegi reefs are primarily thrombolitic in composition, with 90% (n = 26/29) of the reefs containing an average of 9% sponges in aerial percentage calculated from thin sections. Lithistid sponges composed of peloidal fabrics, some desma spicules, and spicule networks commonly occupy the interstitial space in microbial clusters, are encrusted by mesoclots and Epiphyton, and are surrounded by micrite. Subordinate non-lithistid demosponges occur within clusters of microbial elements. The middle Daegi Formation can be largely subdivided into shoal environment dominated by grainstone to packstone facies and shallow subtidal platform interior environment located behind shoal with wackestone to packstone facies. The microbial-sponge reefs mainly developed around platform interior as patch reefs. The current study indicates that metazoans in the form of lithistid and non-lithistid demosponges are nearly ubiquitously incorporated in Daegi reefs and contributed greatly to the formation of microbial-sponge reefs as well as carbonate platform during the time. Study of these microbial-sponge reefs and their distribution within the carbonate platform may help us to understand how

  18. Evolution of the seawater sulfate sulfur composition through the Cambrian Period: Implications from carbonate-associated sulfate

    NASA Astrophysics Data System (ADS)

    Wotte, T.

    2012-12-01

    Cambrian carbonate successions of Australia, W-Gondwana, Kazakhstan, Laurentia, and Siberia were investigated for their sulfur isotopic composition of carbonate-associated sulfate (CAS). For a secure CAS extraction a repeated leaching procedure with NaCl solution was applied as a standard protocol with supplementary analyses of pre-leach sulfate concentrations and δ34SNaCl, and chromium-reducible sulfur (CRS) concentrations and δ34SCRS as routine checks on possible contamination. Additionally, δ13Ccarb, δ18Ocarb, and elemental concentrations (Ca, Fe, Mg, Mn, Sr) of the carbonate host rock were analyzed in order to constrain diagenetic alteration of the measured δ34SCAS. About 200 δ34SCAS values were generated using this analytical procedure which allows the most precise state of the art methodology for CAS and CRS extraction. The most primary δ34SCAS values vary between 24‰ and 33‰ for successions of the transition from Cambrian Series 2 to Cambrian Series 3 (traditional Lower-Middle Cambrian boundary) and between 25‰ and 48‰ for the Cambrian Series 3-Furongian (Upper Cambrian) interval, respectively. These new δ34SCAS data are valuable proxies to verify paleoecological and paleoenvironmental information. They further close an obvious gap of the Cambrian δ34SCAS record, composed of δ34SCAS values, ranging from about 20‰ up to 70‰ (SPICE-event). However, the individual data sets of this Cambrian δ34SCAS pool were generated using various methods of CAS extraction, thus offering the potential of significant differences in the final δ34SCAS values which are consequently not per se comparable with each other. The new δ34SCAS data of worldwide Cambrian sections will be discussed in the context of this problematic.

  19. A Late Cambrian Carbon Isotope Excursion Recorded in Passive Margin Dolostones of the Central Appalachian Basin, USA.

    NASA Astrophysics Data System (ADS)

    Mackey, J. E.; Stewart, B. W.

    2016-12-01

    A Late Cambrian global positive carbon isotope excursion, known as the SPICE event [1,2] is linked to possible widespread ocean anoxia and enhanced carbon burial [3,4]. We report data from the central Appalachian Conasauga Group from the upper portion of the Middle Cambrian Maryville limestone, through the Late Cambrian Nolichucky shale and Maynardville limestone members. A geochemical, macro-, and micro-scale analyses of core material from southeastern Ohio was carried out to further constrain the timing of oceanic anoxia and trace element geochemistry relative to sediment fluxes occurring at the transition of the Middle to Late Cambrian. The section represents condensed, passive margin shale deposition and carbonate ramp development on the continental shelf of Laurentia. Carbonate sediments (primarily diagenetic dolomite) record a positive δ13C (relative to V-PDB) excursion starting in the upper Nolichucky shale member, reaching its peak (+4.0) in the overlying Maynardville limestone. At this location, there is an offset between the onlap Nolichucky shale deposition and start of the C isotope excursion; this was reported as well in a carbonate section further south of this location [2], on the other side of an extensional feature (Rome Trough) that formed a deep marine basin during Cambrian time. The condensed shale package and relatively low TOC content in our samples is likely due to the combination of a shallow, upslope basin location and isostatic influence on passive margin sedimentation. However, within the Rome Trough, the Nolichucky shale is rich in organic carbon and a recent target of hydrocarbon exploration. The data suggest a possible link between deposition of this shale and the global SPICE event. The robustness of the Late Cambrian δ13C excursion in diagenetically altered sediments and association with hydrocarbon bearing units indicates its utility as a stratigraphic indicator and as a target for exploration. Ongoing geochemical work will focus

  20. An Independent Constraint on Marine Sulfate Levels at the Ediacaran-Cambrian Transition

    NASA Astrophysics Data System (ADS)

    Blättler, C. L.; Bergmann, K.; Higgins, J. A.

    2016-12-01

    Sediments from the Ediacaran-Cambrian transition in Oman record major excursions in the isotopic systems of carbon (δ13C) and sulfur (δ34S). The significance of these geochemical signals has been the subject of much debate, focusing on their association with biotic innovations and extinctions, oxygenation of the atmosphere and oceans, and changes in seawater chemistry. The concentration of marine sulfate during this time interval remains particularly uncertain, despite being a critical variable for several hypotheses related to these excursions. We present an independent constraint on relative sulfate concentrations based on calcium-isotope data from the Ara Group evaporites (547-540 Ma) of the South Oman Salt Basin. Anhydrite samples from five boreholes span the A1 through A5 carbonate-evaporite sequences, lying on both sides of the Precambrian-Cambrian boundary. The approach developed by Blättler and Higgins (2014) is used to quantify the degree of isotopic distillation of calcium by sulfate mineral precipitation. The absence of significant distillation (expressed by δ44/40Ca variability in the anhydrite) suggests that Ca/SO4 ratios in the latest Ediacaran and earliest Cambrian were greater than during the Neogene or Permian. These results, together with previously published analyses of halite fluid inclusions and models of sulfur cycling, give a clearer estimate of how marine sulfate levels may have evolved during this dynamic period in Earth history.

  1. Exceptionally preserved crustaceans from western Canada reveal a cryptic Cambrian radiation

    NASA Astrophysics Data System (ADS)

    Harvey, Thomas H. P.; Vélez, Maria I.; Butterfield, Nicholas J.

    2012-01-01

    The early history of crustaceans is obscured by strong biases in fossil preservation, but a previously overlooked taphonomic mode yields important complementary insights. Here we describe diverse crustacean appendages of Middle and Late Cambrian age from shallow-marine mudstones of the Deadwood Formation in western Canada. The fossils occur as flattened and fragmentary carbonaceous cuticles but provide a suite of phylogenetic and ecological data by virtue of their detailed preservation. In addition to an unprecedented range of complex, largely articulated filtering limbs, we identify at least four distinct types of mandible. Together, these fossils provide the earliest evidence for crown-group branchiopods and total-group copepods and ostracods, extending the respective ranges of these clades back from the Devonian, Pennsylvanian, and Ordovician. Detailed similarities with living forms demonstrate the early origins and subsequent conservation of various complex food-handling adaptations, including a directional mandibular asymmetry that has persisted through half a billion years of evolution. At the same time, the Deadwood fossils indicate profound secular changes in crustacean ecology in terms of body size and environmental distribution. The earliest radiation of crustaceans is largely cryptic in the fossil record, but "small carbonaceous fossils" reveal organisms of surprisingly modern aspect operating in an unfamiliar biosphere.

  2. The significance of 24-norcholestanes, triaromatic steroids and dinosteroids in oils and Cambrian-Ordovician source rocks from the cratonic region of the Tarim Basin, NW China

    USGS Publications Warehouse

    Li, Meijun; Wang, T.-G.; Lillis, Paul G.; Wang, Chunjiang; Shi, Shengbao

    2012-01-01

    Two oil families in Ordovician reservoirs from the cratonic region of the Tarim Basin are distinguished by the distribution of regular steranes, triaromatic steroids, norcholestanes and dinosteroids. Oils with relatively lower contents of C28 regular steranes, C26 20S, C26 20R + C27 20S and C27 20R regular triaromatic steroids, dinosteranes, 24-norcholestanes and triaromatic dinosteroids originated from Middle–Upper Ordovician source rocks. In contrast, oils with abnormally high abundances of the above compounds are derived from Cambrian and Lower Ordovician source rocks. Only a few oils have previously been reported to be of Cambrian and Lower Ordovician origin, especially in the east region of the Tarim Basin. This study further reports the discovery of oil accumulations of Cambrian and Lower Ordovician origin in the Tabei and Tazhong Uplifts, which indicates a potential for further discoveries involving Cambrian and Lower Ordovician sourced oils in the Tarim Basin. Dinosteroids in petroleum and ancient sediments are generally thought to be biomarkers for dinoflagellates and 24-norcholestanes for dinoflagellates and diatoms. Therefore, the abnormally high abundance of these compounds in extracts from the organic-rich sediments in the Cambrian and Lower Ordovician and related oils in the cratonic region of the Tarim Basin suggests that phytoplankton algae related to dinoflagellates have appeared and might have flourished in the Tarim Basin during the Cambrian Period. Steroids with less common structural configurations are underutilized and can expand understanding of the early development history of organisms, as well as define petroleum systems.

  3. A molecular and isotopic study of palaeoenvironmental conditions through the middle Cambrian in the Georgina Basin, central Australia

    NASA Astrophysics Data System (ADS)

    Pagès, Anais; Schmid, Susanne; Edwards, Dianne; Barnes, Stephen; He, Nannan; Grice, Kliti

    2016-08-01

    The Cambrian period marks an important point in Earth's history with profound changes in the ocean's biogeochemistry and the occurrence of the most significant evolutionary event in the history of life, the Cambrian explosion. The Cambrian explosion is described as a succession of complex cycles of extinctions and radiations. This study integrates biomarkers and their compound-specific stable carbon isotopes to investigate the palaeoenvironmental depositional conditions in middle Cambrian (Series 3) sedimentary rocks (Thorntonia Limestone, Inca Formation and Currant Bush Limestone) from two drillholes in the Undilla Sub-basin in the eastern Georgina Basin, central Australia. The occurrence of photic zone euxinia (PZE) was detected throughout these three formations by the identification of green sulfur bacteria Chlorobiaceae-derived biomarkers, including a series of 2,3,6-aryl isoprenoids and the intact biomarker isorenieratane. Pulses of enhanced PZE conditions were detected in two core intervals (90-110 mKB, Currant Bush Limestone and 170-200 mKB, Inca Formation) by an increase in the 2,3,6-aryl isoprenoids and C19 biphenyl concentrations. These enhanced PZE conditions were followed by blooms of phytoplankton, as demonstrated by the increase in algal-derived biomarker (i.e. pristane, phytane and the C19n-alkane) concentrations and compound-specific isotopes. These observations confirm that palaeoenvironmental conditions were similar to those reported for the Permian/Triassic and Triassic/Jurassic mass extinction events. The sterane distributions varied across the three formations reflecting possible changes in the phytoplanktonic communities through time. Although a rise in atmospheric oxygen during the Cambrian has been previously associated with the rapid evolution of metazoans, the ecological challenges related to widespread anoxia must have had a major influence on the evolution of life in Cambrian oceans.

  4. Palaeomagnetism and geochemistry of Early Palaeozoic rocks of the Barrandian (Teplé-Barrandian Unit, Bohemian Massif): palaeotectonic implications

    NASA Astrophysics Data System (ADS)

    Patočka, F.; Pruner, P.; Štorch, P.

    The Barrandian area (the Teplá-Barrandian unit, Bohemian Massif) provided palaeomagnetic results on Early Palaeozoic rocks and chemical data on siliciclastic sediments of both Middle Cambrian and Early Ordovician to Middle Devonian sedimentary sequences; an outcoming interpretation defined source areas of clastic material and palaeotectonic settings of the siliciclastic rock deposition. The siliciclastic rocks of the earliest Palaeozoic sedimentation cycle, deposited in the Cambrian Příbram-Jince Basin of the Barrandian, were derived from an early Cadomian volcanic island arc developed on Neoproterozoic oceanic lithosphere and accreted to a Cadomian active margin of northwestern Gondwana. Inversion of relief terminated the Cambrian sedimentation, and a successory Prague Basin subsided nearby since Tremadocian. Source area of the Ordovician and Early Silurian shallow-marine siliciclastic sediments corresponded to progressively dissected crust of continental arc/active continental margin type of Cadomian age. Since Late Ordovician onwards both synsedimentary within-plate basic volcanics and older sediments had been contributing in recognizable proportions to the siliciclastic rocks. The siliciclastic sedimentation was replaced by deposition of carbonate rocks throughout late Early Silurian to Early Devonian period of withdrawal of the Cadomian clastic material source. Above the carbonates an early Givetian flysch-like siliciclastic suite completed sedimentation in the Barrandian. In times between Middle Cambrian and Early/Middle Devonian boundary interval an extensional tectonic setting prevailed in the Teplá-Barrandian unit. The extensional regime was related to Early Palaeozoic large-scale fragmentation of the Cadomian belt of northwestern Gondwana and origin of Armorican microcontinent assemblage. The Teplá-Barrandian unit was also engaged in a peri-equatorially oriented drift of Armorican microcontinent assemblage throughout the Early Palaeozoic: respective

  5. Carbonate rocks of Cambrian and Ordovician age in the Lancaster quadrangle, Pennsylvania

    USGS Publications Warehouse

    Meisler, Harold; Becher, Albert E.

    1968-01-01

    Detailed mapping has shown that the carbonate rocks of Cambrian and Ordovician age in the Lancaster quadrangle, Pennsylvania, can be divided into 14 rock-stratigraphic units. These units are defined primarily by their relative proportions of limestone and dolomite. The oldest units, the Vintage, Kinzers, and Ledger Formations of Cambrian age, and the Conestoga Limestone of Ordovician age are retained in this report. The Zooks Corner Formation, of Cambrian age, a dolomite unit overlying the Ledger Dolomite, is named here for exposures along Conestoga Creek near the village of Zooks Corner. The Conococheague (Cambrian) and Beekmantown (Ordovician) Limestones, as mapped by earlier workers, have been elevated to group rank and subdivided into formations that are correlated with and named for geologic units in Lebanon and Berks Counties, Pa. These formations, from oldest to youngest, are the Buffalo Springs, Snitz Creek, Millbach, and Richland Formations of the Conococheague Group, and the Stonehenge, Bpler, and Ontelaunee Formations of the Beekmantown Group. The Annville and Myerstown Limestones, which are named for lithologically similar units in Dauphin and Lebanon Counties, Pa., overlie the Beekmantown Group in one small area in the quadrangle.

  6. Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba lagerstätte.

    PubMed

    Yang, Jie; Smith, Martin R; Lan, Tian; Hou, Jin-bo; Zhang, Xi-guang

    2014-04-10

    Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp. nov. from the Xiaoshiba fauna (Cambrian Stage 3, Hongjingshao Formation, Kunming, south China). Although spines are absent, the fossils' sclerites - like those of W. corrugata - are symmetrically arranged in five distinct zones. They form rows across the body, and were individually added and shed throughout growth to retain an approximately symmetrical body shape. Their development pattern suggests a molluscan affinity. The basic body plan of wiwaxiids is fundamentally conserved across two continents through Cambrian Stages 3-5 - revealing morphological stasis in the wake of the Cambrian explosion.

  7. Life cycle and morphology of a cambrian stem-lineage loriciferan.

    PubMed

    Peel, John S; Stein, Martin; Kristensen, Reinhardt Møbjerg

    2013-01-01

    Cycloneuralians form a rich and diverse element within Cambrian assemblages of exceptionally preserved fossils. Most resemble priapulid worms whereas other Cycloneuralia (Nematoda, Nematomorpha, Kinorhyncha, Loricifera), well known at the present day, have little or no fossil record. First reports of Sirilorica Peel, 2010 from the lower Cambrian Sirius Passet fauna of North Greenland described a tubular lorica covering the abdomen and part of a well developed introvert with a circlet of 6 grasping denticles near the lorica. The introvert is now known to terminate in a narrow mouth tube, while a conical anal field is also developed. Broad muscular bands between the plates in the lorica indicate that it was capable of movement by rhythmic expansion and contraction of the lorica. Sirilorica is regarded as a macrobenthic member of the stem-lineage of the miniaturised, interstitial, present day Loricifera. Like loriciferans, Sirilorica is now known to have grown by moulting. Evidence of the life cycle of Sirilorica is described, including a large post-larval stage and probably an initial larva similar to that of the middle Cambrian fossil Orstenoloricusshergoldii.

  8. Life Cycle and Morphology of a Cambrian Stem-Lineage Loriciferan

    PubMed Central

    Peel, John S.; Stein, Martin; Kristensen, Reinhardt Møbjerg

    2013-01-01

    Cycloneuralians form a rich and diverse element within Cambrian assemblages of exceptionally preserved fossils. Most resemble priapulid worms whereas other Cycloneuralia (Nematoda, Nematomorpha, Kinorhyncha, Loricifera), well known at the present day, have little or no fossil record. First reports of Sirilorica Peel, 2010 from the lower Cambrian Sirius Passet fauna of North Greenland described a tubular lorica covering the abdomen and part of a well developed introvert with a circlet of 6 grasping denticles near the lorica. The introvert is now known to terminate in a narrow mouth tube, while a conical anal field is also developed. Broad muscular bands between the plates in the lorica indicate that it was capable of movement by rhythmic expansion and contraction of the lorica. Sirilorica is regarded as a macrobenthic member of the stem-lineage of the miniaturised, interstitial, present day Loricifera. Like loriciferans, Sirilorica is now known to have grown by moulting. Evidence of the life cycle of Sirilorica is described, including a large post-larval stage and probably an initial larva similar to that of the middle Cambrian fossil Orstenoloricusshergoldii . PMID:23991198

  9. Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China).

    PubMed

    Han, Jian; Morris, Simon Conway; Ou, Qiang; Shu, Degan; Huang, Hai

    2017-02-09

    Deuterostomes include the group we belong to (vertebrates) as well as an array of disparate forms that include echinoderms, hemichordates and more problematic groups such as vetulicolians and vetulocystids. The Cambrian fossil record is well-populated with representative examples, but possible intermediates are controversial and the nature of the original deuterostome remains idealized. Here we report millimetric fossils, Saccorhytus coronarius nov. gen., nov. sp., from an Orsten-like Lagerstätte from the earliest Cambrian period of South China, which stratigraphically are amongst the earliest of deuterostomes. The bag-like body bears a prominent mouth and associated folds, and behind them up to four conical openings on either side of the body as well as possible sensory structures. An anus may have been absent, and correspondingly the lateral openings probably served to expel water and waste material. This new form has similarities to both the vetulicolians and vetulocystids and collectively these findings suggest that a key step in deuterostome evolution was the development of lateral openings that subsequently were co-opted as pharyngeal gills. Depending on its exact phylogenetic position, the meiofaunal habit of Saccorhytus may help to explain the major gap between divergence times seen in the fossil record and estimates based on molecular clocks.

  10. Stratigraphic Framework of Cambrian and Ordovician Rocks in the Appalachian Basin from Sequatchie County, Tennessee, through Eastern Kentucky, to Mingo County, West Virginia

    USGS Publications Warehouse

    Ryder, Robert T.; Crangle, Robert D.; Repetski, John E.; Harris, Anita G.

    2008-01-01

    Cross section H-H' is the seventh in a series of restored cross sections constructed by the lead author to show the stratigraphic framework of Cambrian and Ordovician rocks in the Appalachian basin from Pennsylvania to Tennessee. The sections show complexly intertongued carbonate and siliciclastic lithofacies, marked thickness variations, key marker horizons, unconformities, stratigraphic nomenclature of the Cambrian and Ordovician sequence, and major faults that offset Proterozoic basement and overlying lower Paleozoic rocks. Several of the drill holes along the cross section have yielded a variety of whole and (or) fragmented conodont elements. The identifiable conodonts are used to differentiate strata of Late Cambrian, Early Ordovician, and Middle Ordovician age, and their conodont color alteration index (CAI) values are used to establish the thermal maturity of the sequence. Previous cross sections in this series are G-G', F-F', E-E', D-D', C-C', and B-B'. Many of these cross sections (B-B', C-C', D-D', and G-G') have been improved with the addition of gamma-ray log traces, converted to digital images, and made accessible on the Web.

  11. Unlocking the early fossil record of the arthropod central nervous system

    PubMed Central

    Edgecombe, Gregory D.; Ma, Xiaoya; Strausfeld, Nicholas J.

    2015-01-01

    Extant panarthropods (euarthropods, onychophorans and tardigrades) are hallmarked by stunning morphological and taxonomic diversity, but their central nervous systems (CNS) are relatively conserved. The timing of divergences of the ground pattern CNS organization of the major panarthropod clades has been poorly constrained because of a scarcity of data from their early fossil record. Although the CNS has been documented in three-dimensional detail in insects from Cenozoic ambers, it is widely assumed that these tissues are too prone to decay to withstand other styles of fossilization or geologically older preservation. However, Cambrian Burgess Shale-type compressions have emerged as sources of fossilized brains and nerve cords. CNS in these Cambrian fossils are preserved as carbon films or as iron oxides/hydroxides after pyrite in association with carbon. Experiments with carcasses compacted in fine-grained sediment depict preservation of neural tissue for a more prolonged temporal window than anticipated by decay experiments in other media. CNS and compound eye characters in exceptionally preserved Cambrian fossils predict divergences of the mandibulate and chelicerate ground patterns by Cambrian Stage 3 (ca 518 Ma), a dating that is compatible with molecular estimates for these splits. PMID:26554038

  12. Cambrian-lower Middle Ordovician passive carbonate margin, southern Appalachians: Chapter 14

    USGS Publications Warehouse

    Read, J. Fred; Repetski, John E.

    2012-01-01

    The southern Appalachian part of the Cambrian–Ordovician passive margin succession of the great American carbonate bank extends from the Lower Cambrian to the lower Middle Ordovician, is as much as 3.5 km (2.2 mi) thick, and has long-term subsidence rates exceeding 5 cm (2 in.)/k.y. Subsiding depocenters separated by arches controlled sediment thickness. The succession consists of five supersequences, each of which contains several third-order sequences, and numerous meter-scale parasequences. Siliciclastic-prone supersequence 1 (Lower Cambrian Chilhowee Group fluvial rift clastics grading up into shelf siliciclastics) underlies the passive margin carbonates. Supersequence 2 consists of the Lower Cambrian Shady Dolomite–Rome-Waynesboro Formations. This is a shallowing-upward ramp succession of thinly bedded to nodular lime mudstones up into carbonate mud-mound facies, overlain by lowstand quartzose carbonates, and then a rimmed shelf succession capped by highly cyclic regressive carbonates and red beds (Rome-Waynesboro Formations). Foreslope facies include megabreccias, grainstone, and thin-bedded carbonate turbidites and deep-water rhythmites. Supersequence 3 rests on a major unconformity and consists of a Middle Cambrian differentiated rimmed shelf carbonate with highly cyclic facies (Elbrook Formation) extending in from the rim and passing via an oolitic ramp into a large structurally controlled intrashelf basin (Conasauga Shale). Filling of the intrashelf basin caused widespread deposition of thin quartz sandstones at the base of supersequence 4, overlain by widespread cyclic carbonates (Upper Cambrian lower Knox Group Copper Ridge Dolomite in the south; Conococheague Formation in the north). Supersequence 5 (Lower Ordovician upper Knox in the south; Lower to Middle Ordovician Beekmantown Group in the north) has a basal quartz sandstone-prone unit, overlain by cyclic ramp carbonates, that grade downdip into thrombolite grainstone and then storm

  13. Evolution of oceanic molybdenum and uranium reservoir size around the Ediacaran-Cambrian transition: Evidence from western Zhejiang, South China

    NASA Astrophysics Data System (ADS)

    Xiang, Lei; Schoepfer, Shane D.; Shen, Shu-zhong; Cao, Chang-qun; Zhang, Hua

    2017-04-01

    The "Cambrian explosion" is one of the most fascinating episodes of diversification in the history of life; however, its relationship to the oxygenation of the oceans and atmosphere around the Ediacaran-Cambrian transition is not fully understood. Marine inventories of redox-sensitive trace elements reflect the relative balance of oxidative weathering on land and deposition in anoxic water masses, and can be used to explore the evolution of oceanic and atmospheric redox conditions. For this study, we conducted a series of geochemical analyses on the upper Lantian, Piyuancun, and Hetang formations in the Chunye-1 well, part of the lower Yangtze Block in western Zhejiang. Iron speciation results indicate that the entire studied interval was deposited under anoxic conditions, with three intervals of persistent euxinia occurring in the uppermost Lantian Fm., the lower Hetang Formation (Fm.), and the upper Hetang Fm. Molybdenum (Mo) and uranium (U) contents and Mo/TOC and U/TOC ratios from the anoxic/euxinic intervals of the Chunye-1 well, combined with published data from the sections in the middle and upper Yangtze Block, suggest that the oceanic Mo reservoir declined consistently from the Ediacaran to Cambrian Stage 3, while the size of the oceanic U reservoir remained relatively constant. Both metals were depleted in the ocean in lower Cambrian Stage 4, before increasing markedly at the end of Stage 4. The lack of an apparent increase in the size of the marine Mo and U reservoir from the upper Ediacaran to Cambrian Stage 3 suggests that oxic water masses did not expand until Cambrian Stage 4. The increase in marine Mo and U availability in the upper Hetang Fm. may have been due to the expansion of oxic water masses in the oceans, associated with oxygenation of the atmosphere during Cambrian Stage 4. This expansion of oxic waters in the global ocean postdates the main phase of Cambrian diversification, suggesting that pervasive oxygenation of the ocean on a large

  14. Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept

    NASA Astrophysics Data System (ADS)

    Landing, Ed; Geyer, Gerd; Brasier, Martin D.; Bowring, Samuel A.

    2013-08-01

    Use of the first appearance datum (FAD) of a fossil to define a global chronostratigraphic unit's base can lead to intractable correlation and stability problems. FADs are diachronous—they reflect species' evolutionary history, dispersal, biofacies, preservation, collection, and taxonomy. The Cambrian Evolutionary Radiation is characterised by diachronous FADs, biofacies controls, and provincialism of taxa and ecological communities that confound a stable Lower Cambrian chronostratigraphy. Cambrian series and stage definitions require greater attention to assemblage zone successions and non-biostratigraphic, particularly carbon isotope, correlation techniques such as those that define the Ediacaran System base. A redefined, basal Cambrian Trichophycus pedum Assemblage Zone lies above the highest Ediacaran-type biotas (vendobionts, putative metazoans, and calcareous problematica such as Cloudina) and the basal Asteridium tornatum-Comasphaeridium velvetum Zone (acritarchs). This definition and the likely close correspondence of evolutionary origin and local FAD of T. pedum preserves the Fortune Head, Newfoundland, GSSP of the Cambrian base and allows the presence of sub-Cambrian, branched ichnofossils. The sub-Tommotian-equivalent base of Stage 2 (a suggested "Laolinian Stage") should be defined by the I'/L4/ZHUCE δ13C positive peak, bracketed by the lower ranges of Watsonella crosbyi and Aldanella attleborensis (molluscs) and the Skiagia ornata-Fimbrioglomerella membranacea Zone (acritarchs). The W. crosbyi and A. attleborensis FADs cannot define a Stage 2 base as they are diachronous even in the Newfoundland "type" W. crosbyi Zone. The Series 2 base cannot be based on a species' FAD owing to the provincialism of skeletalised metazoans in the Terreneuvian-Series 2 boundary interval and global heterochrony of the oldest trilobites. A Series 2 and Stage 3 (a suggested "Lenaldanian Series" and "Zhurinskyan Stage," new) GSSP base is proposed at the Siberian lower

  15. Small bilaterian fossils from 40 to 55 million years before the cambrian.

    PubMed

    Chen, Jun-Yuan; Bottjer, David J; Oliveri, Paola; Dornbos, Stephen Q; Gao, Feng; Ruffins, Seth; Chi, Huimei; Li, Chia-Wei; Davidson, Eric H

    2004-07-09

    Ten phosphatized specimens of a small (<180 micrometers) animal displaying clear bilaterian features have been recovered from the Doushantuo Formation, China, dating from 40 to 55 million years before the Cambrian. Seen in sections, this animal (Vernanimalcula guizhouena gen. et sp. nov.) had paired coeloms extending the length of the gut; paired external pits that could be sense organs; bilateral, anterior-posterior organization; a ventrally directed anterior mouth with thick walled pharynx; and a triploblastic structure. The structural complexity is that of an adult rather than a larval form. These fossils provide the first evidence confirming the phylogenetic inference that Bilateria arose well before the Cambrian.

  16. Unraveling the redox evolution of the Yangtze Block across the Precambrian/Cambrian transition

    NASA Astrophysics Data System (ADS)

    Diamond, C. W.; Zhang, F.; Chen, Y.; Lyons, T. W.

    2016-12-01

    Rocks preserved on the South China Craton have played a critical role in refining our understanding of the co-evolution of life and Earth's surface environments in the Late Neoproterozoic and earliest Paleozoic. From the earliest metazoan embryos to the many examples of exceptional preservation throughout the Cambrian Explosion, South China has preserved an outstanding record of animal evolution across this critical transition. Similarly, rocks preserved in South China hold key insights into the changing ocean chemistry that accompanied this extraordinary time. Recent work form Sahoo and others (2016, Geobiology) used redox sensitive metal enrichments in the Ediacaran Doushantuo Formation to demonstrate that the redox state of the Latest Neoproterozoic oceans was highly dynamic, rather than stably oxygenated or anoxic as had both been suggested previously. In an attempt to follow on from this and other studies, we have examined samples from a drill core taken in eastern Guizhou capturing deep-water facies of the Liuchapo and Jiumenchong formations, which contain the Precambrian/Cambrian boundary. In addition to containing the boundary, the sampled interval contains an enigmatic, widespread horizon that is strongly enriched in Ni and Mo. We have taken a multi-proxy approach in our investigation of this layer, the possible implications it has for the strata above and below (i.e., how its presence affects their utility as archives of paleo-redox conditions), and what those strata can tell us about local and global redox conditions during this pivotal time in Earth's history. Our Fe speciation data indicate that conditions were sulfidic at this location throughout the majority of the sampled interval. While redox sensitive metal concentrations are dramatically enriched in the Ni/Mo interval, their concentrations return to modest enrichments above it and continue to decrease upward. This trend suggests that while the conditions that favored extreme enrichment during the

  17. The 'Orsten': more than a Cambrian Konservat-Lagerstätte yielding exceptional preservation

    USGS Publications Warehouse

    Maas, Andreas; Braun, Andreas; Dong, Xi-Ping; Donoghue, Philip C.J.; Muller, Klaus J.; Olempska, Ewa; Repetski, John E.; Siveter, David J.; Stein, Martin; Waloszek, Dieter

    2006-01-01

    In several areas of southern Sweden, limestone nodules, locally called Orsten occur within bituminous alum shales. These shales and nodules were deposited under dysoxic conditions at the bottom of what was most likely a shallow sea during the late Middle to Upper Cambrian (ca. 500 million years ago). Subsequently, the name ‘Orsten’ has been referred to particular, mainly arthropod, fossils from such nodules, and, in a wider sense, to the specific type of preservation of minute fossil through secondarily phosphatization. This preservation is exceptional in yielding uncompacted and diagenetically undeformed three-dimensional fossils. ‘Orsten’-type preservation resulted from incrustation of a thin external layer and also by impregnation by calcium phosphate and, therefore, mineralization of the surface of the former animals during early diagenesis. Primarily, this type of preservation seems to have affected only cuticle-bearing metazoans such as cycloneuralian nemathelminths and arthropods. ‘Orsten’ preservation in this sense seems to be limited by size, in having yielded no partial or complete animals larger than 2 mm. On the other end of the scale, even larvae 100 μm long are preserved, often more complete than larger specimens, and details such as setules and pores smaller than 1 μm can be observed. Fossils preserved in such a manner are almost exclusively hollow carcasses, but can be filled secondarily; less common are completely phosphatized compact specimens. The high quality of preservation makes the Swedish ‘Orsten’ a typical Konservat-Lagerstätte. Yet, its special type of preservation is more widespread in time and geographical distribution than assumed initially, and the origin of the phosphate is not necessarily restricted just to one source. Subsequent to the first discoveries of limb fragments of Cambrian arthropods in 1975, animals in this special preservational type have been discovered in several continents and across a broad

  18. Review of the Cambrian volcanic activity in Morocco: geochemical fingerprints and geotectonic implications for the rifting of West Gondwana

    NASA Astrophysics Data System (ADS)

    Pouclet, André; El Hadi, Hassan; Álvaro, J. Javier; Bardintzeff, Jacques-Marie; Benharref, Mohammed; Fekkak, Abdelilah

    2018-03-01

    Volcanic activities related to the opening of a Cambrian rift in Morocco were widespread from the Fortunian to the Cambrian Epoch 3. Numerous data are available from northwestern volcanic sites, particularly in the western High Atlas, but they are scarce from the southeastern sites. New data are documented here from the volcanic formations exposed in the Jbel Tazoult n'Ouzina of the Tafilalt Province, eastern Anti-Atlas and dated to Cambrian Epoch 2-3. The Cambrian volcanic activities recorded in the High Atlas, Anti-Atlas, and Coastal Meseta are synthesized to refine their stratigraphic setting and to characterize their magmatic affinities and fingerprints. Six volcanic pulses are determined as tholeiitic, transitional, and alkaline suites. The tholeiitic and transitional magmas originated from primitive mantle and E-MORB-type sources with a spinel- and garnet-bearing lherzolite composition. Some of them were modified by assimilation-fractional crystallisation processes during crust-mantle interactions. The alkaline magmas fit with an OIB-type and a garnet-bearing lherzolite source. The palaeogeographic distribution of the magmatic suites was controlled by the lithospheric thinning of the Cambrian Atlas Rift and lithospheric constraints of the Pan-African metacraton and West African craton.

  19. Multiple High-Frequency Carbon Isotope Excursions Across the Precambrian-Cambrian Boundary: Implications for Correlations and Environmental Change

    NASA Astrophysics Data System (ADS)

    Smith, E. F.; Macdonald, F. A.; Schrag, D. P.; Laakso, T.

    2014-12-01

    The GSSP Precambrian-Cambrian boundary in Newfoundland is defined by the first appearance datum (FAD) of Treptichnus pedum, which is considered to be roughly coincident with the FAD of small shelly fossils (SSFs) and a large negative carbon isotope excursion. An association between the FAD of T. pedum and a negative carbon isotope excursion has previously been documented in Northwest Canada (Narbonne et al., 1994) and Death Valley (Corsetti and Hagadorn, 2000), and since then has been used as an chronostratigraphic marker of the boundary, particularly in siliciclastic poor sections that do not preserve T. pedum. Here we present new high-resolution carbon isotope (δ13C ) chemostratigraphy from multiple sections in western Mongolia and the western United States that span the Ediacaran-Cambrian transition. High-resolution sampling (0.2-1 m) reveals that instead of one large negative excursion, there are multiple, high-frequency negative excursions with an overall negative trend during the latest Ediacaran. These data help to more precisely calibrate changes in the carbon cycle across the boundary as well as to highlight the potential problem of identifying the boundary with just a few negative δ13C values. We then use a simple carbon isotope box model to explore relationships between phosphorous delivery to the ocean, oxygenation, alkalinity, and turnovers in carbonate secreting organisms. Corsetti, F.A., and Hagadorn, J.W., 2000, Precambrian-Cambrian transition: Death Valley, United States: Geology, v. 28, no. 4, p. 299-302. Narbonne, G.M., Kaufman, A.J., and Knoll, A.H., 1994, Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: Implications for Neoproterozoic correlations and the early evolution of animals: Geological Society of America Bulletin, v. 106, no. 10, p. 1281-1292.

  20. Paleomagnetism of a well-dated marine succession in South China: A possible Late Cambrian true polar wander (TPW)

    NASA Astrophysics Data System (ADS)

    Jiao, Wen-Jun; Li, Yong-Xiang; Yang, Zhen-Yu

    2018-04-01

    The Cambrian true polar wander (TPW) hypothesis remains controversial largely because of the uncertainties in the quality and/or fidelity of the paleomagnetic data as well as their chronological control. Testing the TPW hypothesis requires high-quality paleomagnetic data of sufficient spatial and temporal resolutions. Here, we present paleomagnetic results of a continuous Cambrian shallow marine succession from South China where available detailed biostratigraphy provides exceptional chronological constraints. Forty-three sites of paleomagnetic samples were collected from this limestone-dominated succession. Stepwise thermal demagnetization generally reveals three-component magnetizations. Low- and intermediate-temperature components can be cleaned by ∼330 °C, and the high-temperature component (HTC) was isolated typically from ∼350 to ∼450 °C. A positive fold test and the presence of reversed polarity in the strata, together with rock magnetic data as well as the scanning electron microscopic (SEM) and transmission electron microscopic (TEM) results, collectively suggest that the HTCs are likely primary. A directional shift of the HTCs occurs between the lower-middle Cambrian and the upper Cambrian strata in the succession and is tentatively interpreted to indicate a ∼57° polar wander from ∼500.5 to 494 Ma. Because the rate of polar wander is too fast to be a tectonic origin, this polar wander is interpreted to represent a Late Cambrian TPW. This TPW appears coeval with the Steptoean positive carbon isotope excursion (SPICE) and the major trilobite mass extinctions, suggesting a potential link between the TPW and the Late Cambrian biotic and climatic changes. Because the proposed TPW event is exceptionally well-dated, it should be testable through examination of other worldwide sections.

  1. Climatic-oceanic forcing on the organic accumulation across the shelf during the Early Cambrian (Age 2 through 3) in the mid-upper Yangtze Block, NE Guizhou, South China

    NASA Astrophysics Data System (ADS)

    Yeasmin, Rumana; Chen, Daizhao; Fu, Yong; Wang, Jianguo; Guo, Zenghui; Guo, Chuan

    2017-02-01

    The organic-rich sediments were widely deposited over the entire Yangtze Block during the Early Cambrian (late Nemakit-Daldynian to Botomian). In the mid-upper Yangtze region, northeastern Guizhou, South China, they comprise, in ascending order, the Niutitang, Jiumenchong and lower Bianmachong formations which are dominated by black shales except the middle one characterized by interbedded shales-limestones. Three third-order depositional sequences are identified in the two studied sections located on the upper slope to basin of the open shelf. The organic-rich sediments were mostly deposited notably during transgressions on the shallower upper slope-margin (TOC up to 25 wt.%) where they are characterized by co-increases in C, P, Fe, and Ba concentrations, indicating the highest organic productivity and coupled C, P and Fe cycling there. In contrast, in the shelf basin, the concomitant organic-rich sediments yield lower organic (TOC <10 wt.% mostly) and Ba abundances, and generally show antithetic relationship of TOC with P and Fe variations, indicative of a relatively low organic productivity and transient decoupled C, P and Fe cycling in the deeper basin. This spatial difference in C, P, Fe and Ba cycling as a whole thus indicate that the highest organic productivity wedge on the shallower shelf upper slope-margin was likely induced by the oceanic upwelling from the restricted basin where the P and Fe nutrients were transiently depleted without timely renewal. Meanwhile, multiple redox proxies, including V/Al, Ni/Al and Cr/Al ratios vs. TOC contents, together with V/(V + Ni) and V/Cr ratios, generally characterize a more severe euxinic water wedge localized on the shallower upper slope-margin of shelf where the organic production culminated, but a nonsulfidic (ferruginous) anoxic state in the basin due to the relatively low sulfate level. Meanwhile, episodic depletion of trace elements in the deeper basin during the higher organic productivity also reconciles the

  2. A new U-Pb LA-ICP-MS age of the Rumburk granite (Lausitz Block, Saxo-Thuringian Zone): constraints for a magmatic event in the Upper Cambrian

    NASA Astrophysics Data System (ADS)

    Zieger, J.; Linnemann, U.; Hofmann, M.; Gärtner, A.; Marko, L.; Gerdes, A.

    2018-04-01

    The basement of the Saxo-Thuringian Zone consists of Upper Neoproterozoic (c. 650-570 Ma) Cadomian arc sediments (Lusatian greywackes) and voluminous intrusions of Early Cambrian granitoids with ages of c. 540 Ma (Lausitz Block and Karkonosze-Izera Massif). The latter basement complexes comprise several c. 505 Ma granites, granodiorites, and gneisses emplaced during the change from a collisional tectonic setting to rift-related geotectonics. We present a new age for the Rumburk granite of 504 ± 3 Ma linking Late Cambrian plutonism at the northern margin of Gondwana with the initial phase of a Cambro-Ordovician rift event. Trace element analysis points to a linkage of the Rumburk granite with other Late Cambrian aged rocks of the Karkonosze-Izera Massif. Furthermore, geochemical data also provide evidence of a melting and recycling of Lusatian greywackes by the intrusion of the Rumburk granite. The youngest age peak of the Rumburk granite at c. 504 Ma is considered to be the age of emplacement. Older inherited age populations at c. 540 and c. 610 Ma are present and likely the result of a melting and recycling of Lusatian granitoids and greywackes. The appearance of Neoproterozoic inheritance and Lu-Hf similarities with the Rumburk granite strongly suggest the Lusatian greywackes as source rocks. There is a significant age gap of c. 35 Ma between Cambrian plutonic and volcanic rocks in Saxo-Thuringia. Hence, we consider two distinct pulses of magmatic activity during the transition from the Cadomian orogeny to the opening of the Rheic Ocean.

  3. Facies analysis of Late Proterozoic through Lower Cambrian rocks of the Death Valley regional ground-water system and surrounding areas, Nevada and California

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sweetkind, D.S.; White, D.K.

    Late Proterozoic through Lower Cambrian rocks in the southern Great Basin form a westward-thickening wedge of predominantly clastic deposits that record deposition on the early western shelf edge of western North America (Stewart and Poole, 1974; Poole and others, 1992). Regional analyses of geologic controls on ground-water flow in the southern Great Basin typically combined lithostratigraphic units into more general hydrogeologic units that have considerable lateral extent and distinct hydrologic properties. The Late Proterozoic through Lower Cambrian rocks have been treated as a single hydrogeologic unit, named the lower clastic aquitard (Winograd and Thordarson, 1975) or the quartzite confining unitmore » (Laczniak and others, 1996), that serves as the hydrologic basement to the flow system. Although accurate in a general sense, this classification ignores well-established facies relations within these rocks that might increase bedrock permeability and locally influence ground-water flow . This report presents a facies analysis of Late Proterozoic through Lower Cambrian rocks (hereafter called the study interval) in the Death Valley regional ground-water flow system - that portion of the southern Great Basin that includes Death Valley, the Nevada Test Site, and the potential high-level nuclear waste underground repository at Yucca Mountain (fig. 1). The region discussed in this report, hereafter called the study area, covers approximately 100,000 km2 (lat 35 degrees-38 degrees 15'N., long 115 degrees-118 degrees W.). The purpose of this analysis is to provide a general documentation of facies transitions within the Late Proterozoic through Lower Cambrian rocks in order to provide an estimate of material properties (via rock type, grain size, and bedding characteristics) for specific hydrogeologic units to be included in a regional ground-water flow model.« less

  4. Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico

    USGS Publications Warehouse

    Gehrels, G.E.; Stewart, John H.

    1998-01-01

    One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40-1.45 and 1.62-1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225-280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the

  5. Selenium and hazardous elements distribution in plant-soil-water system and human health risk assessment of Lower Cambrian, Southern Shaanxi, China.

    PubMed

    Du, Yajun; Luo, Kunli; Ni, Runxiang; Hussain, Rahib

    2018-03-01

    The natural selenium poisoning due to toxic Se levels in food chain had been observed in humans and animals in Lower Cambrian outcrop areas in Southern Shaanxi, China. To find out the distribution pattern of selenium and other hazardous elements in the plant, soil and water of Lower Cambrian in Southern Shaanxi, China, and their possible potential health risk, a total of 30 elements were analyzed and the health risk assessment of 18 elements was calculated. Results showed that the soil, plant and natural water of Lower Cambrian all had relatively high Se levels. In Lower Cambrian, the soil was enriched with Se, As, Ba, Cu, Mo, Ni, Zn, Ga, Cd and Cr (1.68 < I geo  < 4.48, I geo ; geo-accumulation index). In same plants, the contents of Se, Cd and Zn (except Cd in corn and rice, Zn in potato and corn) of Lower Cambrian were higher than that of the other strata. Ba and Ga in natural water were higher than that of the other strata, while K and Cs were opposite. The health risk assessment results showed that the people living in outcrop areas of Lower Cambrian had both high total non-carcinogenic risk of 18 elements (HI = 16.12, acceptable range: < 1) and carcinogenic risk of As (3.98E-04, acceptable range: 10 -6 -10 -4 ). High contents of Se, As, Mo and Tl of Lower Cambrian may pose a health risk to local people, and food intake was the major pathway. For minimizing potential health risk, the local inhabitants should use the mix-imported food with local growing foods.

  6. Provenance of north Gondwana Cambrian-Ordovician sandstone: U-Pb SHRIMP dating of detrital zircons from Israel and Jordan

    USGS Publications Warehouse

    Kolodner, K.; Avigad, D.; McWilliams, M.; Wooden, J.L.; Weissbrod, T.; Feinstein, S.

    2006-01-01

    A vast sequence of quartz-rich sandstone was deposited over North Africa and Arabia during Early Palaeozoic times, in the aftermath of Neoproterozoic Pan-African orogeny and the amalgamation of Gondwana. This rock sequence forms a relatively thin sheet (1-3 km thick) that was transported over a very gentle slope and deposited over a huge area. The sense of transport indicates unroofing of Gondwana terranes but the exact provenance of the siliciclastic deposit remains unclear. Detrital zircons from Cambrian arkoses that immediately overlie the Neoproterozoic Arabian-Nubian Shield in Israel and Jordan yielded Neoproterozoic U-Pb ages (900-530 Ma), suggesting derivation from a proximal source such as the Arabian-Nubian Shield. A minor fraction of earliest Neoproterozoic and older age zircons was also detected. Upward in the section, the proportion of old zircons increases and reaches a maximum (40%) in the Ordovician strata of Jordan. The major earliest Neoproterozoic and older age groups detected are 0.95-1.1, 1.8-1.9 and 2.65-2.7 Ga, among which the 0.95-1.1 Ga group is ubiquitous and makes up as much as 27% in the Ordovician of Jordan, indicating it is a prominent component of the detrital zircon age spectra of northeast Gondwana. The pattern of zircon ages obtained in the present work reflects progressive blanketing of the northern Arabian-Nubian Shield by Cambrian-Ordovician sediments and an increasing contribution from a more distal source, possibly south of the Arabian-Nubian Shield. The significant changes in the zircon age signal reflect many hundreds of kilometres of southward migration of the provenance. ?? 2006 Cambridge University Press.

  7. Morphology and ultrastructure of epilithic versus cryptic, microbial growth in lower Cambrian phosphorites from the Montagne Noire, France.

    PubMed

    Alvaro, J J; Clausen, S

    2010-03-01

    The lower Cambrian grainy phosphorites of the northern Montagne Noire occur interbedded with grey to black, laminated to massive shales and limestones deposited along the edge of a continental shelf, associated with slope-related facies and unstable substrates. The concentration of phosphate took place by repeated alternations of low sedimentation rates and condensation (hardgrounds), in situ early-diagenetic precipitation of fluorapatite, winnowing and polyphase reworking of previously phosphatized skeletons and hardground-derived clasts. The succession of repeated cycles of sedimentation, phosphate concentration, and reworking led to multi-event phosphate deposits rich in allochthonous particles. Phosphogenesis was primarily mediated by microbial activity, which is evidenced by the abundance of phosphatized putative microbial remains. These occur as smooth and segmented filaments, sheaths, and ovoid-shaped coccoids. These simple morphologies commonly form composite frameworks as a result of their aggregation and entanglement, leading to the record of biofilms, microbial mats, and complex networks. These infested the calcitic skeletonized microfossils that littered the substrate. Microbial activity evidences epilithic (anisotropic coatings on skeletons), euendolithic (perforating skeletal walls), and cryptoendolithic (lining inter- and intraparticulate pores) strategies, the latter dominated by bundles of filaments and globular clusters that grew along the cavities of helcionellids and hyoliths. According to their epilithic versus cryptic strategies, microbial populations that penetrated and dwelled inside hard skeletal substrates show different network and colonial morphologies. These early Cambrian shell concentrations were the loci of a stepwise colonization made by saprophytic to mutualistic, cyanobacterial-fungal consortia. Their euendolithic and cryptoendolithic ecological niches provided microbial refugia to manage the grazing impact mainly led by metazoans.

  8. Self-recognition and Ca2+-dependent carbohydrate-carbohydrate cell adhesion provide clues to the cambrian explosion.

    PubMed

    Fernàndez-Busquets, Xavier; Körnig, André; Bucior, Iwona; Burger, Max M; Anselmetti, Dario

    2009-11-01

    The Cambrian explosion of life was a relatively short period approximately 540 Ma that marked a generalized acceleration in the evolution of most animal phyla, but the trigger of this key biological event remains elusive. Sponges are the oldest extant Precambrian metazoan phylum and thus a valid model to study factors that could have unleashed the rise of multicellular animals. One such factor is the advent of self-/non-self-recognition systems, which would be evolutionarily beneficial to organisms to prevent germ-cell parasitism or the introduction of deleterious mutations resulting from fusion with genetically different individuals. However, the molecules responsible for allorecognition probably evolved gradually before the Cambrian period, and some other (external) factor remains to be identified as the missing triggering event. Sponge cells associate through calcium-dependent, multivalent carbohydrate-carbohydrate interactions of the g200 glycan found on extracellular proteoglycans. Single molecule force spectroscopy analysis of g200-g200 binding indicates that calcium affects the lifetime (+Ca/-Ca: 680 s/3 s) and bond reaction length (+Ca/-Ca: 3.47 A/2.27 A). Calculation of mean g200 dissociation times in low and high calcium within the theoretical framework of a cooperative binding model indicates the nonlinear and divergent characteristics leading to either disaggregated cells or stable multicellular assemblies, respectively. This fundamental phenomenon can explain a switch from weak to strong adhesion between primitive metazoan cells caused by the well-documented rise in ocean calcium levels at the end of Precambrian time. We propose that stronger cell adhesion allowed the integrity of genetically uniform animals composed only of "self" cells, facilitating genetic constitutions to remain within the metazoan individual and be passed down inheritance lines. The Cambrian explosion might have been triggered by the coincidence in time of primitive animals

  9. Body Size Evolution in Conodonts from the Cambrian through the Triassic

    NASA Astrophysics Data System (ADS)

    Schaal, E. K.; Morgan, D. J.; Payne, J.

    2013-12-01

    The size of an organism exercises tremendous control over its physiology, life history, and ecology, yet the factors that influence body size evolution remain poorly understood. One major limitation is the lack of appropriate datasets spanning long intervals of evolutionary time. Here, we document size trends in conodonts (tooth-like microfossils from marine chordates) because they evolved rapidly and are known to change size during intervals of environmental change. By measuring photographs from the Catalogue of Conodonts (Ziegler 1982), we compiled a database of conodont P1 element measurements for 575 species and subspecies from the Cambrian through Triassic periods. Because tooth size correlates with body size in conodont animals and their extant relatives, conodont element length can serve as a proxy for the size of the conodont animal. We find that mean and maximum size across species increased during the early Paleozoic, peaked during the Devonian-Mississippian, and then generally decreased until conodonts went extinct at the end of the Triassic. We used regression analyses to compare conodont mean size trends to potential environmental predictors, such as changing atmospheric pO2, atmospheric pCO2, and sea level. Conodont size exhibited poor correlation with these environmental factors, suggesting that conodont evolution may have been more strongly influenced by other environmental covariates or ecological variables such as predation and competition.

  10. High Resolution Biostratigraphy and the Origin of the Basal Cambrian Bedded Chert from the Aksu Area (Tarim Block, Northwestern China)

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Liu, H.; Dong, L.

    2017-12-01

    The early Cambrian Yurtus Formation in the Aksu area (Tarim block, northwestern China) consists of two lithostratigraphic units, lower black shale with interbedded chert unit and upper siltstone/carbonate unit. This time period represents the most important Proterozoic- Phanerozoic transition in earth's history. In recent years, the black shale has been confirmed to have high hydrocarbon generation potential. However, the depositional environment of the Yurtus Formation remains controversial and the biostratigraphic constrains are rather poor. The chert that is interbedded with black shale in the Yurtus Formation provides an exceptional taphonomic window to capture the diversity of the early Cambrian microfossils. Meanwhile, the origin of the bedded chert would give us some insight into the environmental background when the source rock was deposited. Therefore, in this research, we focus on the chert in the lower Yurtus formation and our purpose is to establish high resolution biostratigraphic framework and to better understand the depositional environment of the source rock. We investigated 4 sections in the Tarim basin: Kungaikuotan, Sugaite, Kule, and Yurtus VI. Abundant acritarch fossils have been identified, including Heliosphaeridium ampliatum, Yurtusia uniformis, and Comasphaeridium annulare. The tubular fossil Megathrix longus is also very common in this formation. In addition, two new types of specimens have been discovered, sheet-like encrolled fossils ( 0.5 mm in size) and regular spindle-like double layered microfossils ( 10μm in diameter). All of these fossils have constant occurrences in the studied sections, and can be well correlated with those yielded from the equivalent interval in South China. The biostratigraphic work suggests the source rock in the lower unit of the Yurtus Formation could be correlated with the Meishucunian small shelly fossil assemblage I and II. The Gemenium/Silicon ratio of the Yurtus chert is less than 1

  11. Controls on Gut Phosphatisation: The Trilobites from the Weeks Formation Lagerstätte (Cambrian; Utah)

    PubMed Central

    Lerosey-Aubril, Rudy; Hegna, Thomas A.; Kier, Carlo; Bonino, Enrico; Habersetzer, Jörg; Carré, Matthieu

    2012-01-01

    Despite being internal organs, digestive structures are frequently preserved in Cambrian Lagerstätten. However, the reasons for their fossilisation and their biological implications remain to be thoroughly explored. This is particularly true with arthropods – typically the most diverse fossilised organisms in Cambrian ecosystems – where digestive structures represent an as-yet underexploited alternative to appendage morphology for inferences on their biology. Here we describe the phosphatised digestive structures of three trilobite species from the Cambrian Weeks Formation Lagerstätte (Utah). Their exquisite, three-dimensional preservation reveals unique details on trilobite internal anatomy, such as the position of the mouth and the absence of a differentiated crop. In addition, the presence of paired pygidial organs of an unknown function is reported for the first time. This exceptional material enables exploration of the relationships between gut phosphatisation and the biology of organisms. Indeed, soft-tissue preservation is unusual in these fossils as it is restricted to the digestive structures, which indicates that the gut played a central role in its own phosphatisation. We hypothesize that the gut provided a microenvironment where special conditions could develop and harboured a source of phosphorus. The fact that gut phosphatization has almost exclusively been observed in arthropods could be explained by their uncommon ability to store ions (including phosphorous) in their digestive tissues. However, in some specimens from the Weeks Formation, the phosphatisation extends to the entire digestive system, suggesting that trilobites might have had some biological particularities not observed in modern arthropods. We speculate that one of them might have been an increased capacity for ion storage in the gut tissues, related to the moulting of their heavily-mineralised carapace. PMID:22431989

  12. Paragenesis of the Morgan Creek Limestone, Late Cambrian, central Texas: Constraints on the formation of glauconite

    NASA Astrophysics Data System (ADS)

    Chafetz, Henry S.

    2007-06-01

    Deposition of the Morgan Creek Limestone, a member of the Cambrian Wilberns Formation, began a few meters above a disconformable surface and displays abundant indicators of accumulation in shallow marine to tidal flat environments. These indicators include: intercalation of a lithologic variety of thin beds (e.g. biosparites, biomicrites, oosparites, intrasparites), which display rapid vertical and lateral lithologic changes, numerous stromatolitic horizons, channels filled with graded oosparites and intrasparites that cut through micrite accumulations, and finely laminated (non-burrowed) siltstones. Glauconite is a ubiquitous minor constituent throughout in the form of pellets, replaced skeletal material and mica books, and, most informatively, as an authigenic precipitate in the form of fibroradiating rims on carbonate allochems and siliciclastic grains. Fibroradiating glauconite rims were disrupted and pushed away from the pelmatozoan nuclei on which they precipitated. Combined sedimentological and paragenetic constraints indicate that the glauconite was the earliest diagenetic event to affect these sediments and occurred essentially at the sediment-water interface within these relatively high-energy, shallow marine deposits. Precipitation of glauconite was closely followed by precipitation of carbonate cement as well as dissolution of aragonitic constituents. Later diagenetic processes included selective dolomitization and silicification. In modern seas glauconite is reported to form at and below mid-shelf water depths. Thus, the constraints pertaining to the origin of modern glauconite are not valid for Late Cambrian deposits and probably are also not applicable for Late Cretaceous through Early Paleogene glauconites.

  13. Cambrian Sauk transgression in the Grand Canyon region redefined by detrital zircons

    NASA Astrophysics Data System (ADS)

    Karlstrom, Karl; Hagadorn, James; Gehrels, George; Matthews, William; Schmitz, Mark; Madronich, Lauren; Mulder, Jacob; Pecha, Mark; Giesler, Dominique; Crossey, Laura

    2018-06-01

    The Sauk transgression was one of the most dramatic global marine transgressions in Earth history. It is recorded by deposition of predominantly Cambrian non-marine to shallow marine sheet sandstones unconformably above basement rocks far into the interiors of many continents. Here we use dating of detrital zircons sampled from above and below the Great Unconformity in the Grand Canyon region to bracket the timing of the Sauk transgression at this classic location. We find that the Sixtymile Formation, long considered a Precambrian unit beneath the Great Unconformity, has maximum depositional ages that get younger up-section from 527 to 509 million years old. The unit contains angular unconformities and soft-sediment deformation that record a previously unknown period of intracratonic faulting and epeirogeny spanning four Cambrian stages. The overlying Tapeats Sandstone has youngest detrital zircon ages of 505 to 501 million years old. When linked to calibrated trilobite zone ages of greater than 500 million years old, these age constraints show that the marine transgression across a greater than 300-km-wide cratonic region took place during an interval 505 to 500 million years ago—more recently and more rapidly than previously thought. We redefine this onlap as the main Sauk transgression in the region. Mechanisms for this rapid flooding of the continent include thermal subsidence following the final breakup of Rodinia, combined with abrupt global eustatic changes driven by climate and/or mantle buoyancy modifications.

  14. Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus

    NASA Astrophysics Data System (ADS)

    Sansom, Robert S.

    2016-09-01

    The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them.

  15. Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus

    PubMed Central

    Sansom, Robert S.

    2016-01-01

    The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them. PMID:27595908

  16. Paleoarchean and Cambrian observations of the geodynamo in light of new estimates of core thermal conductivity

    NASA Astrophysics Data System (ADS)

    Tarduno, John; Bono, Richard; Cottrell, Rory

    2015-04-01

    Recent estimates of core thermal conductivity are larger than prior values by a factor of approximately three. These new estimates suggest that the inner core is a relatively young feature, perhaps as young as 500 million years old, and that the core-mantle heat flux required to drive the early dynamo was greater than previously assumed (Nimmo, 2015). Here, we focus on paleomagnetic studies of two key time intervals important for understanding core evolution in light of the revisions of core conductivity values. 1. Hadean to Paleoarchean (4.4-3.4 Ga). Single silicate crystal paleointensity analyses suggest a relatively strong magnetic field at 3.4-3.45 Ga (Tarduno et al., 2010). Paleointenity data from zircons of the Jack Hills (Western Australia) further suggest the presence of a geodynamo between 3.5 and 3.6 Ga (Tarduno and Cottrell, 2014). We will discuss our efforts to test for the absence/presence of the geodynamo in older Eoarchean and Hadean times. 2. Ediacaran to Early Cambrian (~635-530 Ma). Disparate directions seen in some paleomagnetic studies from this time interval have been interpreted as recording inertial interchange true polar wander (IITPW). Recent single silicate paleomagnetic analyses fail to find evidence for IITPW; instead a reversing field overprinted by secondary magnetizations is defined (Bono and Tarduno, 2015). Preliminary analyses suggest the field may have been unusually weak. We will discuss our on-going tests of the hypothesis that this interval represents the time of onset of inner core growth. References: Bono, R.K. & Tarduno, J.A., Geology, in press (2015); Nimmo, F., Treatise Geophys., in press (2015); Tarduno, J.A., et al., Science (2010); Tarduno, J.A. & Cottrell, R.D., AGU Fall Meeting (2014).

  17. A Vendian-Cambrian boundary succession from the northwestern margin of the Siberian Platform: stratigraphy, palaeontology, chemostratigraphy and correlation

    NASA Technical Reports Server (NTRS)

    Bartley, J. K.; Pope, M.; Knoll, A. H.; Semikhatov, M. A.; Grotzinger, J. (Principal Investigator)

    1998-01-01

    Siberia contains several key reference sections for studies of biological and environmental evolution across the Proterozoic-Phanerozoic transition. The Platonovskaya Formation, exposed in the Turukhansk region of western Siberia, is an uppermost Proterozoic to Cambrian succession whose trace and body fossils place broad limits on the age of deposition, but do not permit detailed correlation with boundary successions elsewhere. In contrast, a striking negative carbon isotopic excursion in the lower part of the Platonovskaya Formation permits precise chemostratigraphic correlation with upper-most Yudomian successions in Siberia, and possibly worldwide. In addition to providing a tool for correlation, the isotopic excursion preserved in the Platonovskaya and contemporaneous successions documents a major biogeochemical event, likely involving the world ocean. The excursion coincides with the palaeontological breakpoint between Ediacaran- and Cambrian-style assemblages, suggesting a role for biogeochemical change in evolutionary events near the Proterozoic Cambrian boundary.

  18. A Vendian-Cambrian boundary succession from the northwestern margin of the Siberian Platform: stratigraphy, palaeontology, chemostratigraphy and correlation.

    PubMed

    Bartley, J K; Pope, M; Knoll, A H; Semikhatov, M A; Petrov PYu

    1998-07-01

    Siberia contains several key reference sections for studies of biological and environmental evolution across the Proterozoic-Phanerozoic transition. The Platonovskaya Formation, exposed in the Turukhansk region of western Siberia, is an uppermost Proterozoic to Cambrian succession whose trace and body fossils place broad limits on the age of deposition, but do not permit detailed correlation with boundary successions elsewhere. In contrast, a striking negative carbon isotopic excursion in the lower part of the Platonovskaya Formation permits precise chemostratigraphic correlation with upper-most Yudomian successions in Siberia, and possibly worldwide. In addition to providing a tool for correlation, the isotopic excursion preserved in the Platonovskaya and contemporaneous successions documents a major biogeochemical event, likely involving the world ocean. The excursion coincides with the palaeontological breakpoint between Ediacaran- and Cambrian-style assemblages, suggesting a role for biogeochemical change in evolutionary events near the Proterozoic Cambrian boundary.

  19. Cambrian archaeocyathan metazoans: revision of morphological characters and standardization of genus descriptions to establish an online identification tool.

    PubMed Central

    Kerner, Adeline; Debrenne, Françoise; Vignes-Lebbe, Régine

    2011-01-01

    Abstract Archaeocyatha represent the oldest calcified sponges and the first metazoans to build bioconstructions in association with calcimicrobes. They are a key group in biology, evolutionary studies, biostratigraphy, paleoecology and paleogeography of the early Cambrian times. The establishing of a new standardized terminology for archaeocyathans description has permitted the creation of the first knowledge base in English including descriptions of all archaeocyathan genera. This base, using the XPER² software package, is an integral part of the -Archaeocyatha- a knowledge base website, freely available at url http://www.infosyslab.fr/archaeocyatha. The website is composed of common information about Archaeocyatha, general remarks about the knowledge base, the description of the 307 genera recognized with images of type-specimens of type-species for each genus, as well as additional morphological data, an interactive free access key and its user guide. The automatic analysis and comparison of the digitized descriptions have identified some genera with highly similar morphology. These results are a great help for future taxonomic revisions and suggest a number of possible synonymies that require further study. PMID:22207818

  20. Magnetic reversal frequency in the Lower Cambrian Niutitang Formation, Hunan Province, South China

    NASA Astrophysics Data System (ADS)

    Duan, Zongqi; Liu, Qingsong; Ren, Shoumai; Li, Lihui; Deng, Xiaolong; Liu, Jianxing

    2018-05-01

    The reversal frequency of the paleomagnetic field bears great information of evolution of the Earth's deep interior. However, there are still debates on the frequency pattern during the older periods of the Phanerozoic. This study investigated the Niutitang Formation (Lower Cambrian) of the Ciye 1 Hole from south China. Rock magnetic results indicate that the dominant magnetic carrier is magnetite. Characteristic remanence magnetizations have been successfully isolated for the weakly-magnetized shale rocks through stepwise alternated field demagnetization using the 2 G Enterprises Rapid System Magnetometer with a low-noise thin-walled quartz-glass sample holder. Constrained by radiometric ages, our paleomagnetic results indicated frequent polarity reversals during the period of ˜524-514 Ma, which backs up the speculation about the episode of the Ediacaran-Cambrian (˜550-500 Ma) with a character of reversal hyperactivity.

  1. Groundwater quality in the Cambrian-Ordovician aquifer system, midwestern United States

    USGS Publications Warehouse

    Stackelberg, Paul E.

    2017-12-07

    Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Cambrian-Ordovician aquifer system constitutes one of the important areas being evaluated.

  2. Precambrian Continent Arctida: A New Kinematic Reconstruction of Late Precambrian - Early Paleozoic Arctida U Europe (baltia) Collision

    NASA Astrophysics Data System (ADS)

    Borisova, T. P.; Guertseva, M. V.; Egorov, A. Ju.; Kononov, M. V.; Kouznetsov, N. B.

    In according to L.P.Zonenshain and L.M.Natapov (1988, 1990), different size conti- nental blocks locating at the margins and inside of present-day Arctic ocean composed the hypothetical early Paleozoic paleocontinent Arctida. The blocks are Kara block (north part of Taymir peninsula, Severnaja Zemlja archipelago and Franz Joseph Land archipelago), north part of Alaska (northward Bruks ridge), Chukchi block, Novosi- birsky block (Novosibirskiye islands together their shelves), several fragments north- ward to the Innuitian orogen (north parts of Peary Land and Ellesmere Island), and Lomonosov ridgeSs block. In the previous kinematic reconstruction it was believed that Arctida as a whole collided with north flanks of Laurentia (Innuitian margin) and Europe (Baltia, Barentsia margin) in middle Paleozoic time. Later, the Arctida (been a fragment of supercontinent Pangea) was fragmented due to a spreading in the Arctic ocean and north part of Atlantic ocean in late Mesozoic and Cenozoic times. Then ArctidaSs fragments were accreted to the Eurasia and North America conti- nents. During the last decade "AEROGEOLOGIA" company has been gathered new data (geologic, stratigraphical, paleomagnetic, and others) of Russian Arctic sector and Svalbard. The data were summarized into "Paleogeographical Atlas for the Rus- sian Arctic sector and Svalbard from Vendian to Jurassic times" (see Abstact SE1.04, ID-NR: EGS02-A-02453). An analyzing of the maps for Vend and Cambrian times allows us to reconsider a few stages of kinematic scenario of late Precambrian - early Paleozoic Arctida U Europe collision. 1) Old interpretation: Arctida was considered as an isolated paleocontinent during early Paleozoic time. New interpretation: during the early Paleozoic Arctida together Europe (Baltia) were assembled into a paleo- continent named us Arcteurope. This conclusion is based on excellent coincidence of Paleozoic paleomagnetic poles of the Kara block (which is a part of Arctida) and Europe

  3. A New Stalked Filter-Feeder from the Middle Cambrian Burgess Shale, British Columbia, Canada

    PubMed Central

    O'Brien, Lorna J.; Caron, Jean-Bernard

    2012-01-01

    Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation) of Mount Stephen (Yoho National Park, British Columbia). With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality. This stalked animal (reaching at least 20 cm in length), has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb-like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-situ by rapid mud flow events. Siphusauctum gregarium resembles Dinomischus, another Cambrian enigmatic stalked animal. Principal points of comparison include a long stem with a calyx containing a visceral mass and bract-like elements, and a similar lifestyle albeit occupying different tiering levels. The presence in both animals of a digestive tract with a potential stomach and anus suggest a grade of organization within bilaterians, but relationships with extant phyla are not straightforward. Thus, the broader affinities of S. gregarium remain largely unconstrained

  4. Upper Neoproterozoic-Lower Cambrian sedimentary successions in the Central Iberian Zone (Spain): sequence stratigraphy, petrology and chemostratigraphy. Implications for other European zones

    NASA Astrophysics Data System (ADS)

    Valladares, M. I.; Barba, P.; Ugidos, J. M.; Colmenero, J. R.; Armenteros, I.

    The Upper Neoproterozoic-Lower Cambrian sedimentary succession in the central areas of the Central Iberian Zone has been subdivided into 12 mostly siliciclastic lithostratigraphic units, ranging in thickness between 1800 and 3900m. The lithology and facies of each unit are described and the facies associations are interpreted. The facies resulted mainly from turbidity currents and debris flows and, to a lesser extent, from submarine slides and traction flows. The facies associations suggest that sedimentation took place in slope and base-of-slope environments. Two depositional sequences are recognized, separated by a type-1 unconformity. The lower sequence is of Late Neoproterozoic age (units I-IV) and exhibits lowstand, transgressive, and highstand systems tracts. Most of the upper sequence is probably of Early Cambrian age (units V-XII). It begins at the base of unit V and possibly ends with the Tamames Limestone Formation. The upper sequence records a lowstand systems tract and minor-order sea-level oscillations. In the Cambrian units there are higher amounts of feldspar and smaller quantities of intrabasinal clasts than in the Neoproterozoic units. The modal data plot close to the Q-L and Qm-Lt sides of Q-F-L and Qm-F-Lt triangular diagrams, suggesting a provenance from a recycled orogen evolving into a provenance from a craton interior towards the top of the succession. The chemical results, based mainly on Al2O3, TiO2, Zr, and Nb abundances in shales from all the units, strongly suggest a gradual compositional change within this sedimentary succession. Together with the petrological data, the chemical results do not reveal any obvious coeval volcanic contribution to the sediments. On the basis of the chemical data, a comparison is made with other European zones containing detrital sediments composed of reworked crustal components.

  5. Phosphate Biomineralization of Cambrian Microorganisms

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Rozanov, Alexei Yu.; Hoover, Richard B.; Westall, Frances

    1998-01-01

    As part of a long term study of biological markers (biomarkers), we are documenting a variety of features which reflect the previous presence of living organisms. As we study meteorites and samples returned from Mars, our main clue to recognizing possible microbial material may be the presence of biomarkers rather than the organisms themselves. One class of biomarkers consists of biominerals which have either been precipitated directly by microorganisms, or whose precipitation has been influenced by the organisms. Such microbe-mediated mineral formation may include important clues to the size, shape, and environment of the microorganisms. The process of fossilization or mineralization can cause major changes in morphologies and textures of the original organisms. The study of fossilized terrestrial organisms can help provide insight into the interpretation of mineral biomarkers. This paper describes the results of investigations of microfossils in Cambrian phosphate-rich rocks (phosphorites) that were found in Khubsugul, Northern Mongolia.

  6. Nd-Sr isotopic and geochemical systematics in Cambrian boninites and tholeiites from Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Nelson, D. R.; Crawford, A. J.; McCulloch, M. T.

    1984-11-01

    Rocks with boninitic affinities have been recognised in a number of “ophiolites”, including the Cambrian Heathcote and Mt Wellington Greenstone Belts of Victoria. Boninites and high-Mg andesites from the Heathcote Greenstone Belt show a restricted range of initial ɛ Nd values of between +3.3 to +5.8. Extremely refractory boninites from the Mt Wellington Greenstone Belt have ɛ Nd ranging from +1.3 to -9. Ti/Zr is positively correlated with Sm/Nd with the Heathcote lavas generally possessing greater depletion of Ti and enrichment of Zr relative to the middle and heavy REE with increasing LREE/HREE. These data are consistent with the generation of boninites by partial melting of refractory peridotite following invasion by LREE- and Zr-enriched, low ɛ Nd fluids. Tholeiites overlying the boninites in both greenstone belts have flat REE patterns and ɛ Nd˜+5, lower than that anticipated for lavas derived from depleted MORB source reservoirs in the Cambrian, suggesting that their source was also contaminated by a LREE-enriched, low ɛ Nd component similar to that involved in the generation of the Howqua boninites. The added components have characteristics compatible with their derivation from subducted altered oceanic crust and/or from wet subducted sediments. The identification of boninites and other low-Ti lavas in the Victorian greenstone belts is strong evidence for island arc development in southeastern Australia during the Lower Cambrian and provides further support for a subduction-related origin for many ophiolites.

  7. Cambrian cinctan echinoderms shed light on feeding in the ancestral deuterostome

    PubMed Central

    Rahman, Imran A.; Zamora, Samuel; Falkingham, Peter L.; Phillips, Jeremy C.

    2015-01-01

    Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have enhanced the transport of suspended particles to the mouth. This strongly suggests that cinctans were active pharyngeal filter feeders, like modern enteropneust hemichordates and urochordates, indicating that the ancestral deuterostome employed a similar feeding strategy. PMID:26511049

  8. Les marqueurs structuraux et magmatiques de l'extension crustale au Protérozoïque terminal-Cambrien basal autour du massif de Kerdous (Anti-Atlas occidental, Maroc)

    NASA Astrophysics Data System (ADS)

    Soulaimani, Abderrahmane; Essaifi, Abderrahim; Youbi, Nassrddine; Hafid, Ahmid

    2004-12-01

    During the Late Precambrian-Early Cambrian times, the borders of the Kerdous inlier were affected by normal faults where thick conglomerates (Ouarzazate Group: PIII), grading progressively upwards into Cambrian marine sediments, were accumulated along their hanging walls. This tectonic activity persisted during the Early Cambrian and was accompanied by a magmatic activity resulting mainly in the emplacement of continental tholeiitic basalts. These tectono-sedimentary and magmatic events are related to the crustal extensional episode that affected the northwestern Gondwana margin during the opening of the Iapetus Ocean during Late Proterozoic times. To cite this article: A. Soulaimani et al., C. R. Geoscience 336 (2004).

  9. Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes.

    PubMed

    Caron, Jean-Bernard; Conway Morris, Simon; Shu, Degan

    2010-03-08

    Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles.

  10. 500 Myr of thermal history elucidated by multi-method detrital thermochronology of North Gondwana Cambrian sandstone (Eilat area, Israel)

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.; Avigad, D.

    2009-04-01

    Following the Neoproterozoic Pan-African orogeny, the Arabian-Nubian Shield (ANS) of North Africa and Arabia was eroded and then covered by Cambrian sandstones that record the onset of platform sedimentation. We applied K-feldspar 40Ar/39Ar, zircon and apatite fission track and apatite (U-Th)/He thermochronology to detritus from Cambrian sandstones of southern Israel deposited at about 500 Ma. U-Pb detrital zircon ages from these sandstones predate deposition and record the earlier Neoproterozoic crustal evolution of the Pan-African orogens. 40Ar/39Ar ages from 50 single grains of K-feldspar yield a Cambrian mean of approximately 535 Ma. The 40Ar/39Ar age spectrum of a multi-grain K-feldspar aliquot displays diffusion behaviour compatible with >560 Ma cooling later affected by a heating event. Assuming that the high temperature domains of the K-feldspars have not been affected by subsequent (hydro)thermal events, and taking previously published K-Ar and Rb-Sr ages from other parts of the East African Orogen at face value, these ages apparently record Pan-African thermal resetting below a thick volcano-sedimentary pile similar to the Saramuj conglomerate in Jordan and/or the Hammamat in Egypt. Detrital zircon fission track (ZFT) ages cluster around 380 Ma, consistent with previous ZFT results from Neoproterozoic basement and sediments of the region, revealing that the Cambrian platform sequence experienced a middle Devonian thermal event and low-grade metamorphism. Regional correlation indicates that during Devonian time the sedimentary cover atop the Cambrian in Israel was never in excess of 2.5 km, requiring an abnormally steep geothermal gradient to explain the complete ZFT annealing. A basal Carboniferous unconformity can be traced from Syria to southern Saudi Arabia, suggesting that the observed Devonian ZFT ages represent a regional tectonothermal event. Similar Devonian ZFT ages were reported from ANS basement outcrops in the Eastern Desert, 500 km south of

  11. Baltica from the Late Precambrian to the Early Ordovician

    NASA Astrophysics Data System (ADS)

    Torsvik, T. H.; Cocks, L. R.

    2004-05-01

    Current thinking supports the existence of the Rodinia supercontinent which consolidated at perhaps 1100 to 1000 million years ago and most probably disintegrated somewhere before 800 Ma. Within the Rodinian collage, Baltica was adjacent to, and probably welded to, Laurentia, with the modern eastern (Uralian) part of Baltica conjugate with the north of Laurentia. Laurentia was in turn attached to the South American terranes of Rio Plata and Amazonia, and possibly also West Africa. Baltica became an independent terrane when it split off from Laurentia, leaving a widening Iapetus Ocean between the two. When this rifting actually commenced is a matter of dispute due to very conflicting palaeomagnetic data from both Laurentia and Baltica; however, we favor that the southern part of the Iapetus, between Laurentia and South America, opened first at about 570 Ma and that this rifting spread gradually northwards until Baltica separated from Laurentia at approximately 550 Ma, near the end of Precambrian time at 543 Ma. New palaeomagnetic and geochronological data from the 616-610 Ma Egersund Dykes (SW Baltica) place Baltica at the south pole whereas subsequent Late Precambrian to Early Cambrian poles places Baltica at lower latitudes. During the late and middle Vendian, the NW margin of Baltica changed from an extensional tectonic regime to an active margin (Timanian Orogeny) in which microcontinental blocks in the Timan-Pechora, northern Ural and Novaya Zemlya areas were united with Baltica at 550-560 Ma. Largely between Middle Cambrian and Middle Ordovician times, the whole large terrane of Baltica underwent a very substantial rotation of about 120°, the maximum rate of this rotation occurred in late Cambrian and early Ordovician times. Much of the craton of Baltica appears to have been submerged under shelf seas for long parts of this time, which lasted from 544 to 490 Ma. As a consequence the olenid trilobite fauna represent a fauna living largely in niches which were

  12. Siliceous spicules in a vauxiid sponge (Demospongia) from the Kaili Biota(Cambrian Stage 5), Guizhou, South China

    NASA Astrophysics Data System (ADS)

    Yang, X.-L.; Zhao, Y.-L.; Babcock, L. E.; Peng, J.

    2017-02-01

    Fossils of the sponge Angulosuspongia sinensis from calcareous mudstones of the middle and upper part of the Kaili Formation (Cambrian Stage 5) in the Jianhe area of Guizhou province, South China, exhibit an apparently reticulate pattern, characteristic of the Vauxiidae. Energy Dispersive X-Ray Spectrometry (EDS) and Raman spectroscopy analysis indicate the presence of silica in the skeletal elements of these fossils, suggesting that this taxon possessed a skeleton comprised of spicules. This is the first confirmation of siliceous skeletal elements in fossils of the family Vauxiidae, and it lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, which were subsequently lost and replaced by spongin later in the evolutionary history of this lineage. The new materials provide critical insight into the phylogeny and evolution of biomineralization in the Demosopongiae.

  13. Uranium in the Upper Cambrian black shale of Sweden

    USGS Publications Warehouse

    McKelvey, Vincent Ellis

    1955-01-01

    The Peltura zone of the Upper Cambrian black shales of Sweden contains about 0.02 percent uranium. Maximum amounts are present in rocks deposited in an embayment in the sea and in rocks in or closely adjacent to that part of the vertical sequence that contains maximum amounts of distillable oil, total organic matter, pyrite, and a black highly uraniferous kerogen called "kolm". Available data suggest that the precipitation of uranium is favored by a low redox potential and that the uranium in the shale matrix may be in fine-grained kolm.

  14. Cambrian intermediate-mafic magmatism along the Laurentian margin: Evidence for flood basalt volcanism from well cuttings in the Southern Oklahoma Aulacogen (U.S.A.)

    NASA Astrophysics Data System (ADS)

    Brueseke, Matthew E.; Hobbs, Jasper M.; Bulen, Casey L.; Mertzman, Stanley A.; Puckett, Robert E.; Walker, J. Douglas; Feldman, Josh

    2016-09-01

    The Southern Oklahoma Aulocogen (SOA) stretches from southern Oklahoma through the Texas panhandle and into Colorado and New Mexico, and contains mafic through silicic magmatism related to the opening of the Iapetus Ocean during the early Cambrian. Cambrian magmatic products are best exposed in the Wichita Mountains (Oklahoma), where they have been extensively studied. However, their ultimate derivation is still somewhat contentious and centers on two very different models: SOA magmatism has been suggested to occur via [1] continental rifting (with or without mantle plume emplacement) or [2] transform-fault related magmatism (e.g., leaky strike-slip faults). Within the SOA, the subsurface in and adjacent to the Arbuckle Mountains in southern Oklahoma contains thick sequences of mafic to intermediate lavas, intrusive bodies, and phreatomagmatic deposits interlayered with thick, extensive rhyolite lavas, thin localized tuffs, and lesser silicic intrusive bodies. These materials were first described in the Arbuckle Mountains region by a 1982 drill test (Hamilton Brothers Turner Falls well) and the best available age constraints from SOA Arbuckle Mountains eruptive products are 535 to 540 Ma. Well cuttings of the mafic through intermediate units were collected from that well and six others and samples from all but the Turner Falls and Morton wells are the focus of this study. Samples analyzed from the wells are dominantly subalkaline, tholeiitic, and range from basalt to andesite. Their overall bulk major and trace element chemistry, normative mineralogy, and Srsbnd Nd isotope ratios are similar to magmas erupted/emplaced in flood basalt provinces. When compared with intrusive mafic rocks that crop out in the Wichita Mountains, the SOA well cuttings are geochemically most similar to the Roosevelt Gabbros. New geochemical and isotope data presented in this study, when coupled with recent geophysical work in the SOA and the coeval relationship with rhyolites, indicates

  15. Oxygen-isotope trends and seawater temperature changes across the Late Cambrian Steptoean positive carbon-isotope excursion (SPICE event)

    USGS Publications Warehouse

    Elrick, M.; Rieboldt, S.; Saltzman, M.; McKay, R.M.

    2011-01-01

    The globally recognized Late Cambrian Steptoean positive C-isotope excursion (SPICE) is characterized by a 3???-5??? positive ??13C shift spanning <4 m.y. Existing hypotheses suggest that the SPICE represents a widespread ocean anoxic event leading to enhanced burial/preservation of organic matter (Corg) and pyrite. We analyzed ??18O values of apatitic inarticulate brachiopods from three Upper Cambrian successions across Laurentia to evaluate paleotemperatures during the SPICE. ??18O values range from ~12.5??? to 16.5???. Estimated seawater temperatures associated with the SPICE are unreasonably warm, suggesting that the brachiopod ??18O values were altered during early diagenesis. Despite this, all three localities show similar trends with respect to the SPICE ??13C curve, suggesting that the brachiopod apatite preserves a record of relative ??18O and temperature changes. The trends include relatively high ??18O values at the onset of the SPICE, decreasing and lowest values during the main event, and an increase in values at the end of the event. The higher ??18O values during the global extinction at the onset of the SPICE suggests seawater cooling and supports earlier hypotheses of upwelling of cool waters onto the shallow shelf. Decreasing and low ??18O values coincident with the rising limb of the SPICE support the hypothesis that seawater warming and associated reduced thermohaline circulation rates contributed to decreased dissolved O2 concentrations, which enhanced the preservation/burial of Corg causing the positive ??13C shift. ?? 2011 Geological Society of America.

  16. Tentaculate Fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) Interpreted as Primitive Deuterostomes

    PubMed Central

    Caron, Jean-Bernard; Conway Morris, Simon; Shu, Degan

    2010-01-01

    Molecular and morphological evidence unite the hemichordates and echinoderms as the Ambulacraria, but their earliest history remains almost entirely conjectural. This is on account of the morphological disparity of the ambulacrarians and a paucity of obvious stem-groups. We describe here a new taxon Herpetogaster collinsi gen. et sp. nov. from the Burgess Shale (Middle Cambrian) Lagerstätte. This soft-bodied vermiform animal has a pair of elongate dendritic oral tentacles, a flexible stolon with an attachment disc, and a re-curved trunk with at least 13 segments that is directed dextrally. A differentiated but un-looped gut is enclosed in a sac suspended by mesenteries. It consists of a short pharynx, a conspicuous lenticular stomach, followed by a narrow intestine sub-equal in length. This new taxon, together with the Lower Cambrian Phlogites and more intriguingly the hitherto enigmatic discoidal eldoniids (Cambrian-Devonian), form a distinctive clade (herein the cambroernids). Although one hypothesis of their relationships would look to the lophotrochozoans (specifically the entoprocts), we suggest that the evidence is more consistent with their being primitive deuterostomes, with specific comparisons being made to the pterobranch hemichordates and pre-radial echinoderms. On this basis some of the earliest ambulacrarians are interpreted as soft-bodied animals with a muscular stalk, and possessing prominent tentacles. PMID:20221405

  17. Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating

    USGS Publications Warehouse

    Avigad, D.; Kolodner, K.; McWilliams, M.; Persing, H.; Weissbrod, T.

    2003-01-01

    Voluminous Paleozoic sandstone sequences were deposited in northern Africa and Arabia following an extended Neoproterozoic orogenic cycle that culminated in the assembly of Gondwana. We measured sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages of detrital zircons separated from several Cambrian units in the Elat area of southern Israel in order to unravel their provenance. This sandstone forms the base of the widespread siliciclastic section now exposed on the periphery of the Arabian-Nubian shield in northeastern Africa and Arabia. Most of the detrital zircons we analyzed yielded Neoproterozoic concordant ages with a marked concentration at 0.55–0.65 Ga. The most likely provenance of the Neoproterozoic detritus is the Arabian-Nubian shield; 0.55–0.65 Ga was a time of posttectonic igneous activity, rift-related volcanism, and strike-slip faulting there. Of the zircons, 30% yielded pre-Neoproterozoic ages grouped at 0.9–1.1 Ga (Kibaran), 1.65–1.85 Ga, and 2.45–2.7 Ga. The majority of the pre-Neoproterozoic zircons underwent Pb loss, possibly as a consequence of the Pan-African orogeny resetting their provenance. Rocks of the Saharan metacraton and the southern Afif terrane in Saudi Arabia (∼1000 km south of Elat) are plausible sources of these zircons. Kibaran basement rocks are currently exposed more than 3000 km south of Elat (flanking the Mozambique belt), but the shape of the detrital zircons of that age and the presence of feldspar in the host sandstone are not fully consistent with such a long-distance transport. Reworking of Neoproteorozoic glacial detritus may explain the presence of Kibaran detrital zircons in the Cambrian of Elat, but the possibility that the Arabian-Nubian shield contains Kibaran rocks (hitherto not recognized) should also be explored.

  18. Siliceous spicules in a vauxiid sponge (Demospongia) from the Kaili Biota(Cambrian Stage 5), Guizhou, South China

    PubMed Central

    Yang, X.-L.; Zhao, Y.-L.; Babcock, L. E.; Peng, J.

    2017-01-01

    Fossils of the sponge Angulosuspongia sinensis from calcareous mudstones of the middle and upper part of the Kaili Formation (Cambrian Stage 5) in the Jianhe area of Guizhou province, South China, exhibit an apparently reticulate pattern, characteristic of the Vauxiidae. Energy Dispersive X-Ray Spectrometry (EDS) and Raman spectroscopy analysis indicate the presence of silica in the skeletal elements of these fossils, suggesting that this taxon possessed a skeleton comprised of spicules. This is the first confirmation of siliceous skeletal elements in fossils of the family Vauxiidae, and it lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, which were subsequently lost and replaced by spongin later in the evolutionary history of this lineage. The new materials provide critical insight into the phylogeny and evolution of biomineralization in the Demosopongiae. PMID:28220860

  19. Facies patterns and conodont biogeography in Arctic Alaska and the Canadian Arctic Islands: Evidence against juxtaposition of these areas during early Paleozoic time

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, A.G.; Bradley, D.C.; De Freitas, T. A.

    2000-01-01

    Differences in lithofacies and biofacies suggest that lower Paleozoic rocks now exposed in Arctic Alaska and the Canadian Arctic Islands did not form as part of a single depositional system. Lithologic contrasts are noted in shallow- and deep-water strata and are especially marked in Ordovician and Silurian rocks. A widespread intraplatform basin of Early and Middle Ordovician age in northern Alaska has no counterpart in the Canadian Arctic, and the regional drowning and backstepping of the Silurian shelf margin in Canada has no known parallel in northern Alaska. Lower Paleozoic basinal facies in northern Alaska are chiefly siliciclastic, whereas resedimented carbonates are volumetrically important in Canada. Micro- and macrofossil assemblages from northern Alaska contain elements typical of both Siberian and Laurentian biotic provinces; coeval Canadian Arctic assemblages contain Laurentian forms but lack Siberian species. Siberian affinities in northern Alaskan biotas persist from at least Middle Cambrian through Mississippian time and appear to decrease in intensity from present-day west to east. Our lithologic and biogeographic data are most compatible with the hypothesis that northern Alaska-Chukotka formed a discrete tectonic block situated between Siberia and Laurentia in early Paleozoic time. If Arctic Alaska was juxtaposed with the Canadian Arctic prior to opening of the Canada basin, biotic constraints suggest that such juxtaposition took place no earlier than late Paleozoic time.

  20. Cambrian rivers and floodplains: the significance of microbial cementation, groundwater and aeolian sediment transport

    NASA Astrophysics Data System (ADS)

    Reesink, A. J. H.; Best, J.; Freiburg, J. T.; Nathan, W.

    2016-12-01

    Rivers that existed before land plants colonized the Earth are commonly considered to be unaffected by microbial activity on their floodplains, because the limited cementation produced by microbial activity is insufficient to stabilize the river banks. Although this assumption is likely correct, such emphasis on channel dynamics ignores the potential role of floodplain dynamics as an integral component of the river system. Detailed analysis of cores from the Cambrian Mount Simon Sandstone, Illinois, suggests that a significant proportion of the terrestrial sequence is composed of flat-bedded `crinkly' structures that provide evidence of cementation by soil crusts and microbial biofilms, and that promoted the adhesion of sediment to sticky surfaces. Wind ripples and local desert pavements were abundant. These findings highlight that sediment deposition on Cambrian floodplains was often dominated by wind in locations where the ground water table reached the surface, and was thus likely independent of sediment transport within the river channel. Erosion by wind would thus have been hindered by surface cementation and the formation of desert pavements. Such ground water control on deposition, and resistance to erosion by floodplain surface hardening, appear to have been the primary controls on Cambrian floodplain topography. Because floodplain topography poses a key control on channel and floodplain flow, these processes may have affected patterns of erosion and deposition, as well as reach-scale dynamics such as channel avulsions. The autonomous operation of wind-and-groundwater controlled floodplains makes pre-vegetated river systems more sensitive to climatic conditions such as precipitation and evaporation, and strikingly different from those that occurred after the development of land plants.

  1. Stratigraphic framework of Cambrian and Ordovician rocks in the central Appalachian Basin from Medina County, Ohio, through southwestern and south-central Pennsylvania to Hampshire County, West Virginia

    USGS Publications Warehouse

    Ryder, Robert T.; Harris, Anita G.; Repetski, John E.; revised and digitized by Crangle, Robert D.

    2003-01-01

    are identified by the following descriptive names: (1) sandstone, shale, limestone, and dolomite unit, (2) dolomite and sandstone unit, (3) limestone and black shale unit, and (4) shale and sandstone unit. Each of these units and their associated subunits thicken from west to east across the restored section to a maximum near the depositional axis of the Rome trough and then thin eastward to the end of the section. The sandstone, shale, limestone, and dolomite unit is largely confined to the asymmetric graben that marks the initial phase of the Rome trough. This unit is Early and Middle Cambrian in age and consists, in ascending order, of a basal sandstone unit (undrilled but probably present), the Tomstown Dolomite (undrilled but probably present), the Waynesboro Formation, and the Pleasant Hill Limestone and its equivalent lower one-third of the Elbrook Formation at the eastern end of the section. The dolomite and sandstone unit forms the core of the Cambrian and Ordovician sequence. In the Rome trough and on the adjoining South-central Pennsylvania arch, this unit consists, in ascending order, of the Middle and Upper Cambrian Warrior Formation and the equivalent upper two-thirds of the Elbrook Formation at the eastern end of the section, the Upper Cambrian Gatesburg Formation, and the Lower Ordovician and Middle Ordovician (Whiterockian and Chazyan) Beekmantown Group. West of the Ohio-West Virginia hinge zone, the dolomite and sandstone unit consists, in ascending order, of the Conasauga Formation of Janssens (1973), the Krysik sandstone of driller's usage, the B zone of Calvert (1964), the Knox Dolomite and the associated Rose Run Sandstone Member, and the Wells Creek Formation. The widespread Knox unconformity is located at the base of the Wells Creek Formation and at or near the top of the adjoining Beekmantown Group, except near the depositional axis of the Rome trough, where the unconformity seems to be absent. The limestone and black shale unit i

  2. Le volcanisme cambrien du Maroc central : implications géodynamiquesThe Central Morocco Cambrian volcanism: geodynamic implications

    NASA Astrophysics Data System (ADS)

    Ouali, Houssa; Briand, Bernard; Bouchardon, Jean-Luc; Capiez, Paul

    2003-05-01

    In southeastern Central Morocco, the Bou-Acila volcanic complex is considered of Cambrian age. In spite of low-grade metamorphic effect, initial volcanic texture and mineralogy can be recognized and volcanic rocks are dominated by dolerites and porphyric dolerites. The initial mineralogy is composed of plagioclases, pyroxenes and dark minerals. A secondary mineral assemblage is composed of albite, epidote, chlorite and calcite. According to their immobile elements compositions, the southeastern central Morocco metavolcanites are of within-plate continental tholeiites. This volcanism and those recognized in many other areas in Morocco confirm a Cambrian extensive episode within the Gondwana supercontinent. To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).

  3. High-Precision U-Pb Geochronology and Correlation: An example Using the Neoproterozic-Cambrian Transition

    NASA Astrophysics Data System (ADS)

    Bowring, S. A.; Grotzinger, J. P.; Amthor, J.; Martin, M. E.

    2001-05-01

    The precise, global correlation of Precambrian and Paleozoic sedimentary rocks can be achieved using temporally calibrated chemostratigraphic records. This approach is essential for determining rates and causes of environmental and faunal change, including mass extinctions. For example, The Neoproterozoic is marked by major environmental change, including periods of global glaciation, large fluctuations in the sequestration of carbon and major tectonic reorganization followed by the explosive diversification of animals in the earliest Cambrian. The extreme climatic change associated with these glaciations have been implicated as a possible trigger for the Cambrian explosion. The recognition of thin zircon-bearing air-fall ash in Neoproterozoic and Cambrian rocks has allowed the establishment of a high-precision temporal framework for animal evolution and is helping to untangle the history of glaciations. In some cases analytical uncertainties translate to age uncertainties of less than 1 Ma and when integrated with chemostratigraphy, the potential for global correlations at even higher resolution. Progress in the global correlation of Neoproterozoic strata has been achieved through the use of C and Sr isotope chemostratigraphy although it has been hampered by a lack of precise geochronological and faunal control. For example, the period from ca 800-580 Ma is characterized by at least two and perhaps as many as four glacial events that are interpreted by many to be global glaciations on a "Snowball Earth". A lack of precise chronological constraints on the number and duration of glaciations, multiple large excursions in the carbon isotopic record, and an absence of detailed biostratigraphy have complicated global correlation and hindered our understanding of this important period of Earth history. However, the ongoing integration of chemostratigraphic and geochronological data are improving temporal resolution and detailed correlations. These data are critical for

  4. Early rifting deposition: examples from carbonate sequences of Sardinia (Cambrian) and Tuscany (Triassic-Jurassic), Italy: an analogous tectono-sedimentary and climatic context

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cocozza, T.; Gandin, A.

    Lower Cambrian Ceroide Limestone (Sardinia) and Lower Jurassic Massiccio Limestone (Tuscany) belong to sequences deposited in analogous tectono-sedimentary context: the former linked to the Caledonian Sardic Phase, the latter to the Alpine Orogeny. Both units consist of massive pure limestone characterized by marginal and lagoonal sequences repeatedly interfingering in the same geological structure. This distribution indicates a morphology of the platforms composed of banks (marginal facies) and shallow basins (lagoonal facies) comparable with a Bahamian complex. Dolomitization affects patchily the massive limestone bodies, and karstic features, breccias, and sedimentary dikes occur at their upper boundary. Both units overlie early dolomitemore » and evaporites (sabkha facies) containing siliciclastic intercalations in their lower and/or upper part and are unconformably covered by open-shelf red (hematitic), nodular limestone Ammonitico Rosso facies). The sedimentary evolution of the two sequences appears to have been controlled by synsedimentary tectonics whose major effects are the end of the terrigenous input, the bank-and-basin morphology of the platform, the irregular distribution of the dolomitization, and the nodular fabric of the overlying facies. The end of the Bahamian-type system is marked by the karstification of the emerged blocks and is followed by their differential sinking and burial under red-nodular facies. From a geodynamic viewpoint, sequences composed of Bahamian-like platform carbonates followed by Ammonitico Rosso facies imply deposition along continental margins subjected to block-faulting during an extensional regime connected with the beginning of continental rifting. Moreover, the variation from sabkha to Bahamian conditions suggests the drifting of the continent from arid to humid, tropical areas.« less

  5. Fossil embryos from the Middle and Late Cambrian period of Hunan, south China.

    PubMed

    Dong, Xi-Ping; Donoghue, Philip C J; Cheng, Hong; Liu, Jian-Bo

    2004-01-15

    Comparative embryology is integral to uncovering the pattern and process of metazoan phylogeny, but it relies on the assumption that life histories of living taxa are representative of their antecedents. Fossil embryos provide a crucial test of this assumption and, potentially, insight into the evolution of development, but because discoveries so far lack phylogenetic constraint, their significance is moot. Here we describe a collection of embryos from the Middle and Late Cambrian period (500 million years ago) of Hunan, south China, that preserves stages of development from cleavage to the pre-hatching embryo of a direct-developing animal comparable to living Scalidophora (phyla Priapulida, Kinorhyncha, Loricifera). The latest-stage embryos show affinity to the Lower Cambrian embryo Markuelia, whose life-history strategy contrasts both with the primitive condition inferred for metazoan phyla and with many proposed hypotheses of affinity, all of which prescribe indirect development. Phylogenetic tests based on these embryological data suggest a stem Scalidophora affinity. These discoveries corroborate, rather than contradict, the predictions of comparative embryology, providing direct historical support for the view that the life-history strategies of living taxa are representative of their stem lineages.

  6. The origin of the animals and a 'Savannah' hypothesis for early bilaterian evolution.

    PubMed

    Budd, Graham E; Jensen, Sören

    2017-02-01

    The earliest evolution of the animals remains a taxing biological problem, as all extant clades are highly derived and the fossil record is not usually considered to be helpful. The rise of the bilaterian animals recorded in the fossil record, commonly known as the 'Cambrian explosion', is one of the most significant moments in evolutionary history, and was an event that transformed first marine and then terrestrial environments. We review the phylogeny of early animals and other opisthokonts, and the affinities of the earliest large complex fossils, the so-called 'Ediacaran' taxa. We conclude, based on a variety of lines of evidence, that their affinities most likely lie in various stem groups to large metazoan groupings; a new grouping, the Apoikozoa, is erected to encompass Metazoa and Choanoflagellata. The earliest reasonable fossil evidence for total-group bilaterians comes from undisputed complex trace fossils that are younger than about 560 Ma, and these diversify greatly as the Ediacaran-Cambrian boundary is crossed a few million years later. It is generally considered that as the bilaterians diversified after this time, their burrowing behaviour destroyed the cyanobacterial mat-dominated substrates that the enigmatic Ediacaran taxa were associated with, the so-called 'Cambrian substrate revolution', leading to the loss of almost all Ediacara-aspect diversity in the Cambrian. Why, though, did the energetically expensive and functionally complex burrowing mode of life so typical of later bilaterians arise? Here we propose a much more positive relationship between late-Ediacaran ecologies and the rise of the bilaterians, with the largely static Ediacaran taxa acting as points of concentration of organic matter both above and below the sediment surface. The breaking of the uniformity of organic carbon availability would have signalled a decisive shift away from the essentially static and monotonous earlier Ediacaran world into the dynamic and burrowing world

  7. Pellet microfossils: Possible evidence for metazoan life in Early Proterozoic time

    PubMed Central

    Robbins, Eleanora Iberall; Porter, Karen Glaus; Haberyan, Kurt A.

    1985-01-01

    Microfossils resembling fecal pellets occur in acid-resistant residues and thin sections of Middle Cambrian to Early Proterozoic shale. The cylindrical microfossils average 50 × 110 μm and are the size and shape of fecal pellets produced by microscopic animals today. Pellets occur in dark gray and black rocks that were deposited in the facies that also preserves sulfide minerals and that represent environments analogous to those that preserve fecal pellets today. Rocks containing pellets and algal microfossils range in age from 0.53 to 1.9 gigayears (Gyr) and include Burgess Shale, Greyson and Newland Formations, Rove Formation, and Gunflint Iron-Formation. Similar rock types of Archean age, ranging from 2.68 to 3.8 Gyr, were barren of pellets. If the Proterozoic microfossils are fossilized fecal pellets, they provide evidence of metazoan life and a complex food chain at 1.9 Gyr ago. This occurrence predates macroscopic metazoan body fossils in the Ediacaran System at 0.67 Gyr, animal trace fossils from 0.9 to 1.3 Gyr, and fossils of unicellular eukaryotic plankton at 1.4 Gyr. Images PMID:16593599

  8. Proterozoic structure, cambrian rifting, and younger faulting as revealed by a regional seismic reflection network in the Southern Illinois Basin

    USGS Publications Warehouse

    Potter, C.J.; Drahovzal, James A.; Sargent, M.L.; McBride, J.H.

    1997-01-01

    Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: 1. Prominent Proterozoic layering, possibly equivalent to Proterozoic (???1 Ga) Middle Run Formation clastic strata and underlying (1.3-1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. 2. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. 3. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. 4. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. 5. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. 6. Where crossed by the seismic reflection line in southeast Illinois, some

  9. The oldest known priapulid-like scalidophoran animal and its implications for the early evolution of cycloneuralians and ecdysozoans.

    PubMed

    Liu, Yunhuan; Xiao, Shuhai; Shao, Tiequan; Broce, Jesse; Zhang, Huaqiao

    2014-05-01

    Morphological phylogenetic analyses suggest that scalidophorans (priapulids, loriciferans, and kinorhynchs) and nematoids (nematodes and nematomorphs) form the ecdysozoan clade Cycloneuralia, which is a sister group to panarthropods. It has been proposed that extant priapulids and Cambrian priapulid-like scalidophorans, because of their conserved evolution, have the potential to illuminate the ancestral morphology, ecology, and developmental biology of highly derived ecdysozoans such as nematods and arthropods. As such, Cambrian fossils, particularly Markuelia and possibly olivooids, can inform the early evolution of scalidophorans, cycloneuralians, and ecdysozoans. However, the scalidophoran Markuelia is known exclusively as embryo fossils, and the olivooids have been alternatively interpreted as cnidarians or cycloneuralians. Here, we describe a post-embryonic scalidophoran fossil Eopriapulites sphinx new genus and species, which represents the oldest known scalidophoran, from the early Cambrian Period (∼535 Ma) in South China. E. sphinx is similar to modern scalidophorans in having an introvert armed with hollow scalids, a collar with coronal scalids, and a pharynx with pharyngeal teeth, but its scalids and pharyngeal teeth are arranged in a hexaradial pattern. Phylogenetically resolved as a stem-group scalidophoran, E. sphinx shares a hexaradial pattern with the hexaradial arrangement of certain anatomical structures in kinorhynchs, loriciferans, nematoids, and Cambrian fossils such as Eolympia pediculata, which could also be a scalidophoran. Thus, the bodyplan of ancestral cycloneuralians may have had a component of hexaradial symmetry (i.e., some but not necessarily all anatomical parts are hexaradially arranged). If panarthropods are nested within paraphyletic cycloneuralians, as several molecular phylogenetic analyses suggest, the ancestral ecdysozoans may have been a legless worm possibly with a component of hexaradial symmetry. © 2014 Wiley

  10. Trilobite-based biostratigraphy (arthropoda-trilobita) and related faunas of the Cambrian from Sonora, Mexico

    NASA Astrophysics Data System (ADS)

    Cuen-Romero, F. J.; Valdez-Holguín, J. E.; Buitrón-Sánchez, B. E.; Monreal, R.; Enríquez-Ocaña, L. F.; Aguirre-Hinojosa, E.; Ochoa-Granillo, J. A.; Palafox-Reyes, J. J.

    2018-04-01

    A biostratigraphic analysis based on trilobites of the main Cambrian outcrops from Sonora, Mexico is performed. The data are based on a combination of field work and published sources, including four previously studied locations from northern and eastern Sonora (Caborca, Cananea, Mazatán, and Arivechi) as well as a new location in the central part of the state of Sonora (San José de Gracia). Chronostratigraphic positions are assigned to the Cambrian outcrops according to Peng et al., 2012 and Cohen et al., 2017. In the Caborca area, the Puerto Blanco, Proveedora, Buelna, Cerro Prieto, Arrojos and El Tren formations comprise a wide range of biozones, which starts from the Fritzaspis Zone until the Glossopleura walcotti Zone (Begadean-Lincolnian Series, global Stage 3-Stage 5, Series 2-Series 3). The Bolsa Quartzite and the Abrigo Limestone exposed in Cananea area are assigned to the Cedaria/Cedarina dakotaensis Zone until the Crepicephalus Zone (Lincolnian Series-Marjuman Stage, global Series 3-Guzhangian). In the San José de Gracia area, The Proveedora, Buelna, Cerro Prieto and El Gavilán formations range from the ?Bristolia mohavensis or ?Bristolia insolens zones until the upper part of Mexicella mexicana Zone, Albertella highlandensis Subzone (Series 2-Series 3, Stage 4-Stage 5). In the Arivechi area, the La Sata, El Mogallón, La Huerta and the Milpillas formations range from Poliella denticulata Zone to the Elvinia Zone (Lincolnian-Millardan, Delamaran-Steptoean, global Series 3-Furongian, Stage 5-Paibian). Paleozoic marine fauna distribution in northwest Mexico and the southwest United States of America, suggest that during this time an extensive faunal province existed, containing a great variety of marine invertebrates with notorious intraspecific affinity. The biotic association includes poriferans, archaeocyathids, brachiopods, mollusks, arthropods and echinoderms as predominant elements.

  11. Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants

    NASA Astrophysics Data System (ADS)

    Davies, Neil S.; Gibling, Martin R.

    2010-02-01

    In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodibility, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, and may increase bank stability, infiltration into substrates, and bed roughness. Vegetation also promotes the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Early Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Early Palaeozoic alluvial successions laid down prior to and during the initial colonization of the Earth's surface by plants. A comprehensive review of 144 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 34 alluvial successions across Europe and North America. The study was designed to identify changes in alluvial style during the period that vegetation was evolving and first colonizing alluvial environments. An increase in mudrock proportion and sandstone maturity is apparent, along with a decrease in overall sand grain size through the Early Palaeozoic. These trends suggest that primitive vegetation cover promoted the production and preservation of muds from the mid Ordovician onwards and increased the residence time of sand-grade sediment in alluvial systems. The compilation also enables the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and related to the evolution of specific palaeobotanical adaptations. The first markedly heterolithic alluvial

  12. Reactive oxygen species may play an essential role in driving biological evolution: The Cambrian Explosion as an example.

    PubMed

    Yang, Dong; Guo, Xuejun; Xie, Tian; Luo, Xiaoyan

    2018-01-01

    The Cambrian Explosion is one of the most significant events in the history of life; essentially all easily fossilizable animal body plans first evolved during this event. Although many theories have been proposed to explain this event, its cause remains unresolved. Here, we propose that the elevated level of oxygen, in combination with the increased mobility and food intake of metazoans, led to increased cellular levels of reactive oxygen species (ROS), which drove evolution by enhancing mutation rates and providing new regulatory mechanisms. Our hypothesis may provide a unified explanation for the Cambrian Explosion as it incorporates both environmental and developmental factors and is also consistent with ecological explanations for animal radiation. Future studies should focus on testing this hypothesis, and may lead to important insights into evolution. Copyright © 2017. Published by Elsevier B.V.

  13. Paleoproterozoic mojaveprovince in northwestern Mexico? Isotopic and U-Pb zircon geochronologic studies of precambrian and Cambrian crystalline and sedimentary rocks, Caborca, Sonora

    USGS Publications Warehouse

    Lang, Farmer G.; Bowring, S.A.; Matzel, J.; Maldonado, G.E.; Fedo, C.; Wooden, J.

    2005-01-01

    Whole-rock Nd isotopic data and U-Pb zircon geochronology from Precambrian crystalline rocks in the Caborca area, northern Sonora, reveal that these rocks are most likely a segment of the Paleoproterozoic Mojave province. Supporting this conclusion are the observations that paragneiss from the ??? 1.75 Ga Bamori Complex has a 2.4 Ga Nd model age and contains detrital zircons ranging in age from Paleo- proterozoic (1.75 Ga) to Archean (3.2 Ga). Paragneisses with similar age and isotopic characteristics occur in the Mojave province in southern California. In addition, "A-type" granite exposed at the southern end of Cerro Rajon has ca 2.0 Ga Nd model age and a U-Pb zircon age of 1.71 Ga, which are similar to those of Paleoproterozoic granites in the Mojave province. Unlike the U.S. Mojave province, the Caborcan crust contains ca. 1.1 Ga granite (Aibo Granite), which our new Nd isotopic data suggest is largely the product of anatexis of the local Precambrian basement. Detrital zircons from Neoproterozoic to early Cambrian miogeoclinal arenites at Caborca show dominant populations ca. 1.7 Ga, ca. 1.4 Ga, and ca. 1.1 Ga, with subordinate Early Cambrian and Archean zircons. These zircons were likely derived predominately from North American crust to the east and northeast, and not from the underlying Caborcan basement. The general age and isotopic similarities between Mojave province basement and overlying miogeoclinal sedimentary rocks in Sonora and southern California is necessary, but not sufficient, proof of the hypothesis that Sonoran crust is allochthonous and was transported to its current position during the Mesozoic along the proposed Mojave-Sonora megashear. One viable alternative model is that the Caborcan Precambrian crust is an isolated, autochthonous segment of Mojave province crust that shares a similar, but not identical, Proterozoic geological history with Mojave province crust found in the southwest United States ?? 2005 Geological Society of America.

  14. Evidence of the coupled geology system and its impact on the evolution of South China during the transformation from Sinian to Cambrian

    NASA Astrophysics Data System (ADS)

    Yang, C.; Wang, T.; Chen, Z.

    2016-12-01

    Separate interpretation of the evidence on tectonic, sedimentology or climate is insufficient to reappear the dynamic process of the evolution of the Earth surface, thus, tectonic, sedimentology and climate should be considered as a coupled system. Thick carbonate succession is overlaying on the paleo-uplift which is divided into two parts by a fluted belt in the center of Sichuan Basin. Sinian carbonate rocks is commonly composed by algae dolomite, while at the top of the Sinian succession the rocks had experienced meteoric karstification. Grain dolostones, fine-grained siliciclastic sandstones with mudstone appeare as the regional sediment of Cambrian. However, extraordinary thick mudstone had settled in the fluted belt, and the succession could be divided in to siliciclastic mud of the lower and clay-carbonate mud of the upper. The geochemistry and well log synthesized profile of Z4 well indicate that the chemical condition of siliciclastic mud and clay-carbonate mud had changed from oxidation to reduction, however the siliciclastic mud only appeared within the fluted belt. The fluted belt does not exist on the map of the gravity anomaly, but it had been convinced by the seismic data. The precursor of the fluted belt might be a sag within the platform basement, while with the sea level gradually raising up, the growth of algal mound exacerbated the geomorphology difference. Then a regression had happened at the end of the Sinian, starved all the algae and caused weather crust. Meanwhile, the fluted belt became a closed lagoon, received the sediment including algal mound fragment and biosilic crystals. Afterwards, rapidly increasing of the sea level deposited thick cay-carbonate mud that could be recognized as the sediment of maximum flooding surface. Then with the sea level decreasing, siliciclastic sandstones and inorganic grain carbonate became the main petrology of the Cambrian strata. Fine-grained eolian siliciclastic sandstones within the Cambrian carbonate

  15. Composition and origin of Early Cambrian Tiantaishan phosphorite-Mn carbonate ores, Shaanxi Province, China

    USGS Publications Warehouse

    Hein, J.R.; Fan, D.; Ye, J.; Liu, T.; Yeh, H.-W.

    1999-01-01

    The Tiantaishan phosphorite-Mn carbonate ores occur in the Early Cambrian Tananpo Formation in complexly folded and faulted rocks located in southern Shaanxi Province. About 65 x 106 tonnes of 17% P2O5 ore reserves exist and Mn-ore reserves are about 8.3 x 106 tonnes of +18% Mn. The stratigraphic sequence in ascending order consists of black phyllite, black to gray phosphorite ore, black phyllite, rhodochrostone ore, Mn mixed-carbonates, and dolostone. Data are presented from microprobe mineral chemistry, whole-rock chemistry, stable isotopes of carbonates, X-ray mineralogy, petrographic and SEM observations, and statistical analysis of chemical data. The dominant ore-forming minerals are hydroxy- and carbonate fluorapatite and Ca rhodochrosite, with Mg kutnahorite and dolomite comprising the Mn mixed-carbonate section. Pyrite occurs in all rock types and alabandite (MnS) occurs throughout the rhodochrostone section. The mean P2O5 content of phosphorite is 31% and argillaceous phosphorite is 16%, while the mean MnO content of rhodochrostone ore is 37%. Phosphorite ores are massive, spheroidal, laminated, and banded, while rhodochrostone ores have oolitic, spheroidal, and granular fabrics. The most distinguishing characteristics of the ores are high total organic carbon (TOC) contents (mean 8.4%) in the phosphorite and high P2O5 contents (mean 2.7%) in the rhodochrostone ore. The atypically high TOC contents in the Tiantaishan phosphorite probably result from very strong productivity leading to high sedimentation rates accompanied by weak reworking of sediments; poor utilization of the organic matter by bacteria; and/or partial replacement of bacterial or algal mats by the apatite. The depositional setting of the ores was the margin of an epicontinental seaway created as a direct consequence of global processes that included break-up of a supercontinent, formation of narrow seaways, creation of extensive continental shelves, overturn of stagnant, metal-rich deep

  16. Geochronology and geochemistry of early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China: Implications for the tectonic evolution of the eastern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-wei; Xu, Wen-liang; Pei, Fu-ping; Wang, Feng; Guo, Peng

    2016-09-01

    This paper presents new zircon U-Pb, Hf isotope, and whole-rock major and trace element data for early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China, in order to constrain the early Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt (CAOB). Zircon U-Pb dating indicates that early Paleozoic magmatic events within the northern Songnen-Zhangguangcai Range Massif (SZM) can be subdivided into four stages: Middle Cambrian ( 505 Ma), Late Cambrian ( 490 Ma), Early-Middle Ordovician ( 470 Ma), and Late Ordovician (460-450 Ma). The Middle Cambrian monzogranites are K-rich, weakly to strongly peraluminous, and characterized by pronounced heavy rare earth element (HREE) depletions, high Sr/Y ratios, low Y concentrations, low primary zircon εHf(t) values (- 6.79 to - 1.09), and ancient two-stage model (TDM2) ages (1901-1534 Ma). These results indicate derivation from partial melting of thickened ancient crustal materials that formed during the amalgamation of the northern SZM and the northern Jiamusi Massif (JM). The Late Cambrian monzonite, quartz monzonite, and monzogranite units are chemically similar to A-type granites, and contain zircons with εHf(t) values of - 2.59 to + 1.78 and TDM2 ages of 1625-1348 Ma. We infer that these rocks formed from primary magmas generated by partial melting of Mesoproterozoic accreted lower crustal materials in a post-collisional extensional environment. The Early-Middle Ordovician quartz monzodiorite, quartz monzonite, monzogranite, and rhyolite units are calc-alkaline, relatively enriched in light REEs (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), depleted in HREEs and high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), and contain zircons with εHf(t) values of - 7.33 to + 4.98, indicative of formation in an active continental margin setting. The Late Ordovician alkali-feldspar granite and rhyolite units have A-type granite affinities that suggest they formed in an

  17. Uranium isotopes distinguish two geochemically distinct stages during the later Cambrian SPICE event

    PubMed Central

    Dahl, Tais W.; Boyle, Richard A.; Canfield, Donald E.; Connelly, James N.; Gill, Benjamin C.; Lenton, Timothy M.; Bizzarro, Martin

    2015-01-01

    Anoxic marine zones were common in early Paleozoic oceans (542–400 Ma), and present a potential link to atmospheric pO2 via feedbacks linking global marine phosphorous recycling, primary production and organic carbon burial. Uranium (U) isotopes in carbonate rocks track the extent of ocean anoxia, whereas carbon (C) and sulfur (S) isotopes track the burial of organic carbon and pyrite sulfur (primary long-term sources of atmospheric oxygen). In combination, these proxies therefore reveal the comparative dynamics of ocean anoxia and oxygen liberation to the atmosphere over million-year time scales. Here we report high-precision uranium isotopic data in marine carbonates deposited during the Late Cambrian ‘SPICE’ event, at ca. 499 Ma, documenting a well-defined −0.18‰ negative δ238U excursion that occurs at the onset of the SPICE event’s positive δ13C and δ34S excursions, but peaks (and tails off) before them. Dynamic modelling shows that the different response of the U reservoir cannot be attributed solely to differences in residence times or reservoir sizes - suggesting that two chemically distinct ocean states occurred within the SPICE event. The first ocean stage involved a global expansion of euxinic waters, triggering the spike in U burial, and peaking in conjunction with a well-known trilobite extinction event. During the second stage widespread euxinia waned, causing U removal to tail off, but enhanced organic carbon and pyrite burial continued, coinciding with evidence for severe sulfate depletion in the oceans (Gill et al., 2011). We discuss scenarios for how an interval of elevated pyrite and organic carbon burial could have been sustained without widespread euxinia in the water column (both non-sulfidic anoxia and/or a more oxygenated ocean state are possibilities). Either way, the SPICE event encompasses two different stages of elevated organic carbon and pyrite burial maintained by high nutrient fluxes to the ocean, and potentially

  18. Microbial involvement in the formation of Cambrian sea-floor silica-iron oxide deposits, Australia

    NASA Astrophysics Data System (ADS)

    Duhig, Nathan C.; Davidson, Garry J.; Stolz, Joe

    1992-06-01

    The Cambrian-Ordovician Mount Windsor volcanic belt in northern Australia is host to stratiform lenses of massive ferruginous chert that are spatially associated with volcanogenic massive sulfide occurrences, in particular the Thalanga zinc-lead-copper-silver deposit. The rocks are composed principally of Fe2O3 and SiO2, with very low concentrations of alkalic elements, and lithogenous elements such as Al, Zr, and Ti; they are interpreted as nearly pure chemical sediments. Textural evidence is documented of the integral role of filamentous bacteria (and/or fungi) in depositing iron from hydrothermal fluids, and of the inorganic precipitation of silica-iron-oxyhydroxide gels that subsequently matured to subcrystalline and crystalline silica forms. At least three distinct iron-accumulating microbial forms are distinguished: networks of septate filaments, nonseptate filament networks, and extremely coarse branching filaments that do not reconnect. Values for δ34S in disseminated pyrite are up to 50‰ lighter than those of contemporaneous Cambrian seawater, suggesting postdepositional colonization of some ironstones by sulfur-reducing bacteria. The site not only preserves the textural interplay of biological and inorganic depositional processes in exhalites, but also extends the oldest known instance of microbial mediation in vent-proximal hydrothermal iron precipitation to at least 500 Ma.

  19. Tidal-bundle sequences in the Jordan Sandstone (Upper Cambrian), southeastern Minnesota, U.S.A.: Evidence for tides along inboard shorelines of the Sauk Epicontinental Sea

    USGS Publications Warehouse

    Tape, C.H.; Cowan, Clinton A.; Runkel, Anthony C.

    2003-01-01

    This study documents for the first time tidal bundling in a lower Paleozoic sheet sandstone from the cratonic interior of North America, providing insights into the hydrodynamics of ancient epicontinental seas. The Jordan Sandstone (Upper Cambrian) in the Upper Mississippi Valley contains large-scale planar tabular cross-sets with tidal-bundle sequences, which were analyzed in detail at an exceptional exposure. Tidal-bundle sequences (neap-spring-neap cycles) were delineated by foreset thickening-thinning patterns and composite shale drapes, the latter of which represent accumulations of mud during the neap tides of neap-spring-neap tidal cycles. Fourier analysis of the bundle thickness data from the 26 measurable bundle sequences revealed cycles ranging from 15 to 34 bundles per sequence, which suggests a semidiurnal or mixed tidal system along this part of the Late Cambrian shoreline. We extend the tidal interpretation to widespread occurrences of the same facies in outcrops of lesser quality, where the facies is recognizable but too few bundles are exposed for tidal cycles to be measured. By doing so, this study shows that tidally generated deposits have a significant geographic and temporal extent in Upper Cambrian strata of central mid-continent North America. The deposition and preservation of tidal facies was related to the intermittent development of shoreline embayments during transgressions. The tidally dominated deposits filled ravined topographies that were repeatedly developed on the updip parts of the shoreface. Resulting coastal geomorphologies, accompanied perhaps by larger-scale changes in basinal conditions and/or configuration, led to changes in depositional conditions from wave-dominated to tide-dominated. Outcrops of the Jordan Sandstone tidal facies in the Upper Mississippi Valley represent the farthest inboard recorded transmission of ocean-generated tides in the Laurentian epicontinental seas, demonstrating that tidal currents were

  20. EBSD characterization of pre-Cambrian deformations in conglomerate pebbles (Sierra de la Demanda, Northern Spain)

    NASA Astrophysics Data System (ADS)

    Puelles, Pablo; Ábalos, Benito; Fernández-Armas, Sergio

    2010-05-01

    Pre-Cambrian and unconformable earliest Cambrian rocks from the Sierra de la Demanda (N Spain) exhibit field and microstructural relationships that attest to orogenic events recorded by concealed basement rocks. Neoproterozoic foliated slates ("Anguiano Schists") crop out under up to 300 m thick, unfoliated quartz-rich conglomerates ("Anguiano Conglomerates") and quartzites which are stratigraphically ca. 600 m below the oldest, paleontologically dated, pre-trilobitic Cambrian layers (likely older than 520 Ma). The Anguiano Conglomerates contain mm to cm grainsized well-rounded pebbles of various types including monocrystalline quartz, detrital zircon and tourmaline-bearing sandstones, black cherts and metamorphic poly-crystalline quartz aggregates. The undeformed matrix is made of much smaller (diagenetically overgrown) monocrystaline quartz grains and minor amounts of accesory zircon, tourmaline and mica. Black chert pebbles exhibit microstructural evidence of brittle deformation (microfaults and thin veins of syntaxial fibrous quartz). These and the fine-grained sandstone pebbles can also exhibit ductile deformations (microfolds with thickened hinges and axial planar continuous foliations), too. Polycrystalline quartz pebbles exhibit a variety of microstructures that resulted from syn-metamorphic ductile deformations. These are recognisable under the petrographic microscope and include continuous foliations, quartz shape fabrics, various types of subgrain or recrystallized new grain microtextures, and lattice preferred orientations (LPOs). Conventional characterization of quartz fabrics (after oriented structural sections) is challenged in conglomerate pebble thin sections by the difficulty of unraveling in them the complete structural reference framework provided by foliation (whose trace can be unraveled) and lineation orientation (which cannot be directly identified). Quartz in various metamorphic polycrystalline pebbles was studied with the Electron Back

  1. The Late Cambrian Takaka Terrane, NW Nelson, New Zealand: Accretionary-prism development and arc collision followed by extension and fan-delta deposition at the SE margin of Gondwana

    NASA Astrophysics Data System (ADS)

    Pound, K. S.

    2013-12-01

    convergence, but is reinterpreted here as a ';true' fan-delta deposit, sedimentologically similar to deposits associated with extension. Textural and compositional data for the Lockett Conglomerate indicates rapid supply of new material (including quartzite, granite, gabbro, and amphibolitic metavolcanics). The Lockett Conglomerate is proposed here to record the initiation of extension, during which basement faults in the hinterland exposed previously buried source rocks. This new interpretation of the Lockett Conglomerate places that initiation of extension and subsequent passive margin sedimentation (Mt. Ellis and Mt. Arthur Groups) earlier (late Middle Cambrian) than previous work has suggested (Late Cambrian or Early Ordovician). These new interpretations provide input useful for correlations and interpretations of the complex mosaic that preserves a record of tectonic activity and processes at the Antarctic, Tasmanian and SE Australian portions of the Cambrian Gondwana margin.

  2. Characterization of the Lower Cambrian sandstone aquifer in the Swedish Baltic Sea area - assessment regarding its potential suitability for storage of CO2

    NASA Astrophysics Data System (ADS)

    Erlström, M.; Sivhed, U.

    2012-04-01

    In the Baltic region the Cambrian sandstone is considered to have great economic value concerning its aquifer and reservoir properties. Its potential as petroleum reservoir is well known, especially from the Polish, Lithuanian and Russian sectors of the Baltic Sea where oil and gas has been found in anticline traps in the sandstone sequence. Offshore exploration in the Swedish sector has so far not encountered any significant findings of oil and gas. However, the extensive exploration has generated data, which is now being used for assessing the overall properties regarding suitability for storage of CO2. The Swedish primary industry has a great interest in finding potential sites for storage of CO2. A suitable site in the Baltic Sea would be a most favourable alternative in comparison to more remote alternatives such as deep saline aquifers in the North Sea. The Lower Cambrian is in the Swedish sector of the Baltic Sea composed of three main sandstone units varying in thickness between 5 and 50 m occurring within an up to 250 m thick Cambrian sequence dominated by fine-grained terriclastic sediments. The limit of Lower Palaeozoic sequence in the Baltic area is today defined by erosional truncation because of the gently dipping Lower Palaeozoic sequence. To the north and northwest, the limit is found in the Pre-Quaternary, whereas the erosional limit is deeply buried beneath Permian and Mesozoic sediments to the south. Here the Lower Palaeozoic limit is buried to depths reaching more than 2 km. The Cambrian sequence in the distal parts of the Swedish sector occurs at depths of c. 1300 m while it constitutes the bedrock surface in a narrow zone trending from Öland to the north of of Gotland. Sandstone beds constitute 40-60% of the total Cambrian sequence. The main sandstone units have a regional distribution of several thousands of square kilometres. The up to 50 m thick Faludden sandstone member exhibits the best reservoir properties including porosities in the

  3. Oxygenation history of the Neoproterozoic to early Phanerozoic and the rise of land plants

    NASA Astrophysics Data System (ADS)

    Wallace, Malcolm W.; Hood, Ashleigh vS.; Shuster, Alice; Greig, Alan; Planavsky, Noah J.; Reed, Christopher P.

    2017-05-01

    There has been extensive debate about the history of Earth's oxygenation and the role that land plant evolution played in shaping Earth's ocean-atmosphere system. Here we use the rare earth element patterns in marine carbonates to monitor the structure of the marine redox landscape through the rise and diversification of animals and early land plants. In particular, we use the relative abundance of cerium (Ceanom), the only redox-sensitive rare earth element, in well-preserved marine cements and other marine precipitates to track seawater oxygen levels. Our results indicate that there was only a moderate increase in oceanic oxygenation during the Ediacaran (average Cryogenian Ceanom = 1.1, average Ediacaran Ceanom = 0.62), followed by a decrease in oxygen levels during the early Cambrian (average Cryogenian Ceanom = 0.90), with significant ocean anoxia persisting through the early and mid Paleozoic (average Early Cambrian-Early Devonian Ceanom = 0.84). It was not until the Late Devonian that oxygenation levels are comparable to the modern (average of all post-middle Devonian Ceanom = 0.55). Therefore, this work confirms growing evidence that the oxygenation of the Earth was neither unidirectional nor a simple two-stage process. Further, we provide evidence that it was not until the Late Devonian, when large land plants and forests first evolved, that oxygen levels reached those comparable to the modern world. This is recorded with the first modern-like negative Ceanom (values <0.6) occurring at around 380 Ma (Frasnian). This suggests that land plants, rather than animals, are the 'engineers' responsible for the modern fully oxygenated Earth system.

  4. Clades reach highest morphological disparity early in their evolution

    PubMed Central

    Hughes, Martin; Gerber, Sylvain; Wills, Matthew Albion

    2013-01-01

    There are few putative macroevolutionary trends or rules that withstand scrutiny. Here, we test and verify the purported tendency for animal clades to reach their maximum morphological variety relatively early in their evolutionary histories (early high disparity). We present a meta-analysis of 98 metazoan clades radiating throughout the Phanerozoic. The disparity profiles of groups through time are summarized in terms of their center of gravity (CG), with values above and below 0.50 indicating top- and bottom-heaviness, respectively. Clades that terminate at one of the “big five” mass extinction events tend to have truncated trajectories, with a significantly top-heavy CG distribution overall. The remaining 63 clades show the opposite tendency, with a significantly bottom-heavy mean CG (relatively early high disparity). Resampling tests are used to identify groups with a CG significantly above or below 0.50; clades not terminating at a mass extinction are three times more likely to be significantly bottom-heavy than top-heavy. Overall, there is no clear temporal trend in disparity profile shapes from the Cambrian to the Recent, and early high disparity is the predominant pattern throughout the Phanerozoic. Our results do not allow us to distinguish between ecological and developmental explanations for this phenomenon. To the extent that ecology has a role, however, the paucity of bottom-heavy clades radiating in the immediate wake of mass extinctions suggests that early high disparity more probably results from the evolution of key apomorphies at the base of clades rather than from physical drivers or catastrophic ecospace clearing. PMID:23884651

  5. Biostratigraphy and chronostratigraphy of the Cambrian-Ordovician great American carbonate bank

    USGS Publications Warehouse

    Taylor, John F.; Repetski, John E.; Loch, James D.; Leslie, Stephen A.

    2012-01-01

    The carbonate strata of the great American carbonate bank (GACB) have been subdivided and correlated with ever-increasing precision and accuracy during the past half century through use of the dominant organisms that evolved on the Laurentian platform through the Cambrian and the Ordovician. Trilobites and conodonts remain the primary groups used for this purpose, although brachiopods, both calcareous and phosphatic, and graptolites are very important in certain facies and intervals. A series of charts show the chronostratigraphic units (series and stages) currently in use for deposits of the GACB and the biostratigraphic units (zones, subzones, and biomeres) whose boundaries delineate them. Older and, in some cases obsolete, stages and faunal units are included in the figures to allow users to relate information from previous publications and/or industry databases to modern units. This chapter also provides a brief discussion on the use of biostratigraphy in the recognition and interregional correlation of supersequence boundaries within the Sauk and Tippecanoe megasequences, and the varied perspectives on the nature of biostratigraphic units and their defining taxa during the past half century. Also included are a concise update on the biomere concept, and an explanation of the biostratigraphic consequences of a profound change in the dynamics of extinction and replacement that occurred on the GACB in the Early Ordovician when the factors responsible for platformwide biomere-type extinctions faded and ultimately disappeared. A final section addresses recent and pending refinements in the genus and species taxonomy of biostratigraphically significant fossil groups, the potential they hold for greatly improved correlation, and the obstacles to be overcome for that potential to be realized.

  6. Palaeoenvironmental and geochemical approach of Archaeocyath-rich facies from Lower Cambrian of Western Gondwana margin at Central Iberian Zone (Urda, Toledo Mountains, Spain)

    NASA Astrophysics Data System (ADS)

    Menéndez, Silvia; Rodríguez-Martínez, Marta; Moreno-Eris, Elena; Perejón, Antonio; Reitner, Joachim

    2010-05-01

    Archaeocyath-rich facies are located in a quarry close to Urda village, at Toledo Mountains, Spain. The outcrops belong to the Caliza de los Navalucillos Formation and they record a considerably high diverse archaeocyath assemblage in the Lower Cambrian successions from the Central Iberian Zone (Julivert et al. 1972 [1974]). In fact, it is first time recorded the presence of Agyrekocyathus, Dokidocyathus, and Plicocyathus in the Central Iberian Zone. Therefore Plicocyathus is no longer exclusive to biozone VI in Spain. The presence of Anthomorpha is characteristic for the early Botomian, presently early Stage 4 (ICS, 2009), and the assemblage corresponds to the biozone VII (late Ovetian, following the biozonation of Perejón & Moreno-Eiris, 2006). The fossiliferous part of the succession is formed by seven lithofacies, all of them tectonically folded and with a low grade metamorphic overprint. They are comprised by two main groups of facies: (a) mound-shaped to massive lithofacies (A1, A2, A3, A4) and (b) massive to bedded and nodular lithofacies (B1, B2, B3). Archaeocyaths occur in several facies: (A1) mound-shaped white marble with irregular to stromatactoid cavities; (A2) massive mottled white to grey limestone; (A3) massive grey limestone with slumps levels; (A4) massive archaeocyath-rich orange limestone; as well as in carbonate nodules embedded in siltstones and cherts (B1, B2 and B3). The best preserved assemblage comes from the nodule record, where fossils are partially pyritized. This type of preservation is exceptional and has never been described before. XRD and wavelength-dispersive electron microprobe analyses reveal the presence of pyrite and pyrrotine partially altered to iron oxides and hydroxides (hematite and goethite) surrounding the archaeocyath cups. In Central Iberian Zone, the development of mounds and nodular facies like those described here is unusual, although the Botomian marks the peak for Early Cambrian archaeocyathan-microbial mounds

  7. Time in Early Childhood: Creative Possibilities with Different Conceptions of Time

    ERIC Educational Resources Information Center

    Farquhar, Sandy

    2016-01-01

    Time is an important driver of pedagogy which is often overlooked in the busy atmosphere of an early childhood centre. Engaging philosophically with three different concepts of time, and drawing examples from literature and art to focus attention on how time is constituted in early childhood centres, this article argues that we inhabit the…

  8. Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity.

    PubMed

    Ou, Qiang; Han, Jian; Zhang, Zhifei; Shu, Degan; Sun, Ge; Mayer, Georg

    2017-08-15

    The early Cambrian problematica Xianguangia sinica , Chengjiangopenna wangii , and Galeaplumosus abilus from the Chengjiang biota (Yunnan, China) have caused much controversy in the past and their phylogenetic placements remain unresolved. Here we show, based on exceptionally preserved material (85 new specimens plus type material), that specimens previously assigned to these three species are in fact parts of the same organism and propose that C. wangii and G. abilus are junior synonyms of X. sinica Our reconstruction of the complete animal reveals an extinct body plan that combines the characteristics of the three described species and is distinct from all known fossil and living taxa. This animal resembled a cnidarian polyp in overall morphology and having a gastric cavity partitioned by septum-like structures. However, it possessed an additional body cavity within its holdfast, an anchoring pit on the basal disk, and feather-like tentacles with densely ciliated pinnules arranged in an alternating pattern, indicating that it was a suspension feeder rather than a predatory actiniarian. Phylogenetic analyses using Bayesian inference and maximum parsimony suggest that X. sinica is a stem-group cnidarian. This relationship implies that the last common ancestor of X. sinica and crown cnidarians was probably a benthic, polypoid animal with a partitioned gastric cavity and a single mouth/anus opening. This extinct body plan suggests that feeding strategies of stem cnidarians may have been drastically different from that of their crown relatives, which are almost exclusively predators, and reveals that the morphological disparity of total-group Cnidaria is greater than previously assumed.

  9. Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity

    PubMed Central

    Ou, Qiang; Han, Jian; Zhang, Zhifei; Shu, Degan; Sun, Ge; Mayer, Georg

    2017-01-01

    The early Cambrian problematica Xianguangia sinica, Chengjiangopenna wangii, and Galeaplumosus abilus from the Chengjiang biota (Yunnan, China) have caused much controversy in the past and their phylogenetic placements remain unresolved. Here we show, based on exceptionally preserved material (85 new specimens plus type material), that specimens previously assigned to these three species are in fact parts of the same organism and propose that C. wangii and G. abilus are junior synonyms of X. sinica. Our reconstruction of the complete animal reveals an extinct body plan that combines the characteristics of the three described species and is distinct from all known fossil and living taxa. This animal resembled a cnidarian polyp in overall morphology and having a gastric cavity partitioned by septum-like structures. However, it possessed an additional body cavity within its holdfast, an anchoring pit on the basal disk, and feather-like tentacles with densely ciliated pinnules arranged in an alternating pattern, indicating that it was a suspension feeder rather than a predatory actiniarian. Phylogenetic analyses using Bayesian inference and maximum parsimony suggest that X. sinica is a stem-group cnidarian. This relationship implies that the last common ancestor of X. sinica and crown cnidarians was probably a benthic, polypoid animal with a partitioned gastric cavity and a single mouth/anus opening. This extinct body plan suggests that feeding strategies of stem cnidarians may have been drastically different from that of their crown relatives, which are almost exclusively predators, and reveals that the morphological disparity of total-group Cnidaria is greater than previously assumed. PMID:28760981

  10. Sedimentary facies of the upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: new insight on the old stormy debate

    USGS Publications Warehouse

    Eoff, Jennifer D.

    2014-01-01

    New data from detailed measured sections permit a comprehensive revision of the sedimentary facies of the Furongian (upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. Heterogeneous sandstones, comprising seven lithofacies along a depositional transect from shoreface to transitional-offshore environments, record sedimentation in a storm-dominated, shallow-marine epicontinental sea. The origin of glauconite in the Birkmose Member and Reno Member of the Lone Rock Formation was unclear, but its formation and preserved distribution are linked to inferred depositional energy rather than just net sedimentation rate. Flat-pebble conglomerate, abundant in lower Paleozoic strata, was associated with the formation of a condensed section during cratonic flooding. Hummocky cross-stratification was a valuable tool used to infer depositional settings and relative paleobathymetry, and the model describing formation of this bedform is expanded to address flow types dominant during its genesis, in particular the importance of an early unidirectional component of combined flow. The depositional model developed here for the Lone Rock Formation and Mazomanie Formation is broadly applicable to other strata common to the early Paleozoic that document sedimentation along flooded cratonic interiors or shallow shelves.

  11. Molecular clocks and the early evolution of metazoan nervous systems.

    PubMed

    Wray, Gregory A

    2015-12-19

    The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation. © 2015 The Author(s).

  12. Oxygen and Early Animal Evolution

    NASA Astrophysics Data System (ADS)

    Xiao, S.

    2012-12-01

    It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

  13. Cambrian palaeomagnetic data confirm a Natal Embayment location for the Ellsworth-Whitmore Mountains, Antarctica, in Gondwana reconstructions

    NASA Astrophysics Data System (ADS)

    Randall, Darren E.; Mac Niocaill, Conall

    2004-04-01

    The Ellsworth-Whitmore Mountains (EWM) are one of five terranes that form West Antarctica. Constraining the positions of these terranes in pre-break up Gondwana is crucial to understanding the history of the palaeo-Pacific Gondwana margin. We report the results of a detailed palaeomagnetic investigation of the EWM, which comprises some 150 sites in six formations, ranging in age from Cambrian to Permian. Five of the studied units yield only viscous remnant magnetizations of recent age, or unstable natural remanent magnetizations. The remaining unit, the mid-late Cambrian Frazier Ridge Formation, yielded stable magnetizations at 16 of 35 sites. This component passes a fold test at the 95 per cent confidence level, indicating that it pre-dates Permian deformation, and we argue that it is of primary origin. The resulting palaeopole (9°N 293°E A95= 5.1°) is in good agreement with two previously published palaeopoles from similarly aged rocks in the EWM. Collectively these data indicate that the EWM were located in the Natal Embayment prior to Gondwana break-up, and underwent 90° of anticlockwise rotation during break-up. All three studies, however, yield inclinations that are slightly too shallow when compared with coeval Gondwana reference poles.

  14. Giving the early fossil record of sponges a squeeze.

    PubMed

    Antcliffe, Jonathan B; Callow, Richard H T; Brasier, Martin D

    2014-11-01

    Twenty candidate fossils with claim to be the oldest representative of the Phylum Porifera have been re-analysed. Three criteria are used to assess each candidate: (i) the diagnostic criteria needed to categorize sponges in the fossil record; (ii) the presence, or absence, of such diagnostic features in the putative poriferan fossils; and (iii) the age constraints for the candidate fossils. All three criteria are critical to the correct interpretation of any fossil and its placement within an evolutionary context. Our analysis shows that no Precambrian fossil candidate yet satisfies all three of these criteria to be a reliable sponge fossil. The oldest widely accepted candidate, Mongolian silica hexacts from c. 545 million years ago (Ma), are here shown to be cruciform arsenopyrite crystals. The oldest reliable sponge remains are siliceous spicules from the basal Cambrian (Protohertzina anabarica Zone) Soltanieh Formation, Iran, which are described and analysed here in detail for the first time. Extensive archaeocyathan sponge reefs emerge and radiate as late as the middle of the Fortunian Stage of the Cambrian and demonstrate a gradual assembly of their skeletal structure through this time coincident with the evolution of other metazoan groups. Since the Porifera are basal in the Metazoa, their presence within the late Proterozoic has been widely anticipated. Molecular clock calibration for the earliest Porifera and Metazoa should now be based on the Iranian hexactinellid material dated to c. 535 Ma. The earliest convincing fossil sponge remains appeared at around the time of the Precambrian-Cambrian boundary, associated with the great radiation events of that interval. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

  15. Early Paleozoic paleogeography of the northern Gondwana margin: new evidence for Ordovician-Silurian glaciation

    NASA Astrophysics Data System (ADS)

    Semtner, A.-K.; Klitzsch, E.

    1994-12-01

    During the Early Paleozoic, transgressions and the distribution of sedimentary facies on the northern Gondwana margin were controlled by a regional NNW-SSE to almost north-south striking structural relief. In Early Silurian times, a eustatic highstand enabled the sea to reach its maximum southward extent. The counterclockwise rotation of Gondwana during the Cambrian and Early Ordovician caused the northern Gondwana margin to shift from intertropical to southern polar latitudes in Ordovician times. Glacial and periglacial deposits are reported from many localities in Morocco, Algeria, Niger, Libya, Chad, Sudan, Jordan and Saudi Arabia. The Late Ordovician glaciation phase was followed by a period of a major glacioeustatic sea-level rise in the Early Silurian due to the retreat of the ice-cap. As a consequence of the decreasing water circulation in the basin centers (Central Arabia, Murzuk- and Ghadames basins), highly bituminous euxinic shales were deposited. These shales are considered to be the main source rock of Paleozoic oil and gas deposits in parts of Saudi Arabia, Libya and Algeria. The following regression in the southern parts of the Early Silurian sea was probably caused by a second glacial advance, which was mainly restricted to areas in Chad, Sudan and Niger. Evidence for glacial activity and fluvioglacial sedimentation is available from rocks overlying the basal Silurian shale in north-east Chad and north-west Sudan. The Early Silurian ice advance is considered to be responsible for the termination of euxinic shale deposition in the basin centers.

  16. Detrital zircon geochronology of Neoproterozoic to Middle Cambrian miogeoclinal and platformal strata: Northwest Sonora, Mexico

    USGS Publications Warehouse

    Gross, E.L.; Stewart, John H.; Gehreis, G.E.

    2000-01-01

    Eighty-five detrital zircon grains from Mesoproterozoic and/or Neoproterozoic to Middle Cambrian sedimentary strata in northwest Sonora, Mexico, have been analyzed to determine source terranes and provide limiting depositional ages of the units. The zircon suites from the Mesoproterozoic and/or Neoproterozoic El Alamo Formation and El Aguila unit yield ages between 1.06 Ga and 2.67 Ga, with predominant ages of 1.1 to 1.2 Ga. Zircons from the Lower? and Middle Cambrian Bolsa Quartzite show age groups from 525 Ma to 1.63 Ga, with a dominant population of 1.1 to 1.2 Ga grains. Grains older than 1.2 Ga in the samples were most likely derived from basement terranes and ???1.4 Ga granitic bodies of the southwest U.S. and northwest Mexico. It is also possible that the sediments were transported from the south, although source rocks of the appropriate age are not presently exposed south of the study area in northern Mexico. Three possibilities for the dominant 1.1 to 1.2 Ga grains include derivation from: (I) exposures of the Grenville belt in southern North America, (2) local 1.1-1.2 Ga granite bodies, or (3) a southern source, such as the Oaxaca terrane, that was subsequently rifted away. Sampling of additional units in the western U.S. and northern Mexico may help resolve the ambiguity surrounding the source of the 1.1 to 1.2 Ga grains.

  17. Trace fossils and bioturbation in peritidal facies of the Potsdam-Theresa Formations (Cambrian-Ordovician), Northwest Adirondacks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bjerstedt, T.W.; Erickson, J.M.

    The Cambrian-Ordovician Potsdam Sandstone, Theresa Formation, and Canadian correlatives in the St. Lawrence Lowlands preserve tide-dominated facies during the basal Cambrian transgression. Low intertidal sand flats in the upper Potsdam contain a Skolithos Ichnofacies dominated by Diplocraterion parallelum in clean, herringbone cross-bedded sandstones indicative of high tidal current energy. Wind-wave-driven longshore and tidal currents along a macrotidal coastline were funneled northeast-southwest by Precambrian topographic relief of up to 65 m. This relief is now expressed as the Thousand Islands of New York and Canada. The conformably overlying Theresa Formation preserves a shoaling-upward sequence of mixed clastic-carbonate facies. Shallow subtidal andmore » peritidal facies contain a mixed Skolithos-Cruziana Ichnofacies in sharply alternating lithofacies consisting of gray, intensely bioturbated, poorly sorted calcareous sandstone, and meter-thick, white cross-bedded sandstone. The parallelism between ichnofacies and lithofacies indicates that environmental energy level and persistence rather than water depth controlled trace fossil distribution. Bioturbated sandstones contain a Cruziana ichnofacies of abundant deposit feeders including: Fustiglyphus , Gyrochorte , Neonereites uniserialis , Phycodes flabellum, Planolites beverlyensis, Rosselia socialis, and Teichichnus. Suspension feeders are represented by D. habichi, D. parallelum, Skolithos, Monocraterion, and possibly Palaeophycus tubularis. Scavenging or deposit-feeding arthropods are represented by rare Cruziana furrows. Cross-bedded sandstones contain a Skolithos Ichnofacies of shallow Skolithos and Monocraterion burrows, and an undescribed large epistratal eurypterid( ) trail.« less

  18. Early Paleozoic magmatic events in the eastern Klamath Mountains, northern California

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wallin, E.T.; Mattinson, J.M.; Potter, A.W.

    1988-02-01

    New U-Pb zircon ages for nine samples of tonalite and pegmatitic trondhjemite from the Trinity ophiolite and associated melange reveal a complex history of magmatic activity extending back into the earliest Cambrian, much older than previously believed. Earlier investigations, based on limited data, recognized lower Paleozoic crustal elements in the eastern Klamath terrane (EKT) ranging in age from Middle Ordovician to Early to Middle Devonian. The new work in the Yreka-Callahan area of the EKT confirms the Ordovician (440-475 Ma) and younger ages, but reveals for the first time the presence of tonalitic rocks that crystallized during a narrow timemore » interval at about 565-570 Ma. The authors also recognize younger, Late Silurian magmatism at 412 Ma. In the context of available mapping, these ages indicate that the Trinity ophiolite is broadly polygenetic because parts of it yield crystallization ages that span approximately 150 m.y. Superjacent dismembered units of probable early Paleozoic age may be tectonostratigraphically equivalent to the Sierra City melange in the northern Sierra Nevada.« less

  19. Fossils and the Evolution of the Arthropod Brain.

    PubMed

    Strausfeld, Nicholas J; Ma, Xiaoya; Edgecombe, Gregory D

    2016-10-24

    The discovery of fossilized brains and ventral nerve cords in lower and mid-Cambrian arthropods has led to crucial insights about the evolution of their central nervous system, the segmental identity of head appendages and the early evolution of eyes and their underlying visual systems. Fundamental ground patterns of lower Cambrian arthropod brains and nervous systems correspond to the ground patterns of brains and nervous systems belonging to three of four major extant panarthropod lineages. These findings demonstrate the evolutionary stability of early neural arrangements over an immense time span. Here, we put these fossil discoveries in the context of evidence from cladistics, as well as developmental and comparative neuroanatomy, which together suggest that despite many evolved modifications of neuropil centers within arthropod brains and ganglia, highly conserved arrangements have been retained. Recent phylogenies of the arthropods, based on fossil and molecular evidence, and estimates of divergence dates, suggest that neural ground patterns characterizing onychophorans, chelicerates and mandibulates are likely to have diverged between the terminal Ediacaran and earliest Cambrian, heralding the exuberant diversification of body forms that account for the Cambrian Explosion. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. The sophisticated visual system of a tiny Cambrian crustacean: analysis of a stalked fossil compound eye

    PubMed Central

    Schoenemann, Brigitte; Castellani, Christopher; Clarkson, Euan N. K.; Haug, Joachim T.; Maas, Andreas; Haug, Carolin; Waloszek, Dieter

    2012-01-01

    Fossilized compound eyes from the Cambrian, isolated and three-dimensionally preserved, provide remarkable insights into the lifestyle and habitat of their owners. The tiny stalked compound eyes described here probably possessed too few facets to form a proper image, but they represent a sophisticated system for detecting moving objects. The eyes are preserved as almost solid, mace-shaped blocks of phosphate, in which the original positions of the rhabdoms in one specimen are retained as deep cavities. Analysis of the optical axes reveals four visual areas, each with different properties in acuity of vision. They are surveyed by lenses directed forwards, laterally, backwards and inwards, respectively. The most intriguing of these is the putatively inwardly orientated zone, where the optical axes, like those orientated to the front, interfere with axes of the other eye of the contralateral side. The result is a three-dimensional visual net that covers not only the front, but extends also far laterally to either side. Thus, a moving object could be perceived by a two-dimensional coordinate (which is formed by two axes of those facets, one of the left and one of the right eye, which are orientated towards the moving object) in a wide three-dimensional space. This compound eye system enables small arthropods equipped with an eye of low acuity to estimate velocity, size or distance of possible food items efficiently. The eyes are interpreted as having been derived from individuals of the early crustacean Henningsmoenicaris scutula pointing to the existence of highly efficiently developed eyes in the early evolutionary lineage leading towards the modern Crustacea. PMID:22048954

  1. Neoproterozoic-Early Paleozoic Peri-Pacific Accretionary Evolution of the Mongolian Collage System: Insights From Geochemical and U-Pb Zircon Data From the Ordovician Sedimentary Wedge in the Mongolian Altai

    NASA Astrophysics Data System (ADS)

    Jiang, Y. D.; Schulmann, K.; Kröner, A.; Sun, M.; Lexa, O.; Janoušek, V.; Buriánek, D.; Yuan, C.; Hanžl, P.

    2017-11-01

    Neoproterozoic to early Paleozoic accretionary processes of the Central Asian Orogenic Belt have been evaluated so far mainly using the geology of ophiolites and/or magmatic arcs. Thus, the knowledge of the nature and evolution of associated sedimentary prisms remains fragmentary. We carried out an integrated geological, geochemical, and zircon U-Pb geochronological study on a giant Ordovician metasedimentary succession of the Mongolian Altai Mountains. This succession is characterized by dominant terrigenous components mixed with volcanogenic material. It is chemically immature, compositionally analogous to graywacke, and marked by significant input of felsic to intermediate arc components, pointing to an active continental margin depositional setting. Detrital zircon U-Pb ages suggest a source dominated by products of early Paleozoic magmatism prevailing during the Cambrian-Ordovician and culminating at circa 500 Ma. We propose that the Ordovician succession forms an "Altai sedimentary wedge," the evolution of which can be linked to the geodynamics of the margins of the Mongolian Precambrian Zavhan-Baydrag blocks. This involved subduction reversal from southward subduction of a passive continental margin (Early Cambrian) to the development of the "Ikh-Mongol Magmatic Arc System" and the giant Altai sedimentary wedge above a north dipping subduction zone (Late Cambrian-Ordovician). Such a dynamic process resembles the tectonic evolution of the peri-Pacific accretionary Terra Australis Orogen. A new model reconciling the Baikalian metamorphic belt along the southern Siberian Craton with peri-Pacific Altai accretionary systems fringing the Mongolian microcontinents is proposed to explain the Cambro-Ordovician geodynamic evolution of the Mongolian collage system.

  2. Seaweed morphology and ecology during the great animal diversification events of the early Paleozoic: A tale of two floras.

    PubMed

    LoDuca, S T; Bykova, N; Wu, M; Xiao, S; Zhao, Y

    2017-07-01

    Non-calcified marine macroalgae ("seaweeds") play a variety of key roles in the modern Earth system, and it is likely that they were also important players in the geological past, particularly during critical transitions such as the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE). To investigate the morphology and ecology of seaweeds spanning the time frame from the CE through the GOBE, a carefully vetted database was constructed that includes taxonomic and morphometric information for non-calcified macroalgae from 69 fossil deposits. Analysis of the database shows a pattern of seaweed history that can be explained in terms of two floras: the Cambrian Flora and the Ordovician Flora. The Cambrian Flora was dominated by rather simple morphogroups, whereas the Ordovician Flora, which replaced the Cambrian Flora in the Ordovician and extended through the Silurian, mainly comprised comparatively complex morphogroups. In addition to morphogroup representation, the two floras show marked differences in taxonomic composition, morphospace occupation, functional-form group representation, and life habit, thereby pointing to significant morphological and ecological changes for seaweeds roughly concomitant with the GOBE and the transition from the Cambrian to Paleozoic Evolutionary Faunas. Macroalgal changes of a similar nature and magnitude, however, are not evident in concert with the CE, as the Cambrian Flora consists largely of forms established during the Ediacaran. The cause of such a lag in macroalgal morphological diversification remains unclear, but an intriguing possibility is that it signals a previously unknown difference between the CE and GOBE with regard to the introduction of novel grazing pressures. The consequences of the establishment of the Ordovician Flora for shallow marine ecosystems and Earth system dynamics remain to be explored in detail but could have been multifaceted and potentially include impacts on the global

  3. Precambrian-Cambrian provenance of Matinde Formation, Karoo Supergroup, northwestern Mozambique, constrained from detrital zircon U-Pb age and Lu-Hf isotope data

    NASA Astrophysics Data System (ADS)

    Bicca, Marcos Müller; Jelinek, Andrea Ritter; Philipp, Ruy Paulo; de Carvalho Lana, Cristiano; Alkmim, Ana Ramalho

    2018-02-01

    The Permian-Triassic time interval was a period of high sedimentation rates in the intracontinental Karoo rift basin of northwestern Mozambique, reflecting high exhumation rates in the surrounding high ground Precambrian-Cambrian basement and juxtaposed nappes. U-Pb LA-MC-ICPMS dating and Lu-Hf isotopic analysis of detrital zircons from the Late Permian-Early Triassic Matinde Formation of the Karoo Supergroup is used as a reliable proxy to map denudation patterns of source regions. Data allow discrimination of U-Pb age populations of ca. 1250-900 Ma, a secondary population between ca. 900-700 and a major contribution of ages around ca. 700-490 Ma. Zircon grains of the Mesoproterozoic age population present Mesoproterozoic (1000-1500 Ma) to Paleoproterozoic (1800-2300 Ma) Hf TDM ages, with positive (0 to +11) and negative εHf values (-3 to -15), respectively. The younger U-Pb age population also presents two different groups of zircon grains according to Lu-Hf isotopes. The first group comprise Paleoproterozoic (1800-2300 Ma) ages, with highly negative εHf values, between -10 and -22, and the second group exhibits Mesoproterozoic ages (1200-1500 Ma), with increased juvenile εHf values (ca. 0 to -5). These Hf isotopes reinforce the presence of unexposed ancient crust in this region. The oldest U-Pb age population resembles the late stages of Grenville Orogeny and the Rodinia Supercontinent geotectonic activity mostly represented by magmatic rocks, which are widely present in the basement of northern Mozambique. The juvenile Hf-isotope signature with an older age component is associated to rocks generated from subduction processes with crust assimilation by continental arcs, which we correlate to rocks of the Nampula Complex, south and east of the Moatize-Minjova Basin. The U-Pb ages between 900 and 700 Ma were correlated to the calc-alkaline magmatism registered in the Guro Suite, related to the breakup phase of Rodinia, and mark the western limit of the Moatize

  4. Geology of the Sierra de Fiambala, northwestern Argentina: implications for Early Palaeozoic Andean tectonics

    USGS Publications Warehouse

    Grissom, G.C.; DeBari, S.M.; Snee, L.W.

    1998-01-01

    This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. Field mapping in conjunction with structural, metamorphic, and geochronological data document the tectono-thermal history of exhumed deep crustal rocks in the Sierra de Fiambala, NW Argentina. The range consists of two structural blocks distinguished by different metasedimentary sequences and different grades of metamorphism. Orthogneiss and paragneiss in the northern structural block may have a Precambrian history. Greenschist- to amphibolite-facies metamorphism, intrusion, and injection magmatization affected all rocks at 540-550 Ma. A subsequent event in the Late Cambrian to Ordovician (c.515 to 470 Ma) involved amphibolite- to granulite-facies metamorphism, mafic intrusion, and deformation, followed by cooling through mid-Palaeozoic time. The emplacement of Carboniferous (325-350 Ma) post-tectonic granites caused reheating and retrogression that was strongest toward the northeast part of the range. The Cambrian, Ordovician, and Carboniferous events in the Sierra de Fiambala were of regional extent as indicated by temporal correlations with events reported for other deep crustal rocks of the northern Sierras Pampeanas. Correlations between periods of intrusion and high-grade metamorphism in the northern Sierras Pampeanas and volcanic-sedimentary events in the adjacent supracrustal exposures confirm that rocks in the northern Sierras Pampeanas formed at deep (10-25 km) structural levels in the early Palaeozoic continental margin of Gondwana.

  5. Late-stage sulfides and sulfarsenides in Lower Cambrian black shale (stone coal) from the Huangjiawan mine, Guizhou Province, People's Republic of China

    USGS Publications Warehouse

    Belkin, H.E.; Luo, K.

    2008-01-01

    The Ni-Mo Huangjiawan mine, Guizhou Province, People's Republic of China, occurs in Lower Cambrian black shale (stone coal) in an area where other mines have recently extracted ore from the same horizon. Detailed electron microprobe (EMPA) and scanning electron microscope (SEM) analyses of representative thin sections have revealed a complex assemblage of sulfides and sulfarsenides. Early sulfidic and phosphatic nodules and host matrix have been lithified, somewhat fractured, and then mineralized with later-stage sulfides and sulfarsenides. Gersdorffite, millerite, polydymite, pyrite, sphalerite, chalcopyrite, galena, and clausthalite have been recognized. EMPA data are given for the major phases. Pyrite trace-element distributions and coeval Ni-, As-sulfides indicate that in the main ore layer, the last sulfide deposition was Ni-As-Co-rich. Mo and V deposition were early in the petrogenesis of these rocks. The assemblages gersdorffite-millerite-polydymite (pyrite) and millerite-gersdorffite (pyrite) and the composition of gersdorffite indicate a formation temperature of between 200?? and 300??C suggesting that the last solutions to infiltrate and mineralize the samples were related to hydrothermal processes. Environmentally sensitive elements such as As, Cd, and Se are hosted by sulfides and sulfarsenides and are the main source of these elements to residual soil. Crops grown on them are enriched in these elements, and they may be hazardous for animal and human consumption. ?? Springer-Verlag 2007.

  6. The characteristics and controlling factor of the multi-stage eogenetic karst in the Longwangmiao Foramtion in Lower Cambrian, western Central Yangtze Block, SW China

    NASA Astrophysics Data System (ADS)

    Lu, C.

    2017-12-01

    This study utilized field outcrops, thin sections, geochemical data, and GR logging curves to investigate the development model of paleokarst within the Longwangmiao Formation in the Lower Cambrian, western Central Yangtze Block, SW China. The Longwangmiao Formation, which belongs to a third-order sequence, consists of four forth-order sequences and is located in the uppermost part of the Lower Cambrian. The vertical variations of the δ13C and δ18O values indicate the existence of multi-stage eogenetic karst events. The eogenetic karst event in the uppermost part of the Longwangmiao Formation is recognized by the dripstones developed within paleocaves, vertical paleoweathering crust with four zones (bedrock, a weak weathering zone, an intense weathering zone and a solution collapsed zone), two generations of calcsparite cement showing bright luminescence and a zonation from nonluminescent to bright to nonluminescent, two types breccias (matrix-rich clast-supported chaotic breccia and matrix-supported chaotic breccia) and rundkarren. The episodic variations of stratiform dissolution vugs and breccias in vertical, and facies-controlled dissolution and filling features indicated the development of multi-stages eogenetic karst. The development of the paleokarst model is controlled by multi-level sea-level changes. The long eccentricity cycle dictates the fluctuations of the forth-order sea-level, generating multi-stage eogenetic karst events. The paleokarst model is an important step towards better understanding the link between the probably orbitally forced sea-level oscillations and eogenetic karst in the Lower Cambrian. According to this paleokarst model, hydrocarbon exploration should focus on both the karst highlands and the karst transitional zone.

  7. Unusual seismogenic soft-sediment deformation structures in Cambrian epicratonic carbonate deposits, western Colorado, U.S.A

    NASA Astrophysics Data System (ADS)

    Myrow, P.; Chen, J.

    2013-12-01

    A wide variety of unusual penecontemporaneous deformation structures exist in grainstone and flat-pebble conglomerate beds of the Upper Cambrian strata, western Colorado, including slide scarps, thrusted beds, irregular blocks and internally deformed beds. Slide scarps are characterized by concave-up, sharp surfaces that truncate one or more underlying beds. Thrusted beds record movement of a part of a bed onto itself along a moderate to steeply inclined (generally 25°-40°) ramp. The hanging wall lenses in cases show fault-bend geometries, with either intact or mildly deformed bedding. Irregular bedded to internally deformed blocks isolated on generally flat upper bedding surfaces are similar in composition to the underlying beds. These features represent parts of beds that were detached, moved up onto, and some distances across, the laterally adjacent undisturbed bed surfaces. The blocks moved either at the sediment-water interface or intrastratally at shallow depths within overlying muddy deposits. Finally, internally deformed beds have large blocks, fitted fabrics of highly irregular fragments, and contorted lamination, which represent heterogeneous deformation, such as brecciation and liquefaction. The various deformation structures were most probably triggered by earthquakes, considering the nature of deformation (regional distribution of liquefaction structures, and the brittle segmentation and subsequent transportation of semi-consolidated beds) and the reactivation of Mesoproterozoic, crustal-scale shear zones in the central Rockies during the Late Cambrian. Features produced by initial brittle deformation are unusual relative to most reported seismites, and may represent poorly recognized to unrecognized seismogenic structures in the rock record.

  8. Timing of Orphanhood, Early Sexual Debut, and Early Marriage in Four Sub-Saharan African Countries

    PubMed Central

    Chae, Sophia

    2014-01-01

    According to a growing body of literature, some orphans are at heightened risk of early sexual debut and early marriage. This study examines a rarely explored aspect of orphanhood: the timing and type of parental death and their relationship to these outcomes. The study also explores whether education mediates orphans’ risk of early sexual initiation and early marriage. The data are drawn from the 2004 National Survey of Adolescents, which includes interviews with 12–19-year-old adolescents in Burkina Faso, Ghana, Malawi, and Uganda. Results from discrete-time event history analysis indicate that female double orphans, regardless of timing of orphanhood, have greater odds of early sexual debut than do nonorphans. Education explains little of their increased risk. In contrast, male orphans of any type reveal no increased vulnerability to early sexual debut. Uganda is the only country where female orphans, specifically double orphans and those who are paternal orphans before age 10, have greater odds of early marriage, with education accounting for a small portion of the risk. PMID:23719999

  9. Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

    PubMed Central

    2012-01-01

    Background Vetulicolians are a group of Cambrian metazoans whose distinctive bodyplan continues to present a major phylogenetic challenge. Thus, we see vetulicolians assigned to groups as disparate as deuterostomes and ecdysozoans. This divergence of opinions revolves around a strikingly arthropod-like body, but one that also bears complex lateral structures on its anterior section interpreted as pharyngeal openings. Establishing the homology of these structures is central to resolving where vetulicolians sit in metazoan phylogeny. Results New material from the Chengjiang Lagerstätte helps to resolve this issue. Here, we demonstrate that these controversial structures comprise grooves with a series of openings. The latter are oval in shape and associated with a complex anatomy consistent with control of their opening and closure. Remains of what we interpret to be a musculature, combined with the capacity for the grooves to contract, indicate vetulicolians possessed a pumping mechanism that could process considerable volumes of seawater. Our observations suggest that food captured in the anterior cavity was transported to dorsal and ventral gutters, which then channeled material to the intestine. This arrangement appears to find no counterpart in any known fossil or extant arthropod (or any other ecdysozoan). Anterior lateral perforations, however, are diagnostic of deuterostomes. Conclusions If the evidence is against vetulicolians belonging to one or other group of ecdysozoan, then two phylogenetic options seem to remain. The first is that such features as vetulicolians possess are indicative of either a position among the bilaterians or deuterostomes but apart from the observation that they themselves form a distinctive and recognizable clade current evidence can permit no greater precision as to their phylogenetic placement. We argue that this is too pessimistic a view, and conclude that evidence points towards vetulicolians being members of the stem

  10. Sulfur and Carbon Isotope Systematics in Middle-Upper Cambrian Port au Port Group From Western Newfoundland, Canada: Implications for Seawater Sulfate Concentrations

    NASA Astrophysics Data System (ADS)

    Hurtgen, M. T.; Pruss, S.; Knoll, A. H.

    2006-12-01

    The biogeochemical cycles of carbon and sulfur are intimately linked through a variety of feedbacks that operate on timescales of days to millions of years. For example, under anaerobic conditions, some bacteria respire organic matter by sulfate reduction, reducing sulfate to sulfide, which then reacts with iron to form iron sulfide (preserved as pyrite). On much longer timescales, increases in the fraction of total carbon buried as organic carbon can drive increases in atmospheric oxygen concentrations which then facilitate an increase in the extent to which sulfides on land are oxidatively weathered and ultimately delivered to the oceans as sulfate via rivers. Interestingly, these two processes impose very different isotope relationships between the C isotope composition of marine dissolved inorganic carbon (DIC) and the S isotope composition of seawater sulfate. The former leads to a positive correlation between δ13Ccarbonate and δ34Ssulfate whereas the latter prescribes a long-term negative correlation. Of course, the recognition of either a positive or negative correlation between δ13Ccarbonate and δ34Ssulfate depends strongly on the relative sizes of the DIC and seawater sulfate reservoirs-- neither of which is well constrained for the Cambrian Period. Here, we present a high-resolution δ34S (sulfate and pyrite) and δ13Ccarbonate record from the mixed carbonate-siliciclastic Middle-Upper Cambrian Port au Port Group in western Newfoundland, Canada. The δ34Ssulfate profile displays systematic shifts of >15‰ over relatively short stratigraphic distances (10 m, likely to represent < 1 Myr). C isotope values shift sympathetically throughout much of the composite section; however, important deviations from this relationship exist. First, in the Middle Cambrian March Point Formation, a 15‰- δ34Ssulfate decrease precedes a 3‰-δ13Ccarbonate fall suggesting that the sulfur cycle recorded the perturbation to the system before the carbon cycle did

  11. Experimental taphonomy and the anatomy and diversity of the earliest fossil vertebrates (Chengjiang Biota, Cambrian, China)

    NASA Astrophysics Data System (ADS)

    Purnell, Mark; Gabbott, Sarah; Murdock, Duncan; Cong, Peiyun

    2016-04-01

    The oldest fossil vertebrates are from the Lower Cambrian Chengjiang biota of China, which contains four genera of fish-like, primitive vertebrates: Haikouichthys, Myllokunmingia, Zhongjianichthys and Zhongxiniscus. These fossils play key roles in calibrating molecular clocks and informing our view of the anatomy of animals close to the origin of vertebrates, potentially including transitional forms between vertebrates and their nearest relatives. Despite the evident importance of these fossils, the degree to which taphonomic processes have affected their anatomical completeness has not been investigated. For example, some or all might have been affected by stemward slippage - the pattern observed in experimental decay of non-biomineralised chordates in which preferential decay of synapomorphies and retention of plesiomorphic characters would cause fossil taxa to erroneously occupy more basal positions than they should. This hypothesis is based on experimental data derived from decay of non-biomineralised chordates under laboratory conditions. We have expanded this analysis to include a broader range of potentially significant environmental variables; we have also compared and combined the results of experiments from several taxa to identify general patterns of chordate decay. Examination of the Chengjiang vertebrates in the light of these results demonstrates that, contrary to some assertions, experimentally derived models of phylogenetic bias are applicable to fossils. Anatomical and phylogenetic interpretations of early vertebrates that do not take taphonomic biases into account risk overestimating diversity and the evolutionary significance of differences between fossil specimens.

  12. Oxygen as a driver of early arthropod micro-benthos evolution.

    PubMed

    Williams, Mark; Vannier, Jean; Corbari, Laure; Massabuau, Jean-Charles

    2011-01-01

    We examine the physiological and lifestyle adaptations which facilitated the emergence of ostracods as the numerically dominant Phanerozoic bivalve arthropod micro-benthos. The PO(2) of modern normoxic seawater is 21 kPa (air-equilibrated water), a level that would cause cellular damage if found in the tissues of ostracods and much other marine fauna. The PO(2) of most aquatic breathers at the cellular level is much lower, between 1 and 3 kPa. Ostracods avoid oxygen toxicity by migrating to waters which are hypoxic, or by developing metabolisms which generate high consumption of O(2). Interrogation of the Cambrian record of bivalve arthropod micro-benthos suggests a strong control on ecosystem evolution exerted by changing seawater O(2) levels. The PO(2) of air-equilibrated Cambrian-seawater is predicted to have varied between 10 and 30 kPa. Three groups of marine shelf-dwelling bivalve arthropods adopted different responses to Cambrian seawater O(2). Bradoriida evolved cardiovascular systems that favoured colonization of oxygenated marine waters. Their biodiversity declined during intervals associated with black shale deposition and marine shelf anoxia and their diversity may also have been curtailed by elevated late Cambrian (Furongian) oxygen-levels that increased the PO(2) gradient between seawater and bradoriid tissues. Phosphatocopida responded to Cambrian anoxia differently, reaching their peak during widespread seabed dysoxia of the SPICE event. They lacked a cardiovascular system and appear to have been adapted to seawater hypoxia. As latest Cambrian marine shelf waters became well oxygenated, phosphatocopids went extinct. Changing seawater oxygen-levels and the demise of much of the seabed bradoriid micro-benthos favoured a third group of arthropod micro-benthos, the ostracods. These animals adopted lifestyles that made them tolerant of changes in seawater O(2). Ostracods became the numerically dominant arthropod micro-benthos of the Phanerozoic. Our work

  13. Oxygen as a Driver of Early Arthropod Micro-Benthos Evolution

    PubMed Central

    Williams, Mark; Vannier, Jean; Corbari, Laure; Massabuau, Jean-Charles

    2011-01-01

    Background We examine the physiological and lifestyle adaptations which facilitated the emergence of ostracods as the numerically dominant Phanerozoic bivalve arthropod micro-benthos. Methodology/Principal Findings The PO2 of modern normoxic seawater is 21 kPa (air-equilibrated water), a level that would cause cellular damage if found in the tissues of ostracods and much other marine fauna. The PO2 of most aquatic breathers at the cellular level is much lower, between 1 and 3 kPa. Ostracods avoid oxygen toxicity by migrating to waters which are hypoxic, or by developing metabolisms which generate high consumption of O2. Interrogation of the Cambrian record of bivalve arthropod micro-benthos suggests a strong control on ecosystem evolution exerted by changing seawater O2 levels. The PO2 of air-equilibrated Cambrian-seawater is predicted to have varied between 10 and 30 kPa. Three groups of marine shelf-dwelling bivalve arthropods adopted different responses to Cambrian seawater O2. Bradoriida evolved cardiovascular systems that favoured colonization of oxygenated marine waters. Their biodiversity declined during intervals associated with black shale deposition and marine shelf anoxia and their diversity may also have been curtailed by elevated late Cambrian (Furongian) oxygen-levels that increased the PO2 gradient between seawater and bradoriid tissues. Phosphatocopida responded to Cambrian anoxia differently, reaching their peak during widespread seabed dysoxia of the SPICE event. They lacked a cardiovascular system and appear to have been adapted to seawater hypoxia. As latest Cambrian marine shelf waters became well oxygenated, phosphatocopids went extinct. Changing seawater oxygen-levels and the demise of much of the seabed bradoriid micro-benthos favoured a third group of arthropod micro-benthos, the ostracods. These animals adopted lifestyles that made them tolerant of changes in seawater O2. Ostracods became the numerically dominant arthropod micro-benthos of

  14. Paired δ34S data from carbonate-associated sulfate and chromium-reducible sulfur across the traditional Lower-Middle Cambrian boundary of W-Gondwana

    NASA Astrophysics Data System (ADS)

    Wotte, Thomas; Strauss, Harald; Fugmann, Artur; Garbe-Schönberg, Dieter

    2012-05-01

    In this study, we present the first high-resolution data from coupled δ34S analyses of carbonate-associated sulfate (CAS) and chromium-reducible sulfur (CRS) from three Lower-Middle Cambrian sections in western Gondwana. CAS and CRS were extracted and analyzed from marine dolostone, limestone, and nodular limestone from Spanish and French successions. In parallel, carbonate samples were also analyzed for δ13Ccarb, δ18Ocarb, and major/trace element concentrations (Ca, Fe, Mg, Mn, Sr). δ34SCAS values vary between 17.6‰ and 33.2‰, with a maximum CAS concentration of ca. 900 ppm. δ34SCRS data show a similar broad range between -5.1‰ and 29.7‰, with maximal CRS contents up to ca. 3700 ppm. Notably, there is little stratigraphic variation in the δ34SCAS data in each of the sections confounding inter-basinal chemostratigraphic correlations. Nonetheless, the absolute differences in δ34SCAS between sections as well as variations in CAS and CRS concentrations are attributed to paleoenvironmental differences between proximal and distal parts of the carbonate ramp, as well as effects of subaerial exposure and riverine input. Thus, the generated δ34SCAS data deliver not only valuable paleoecological and paleoenvironmental information, they also illustrate a heterogeneity in the seawater sulfate sulfur isotopic composition of the western Gondwanan ocean. Consequently, the lack of correlation between our Gondwanan δ34SCAS data and time equivalent sections of Laurentia and Siberia is probably not only caused by the absence of an internationally accepted biostratigraphic correlation, but rather supports the view that sulfate was non-conservative anion in seawater during the Cambrian Period.

  15. The evolution of the passive continental margin of Norway and its adjacent mainland - using the sub-Cambrian peneplain as a reference surface.

    NASA Astrophysics Data System (ADS)

    Gabrielsen, R. H.; Faleide, J. I.; Jarsve, E. M.

    2012-04-01

    The structuring, uplift and subsidence of the passive margin and shelf of Norway and its adjacent mainland were affected by several profound geological processes, including inherited basement structural grain related to the Proterozoic and Caledonian orogens and also including the extensional collapse of the Caledonides (Gabrielsen et al. 2000). This has been followed by several stages of late Palaoezoic - Cenozoic rifting and associated thermotectonic activity, Cenozoic accelerated uplift of uncertain origin of the hinterland, creating an irregular pattern of upheaval and, finally Pleistocene - Holocene glacial loading and unloading (Gabrielsen et al. 2010). These processes have strongly influenced the topography of the hinterland, thus causing and acting in concert with climate fluctuations (Nielsen et al. 2009). The correlation of erosional surfaces of regional significance on the shelf and on the mainland is a key to the evaluating the total topography of the margin. Because of the lack of datable surfaces on the mainland, this is problematic. The so-called Paleic surface has been used in this context, but its age and nature is not well constrained and the absence of post-Caledonian rocks in the western and central mainland of southern Norway adds to this complexity. In contrast, the sub-Cambrian peneplain, which is found in larger parts of Scandinavia, is well established when it comes to dating and development (e.g. Strøm 1948). It is generally accepted that this surface had only a minor topography, if any, throughout Scandinavia at the earliest Cambrian. Hence, its present relief is the result of the accumulated vertical displacements from the Caledonian to the Present. Still, even though it was well established through regional mapping already in the late 19th century, much remains in the detailed documentation of this important surface. To improve the topographic accuracy in its characterization, fieldwork has been initiated to establish a detailed WNW

  16. Cambrian nepheline syenite complex at Jabal Sawda, Midyan region, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Liddicoat, W.K.; Ramsay, C.R.; Hedge, C.E.

    1986-01-01

    The only nepheline syenite complex presently known in the Arabian Shield is at Jabal Sawda, about 30 km S of Haql in the extreme NW of Saudi Arabia. It is a post-tectonic, composite intrusion with a crudely concentric structure. A core of leuco-nepheline syenite, a partial ring of mela-nepheline syenite, and an almost complete outer ring of alkali-feldspar syenite are the main rock units. Several mega-inclusions of porphyritic nepheline syenite, nepheline monzosyenite, malignite and ijolite are present in the leuco-nepheline syenite. The chemical composition is notable for very high values of Al2O3, Na2O, Ba, La, Nb, Sr and Zr. U{single bond}Pb isotope dating indicates an emplacement age of 553 ?? 4 Ma, one of an increasing number of reliable Cambrian isotope dates in the northern Red Sea region. ?? 1986.

  17. Cambrian nepheline syenite complex at Jabal Sawda, Midyan region, Kingdom of Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Liddicoat, W. K.; Ramsay, C. R.; Hedge, C. E.

    The only nepheline syenite complex presently known in the Arabian Shield is at Jabal Sawda, about 30 km S of Haql in the extreme NW of Saudi Arabia. It is a post-tectonic, composite intrusion with a crudely concentric structure. A core of leuco-nepheline syenite, a partial ring of mela-nepheline syenite, and an almost complete outer ring of alkali-feldspar syenite are the main rock units. Several mega-inclusions of porphyritic nepheline syenite, nepheline monzosyenite, malignite and ijolite are present in the leuco-nepheline syenite. The chemical composition is notable for very high values of Al 2O 3, Na 2O, Ba, La, Nb, Sr and Zr. U sbnd Pb isotope dating indicates an emplacement age of 553 ± 4 Ma, one of an increasing number of reliable Cambrian isotope dates in the northern Red Sea region.

  18. Timely Healthcare Checkup Catches Melanoma Early

    MedlinePlus

    ... please turn Javascript on. Feature: Skin Cancer Timely Healthcare Checkup Catches Melanoma Early Past Issues / Summer 2013 ... left the Congress and starting working as a healthcare consultant, when I finally decided to have a ...

  19. Cause of Cambrian Explosion - Terrestrial or Cosmic?

    PubMed

    Steele, Edward J; Al-Mufti, Shirwan; Augustyn, Kenneth A; Chandrajith, Rohana; Coghlan, John P; Coulson, S G; Ghosh, Sudipto; Gillman, Mark; Gorczynski, Reginald M; Klyce, Brig; Louis, Godfrey; Mahanama, Kithsiri; Oliver, Keith R; Padron, Julio; Qu, Jiangwen; Schuster, John A; Smith, W E; Snyder, Duane P; Steele, Julian A; Stewart, Brent J; Temple, Robert; Tokoro, Gensuke; Tout, Christopher A; Unzicker, Alexander; Wainwright, Milton; Wallis, Jamie; Wallis, Daryl H; Wallis, Max K; Wetherall, John; Wickramasinghe, D T; Wickramasinghe, J T; Wickramasinghe, N Chandra; Liu, Yongsheng

    2018-08-01

    We review the salient evidence consistent with or predicted by the Hoyle-Wickramasinghe (H-W) thesis of Cometary (Cosmic) Biology. Much of this physical and biological evidence is multifactorial. One particular focus are the recent studies which date the emergence of the complex retroviruses of vertebrate lines at or just before the Cambrian Explosion of ∼500 Ma. Such viruses are known to be plausibly associated with major evolutionary genomic processes. We believe this coincidence is not fortuitous but is consistent with a key prediction of H-W theory whereby major extinction-diversification evolutionary boundaries coincide with virus-bearing cometary-bolide bombardment events. A second focus is the remarkable evolution of intelligent complexity (Cephalopods) culminating in the emergence of the Octopus. A third focus concerns the micro-organism fossil evidence contained within meteorites as well as the detection in the upper atmosphere of apparent incoming life-bearing particles from space. In our view the totality of the multifactorial data and critical analyses assembled by Fred Hoyle, Chandra Wickramasinghe and their many colleagues since the 1960s leads to a very plausible conclusion - life may have been seeded here on Earth by life-bearing comets as soon as conditions on Earth allowed it to flourish (about or just before 4.1 Billion years ago); and living organisms such as space-resistant and space-hardy bacteria, viruses, more complex eukaryotic cells, fertilised ova and seeds have been continuously delivered ever since to Earth so being one important driver of further terrestrial evolution which has resulted in considerable genetic diversity and which has led to the emergence of mankind. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Les microbialites de l'Anti-Atlas occidental (Maroc) : marqueurs stratigraphiques et témoins des changements environnementaux au Cambrien inférieur Stratigraphic and environmental significance of the Lower-Cambrian western Anti-Atlasic microbialites (Morocco)

    NASA Astrophysics Data System (ADS)

    Benssaou, Mohammed; Hamoumi, Naima

    2004-02-01

    Three microbialite forms are recognized in the Lower-Cambrian succession of Irherm area in the western Anti-Atlas (Morocco). Stromatolites, which correspond to non-calcified shallow marine laminated microbialites, are well developed in the basal Lower-Cambrian succession. Occurrence of calcified microbial thrombolites, in the middle part of this succession, reflects an increasing sea level from the peritidal zone to the subtidal environment. In the upper part of this succession, a second increasing water depth event and the development of branching archaeocyathan reefal framework lead to dendritic microbialite emergence. To cite this article: M. Benssaou, N. Hamoumi, C. R. Geoscience 336 (2004).

  1. Black shale source rocks and oil generation in the Cambrian and Ordovician of the central Appalachian Basin, USA

    USGS Publications Warehouse

    Ryder, R.T.; Burruss, R.C.; Hatch, J.R.

    1998-01-01

    Nearly 600 million bbl of oil (MMBO) and 1 to 1.5 trillion ft3 (tcf) of gas have been produced from Cambrian and Ordovician reservoirs (carbonate and sandstone) in the Ohio part of the Appalachian basin and on adjoining arches in Ohio, Indiana, and Ontario, Canada. Most of the oil and gas is concentrated in the giant Lima-Indiana field on the Findlay and Kankakee arches and in small fields distributed along the Knox unconformity. Based on new geochemical analyses of oils, potential source rocks, bitumen extracts, and previously published geochemical data, we conclude that the oils in both groups of fields originated from Middle and Upper Ordovician blcak shale (Utica and Antes shales) in the Appalachian basin. Moroever, we suggest that approximately 300 MMBO and many trillions of cubic feet of gas in the Lower Silurian Clinton sands of eastern Ohio originated in the same source rocks. Oils from the Cambrian and Ordovician reservoirs have similar saturated hydrocarbon compositions, biomarker distributions, and carbon isotope signatures. Regional variations in the oils are attributed to differences in thermal maturation rather than to differences in source. Total organic carbon content, genetic potential, regional extent, and bitument extract geochemistry identify the balck shale of the Utica and Antes shales as the most plausible source of the oils. Other Cambrian and Ordovician shale and carbonate units, such as the Wells Creek formation, which rests on the Knox unconformity, and the Rome Formation and Conasauga Group in the Rome trough, are considered to be only local petroleum sources. Tmax, CAI, and pyrolysis yields from drill-hole cuttings and core indicate that the Utica Shale in eastern and central Ohio is mature with respect to oil generation. Burial, thermal, and hydrocarbon-generation history models suggest that much of the oil was generated from the Utica-Antes source in the late Paleozoic during the Alleghanian orogeny. A pervasive fracture network

  2. The Late Cambrian SPICE (δ13C) event and the Sauk II-Sauk III regression: new evidence from Laurentian basins in Utah, Iowa, and Newfoundland

    USGS Publications Warehouse

    Saltzman, Matthew R.; Cowan, Clinton A.; Runkel, Anthony C.; Runnegar, Bruce; Stewart, Michael C.; Palmer, Allison R.

    2004-01-01

    Carbon isotope data from Upper Cambrian sections in three Laurentian basins in northern Utah, central Iowa, and western Newfoundland record a large positive ??13C excursion (SPICE event) of up to + 5???. Peak ??13C ratios are well dated by trilobite collections to the middle of the Steptoean Stage (Dunderbergia Zone) and occur during maximum regression associated with formation of the Sauk II-Sauk III subsequence boundary on the North American craton. Maximum regression was marked by an influx of quartz sand into carbonate-platform settings in all three widely separated basins. In northern Utah, this quartz sand formed a thick sequence known as the Worm Creek Quartzite, which marks a conspicuous interruption of carbonate deposition during the Middle to Late Cambrian in the region. In western Newfoundland, the thickness of the quartz sand unit is much reduced but still marks a brief shutdown of the carbonate factory that is unique to the Cambrian shelf succession of the area. In the central Iowa area of the cratonic interior, an upward-shallowing carbonate succession culminates in cross-stratified trilobite grainstones at the peak of the SPICE in Dunderbergia Zone time, and the lowest point on the relative-sea-level curve is associated with the occurrence of coarse quartz sand derived from the encroaching shoreface. Although it is difficult to determine precisely the departure from baseline ??13C that marks the beginning of the SPICE excursion in the stratigraphic successions analyzed, our results are consistent with a rise and subsequent fall in ??13C tracking a major regressive-transgressive event recorded across northern Laurentia. The correlation of a major ??13C excursion with regression is similar to that described for the Late Ordovician, for which the pattern has been attributed to either increased carbonate relative to terrigenous weathering rates as ice sheets covered up organic-matter-containing silicates at high latitudes or high productivity and organic

  3. Suspected microbial-induced sedimentary structures (MISS) in Furongian (Upper Cambrian; Jiangshanian, Sunwaptan) strata of the Upper Mississippi Valley

    USGS Publications Warehouse

    Eoff, Jennifer D.

    2014-01-01

    The Furongian (Upper Cambrian; Jiangshanian and Sunwaptan) Tunnel City Group (Lone Rock Formation and Mazomanie Formation), exposed in Wisconsin and Minnesota, represents a shallow-marine clastic environment during a time of exceptionally high sea level. Lithofacies from shoreface to transitional-offshore settings document deposition in a wave- and storm-dominated sea. Flooding of the cratonic interior was associated with formation of a condensed section and the extensive development of microbial mats. Biolamination, mat fragments, wrinkle structures, and syneresis cracks are preserved in various sandstone facies of the Lone Rock Formation, as is evidence for the cohesive behavior of sand. These microbial-induced sedimentary structures (MISS) provide unique signals of biological–physical processes that physical structures alone cannot mimic. The MISS are associated with a trilobite extinction event in the Steptoean–Sunwaptan boundary interval. This may support recent claims that Phanerozoic microbial mats were opportunistic disaster forms that flourished during periods of faunal turnover. Further investigation of stratigraphic, taphonomic, and other potential biases, however, is needed to fully test this hypothesis.

  4. Geohydrologic systems in Kansas with emphasis on systems in Upper Cambrian through Lower Cretaceous rocks

    USGS Publications Warehouse

    Wolf, R.J.; Hansen, C.V.; McGovern, H.E.; Spinazola, J.M.

    1990-01-01

    This Hydrologic Investigations Atlas, which consists of a series of chapters, presents a description of (1) the physical frameworks and (2) the geohydrology of the principal aquifers and confining systems in Kansas. The report is the result of an investigation that has been made as part of the Central Midwest Regional Aquifer System Analysis (CMRASA), one of several major investigations by the U.S. Geological Survey to define regional aquifer systems. These regional analyses are designed to increase knowledge of major flow regimes and provide data for assessing, developing, and managing water supplies. The CMRASA is an investigation of water in Upper Cambrian through Lower Cretaceous rocks in parts of 10 Central Midwestern States, as shown by the map on the envelope cover.

  5. Sequence stratigraphy of the Upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: Transgressing assumptions of cratonic flooding

    USGS Publications Warehouse

    Eoff, Jennifer D.

    2014-01-01

    New data from detailed measured sections permit comprehensive analysis of the sequence framework of the Furongian (Upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. The sequence-stratigraphic architecture of the lower part of the Sunwaptan Stage at the base of the Tunnel City Group, at the contact between the Wonewoc Formation and Lone Rock Formation, records the first part of complex polyphase flooding (Sauk III) of the Laurentian craton, at a scale smaller than most events recorded by global sea-level curves. Flat-pebble conglomerate and glauconite document transgressive ravinement and development of a condensed section when creation of accommodation exceeded its consumption by sedimentation. Thinly-bedded, fossiliferous sandstone represents the most distal setting during earliest highstand. Subsequent deposition of sandstone characterized by hummocky or trough cross-stratification records progradational pulses of shallower, storm- and wave-dominated environments across the craton before final flooding of Sauk III commenced with carbonate deposition during the middle part of the Sunwaptan Stage. Comparison of early Sunwaptan flooding of the inner Laurentian craton to published interpretations from other parts of North America suggests that Sauk III was not a single, long-term accommodation event as previously proposed.

  6. Paleoecology and paleoceanography of the Athel silicilyte, Ediacaran-Cambrian boundary, Sultanate of Oman.

    PubMed

    Stolper, D A; Love, G D; Bates, S; Lyons, T W; Young, E; Sessions, A L; Grotzinger, J P

    2017-05-01

    The Athel silicilyte is an enigmatic, hundreds of meters thick, finely laminated quartz deposit, in which silica precipitated in deep water (>~100-200 m) at the Ediacaran-Cambrian boundary in the South Oman Salt Basin. In contrast, Meso-Neoproterozoic sinks for marine silica were dominantly restricted to peritidal settings. The silicilyte is known to contain sterane biomarkers for demosponges, which today are benthic, obligately aerobic organisms. However, the basin has previously been described as permanently sulfidic and time-equivalent shallow-water carbonate platform and evaporitic facies lack silica. The Athel silicilyte thus represents a unique and poorly understood depositional system with implications for late Ediacaran marine chemistry and paleoecology. To address these issues, we made petrographic observations, analyzed biomarkers in the solvent-extractable bitumen, and measured whole-rock iron speciation and oxygen and silicon isotopes. These data indicate that the silicilyte is a distinct rock type both in its sedimentology and geochemistry and in the original biology present as compared to other facies from the same time period in Oman. The depositional environment of the silicilyte, as compared to the bounding shales, appears to have been more reducing at depth in sediments and possibly bottom waters with a significantly different biological community contributing to the preserved biomarkers. We propose a conceptual model for this system in which deeper, nutrient-rich waters mixed with surface seawater via episodic mixing, which stimulated primary production. The silica nucleated on this organic matter and then sank to the seafloor, forming the silicilyte in a sediment-starved system. We propose that the silicilyte may represent a type of environment that existed elsewhere during the Neoproterozoic. These environments may have represented an important locus for silica removal from the oceans. © 2017 John Wiley & Sons Ltd.

  7. Water-quality assessment of the Cambrian-Ordovician aquifer system in the northern Midwest, United States

    USGS Publications Warehouse

    Wilson, John T.

    2012-01-01

    This report provides a regional assessment of groundwater quality of the Cambrian-Ordovician aquifer system, based primarily on raw water samples collected by the NAWQA Program during 1995 through 2007. The NAWQA Program has published findings in local study-unit reports encompassing parts of the Cambrian-Ordovician aquifer system. Data collected from the aquifer system were used in national synthesis reports on selected topics such as specific water-quality constituent classes, well type, or aquifer material; however, a synthesis of groundwater quality at the principal aquifer scale has not been completed and is therefore the major purpose of this report. Water samples collected by the NAWQA Program were analyzed for various classes of characteristics including physical properties, major ions, trace elements, nutrients and dissolved organic carbon, radionuclides (tritium, radon, and radium), pesticides, and volatile organic compounds. Subsequent sections of this report provide discussions on these classes of characteristics. The assessment objectives of this report are to (1) summarize constituent concentrations and compare them to human-health benchmarks and non-health guidelines; (2) determine the geographic distribution of constituent concentrations and relate them to various factors such as confining conditions, well type, land use, and groundwater age; and (3) evaluate near-decadal-scale changes in nitrate concentrations and pesticide detections. The most recent sample collected from each well by the NAWQA Program was used for most analyses. Near-decadal-scale changes in nitrate concentrations and pesticide detections were evaluated for selected well networks by using the most recent sample from each well and comparing it to the results from a sample collected 7 or 11 years earlier. Because some of the NAWQA well networks provide a limited areal coverage of the aquifer system, data for raw water samples from other USGS sources and state agencies were included

  8. Cambrian–Ordovician of the central Appalachians:Correlations and event stratigraphy of carbonate platform andadjacent deep-water deposits

    USGS Publications Warehouse

    Brezinski, David K.; Taylor, John F.; Repetski, John E.; Loch, James D.

    2015-01-01

    deposited within the Pennsylvania and Maryland portion of the Great American Carbonate Bank. From the Early Cambrian (Dyeran) through Late Ordovician (Turinan), the Laurentian paleocontinent was rimmed by an extensive carbonate platform. During this protracted period of time, a succession of carbonate rock, more than two miles thick, was deposited in Maryland and Pennsylvania. These strata are now exposed in the Nittany arch of central Pennsylvania; the Great Valley of Pennsylvania, Maryland, and Virginia; and the Conestoga and Frederick Valleys of eastern Pennsylvania and Maryland. This fi eld trip will visit key outcrops that illustrate the varied depositional styles and environmental settings that prevailed at different times within the Pennsylvania reentrant portion of the Great American Carbonate Bank. In particular, we will contrast the timing and pattern of sedimentation in off-shelf (Frederick Valley), outer-shelf (Great Valley), and inner-shelf (Nittany arch) deposits. The deposition was controlled primarily by eustasy through the Cambrian and Early Ordovician (within the Sauk megasequence), but was strongly infl uenced later by the onset of Taconic orogenesis during deposition of the Tippecanoe megasequence.

  9. Early Earth(s) Across Time and Space

    NASA Astrophysics Data System (ADS)

    Mojzsis, S.

    2014-04-01

    The geochemical and cosmochemical record of our solar system is the baseline for exploring the question: "when could life appear on a world similar to our own?" Data arising from direct analysis of the oldest terrestrial rocks and minerals from the first 500 Myr of Earth history - termed the Hadean Eon - inform us about the timing for the establishment of a habitable silicate world. Liquid water is the key medium for life. The origin of water, and its interaction with the crust as revealed in the geologic record, guides our exploration for a cosmochemically Earth-like planets. From the time of primary planetary accretion to the start of the continuous rock record on Earth at ca. 3850 million years ago, our planet experienced a waning bolide flux that partially or entirely wiped out surface rocks, vaporized oceans, and created transient serpentinizing atmospheres. Arguably, "Early Earths" across the galaxy may start off as ice planets due to feeble insolation from their young stars, occasionally punctuated by steam atmospheres generated by cataclysmic impacts. Alternatively, early global environments conducive to life spanned from a benign surface zone to deep into crustal rocks and sediments. In some scenarios, nascent biospheres benefit from the exogenous delivery of essential bio-elements via leftovers of accretion, and the subsequent establishment of planetary-scale hydrothermal systems. If what is now known about the early dynamical regime of the Earth serves as any measure of the potential habitability of worlds across space and time, several key boundary conditions emerge. These are: (i) availability and long-term stability of liquid water; (ii) presence of energy resources; (iii) accessibility of organic raw materials; (iv) adequate inventory of radioisotopes to drive internal heating; (v) gross compositional parameters such as mantle/core mass ratio, and (vi) P-T conditions at or near the surface suitable for sustaining biological activity. Life could

  10. How Do Early Career Agriculture Teachers Talk about Their Time?

    ERIC Educational Resources Information Center

    Lambert, Misty D.; Henry, Anna L.; Tummons, John D.

    2011-01-01

    This phenomenological study of early career agriculture teachers sought to determine the meaning early career agriculture teachers ascribe to their time. Seven teachers with a range of experience from mid-first year to beginning of sixth year were chosen. Interviews were used to make meaning of their time. Five themes were found in the…

  11. Influence of first-time mothers' early employment on severe early childhood caries in their child.

    PubMed

    Plutzer, Kamila; Keirse, Marc J N C

    2012-01-01

    Aim. To examine whether mothers' early employment status is related to the development of severe early childhood caries in their child. Methods. Questionnaire survey of 429 first-time mothers in metropolitan Adelaide, South Australia, and dental examinations of their child at 20 months of age. Results. At 20 ± 2.5 months of age, 5.6% of children exhibited caries defined as one or more demineralized or cavitated lesions on the upper incisors. Of the mothers, 52.2% had no paid employment, 39.6% were part-time and 8.2% full-time employed. Overall, mothers' participation in the workforce had no influence on the frequency of severe early childhood caries in their child, but there was a significant interaction with family structure. For mothers without employment there was no difference between single, and two-parent families, but children with an employed single mother more frequently had caries than those with a working mother in a two-parent family (P < 0.04). However, there were no significant differences in children's reported general health. Conclusions. The data indicate a need to explore strategies that may assist single mothers and especially those in the workforce to prevent severe early childhood caries in their child.

  12. A stem-group cnidarian described from the mid-Cambrian of China and its significance for cnidarian evolution.

    PubMed

    Park, Tae-yoon; Woo, Jusun; Lee, Dong-Jin; Lee, Dong-Chan; Lee, Seung-bae; Han, Zuozhen; Chough, Sung Kwun; Choi, Duck K

    2011-08-23

    Palaeontological data of extinct groups often sheds light on the evolutionary sequences leading to extant groups, but has failed to resolve the basal metazoan phylogeny including the origin of the Cnidaria. Here we report the occurrence of a stem-group cnidarian, Cambroctoconus orientalis gen. et sp. nov., from the mid-Cambrian of China, which is a colonial organism with calcareous octagonal conical cup-shaped skeletons. It bears cnidarian features including longitudinal septa arranged in octoradial symmetry and colonial occurrence, but lacks a jelly-like mesenchyme. Such morphological characteristics suggest that the colonial occurrence with polyps of octoradial symmetry is the plesiomorphic condition of the Cnidaria and appeared earlier than the jelly-like mesenchyme during the course of evolution. © 2011 Macmillan Publishers Limited. All rights reserved.

  13. A stem-group cnidarian described from the mid-Cambrian of China and its significance for cnidarian evolution

    PubMed Central

    Park, Tae-yoon; Woo, Jusun; Lee, Dong-Jin; Lee, Dong-Chan; Lee, Seung-bae; Han, Zuozhen; Chough, Sung Kwun; Choi, Duck K.

    2011-01-01

    Palaeontological data of extinct groups often sheds light on the evolutionary sequences leading to extant groups, but has failed to resolve the basal metazoan phylogeny including the origin of the Cnidaria. Here we report the occurrence of a stem-group cnidarian, Cambroctoconus orientalis gen. et sp. nov., from the mid-Cambrian of China, which is a colonial organism with calcareous octagonal conical cup-shaped skeletons. It bears cnidarian features including longitudinal septa arranged in octoradial symmetry and colonial occurrence, but lacks a jelly-like mesenchyme. Such morphological characteristics suggest that the colonial occurrence with polyps of octoradial symmetry is the plesiomorphic condition of the Cnidaria and appeared earlier than the jelly-like mesenchyme during the course of evolution. PMID:21863009

  14. Geology and lithogeochemistry of hydrothermal mudstones from the upper block near the Duck Pond volcanogenic massive sulfide (VMS) deposit, Newfoundland, Canada: evidence for low-temperature venting into oxygenated mid-Cambrian seawater

    NASA Astrophysics Data System (ADS)

    Piercey, Stephen J.; Squires, Gerry; Brace, Terry

    2018-02-01

    Pyrite- and pyrrhotite-rich mudstones are spatially associated with Cambrian ( 512-509 Ma) volcanogenic massive sulfide (VMS) deposits throughout the Tally Pond group, central Newfoundland, Canada. At the Duck Pond mine, sulfide-rich mudstones are hosted within a weakly mineralized upper block that structurally overlies the deposit but is older ( 513 versus 509 Ma). The mudstones are laminated, 10-30-cm thick, and pyrite- and pyrrhotite-rich and occur along pillow lava selvages, or in between pillow lavas, rhyolite flows, and volcaniclastic rocks. The mudstones are laterally extensive and proximal to the mudstone host rocks are hydrothermally altered to epidote-quartz-chlorite (basalt host) and sericite-quartz (rhyolite host). Lithogeochemical data for the sulfide-rich mudstones reflect the varying contributions of elements from sedimentary detritus, hydrothermal discharge, and hydrogenous scavenging from middle Cambrian seawater. The mudstones have minor detrital element abundances and significant hydrothermal element enrichments (i.e., elevated Fe2O3, S, Pb, Zn, Cu, and Ba concentrations, high Fe/Al ratios). The hydrothermal mudstones are also enriched in oxyanions (i.e., P2O5, U, V, Cr, Ni, Co, and Hg), interpreted to have been enriched via oxidative scavenging from seawater by Fe-oxide/oxyhydroxide particles. The mudstones also have REE-Y signatures similar to modern oxygenated seawater with high Y/Ho and negative Ce anomalies (Ce/Ce* = 0.40-0.86; average = 0.58), which correlate with adsorbed oxyanion concentrations. The low Eu/Eu* (1.02-1.86; average = 1.22) in the mudstones suggest that they were deposited from low-temperature (< 250 °C), Fe-rich hydrothermal fluids that likely formed a buoyant plume into an oxygenated water column. The REE-Y-oxyanion signatures suggest that the particles within the hydrothermal plume had sufficient residence time to scavenge oxyanions from seawater and inherit a middle Cambrian seawater signature. The predominant seawater

  15. Cambrian-Ordovician Knox production in Ohio: Three case studies of structural-stratigraphic traps

    USGS Publications Warehouse

    Riley, R.A.; Wicks, J.; Thomas, Joan

    2002-01-01

    The Knox Dolomite (Cambrian-Ordovician) in Ohio consists of a mixed carbonate-siliciclastic sequence deposited in a tidal-flat to shallow-marine environment along a broad continental shelf. Knox hydrocarbon production occurs in porous sandstone and dolomite reservoirs in the Copper Ridge dolomite, Rose Run sandstone, and Beekmantown dolomite. In Ohio, historical Knox exploration and development have been focused on paleogeomorphic traps within the prolific Morrow Consolidated field, and more recently, within and adjacent to the Rose Run subcrop. Although these paleogeomorphic traps have yielded significant Knox production, structural and stratigraphic traps are being largely ignored. Three Knox-producing pools demonstrate structural and stratigraphic traps: the Birmingham-Erie pool in southern Erie and southwestern Lorain counties, the South Canaan pool in northern Wayne County, and the East Randolph pool in south-central Portage County. Enhanced porosity and permeability from fractures, as evident in the East Randolph pool, are also an underexplored mechanism for Knox hydrocarbon accumulation. An estimated 800 bcf of gas from undiscovered Knox resources makes the Knox one of the most attractive plays in the Appalachian basin.

  16. Proposed stratotype for the base of the highest Cambrian stage at the first appearance datum of Cordylodus andresi, Lawson Cove section, Utah, USA

    USGS Publications Warehouse

    Miller, J.F.; Ethington, Raymond L.; Evans, K.R.; Holmer, L.E.; Loch, James D.; Popov, L.E.; Repetski, J.E.; Ripperdan, R.L.; Taylor, John F.

    2006-01-01

    We propose a candidate for the Global Standard Stratotype-section and Point (GSSP) for the base of the highest stage of the Furongian Series of the Cambrian System. The section is at Lawson Cove in the Ibex area of Millard County, Utah, USA. The marker horizon is the first appearance datum (FAD) of the conodont Cordylodus andresi Viira et Sergeyeva in Kaljo et al. [Kaljo, D., Borovko, N., Heinsalu, H., Khazanovich, K., Mens, K., Popov, L., Sergeyeva, S., Sobolevskaya, R., Viira, V., 1986. The Cambrian-Ordovician boundary in the Baltic-Ladoga clint area (North Estonia and Leningrad Region, USSR). Eesti NSV Teaduste Akadeemia Toimetised. Geologia 35, 97-108]. At this section and elsewhere this horizon also is the FAD of the trilobite Eurekia apopsis (Winston et Nicholls, 1967). This conodont characterizes the base of the Cordylodus proavus Zone, which has been recognized in many parts of the world. This trilobite characterizes the base of the Eurekia apopsis Zone, which has been recognized in many parts of North America. The proposed boundary is 46.7 m above the base of the Lava Dam Member of the Notch Peak Formation at the Lawson Cove section. Brachiopods, sequence stratigraphy, and carbon-isotope geochemistry are other tools that characterize this horizon and allow it to be recognized in other areas. ?? 2006 Nanjing Institute of Geology and Palaeontology, CAS.

  17. First data on age of metarhyolites from the Turan Group of the Bureya Terrane, eastern part of the Central Asian Foldbelt

    NASA Astrophysics Data System (ADS)

    Sorokin, A. A.; Smirnov, Yu. V.; Smirnova, Yu. N.; Kudryashov, N. M.

    2011-07-01

    The U-Pb geochronological studies showed that metarhyolites from the Turan Group of the Bureya (Turan) Terrane to the east of the Central Asian Foldbelt are Middle Cambrian (504 ± 8 Ma), not Neoproterozoic in age, as was suggested before. Metarhyolites are younger than the Early Cambrian terrigenous-carbonate sediments from this terrane characterized by the Atdabanian archaeochyatid. Considering that volcanic rocks have features of intraplate origin, it may be assumed that their formation corresponds to the breakup of the Early Paleozoic passive continental margin.

  18. Sedimentology of SPICE (Steptoean positive carbon isotope excursion): A high-resolution trace fossil and microfabric analysis of the middle to late Cambrian Alum Shale Formation, southern Sweden

    USGS Publications Warehouse

    Egenhoff, Sven; Fishman, Neil; Ahlberg, Per; Maletz, Jorg; Jackson, Allison; Kolte, Ketki; Lowers, Heather; Mackie, James; Newby, Warren; Petrowsky, Matthew

    2015-01-01

    The Cambrian Alum Shale Formation in the Andrarum-3 core from Scania, southern Sweden, consists of black siliciclastic mudstone with minor carbonate intercalations. Four facies comprise three siliciclastic mudstones and one fine-grained carbonate. The facies reflect deposition along a transect from deep ramp to basin on a Cambrian shelf. The three mudstone facies contain abundant clay clasts and laterally variable siltstone laminae. Bed-load transport processes seem to have dominated deposition on this deep shelf. These sedimentary rocks record mainly event deposition, and only relatively few, thin laminae probably resulted from suspension settling. The Alum Shale Formation deep shelf did not show a bioturbation gradient, but fecal strings are common and Planolites burrows are rare in all mudstone facies. Evidence for biotic colonization indicates that this mudstone environment was not persistently anoxic, but rather was most likely intermittently dysoxic. The Alum Shale Formation in the Andrarum-3 core shows an overall decrease of grain size, preserved energy indicators, and carbonate content upsection interpreted to reflect a deepening upward. The succession can also be divided into four small-scale fining-upward cycles that represent deepening, and four overlying coarsening-upward cycles that represent upward shallowing.

  19. [Relevant factors of early puberty timing in urban primary schools in Chongqing].

    PubMed

    Luo, Yan; Liu, Qin; Wen, Yi; Liu, Shudan; Lei, Xun; Wang, Hong

    2016-05-01

    To investigate the status of puberty timing and relevant factors of early puberty timing in children from grade one to four in urban primary schools of Chongqing. According to the purposive sample method, four urban primary schools in Chongqing were selected and of which 1471 children from grade one to four who have obtained informed consent were recruited. Questionnaire survey on social-demographic characteristics and family environment (e.g., age, parents' relationship, diet and lifestyle, etc), and Pubertal Development Scale (PDS) survey and physical examination (measurements of height, weight, pubertal development status, etc) were conducted. P25, P50, P75 ages of each important pubertal event were calculated by probit regression. Univariate and multivariate analysis were used to analyze relevant factors. The detection rate of early puberty timing was 17.7%, and the median ages of the onset of breast and testicular development were 10.77 and 11.48 years old, respectively. Multivariate logistic regression showed that early puberty timing occurred more likely in girls than in boys (OR = 0.561, 95% CI 0.406-0.774), and bad relationship between parents (OR = 1.320, 95% CI 1.007-1.729) and hair-products-use (OR = 1.685, 95%, CI 1.028-2.762) were risk factors of early puberty timing. Early onset of puberty in urban Chongqing is still exist. Gender, parents' relationship, and hair-products-use have an essential impact on early puberty timing.

  20. Precambrian animal life: probable developmental and adult cnidarian forms from Southwest China

    NASA Technical Reports Server (NTRS)

    Chen, Jun-Yuan; Oliveri, Paola; Gao, Feng; Dornbos, Stephen Q.; Li, Chia-Wei; Bottjer, David J.; Davidson, Eric H.

    2002-01-01

    The evolutionary divergence of cnidarian and bilaterian lineages from their remote metazoan ancestor occurred at an unknown depth in time before the Cambrian, since crown group representatives of each are found in Lower Cambrian fossil assemblages. We report here a variety of putative embryonic, larval, and adult microfossils deriving from Precambrian phosphorite deposits of Southwest China, which may predate the Cambrian radiation by 25-45 million years. These are most probably of cnidarian affinity. Large numbers of fossilized early planula-like larvae were observed under the microscope in sections. Though several forms are represented, the majority display remarkable conformity, which is inconsistent with the alternative that they are artifactual mineral inclusions. Some of these fossils are preserved in such high resolution that individual cells can be discerned. We confirm in detail an earlier report of the presence in the same deposits of tabulates, an extinct crown group anthozoan form. Other sections reveal structures that most closely resemble sections of basal modern corals. A large number of fossils similar to modern hydrozoan gastrulae were also observed. These again displayed great morphological consistency. Though only a single example is available, a microscopic animal remarkably similar to a modern adult hydrozoan is also presented. Taken together, the new observations reported in this paper indicate the existence of a diverse and already differentiated cnidarian fauna, long before the Cambrian evolutionary event. It follows that at least stem group bilaterians must also have been present at this time.

  1. The geology of the northern tip of the Arabian-Nubian Shield

    NASA Astrophysics Data System (ADS)

    Beyth, M.; Eyal, Y.; Garfunkel, Z.

    2014-11-01

    accompanied in ∼609 Ma by rhyolite, andesite and composite dykes. The last magmatic event in the Elat area is represented by the volcano-conglomeratic series comprising rhyolites, basalts, andesites, hypabyssal intrusions of monzonite and syenite and conglomerates. The conglomerates, dated to about 590 Ma, are the products of a major erosion phase in which about 12,000 m of the section were removed. These conglomerates were intruded by 585 Ma rhyolite, andesite and composite dykes. The Neoproterozoic basement is truncated by a peneplain whose age, post 532 Ma, is constrained by the age of the youngest eroded dolerite dykes. This Early Cambrian peneplain was associated with erosion of 2000 m of the section and by chemical weathering. Three major breaks in Neoproterozoic magmatic activity are recognized: the first, occurred in Cryogenian time, lasted ∼60 million years after the amphibolite facies metamorphism and before emplacement of the calc alkaline plutons, separating the first and the second orogenic phases; the second break between the orogenic and the extensional phases occurred in early Ediacaran time, encompassed ∼20 million years between the emplacement of the calc-alkaline and alkaline plutonic rocks and rhyolite, andesite and the composite dykes; and the third, ∼50 Ma break, occurred between the emplacement of the last felsic intrusions at ∼585 Ma and intrusion of the dolerite dykes in 532 Ma, before the Early Cambrian peneplain developed. The great lateral extension of the Cambrian to Eocene sedimentary rocks and their slow facies and thickness changes suggest a stable flat platform area at the northern tip of the ANS. Early Cambrian sedimentation began with fluviatile subarkoses of the Amudei Shlomo Formation. It was overlain by an Early to Middle Cambrian transgressive-regressive lagoonal cycle of dolostones, sandstones, and siltstones of the Timna Formation. Then Middle Cambrian subarkoses and siltstones of the Shehoret Formation and the quartz arenite

  2. First-Time Mothers' Knowledge and Beliefs Regarding Early Communication Development

    ERIC Educational Resources Information Center

    Williams, Vicki; Pearce, Wendy M.; Devine, Sue

    2014-01-01

    Limited literature exists in the Australian context about first-time mothers' knowledge of early communication milestones, their strategies to facilitate speech and language development and understanding of the relationship between early communication skills and future development. A cross-sectional online survey was administered to 53 first-time…

  3. Alxa Block Provenance of Ediacaran (Sinian) Sediments in the Helanshan Area: Constraints from Hf Isotopes and U-Pb Geochronology of Detrital Zircons

    NASA Astrophysics Data System (ADS)

    Xiaopeng, D.

    2016-12-01

    The tectonic relationship between the Alxa Block and the North China Craton has long been controversial. The Helanshan area lies at the western margin of the Ordos Block and east of the Alxa Block (Fig.a), and it contains rocks of the lower Zhengmuguan and upper Tuerkeng formations that belong to the Ediacaran system. The Zhengmuguan Formation is made up of abyssal facies rocks including dolomite and glacial conglomerate with dropstones, and the Tuerkeng Formation consists of silty slate of the neritic facies. A discontinuity marks the boundary between the Tuerkeng Formation and the Early Cambrian Suyukou Formation, which is composed mainly of pebbly sandstone towards the base and sandstone towards the top, representing a change in sedimentary facies from terrestrial to littoral.The Neoproterozoic U-Pb ages of zircons from the Ediacaran and Early Cambrian sediments peak at 818 ± 4 Ma (n = 88) and 905 ± 8 Ma (n = 20), consistent with the Neoproterozoic age peaks found in the Precambrian basement of the Alxa Block(Fig.b). There are few Neoproterozoic zircons in the Neoproterozoic strata of the Langshan area, and there are no reports of Neoproterozoic zircons in the Zhuozishan area, northwest of Helanshan, or in the western margin of the neighboring Ordos Basin. A number of Neoproterozoic zircons are found in the Middle Cambrian to Middle Ordovician strata of the Niushoushan area. And while Niushoushan is part of the Hexi Corridor, it did not amalgamate with the NCC before the Early-Middle Cambrian. Therefore, the Neoproterozoic and Early Cambrian sediments in Helanshan record information about Neoproterozoic magmatic events in the Alxa Block, and indicate an Alxa Block provenance(Fig.c).The Hf isotopic characteristics of the Neoproterozoic zircons from the Ediacaran Zhengmuguan Formation in the Helanshan area (eHf(t) = -7.812 to 3.274, TDMC = 2211-1578 Ma, n = 10) are similar to those Neoproterozoic igneous zircons from the Langshan area (eHf(t) = -1.105 to 5

  4. Group Time in Early Childhood Centers: An Exploratory Study.

    ERIC Educational Resources Information Center

    McAfee, Oralie

    To investigate the current status of group time in early childhood centers, a small-scale exploratory study was designed and executed. Results of interviews with 35 teachers and observations in five classrooms serving children ages 2 1/2 through kindergarten revealed that all classrooms had at least one group time or circle time, usually in the…

  5. Background experiences, time allocation, time on teaching and perceived support of early-career college science faculty

    NASA Astrophysics Data System (ADS)

    Sagendorf, Kenneth S.

    The purposes of this research were to create an inventory of the research, teaching and service background experiences of and to document the time allocation and time spent on teaching by early-career college science faculty members. This project is presented as three distinct papers. Thirty early-career faculty in the science disciplines from sixteen different institutions in their first year of employment participated in this study. For the first two papers, a new survey was developed asking participants to choose which experiences they had acquired prior to taking their current faculty position and asking them to document their time allocation and time spent on teaching activities in an average work week. In addition, a third component documents the support early-career college faculty in the sciences are receiving from the perspective of faculty members and their respective department chairpersons and identifies areas of disagreement between these two different groups. Twenty early-career college science faculty and their respective department chairpersons completed a newly-designed survey regarding the support offered to new faculty. The survey addressed the areas of feedback on performance, clarity of tenure requirements, mentoring, support for teaching and scholarship and balancing faculty life. This dissertation presents the results from these surveys, accounting for different demographic variables such as science discipline, gender and institutional category.

  6. Modern freshwater microbialite analogues for ancient dendritic reef structures

    NASA Technical Reports Server (NTRS)

    Laval, B.; Cady, S. L.; Pollack, J. C.; McKay, C. P.; Bird, J. S.; Grotzinger, J. P.; Ford, D. C.; Bohm, H. R.

    2000-01-01

    Microbialites are organosedimentary structures that can be constructed by a variety of metabolically distinct taxa. Consequently, microbialite structures abound in the fossil record, although the exact nature of the biogeochemical processes that produced them is often unknown. One such class of ancient calcareous structures, Epiphyton and Girvanella, appear in great abundance during the Early Cambrian. Together with Archeocyathids, stromatolites and thrombolites, they formed major Cambrian reef belts. To a large extent, Middle to Late Cambrian reefs are similar to Precambrian reefs, with the exception that the latter, including terminal Proterozoic reefs, do not contain Epiphyton or Girvanella. Here we report the discovery in Pavilion Lake, British Columbia, Canada, of a distinctive assemblage of freshwater calcite microbialites, some of which display microstructures similar to the fabrics displayed by Epiphyton and Girvanella. The morphologies of the modern microbialites vary with depth, and dendritic microstructures of the deep water (> 30 m) mounds indicate that they may be modern analogues for the ancient calcareous structures. These microbialites thus provide an opportunity to study the biogeochemical interactions that produce fabrics similar to those of some enigmatic Early Cambrian reef structures.

  7. Impact cratering calculations. Part 1: Early time results

    NASA Technical Reports Server (NTRS)

    Thomsen, J. M.; Sauer, F. N.; Austin, M. G.; Ruhl, S. F.; Shultz, P. H.; Orphal, D. L.

    1979-01-01

    Early time two dimensional finite difference calculations of laboratory scale hypervelocity impact of 0.3 g spherical 2024 aluminum projectiles into homogeneous plasticene clay targets were performed. Analysis of resulting material motions showed that energy and momentum were coupled quickly from the aluminum projectile to the target material. In the process of coupling, some of the plasticene clay target was vaporized while the projectile become severely deformed. The velocity flow field developed within the target was shown to have features similar to those found in calculations of near surface explosion cratering. Specific application of Maxwell's analytic Z-Model showed that this model can be used to describe the early time flow fields resulting from the impact cratering calculations as well, provided the flow field centers are located beneath the target surface and most of the projectile momentum is dissipated before the model is applied.

  8. Evidence for Late-Paleozoic brine migration in Cambrian carbonate rocks of the central and southern Appalachians: Implications for Mississippi Valley-type sulfide mineralization

    USGS Publications Warehouse

    Hearn, P.P.; Sutter, J.F.; Belkin, H.E.

    1987-01-01

    Many Lower Paleozoic limestones and dolostones in the Valley and Ridge province of the central and southern Appalachians contain 10 to 25 weight percent authigenic potassium feldspar. This was considered to be a product of early diagenesis, however, 40Ar 39Ar analyses of overgrowths on detrital K-feldspar in Cambrian carbonate rocks from Pennsylvania, Maryland, Virginia, and Tennessee yield Late Carboniferous-Early Permian ages (278-322 Ma). Simple mass balance calculations suggest that the feldspar could not have formed isochemically, but required the flux of multiple pore volumes of fluid through the rocks, reflecting regional fluid migration events during the Late-Paleozoic Alleghanian orogeny. Microthermometric measurements of fluid inclusions in overgrowths on detrital K-feldspar and quartz grains from unmineralized rocks throughout the study area indicate homogenization temperatures from 100?? to 200??C and freezing point depressions of -14?? to -18.5??C (18-21 wt.% NaCl equiv). The apparent similarity of these fluids to fluid inclusions in ore and gangue minerals of nearby Mississippi Valley-type (MVT) deposits suggests that the regional occurrences of authigenic K-feldspar and MVT mineralization may be genetically related. This hypothesis is supported by the discovery of authigenic K-feldspar intergrown with sphalerite in several mines of the Mascot-Jefferson City District, E. Tennessee. Regional potassic alteration in unmineralized carbonate rocks and localized occurrences of MVT mineralization are both explainable by a gravity-driven flow model, in which deep brines migrate towards the basin margin under a hydraulic gradient established during the Alleghanian orogeny. The authigenic K-feldspar may reflect the loss of K during disequilibrium cooling of the ascending brines. MVT deposits are probably localized manifestations of the same migrating fluids, occurring where the necessary physical and chemical traps are present. ?? 1987.

  9. Effectiveness of early part-time sick leave in musculoskeletal disorders.

    PubMed

    Martimo, Kari-Pekka; Kaila-Kangas, Leena; Kausto, Johanna; Takala, Esa-Pekka; Ketola, Ritva; Riihimäki, Hilkka; Luukkonen, Ritva; Karppinen, Jaro; Miranda, Helena; Viikari-Juntura, Eira

    2008-02-25

    The importance of staying active instead of bed rest has been acknowledged in the management of musculoskeletal disorders (MSDs). This emphasizes the potential benefits of adjusting work to fit the employee's remaining work ability. Despite part-time sick leave being an official option in many countries, its effectiveness has not been studied yet. We have designed a randomized controlled study to assess the health effects of early part-time sick leave compared to conventional full-day sick leave. Our hypothesis is that if work time is temporarily reduced and work load adjusted at the early stages of disability, employees with MSDs will have less disability days and faster return to regular work duties than employees on a conventional sick leave. The study population will consist of 600 employees, who seek medical advice from an occupational physician due to musculoskeletal pain. The inclusion requires that they have not been on a sick leave for longer than 14 days prior to the visit. Based on the physician's judgement, the severity of the symptoms must indicate a need for conventional sick leave, but the employee is considered to be able to work part-time without any additional risk. Half of the employees are randomly allocated to part-time sick leave group and their work time is reduced by 40-60%, whereas in the control group work load is totally eliminated with conventional sick leave. The main outcomes are the number of days from the initial visit to return to regular work activities, and the total number of sick leave days during 12 and 24 months of follow-up. The costs and benefits as well as the feasibility of early part-time sick leave will also be evaluated. This is the first randomised trial to our knowledge on the effectiveness of early part-time sick leave compared to conventional full-time sick leave in the management of MSDs. The data collection continues until 2011, but preliminary results on the feasibility of part-time sick leave will be available

  10. Optimal timing for early surgery in infective endocarditis: a meta-analysis†

    PubMed Central

    Liang, Fuxiang; Song, Bing; Liu, Ruisheng; Yang, Liu; Tang, Hanbo; Li, Yuanming

    2016-01-01

    To systematically review early surgery and the optimal timing of surgery in patients with infective endocarditis (IE), a search for foreign and domestic articles on cohort studies about the association between early surgery and infective endocarditis published from inception to January 2015 was conducted in the PubMed, EMBASE, Chinese Biomedical Literature (CBM), Wanfang and Chinese National Knowledge Infrastructure (CNKI) databases. The studies were screened according to the inclusion and exclusion criteria, the data were extracted and the quality of the method of the included studies was assessed. Then, the meta-analysis was performed using the Stata 12.0 software. Sixteen cohort studies, including 8141 participants were finally included. The results of the meta-analysis revealed that, compared with non-early surgery, early surgery in IE lowers the incidence of in-hospital mortality [odds ratio (OR) = 0.57, 95% confidence interval (CI) (0.42, 0.77); P = 0.000, I2 = 73.1%] and long-term mortality [OR = 0.57, 95% CI (0.43, 0.77); P = 0.001, I2 = 67.4%]. Further, performing operation within 2 weeks had a more favourable effect on long-term mortality [OR = 0.63, 95% CI (0.41, 0.97); P = 0.192, I2 = 39.4%] than non-early surgery. In different kinds of IE, we found that early surgery for native valve endocarditis (NVE) had a lower in-hospital [OR = 0.46, 95% CI (0.31, 0.69); P = 0.001, I2 = 73.0%] and long-term [OR = 0.57, 95% CI (0.40, 0.81); P = 0.001, I2 = 68.9%] mortality than the non-early surgery group. However, for prosthetic valve endocarditis (PVE), in-hospital mortality did not differ significantly [OR = 0.83, 95% CI (0.65, 1.06); P = 0.413, I2 = 0.0%] between early and non-early surgery. We concluded that early surgery was associated with lower in-hospital and long-term mortality compared with non-early surgical treatment for IE, especially in NVE. However, the optimal timing of surgery remains unclear. Additional larger prospective clinical trials will be

  11. Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda.

    PubMed

    Yang, Jie; Ortega-Hernández, Javier; Butterfield, Nicholas J; Liu, Yu; Boyan, George S; Hou, Jin-Bo; Lan, Tian; Zhang, Xi-Guang

    2016-03-15

    Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstätte (South China). The VNC of C. kunmingensis comprises a homonymous series of condensed ganglia that extend throughout the body, each associated with a pair of biramous limbs. Submillimetric preservation reveals numerous segmental and intersegmental nerve roots emerging from both sides of the VNC, which correspond topologically to the peripheral nerves of extant Priapulida and Onychophora. The fuxianhuiid VNC indicates that ancestral neurological features of Ecdysozoa persisted into derived members of stem-group Euarthropoda but were later lost in crown-group representatives. These findings illuminate the VNC ground pattern in Panarthropoda and suggest the independent secondary loss of cycloneuralian-like neurological characters in Tardigrada and Euarthropoda.

  12. Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda

    PubMed Central

    Yang, Jie; Ortega-Hernández, Javier; Butterfield, Nicholas J.; Liu, Yu; Boyan, George S.; Hou, Jin-bo; Lan, Tian; Zhang, Xi-guang

    2016-01-01

    Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstätte (South China). The VNC of C. kunmingensis comprises a homonymous series of condensed ganglia that extend throughout the body, each associated with a pair of biramous limbs. Submillimetric preservation reveals numerous segmental and intersegmental nerve roots emerging from both sides of the VNC, which correspond topologically to the peripheral nerves of extant Priapulida and Onychophora. The fuxianhuiid VNC indicates that ancestral neurological features of Ecdysozoa persisted into derived members of stem-group Euarthropoda but were later lost in crown-group representatives. These findings illuminate the VNC ground pattern in Panarthropoda and suggest the independent secondary loss of cycloneuralian-like neurological characters in Tardigrada and Euarthropoda. PMID:26933218

  13. Time and Temporality in Early Childhood Educators' Work

    ERIC Educational Resources Information Center

    Nuttall, Joce; Thomas, Louise

    2015-01-01

    This article reports on the persistence and significance of notions of time and temporality in interviews with early childhood educators in Victoria and Queensland, Australia, in two studies designed to explore the concept of "pedagogical leadership". Interpretive analysis of the interview transcripts of the 19 participants identified…

  14. Time scale controversy: Accurate orbital calibration of the early Paleogene

    NASA Astrophysics Data System (ADS)

    Roehl, U.; Westerhold, T.; Laskar, J.

    2012-12-01

    Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to 54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

  15. Time scale controversy: Accurate orbital calibration of the early Paleogene

    NASA Astrophysics Data System (ADS)

    Westerhold, Thomas; RöHl, Ursula; Laskar, Jacques

    2012-06-01

    Timing is crucial to understanding the causes and consequences of events in Earth history. The calibration of geological time relies heavily on the accuracy of radioisotopic and astronomical dating. Uncertainties in the computations of Earth's orbital parameters and in radioisotopic dating have hampered the construction of a reliable astronomically calibrated time scale beyond 40 Ma. Attempts to construct a robust astronomically tuned time scale for the early Paleogene by integrating radioisotopic and astronomical dating are only partially consistent. Here, using the new La2010 and La2011 orbital solutions, we present the first accurate astronomically calibrated time scale for the early Paleogene (47-65 Ma) uniquely based on astronomical tuning and thus independent of the radioisotopic determination of the Fish Canyon standard. Comparison with geological data confirms the stability of the new La2011 solution back to ˜54 Ma. Subsequent anchoring of floating chronologies to the La2011 solution using the very long eccentricity nodes provides an absolute age of 55.530 ± 0.05 Ma for the onset of the Paleocene/Eocene Thermal Maximum (PETM), 54.850 ± 0.05 Ma for the early Eocene ash -17, and 65.250 ± 0.06 Ma for the K/Pg boundary. The new astrochronology presented here indicates that the intercalibration and synchronization of U/Pb and 40Ar/39Ar radioisotopic geochronology is much more challenging than previously thought.

  16. Pubertal timing and early sexual intercourse in the offspring of teenage mothers.

    PubMed

    De Genna, Natacha M; Larkby, Cynthia; Cornelius, Marie D

    2011-10-01

    Early puberty is associated with stressful family environments, early sexual intercourse, and teenage pregnancy. We examined pubertal timing and sexual debut among the 14-year-old offspring of teenage mothers. Mothers (71% Black, 29% White) were recruited as pregnant teenagers (12-18 years old). Data were collected during pregnancy and when offspring were 6, 10 and 14 years old (n = 318). Adolescents (50% male) compared the timing of their pubertal maturation to same-sex peers. There was a significant 3-way interaction effect of race, sex, and pubertal timing on sexual debut (n = 305). This effect remained significant in a model controlling for maternal age at first intercourse, substance use, exposure to trauma, authoritative parenting, and peer sexual activity (n = 255). Early maturation was associated with early sex in daughters, and may be one pathway for the inter-generational transfer of risk for teenage pregnancy among daughters of teenage mothers.

  17. Cambrian origin of the CYP27C1-mediated vitamin A1-to-A2 switch, a key mechanism of vertebrate sensory plasticity

    USGS Publications Warehouse

    Morshedian, Ala; Toomery, Matthew B.; Pollock, Gabriel E.; Frederiksen, Rikard; Enright, Jennifer; McCormick, Stephen; Cornwall, M. Carter; Fain, Gordon L.; Corbo, Joseph C.

    2017-01-01

    The spectral composition of ambient light varies across both space and time. Many species of jawed vertebrates adapt to this variation by tuning the sensitivity of their photoreceptors via the expression of CYP27C1, an enzyme that converts vitamin A1 into vitamin A2, thereby shifting the ratio of vitamin A1-based rhodopsin to red-shifted vitamin A2-based porphyropsin in the eye. Here, we show that the sea lamprey (Petromyzon marinus), a jawless vertebrate that diverged from jawed vertebrates during the Cambrian period (approx. 500 Ma), dynamically shifts its photoreceptor spectral sensitivity via vitamin A1-to-A2 chromophore exchange as it transitions between photically divergent aquatic habitats. We further show that this shift correlates with high-level expression of the lamprey orthologue of CYP27C1, specifically in the retinal pigment epithelium as in jawed vertebrates. Our results suggest that the CYP27C1-mediated vitamin A1-to-A2 switch is an evolutionarily ancient mechanism of sensory plasticity that appeared not long after the origin of vertebrates.

  18. New palaeomagnetic data from Argun terrane. Testing its association with Amuria and the Mongol-Okhotsk Ocean

    NASA Astrophysics Data System (ADS)

    Gordienko, I. V.; Metelkin, D. V.; Vetluzhskikh, L. I.; Mikhaltsov, N. E.; Kulakov, E. V.

    2018-06-01

    In this study, we present new palaeomagnetic and geological data obtained from Ediacaran and Cambrian sedimentary rocks of Argun terrane, which is traditionally considered a key element of the hypothetical Amuria composite continent. Since 1990, when Amuria was first proposed in palaeogeographic reconstructions, it became one of the principle members in the global palaeotectonic schemes. A scenario when collision of Amuria with Siberian margin resulted in formation of the Mongol-Okhotsk Ocean is universally accepted and supported by majority of researchers. However, time of Amuria's final assembly and relative position of the blocks within Amuria before the collision with Siberia is still a topic of debate. Questions about principal allocation of Argun terrane and its relation to Amuria during the late Neoroterozoic-Cambrian are addressed in this study. Palaeomagnetic poles for the Ediacaran-early Cambrian rocks of Argun terrane differ within an error from coeval poles from Siberia indicating that Argun terrane could have been located similar to its present-day position with respect to Siberia already at 560-525 Ma. This observation calls into question association of Argun terrane with Amuria, which in classic reconstructions is usually placed close to the North China Craton. It also questions our current understanding of the Amuria palaeocontinent and consequently, accuracy of global palaeogeographic reconstructions for the late Neoproterozoic-Cambrian in general, and those of the eastern part of the Central Asia in particular.

  19. Pubertal Timing and Early Sexual Intercourse in the Offspring of Teenage Mothers

    PubMed Central

    De Genna, Natacha M.; Larkby, Cynthia; Cornelius, Marie D.

    2011-01-01

    Early puberty is associated with stressful family environments, early sexual intercourse, and teenage pregnancy. We examined pubertal timing and sexual debut among the 14-year-old offspring of teenage mothers. Mothers (71% Black, 29% White) were recruited as pregnant teenagers (12–18 years old). Data were collected during pregnancy and when offspring were 6, 10 and 14 years old (n = 318). Adolescents (50% male) compared the timing of their pubertal maturation to same-sex peers. There was a significant 3-way interaction effect of race, sex, and pubertal timing on sexual debut (n = 305). This effect remained significant in a model controlling for maternal age at first intercourse, substance use, exposure to trauma, authoritative parenting, and peer sexual activity (n = 255). Early maturation was associated with early sex in daughters, and may be one pathway for the inter-generational transfer of risk for teenage pregnancy among daughters of teenage mothers. PMID:21279428

  20. Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont

    USGS Publications Warehouse

    Cady, Wallace Martin; Albee, Arden Leroy; Chidester, A.H.

    1963-01-01

    The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north-central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bedrock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamorphosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamorphosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian(?) and Early Cambrian age is characterized by carbonaceous schist. It is succeeded in western parts of the area by the Jay Peak formation of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a

  1. Optimal timing for early surgery in infective endocarditis: a meta-analysis.

    PubMed

    Liang, Fuxiang; Song, Bing; Liu, Ruisheng; Yang, Liu; Tang, Hanbo; Li, Yuanming

    2016-03-01

    To systematically review early surgery and the optimal timing of surgery in patients with infective endocarditis (IE), a search for foreign and domestic articles on cohort studies about the association between early surgery and infective endocarditis published from inception to January 2015 was conducted in the PubMed, EMBASE, Chinese Biomedical Literature (CBM), Wanfang and Chinese National Knowledge Infrastructure (CNKI) databases. The studies were screened according to the inclusion and exclusion criteria, the data were extracted and the quality of the method of the included studies was assessed. Then, the meta-analysis was performed using the Stata 12.0 software. Sixteen cohort studies, including 8141 participants were finally included. The results of the meta-analysis revealed that, compared with non-early surgery, early surgery in IE lowers the incidence of in-hospital mortality [odds ratio (OR) = 0.57, 95% confidence interval (CI) (0.42, 0.77); P = 0.000, I(2) = 73.1%] and long-term mortality [OR = 0.57, 95% CI (0.43, 0.77); P = 0.001, I(2) = 67.4%]. Further, performing operation within 2 weeks had a more favourable effect on long-term mortality [OR = 0.63, 95% CI (0.41, 0.97); P = 0.192, I(2) = 39.4%] than non-early surgery. In different kinds of IE, we found that early surgery for native valve endocarditis (NVE) had a lower in-hospital [OR = 0.46, 95% CI (0.31, 0.69); P = 0.001, I(2) = 73.0%] and long-term [OR = 0.57, 95% CI (0.40, 0.81); P = 0.001, I(2) = 68.9%] mortality than the non-early surgery group. However, for prosthetic valve endocarditis (PVE), in-hospital mortality did not differ significantly [OR = 0.83, 95% CI (0.65, 1.06); P = 0.413, I(2) = 0.0%] between early and non-early surgery. We concluded that early surgery was associated with lower in-hospital and long-term mortality compared with non-early surgical treatment for IE, especially in NVE. However, the optimal timing of surgery remains unclear. Additional larger prospective clinical

  2. The evolution of early vertebrate photoreceptors.

    PubMed

    Collin, Shaun P; Davies, Wayne L; Hart, Nathan S; Hunt, David M

    2009-10-12

    Meeting the challenge of sampling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciation in the Early Cambrian. Based on the fossil record, we know that hagfishes, lampreys, holocephalans, elasmobranchs and lungfishes occupy critical stages in vertebrate evolution, having remained relatively unchanged over hundreds of millions of years. Now using extant representatives of these 'living fossils', we are able to piece together the evolution of vertebrate photoreception. While photoreception in hagfishes appears to be based on light detection and controlling circadian rhythms, rather than image formation, the photoreceptors of lampreys fall into five distinct classes and represent a critical stage in the dichotomy of rods and cones. At least four types of retinal cones sample the visual environment in lampreys mediating photopic (and potentially colour) vision, a sampling strategy retained by lungfishes, some modern teleosts, reptiles and birds. Trichromacy is retained in cartilaginous fishes (at least in batoids and holocephalans), where it is predicted that true scotopic (dim light) vision evolved in the common ancestor of all living gnathostomes. The capacity to discriminate colour and balance the tradeoff between resolution and sensitivity in the early vertebrates was an important driver of eye evolution, where many of the ocular features evolved were retained as vertebrates progressed on to land.

  3. Cadomian volcanosedimentary complexes across the Ediacaran-Cambrian transition of the Eastern Pyrenees, southwestern Europe

    NASA Astrophysics Data System (ADS)

    Padel, Maxime; Álvaro, J. Javier; Casas, Josep Maria; Clausen, Sébastien; Poujol, Marc; Sánchez-García, Teresa

    2017-11-01

    The volcanism hosted by the Ediacaran-Terreneuvian Canaveilles Group of the Eastern Pyrenees displays two distinct geochemical affinities: (1) metabasites of the Nyer and Olette formations reflect the emplacement of a tholeiitic magmatism linked to extensional conditions, whereas (2) subsequent felsic and calc-alkaline magmatic rocks marking the top of the Olette Formation and forming the overlying Fabert and Finestrelles members represent Cadomian magmatic events. Based on U-Pb zircon dating constraints, palaeotopographic relationships linked to onlap geometries and distance from vent sources, three volcanosedimentary edifices can be distinguished, the so-called Tregurà (ca. 565-552 Ma), Cap de Creus (ca. 558 Ma) and Coll d'Ares (ca. 542-532 Ma) edifices. The top of their palaeoreliefs recorded locally the nucleation of centres of microbial carbonate productivity (Puig Sec Member) linked to synsedimentary tilting and karstification. Throughout West Gondwana, the presence of carbonate production across the Ediacaran-Cambrian transition is exclusively located in back-arc settings (Central-Iberian Zone) and areas far from the Cadomian subduction trench and devoid of significant terrigenous input, such as those reported in the Eastern Pyrenees and the neighbouring Montagne Noire.

  4. DHI evaluation by combining rock physics simulation and statistical techniques for fluid identification of Cambrian-to-Cretaceous clastic reservoirs in Pakistan

    NASA Astrophysics Data System (ADS)

    Ahmed, Nisar; Khalid, Perveiz; Shafi, Hafiz Muhammad Bilal; Connolly, Patrick

    2017-10-01

    The use of seismic direct hydrocarbon indicators is very common in exploration and reservoir development to minimise exploration risk and to optimise the location of production wells. DHIs can be enhanced using AVO methods to calculate seismic attributes that approximate relative elastic properties. In this study, we analyse the sensitivity to pore fluid changes of a range of elastic properties by combining rock physics studies and statistical techniques and determine which provide the best basis for DHIs. Gassmann fluid substitution is applied to the well log data and various elastic properties are evaluated by measuring the degree of separation that they achieve between gas sands and wet sands. The method has been applied successfully to well log data from proven reservoirs in three different siliciclastic environments of Cambrian, Jurassic, and Cretaceous ages. We have quantified the sensitivity of various elastic properties such as acoustic and extended elastic (EEI) impedances, elastic moduli ( K sat and K sat- μ), lambda-mu-rho method ( λρ and μρ), P-to-S-wave velocity ratio ( V P/ V S), and Poisson's ratio ( σ) at fully gas/water saturation scenarios. The results are strongly dependent on the local geological settings and our modeling demonstrates that for Cambrian and Cretaceous reservoirs, K sat- μ, EEI, V P/ V S, and σ are more sensitive to pore fluids (gas/water). For the Jurassic reservoir, the sensitivity of all elastic and seismic properties to pore fluid reduces due to high overburden pressure and the resultant low porosity. Fluid indicators are evaluated using two metrics: a fluid indicator coefficient based on a Gaussian model and an overlap coefficient which makes no assumptions about a distribution model. This study will provide a potential way to identify gas sand zones in future exploration.

  5. An outline of the palaeogeographic evolution of the Australasian region since the beginning of the Neoproterozoic

    NASA Astrophysics Data System (ADS)

    Li, Z. X.; Powell, C. McA.

    2001-04-01

    In the last 1000 million years, Australia has been part of two supercontinents: Palaeozoic Gondwanaland and Neoproterozoic Rodinia. Neoproterozoic Australia was covered by shallow epicontinental seas, and, in the late Neoproterozoic, by low-latitude glaciers. The breakup of Rodinia along the Tasman Line occurred at the end of the Sturtian glaciation (760 Ma) giving rise to the Palaeo-Pacific Ocean. Gondwanaland formed in the Early Cambrian, at the same time as the Tarim block broke away from northwestern Australia. Westward subduction of the Palaeo-Pacific Ocean along the eastern margin of Australia-Antarctica commenced during the Early Cambrian in northern Victoria Land and in the Middle Cambrian in South Australia, and culminated to the Late Cambrian-Early Ordovician Ross-Delamerian Mountains. In the Ordovician, the magmatic arc retreated from Australia's then-eastern continental margin, forming a marginal sea and offshore island arc. A shallow seaway across Australia in the Late Cambrian and Ordovician gradually gave way to desert-like conditions in Central Australia and the adjacent Canning Basin by Silurian time. The Silurian to mid-Devonian was an interval of rapidly changing palaeogeography in eastern Australia with deep volcanogenic troughs formed in a dextral transtensional tectonic setting. Widespread deformation in the Tasman orogenic zone in the Middle Devonian to Early Carboniferous, was accompanied by the development of an Andean-style magmatic arc along the Pacific continental margin of Australia. The most widespread Phanerozoic mountain-building stage in Central Australia occurred in the Late Devonian to mid-Carboniferous, as part of a world-wide Variscan orogenic episode associated with the collision of Gondwanaland with Laurussia to form Pangea. In the late Visean, Australia drifted rapidly southward from previous low latitudes to a near-polar position. Glacial conditions dominated the Late Carboniferous and earliest Permian. Transtensional basins

  6. Early Proterozoic (2.04 GA) Phoshorites of Pechenga Greenstone Belt and Their Origin

    NASA Technical Reports Server (NTRS)

    Rozanov, Alexei Yu.; Astafieva, Marina M.; Hoover, Richard B.

    2007-01-01

    No principal differences have been found between microfossils described from Cambrian and Phanerozoic and the 2000 Ma phosphorites. Numerous samples revealed diverse microbial microstructures interpreted as cyanobacterial mats consisting of filamentous (1-3 microns in diameter, 20 microns in length), coccoidal (0.8-1.0 microns) and ellipsoidal or rod-shaped microfossils (0.8 microns in diameter, around 2 microns in length) which morphologically resemble modern Microcoleus and Siphonophycus, Thiocapsa, and Rhabdoderma, respectively, reported from alkali ne or saline environment_ The sequence of the early Palaeoproterozoic events which point to a significant oxidation of the hydrosphere, including the formation of phosphorites and changes in the phosphorous cycle, mimics the sequence which was repeated at the Neoproterozoic-Cembrian transition, implying that oxidation of the terrestrial atmosphere-hydrosphere system experienced an irregular cyclic development.

  7. Pikaia gracilens Walcott: stem chordate, or already specialized in the Cambrian?

    PubMed

    Mallatt, Jon; Holland, Nicholas

    2013-06-01

    For the past 35 years, the Cambrian fossil Pikaia gracilens was widely interpreted as a typical basal chordate based on short descriptions by Conway Morris. Recently, Conway Morris and Caron (CMC) (2012, Biol Rev 87:480-512) described Pikaia extensively, as a basis for new ideas about deuterostome evolution. This new Pikaia has characters with no clear homologues in other animals, so they could be phylogenetically uninformative autapomorphies. These characters include a dorsal organ, posterior ventral area, posterior fusiform structure, and anterior dorsal unit. Yet CMC interpret most of the unusual characters as primitive for chordates, thereby interpreting Pikaia as an even more convincing stem chordate than before. Moreover, they claim that segment (myomere) shape is a reliable guide for defining a chordate and even for assigning animals to their correct place in deuterostome phylogeny. By defining sigmoidal segments as a basal chordate character, they situate Pikaia at the base of the chordates and banish fossil yunnanozoans (which have straight segments) to a position deep within the deuterostomes. In addition, they consider amphioxus, with its conspicuously chevron-shaped segments, to be so highly derived that it is of little use for reconstructing the first chordates. We question their overemphasis on the phylogenetic value of segment shape and their marginalizing of amphioxus. We deduce that Pikaia, not amphioxus, is specialized. We performed a cladistic analysis that showed the character interpretations of CMC are consistent with their wide-ranging evolutionary scenario, but that these interpretations leave unresolved the position of Pikaia within chordates. Copyright © 2013 Wiley Periodicals, Inc.

  8. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming.

    PubMed

    Lacalli, Thurston

    2012-07-06

    Conway Morris and Caron (2012) have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia's anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundaries between them (the myosepta) are gently curved, with minimal overlap, whereas amphioxus and vertebrates have strongly overlapping V- and W-shaped myomeres. The implication, on biomechanical grounds, is that myomeres in Pikaia exerted much less tension on the myosepta, so the animal would have been incapable of swimming as rapidly as living chordates operating in the fast-twitch mode used for escape and attack. Pikaia either lacked the fast-twitch fibers necessary for such speeds, having instead only slow-twitch fibers, or it had an ancestral fiber type with functional capabilities more like modern slow fibers than fast ones. The first option is supported by the sequence of development in zebrafish, where both myoseptum formation and fast fiber deployment show a dependence on slow fibers, which develop first. For Pikaia, the absence of fast fibers has both behavioral and anatomical implications, which are discussed. Among the latter is the possibility that a notochord may not have been needed as a primary stiffening device if other structures (for example, the dorsal organ) could perform that role.

  9. Early Paleozoic tectonic reconstruction of Iran: Tales from detrital zircon geochronology

    NASA Astrophysics Data System (ADS)

    Moghadam, Hadi Shafaii; Li, Xian-Hua; Griffin, William L.; Stern, Robert J.; Thomsen, Tonny B.; Meinhold, Guido; Aharipour, Reza; O'Reilly, Suzanne Y.

    2017-01-01

    In this study we use detrital zircons to probe the Early Paleozoic history of NE Iran and evaluate the link between sediment sources and Gondwanan pre-Cadomian, Cadomian and younger events. U-Pb zircon ages and Hf isotopic compositions are reported for detrital zircons from Ordovician and Early Devonian sedimentary rocks from NE Iran. These clastic rocks are dominated by zircons with major age populations at 2.5 Ga, 0.8-0.6 Ga, 0.5 Ga and 0.5-0.4 Ga as well as a minor broad peak at 1.0 Ga. The source of 2.5 Ga detrital zircons is enigmatic; they may have been supplied from the Saharan Metacraton (or West African Craton) to the southwest or Afghanistan-Tarim to the east. The detrital zircons with age populations at 0.8-0.6 Ga probably originated from Cryogenian-Ediacaran juvenile igneous rocks of the Arabian-Nubian Shield; this inference is supported by their juvenile Hf isotopes, although some negative εHf (t) values suggest that other sources (such as the West African Craton) were also involved. The age peak at ca 0.5 Ga correlates with Cadomian magmatism reported from Iranian basement and elsewhere in north Gondwana. The variable εHf (t) values of Cadomian detrital zircons, resembling the εHf (t) values of zircons in magmatic Cadomian rocks from Iran and Taurides (Turkey), suggest an Andean-type margin and the involvement of reworked older crust in the generation of the magmatic rocks. The youngest age population at 0.5-0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys, which probably started in Late Cambrian-Ordovician time. A combination of U-Pb dating and Hf-isotope data from Iran, Turkey and North Gondwana confirms that Iran and Turkey were parts of Gondwana at least until late Paleozoic time.

  10. Novel Algorithms Enabling Rapid, Real-Time Earthquake Monitoring and Tsunami Early Warning Worldwide

    NASA Astrophysics Data System (ADS)

    Lomax, A.; Michelini, A.

    2012-12-01

    We have introduced recently new methods to determine rapidly the tsunami potential and magnitude of large earthquakes (e.g., Lomax and Michelini, 2009ab, 2011, 2012). To validate these methods we have implemented them along with other new algorithms within the Early-est earthquake monitor at INGV-Rome (http://early-est.rm.ingv.it, http://early-est.alomax.net). Early-est is a lightweight software package for real-time earthquake monitoring (including phase picking, phase association and event detection, location, magnitude determination, first-motion mechanism determination, ...), and for tsunami early warning based on discriminants for earthquake tsunami potential. In a simulation using archived broadband seismograms for the devastating M9, 2011 Tohoku earthquake and tsunami, Early-est determines: the epicenter within 3 min after the event origin time, discriminants showing very high tsunami potential within 5-7 min, and magnitude Mwpd(RT) 9.0-9.2 and a correct shallow-thrusting mechanism within 8 min. Real-time monitoring with Early-est givess similar results for most large earthquakes using currently available, real-time seismogram data. Here we summarize some of the key algorithms within Early-est that enable rapid, real-time earthquake monitoring and tsunami early warning worldwide: >>> FilterPicker - a general purpose, broad-band, phase detector and picker (http://alomax.net/FilterPicker); >>> Robust, simultaneous association and location using a probabilistic, global-search; >>> Period-duration discriminants TdT0 and TdT50Ex for tsunami potential available within 5 min; >>> Mwpd(RT) magnitude for very large earthquakes available within 10 min; >>> Waveform P polarities determined on broad-band displacement traces, focal mechanisms obtained with the HASH program (Hardebeck and Shearer, 2002); >>> SeisGramWeb - a portable-device ready seismogram viewer using web-services in a browser (http://alomax.net/webtools/sgweb/info.html). References (see also: http

  11. Cognitive Vulnerabilities Amplify the Effect of Early Pubertal Timing on Interpersonal Stress Generation During Adolescence

    PubMed Central

    Stange, Jonathan P.; Kleiman, Evan M.; Hamlat, Elissa J.; Abramson, Lyn Y.; Alloy, Lauren B.

    2013-01-01

    Early pubertal timing has been found to confer risk for the occurrence of interpersonal stressful events during adolescence. However, pre-existing vulnerabilities may exacerbate the effects of early pubertal timing on the occurrence of stressors. Thus, the current study prospectively examined whether cognitive vulnerabilities amplified the effects of early pubertal timing on interpersonal stress generation. In a diverse sample of 310 adolescents (M age = 12.83 years, 55 % female; 53 % African American), early pubertal timing predicted higher levels of interpersonal dependent events among adolescents with more negative cognitive style and rumination, but not among adolescents with lower levels of these cognitive vulnerabilities. These findings suggest that cognitive vulnerabilities may heighten the risk of generating interpersonal stress for adolescents who undergo early pubertal maturation, which may subsequently place adolescents at greater risk for the development of psychopathology. PMID:24061858

  12. Assembling and disassembling california: A zircon and monazite geochronologic framework for proterozoic crustal evolution in southern California

    USGS Publications Warehouse

    Barth, A.P.; Wooden, J.L.; Coleman, D.S.; Vogel, M.B.

    2009-01-01

    The Mojave province in southern California preserves a comparatively complete record of assembly, postorogenic sedimentation, and rifting along the southwestern North American continental margin. The oldest exposed rocks are metasedimentary gneisses and amphibolite, enclosing intrusive suites that range from tonalite and quartz mon-zodiorite to granite with minor trondhjemite. Discrete magmatic episodes occurred at approximately 1790-1730 and 1690-1640 Ma. Evidence from detrital and premagmatic zircons indicates that recycling of 1900-1790 Ma Paleopro-terozoic crust formed the unique isotopic character of the Mojave province. Peak metamorphic conditions in the Mojave province reached middle amphibolite to granulite facies; metamorphism occurred locally from 1795 to 1640 Ma, with widespread evidence for metamorphism at 1711-1689 and 1670-1650 Ma. Structures record early, tight to isoclinal folding and penetrative west-vergent shear during the final metamorphic event in the west Mojave province. Proterozoic basement rocks are overlain by siliciclastic-carbonate sequences of Mesoproterozoic, Neoproterozoic, and Cambrian age, recording environmental change over the course of the transition from stable Mojave crust to the rifted Cordilleran margin. Neoproterozoic quartzites have diverse zircon populations inconsistent with a southwest North American source, which we infer were derived from the western conjugate rift pair within Rodinia, before establishment of the miogeocline. Neoproterozoic-Cambrian miogeoclinal clastic rocks record an end to rifting and establishment of the Cordilleran miogeocline in southern California by latest Neoproterozoic to Early Cambrian time. ?? 2009 by The University of Chicago.

  13. Area/latency optimized early output asynchronous full adders and relative-timed ripple carry adders.

    PubMed

    Balasubramanian, P; Yamashita, S

    2016-01-01

    This article presents two area/latency optimized gate level asynchronous full adder designs which correspond to early output logic. The proposed full adders are constructed using the delay-insensitive dual-rail code and adhere to the four-phase return-to-zero handshaking. For an asynchronous ripple carry adder (RCA) constructed using the proposed early output full adders, the relative-timing assumption becomes necessary and the inherent advantages of the relative-timed RCA are: (1) computation with valid inputs, i.e., forward latency is data-dependent, and (2) computation with spacer inputs involves a bare minimum constant reverse latency of just one full adder delay, thus resulting in the optimal cycle time. With respect to different 32-bit RCA implementations, and in comparison with the optimized strong-indication, weak-indication, and early output full adder designs, one of the proposed early output full adders achieves respective reductions in latency by 67.8, 12.3 and 6.1 %, while the other proposed early output full adder achieves corresponding reductions in area by 32.6, 24.6 and 6.9 %, with practically no power penalty. Further, the proposed early output full adders based asynchronous RCAs enable minimum reductions in cycle time by 83.4, 15, and 8.8 % when considering carry-propagation over the entire RCA width of 32-bits, and maximum reductions in cycle time by 97.5, 27.4, and 22.4 % for the consideration of a typical carry chain length of 4 full adder stages, when compared to the least of the cycle time estimates of various strong-indication, weak-indication, and early output asynchronous RCAs of similar size. All the asynchronous full adders and RCAs were realized using standard cells in a semi-custom design fashion based on a 32/28 nm CMOS process technology.

  14. Early tracheostomy in trauma patients saves time and money.

    PubMed

    Hyde, Glendon A; Savage, Stephanie A; Zarzaur, Ben L; Hart-Hyde, Jensen E; Schaefer, Candace B; Croce, Martin A; Fabian, Timothy C

    2015-01-01

    Patients suffering traumatic brain and chest wall injuries are often difficult to liberate from the ventilator yet best timing of tracheostomy remains ill-defined. While prior studies have addressed early versus late tracheostomy, they generally suffer from the use of historical controls, which cannot account for variations in management over time. Propensity scoring can be utilized to identify controls from the same patient population, minimizing impact of confounding variables. The purpose of this study was to determine outcomes associated with early versus late tracheostomy by application of propensity scoring. Patients requiring intubation within 48h and receiving tracheostomy from January 2010 to June 2012 were identified. Early tracheostomy (ET) was a tracheostomy performed by the fifth hospital day. ET patients were matched to late tracheostomy patients (LT, tracheostomy after day 5) using propensity scoring and compared for multiple outcomes. Cost for services was calculated using average daily billing rates at our institution. One hundred and six patients were included, 53 each in the ET (mean day tracheostomy=4) and the LT (mean day tracheostomy=10) cohorts. The average age was 47 years and 94% suffered blunt injury, with an average NISS of 23.7. Patients in the ET group had significantly shorter TICU LOS (21.4 days vs. 28.6 days, p<0.0001) and significantly fewer ventilator days (16.7 days vs. 21.9, p<0.0001) compared to the LT group. ET patients also had significantly less VAP (34% vs. 64.2%, p=0.0019). In the current era of increased health-care costs, early tracheostomy significantly decreased both pulmonary morbidity and critical care resource utilization. This translates to an appreciable cost savings, at minimum $52,173 per patient and a potential total savings of $2.8million/year for the entire LT cohort. For trauma patients requiring prolonged ventilator support, early tracheostomy should be performed. Copyright © 2014 Elsevier Ltd. All rights

  15. Hurricane Mountain Formation melange: history of Cambro-Ordovician accretion of the Boundary Mountains terrane within the northern Appalachian orthotectonic zone

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boone, G.M.; Boudette, E.L.

    1985-01-01

    The Hurricane Mountain Formation (HMF) melange and associated ophiolitic and volcanogenic formations of Cambrian and lowermost Ordovician age bound the SE margin of the Precambrian Y (Helikian) Chain Lakes Massif in western Maine. HMF melange matrix, though weakly metamorphosed, contains a wide variety of exotic greenschist to amphibolite facies blocks as components of its polymictic assemblage, but blocks of high-grade cratonal rocks such as those of Chain Lakes or Grenville affinity are lacking. Formations of melange exposed in structural culminations of Cambrian and Ordovician rocks NE of the HMF in Maine and in the Fournier Group in New Brunswick aremore » lithologically similar and probably tectonically correlative with the HMF; taken together, they may delineate a common pre-Middle Ordovician tectonic boundary. The authors infer that the Hurricane Mountain and St. Daniel melange belts define the SE and NW margins of the Boundary Mountains accreted terrane (BMT), which may consist of cratonal basement of Chain Lakes affinity extending from eastern Gaspe (deBroucker and St. Julien, 1985) to north-central New Hampshire. The Laurentian continental margin, underlain by Grenville basement, underplated the NW margin of this terrane, marked by the SDF suture zone, in late Cambrian to early Ordovician time, while terranes marked by Cambrian to Tremadocian (.) lithologies dissimilar to the Boundary Mountains terrane were accreted to its outboard margin penecontemporaneously. The docking of the Boundary Mountains terrane and the initiation of its peripheral melanges are equated to the Penobscottian disturbance.« less

  16. Early Childhood Maltreatment and Girls' Sexual Behavior: The Mediating Role of Pubertal Timing.

    PubMed

    Ryan, Rebecca M; Mendle, Jane; Markowitz, Anna J

    2015-09-01

    Although links between early childhood maltreatment and girls' sexual behavior in adolescence have been well established, it is unclear whether different forms of maltreatment are differentially associated with sexual outcomes and whether distinct mechanisms explain associations across maltreatment types. Using data from National Longitudinal Study of Adolescent Health (Add Health), the present study examines whether physical abuse, sexual abuse, and physical neglect in early childhood differentially predict girls' age at first intercourse and number of sexual partners in early adulthood. The study also tests whether early pubertal timing mediates the link between early maltreatment and sexual behavior (N = 6,364). Findings indicate that early sexual and physical abuse were equally predictive of earlier age at first intercourse and a greater number of sexual partners, but that only the sexual abuse-age at first intercourse link was mediated by early puberty. These results suggest that sexual abuse and physical abuse are associated with earlier and riskier sexual behavior in girls relative to no maltreatment and to similar degrees. However, only the link between sexual abuse and sexual behavior involves a biological mechanism manifested in early pubertal timing. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  17. Early Sexual Intercourse: Prospective Associations with Adolescents Physical Activity and Screen Time

    PubMed Central

    Wijtzes, Anne; van de Bongardt, Daphne; van de Looij-Jansen, Petra; Bannink, Rienke; Raat, Hein

    2016-01-01

    Objectives To assess the prospective associations of physical activity behaviors and screen time with early sexual intercourse initiation (i.e., before 15 years) in a large sample of adolescents. Methods We used two waves of data from the Rotterdam Youth Monitor, a longitudinal study conducted in the Netherlands. The analysis sample consisted of 2,141 adolescents aged 12 to 14 years (mean age at baseline = 12.2 years, SD = 0.43). Physical activity (e.g., sports outside school), screen time (e.g., computer use), and early sexual intercourse initiation were assessed by means of self-report questionnaires. Logistic regression models were tested to assess the associations of physical activity behaviors and screen time (separately and simultaneously) with early sexual intercourse initiation, controlling for confounders (i.e., socio-demographics and substance use). Interaction effects with gender were tested to assess whether these associations differed significantly between boys and girls. Results The only physical activity behavior that was a significant predictor of early sexual intercourse initiation was sports club membership. Adolescent boys and girls who were members of a sports club) were more likely to have had early sex (OR = 2.17; 95% CI = 1.33, 3.56. Significant gender interaction effects indicated that boys who watched TV ≥2 hours/day (OR = 2.00; 95% CI = 1.08, 3.68) and girls who used the computer ≥2 hours/day (OR = 3.92; 95% CI = 1.76, 8.69) were also significantly more likely to have engaged in early sex. Conclusion These findings have implications for professionals in general pediatric healthcare, sexual health educators, policy makers, and parents, who should be aware of these possible prospective links between sports club membership, TV watching (for boys), and computer use (for girls), and early sexual intercourse initiation. However, continued research on determinants of adolescents’ early sexual initiation is needed to further contribute to

  18. Origin and implications of a thrust-bound gypsiferous unit along the western edge of Jabal Sumeini, northern Oman Mountains

    NASA Astrophysics Data System (ADS)

    Cooper, David J. W.; Ali, Mohammed Y.; Searle, Michael P.

    2018-04-01

    The Oman Mountains comprise a series of thrust sheets of Neo-Tethyan oceanic rocks that were emplaced onto the Arabian continental margin during obduction of the Semail Ophiolite during the Late Cretaceous. Three separate groups of anomalous gypsiferous bodies intrude the allochthonous units along faults over a distance of about 150 km in the Hawasina Window, Jabal Qumayrah and Jabal Sumeini. The bodies at Jabal Sumeini form a band about 4 km long and up to 100 m wide along a late-stage thrust that restacks the allochthon over a post-emplacement Maastrichtian-Palaeogene sedimentary succession. The gypsum shows evidence of flow-folding and contains numerous clasts and rafts of a range of quartzose sandstones, but with only a minor component from carbonates from the Neo-Tethyan Sumeini Group in the hanging-wall. Palaeogene limestones from the footwall succession are essentially absent. Strontium isotope ratios are high and intersect with the open ocean-water reference curve for the Late Cambrian-Ordovician and Late Miocene-Pliocene. They are also noticeably higher than the ratios from the two other gypsiferous outcrop areas in the Oman Mountains and from outcrops of Ediacaran-Early Cambrian salt domes in central Oman. However, the regional stratigraphy points towards a source of the gypsum from either an Ediacaran-Early Cambrian Ara Group salt basin or from the Lower Fars Formation (Early-Middle Miocene), and derivation of the sandstone clasts and rafts from thick Lower Palaeozoic clastic sequences. The discrepancy with the ages inferred from the strontium isotope data can be attributed to deposition of the gypsum in restricted conditions not in equilibrium with the prevailing ocean water. Two models are presented, for an Ediacaran-Early Cambrian and an Early-Middle Miocene source. While the latter cannot be wholly discounted, the stratigraphic and structural context point more strongly towards an Ediacaran-Early Cambrian Ara Group source of the gypsum. This was

  19. Consensus in a Precambrian garden

    NASA Astrophysics Data System (ADS)

    Maggs, William Ward

    At the Precambrian-Cambrian boundary, the course of life on Earth underwent a dramatic change that culminated in the rise of predators and other complex animals, a group of paleontologists agreed at a conferece last week.Just prior to 590 million years ago, the ecology of life in the oceans was very simple; soft-shelled multicellular animals called Ediacara lived in apparent harmony with vast mats o f bacteria and algae that covered the seafloor, dependent on the photosynthesis or chemosynthesis of their one-celled hosts for their existence. According to the consensus reached by the scientists, this symbiotic and apparently global “Garden of Ediacara” fell early in the Cambrian Period, as the mats declined and food chains multiplied with new animals that, for the first time in Earth's history, preyed on other living things.

  20. Pubertal Timing and Early Sexual Intercourse in the Offspring of Teenage Mothers

    ERIC Educational Resources Information Center

    De Genna, Natacha M.; Larkby, Cynthia; Cornelius, Marie D.

    2011-01-01

    Early puberty is associated with stressful family environments, early sexual intercourse, and teenage pregnancy. We examined pubertal timing and sexual debut among the 14-year-old offspring of teenage mothers. Mothers (71% Black, 29% White) were recruited as pregnant teenagers (12-18 years old). Data were collected during pregnancy and when…

  1. Early Middle Ordovician evidence for land plants in Argentina (eastern Gondwana).

    PubMed

    Rubinstein, C V; Gerrienne, P; de la Puente, G S; Astini, R A; Steemans, P

    2010-10-01

    • The advent of embryophytes (land plants) is among the most important evolutionary breakthroughs in Earth history. It irreversibly changed climates and biogeochemical processes on a global scale; it allowed all eukaryotic terrestrial life to evolve and to invade nearly all continental environments. Before this work, the earliest unequivocal embryophyte traces were late Darriwilian (late Middle Ordovician; c. 463-461 million yr ago (Ma)) cryptospores from Saudi Arabia and from the Czech Republic (western Gondwana). • Here, we processed Dapingian (early Middle Ordovician, c. 473-471 Ma) palynological samples from Argentina (eastern Gondwana). • We discovered a diverse cryptospore assemblage, including naked and envelope-enclosed monads and tetrads, representing five genera. • Our discovery reinforces the earlier suggestion that embryophytes first evolved in Gondwana. It indicates that the terrestrialization of plants might have begun in the eastern part of Gondwana. The diversity of the Dapingian assemblage implies an earlier, Early Ordovician or even Cambrian, origin of embryophytes. Dapingian to Aeronian (Early Silurian) cryptospore assemblages are similar, suggesting that the rate of embryophyte evolution was extremely slow during the first c. 35-45 million yr of their diversification. The Argentinean cryptospores predate other cryptospore occurrences by c. 8-12 million yr, and are currently the earliest evidence of plants on land. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

  2. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian-Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland)

    NASA Astrophysics Data System (ADS)

    Kosakowski, Paweł; Kotarba, Maciej J.; Piestrzyński, Adam; Shogenova, Alla; Więcław, Dariusz

    2017-03-01

    We present geochemical characteristics of the Lower Palaeozoic shales deposited in the Baltic Basin and Podlasie Depression. In the study area, this strata are represented by the Upper Cambrian-Lower Ordovician Alum Shale recognized in southern Scandinavia and Polish offshore and a equivalent the Lower Tremadocian Dictyonema Shale from the northern Estonia and the Podlasie Depression in Poland. Geochemical analyses reveal that the Alum Shale and Dictyonema Shale present high contents of organic carbon. These deposits have the best source quality among the Lower Palaeozoic strata, and they are the best source rocks in the Baltic region. The bituminous shales complex has TOC contents up to ca. 22 wt%. The analysed rocks contain low-sulphur, oil-prone Type-II kerogen deposited in anoxic or sub-oxic conditions. The maturity of the Alum and Dictyonema Shales changes gradually, from the east and north-east to the west and south-west, i.e. in the direction of the Tornquist-Teisseyre Zone. Samples, located in the seashore of Estonia and in the Podlasie region, are immature and in the initial phase of "oil window". The mature shales were found in the central offshore part of the Polish Baltic Basin, and the late mature and overmature are located in the western part of the Baltic Basin. The Alum and Dictyonema Shales are characterized by a high grade of radioactive elements, especially uranium. The enrichment has a syngenetic or early diagenetic origin. The measured content of uranium reached up to 750 ppm and thorium up to 37 ppm.

  3. Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna

    PubMed Central

    Brayard, Arnaud; Krumenacker, L. J.; Botting, Joseph P.; Jenks, James F.; Bylund, Kevin G.; Fara, Emmanuel; Vennin, Emmanuelle; Olivier, Nicolas; Goudemand, Nicolas; Saucède, Thomas; Charbonnier, Sylvain; Romano, Carlo; Doguzhaeva, Larisa; Thuy, Ben; Hautmann, Michael; Stephen, Daniel A.; Thomazo, Christophe; Escarguel, Gilles

    2017-01-01

    In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era. PMID:28246643

  4. Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.

    PubMed

    Brayard, Arnaud; Krumenacker, L J; Botting, Joseph P; Jenks, James F; Bylund, Kevin G; Fara, Emmanuel; Vennin, Emmanuelle; Olivier, Nicolas; Goudemand, Nicolas; Saucède, Thomas; Charbonnier, Sylvain; Romano, Carlo; Doguzhaeva, Larisa; Thuy, Ben; Hautmann, Michael; Stephen, Daniel A; Thomazo, Christophe; Escarguel, Gilles

    2017-02-01

    In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage-the Paris Biota-from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200-million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.

  5. On the Early-Time Excess Emission in Hydrogen-Poor Superluminous Supernovae

    NASA Technical Reports Server (NTRS)

    Vreeswijk, Paul M.; Leloudas, Giorgos; Gal-Yam, Avishay; De Cia, Annalisa; Perley, Daniel A.; Quimby, Robert M.; Waldman, Roni; Sullivan, Mark; Yan, Lin; Ofek, Eran O.; hide

    2017-01-01

    We present the light curves of the hydrogen-poor super-luminous supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the (intermediate) Palomar Transient Factory. Both show excess emission at early times and a slowly declining light curve at late times. The early bump in PTF 12dam is very similar in duration (approximately 10 days) and brightness relative to the main peak (23 mag fainter) compared to that observed in other SLSNe I. In contrast, the long-duration (greater than 30 days) early excess emission in iPTF 13dcc, whose brightness competes with that of the main peak, appears to be of a different nature. We construct bolometric light curves for both targets, and fit a variety of light-curve models to both the early bump and main peak in an attempt to understand the nature of these explosions. Even though the slope of the late-time decline in the light curves of both SLSNe is suggestively close to that expected from the radioactive decay of 56Ni and 56Co, the amount of nickel required to power the full light curves is too large considering the estimated ejecta mass. The magnetar model including an increasing escape fraction provides a reasonable description of the PTF 12dam observations. However, neither the basic nor the double-peaked magnetar model is capable of reproducing the light curve of iPTF 13dcc. A model combining a shock breakout in an extended envelope with late-time magnetar energy injection provides a reasonable fit to the iPTF 13dcc observations. Finally, we find that the light curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the model involving interaction with the circumstellar medium.

  6. On The Early-Time Excess Emission In Hydrogen-Poor Superluminous Supernovae

    DOE PAGES

    Vreeswijk, Paul M.; Leloudas, Giorgos; Gal-Yam, Avishay; ...

    2017-01-18

    Here, we present the light curves of the hydrogen-poor superluminous supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the (intermediate) Palomar Transient Factory. Both show excess emission at early times and a slowly declining light curve at late times. The early bump in PTF 12dam is very similar in duration (~10 days) and brightness relative to the main peak (2-3 mag fainter) compared to that observed in other SLSNe I. In contrast, the long-duration ( > 30 days) early excess emission in iPTF 13dcc, whose brightness competes with that of the main peak, appears to be of amore » different nature. We construct bolometric light curves for both targets, and fit a variety of light-curve models to both the early bump and main peak in an attempt to understand the nature of these explosions. Even though the slope of the late-time decline in the light curves of both SLSNe is suggestively close to that expected from the radioactive decay of 56Ni and 56Co, the amount of nickel required to power the full light curves is too large considering the estimated ejecta mass. The magnetar model including an increasing escape fraction provides a reasonable description of the PTF 12dam observations. However, neither the basic nor the double-peaked magnetar model is capable of reproducing the light curve of iPTF 13dcc. A model combining a shock breakout in an extended envelope with late-time magnetar energy injection provides a reasonable fit to the iPTF 13dcc observations. Finally, we find that the light curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the model involving interaction with the circumstellar medium.« less

  7. ON THE EARLY-TIME EXCESS EMISSION IN HYDROGEN-POOR SUPERLUMINOUS SUPERNOVAE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vreeswijk, Paul M.; Leloudas, Giorgos; Gal-Yam, Avishay

    2017-01-20

    We present the light curves of the hydrogen-poor superluminous supernovae (SLSNe I) PTF 12dam and iPTF 13dcc, discovered by the (intermediate) Palomar Transient Factory. Both show excess emission at early times and a slowly declining light curve at late times. The early bump in PTF 12dam is very similar in duration (∼10 days) and brightness relative to the main peak (2–3 mag fainter) compared to that observed in other SLSNe I. In contrast, the long-duration (>30 days) early excess emission in iPTF 13dcc, whose brightness competes with that of the main peak, appears to be of a different nature. Wemore » construct bolometric light curves for both targets, and fit a variety of light-curve models to both the early bump and main peak in an attempt to understand the nature of these explosions. Even though the slope of the late-time decline in the light curves of both SLSNe is suggestively close to that expected from the radioactive decay of {sup 56}Ni and {sup 56}Co, the amount of nickel required to power the full light curves is too large considering the estimated ejecta mass. The magnetar model including an increasing escape fraction provides a reasonable description of the PTF 12dam observations. However, neither the basic nor the double-peaked magnetar model is capable of reproducing the light curve of iPTF 13dcc. A model combining a shock breakout in an extended envelope with late-time magnetar energy injection provides a reasonable fit to the iPTF 13dcc observations. Finally, we find that the light curves of both PTF 12dam and iPTF 13dcc can be adequately fit with the model involving interaction with the circumstellar medium.« less

  8. New paleomagnetic data from Siberia: Non-uniformitarian geomagnetic field around the Proterozoic-Phanerozoic boundary?

    NASA Astrophysics Data System (ADS)

    Pavlov, V.; Shatsillo, A.; Kouznetsov, N.; Gazieva, E.

    2017-12-01

    There is a range of evidence, mainly from sedimentary and volcanic rocks of the Laurentia and Baltica cratons, that argue for the anomalous character of the Ediacaran-Early Cambrian paleomagnetic record. This feature could be linked either to some peculiarities of the paleomagnetic record itself or to some unusual geophysical event that would have taken place around the Proterozoic-Phanerozoic boundary (e.g., true polar wander or nonuniformitarian geomagnetic field behavior). In the latter case, the traces of this event should be observed in Ediacaran-Early Cambrian rocks anywhere there is a possibility to observe a primary paleomagnetic signal. In previous work, we reported results that suggested an anomalous paleomagnetic record in Siberian Ediacaran-Lower Cambrian rocks. Here we present new Siberian data that indicate a very high geomagnetic reversal frequency during this period and the coexistence of two very different paleomagnetic directions. We speculate that these features could be due either to a near-equatorial geomagnetic dipole during the polarity transitions or to alternation between axial and near equatorial dipoles not directly linked with polarity reversals.

  9. Stratigraphy and depositional environment of upper Cambrian Red Lion Formation, southwestern Montana

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hayden, L.L.; Bush, J.H.

    1987-08-01

    The Red Lion Formation was examined along a northwest-southeast transect from Missoula to Bozeman, Montana. Lateral equivalents are the Snowy Range Formation east of Bozeman and the upper Fishtrap Dolomite in northwest Montana. The basal Dry Creek Member (0-5 m) consists of shale interbedded with quartz siltstones and sandstones. The overlying Sage Member, up to 115 meters in thickness, is characterized by ribbon carbonate beds containing lime mudstone and quartzose calcisiltite couplets arranged in fining-upward sequences 1-5 cm thick. Couplets are interlayered in places with thin (1-5 cm) to medium bedded (6-70 cm) units of laminated and non-laminated calcareous siltstones,more » flat-pebble conglomerates, trilobite packstones, cryptalgal boundstones, bioturbated lime mudstones and shales. In places, the upper Sage contains columnar and domal algal features. The Red Lion Formation is considered to be one Grand Cycle with the Dry Creek representing a lower inner detrital half-cycle and the Sage an upper carbonate half-cycle. The Dry Creek formed as the result of a westward clastic pulse from the inner detrital belt across an intrashelf basin onto outer middle carbonate peritidal complexes of the underlying Pilgrim Formation. Lower Sage ribbon rocks were deposited in storm-crossed, below wave-base areas. During deposition of the upper Sage, shallowing formed discontinuous algal-peritidal complexes over much of western and central Montana. These complexes were less extensive than earlier Cambrian buildups owing to slower rates of basin subsidence and clastic input suppressing carbonate production.« less

  10. Paleomagnetism of Early Paleozoic Rocks from the de Long Archipelago and Tectonics of the New Siberian Islands Terrane

    NASA Astrophysics Data System (ADS)

    Metelkin, D. V.; Chernova, A. I.; Matushkin, N. Y.; Vernikovskiy, V. A.

    2017-12-01

    The De Long archipelago is located to the north of the Anjou archipelago as a part of a large group between the Laptev Sea and the East Siberian Sea - the New Siberian Islands and consists of Jeannette Island, Bennett Island and Henrietta Island. These islands have been shown to be part of a single continental terrane, whose tectonic history was independent of other continental masses at least since the Ordovician. Paleomagnetic and precise geological data for the De Long archipelago were absent until recently. Only in 2013 special international field trips to the De Long Islands could be organized and geological, isotope-geochronological and paleomagnetic studies were carried out.On Jeannette Island a volcanic-sedimentary sequence intruded by mafic dikes was described. The age of these dikes is more likely Early Ordovician, close to 480 Ma, as evidenced by the results of our 40Ar/39Ar and paleomagnetic investigations of the dolerites as well as the result from detrital zircons in the host rocks published before. On Bennett Island, there are widespread Cambrian-Ordovician mainly terrigenous rocks. Paleomagnetic results from these rocks characterize the paleogeographic position of the De Long archipelago at 465 Ma and perhaps at 530 Ma, although there is no evidence for the primary origin of magnetization for the latter. On Henrietta Island the Early Cambrian volcanic-sedimentary section was investigated. A paleomagnetic pole for 520 Ma was obtained and confirmed by new 40Ar/39Ar results. Adding to our previous paleomagnetic data for the Anjou archipelago the extended variant of the apparent polar wander path for the New Siberian Island terrane was created. The established paleolatitudes define its location in the equatorial and subtropical zone no higher than 40 degrees during the Early Paleozoic. Because there are no good confirmations for true polarity and related geographic hemisphere we present two possibilities for tectonic reconstruction. But both these

  11. [The application of the prospective space-time statistic in early warning of infectious disease].

    PubMed

    Yin, Fei; Li, Xiao-Song; Feng, Zi-Jian; Ma, Jia-Qi

    2007-06-01

    To investigate the application of prospective space-time scan statistic in the early stage of detecting infectious disease outbreaks. The prospective space-time scan statistic was tested by mimicking daily prospective analyses of bacillary dysentery data of Chengdu city in 2005 (3212 cases in 102 towns and villages). And the results were compared with that of purely temporal scan statistic. The prospective space-time scan statistic could give specific messages both in spatial and temporal. The results of June indicated that the prospective space-time scan statistic could timely detect the outbreaks that started from the local site, and the early warning message was powerful (P = 0.007). When the merely temporal scan statistic for detecting the outbreak was sent two days later, and the signal was less powerful (P = 0.039). The prospective space-time scan statistic could make full use of the spatial and temporal information in infectious disease data and could timely and effectively detect the outbreaks that start from the local sites. The prospective space-time scan statistic could be an important tool for local and national CDC to set up early detection surveillance systems.

  12. Elucidating the mechanisms linking early pubertal timing, sexual activity, and substance use for maltreated versus nonmaltreated adolescents.

    PubMed

    Negriff, Sonya; Brensilver, Matthew; Trickett, Penelope K

    2015-06-01

    To test models linking pubertal timing, peer substance use, sexual behavior, and substance use for maltreated versus comparison adolescents. Three theoretical mechanisms were tested: (1) peer influence links early pubertal timing to later sexual behavior and substance use; (2) early maturers engage in substance use on their own and then select substance-using friends; or (3) early maturers initiate sexual behaviors which lead them to substance-using peers. The data came from a longitudinal study of the effects of child maltreatment on adolescent development (303 maltreated and 151 comparison adolescents; age, 9-13 years at initial wave). Multiple-group structural equation models tested the hypotheses across three time points including variables of pubertal timing, perception of peer substance use, sexual behavior, and self-reported substance use. Early pubertal timing was associated with substance-using peers only for maltreated adolescents, indicating the mediation path from early pubertal timing through substance-using peers to subsequent adolescent substance use and sexual behavior only holds for maltreated adolescents. Mediation via sexual behavior was significant for both maltreated and comparison adolescents. This indicates that sexual behavior may be a more universal mechanism linking early maturation with risky friends regardless of adverse life experiences. The findings are a step toward elucidating the developmental pathways from early puberty to risk behavior and identifying early experiences that may alter mediation effects. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  13. Biochemical methane potential (BMP) tests: Reducing test time by early parameter estimation.

    PubMed

    Da Silva, C; Astals, S; Peces, M; Campos, J L; Guerrero, L

    2018-01-01

    Biochemical methane potential (BMP) test is a key analytical technique to assess the implementation and optimisation of anaerobic biotechnologies. However, this technique is characterised by long testing times (from 20 to >100days), which is not suitable for waste utilities, consulting companies or plants operators whose decision-making processes cannot be held for such a long time. This study develops a statistically robust mathematical strategy using sensitivity functions for early prediction of BMP first-order model parameters, i.e. methane yield (B 0 ) and kinetic constant rate (k). The minimum testing time for early parameter estimation showed a potential correlation with the k value, where (i) slowly biodegradable substrates (k≤0.1d -1 ) have a minimum testing times of ≥15days, (ii) moderately biodegradable substrates (0.1times between 8 and 15 days, and (iii) rapidly biodegradable substrates (k≥0.2d -1 ) have testing times lower than 7days. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Permian-Early Triassic tectonics and stratigraphy of the Karoo Supergroup in northwestern Mozambique

    NASA Astrophysics Data System (ADS)

    Bicca, Marcos Müller; Philipp, Ruy Paulo; Jelinek, Andrea Ritter; Ketzer, João Marcelo Medina; dos Santos Scherer, Claiton Marlon; Jamal, Daúd Liace; dos Reis, Adriano Domingos

    2017-06-01

    The Gondwana continent was the base of great basin inception, sedimentation and magmatism throughout the Cambrian to Middle Jurassic periods. The northwestern Mozambique igneous and metamorphic basement assemblages host the NW-trending Moatize Minjova Basin, which has great economic potential for coal and gas mining. This rift basin was activated by an S-SW stress field during the Early Permian period, as constrained by regional and field scale structural data. Tectonically induced subsidence in the basin, from the reactivation of NW-SE and NNE-SSW regional structures is well recorded by faults, folds and synsedimentary fractures within the Early Late Permian Moatize Formation. NW-SE, N-S and NE-SW field structures consist of post-Karoo reactivation patterns related to a NNE-SSW extension produced by the Pangea breakup and early inception stages of the Great East African Rift System. The Early Late Permian sequences of the Moatize-Minjova Basin are composed of fluvial meandering, coal-bearing beds of the Moatize Formation, which comprises mostly floodplain, crevasse splay and fluvial channel lithofacies associations, deposited in a cyclic pattern. This sequence was overlapped by a multiple-story, braided fluvial plain sequence of the Matinde Formation (Late Permian - Early Triassic). Lithofacies associations in the Matinde Formation and its internal relationships suggest deposition of poorly channelized braided alluvial plain in which downstream and probably lateral accretion macroforms alternate with gravity flow deposits. NW paleoflow measurements suggest that Permian fluvial headwaters were located somewhere southeast of the study area, possibly between the African and Antarctic Precambrian highlands.

  15. Elucidating the mechanisms linking early pubertal timing, sexual activity, and substance use for maltreated versus nonmaltreated adolescents

    PubMed Central

    Negriff, Sonya; Brensilver, Matthew; Trickett, Penelope K.

    2015-01-01

    Purpose To test models linking pubertal timing, peer substance use, sexual behavior, and substance use for maltreated versus comparison adolescents. Three theoretical mechanisms were tested: 1) peer influence links early pubertal timing to later sexual behavior and substance use, 2) early maturers engage in substance use on their own and then select substance-using friends, or 3) early maturers initiate sexual behaviors which leads them to substance-using peers. Methods The data came from a longitudinal study of the effects of child maltreatment on adolescent development (303 maltreated and 151 comparison adolescents; age: 9–13 years at initial wave). Multiple-group structural equation models tested the hypotheses across three timepoints including variables of pubertal timing, perception of peer substance use, sexual behavior, and self-reported substance use. Results Early pubertal timing was associated with substance-using peers only for maltreated adolescents, indicating the mediation path from early pubertal timing through substance-using peers to subsequent adolescent substance use and sexual behavior only holds for maltreated adolescents. Mediation via sexual behavior was significant for both maltreated and comparison adolescents. This indicates that sexual behavior may be a more universal mechanism linking early maturation with risky friends regardless of adverse life experiences. Conclusions The findings are a step toward elucidating the developmental pathways from early puberty to risk behavior and identifying early experiences that may alter mediation effects. PMID:26003577

  16. Hallucigenia's head and the pharyngeal armature of early ecdysozoans.

    PubMed

    Smith, Martin R; Caron, Jean-Bernard

    2015-07-02

    The molecularly defined clade Ecdysozoa comprises the panarthropods (Euarthropoda, Onychophora and Tardigrada) and the cycloneuralian worms (Nematoda, Nematomorpha, Priapulida, Loricifera and Kinorhyncha). These disparate phyla are united by their means of moulting, but otherwise share few morphological characters--none of which has a meaningful fossilization potential. As such, the early evolutionary history of the group as a whole is largely uncharted. Here we redescribe the 508-million-year-old stem-group onychophoran Hallucigenia sparsa from the mid-Cambrian Burgess Shale. We document an elongate head with a pair of simple eyes, a terminal buccal chamber containing a radial array of sclerotized elements, and a differentiated foregut that is lined with acicular teeth. The radial elements and pharyngeal teeth resemble the sclerotized circumoral elements and pharyngeal teeth expressed in tardigrades, stem-group euarthropods and cycloneuralian worms. Phylogenetic results indicate that equivalent structures characterized the ancestral panarthropod and, seemingly, the ancestral ecdysozoan, demonstrating the deep homology of panarthropod and cycloneuralian mouthparts, and providing an anatomical synapomorphy for the ecdysozoan supergroup.

  17. Isotopic and geochemical characterization of fossil brines of the Cambrian Mt. Simon Sandstone and Ironton-Galesville Formation from the Illinois Basin, USA

    NASA Astrophysics Data System (ADS)

    Labotka, Dana M.; Panno, Samuel V.; Locke, Randall A.; Freiburg, Jared T.

    2015-09-01

    Geochemical and isotopic characteristics of deep-seated saline groundwater provide valuable insight into the origin and evolving composition, water-rock interaction, and mixing potential of fossil brines. Such information may yield insight into intra- and interbasinal brine movement and relationships between brine evolution and regional groundwater flow systems. This investigation reports on the δ18O and δD composition and activity values, 87Sr/86Sr ratios and Sr concentrations, and major ion concentrations of the Cambrian-hosted brines of the Mt. Simon Sandstone and Ironton-Galesville Formation and discusses the evolution of these brines as they relate to other intracontinental brines. Brines in the Illinois Basin are dominated by Na-Ca-Cl-type chemistry. The Mt. Simon and overlying Ironton-Galesville brines exhibit total dissolved solids concentrations of ∼195,000 mg/L and ∼66,270 mg/L, respectively. The δD of brine composition of the Mt. Simon ranges from -34‰ to -22‰ (V-SMOW), and the Ironton-Galesville is ∼-53.2‰ (V-SMOW). The δ18O composition of the Mt. Simon brine ranges from -5.0‰ to -2.8‰ (V-SMOW), and the Ironton-Galesville brine is ∼-6.9‰ (V-SMOW). The 87Sr/86Sr values in the Mt. Simon brine range from 0.7110 to 0.7116. The less radiogenic Ironton-Galesville brine has an average 87Sr/86Sr value of 0.7107. Evaluation of δ18O and δD composition and activities and 87Sr/86Sr ratios suggests that the Mt. Simon brine is likely connate seawater and recirculating deep-seated brines that have been diluted with meteoric water and influenced by the dissolution of evaporites with a minimal halite contribution based on Cl/Br ratios. The Ironton-Galesville brine is also likely originally connate seawater that mixed with other brines and meteoric waters, including possibly Pleistocene glacial recharge. The Ca-excess vs. Na-deficiency comparison with the Basinal Fluid Line suggests the Mt. Simon and Ironton-Galesville brines have been

  18. Uncertainty in the Timing of Origin of Animals and the Limits of Precision in Molecular Timescales

    PubMed Central

    dos Reis, Mario; Thawornwattana, Yuttapong; Angelis, Konstantinos; Telford, Maximilian J.; Donoghue, Philip C.J.; Yang, Ziheng

    2015-01-01

    Summary The timing of divergences among metazoan lineages is integral to understanding the processes of animal evolution, placing the biological events of species divergences into the correct geological timeframe. Recent fossil discoveries and molecular clock dating studies have suggested a divergence of bilaterian phyla >100 million years before the Cambrian, when the first definite crown-bilaterian fossils occur. Most previous molecular clock dating studies, however, have suffered from limited data and biases in methodologies, and virtually all have failed to acknowledge the large uncertainties associated with the fossil record of early animals, leading to inconsistent estimates among studies. Here we use an unprecedented amount of molecular data, combined with four fossil calibration strategies (reflecting disparate and controversial interpretations of the metazoan fossil record) to obtain Bayesian estimates of metazoan divergence times. Our results indicate that the uncertain nature of ancient fossils and violations of the molecular clock impose a limit on the precision that can be achieved in estimates of ancient molecular timescales. For example, although we can assert that crown Metazoa originated during the Cryogenian (with most crown-bilaterian phyla diversifying during the Ediacaran), it is not possible with current data to pinpoint the divergence events with sufficient accuracy to test for correlations between geological and biological events in the history of animals. Although a Cryogenian origin of crown Metazoa agrees with current geological interpretations, the divergence dates of the bilaterians remain controversial. Thus, attempts to build evolutionary narratives of early animal evolution based on molecular clock timescales appear to be premature. PMID:26603774

  19. Mechanism for Burgess Shale-type preservation

    PubMed Central

    Gaines, Robert R.; Hammarlund, Emma U.; Hou, Xianguang; Qi, Changshi; Gabbott, Sarah E.; Zhao, Yuanlong; Peng, Jin; Canfield, Donald E.

    2012-01-01

    Exceptionally preserved fossil biotas of the Burgess Shale and a handful of other similar Cambrian deposits provide rare but critical insights into the early diversification of animals. The extraordinary preservation of labile tissues in these geographically widespread but temporally restricted soft-bodied fossil assemblages has remained enigmatic since Walcott’s initial discovery in 1909. Here, we demonstrate the mechanism of Burgess Shale-type preservation using sedimentologic and geochemical data from the Chengjiang, Burgess Shale, and five other principal Burgess Shale-type deposits. Sulfur isotope evidence from sedimentary pyrites reveals that the exquisite fossilization of organic remains as carbonaceous compressions resulted from early inhibition of microbial activity in the sediments by means of oxidant deprivation. Low sulfate concentrations in the global ocean and low-oxygen bottom water conditions at the sites of deposition resulted in reduced oxidant availability. Subsequently, rapid entombment of fossils in fine-grained sediments and early sealing of sediments by pervasive carbonate cements at bed tops restricted oxidant flux into the sediments. A permeability barrier, provided by bed-capping cements that were emplaced at the seafloor, is a feature that is shared among Burgess Shale-type deposits, and resulted from the unusually high alkalinity of Cambrian oceans. Thus, Burgess Shale-type preservation of soft-bodied fossil assemblages worldwide was promoted by unique aspects of early Paleozoic seawater chemistry that strongly impacted sediment diagenesis, providing a fundamentally unique record of the immediate aftermath of the “Cambrian explosion.” PMID:22392974

  20. Relations between extensional tectonics and magmatism within the Southern Oklahoma aulacogen

    NASA Technical Reports Server (NTRS)

    Mcconnell, D. A.; Gilbert, M. C.

    1985-01-01

    Variations in the geometry, distribution and thickness of Cambrian igneous and sedimentary units within southwest Oklahoma are related to a late Proterozoic - early Paleozoic rifting event which formed the Southern Oklahoma aulacogen. These rock units are exposed in the Wichita Mountains, southwest Olkahoma, located on the northern margin of a Proterozoic basin, identified in the subsurface by COCORP reflection data. Overprinting of the Cambrian extensional event by Pennyslvanian tectonism obsured the influence of pre-existing basement structures and contrasting basement lithologies upon the initial development of the aulacogen.

  1. First-time mothers' experiences of early labour in Italian maternity care services.

    PubMed

    Cappelletti, Giulia; Nespoli, Antonella; Fumagalli, Simona; Borrelli, Sara E

    2016-03-01

    The aim of this study is to explore first-time mothers' experiences of early labour in Italian maternity care services when admitted to hospital or advised to return home after maternity triage assessment. The study was conducted in a second-level maternity hospital in northern Italy with an obstetric unit for both low- and high-risk women. The participants included 15 first-time mothers in good general health with spontaneous labour at term of a low-risk pregnancy who accessed maternity triage during early labour, and were either admitted to hospital or advised to return home. A qualitative interpretive phenomenological study was conducted. A face-to-face recorded semi-structured interview was conducted with each participant 48-72h after birth. Four key themes emerged from the interviews: (a) recognising signs of early labour; (b) coping with pain at home; (c) seeking reassurance from healthcare professionals; and (d) being admitted to hospital versus returning home. Uncertainty about the progression of labour and the need for reassurance were cited by women as the main reasons for hospital visit in early labour. An ambivalent feeling was reported by the participants when admitted to hospital in early labour. In fact, while the women felt reassured in the first instance, some women subsequently felt dissatisfied due to the absence of one-to-one dedicated care during early labour. When advised to return home, a number of women reported feelings of disappointment, anger, fear, discouragement and anxiety about not being admitted to hospital; however, some of these women reported a subsequent feeling of comfort due to being at home and putting in place the suggestions made by the midwives during the maternity triage assessment. The guidance provided by midwives during triage assessment seemed to be the key factor influencing women׳s satisfaction when advised either to return home or to stay at the hospital during early labour. During antenatal classes and clinics

  2. Mothers' Time with Infant and Time in Employment as Predictors of Mother-Child Relationships and Children's Early Development

    ERIC Educational Resources Information Center

    Huston, Aletha C.; Rosenkrantz Aronson, Stacey

    2005-01-01

    This study tested predictions from economic and developmental theories that maternal time with an infant is important for mother-child relationships and children's development, using time-use diaries for mothers of 7- to 8-month-old infants from the National Institute of Child Health and Human Development Study of Early Child Care (N=1,053).…

  3. Exceptionally Preserved Cambrian Trilobite Digestive System Revealed in 3D by Synchrotron-Radiation X-Ray Tomographic Microscopy

    PubMed Central

    Eriksson, Mats E.; Terfelt, Fredrik

    2012-01-01

    The Cambrian ‘Orsten’ fauna comprises exceptionally preserved and phosphatised microscopic arthropods. The external morphology of these fossils is well known, but their internal soft-tissue anatomy has remained virtually unknown. Here, we report the first non-biomineralised tissues from a juvenile polymerid trilobite, represented by digestive structures, glands, and connective strands harboured in a hypostome from the Swedish ‘Orsten’ fauna. Synchrotron-radiation X-ray tomographic microscopy enabled three-dimensional internal recordings at sub-micrometre resolution. The specimen provides the first unambiguous evidence for a J-shaped anterior gut and the presence of a crop with a constricted alimentary tract in the Trilobita. Moreover, the gut is Y-shaped in cross section, probably due to a collapsed lumen of that shape, another feature which has not previously been observed in trilobites. The combination of anatomical features suggests that the trilobite hypostome is functionally analogous to the labrum of euarthropods and that it was a sophisticated element closely integrated with the digestive system. This study also briefly addresses the preservational bias of the ‘Orsten’ fauna, particularly the near-absence of polymerid trilobites, and the taphonomy of the soft-tissue-harbouring hypostome. PMID:22558180

  4. Exceptionally preserved Cambrian trilobite digestive system revealed in 3D by synchrotron-radiation X-ray tomographic microscopy.

    PubMed

    Eriksson, Mats E; Terfelt, Fredrik

    2012-01-01

    The Cambrian 'Orsten' fauna comprises exceptionally preserved and phosphatised microscopic arthropods. The external morphology of these fossils is well known, but their internal soft-tissue anatomy has remained virtually unknown. Here, we report the first non-biomineralised tissues from a juvenile polymerid trilobite, represented by digestive structures, glands, and connective strands harboured in a hypostome from the Swedish 'Orsten' fauna. Synchrotron-radiation X-ray tomographic microscopy enabled three-dimensional internal recordings at sub-micrometre resolution. The specimen provides the first unambiguous evidence for a J-shaped anterior gut and the presence of a crop with a constricted alimentary tract in the Trilobita. Moreover, the gut is Y-shaped in cross section, probably due to a collapsed lumen of that shape, another feature which has not previously been observed in trilobites. The combination of anatomical features suggests that the trilobite hypostome is functionally analogous to the labrum of euarthropods and that it was a sophisticated element closely integrated with the digestive system. This study also briefly addresses the preservational bias of the 'Orsten' fauna, particularly the near-absence of polymerid trilobites, and the taphonomy of the soft-tissue-harbouring hypostome.

  5. Exploring the utility of real-time hydrologic data for landslide early warning

    NASA Astrophysics Data System (ADS)

    Mirus, B. B.; Smith, J. B.; Becker, R.; Baum, R. L.; Koss, E.

    2017-12-01

    Early warning systems can provide critical information for operations managers, emergency planners, and the public to help reduce fatalities, injuries, and economic losses due to landsliding. For shallow, rainfall-triggered landslides early warning systems typically use empirical rainfall thresholds, whereas the actual triggering mechanism involves the non-linear hydrological processes of infiltration, evapotranspiration, and hillslope drainage that are more difficult to quantify. Because hydrologic monitoring has demonstrated that shallow landslides are often preceded by a rise in soil moisture and pore-water pressures, some researchers have developed early warning criteria that attempt to account for these antecedent wetness conditions through relatively simplistic storage metrics or soil-water balance modeling. Here we explore the potential for directly incorporating antecedent wetness into landslide early warning criteria using recent landslide inventories and in-situ hydrologic monitoring near Seattle, WA, and Portland, OR. We use continuous, near-real-time telemetered soil moisture and pore-water pressure data measured within a few landslide-prone hillslopes in combination with measured and forecasted rainfall totals to inform easy-to-interpret landslide initiation thresholds. Objective evaluation using somewhat limited landslide inventories suggests that our new thresholds based on subsurface hydrologic monitoring and rainfall data compare favorably to the capabilities of existing rainfall-only thresholds for the Seattle area, whereas there are no established rainfall thresholds for the Portland area. This preliminary investigation provides a proof-of-concept for the utility of developing landslide early warning criteria in two different geologic settings using real-time subsurface hydrologic measurements from in-situ instrumentation.

  6. Supercontinents, True Polar Wander, and Paleogeography of the Slave Craton

    NASA Astrophysics Data System (ADS)

    Mitchell, Ross Nelson

    The supercontinent cycle, which may have been operational throughout most of Earth history, describes not only the kinematics associated with the suturing and rifting of continents via plate tectonics but also the wholesale organization of mantle convection patterns, which has consequences for long-term geodynamics and true polar wander (TPW). Based on both newly acquired paleomagnetic data and regional or global syntheses, this thesis generates paleogeographic maps spanning 2 billion years and evaluates how such empirical constraints inform plate kinematics and TPW. Prior to Pangea, the latest supercontinent, paleomagnetism is the only quantitative method for reconstructing continents. Comparing high-quality data from continents considered central to Nuna, possibly Earth's first supercontinent, reconstructs the core of the hypothesized Paleo-Mesoproterozoic supercontinent for the first time. A global paleomagnetic synthesis spanning the past three supercontinents yields evidence for periods of oscillatory TPW following each supercontinent that can be used to infer a geometric pattern to supercontinent cycles and constrain absolute paleolongitude. Relative to post-Pangea oscillations, large-amplitude TPW is implied for older events if evidence for early TPW is to be believed. Possibly the last large (˜60°) TPW event occurred during the Cambrian explosion of animal life. A new detailed Early Cambrian magnetostratigraphy from the Amadeus Basin of Australia indicates a rapid Early Cambrian rotation of Gondwana, still permitting the possibility that at least one large-amplitude TPW event occurred in Phanerozoic time. Investigating earlier and even larger possible TPW episodes, several cases are identified where interpreting large paleomagnetic oscillations as TPW permits regional geologic interpretations to be honored. Allowing for only minor tectonic motion of Laurentia and large-scale TPW, large amounts of paleomagnetic motion observed can be reconciled with

  7. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution.

    PubMed

    Fritz, H; Abdelsalam, M; Ali, K A; Bingen, B; Collins, A S; Fowler, A R; Ghebreab, W; Hauzenberger, C A; Johnson, P R; Kusky, T M; Macey, P; Muhongo, S; Stern, R J; Viola, G

    2013-10-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara-Congo-Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian-Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite-Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650-620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo-Tanzania-Bangweulu Cratons and the Zimbabwe-Kalahari Craton. They closed during the ∼600-500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600-550 Ma extension is recorded in the Arabian-Nubian Shield and the Eastern Granulite-Cabo Delgado Nappe Complex. Later ∼550-480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings resulted in the evolution

  8. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution

    NASA Astrophysics Data System (ADS)

    Fritz, H.; Abdelsalam, M.; Ali, K. A.; Bingen, B.; Collins, A. S.; Fowler, A. R.; Ghebreab, W.; Hauzenberger, C. A.; Johnson, P. R.; Kusky, T. M.; Macey, P.; Muhongo, S.; Stern, R. J.; Viola, G.

    2013-10-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world´s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara-Congo-Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian-Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite-Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650-620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo-Tanzania-Bangweulu Cratons and the Zimbabwe-Kalahari Craton. They closed during the ∼600-500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600-550 Ma extension is recorded in the Arabian-Nubian Shield and the Eastern Granulite-Cabo Delgado Nappe Complex. Later ∼550-480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings resulted in the evolution of

  9. Detrital Record of Phanerozoic Tectonics in Iran: Evidence From U-Pb Zircon Geochronology

    NASA Astrophysics Data System (ADS)

    Horton, B. K.; Gillis, R. J.; Stockli, D. F.; Hassanzadeh, J.; Axen, G. J.; Grove, M.

    2004-12-01

    Ion-microprobe U-Pb ages of 91 detrital zircon grains supplement ongoing investigations of the tectonic history of Iran, a critical region bridging the gap between the Alpine and Himalayan orogenic belts. These data improve understanding of the distribution of continental blocks during a complex history of Late Proterozoic (Pan-African) crustal growth, Paleozoic passive-margin sedimentation, early Mesozoic collision with Eurasia, and Cenozoic collision with Arabia. U-Pb analyses of detrital zircon grains from four sandstone samples (two Lower Cambrian, one uppermost Triassic-Lower Jurassic, one Neogene) collected from the Alborz mountains of northern Iran reveal a spectrum of ages ranging from 50 to 2900 Ma. Most analyses yield concordant to moderately discordant ages. The Lower Cambrian Lalun and Barut sandstones yield age distribution peaks at approximately 550-650, 1000, and 2500 Ma, consistent with a Gondwanan source area presently to the south and west in parts of Iran and the Arabian-Nubian shield (Saudi Arabia and northwestern Africa). The uppermost Triassic-Lower Jurassic Shemshak Formation exhibits a broad range of U-Pb ages, including peaks of approximately 200-260, 330, 430, 600, and 1900 Ma, requiring a Eurasian source area presently to the north and east in the Turan plate (Turkmenistan and southwestern Asia). Neogene strata display both the youngest and oldest ages (approximately 50 and 2900 Ma) of any samples, a result of substantial sedimentary recycling of older Phanerozoic cover rocks. Because the youngest zircon ages for three of the four samples are indistinguishable from their stratigraphic (depositional) ages, these data suggest rapid exhumation and help constrain the termination age of Late Proterozoic-Early Cambrian (Pan-African) orogenesis and the timing of the Iran-Eurasia collision.

  10. Early adolescence behavior problems and timing of poverty during childhood: A comparison of lifecourse models.

    PubMed

    Mazza, Julia Rachel S E; Lambert, Jean; Zunzunegui, Maria Victoria; Tremblay, Richard E; Boivin, Michel; Côté, Sylvana M

    2017-03-01

    Poverty is a well-established risk factor for the development of behavior problems, yet little is known about how timing of exposure to childhood poverty relates to behavior problems in early adolescence. To examine the differential effects of the timing of poverty between birth and late childhood on behavior problems in early adolescence by modeling lifecourse models, corresponding to sensitive periods, accumulation of risk and social mobility models. We used the Quebec Longitudinal Study of Child Development (N = 2120). Poverty was defined as living below the low-income thresholds defined by Statistics Canada and grouped into three time periods: between ages 0-3 years, 5-7 years, and 8-12 years. Main outcomes were teacher's report of hyperactivity, opposition and physical aggression at age 13 years. Structured linear regression analyses were conducted to estimate the contribution of poverty during the three selected time periods to behavior problems. Partial F-tests were used to compare nested lifecourse models to a full saturated model (all poverty main effects and possible interactions). Families who experienced poverty at all time periods were 9.3% of the original sample. Those who were poor at least one time period were 39.2%. The accumulation of risk model was the best fitting model for hyperactivity and opposition. The risk for physical aggression problems was associated only to poverty between 0 and 3 years supporting the sensitive period. Early and prolonged exposure to childhood poverty predicted higher levels of behavior problems in early adolescence. Antipoverty policies targeting the first years of life and long term support to pregnant women living in poverty are likely to reduce behavior problems in early adolescence. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. The Sanrafaelic remagnetization revisited: Magnetic properties and magnetofabrics of Cambrian-Ordovician carbonates of the Eastern Precordillera of San Juan, Argentina

    NASA Astrophysics Data System (ADS)

    Fazzito, Sabrina Y.; Rapalini, Augusto E.; Poiré, Daniel G.

    2017-11-01

    Systematic rock-magnetic and magnetofabric studies were carried out on samples from twenty-three palaeomagnetic sites distributed on the La Laja, Zonda, La Flecha, La Silla and San Juan Formations, which constitute a thick middle Cambrian to early Ordovician carbonate sequence exposed in the Eastern Precordillera of Argentina. Previous palaeomagnetic studies on these rocks showed that this succession is characterized by a recent full overprint in the lower levels and a post-tectonic Permian remagnetization associated to the widespread Sanrafaelic event in the upper part. Our investigation revealed that the fluctuations of the magnetic properties are stratigraphically (lithologically) controlled. Anisotropy of magnetic and anhysteretic susceptibility measurements defined consistent fabrics along the entire section that switch progressively from "inverse", at the bottom, to "normal", at the top, with "intermediate" fabrics occurring mainly at medium levels. Degree of dolomitization significantly affects many rock-magnetic parameters, but appears unrelated to the presence of the Permian remagnetization, which is determined to reside in magnetite despite the complex magnetic mineralogy shown by the studied carbonates. Hysteresis cycles of rocks affected by the Sanrafaelic remagnetization are governed by ferromagnetic fractions showing a clear difference respect to those not affected and characterized by the dominance of paramagnetic or diamagnetic signals. The magnetic fabrics and mineralogical characterization rule out a thermoviscous origin and suggest a chemical remagnetization originated in the authigenic formation of magnetite for the Sanrafaelic overprint. X-ray diffraction analyses indicate that clay minerals are virtually absent in the whole succession with no traces of illite in any sample, discarding burial diagenesis of clay minerals for the origin of the remagnetization. Lack of late Palaeozoic magmatic rocks near the study area difficults correlation of

  12. Early years neurosurgical training in the era of the European Working Time Directive.

    PubMed

    Kirkman, Matthew A; Watkins, Laurence D; Kitchen, Neil D; Sethi, Huma

    2013-10-01

    The past decade has seen significant changes to the face of neurosurgical training in the United Kingdom, driven in part by an increasing focus on patient safety and the introduction of Modernising Medical Careers and the European Working Time Directive (EWTD). Recent reforms to neurosurgical training over the past few years have resulted in creation of an 8-year 'run-through' training programme. In this programme, early years (ST1 and ST2) trainees often lack dedicated time for elective theatre lists and outpatient clinics. Further, any time spent in theatre and clinics is often with different teams. Here we describe a training model for early years trainees at the National Hospital for Neurology and Neurosurgery, who are given the responsibilities traditionally associated with a more senior trainee including dedicated weekly theatre and clinic time under the supervision of a single consultant, in addition to out of hours experience. The advantages and considerations for implementing this model are discussed, including the benefit of guidance under a single consultant in the early stages of training, along with key educational concepts necessary for understanding its utility. We feel that this is an effective model for junior neurosurgical training in the EWTD era, expediting the trainee's development of key technical and non-technical skills, with potentially significant rewards for patient, trainee and trainer. National implementation of this model should be considered.

  13. Early diagnosis and multidisciplinary care reduce the hospitalization time and duration of tube feeding and prevent early obesity in PWS infants.

    PubMed

    Bacheré, N; Diene, G; Delagnes, V; Molinas, C; Moulin, P; Tauber, M

    2008-01-01

    To describe and evaluate the impact of very early diagnosis and multidisciplinary care on the evolution and care of infants presenting with Prader-Willi syndrome (PWS). 19 infants diagnosed with PWS before the second month of life were followed by a multidisciplinary team. Median age at the time of analysis was 3.1 years [range 0.4-6.5]. The data were compared with data collected in 1997 from 113 questionnaires filled out by members of the French PWS Association. The patients from this latter data set were 12.0 years [range 4 months to 41 years] at the time of analysis, with a median age of 36 months at diagnosis. The duration of their hospitalization time was significantly reduced from 30.0 [range 0-670] to 21 [range 0-90] days (p = 0.043). The duration of gastric tube feeding was significantly reduced from 30.5 [range 0-427] to 15 [range 0-60] days (p = 0.017). Growth hormone treatment was started at a mean age of 1.9 +/- 0.5 years in 10 infants and L-thyroxine in 6 infants. Only 1 infant became obese at 2.5 years. Early diagnosis combined with multidisciplinary care decreases the hospitalization time, duration of gastric tube feeding and prevents early obesity in PWS infants. (c) 2007 S. Karger AG, Basel.

  14. Standardized Symptom Measurement of Individuals with Early Lyme Disease Over Time.

    PubMed

    Bechtold, Kathleen T; Rebman, Alison W; Crowder, Lauren A; Johnson-Greene, Doug; Aucott, John N

    2017-03-01

    Understanding the Lyme disease (LD) literature is challenging given the lack of consistent methodology and standardized measurement of symptoms and the impact on functioning. This prospective study incorporates well-validated measures to capture the symptom picture of individuals with early LD from time of diagnosis through 6-months post-treatment. One hundred seven patients with confirmed early LD and 26 healthy controls were evaluated using standardized instruments for pain, fatigue, depressive symptoms, functional impact, and cognitive functioning. Prior to antibiotic treatment, patients experience notable symptoms of fatigue and pain statistically higher than controls. After treatment, there are no group differences, suggesting that symptoms resolve and that there are no residual cognitive impairments at the level of group analysis. However, using subgroup analyses, some individuals experience persistent symptoms that lead to functional decline and these individuals can be identified immediately post-completion of standard antibiotic treatment using well-validated symptom measures. Overall, the findings suggest that ideally-treated early LD patients recover well and experience symptom resolution over time, though a small subgroup continue to suffer with symptoms that lead to functional decline. The authors discuss use of standardized instruments for identification of individuals who warrant further clinical follow-up. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  15. Investigation of Times of Minima of Selected Early-Type Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Mayer, Pavel; Wolf, Marek; Niarchos, P. G.; Gazeas, K. D.; Manimanis, V. N.; Chochol, Drahomír

    2006-08-01

    New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus.

  16. Early Life Factors and Adult Leisure Time Physical Inactivity Stability and Change.

    PubMed

    Pinto Pereira, Snehal M; Li, Leah; Power, Chris

    2015-09-01

    Physical inactivity has a high prevalence and associated disease burden. A better understanding of influences on sustaining and changing inactive lifestyles is needed. We aimed to establish whether leisure time inactivity was stable in midadulthood and whether early life factors were associated with inactivity patterns. In the 1958 British birth cohort (n = 12,271), leisure time inactivity (frequency, less than once a week) assessed at 33 and 50 yr was categorized as "never inactive," "persistently inactive," "deteriorating," or "improving." Early life factors (birth to 16 yr) were categorized into three (physical, social, and behavioral) domains. Using multinomial logistic regression, we assessed associations with inactivity persistence and change of factors within each early life domain and the three domains combined with and without adjustment for adult factors. Inactivity prevalence was similar at 33 and 50 yr (approximately 31%), but 17% deteriorated and 18% improved with age. In models adjusted for all domains simultaneously, factors associated with inactivity persistence versus never inactive were prepubertal stature (8% lower risk/height SD), poor hand control/coordination (17% higher risk/increase on four-point scale), cognition (16% lower/SD in ability) (physical); parental divorce (25% higher), class at birth (7% higher/reduction on four-point scale), minimal parental education (16% higher), household amenities (2% higher/increase in 19-point score (high = poor)) (social); and inactivity (22% higher/reduction in activity on four-point scale), low sports aptitude (47% higher), smoking (30% higher) (behavioral). All except stature, parental education, sports aptitude, and smoking were associated also with inactivity deterioration. Poor hand control/coordination was the only factor associated with improved status (13% lower/increase on four-point scale) versus persistently inactive. Adult leisure time inactivity is moderately stable. Early life factors are

  17. The geology of a part of Acadia and the nature of the Acadian orogeny across Central and Eastern Maine

    USGS Publications Warehouse

    Tucker, R.D.; Osberg, P.H.; Berry, H.N.

    2001-01-01

    The zone of Acadian collision between the Medial New England and Composite Avalon terranes is well preserved in Maine. A transect from northwest (Rome) to southeast (Camden) crosses the eastern part of Medial New England comprising the Central Maine basin, Liberty-Orrington thrust sheet, and Fredericton trough, and the western part of Composite Avalon, including the Graham Lake, Clarry Hill, and Clam Cove thrust sheets. U-Pb geochronology of events before, during, and after the Acadian orogeny helps elucidate the nature and distribution of tectonostrati& graphic belts in this zone and the timing of some Acadian events in the Northern Appalachians. The Central Maine basin consists of sedimentary and volcanic rocks of Middle Ordovician (???470 to ???460 Ma) age overlain with probable conformity by latest Ordovician(?) through earliest Devonian marine rift and flysch sedimentary rocks; these are intruded by weakly to undeformed plutonic rocks of Early and Middle Devonian age (???399??378 Ma). The Fredericton trough consists of Early Silurian gray pelite and sandstone to earliest Late Silurian calcareous turbidite, deformed and variably metamorphosed prior to the emplacement of Late Silurian (???422 Ma) and Early to Late Devonian (???418 to ???368 Ma) plutons. The Liberty-Orrington thrust sheet consists of Cambrian(?)-Ordovician (>???474 to ???469 Ma and younger) clastic sedimentary and volcanic rocks intruded by highly deformed Late Silurian (???424 to ???422 Ma) and Devonian (???418 to ???389 Ma) plutons, possibly metamorphosed in Late Silurian time (prior to ???417 Ma), and metamorphosed to amphibolite facies in Early to Middle Devonian time (???400 to ???381 Ma). The Graham Lake thrust sheet contains possible Precambrian rocks, Cambrian sedimentary rocks with a volcanic unit dated at ???503 Ma, and Ordovician rocks with possible Caradocian Old World fossils, metamor& phosed and deformed in Silurian time and intruded by mildly to undeformed Late Silurian (???421 Ma

  18. Metamorphosis Is Ancestral for Crown Euarthropods, and Evolved in the Cambrian or Earlier.

    PubMed

    Wolfe, Joanna M

    2017-09-01

    Macroevolutionary developmental biology employs fossilized ontogenetic data and phylogenetic comparative methods to probe the evolution of development at ancient nodes. Despite the prevalence of ecologically differentiated larval forms in marine invertebrates, it has been frequently presumed that the ancestors of arthropods were direct developers, and that metamorphosis may not have evolved until the Ordovician or later. Using fossils and new dated phylogenies, I infer that metamorphosis was likely ancestral for crown arthropods, contradicting this assumption. Based on a published morphological dataset encompassing 217 exceptionally preserved fossil and 96 extant taxa, fossils were directly incorporated into both the topology and age estimates, as in "tip dating" analyses. Using data from post-embryonic fossils representing 25 species throughout stem and crown arthropod lineages (as well as most of the 96 extant taxa), characters for metamorphosis were assigned based on inferred ecological changes in development (e.g., changes in habitat and adaptive landscape). Under all phylogenetic hypotheses, metamorphosis was supported as most likely ancestral to both ecdysozoans and euarthropods. Care must be taken to account for potential drastic post-embryonic morphological changes in evolutionary analyses. Many stem group euarthrpods may have had ecologically differentiated larval stages that did not preserve in the fossil record. Moreover, a complex life cycle and planktonic ecology may have evolved in the Ediacaran or earlier, and may have typified the pre-Cambrian explosion "wormworld" prior to the origin of crown group euarthropods. © The Author 2017. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

  19. Changes in chloride concentration in water from municipal wells that tap aquifers in rocks of Cambrian and Ordovician age in northeastern Illinois, 1915-84

    USGS Publications Warehouse

    Balding, G.O.

    1991-01-01

    During the past few decades, several municipalities in northeastern Illinois have noted increases in the salinity of water from wells that tap aquifers in rocks of Cambrian and Ordovician age. The municipalities have discontinued the use of, or sealed-off sections of, those wells. The aquifers involved include the Ancell, the Ironton-Galesville, and the Elmhurst-Mt. Simon. To define the location, magnitude, and possible causes for the salinity increases in the six northeastern counties of Illinois, 17 municipal wells and 1 deep test well were selected on the basis of their proximity to major pumping centers, the availability of water-quality data, and their documented maintenance history. Well depths ranged from about 960 to 3,475 feet. One well was finished in the middle confining unit, 2 wells were finished in the Ironton-Galesville aquifer, 4 wells were finished in the Eau Claire confining unit, and 10 wells were finished in the Elmhurst-Mt. Simon aquifer. The deep test well was finished below the Elmhurst-Mt. Simon aquifer in Precambrian-age rock. Chloride concentrations in the municipal wells ranged from less than 5 to greater than 600 milligrams per liter; in the deep test well, they ranged from 13 t o 37,000 milligrams per liter. Some changes in the chloride concentration in water from the studied municipal wells can be related to physical changes to the wells, including the partial filling in of a well, bridging within a well, the cleaning out of a well, or the deepening of a well. Some changes in chloride concentration are not related to physical changes but may be caused by increased pumpage; changes in pumping rate, frequency, or duration; cessation of pumping; improper abandonment of wells; and the upconing of highly mineralized water. The data base was inadequate for a quantitative study of the changes in chloride concentration in water from individual aquifers in rocks of Cambrian and Ordovician age.

  20. Towards a High-resolution Time Scale for the Early Devonian

    NASA Astrophysics Data System (ADS)

    Dekkers, M. J.; da Silva, A. C.

    2017-12-01

    High-resolution time scales are crucial to understand Earth's history in detail. The construction of a robust geological time scale, however, inevitably becomes increasingly harder further back in time. Uncertainties associated with anchor radiometric ages increase in size, not speaking of the mere presence of suitable datable strata. However, durations of stages can be tightly constrained by making use of cyclic expressions in sediments, an approach that revolutionized the Cenozoic time scale. When precisely determined durations are stitched together, ultimately, a very precise time scale is the result. For the Mesozoic and Paleozoic an astronomical solution as a tuning target is not available but the dominant periods of eccentricity, obliquity and precession are reasonably well constrained for the entire Phanerozoic which enables their detection by means of spectral analysis. Eccentricity is time-invariant and is used as the prime building block. Here we focus on the Early Devonian, on its lowermost three stages: the Lochkovian, Pragian and Emsian. The uncertainties on the Devonian stage boundaries are currently in the order of several millions of years. The preservation of climatic cycles in diagenetically or even anchimetamorphically affected successions, however, is essential. The fit of spectral peak ratios with those calculated for orbital cycles, is classically used as a strong argument for a preserved climatic signal. Here we use primarily the low field magnetic susceptibility (MS) as proxy parameter, supported by gamma-ray spectrometry to test for consistency. Continuous Wavelet Transform, Evolutive Harmonic Analysis, Multitaper Method, and Average Spectral Misfit are used to reach an optimal astronomical interpretation. We report on classic Early Devonian sections from the Czech Republic: the Pozar-CS (Lochkovian and Pragian), Pod Barrandovem (Pragian and Lower Emsian), and Zlichov (Middle-Upper Emsian). Also a Middle-Upper Emsian section from the US

  1. Timing of First Antenatal Care (ANC) and Inequalities in Early Initiation of ANC in Nepal.

    PubMed

    Paudel, Yuba Raj; Jha, Trishna; Mehata, Suresh

    2017-01-01

    The provision and uptake of quality and timely antenatal care (ANC) is an essential element of efforts to improve health outcomes for women and newborn babies. Antenatal consultations assist in early identification and treatment of complications during pregnancy. This study aimed to provide an information on distribution and inequalities in early initiation of ANC in Nepal. The distribution and inequalities in the early initiation of ANC were examined using Nepal Demographic and Health Surveys 2011. Bivariate and multivariate logistic regression was used to assess inequalities. Overall, 70% of the women had started their first ANC at 4 month or earlier. Among participants who had never attended school, just more than half (52%) received first ANC at 4 months or earlier, while majority of participants (97%) who had received higher education received first ANC at recommended time. Similarly, 89% of those from richest quintile and 48% of those from poorest quintile received first ANC at recommended time. In adjusted analysis, women from richest wealth quintile were significantly more likely to initiate ANC early (AOR: 3.74, 95% CI: 2.31-6.05) compared to the poorest. Similarly, women with higher level education were significantly more likely (AOR: 11.40, 95% CI: 5.05-25.73) to initiate ANC early compared to women who had never attended school. A significantly lower odds of early ANC take up was observed among madhesi other caste (AOR: 0.56, 95% CI: 0.35-0.90) compared to brahmin/chhetri women. Women whose pregnancy was unwanted were significantly less likely to attend first ANC at 4 months or early (AOR: 0.73, 95% CI: 0.58-0.93) in comparison to women whose pregnancy was wanted. The differences in the recommended timing of initiation of ANC were evident among women with different educational, economic levels, and caste/ethnic groups. Rural women were less likely to have checkups as per guidelines. The findings suggest to a need of interventions to raise female

  2. Boundary|Time|Surface: Art and Geology Meet in Gros Morne National Park, NL, Canada

    NASA Astrophysics Data System (ADS)

    Lancaster, Sydney; Waldron, John

    2015-04-01

    Environmental Art works range in scope from major permanent interventions in the landscape to less intrusive, more ephemeral site-specific installations constructed of materials from the local environment. Despite this range of intervention, however, these works all share in a tradition of art making that situates the artwork in direct response to the surrounding landscape. Andy Goldsworthy and Richard Long, for example, both favour methods that combine elements of both sculpture and performance in the creation of non-permanent interventions in the landscape, and both rely upon photographic, text-based, or video documentation as the only lasting indication of the works' existence. Similarly, Earth Scientists are responsible for interventions in the landscape, both physical and conceptual. For example, in Earth science, the periods of the geologic timescale - Cambrian, Ordovician, Silurian, etc. - were established by 19th century pioneers of geology at a time when they were believed to represent natural chapters in Earth history. Since the mid-20th century, stratigraphers have attempted to resolve ambiguities in the original definitions by defining stratotypes: sections of continuously deposited strata where a single horizon is chosen as a boundary. One such international stratotype, marking the Cambrian-Ordovician boundary, is defined at Green Point in Gros Morne National Park, Newfoundland. Boundary|Time|Surface was an ephemeral sculptural installation work constructed in June 2014. The main installation work was a fence of 52 vertical driftwood poles, 2-3 m tall, positioned precisely along the boundary stratotype horizon at Green Point in Newfoundland. The fence extended across a 150 m wave-cut platform from sea cliffs to the low-water mark, separating Ordovician from Cambrian strata. The installation was constructed by hand (with volunteer assistance) on June 22, as the wave-cut platform was exposed by the falling tide. During the remainder of the tidal cycle

  3. New evidence on the anatomy and phylogeny of the earliest vertebrates.

    PubMed Central

    Xian-guang, Hou; Aldridge, Richard J; Siveter, David J; Siveter, Derek J; Xiang-hong, Feng

    2002-01-01

    We report the discovery of a new agnathan specimen from the Lower Cambrian Chengjiang Lagerstätte of China and thereby provide new evidence on the myomeres (V-shaped), the branchial apparatus (gill filaments and arches), the dorsal fin and the gonads (24-26) of the earliest vertebrates. The new specimen and the co-occurring Myllokunmingia fengjiaoa and Haikouichthys ercaicunensis represent a single species, which is a primitive member of the crown group craniates (vertebrates) and post-dates the origin of the myxinoids (hagfish). The origin of the vertebrate clade is at least as old as Early Cambrian. PMID:12350247

  4. Listening to Students: Studying for a Part-Time Degree in Early Childhood Studies.

    ERIC Educational Resources Information Center

    Burn, Elizabeth

    For this study, 12 part-time students in an early childhood studies program were interviewed and videotaped concerning their personal stories as students. Initial analysis of their responses revealed main themes: (1) economic barriers to full-time degree study; (2) domestic responsibilities/gender issues (for example, the stress of juggling…

  5. Early tectonic evolution of the Thomson Orogen in Queensland inferred from constrained magnetic and gravity data

    NASA Astrophysics Data System (ADS)

    Spampinato, Giovanni P. T.; Betts, Peter G.; Ailleres, Laurent; Armit, Robin J.

    2015-05-01

    The crustal architecture as well as the kinematic evolution of the Thomson Orogen in Queensland is poorly resolved because the region is concealed under thick Phanerozoic sedimentary basins and the basement geology is known from limited drill holes. Combined potential field and seismic interpretation indicates that the Thomson Orogen is characterized by prominent regional NE- and NW-trending structural grain defined by long wavelength and low amplitude geophysical anomalies. The 'smooth' magnetic signature is interpreted to reflect deeply buried source bodies in the mid- to lower crust. Short wavelength positive magnetic features that correlate with negative gravity anomalies are interpreted to represent shallower granitic intrusions. They appear to be focused along major fault zones that might have controlled the locus for magmatism. The eastern Thomson Orogen is characterized by a prominent NE structural grain and orthogonal faults and fold interference patterns resulting in a series of troughs and highs. The western Thomson Orogen consists of a series of NW-trending structures interpreted to reflect reverse faults. Sedimentation and basin development are interpreted to have initiated in the Neoproterozoic to Early Cambrian during E-W- to ENE-WSW extension, possibly related to the Rodinia break-up. This extensional event was followed by Late Cambrian shortening recorded in the Maneroo Platform and the Diamantina River Domain which possibly correlates with the Delamerian Orogeny. Renewed deposition and volcanism occurred during the Ordovician and may have continued until Late Silurian, resulting in thinned Proterozoic basement crust and extensive basin systems that formed in a distal continental back-arc environment. Our interpretation places the Thomson Orogen to the west of the Neoproterozoic passive margin preserved in the Anakie Inlier. The region is likely to represent the internal extensional architecture during the Rodinia break-up that has been

  6. Planetary biology and microbial ecology. Biochemistry of carbon and early life

    NASA Technical Reports Server (NTRS)

    Margulis, L. (Editor); Nealson, K. H. (Editor); Taylor, I. (Editor)

    1983-01-01

    Experiments made with cyanobacteria, phototrophic bacteria, and methanogenic bacteria are detailed. Significant carbon isotope fractionation data is included. Taken from well documented extant microbial communities, this data provides a basis of comparison for isotope fractionation values measured in Archean and Proterozoic (preCambrian) rocks. Media, methods, and techniques used to acquire data are also described.

  7. Evidence for local and global redox conditions at an Early Ordovician (Tremadocian) mass extinction

    NASA Astrophysics Data System (ADS)

    Edwards, Cole T.; Fike, David A.; Saltzman, Matthew R.; Lu, Wanyi; Lu, Zunli

    2018-01-01

    Profound changes in environmental conditions, particularly atmospheric oxygen levels, are thought to be important drivers of several major biotic events (e.g. mass extinctions and diversifications). The early Paleozoic represents a key interval in the oxygenation of the ocean-atmosphere system and evolution of the biosphere. Global proxies (e.g. carbon (δ13C) and sulfur (δ34S) isotopes) are used to diagnose potential changes in oxygenation and infer causes of environmental change and biotic turnover. The Cambrian-Ordovician contains several trilobite extinctions (some are apparently local, but others are globally correlative) that are attributed to anoxia based on coeval positive δ13C and δ34S excursions. These extinction and excursion events have yet to be coupled with more recently developed proxies thought to be more reflective of local redox conditions in the water column (e.g. I/Ca) to confirm whether these extinctions were associated with oxygen crises over a regional or global scale. Here we examine an Early Ordovician (Tremadocian Stage) extinction event previously interpreted to reflect a continuation of recurrent early Paleozoic anoxic events that expanded into nearshore environments. δ13C, δ34S, and I/Ca trends were measured from three sections in the Great Basin region to test whether I/Ca trends support the notion that anoxia was locally present in the water column along the Laurentian margin. Evidence for anoxia is based on coincident, but not always synchronous, positive δ13C and δ34S excursions (mainly from carbonate-associated sulfate and less so from pyrite data), a 30% extinction of standing generic diversity, and near-zero I/Ca values. Although evidence for local water column anoxia from the I/Ca proxy broadly agrees with intervals of global anoxia inferred from δ13C and δ34S trends, a more complex picture is evident where spatially and temporally variable local trends are superimposed on time-averaged global trends. Stratigraphic

  8. Early, on-time, and late behavioural autonomy in adolescence: psychosocial correlates in young and middle adulthood.

    PubMed

    Pavlova, Maria K; Haase, Claudia M; Silbereisen, Rainer K

    2011-04-01

    Drawing on two nationally representative German studies (N(1) = 1744, N(2) = 759), we examined correlates of early, on-time, and late curfew autonomy, a retrospective indicator of behavioural autonomy, in young and middle adulthood (19-37 years of age). Adjustment in four domains was considered: educational attainment, externalizing problem behaviour, subjective well-being, and interpersonal relationships. The early group showed lower adjustment in multiple domains across young and middle adulthood. The late group reported a mixed pattern of adjustment at younger ages (lower externalizing problems, but lower positive affect, lower importance of peers, and lower likelihood to have a partner) and positive adjustment in all domains at older ages. Timing effects were controlled for sociodemographic characteristics and retrospective measures of early adversities, pubertal timing, disclosure to parents, and peer group affiliation in adolescence. Findings show that late behavioural autonomy in its correlates is not simply the opposite of early behavioural autonomy. Copyright © 2010 The Association for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

  9. The origin of increased salinity in the Cambrian-Vendian aquifer system on the Kopli Peninsula, northern Estonia

    NASA Astrophysics Data System (ADS)

    Karro, Enn; Marandi, Andres; Vaikmäe, Rein

    Monitoring of the confined Cambrian-Vendian aquifer system utilised for industrial water supply at Kopli Peninsula in Tallinn over 24 years reveals remarkable changes in chemical composition of groundwater. A relatively fast 1.5 to 3.0-fold increase in TDS and in concentrations of major ions in ed groundwater is the consequence of heavy pumping. The main sources of dissolved load in Cambrian-Vendian groundwater are the leaching of host rock and the other geochemical processes that occur in the saturated zone. Underlying crystalline basement, which comprises saline groundwater in its upper weathered and fissured portion, and which is hydraulically connected with the overlying Cambrian-Vendian aquifer system, is the second important source of ions. The fractured basement and its clayey weathering crust host the Ca-Cl type groundwater, which is characterised by high TDS values (2-20 g/L). Intensive water ion accelerates the exchange of groundwaters and increases the area of influence of pumping. Chemical and isotopic studies of groundwater indicate an increasing contribution of old brackish water from the crystalline basement and rule out the potential implication of an intrusion of seawater into aquifer. L'origine de la salinité croissante dans le système aquifère du Cambrien-Vendien dans la péninsule de Kopli, nord de l'Estonie Le suivi à long terme du système aquifère captif du Cambrien-Vendien utilisé pour l'approvisionnement d'eaux industrielles dans la Péninsule de Kopli, nord de l'Estonie, révèle de remarquables changements dans la composition chimique des eaux souterraines. Une augmentation de facteur 1.5 à 3 de la TDS et des concentrations en ions majeurs dans l'eau souterraine est la conséquence de pompages intensifs. Les sources principales des charges dissoutes dans les eaux de l'aquifère du Cambrien-Vendien sont le lessivage des roches et d'autres phénomènes géochimiques ayant lieu dans la zone saturée. Le soubassement rocheux cristallin

  10. Comparing physical activity and sedentary time among overweight and nonoverweight preschoolers enrolled in early learning programs: a cross-sectional study.

    PubMed

    Tucker, Patricia; Maltby, Alana M; Burke, Shauna M; Vanderloo, Leigh M; Irwin, Jennifer D

    2016-09-01

    Establishing appropriate physical activity and sedentary behaviours during early childhood is important to ensure children accrue the many associated health benefits. While physical activity levels have been reported as low within early learning programs, little research has explored the physical activity and sedentary time of Canadian preschoolers classified as overweight within these facilities. The purpose of this study was to compare objectively measured physical activity and sedentary time among preschoolers classified as overweight and nonoverweight in early learning programs. Direct assessment of physical activity and sedentary time of 216 preschool-aged children was collected via Actical accelerometers during early learning hours, while body mass index percentile was calculated based on preschoolers' objectively measured height and weight. Results of three 3-way ANOVAs suggest that rates of moderate to vigorous physical activity, total physical activity, and sedentary time (p > 0.05) did not significantly differ based on weight status, sex, and type of early learning facility. This study is one of few that has examined differences in overweight and nonoverweight preschoolers' sedentary time, and adds to the limited research exploring physical activity levels among overweight and nonoverweight preschoolers during early learning hours. Given the high rates of sedentary time reported, programming within early learning facilities is necessary to support preschoolers, regardless of weight status, to achieve increased physical activity levels and decreased sedentary time.

  11. The Developmental Pathway From Pubertal Timing to Delinquency and Sexual Activity From Early to Late Adolescence

    PubMed Central

    Negriff, Sonya; Elizabeth, J. Susman; Trickett, Penelope K.

    2013-01-01

    There is strong evidence that early pubertal timing is associated with adolescent problem behaviors. However, there has been limited investigation of the mechanisms or developmental relationships. The present study examined longitudinal models incorporating pubertal timing, delinquency, and sexual activity in a sample of 454 adolescents (9–13 years old at enrollment; 47% females). Participants were seen for three assessments approximately 1 year apart. Characteristics of friendship networks (older friends, male friends, older male friends) were examined as mediators. Structural equation modeling was used to test these associations as well as temporal relationships between sexual activity and delinquency. Results showed that early pubertal timing at Time 1 was related to more sexual activity at Time 2, which was related to higher delinquency at Time 3, a trend mediation effect. None of the friendship variables mediated these associations. Gender or maltreatment status did not moderate the meditational pathways. The results also supported the temporal sequence of sexual activity preceding increases in delinquency. These findings reveal that early maturing adolescents may actively seek out opportunities to engage in sexual activity which appears to be risk for subsequent delinquency. PMID:21191640

  12. The developmental pathway from pubertal timing to delinquency and sexual activity from early to late adolescence.

    PubMed

    Negriff, Sonya; Susman, Elizabeth J; Trickett, Penelope K

    2011-10-01

    There is strong evidence that early pubertal timing is associated with adolescent problem behaviors. However, there has been limited investigation of the mechanisms or developmental relationships. The present study examined longitudinal models incorporating pubertal timing, delinquency, and sexual activity in a sample of 454 adolescents (9-13 years old at enrollment; 47% females). Participants were seen for three assessments approximately 1 year apart. Characteristics of friendship networks (older friends, male friends, older male friends) were examined as mediators. Structural equation modeling was used to test these associations as well as temporal relationships between sexual activity and delinquency. Results showed that early pubertal timing at Time 1 was related to more sexual activity at Time 2, which was related to higher delinquency at Time 3, a trend mediation effect. None of the friendship variables mediated these associations. Gender or maltreatment status did not moderate the meditational pathways. The results also supported the temporal sequence of sexual activity preceding increases in delinquency. These findings reveal that early maturing adolescents may actively seek out opportunities to engage in sexual activity which appears to be risk for subsequent delinquency.

  13. Sands of West Gondwana: An archive of secular magmatism and plate interactions — A case study from the Cambro-Ordovician section of the Tassili Ouan Ahaggar (Algerian Sahara) using U-Pb-LA-ICP-MS detrital zircon ages

    NASA Astrophysics Data System (ADS)

    Linnemann, Ulf; Ouzegane, Khadidja; Drareni, Amar; Hofmann, Mandy; Becker, Sindy; Gärtner, Andreas; Sagawe, Anja

    2011-04-01

    Enormous masses of highly mature quartz sands were deposited in Western Gondwana during the Cambrian-Ordovician time, and provide a wide range of information concerning magmatic events through time, provenance, paleoclimate, and basin history. We present a provenance study based on 630 U-Pb (LA-ICP-MS) ages of detrital zircon from the latest Cambrian to Ordovician siliciclastic rocks of the Tassili Ouan Ahaggar basin situated in the Algerian Sahara. Most authors suggest local sources only for the sandstones. Instead, we demonstrate that the detritus is derived from different cratons and terranes which contributed to the deposition of a Cambrian-Ordovician overstep sequence covering western and northern Africa. Most zircon ages (61.0%) fall in the range of ~ 540 to 740 Ma and are interpreted to have been derived from Pan-African orogenic belts such as the Trans-Saharan Belt of NW Africa and previously from the Brazila belt of South America. Other potential sources for this zircon population are terranes of Cadomian affinity situated marginal to West Africa. The second-largest zircon population (20.2%) is 2.0 to 2.2 Ga, and is attributed to sources in the West African craton, such as the Birimian basement and the Eburnean orogenic belt, with possible partial input from the Amazonian craton. A zircon population of 7.1% yields Mesoproterozoic and early Paleoproterozoic ages in the range of ~ 1.3 to ~ 1.8 Ga and was probably derived from source rocks outside of the West African basement, the Tuareg shield and other adjoining areas. The Amazonian craton is a potential source region. A population of 6.7% of all zircon ages scatter from ~ 750 Ma to ~ 980 Ma and may reflect input from latest stages of the formation of Rodinia and its subsequent dispersal. A smaller population (3.2%) of zircon ages lie between ~ 2.3 and 2.65 Ga, and may be derived from late Paleoproterozoic to early Archaean rocks from the West African craton and possibly from Amazonia. Less than 1% of all

  14. Structure and function of a compound eye, more than half a billion years old.

    PubMed

    Schoenemann, Brigitte; Pärnaste, Helje; Clarkson, Euan N K

    2017-12-19

    Until now, the fossil record has not been capable of revealing any details of the mechanisms of complex vision at the beginning of metazoan evolution. Here, we describe functional units, at a cellular level, of a compound eye from the base of the Cambrian, more than half a billion years old. Remains of early Cambrian arthropods showed the external lattices of enormous compound eyes, but not the internal structures or anything about how those compound eyes may have functioned. In a phosphatized trilobite eye from the lower Cambrian of the Baltic, we found lithified remnants of cellular systems, typical of a modern focal apposition eye, similar to those of a bee or dragonfly. This shows that sophisticated eyes already existed at the beginning of the fossil record of higher organisms, while the differences between the ancient system and the internal structures of a modern apposition compound eye open important insights into the evolution of vision. Copyright © 2017 the Author(s). Published by PNAS.

  15. Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the northern Great Xing'an Range, NE China

    NASA Astrophysics Data System (ADS)

    Feng, Zhiqiang; Liu, Yongjiang; Li, Yanrong; Li, Weimin; Wen, Quanbo; Liu, Binqiang; Zhou, Jianping; Zhao, Yingli

    2017-08-01

    The Xinlin-Xiguitu suture zone, located in the Great Xing'an Range, NE China, in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the boundary between the Erguna and Xing'an micro-continental blocks. The exact location of the Xinlin-Xiguitu suture zone has been debated, especially, the location of the northern extension of the suture zone. In this study, based on a detailed field, geochemical, geochronological and Sr-Nd-Hf isotope study, we focus our work on the Cambrian igneous rocks in the Erguna-Xing'an block. The Xinglong granitoids, mainly include ∼520 Ma diorite, ∼470 Ma monzogranite and ∼480 Ma pyroxene diorite. The granitoids show medium to high-K calc-alkaline series characteristics with post-collision granite affinity. The circa 500 Ma granitoids have low εHf (t) values (-16.6 to +2.2) and ancient two-stage model (TDM2) ages between 1317 Ma and 2528 Ma. These results indicate the primary magmas of the Xinglong granitoids were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic ;old; crustal source with possible different degrees of addition of juvenile materials, and formed in a post-collision tectonic setting after the amalgamation of the Erguna and Xing'an blocks. Compared with the Xinglong granitoids, the Duobaoshan igneous rocks are consisted of the approximately coeval rhyolitic tuffs (491 ± 5 Ma) and ultramafic intrusions (497 ± 5 Ma) within the Duobaoshan Formation. They are generally enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), consistent with the geochemistry of igneous rocks from island arcs or active continental margins. The ultramafic rocks have high positive εHf (t) values (+1.3 to +15) and εNd (t) (+1.86 to +2.28), and relatively young two-stage model (TDM2) ages and low initial 87Sr/86Sr ratios (0.70628-0.70853), indicating the partial melting of a depleted mantle source from a subducted slab in

  16. Between Charity and Education: Orphans and Orphanages in Early Modern Times

    ERIC Educational Resources Information Center

    Jacobi, Juliane

    2009-01-01

    In early modern times orphans have been children who could not expect sufficient support from their family because of lack of at least one parent, in most cases the father. This article will clarify of whom we are talking if we talk about orphans and what have been the conditions of living in a society which was organised by a high variety of…

  17. Singular F(R) cosmology unifying early- and late-time acceleration with matter and radiation domination era

    NASA Astrophysics Data System (ADS)

    Odintsov, S. D.; Oikonomou, V. K.

    2016-06-01

    We present some cosmological models which unify the late- and early-time acceleration eras with the radiation and the matter domination era, and we realize the cosmological models by using the theoretical framework of F(R) gravity. Particularly, the first model unifies the late- and early-time acceleration with the matter domination era, and the second model unifies all the evolution eras of our Universe. The two models are described in the same way at early and late times, and only the intermediate stages of the evolution have some differences. Each cosmological model contains two Type IV singularities which are chosen to occur one at the end of the inflationary era and one at the end of the matter domination era. The cosmological models at early times are approximately identical to the R 2 inflation model, so these describe a slow-roll inflationary era which ends when the slow-roll parameters become of order one. The inflationary era is followed by the radiation era and after that the matter domination era follows, which lasts until the second Type IV singularity, and then the late-time acceleration era follows. The models have two appealing features: firstly they produce a nearly scale invariant power spectrum of primordial curvature perturbations and a scalar-to-tensor ratio which are compatible with the most recent observational data and secondly, it seems that the deceleration-acceleration transition is crucially affected by the presence of the second Type IV singularity which occurs at the end of the matter domination era. As we demonstrate, the Hubble horizon at early times shrinks, as expected for an initially accelerating Universe, then during the matter domination era, it expands and finally after the Type IV singularity, the Hubble horizon starts to shrink again, during the late-time acceleration era. Intriguingly enough, the deceleration-acceleration transition, occurs after the second Type IV singularity. In addition, we investigate which F(R) gravity

  18. The Role of Present Time Perspective in Predicting Early Adolescent Violence.

    PubMed

    Kruger, Daniel J; Carrothers, Jessica; Franzen, Susan P; Miller, Alison L; Reischl, Thomas M; Stoddard, Sarah A; Zimmerman, Marc A

    2018-06-01

    This study investigated the role of present and future time perspectives, and their relationships with subjective norms and beliefs regarding violence, in predicting violent behaviors among urban middle school students in the Midwestern United States. Although present time perspective covaried with subjective norms and beliefs, each made a unique prediction of self-reported violent behaviors. Future time perspective was not a significant predictor when accounting for these relationships. In addition, present orientation moderated the relationship between subjective norms and beliefs and rates of violent behaviors; those with higher present orientations exhibited stronger associations. We replicated this pattern of results in data from new participants in a subsequent wave of the study. Interventions that explicitly address issues related to time perspective may be effective in reducing early adolescent violence.

  19. A paired apatite and calcite clumped isotope thermometry approach to estimating Cambro-Ordovician seawater temperatures and isotopic composition

    NASA Astrophysics Data System (ADS)

    Bergmann, Kristin D.; Finnegan, Seth; Creel, Roger; Eiler, John M.; Hughes, Nigel C.; Popov, Leonid E.; Fischer, Woodward W.

    2018-03-01

    The secular increase in δ18O values of both calcitic and phosphatic marine fossils through early Phanerozoic time suggests either that (1) early Paleozoic surface temperatures were high, in excess of 40 °C (tropical MAT), (2) the δ18O value of seawater has increased by 7-8‰ VSMOW through Paleozoic time, or (3) diagenesis has altered secular trends in early Paleozoic samples. Carbonate clumped isotope analysis, in combination with petrographic and elemental analysis, can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular δ18O increase. Clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late Cambrian- to Middle-late Ordovician-aged strata-the first paired fossil study of its kind-document tropical sea surface temperatures near modern temperatures (26-38 °C) and seawater oxygen isotope ratios similar to today's ratios.

  20. Design and characterization of a dead-time regime enhanced early photon projection imaging system

    NASA Astrophysics Data System (ADS)

    Sinha, L.; Fogarty, M.; Zhou, W.; Giudice, A.; Brankov, J. G.; Tichauer, K. M.

    2018-04-01

    Scattering of visible and near-infrared light in biological tissue reduces spatial resolution for imaging of tissues thicker than 100 μm. In this study, an optical projection imaging system is presented and characterized that exploits the dead-time characteristics typical of photon counting modules based on single photon avalanche diodes (SPADs). With this system, it is possible to attenuate the detection of more scattered late-arriving photons, such that detection of less scattered early-arriving photons can be enhanced with increased light intensity, without being impeded by the maximum count rate of the SPADs. The system has the potential to provide transmittance-based anatomical information or fluorescence-based functional information (with slight modification in the instrumentation) of biological samples with improved resolution in the mesoscopic domain (0.1-2 cm). The system design, calibration, stability, and performance were evaluated using simulation and experimental phantom studies. The proposed system allows for the detection of very-rare early-photons at a higher frequency and with a better signal-to-noise ratio. The experimental results demonstrated over a 3.4-fold improvement in the spatial resolution using early photon detection vs. conventional detection, and a 1000-fold improvement in imaging time using enhanced early detection vs. conventional early photon detection in a 4-mm thick phantom with a tissue-equivalent absorption coefficient of μa = 0.05 mm-1 and a reduced scattering coefficient of μs' = 5 mm-1.

  1. Coking-coal deposits of the western United States

    USGS Publications Warehouse

    Berryhill, Louise R.; Averitt, Paul

    1951-01-01

    Geohydrologic systems in the Anadarko basin in the central United States are controlled by topography, climate, geologic structures, and aquifer hydraulic properties, all of which are the result of past geologic and hydrologic processes, including tectonics and diagenesis. From Late Cambrian through Middle Ordovician time, a generally transgressive but cyclic sea covered the area. The first deposits were permeable sand, followed by calcareous mud. During periods of sea transgression, burial diagenesis decreased porosity and permeability. During Pennsylvanian time, rapid sedimentation accompanied rapid subsidence in the Anadarko basin. A geopressure zone probably resulted when sediments with little permeability trapped depositional water in Lower Pennsylvanian sands. Burial diagenesis included compaction and thermal alteration of deeply buried organic material, which released carbon dioxide, water, and hydrocarbons. By Middle Pennsylvanian time, the sea had submerged most of the central United States, including the Ozarks, as tectonic activity reached its maximum. During Late Pennsylvanian and Early Permian time, the Ouachita uplift had been formed and was higher than the Ozarks. Uplift was accompanied by a regional upward tilt toward the Ouachita-Ozarks area; the sea receded westward, depositing large quantities of calcareous mud and clay, and precipitating evaporitic material in the restricted-circulation environment. By the end of Permian time, > 20,000 ft of Pennsylvanian and Permian sediments had been deposited in the Anadarko basin. These thick sediments caused rapid and extreme burial diagensis, including alteration of organic material During Permian time in the Ozarks area, development of the Ozark Plateau aquifer system commenced in the permeable Cambrian-Mississippian rocks near the St. Francois Mountains as the Pennsylvanian confining material was removed. Since Permian time, uplift diagenesis has been more active than burial diagenesis in the Anadarko

  2. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution☆

    PubMed Central

    Fritz, H.; Abdelsalam, M.; Ali, K.A.; Bingen, B.; Collins, A.S.; Fowler, A.R.; Ghebreab, W.; Hauzenberger, C.A.; Johnson, P.R.; Kusky, T.M.; Macey, P.; Muhongo, S.; Stern, R.J.; Viola, G.

    2013-01-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara–Congo–Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian–Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite–Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650–620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo–Tanzania–Bangweulu Cratons and the Zimbabwe–Kalahari Craton. They closed during the ∼600–500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600–550 Ma extension is recorded in the Arabian–Nubian Shield and the Eastern Granulite–Cabo Delgado Nappe Complex. Later ∼550–480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings

  3. Detrimental Psychological Outcomes Associated with Early Pubertal Timing in Adolescent Girls

    PubMed Central

    Mendle, Jane; Turkheimer, Eric; Emery, Robert E.

    2010-01-01

    Though often discussed as though it were a discrete event, puberty comprises one segment of a larger developmental continuum and is notable for rapid transformation across a multitude of domains. Research suggests that an earlier rate of pubertal maturation in girls correlates with a number of detrimental outcomes compared with on-time or later maturation. The present review synthesizes the research on negative psychological sequelae of early pubertal timing in adolescent girls. Emphasis is on three theoretical perspectives by which precocious development is believed to affect the emergence of adverse outcomes: biological, psychosocial, and selection effects. PMID:20740062

  4. Early Pubertal Timing as a Vulnerability to Depression Symptoms: Differential Effects of Race and Sex

    PubMed Central

    Hamlat, Elissa J.; Stange, Jonathan P.; Alloy, Lauren B.; Abramson, Lyn Y.

    2013-01-01

    Robust evidence supports that girls and boys who experience early pubertal timing, maturing earlier than one’s peers, are vulnerable to developing symptoms of depression. However, it has yet to be clarified whether early pubertal timing confers vulnerability to African American as well as to Caucasian adolescents and whether this vulnerability is specific to depressive symptoms or can be generalized to symptoms of social anxiety. In previous studies, one race or one sex was examined in isolation or sample sizes were too small to examine racial differences. Our longitudinal study consisted of a sample of 223 adolescents (Mean age = 12.42, 54.3% female, 50.2% African American, and 49.8% Caucasian). At baseline, depressive symptoms, social anxiety symptoms, and pubertal timing were assessed by self-report. Nine months later, we assessed depressive symptoms, social anxiety symptoms, body esteem, and stressful life events that occurred between baseline and follow-up. Analyses indicated that early pubertal timing interacted with stressful life events to predict increased symptoms of depression, but only for Caucasian girls and African American boys. Results were found to be specific to depressive symptoms and did not generalize to symptoms of social anxiety. Additionally, there was a significant positive indirect effect of pubertal timing on symptoms of depression through body esteem for Caucasian females. PMID:24014162

  5. Time to hospitalization for suicide attempt by the timing of parental suicide during offspring early development

    PubMed Central

    Kuramoto, S. Janet; Runeson, Bo; Stuart, Elizabeth A.; Lichtenstein, Paul; Wilcox, Holly C.

    2013-01-01

    Context Previous studies have suggested that children who experience parental suicide at earlier ages are at higher risk of future hospitalization for suicide attempt. However, how the trajectories of risk differ by offspring age at the time of parental suicide is currently unknown. Objective To study time at risk to hospitalization for suicide attempt among offspring after experiencing parental suicide or accidental death by offspring developmental period at the time of parental death. Design Population-based retrospective cohort study Setting Sweden Participants 26,096 offspring who experienced parental suicide and 32,395 offspring of accident decedents prior to age 25 from 1973-2003. Main Outcome Measures Hospitalization for suicide attempt. Parametric survival analysis was used to model the time to hospitalization for suicide attempt across offspring who lost a parent during early childhood (0-5 years old), later childhood (6-12), adolescence (13-17) and young adulthood (18-24). Results The risk in offspring who lost a parent during early or late childhood surpassed the other two age groups’ hazards approximately 5 years after the origin and, for the youngest group, continued to rise over the course of decades. Offspring who lost a parent during adolescence or young adulthood were at greatest risk within 1 to 2 years after parental suicide, and risk declined over time. The shape of hospitalization risk was similar among those who experienced parental fatal accident. When the shape of hospitalization for suicide attempt at each developmental period was fixed to be the same between the two groups, offspring who lost a parent to suicide had earlier risk to hospitalization for suicide attempt hospitalization than offspring who lost a parent to an accident. Conclusion The hospitalization risk for suicide attempt in offspring who lost a parent during their childhood is different from those who lost a parent during adolescence or young adulthood. The results suggest

  6. Subdivision of the Cambrian-Ordovician Upper Sandstone Aquifer'' in the Fox Cities area, east-central Wisconsin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Erikson, K.A.; Smith, G.L.

    The informally-named Upper Sandstone Aquifer,'' a lithologically heterogeneous unit, has been subdivided into three thinner hydrostratigraphic units, the Upper Cambrian Jordan Formation (sandstone), the Lower Ordovician Prairie du Chien Group (dolomite), and the Middle Ordovician St. Peter Formation (mostly sandstone). Reevaluation of the Upper Sandstone Aquifer'' in the Fox Cities area (Appleton, Neenah, Menasha) was based on detailed analysis of 125 geologic well logs and 200 well-construction reports. Isopach maps and geologic cross-sections of these units in the Fox Cities area show extreme variations in thickness over short lateral distances. Although the Jordan Formation has a uniform thickness of 13more » m (40 ft), the Prairie du Chien Group varies from 0--88 m (0--275 ft). The St. Peter Formation varies in thickness from 0--108 m (0--335 ft). The Prairie du Chien Group is relatively thin or absent in the Fox Cities area in locations where the overlying St. Peter Formation is relatively thick. St Peter can be further subdivided into Readstown, Tonti, and Glenwood Members. The Readstown Member is a lithologically heterogeneous unit of variable thickness and distribution. The Tonti Member is a poorly cemented, fine-medium quartz arenite with which is lumped the Glenwood Member, a conglomeratic, silty medium-coarse sandstone. Maximum St. Peter thicknesses represent filled paleokarst depressions developed on top of the Prairie du Chien Group, with profound implications for estimates of hydraulic conductivity.« less

  7. Detection of early postseismic deformation from high-rate GNSS time series

    NASA Astrophysics Data System (ADS)

    Twardzik, C.; Vergnolle, M.; Avallone, A.; Sladen, A.

    2017-12-01

    Postseismic processes after an earthquake contribute to the redistribution of stresses in addition to that induced by the coseismic rupture. With the exception of very few studies (e.g., Miyazaki and Larson, 2008), most postseismic analyses only start one or two days following the mainshock. This leaves a critical part of postseismic phase unexplored, from a few minutes up to a few hours after the earthquake. In this study, we use kinematic precise point positioning (K-PPP) to analyze continuous GNSS data in order to obtain 30s position time series. These time series provide information on the surface displacements a soon as the dynamic response of the earthquake is over. Our first analysis focuses on the 2016 Pedernales, Ecuador, earthquake (Mw7.8). Using spectral analysis, we show that the typical logarithmic postseismic displacement trend can be detected as early as one to six hours after the earthquake depending on the station location and the level of noise. This analysis also allows to estimate the bias on the coseismic offsets usually based on daily pre- and post- earthquake positions. We use the early postseismic time series to test whether rate-and-state friction laws, traditionally used to explain postseismic processes days after the earthquake, still hold right after the mainshock. This study is being extended to two other subduction earthquakes: the 2010 Maule, Chile, earthquake (Mw8.8) and the 2015 Illapel, Chile, earthquake (Mw8.2).

  8. Inferring Arthropod Phylogeny: Fossils and their Interaction with Other Data Sources.

    PubMed

    Edgecombe, Gregory D

    2017-09-01

    The past five years have witnessed a renewed interest in discrete morphological characters as a source of phylogenetic data, after a decade or more of their dismissal in favor of molecules-only approaches. This has stemmed in large part from refinements in total evidence dating, which requires morphological character matrices for extinct and extant taxa as well as temporal data from fossils. The unique contribution of palaeontology is stem groups, revealing the sequence of character acquisition in long-branch terminals and otherwise unknown character combinations and/or character states in extinct phenotypes. The origin of mandibles exemplifies an integrative approach to analyzing the origin of a complex phenotypic feature using molecular, anatomical, and palaeontological data: (1) transcriptomics defends a single origin of mandibles in the clade Mandibulata; (2) Cambrian fossils inform on morphological changes in the gnathal appendages in the mandibulate stem group; (3) molecular dating, calibrated by fossils in novel modes of exceptional preservation, draws the mandibulate crown group into the early Cambrian and constrains the timing of character evolution; and (4) functional studies in extant taxa identify genes that specify mandibular identity from a maxilla and, ultimately, a trunk limb-like precursor, as predicted by the serial similarity of these appendages in Cambrian stem-group fossils. © The Author 2017. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

  9. Early mechanical stimulation only permits timely bone healing in sheep.

    PubMed

    Tufekci, Pelin; Tavakoli, Aramesh; Dlaska, Constantin; Neumann, Mirjam; Shanker, Mihir; Saifzadeh, Siamak; Steck, Roland; Schuetz, Michael; Epari, Devakar

    2018-06-01

    Bone fracture healing is sensitive to the fixation stability. However, it is unclear which phases of healing are mechano-sensitive and if mechanical stimulation is required throughout repair. In this study, a novel bone defect model, which isolates an experimental fracture from functional loading, was applied in sheep to investigate if stimulation limited to the early proliferative phase is sufficient for bone healing. An active fixator controlled motion in the fracture. Animals of the control group were unstimulated. In the physiological-like group, 1 mm axial compressive movements were applied between day 5 and 21, thereafter the movements were decreased in weekly increments and stopped after 6 weeks. In the early stimulatory group, the movements were stopped after 3 weeks. The experimental fractures were evaluated with mechanical and micro-computed tomography methods after 9 weeks healing. The callus strength of the stimulated fractures (physiological-like and early stimulatory) was greater than the unstimulated control group. The control group was characterized by minimal external callus formation and a lack of bone bridging at 9 weeks. In contrast, the stimulated groups exhibited advanced healing with solid bone formation across the defect. This was confirmed quantitatively by a lower bone volume in the control group compared to the stimulated groups.The novel experimental model permits the application of a well-defined load history to an experimental bone fracture. The poor healing observed in the control group is consistent with under-stimulation. This study has shown early mechanical stimulation only is sufficient for a timely healing outcome. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1790-1796, 2018. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  10. Early time evolution of a chemically produced electron depletion

    NASA Technical Reports Server (NTRS)

    Scales, W. A.; Bernhardt, P. A.; Ganguli, G.

    1995-01-01

    The early time evolution of an ionospheric electron depletion produced by a radially expanding electron attachment chemical release is studied with a two-dimensional simulation model. The model includes electron attachment chemistry, incorporates fluid electrons, particle ions and neutrals, and considers the evolution in a plane perpendicular to the geomagnetic field for a low beta plasma. Timescales considered are of the order of or less than the cyclotron period of the negative ions that result as a by-product of the electron attacment reaction. This corresponds to time periods of tenths of seconds during recent experiemts. Simulation results show that a highly sheared azimuthal electron flow velocity develops in the radially expanding depletion boundary. This sheared electron flow velocity and the steep density gradients in the boundary give rise to small-scale irregulatities in the form of electron density cavities and spikes. The nonlinear evolution of these irregularities results in trapping and ultimately turbulent heating of the negative ions.

  11. Group-Based Modeling of Time Spent in Structured Activity Trajectories from Middle Childhood into Early Adolescence

    ERIC Educational Resources Information Center

    Mata, Andrea D.; van Dulmen, Manfred H. M.

    2012-01-01

    This study investigated trajectories of time spent in structured activities from middle childhood to early adolescence by using data from the National Institute of Child Health & Human Development (NICHD) Study of Early Child Care. We used latent class growth analyses and identified five trajectories (stable low, increasing high, decreasing low,…

  12. Trait-based diversification shifts reflect differential extinction among fossil taxa

    PubMed Central

    Wagner, Peter J.; Estabrook, George F.

    2014-01-01

    Evolution provides many cases of apparent shifts in diversification associated with particular anatomical traits. Three general models connect these patterns to anatomical evolution: (i) elevated net extinction of taxa bearing particular traits, (ii) elevated net speciation of taxa bearing particular traits, and (iii) elevated evolvability expanding the range of anatomies available to some species. Trait-based diversification shifts predict elevated hierarchical stratigraphic compatibility (i.e., primitive→derived→highly derived sequences) among pairs of anatomical characters. The three specific models further predict (i) early loss of diversity for taxa retaining primitive conditions (elevated net extinction), (ii) increased diversification among later members of a clade (elevated net speciation), and (iii) increased disparity among later members in a clade (elevated evolvability). Analyses of 319 anatomical and stratigraphic datasets for fossil species and genera show that hierarchical stratigraphic compatibility exceeds the expectations of trait-independent diversification in the vast majority of cases, which was expected if trait-dependent diversification shifts are common. Excess hierarchical stratigraphic compatibility correlates with early loss of diversity for groups retaining primitive conditions rather than delayed bursts of diversity or disparity across entire clades. Cambrian clades (predominantly trilobites) alone fit null expectations well. However, it is not clear whether evolution was unusual among Cambrian taxa or only early trilobites. At least among post-Cambrian taxa, these results implicate models, such as competition and extinction selectivity/resistance, as major drivers of trait-based diversification shifts at the species and genus levels while contradicting the predictions of elevated net speciation and elevated evolvability models. PMID:25331898

  13. Trait-based diversification shifts reflect differential extinction among fossil taxa.

    PubMed

    Wagner, Peter J; Estabrook, George F

    2014-11-18

    Evolution provides many cases of apparent shifts in diversification associated with particular anatomical traits. Three general models connect these patterns to anatomical evolution: (i) elevated net extinction of taxa bearing particular traits, (ii) elevated net speciation of taxa bearing particular traits, and (iii) elevated evolvability expanding the range of anatomies available to some species. Trait-based diversification shifts predict elevated hierarchical stratigraphic compatibility (i.e., primitive→derived→highly derived sequences) among pairs of anatomical characters. The three specific models further predict (i) early loss of diversity for taxa retaining primitive conditions (elevated net extinction), (ii) increased diversification among later members of a clade (elevated net speciation), and (iii) increased disparity among later members in a clade (elevated evolvability). Analyses of 319 anatomical and stratigraphic datasets for fossil species and genera show that hierarchical stratigraphic compatibility exceeds the expectations of trait-independent diversification in the vast majority of cases, which was expected if trait-dependent diversification shifts are common. Excess hierarchical stratigraphic compatibility correlates with early loss of diversity for groups retaining primitive conditions rather than delayed bursts of diversity or disparity across entire clades. Cambrian clades (predominantly trilobites) alone fit null expectations well. However, it is not clear whether evolution was unusual among Cambrian taxa or only early trilobites. At least among post-Cambrian taxa, these results implicate models, such as competition and extinction selectivity/resistance, as major drivers of trait-based diversification shifts at the species and genus levels while contradicting the predictions of elevated net speciation and elevated evolvability models.

  14. Ultrasonic RF time series for early assessment of the tumor response to chemotherapy.

    PubMed

    Lin, Qingguang; Wang, Jianwei; Li, Qing; Lin, Chunyi; Guo, Zhixing; Zheng, Wei; Yan, Cuiju; Li, Anhua; Zhou, Jianhua

    2018-01-05

    Ultrasound radio-frequency (RF) time series have been shown to carry tissue typing information. To evaluate the potential of RF time series for early prediction of tumor response to chemotherapy, 50MCF-7 breast cancer-bearing nude mice were randomized to receive cisplatin and paclitaxel (treatment group; n = 26) or sterile saline (control group; n = 24). Sequential ultrasound imaging was performed on days 0, 3, 6, and 8 of treatment to simultaneously collect B-mode images and RF data. Six RF time series features, slope, intercept, S1, S2, S3 , and S4 , were extracted during RF data analysis and contrasted with microstructural tumor changes on histopathology. Chemotherapy administration reduced tumor growth relative to control on days 6 and 8. Compared with day 0, intercept, S1 , and S2 were increased while slope was decreased on days 3, 6, and 8 in the treatment group. Compared with the control group, intercept, S1, S2, S3 , and S4 were increased, and slope was decreased, on days 3, 6, and 8 in the treatment group. Tumor cell density decreased significantly in the latter on day 3. We conclude that ultrasonic RF time series analysis provides a simple way to noninvasively assess the early tumor response to chemotherapy.

  15. Comparisons of Lower Cambrian ( ) Chilhowee Group siliciclastics of the frontal Blue Ridge with possible equivalents in the central Blue Ridge and basement massifs in the southern Appalachians

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aylor, J.G. Jr.; Tull, J.F.

    1993-03-01

    The Lower Cambrian Chilhowee Group (CG) along the Blue Ridge (BR) foreland boundary may also be represented in more internal parts of the orogen. The relative palinspastic positions of these more internal CG( ) sequences are poorly constrained, but they are believed to represent more outboard facies than those along the frontal BR. Although correlation with CG rocks of the frontal BR is indefinite due to metamorphism and polydeformation, correlative sequences may include the cover of the Corbin and Salem Church gneisses (Pinelog Fm.), Grandfather Mountain window, Murphy belt (MB) (Hiwassee River Group), Tallulah and Toxaway domes (TTD) (quartzite-schist membermore » of the Tallulah Falls Fm.), Pine Mountain window (Hollis Quartzite), and Sauratown Mountains window (Hogan Creek and Sauratown Fms.). The CG is generally bounded on the west by the Great Smoky fault. Siliciclastics of the CG represent stacked, coarsening upward sequences, separated by transgressive facies, and capped by a highstand of the Shady Dolomite or its equivalents. CG correlations in the Kahatchee Mountain Group of the Talladega belt and the siliciclastics in the Hiwassee River Group of the MB are supported by fossil constraints. Other units are correlated with CG based upon intimate associations with marble believed to be equivalent to the overlying Lower Cambrian Shady Dolomite, or upon presumed uncomformable relationships above Grenville basement. The CG averages about 1,260 meters thickness at the frontal BR, whereas lower siliciclastics in the MB average 1,830 meters. The Pinelog Fm. is up to 600 meters thick. The Hollis Quartzite is approximately 325 meters thick, and the estimated thickness of the quartz-schist member at Tallulah Falls is up to 900 meters. More distal siliciclastics of the central BR in the MB and distal siliciclastics overlying basement were deposited farther out on the shelf as stratigraphic, litho-facies equivalents of shallower marine and continental deposits of the

  16. Long distance transport of eclogite and blueschist during early Pacific Ocean subduction rollback

    NASA Astrophysics Data System (ADS)

    Tamblyn, Renee; Hand, Martin; Kelsey, David; Phillips, Glen; Anczkiewicz, Robert

    2017-04-01

    The Tasmanides in eastern Australia represent a period of continental crustal growth on the western margin of the Pacific Ocean associated with slab rollback from the Cambrian until the Triassic. During rollback numerical models predict that subduction products can become trapped in the forearc (Geyra et al., 2002), and can migrate with the trench as it retreats. In a long-lived subduction controlled regime such as the Tasmanides, this should result in an accumulation of subduction products with protracted geochronological and metamorphic histories. U-Pb, Lu-Hf, Sm-Nd and Ar-Ar geochronology and phase equilibria modelling of lawsonite-eclogite and garnet blueschist in the Southern New England Fold Belt in Australia demonstrate that high-P low-T rocks remained within a subduction setting for c. 40 Ma, from c. 500 to 460 Ma. High-P metamorphic rocks initially formed close to the Australian cratonic margin during the late Cambrian, and were subsequently transported over 1500 Ma oceanward, during which time subducted material continued to accumulate, resulting in the development of complex mélange which records eclogite and blueschist metamorphism and partial exhumation over 40 Ma. The duration of refrigerated metamorphism approximates the extensional evolution of the upper plate which culminated in the development of the Lachlan Fold Belt. The protracted record of eclogite and blueschist metamorphism indicates that rapid exhumation is not necessarily required for preservation of high-pressure metamorphic rocks from subduction systems. Reference: Gerya, T. V., Stockhert, B., & Perchuk, A. L. (2002). Exhumation of high-pressure metamorphic rocks in a subduction channel: A numerical simulation. Tectonics, 21(6), 6-1-6-19. doi:10.1029/2002tc001406

  17. A balancing act in an unknown territory: a metasynthesis of first-time mothers' experiences in early labour.

    PubMed

    Eri, Tine S; Bondas, Terese; Gross, Mechthild M; Janssen, Patricia; Green, Josephine M

    2015-03-01

    to integrate findings of individual studies in order to broaden the understanding of first-time mothers' experiences of early labour. the methodology was metasynthesis which is based on the interpretive meta-ethnography described by Noblit and Hare (1988). Metasynthesis is research on research which synthesises the findings of previous qualitative studies, and the focus is on interpretation and the creation of new knowledge. all included studies originated from high resource countries (USA 2, UK 4, and Scandinavia 5) and all were carried out in a context of hospital based maternity care. a total of 231 women participated in the studies. 11 articles were included. The main results are presented with the metaphor a balancing act in an unknown territory. The 'unknown territory' has a double meaning: as the personal experience of going into labour for the first time and as encountering the maternity care system. On both levels women have to make significant decisions: whether labour really has started and subsequently when to go to the hospital. A key challenge is to balance the arrival on the labour ward at the 'right' time, not too early and not too late. Arriving at the 'right' time leads to a positive path, while arriving 'too soon' might lead to a cascade of negative experiences. The results are further presented with five central themes: 'Finding out if labour has started is absorbing'; 'Dealing with labour at home'; 'Trying to arrive at the labour ward at the right time'; 'There is always a risk of being sent home'; 'Encountering health professionals arouses strong emotions'. the metasynthesis broadens the understanding of first-time mothers' experiences of early labour, and suggests that women's needs when planning a hospital birth are not being adequately met at this stage in the labour process. Three areas of future research are suggested: how to support and strengthen women during pregnancy in order to cope with early labour; women's experiences of early

  18. Paleozoic and Mesozoic silica-rich seawater: Evidence from hematitic chert (jasper) deposits

    USGS Publications Warehouse

    Grenne, Tor; Slack, J.F.

    2003-01-01

    Laterally extensive beds of highly siliceous, hematitic chert (jasper) are associated with many volcanogenic massive sulfide (VMS) deposits of Late Cambrian to Early Cretaceous age, yet are unknown in analogous younger (including modern) settings. Textural studies suggest that VMS-related jaspers in the Ordovician Løkken ophiolite of Norway were originally deposited as Si- and Fe-rich gels that precipitated from hydrothermal plumes as colloidal silica and iron-oxyhydroxide particles. Rare earth element patterns and Ge/Si ratios of the jaspers reflect precipitation from plumes having seawater dilution factors of 103 to 104, similar to modern examples. We propose that silica in the ancient jaspers is not derived from submarine hydrothermal fluids-as suggested by previous workers-but instead was deposited from silic-rich sea-water. Flocculation and precipitation of the silica were triggered inorganically by the bridging effect of positively charged iron oxyhydroxides in the hydrothermal plume. A model involving amorphous silica (opal-A) precursors to the jaspers suggests that silica contents of Cambrian-Early Cretaceous oceans were at least 110 mg/L SiO2, compared to values of 40-60 mg/L SiO2 estimated in other studies. The evolution of ancient silica-rich to modern Fe-rich precipitates in submarine-hydrothermal plumes reflects a changeover from silica-saturated to silica-depleted seawater through Phanerozoic time, due mainly to ocean-wide emergence of diatoms in the Cretaceous.

  19. Neoproterozoic complexes of the shelf cover of the Dzabkhan terrane basement in the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Kozakov, I. K.; Kuznetsov, A. B.; Erdenegargal, Ch.; Salnikova, E. B.; Anisimova, I. V.; Plotkina, Ju. V.; Fedoseenko, A. M.

    2017-09-01

    The formation stages of high-grade metamorphic complexes and the related granitoids of the Dzabkhan terrane basement are considered. The age data (U-Pb method, TIMS) of zircons from the trondhjemite block of the eastern part of the Dzabkhan terrane, which is directly overlain by the dolomite sequence of the Tsagaan Oloom Formation, are given. Trondhjemites yield the U-Pb zircon age of 862 ± 3 Ma. In their structural position, they are assigned to typical postmetamorphic formations that determine the formation and cratonization of rocks of the host block. The geochronological study of trondhjemites gives grounds to distinguish fragments of the continental crust in the Dzabkhan terrane basement, the formation of which occurred at different periods of time: ˜860 and ˜790 Ma. Geological-geochronological and Sm‒Nd isotope-geochemical studies indicate that the Dzabkhan terrane basement is not a single block of the Early Precambrian continental crust, but a composite terrane, comprising Neoproterozoic ensialic and island-arc structural and compositional complexes. Correlation of Sr isotopic characteristics with the 87Sr/86Sr variation curve in the Neoproterozoic and Cambrian seawater shows that carbonate deposits accumulated at the eastern margin of the Dzabkhan terrane near the end of the Neoproterozoic, 700-550 Ma, and in the central part of the terrane in the Early Cambrian, 540-530 Ma.

  20. Reaction Time Is Negatively Associated with Corpus Callosum Area in the Early Stages of CADASIL.

    PubMed

    Delorme, S; De Guio, F; Reyes, S; Jabouley, A; Chabriat, H; Jouvent, E

    2017-11-01

    Reaction time was recently recognized as a marker of subtle cognitive and behavioral alterations in the early clinical stages of CADASIL, a monogenic cerebral small-vessel disease. In unselected patients with CADASIL, brain atrophy and lacunes are the main imaging correlates of disease severity, but MR imaging correlates of reaction time in mildly affected patients are unknown. We hypothesized that reaction time is independently associated with the corpus callosum area in the early clinical stages of CADASIL. Twenty-six patients with CADASIL without dementia (Mini-Mental State Examination score > 24 and no cognitive symptoms) and without disability (modified Rankin Scale score ≤ 1) were compared with 29 age- and sex-matched controls. Corpus callosum area was determined on 3D-T1 MR imaging sequences with validated methodology. Between-group comparisons were performed with t tests or χ 2 tests when appropriate. Relationships between reaction time and corpus callosum area were tested using linear regression modeling. Reaction time was significantly related to corpus callosum area in patients (estimate = -7.4 × 10 3 , standard error = 3.3 × 10 3 , P = .03) even after adjustment for age, sex, level of education, and scores of depression and apathy (estimate = -12.2 × 10 3 , standard error = 3.8 × 10 3 , P = .005). No significant relationship was observed in controls. Corpus callosum area, a simple and robust imaging parameter, appears to be an independent correlate of reaction time at the early clinical stages of CADASIL. Further studies will determine whether corpus callosum area can be used as an outcome in future clinical trials in CADASIL or in more prevalent small-vessel diseases. © 2017 by American Journal of Neuroradiology.

  1. Depositional and diagenetic variability within the Cambrian Mount Simon Sandstone: Implications for carbon dioxide sequestration

    USGS Publications Warehouse

    Bowen, B.B.; Ochoa, R.I.; Wilkens, N.D.; Brophy, J.; Lovell, T.R.; Fischietto, N.; Medina, C.R.; Rupp, J.A.

    2011-01-01

    The Cambrian Mount Simon Sandstone is the major target reservoir for ongoing geologic carbon dioxide (CO2) sequestration demonstrations throughout the midwest United States. The potential CO2 reservoir capacity, reactivity, and ultimate fate of injected CO2 depend on textural and compositional properties determined by depositional and diagenetic histories that vary vertically and laterally across the formation. Effective and efficient prediction and use of the available pore space requires detailed knowledge of the depositional and diagenetic textures and mineralogy, how these variables control the petrophysical character of the reservoir, and how they vary spatially. Here, we summarize the reservoir characteristics of the Mount Simon Sandstone based on examination of geophysical logs, cores, cuttings, and analysis of more than 150 thin sections. These samples represent different parts of the formation and depth ranges of more than 9000 ft (>2743 m) across the Illinois Basin and surrounding areas. This work demonstrates that overall reservoir quality and, specifically, porosity do not exhibit a simple relationship with depth, but vary both laterally and with depth because of changes in the primary depositional facies, framework composition (i.e., feldspar concentration), and diverse diagenetic modifications. Diagenetic processes that have been significant in modifying the reservoir include formation of iron oxide grain coatings, chemical compaction, feldspar precipitation and dissolution, multiple generations of quartz overgrowth cementation, clay mineral precipitation, and iron oxide cementation. These variables provide important inputs for calculating CO2 capacity potential, modeling reactivity, and are also an important baseline for comparisons after CO2 injection. Copyright ??2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  2. Time Outdoors at Specific Ages During Early Childhood and the Risk of Incident Myopia.

    PubMed

    Shah, Rupal L; Huang, Yu; Guggenheim, Jeremy A; Williams, Cathy

    2017-02-01

    Time outdoors during childhood is negatively associated with incident myopia. Consequently, additional time outdoors has been suggested as a public health intervention to reduce the prevalence of myopia. We investigated whether there were specific ages during early childhood when the time outdoors versus incident myopia association was strongest. Children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) were studied from age 2 to 15 years. Parentally reported time outdoors and time spent reading were assessed longitudinally in early childhood (ages 2, 3, 4, 5, 7, and 9 years). Noncycloplegic autorefraction was carried out longitudinally in later childhood (ages 10, 11, 12, and 15 years). Information was available for 2833 participants. Cox proportional hazards regression was used to test for association between time outdoors and incident myopia. From 3 years of age onward, greater time outdoors was associated with a reduced risk of incident myopia. The hazard ratio for myopia changed progressively from 0.90 (95% CI 0.83-0.98, P = 0.012) at age 3 years, to 0.86 (95% CI 0.78-0.93, P = 0.001) at age 9 years, for each additional SD of time spent outdoors per day. These associations were independent of two major risk factors for myopia: time reading and number of myopic parents. Additional time spent outdoors across the 3 to 9 years age range was associated with a reduced incidence of myopia between ages 10 and 15 years. There was a trend for the association to increase toward the older end of the 3 to 9 years range.

  3. Irregular oscillatory patterns in the early-time region of coherent phonon generation in silicon

    NASA Astrophysics Data System (ADS)

    Watanabe, Yohei; Hino, Ken-ichi; Hase, Muneaki; Maeshima, Nobuya

    2017-09-01

    Coherent phonon (CP) generation in an undoped Si crystal is theoretically investigated to shed light on unexplored quantum-mechanical effects in the early-time region immediately after the irradiation of ultrashort laser pulses. We examine time signals attributed to an induced charge density of an ionic core, placing the focus on the effects of the Rabi frequency Ω0 c v on the signals; this frequency corresponds to the peak electric-field of the pulse. It is found that at specific Ω0 c v's, where the energy of plasmon caused by photoexcited carriers coincides with the longitudinal-optical phonon energy, the energetically resonant interaction between these two modes leads to striking anticrossings, revealing irregular oscillations with anomalously enhanced amplitudes in the observed time signals. Also, the oscillatory pattern is subject to the Rabi flopping of the excited carrier density that is controlled by Ω0 c v. These findings show that the early-time region is enriched with quantum-mechanical effects inherent in the CP generation, though experimental signals are more or less masked by the so-called coherent artifact due to nonlinear optical effects.

  4. Geologically Controlled Isotope-Time Patterns Reveal Early Differentiation and Crust Formation Processes

    NASA Astrophysics Data System (ADS)

    Bennett, V. C.; Nutman, A. P.

    2014-12-01

    The mechanisms of continental crust production and evolution in the early Earth remain controversial, as are questions of the relative roles of early differentiation versus subsequent tectonic procssing in creating Earth's chemical signatures. Here we present geologic observations integrated with whole rock major, trace element and Sm-Nd isotopic signatures and combined with U-Pb and Lu-Hf isotopic compositions of zircon populations from the same rocks, from the most extensive early rock record comprising the 3.9 Ga to 3.6 Ga terranes of southwest Greenland. These data reveal repeated patterns of formation of juvenile TTG crust and associated mafic and ultramafic rocks in convergent margin settings followed by formation of more evolved granites [1]. Our new zircon Lu-Hf data from rare 3.6-3.7 Ga tonalites within the Itsaq Gneiss Complex, obtained from single component, non-migmatitic gneisses with simple zircon populations, limited within sample Hf isotopic variability and accurate U-Pb ages, now document extraction of juvenile tonalites from a near chondritic mantle source between 3.9 Ga and 3.6 Ga. The more evolved, granitic rocks in each area show slightly negative initial ɛHf in accord with crustal reworking of the older (3.8-3.9 Ga) gniesses. There is no evidence for Hadean material in the sources of the granitoids. The Hf isotope-time patterns are consistent with juvenile crust production from a mantle source that experienced only modest amounts of prior crustal extraction. They are distinct from those predicted by reprocessing of an enriched Hadean mafic crust, as has been proposed for this region [2] and for the source of the Hadean Jack Hills zircons [3]. The well-documented, time decreasing, positive 142Nd anomalies [e.g., 4] from these rocks are further evidence of crustal derivation from a convecting mantle source, rather than reworking of an enriched mafic lithosphere. The 143Nd isotopic -time patterns are more complex, reflecting the interplay

  5. Early evolution of multifocal optics for well-focused colour vision in vertebrates.

    PubMed

    Gustafsson, O S E; Collin, S P; Kröger, R H H

    2008-05-01

    Jawless fishes (Agnatha; lampreys and hagfishes) most closely resemble the earliest stage in vertebrate evolution and lamprey-like animals already existed in the Lower Cambrian [about 540 million years ago (MYA)]. Agnathans are thought to have separated from the main vertebrate lineage at least 500 MYA. Hagfishes have primitive eyes, but the eyes of adult lampreys are well-developed. The southern hemisphere lamprey, Geotria australis, possesses five types of opsin genes, three of which are clearly orthologous to the opsin genes of jawed vertebrates. This suggests that the last common ancestor of all vertebrate lineages possessed a complex colour vision system. In the eyes of many bony fishes and tetrapods, well-focused colour images are created by multifocal crystalline lenses that compensate for longitudinal chromatic aberration. To trace the evolutionary origins of multifocal lenses, we studied the optical properties of the lenses in four species of lamprey (Geotria australis, Mordacia praecox, Lampetra fluviatilis and Petromyzon marinus), with representatives from all three of the extant lamprey families. Multifocal lenses are present in all lampreys studied. This suggests that the ability to create well-focused colour images with multifocal optical systems also evolved very early.

  6. Early and Real-Time Detection of Seasonal Influenza Onset

    PubMed Central

    Marques-Pita, Manuel

    2017-01-01

    Every year, influenza epidemics affect millions of people and place a strong burden on health care services. A timely knowledge of the onset of the epidemic could allow these services to prepare for the peak. We present a method that can reliably identify and signal the influenza outbreak. By combining official Influenza-Like Illness (ILI) incidence rates, searches for ILI-related terms on Google, and an on-call triage phone service, Saúde 24, we were able to identify the beginning of the flu season in 8 European countries, anticipating current official alerts by several weeks. This work shows that it is possible to detect and consistently anticipate the onset of the flu season, in real-time, regardless of the amplitude of the epidemic, with obvious advantages for health care authorities. We also show that the method is not limited to one country, specific region or language, and that it provides a simple and reliable signal that can be used in early detection of other seasonal diseases. PMID:28158192

  7. Arthropod colonization of land--linking molecules and fossils in oribatid mites (Acari, Oribatida).

    PubMed

    Schaefer, Ina; Norton, Roy A; Scheu, Stefan; Maraun, Mark

    2010-10-01

    Terrestrial fossils that document the early colonization of land are scarce for >100 my after the Cambrian explosion. This raises the question whether life on land did not exist or just did not fossilize. With a molecular dating technique, we analyzed the origin of terrestrial chelicerate microarthropods (Acari, Oribatida) which have a fossil record since the Middle Devonian that is exceptional among soil animals. Our results suggest that oribatid mites originated in the Precambrian (571+/-37 mya) and that the radiation of basal groups coincides with the gap in the terrestrial fossil record between the Cambrian explosion and the earliest fossilized records of continental ecosystems. Further, they suggest that the colonization of land started via the interstitial, approximately 150 my earlier than the oldest fossils of terrestrial ecosystems. Overall, the results imply that omnivorous and detritivorous arthropods formed a major component in early terrestrial food webs, thereby facilitating the invasion of terrestrial habitats by later colonizers of higher trophic levels. Copyright 2010 Elsevier Inc. All rights reserved.

  8. Le graben de l'Anti-Atlas occidental (Maroc) : contrôle tectonique de la paléogéographie et des séquences au Cambrien inférieurThe Lower-Cambrian western Anti-Atlasic graben: tectonic control of palaeogeography and sequential organisation

    NASA Astrophysics Data System (ADS)

    Benssaou, Mohammed; Hamoumi, Naı̈ma

    2003-03-01

    In the Moroccan western Anti-Atlas, the combined extensive tectonic events with a long-term sea-level rise is the main factor on building vertical stacking transgressive-regressive sequences. In the Ait Abdallah-Boussafene axis, the subsidence processes, relayed by a brutal platform tilting generated an elongated NE-SW graben. This is an evidence of the persistence of the Anti-Atlasic rifting process during the last part of the Lower-Cambrian succession.

  9. Oceanic oxygenation events in the anoxic Ediacaran ocean.

    PubMed

    Sahoo, S K; Planavsky, N J; Jiang, G; Kendall, B; Owens, J D; Wang, X; Shi, X; Anbar, A D; Lyons, T W

    2016-09-01

    The ocean-atmosphere system is typically envisioned to have gone through a unidirectional oxygenation with significant oxygen increases in the earliest (ca. 635 Ma), middle (ca. 580 Ma), or late (ca. 560 Ma) Ediacaran Period. However, temporally discontinuous geochemical data and the patchy metazoan fossil record have been inadequate to chart the details of Ediacaran ocean oxygenation, raising fundamental debates about the timing of ocean oxygenation, its purported unidirectional rise, and its causal relationship, if any, with the evolution of early animal life. To better understand the Ediacaran ocean redox evolution, we have conducted a multi-proxy paleoredox study of a relatively continuous, deep-water section in South China that was paleogeographically connected with the open ocean. Iron speciation and pyrite morphology indicate locally euxinic (anoxic and sulfidic) environments throughout the Ediacaran in this section. In the same rocks, redox sensitive element enrichments and sulfur isotope data provide evidence for multiple oceanic oxygenation events (OOEs) in a predominantly anoxic global Ediacaran-early Cambrian ocean. This dynamic redox landscape contrasts with a recent view of a redox-static Ediacaran ocean without significant change in oxygen content. The duration of the Ediacaran OOEs may be comparable to those of the oceanic anoxic events (OAEs) in otherwise well-oxygenated Phanerozoic oceans. Anoxic events caused mass extinctions followed by fast recovery in biologically diversified Phanerozoic oceans. In contrast, oxygenation events in otherwise ecologically monotonous anoxic Ediacaran-early Cambrian oceans may have stimulated biotic innovations followed by prolonged evolutionary stasis. © 2016 John Wiley & Sons Ltd.

  10. Rhenium and osmium isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada, and Hunan and Guizhou provinces, China

    USGS Publications Warehouse

    Horan, M.F.; Morgan, J.W.; Grauch, R.I.; Coveney, R.M.; Murowchick, J.B.; Hulbert, L.J.

    1994-01-01

    Rhenium and osmium abundances and osmium isotopic compositions were determined by negative thermal ionization mass spectrometry for samples of Devonian black shale and an associated Ni-enriched sulfide layer from the Yukon Territory, Canada. The same composition information was also obtained for samples of early Cambrian Ni-Mo-rich sulfide layers hosted in black shale in Guizhou and Hunan provinces, China. This study was undertaken to constrain the origin of the PGE enrichment in the sulfide layers. Samples of the Ni sulfide layer from the Yukon Territory are highly enriched in Re, Os, and other PGE, with distinctly higher Re/192Os but similar Pt/Re, compared to the black shale host. Re-Os isotopic data of the black shale and the sulfide layer are approximately isochronous, and the data plot close to reference isochrons which bracket the depositional age of the enclosing shales. Samples of the Chinese sulfide layers are also highly enriched in Re, Os, and the other PGE. Re/192Os are lower than in the Yukon sulfide layer. Re-Os isotopic data for the sulfide layers lie near a reference isochron with an age of 560 Ma, similar to the depositional age of the black shale host. The osmium isotopic data suggest that Re and PGE enrichment of the brecciated sulfide layers in both the Yukon Territory and in southern China may have occurred near the time of sediment deposition or during early diagenesis, during the middle to late Devonian and early Cambrian, respectively. ?? 1994.

  11. Calculational investigation of impact cratering dynamics - Early time material motions

    NASA Technical Reports Server (NTRS)

    Thomsen, J. M.; Austin, M. G.; Ruhl, S. F.; Schultz, P. H.; Orphal, D. L.

    1979-01-01

    Early time two-dimensional finite difference calculations of laboratory-scale hypervelocity (6 km/sec) impact of 0.3 g spherical 2024 aluminum projectiles into homogeneous plasticene clay targets were performed and the resulting material motions analyzed. Results show that the initial jetting of vaporized target material is qualitatively similar to experimental observation. The velocity flow field developed within the target is shown to have features quite similar to those found in calculations of near-surface explosion cratering. Specific application of Maxwell's analytic Z-Model (developed to interpret the flow fields of near-surface explosion cratering calculations), shows that this model can be used to describe the flow fields resulting from the impact cratering calculations, provided that the flow field center is located beneath the target surface, and that application of the model is made late enough in time that most of the projectile momentum has been dissipated.

  12. Turnaround Time for Early Infant HIV Diagnosis in Rural Zambia: A Chart Review

    PubMed Central

    Sutcliffe, Catherine G.; van Dijk, Janneke H.; Hamangaba, Francis; Mayani, Felix; Moss, William J.

    2014-01-01

    Background Early infant HIV diagnosis is challenging in sub-Saharan Africa, particularly in rural areas where laboratory capacity is limited. Specimens must be transported to central laboratories for testing, leading to delays in diagnosis and initiation of antiretroviral therapy. This study was undertaken in rural Zambia to measure the turnaround time for confirmation of HIV infection and identify delays in diagnosis. Methods Chart reviews were conducted from 2010–2012 for children undergoing early infant HIV diagnosis at Macha Hospital in Zambia. Relevant dates, receipt of drugs by mother and child for the prevention of mother-to-child transmission (PMTCT), and test results were abstracted. Results 403 infants provided 476 samples for early infant diagnosis. The median age at the “6-week” and “6-month” assessments was 8.1 weeks and 7.0 months, respectively. The majority of mothers (80%) and infants (67%) received PMTCT. The median time between sample collection and arrival at the central laboratory in Lusaka was 17 days (IQR: 10, 28); arrival at the central laboratory to testing was 6 days (IQR: 5, 11); testing to return of results to the clinic was 29 days (IQR: 17, 36); arrival of results at the clinic to return of results to the caregiver was 45 days (IQR: 24, 79). The total median time from sample collection to return of results to the caregiver was 92 days (IQR: 84, 145). The proportion of HIV PCR positive samples was 12%. The total median turnaround time was shorter for HIV PCR positive as compared to negative or invalid samples (85 vs. 92 days; p = 0.08). Conclusions Delays in processing and communicating test results were identified, particularly in returning results from the central laboratory to the clinic and from the clinic to the caregiver. A more efficient process is needed so that caregivers can be provided test results more rapidly, potentially resulting in earlier treatment initiation and better outcomes for HIV-infected infants

  13. The Role of Peer Stress and Pubertal Timing on Symptoms of Psychopathology during Early Adolescence

    ERIC Educational Resources Information Center

    Sontag, Lisa M.; Graber, Julia A.; Clemans, Katherine H.

    2011-01-01

    Stress is known to amplify the link between pubertal timing and psychopathology. However, few studies have examined the role of peer stress as a context for this link. The present study examined the interaction between perceived pubertal timing and peer stress on symptoms of psychopathology in early adolescence. The sample consisted of 264…

  14. Time perception impairment in early-to-moderate stages of Huntington's disease is related to memory deficits.

    PubMed

    Righi, Stefania; Galli, Luca; Paganini, Marco; Bertini, Elisabetta; Viggiano, Maria Pia; Piacentini, Silvia

    2016-01-01

    Huntington's disease (HD) primarily affects striatum and prefrontal dopaminergic circuits which are fundamental neural correlates of the timekeeping mechanism. The few studies on HD mainly investigated motor timing performance in second durations. The present work explored time perception in early-to-moderate symptomatic HD patients for seconds and milliseconds with the aim to clarify which component of the scalar expectancy theory (SET) is mainly responsible for HD timing defect. Eleven HD patients were compared to 11 controls employing two separate temporal bisection tasks in second and millisecond ranges. Our results revealed the same time perception deficits for seconds and milliseconds in HD patients. Time perception impairment in early-to-moderate stages of Huntington's disease is related to memory deficits. Furthermore, both the non-systematical defect of temporal sensitivity and the main impairment of timing performance in the extreme value of the psychophysical curves suggested an HD deficit in the memory component of the SET. This result was further confirmed by the significant correlations between time perception performance and long-term memory test scores. Our findings added important preliminary data for both a deeper comprehension of HD time-keeping deficits and possible implications on neuro-rehabilitation practices.

  15. Pre-mesozoic palinspastic reconstruction of the eastern great basin (Western United States).

    PubMed

    Levy, M; Christie-Blick, N

    1989-09-29

    The Great Basin of the western United States has proven important for studies of Proterozoic and Paleozoic geology [2500 to 245 million years ago (Ma)] and has been central to the development of ideas about the mechanics of crustal shortening and extension. An understanding of the deformational history of this region during Mesozoic and Cenozoic time (245 Ma to the present) is required for palinspastic reconstruction of now isolated exposures of older geology in order to place these in an appropriate regional geographic context. Considerable advances in unraveling both the crustal shortening that took place during Mesozoic to early Cenozoic time (especially from about 150 to 50 Ma) and the extension of the past 37 million years have shown that earlier reconstructions need to be revised significantly. A new reconstruction is developed for rocks of middle Proterozoic to Early Cambrian age based on evidence that total shortening by generally east-vergent thrusts and folds was at least 104 to 135 kilometers and that the Great Basin as a whole accommodated approximately 250 kilometers of extension in the direction 287 degrees +/- 12 degrees between the Colorado Plateau and the Sierra Nevada. Extension is assumed to be equivalent at all latitudes because available paleomagnetic evidence suggests that the Sierra Nevada experienced little or no rotation with respect to the extension direction since the late Mesozoic. An estimate of the uncertainty in the amount of extension obtained from geological and paleomagnetic uncertainties increases northward from +/-56 kilometers at 36 degrees 30N to (-87)(+108) kilometers at 40 degrees N. On the basis of the reconstruction, the original width of the preserved part of the late Proterozoic and Early Cambrian basin was about 150 to 300 kilometers, about 60 percent of the present width, and the basin was oriented slightly more north-south with respect to present-day coordinates.

  16. Time Outdoors at Specific Ages During Early Childhood and the Risk of Incident Myopia

    PubMed Central

    Shah, Rupal L.; Huang, Yu; Guggenheim, Jeremy A.; Williams, Cathy

    2017-01-01

    Purpose Time outdoors during childhood is negatively associated with incident myopia. Consequently, additional time outdoors has been suggested as a public health intervention to reduce the prevalence of myopia. We investigated whether there were specific ages during early childhood when the time outdoors versus incident myopia association was strongest. Methods Children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC) were studied from age 2 to 15 years. Parentally reported time outdoors and time spent reading were assessed longitudinally in early childhood (ages 2, 3, 4, 5, 7, and 9 years). Noncycloplegic autorefraction was carried out longitudinally in later childhood (ages 10, 11, 12, and 15 years). Information was available for 2833 participants. Cox proportional hazards regression was used to test for association between time outdoors and incident myopia. Results From 3 years of age onward, greater time outdoors was associated with a reduced risk of incident myopia. The hazard ratio for myopia changed progressively from 0.90 (95% CI 0.83–0.98, P = 0.012) at age 3 years, to 0.86 (95% CI 0.78–0.93, P = 0.001) at age 9 years, for each additional SD of time spent outdoors per day. These associations were independent of two major risk factors for myopia: time reading and number of myopic parents. Conclusions Additional time spent outdoors across the 3 to 9 years age range was associated with a reduced incidence of myopia between ages 10 and 15 years. There was a trend for the association to increase toward the older end of the 3 to 9 years range. PMID:28245296

  17. "Soft-shelled" monothalamid foraminifers as a modern analogue of early life

    NASA Astrophysics Data System (ADS)

    Kitazato, Hiroshi; Ohkawara, Nina; Gooday, Andrew

    2017-04-01

    According to the fossil record, the earliest undoubted foraminifers are found in the Early Cambrian, where they are represented by tubular agglutinated forms, thought to be the most primitive foraminiferal morphotypes. The numerous foraminifers with single-chambered, organic-walled tests (i.e. 'soft-shelled' monothalamids) exist in the deep sea and are difficult to preserve as fossils. Molecular phylogenetic data tell us that these 'primitive' taxa include the deepest foraminiferal clades, originating around 600 - 900 Ma. We found many soft-shelled monothalamids in sediment samples from deep trenches, including the Challenger Deep (Marianas Trench) and the Horizon Deep (Tonga Trench). Both deeps exceed 10,000 m water depth, well below the carbonate compensation depth, which represents an environmental barrier for calcareous foraminifera. The foraminifera at these extreme hadal sites include tubular and globular forms with organic walls, among which species of the genera Nodellum and Resigella are particularly abundant. Some forms selectively agglutinate minute flakes of clay minerals on the surface of the organic test. Many soft-shelled monothalamids, including most of those in deep tranches, contain stercomata, the function of which is currently unknown. Gromiids (a rhizarian group related to foraminifera) also accumulate stercomata in their sack-shaped tests. This suggests the possibility that the function of these waste particles is to add bulk, like the filling of soft bags or pillows. We suggest that the monothalamid foraminifera that dominate small-sized eukaryotes in extreme hadal settings may provide clues to understanding the biology and ecology of early life in Neoproterozoic sedimented habitats.

  18. The Ross Orogen and Lachlan Fold Belt in Marie Byrd Land, Northern Victoria Land and New Zealand: implication for the tectonic setting of the Lachlan Fold Belt in Antarctica

    USGS Publications Warehouse

    Bradshaw, J.D.

    2007-01-01

    Correlation of the Cambrian Delamerian Orogen of Australia and Ross Orogen of the Transantarctic Mountains widely accepted but the extension of the adjacent Lachlan Orogen into Antarctica is controversial. Outside the main Ross-Delamerian belt, evidence of this orogeny is preserved at Mt Murphy in Marie Byrd Land and the in Takaka Terrane of New Zealand. In all pre-break- configurations of the SW Pacific, these two areas are far removed from the Ross-Delamerian belt. Evidence from conglomerates in the Takaka Terrane, however, shows that in Late Cambrian times it was adjacent to the Ross Orogen. This indicates major tectonic displacements within Gondwana after the Cambrian and before break-up. The Lachlan Orogen formed in an extensional belt in a supra-subduction zone setting and the Cambrian rocks of Marie Byrd Land and New Zealand are interpreted as parts of a rifted continental ribbon on the outboard side of the Lachlan belt.

  19. Evidence for Cambrian petroleum source rocks in the Rome trough of West Virginia and Kentucky, Appalachian basin: Chapter G.8 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    USGS Publications Warehouse

    Ryder, Robert T.; Harris, David C.; Gerome, Paul; Hainsworth, Timothy J.; Burruss, Robert A.; Lillis, Paul G.; Jarvie, Daniel M.; Pawlewicz, Mark J.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    The bitumen extract from the Rogersville Shale compares very closely with oils or condensates from Cambrian reservoirs in the Carson Associates No. 1 Kazee well, Homer gas field, Elliott County, Ky.; the Inland No. 529 White well, Boyd County, Ky.; and the Miller No. 1 well, Wolfe County, Ky. These favorable oil-source rock correlations suggest a new petroleum system in the Appalachian basin that is characterized by a Conasauga Group source rock and Rome Formation and Conasauga Group reservoirs. This petroleum system probably extends along the Rome trough from eastern Kentucky to at least central West Virginia.

  20. The importance of intracrustal magmatic heat advection in large hot orogens: the Ediacaran-Cambrian ultrahigh-temperature domain of southern Madagascar.

    NASA Astrophysics Data System (ADS)

    Holder, R. M.; Hacker, B. R.

    2016-12-01

    Ultrahigh temperature metamorphism (UHTM) represents the thermal extremes of crustal metamorphism and is integral to our understanding of orogenic systems and continental evolution. The relative importance of advective and radiogenic heating in UHTM is often unclear, however, due to retrogression of UHT mineral assemblages and lack of robust chronology. We report the first observation of osumilite, pseudosections, feldspar thermometry, and monazite LASS U-Th-Pb chronology from the Ediacaran-Cambrian Anosyen domain of southern Madagascar to evaluate P-T-time paths and assess the relative importance of advective and radiogenic heating. Pseudosections of an osumilite-bearing assemblage, a garnet-orthopyroxene gneiss, and a garnet-spinel leucogneiss indicate peak conditions of 930-1010 C, 4-6 kbar; 900-950 C, 6-7 kbar; and 970-1000 C, 4.5-5.5 kbar, respectively. Feldspar thermometry indicates T > 915 ± 30 C. These conditions were reached along a low-P prograde path, as implied by cordierite and sillimanite inclusions in garnet. Monazite and zircon U/Th-Pb dating indicates that prograde metamorphism began 625 Ma and lasted 60 Myr. The timing of peak metamorphism is constrained to a 16 ± 2.5 Myr period between 566 ± 2 and 550 ± 1.5 Ma, by monazite inclusions in pseudomorphs after osumilite and monazite from a leucosome in the same outcrop. Peak T was achieved immediately following emplacement of voluminous charnockites (emplaced 1000-1100 C) and related magmas of the Anosyen Batholith. Crystallization of pegmatite dikes, leucosomes, and smaller plutons during cooling lasted from 550 to 510 Ma. This broad thermal history is also recorded by metamorphic monazite Eu/Eu*, which indicate progressive melt generation and extraction prior to 550 Ma followed by melt accumulation and crystallization after 550 Ma. Although the duration of prograde metamorphism is consistent with radiogenic heating models of large hot orogens, peak T was 100-200 C higher in southern Madagascar

  1. Fossilized embryos are widespread but the record is temporally and taxonomically biased

    USGS Publications Warehouse

    Donoghue, P.C.J.; Kouchinsky, A.; Waloszek, Dieter; Bengtson, S.; Dong, X.-P.; Val'Kov, A.K.; Cunningham, J.A.; Repetski, J.E.

    2006-01-01

    We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages. The temporal window within which the embryos and egg capsules are found is of relatively short duration; it ends in the Early Ordovician and is roughly coincident with that of typical "Orsten"-type faunas. The reduced occurrence of such fossils has been attributed to reducing levels of phosphate in marine waters during the early Paleozoic, but may also be owing to the increasing depth of sediment mixing by infaunal metazoans. Furthermore, most records younger than the earliest Cambrian are of a single kind - large eggs and embryos of the priapulid-like scalidophoran Markuelia. We explore alternative explanations for the low taxonomic diversity of embryos recovered thus far, including sampling, size, anatomy, ecology, and environment, concluding that the preponderance of Markuelia embryos is due to its precocious development of cuticle at an embryonic stage, predisposing it to preservation through action as a substrate on which microbially mediated precipitation of authigenic calcium phosphate may occur. The fossil record of embryos may be limited to a late Neoproterozoic to early Ordovician snapshot that is subject to dramatic systematic bias. Together, these biases must be considered seriously in attempts to use the fossil record to arbitrate between hypotheses of developmental and life history evolution implicated in the origin of metazoan clades. ?? 2006 Blackwell Publishing Ltd.

  2. Early mortality in multiple myeloma: the time-dependent impact of comorbidity: A population-based study in 621 real-life patients.

    PubMed

    Ríos-Tamayo, Rafael; Sáinz, Juan; Martínez-López, Joaquín; Puerta, José Manuel; Chang, Daysi-Yoe-Ling; Rodríguez, Teresa; Garrido, Pilar; de Veas, José Luís García; Romero, Antonio; Moratalla, Lucía; López-Fernández, Elisa; González, Pedro Antonio; Sánchez, María José; Jiménez-Moleón, José Juan; Jurado, Manuel; Lahuerta, Juan José

    2016-07-01

    Multiple myeloma is a heterogeneous disease with variable survival; this variability cannot be fully explained by the current systems of risk stratification. Early mortality remains a serious obstacle to further improve the trend toward increased survival demonstrated in recent years. However, the definition of early mortality is not standardized yet. Importantly, no study has focused on the impact of comorbidity on early mortality in multiple myeloma to date. Therefore, we analyzed the role of baseline comorbidity in a large population-based cohort of 621 real-life myeloma patients over a 31-year period. To evaluate early mortality, a sequential multivariate regression model at 2, 6, and 12 months from diagnosis was performed. It was demonstrated that comorbidity had an independent impact on early mortality, which is differential and time-dependent. Besides renal failure, respiratory disease at 2 months, liver disease at 6 months, and hepatitis virus C infection at 12 months, were, respectively, associated with early mortality, adjusting for other well-established prognostic factors. On the other hand, the long-term monitoring in our study points out a modest downward trend in early mortality over time. This is the first single institution population-based study aiming to assess the impact of comorbidity on early mortality in multiple myeloma. It is suggested that early mortality should be analyzed at three key time points (2, 6, and 12 months), in order to allow comparisons between studies. Comorbidity plays a critical role in the outcome of myeloma patients in terms of early mortality. Am. J. Hematol. 91:700-704, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  3. Viscous cosmology for early- and late-time universe

    NASA Astrophysics Data System (ADS)

    Brevik, Iver; Grøn, Øyvind; de Haro, Jaume; Odintsov, Sergei D.; Saridakis, Emmanuel N.

    From a hydrodynamicist’s point of view the inclusion of viscosity concepts in the macroscopic theory of the cosmic fluid would appear most natural, as an ideal fluid is after all an abstraction (exluding special cases such as superconductivity). Making use of modern observational results for the Hubble parameter plus standard Friedmann formalism, we may extrapolate the description of the universe back in time up to the inflationary era, or we may go to the opposite extreme and analyze the probable ultimate fate of the universe. In this review, we discuss a variety of topics in cosmology when it is enlarged in order to contain a bulk viscosity. Various forms of this viscosity, when expressed in terms of the fluid density or the Hubble parameter, are discussed. Furthermore, we consider homogeneous as well as inhomogeneous equations of state. We investigate viscous cosmology in the early universe, examining the viscosity effects on the various inflationary observables. Additionally, we study viscous cosmology in the late universe, containing current acceleration and the possible future singularities, and we investigate how one may even unify inflationary and late-time acceleration. Finally, we analyze the viscosity-induced crossing through the quintessence-phantom divide, we examine the realization of viscosity-driven cosmological bounces, and we briefly discuss how the Cardy-Verlinde formula is affected by viscosity.

  4. Selenium speciation in Lower Cambrian Se-enriched strata in South China and its geological implications

    NASA Astrophysics Data System (ADS)

    Fan, Haifeng; Wen, Hanjie; Hu, Ruizhong; Zhao, Hui

    2011-12-01

    To understand the impact of Selenium (Se) into the biogeochemical cycle and implications for palaeo-redox environment, a sequential extraction method was utilized for samples including black shales, cherts, a Ni-Mo-Se sulfide layer, K-bentonite and phosphorite from Lower Cambrian Se-enriched strata in southern China. Seven species (water-soluble, phosphate exchangeable, base-soluble, acetic acid-soluble, sulfide/selenide associated, residual Se) and different oxidation states (selenate Se(VI), selenite Se(IV), organic Se, Se (0) and mineral Se(-II)) were determinated in this study. We found that the Ni-Mo-Se sulfide layer contained a significantly greater amount of Se(-II) associated with sulfides/selenides than those in host black shales and cherts. Furthermore, a positive correlation between the degree of sulfidation of iron (DOS) and the percentage of the sulfide/selenide-associated Se(-II) was observed for samples, which suggests the proportion of sulfide/selenide-associated Se(-II) could serve as a proxy for palaeo-redox conditions. In addition, the higher percentage of Se(IV) in K-bentonite and phosphorite was found and possibly attributed to the adsorption of Se by clay minerals, iron hydroxide surfaces and organic particles. Based on the negative correlations between the percentage of Se(IV) and that of Se(-II) in samples, we propose that the K-bentonite has been altered under the acid oxic conditions, and the most of black shale (and cherts) and the Ni-Mo-Se sulfide layer formed under the anoxic and euxinic environments, respectively. Concerning Se accumulation in the Ni-Mo-Se sulfide layer, the major mechanism can be described by (1) biotic and abiotic adsorption and further dissimilatory reduction from oxidized Se(VI) and Se(IV) to Se(-II), through elemental Se, (2) contribution of hydrothermal fluid with mineral Se(-II).

  5. Return to work after early part-time sick leave due to musculoskeletal disorders: a randomized controlled trial.

    PubMed

    Viikari-Juntura, Eira; Kausto, Johanna; Shiri, Rahman; Kaila-Kangas, Leena; Takala, Esa-Pekka; Karppinen, Jaro; Miranda, Helena; Luukkonen, Ritva; Martimo, Kari-Pekka

    2012-03-01

    The purpose of this study was to assess the effects of early part-time sick leave on return to work (RTW) and sickness absence among patients with musculoskeletal disorders. A randomized controlled trial was conducted in six occupational health units of medium- and large-size enterprises. Patients aged 18-60 years with musculoskeletal disorders (N=63) unable to perform their regular work were randomly allocated to part- or full-time sick leave. In the former group, workload was reduced by restricting work time by about a half. Remaining work tasks were modified when necessary, as specified in a "fit note" from the physician. The main outcomes were time to return to regular work activities and sickness absence during 12-month follow-up. Time to RTW sustained for ≥4 weeks was shorter in the intervention group (median 12 versus 20 days, P=0.10). Hazard ratio of RTW adjusted for age was 1.60 [95% confidence interval (95% CI) 0.98-2.63] and 1.76 (95% CI 1.21-2.56) after further adjustment for pain interference with sleep and previous sickness absence at baseline. Total sickness absence during the 12-month follow-up was about 20% lower in the intervention than the control group. Compliance with the intervention was high with no discontinuations of part-time sick leave due to musculoskeletal reasons. Early part-time sick leave may provide a faster and more sustainable return to regular duties than full-time sick leave among patients with musculoskeletal disorders. This is the first study to show that work participation can be safely increased with early part-time sick leave.

  6. Synchronization of the astronomical time scales in the Early Toarcian: A link between anoxia, carbon-cycle perturbation, mass extinction and volcanism

    NASA Astrophysics Data System (ADS)

    Ait-Itto, Fatima-Zahra; Martinez, Mathieu; Price, Gregory D.; Ait Addi, Abdellah

    2018-07-01

    The Late Pliensbachian-Early Toarcian is a pivotal time in the Mesozoic era, marked by pronounced carbon-isotope excursions, biotic crises and major climatic and oceanographic changes. Here we present new high-resolution carbon-isotope and magnetic-susceptibility measurements from an expanded hemipelagic Late Pliensbachian-Early Toarcian section from the Middle Atlas Basin (Morocco). Our new astronomical calibration allows the construction of an orbital time scale based on the 100-kyr eccentricity cycle. The Early Toarcian Polymorphum Zone contains 10 to 10.5 repetitions of the 100-kyr eccentricity both in the carbon-isotope and the magnetic-susceptibility data, leading to an average duration of 1.00 ± 0.08 myr. We also show that the Late Pliensbachian-Early Toarcian global carbon-cycle perturbation has an average duration of 0.24 ± 0.02 myr. These durations are comparable to previous astrochronological time scales provided for this time interval in the most complete sections of the Tethyan area, and longer than what has been provided in condensed sections. Anchoring this framework on published radiometric ages and astrochronological time scales, we estimate that the carbon-cycle perturbation of the Late Pliensbachian-Early Toarcian corresponds with the early phase of the Karoo and Chonke Aike large igneous provinces. Likewise, our new age constraints confirm that the Toarcian oceanic anoxic event is synchronous to the main phase of the Ferrar volcanic activity. Thus, these successive and short phases of the volcanic activity may have been at the origin of the successive phases of the mass extinctions observed in marine biotas in the Pliensbachian and Toarcian times.

  7. The controversial “Cambrian” fossils of the Vindhyan are real but more than a billion years older

    PubMed Central

    Bengtson, Stefan; Belivanova, Veneta; Rasmussen, Birger; Whitehouse, Martin

    2009-01-01

    The age of the Vindhyan sedimentary basin in central India is controversial, because geochronology indicating early Proterozoic ages clashes with reports of Cambrian fossils. We present here an integrated paleontologic–geochronologic investigation to resolve this conundrum. New sampling of Lower Vindhyan phosphoritic stromatolitic dolomites from the northern flank of the Vindhyans confirms the presence of fossils most closely resembling those found elsewhere in Cambrian deposits: annulated tubes, embryo-like globules with polygonal surface pattern, and filamentous and coccoidal microbial fabrics similar to Girvanella and Renalcis. None of the fossils, however, can be ascribed to uniquely Cambrian or Ediacaran taxa. Indeed, the embryo-like globules are not interpreted as fossils at all but as former gas bubbles trapped in mucus-rich cyanobacterial mats. Direct dating of the same fossiliferous phosphorite yielded a Pb–Pb isochron of 1,650 ± 89 (2σ) million years ago, confirming the Paleoproterozoic age of the fossils. New U–Pb geochronology of zircons from tuffaceous mudrocks in the Lower Vindhyan Porcellanite Formation on the southern flank of the Vindhyans give comparable ages. The Vindhyan phosphorites provide a window of 3-dimensionally preserved Paleoproterozoic fossils resembling filamentous and coccoidal cyanobacteria and filamentous eukaryotic algae, as well as problematic forms. Like Neoproterozoic phosphorites a billion years later, the Vindhyan deposits offer important new insights into the nature and diversity of life, and in particular, the early evolution of multicellular eukaryotes. PMID:19416859

  8. Reaction Time is a Marker of Early Cognitive and Behavioral Alterations in Pure Cerebral Small Vessel Disease.

    PubMed

    Jouvent, Eric; Reyes, Sonia; De Guio, François; Chabriat, Hugues

    2015-01-01

    The assessment of early and subtle cognitive and behavioral effects of cerebral small vessel disease (SVD) requires specific and long-lasting evaluations performed by experienced neuropsychologists. Simpler tools would be helpful for daily clinical practice. To determine whether a simple reaction time task that lasts 5 minutes and can be performed without external supervision on any tablet or laptop can be used as a proxy of early cognitive and behavioral alterations in CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy), a monogenic form of pure SVD related to NOTCH3 mutations. Twenty-two genetically confirmed patients with CADASIL having preserved global cognitive abilities and without disability (MMSE >24 and modified Rankin's scale ≤1) were compared to 29 age-and-gender matched controls to determine group differences according to: 1) conventional neuropsychological and behavioral testing; 2) a computerized battery evaluating reaction time, processing speed, and executive functions. In a second step, correlations between reaction time and cognitive and behavioral alterations detected using both conventional and computerized testing were tested in patients. Reaction time was significantly higher in patients than in controls (mean in patients: 283 ms - in controls: 254 ms, p = 0.03). In patients, reaction time was significantly associated with conventional and chronometric tests of executive functions, working memory, and apathy. Reaction time obtained using a very simple task may serve as a proxy of early cognitive and behavioral alterations in SVD and could be easily used in daily clinical practice.

  9. The complete mitochondrial genome of Pauropus longiramus (Myriapoda: Pauropoda): implications on early diversification of the myriapods revealed from comparative analysis.

    PubMed

    Dong, Yan; Sun, Hongying; Guo, Hua; Pan, Da; Qian, Changyuan; Hao, Sijing; Zhou, Kaiya

    2012-08-15

    Myriapods are among the earliest arthropods and may have evolved to become part of the terrestrial biota more than 400 million years ago. A noticeable lack of mitochondrial genome data from Pauropoda hampers phylogenetic and evolutionary studies within the subphylum Myriapoda. We sequenced the first complete mitochondrial genome of a microscopic pauropod, Pauropus longiramus (Arthropoda: Myriapoda), and conducted comprehensive mitogenomic analyses across the Myriapoda. The pauropod mitochondrial genome is a circular molecule of 14,487 bp long and contains the entire set of thirty-seven genes. Frequent intergenic overlaps occurred between adjacent tRNAs, and between tRNA and protein-coding genes. This is the first example of a mitochondrial genome with multiple intergenic overlaps and reveals a strategy for arthropods to effectively compact the mitochondrial genome by overlapping and truncating tRNA genes with neighbor genes, instead of only truncating tRNAs. Phylogenetic analyses based on protein-coding genes provide strong evidence that the sister group of Pauropoda is Symphyla. Additionally, approximately unbiased (AU) tests strongly support the Progoneata and confirm the basal position of Chilopoda in Myriapoda. This study provides an estimation of myriapod origins around 555 Ma (95% CI: 444-704 Ma) and this date is comparable with that of the Cambrian explosion and candidate myriapod-like fossils. A new time-scale suggests that deep radiations during early myriapod diversification occurred at least three times, not once as previously proposed. A Carboniferous origin of pauropods is congruent with the idea that these taxa are derived, rather than basal, progoneatans. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Methods for Detecting Early Warnings of Critical Transitions in Time Series Illustrated Using Simulated Ecological Data

    PubMed Central

    Dakos, Vasilis; Carpenter, Stephen R.; Brock, William A.; Ellison, Aaron M.; Guttal, Vishwesha; Ives, Anthony R.; Kéfi, Sonia; Livina, Valerie; Seekell, David A.; van Nes, Egbert H.; Scheffer, Marten

    2012-01-01

    Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called ‘early warning signals’, and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data. PMID:22815897

  11. Bullying Behavior, Parents' Work Hours and Early Adolescents' Perceptions of Time Spent with Parents

    ERIC Educational Resources Information Center

    Christie-Mizell, C. Andre; Keil, Jacqueline M.; Laske, Mary Therese; Stewart, Jennifer

    2011-01-01

    This research investigates the relationships among bullying behavior, mother's and father's work hours, and early adolescents' perceptions of whether they spend sufficient time with their parents. In cross-sectional models, we find maternal work hours are modestly associated with increases in bullying behavior. However, in more rigorous change…

  12. A molecular palaeobiological exploration of arthropod terrestrialization

    PubMed Central

    Carton, Robert; Edgecombe, Gregory D.

    2016-01-01

    Understanding animal terrestrialization, the process through which animals colonized the land, is crucial to clarify extant biodiversity and biological adaptation. Arthropoda (insects, spiders, centipedes and their allies) represent the largest majority of terrestrial biodiversity. Here we implemented a molecular palaeobiological approach, merging molecular and fossil evidence, to elucidate the deepest history of the terrestrial arthropods. We focused on the three independent, Palaeozoic arthropod terrestrialization events (those of Myriapoda, Hexapoda and Arachnida) and showed that a marine route to the colonization of land is the most likely scenario. Molecular clock analyses confirmed an origin for the three terrestrial lineages bracketed between the Cambrian and the Silurian. While molecular divergence times for Arachnida are consistent with the fossil record, Myriapoda are inferred to have colonized land earlier, substantially predating trace or body fossil evidence. An estimated origin of myriapods by the Early Cambrian precedes the appearance of embryophytes and perhaps even terrestrial fungi, raising the possibility that terrestrialization had independent origins in crown-group myriapod lineages, consistent with morphological arguments for convergence in tracheal systems. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325830

  13. A diploblastic radiate animal at the dawn of cambrian diversification with a simple body plan: distinct from Cnidaria?

    PubMed

    Yasui, Kinya; Reimer, James D; Liu, Yunhuan; Yao, Xiaoyong; Kubo, Daisuke; Shu, Degan; Li, Yong

    2013-01-01

    Microfossils of the genus Punctatus include developmental stages such as blastula, gastrula, and hatchlings, and represent the most complete developmental sequence of animals available from the earliest Cambrian. Despite the extremely well-preserved specimens, the evolutionary position of Punctatus has relied only on their conical remains and they have been tentatively assigned to cnidarians. We present a new interpretation of the Punctatus body plan based on the developmental reconstruction aided by recent advances in developmental biology. Punctatus developed from a rather large egg, gastrulated in a mode of invagination from a coeloblastura, and then formed a mouth directly from the blastopore. Spiny benthic hatchlings were distinguishable from swimming or crawling ciliate larvae found in cnidarians and sponges. A mouth appeared at the perihatching embryonic stage and was renewed periodically during growth, and old mouths transformed into the body wall, thus elongating the body. Growing animals retained a small blind gut in a large body cavity without partitioning by septa and did not form tentacles, pedal discs or holdfasts externally. A growth center at the oral pole was sufficient for body patterning throughout life, and the body patterning did not show any bias from radial symmetry. Contrary to proposed cnidarian affinity, the Punctatus body plan has basic differences from that of cnidarians, especially concerning a spacious body cavity separating ectoderm from endoderm. The lack of many basic cnidarian characters in the body patterning of Punctatus leads us to consider its own taxonomic group, potentially outside of Cnidaria.

  14. Extent and architecture of major fault systems between northern Victoria Land and the eastern margin of the Wilkes Subglacial Basin (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Armadillo, E.; Ferraccioli, F.; Balbi, P.; Bozzo, E.

    2013-12-01

    Terrane bounding and intra-terrane faults of the Ross Orogen in East Antarctica are linked to several phases of Cambrian to Ordovician age subduction and accretion along the active paleo-Pacific margin of Gondwana. Here we compile and analyse new enhanced aeromagnetic anomaly images over the Northern Victoria Land (NVL) segment of the Ross Orogen and the eastern margin of the Wilkes Subglacial Basin (WSB) that help constrain the extent and structural architecture of these fault systems and enable us re-assess their tectonic evolution. Long-wavelength magnetic lows and residual Bouguer gravity highs are modelled as several-km thick inverted sedimentary basins of early Cambrian(?) age. Tectonic inversion occurred along major thrust faults during the late stages of the Ross Orogen, forming a major high-grade pop-up structure within the central Wilson Terrane, flanked by lower grade rocks. The Prince Albert Fault System can now be recongnised as being located to the west of the Exiles Thrust fault system rather than representing its southern continuation. Relatively thin sheets of mylonitic sheared granitoids and possible ultramafic lenses are associated with the late-Ross (ca 480 Ma) Exiles Thrust fault system, while significantly larger and thicker batholiths were emplaced along the Prince Albert Fault System. Recent zircon U-Pb dating over small exposures of gabbro-diorites within the Prince Albert Mountains to the south lead us to propose that this part of the magmatic arc was emplaced during an earlier phase of subduction (~520 Ma or older?), compared to the late-Ross intrusions to the east. Whether the Prince Albert Fault System was indeed a major cryptic suture in early Cambrian times (Ferraccioli et al., 2002, GRL) remains speculative, but possible. Our aeromagnetic interpretation leads us to conclude that these inherited terrane bounding and intra-terrane fault systems of the Ross Orogen exerted a key influence on Cenozoic tectonic blocks and faults of the

  15. Inside stories: maternal representations of first time mothers from pre-pregnancy to early pregnancy.

    PubMed

    Hopkins, Julia; Clarke, David; Cross, Wendy

    2014-03-01

    According to the psychoanalytical literature, it is during pregnancy that maternal representations of the mother-infant relationship become activated. Midwives who are engaged with the mother and the baby have not drawn upon this concept in their practice. In order for this to happen, it is important to understand better the nature of maternal representations and when they are activated from empirical studies. The research question is: what are the maternal representations of a group of first time mothers from pre-pregnancy, early pregnancy and to the first ultrasound. A narrative approach was used to gain insight into the maternal representations of first time pregnant womens' account of their representations. The analysis method was based on thematic approach. Fifteen women aged between 23 and 38 years. A midwives clinic attached to a tertiary hospital in Melbourne, Australia. First-time pregnant women's maternal representations were activated when a woman begins to plan her pregnancy ('the time is right'), again at the onset of physical changes to her body as a result of conception ('my body is changing'), and at the first early ultrasound at around twelve weeks ('it' is a real baby). Maternal representations are important for the midwife and pregnant women because this concept provides another understanding in relation to the psychological dimension of pregnancy. Copyright © 2013 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.

  16. Parental Monitoring during Early Adolescence Deters Adolescent Sexual Initiation: Discrete-Time Survival Mixture Analysis

    ERIC Educational Resources Information Center

    Huang, David Y. C.; Murphy, Debra A.; Hser, Yih-Ing

    2011-01-01

    We used discrete-time survival mixture modeling to examine 5,305 adolescents from the 1997 National Longitudinal Survey of Youth regarding the impact of parental monitoring during early adolescence (ages 14-16) on initiation of sexual intercourse and problem behavior engagement (ages 14-23). Four distinctive parental-monitoring groups were…

  17. A- and I-type metagranites from the North Shahrekord Metamorphic Complex, Iran: Evidence for Early Paleozoic post-collisional magmatism

    NASA Astrophysics Data System (ADS)

    Badr, Afsaneh; Davoudian, Ali Reza; Shabanian, Nahid; Azizi, Hossein; Asahara, Yoshihiro; Neubauer, Franz; Dong, Yunpeng; Yamamoto, Koshi

    2018-02-01

    The North Shahrekord Metamorphic Complex (NSMC) of the central Sanandaj-Sirjan Zone (SaSZ) consists of metagranitoid bodies, which were metamorphosed within high pressure-low temperature conditions. Whole rock chemistry shows relatively high amounts of SiO2 (65-77 wt%) and Al2O3 (12-15 wt%), low amounts of Nb, P, Sr, Ti, a high ratio of Ga/Al (4-9) and a negative Eu anomaly. The chemical compositions of metagranites are reasonably similar to A- and I-type granites. U-Pb zircon ages of three samples of metagranites indicate that crystallization of the granites occurred at 521.6 ± 9.1 to 513.5 ± 8.5 Ma, Middle Cambrian. The initial 87Sr/86Sr and 143Nd/144Nd ratios of samples vary from 0.7057-0.7239 and 0.511801-0.511890, respectively. High initial 87Sr/86Sr ratios and low εNd(t) values (- 3.39 to - 1.07) associated with high ratios of 206Pb/204Pb(t) = 17.8557-18.8045, 207Pb/204Pb(t) = 15.6721-15.7220, and 208Pb/204Pb(t) = 37.7490-38.4468 infer a significant contribution of continental crust in generating the source magma of the metagranite bodies. The results reveal that the metagranites were mainly produced through mixing of basaltic melts with components similar to metasedimentary sources. The new results show that crystallization of the metagranites occurred in Early Paleozoic times and much earlier than break-up and drifting of the SaSZ from the Arabian plate, suggesting that the metagranites were mainly produced in the western Iran after the closure of the Proto-Tethys Ocean. This model is consistent with the previously suggested models for formation of an Early Paleozoic granitoid belt along the northern rim of Gondwana.

  18. A comparative assessment of the role of anoxia during the Cambrian SPICE event

    NASA Astrophysics Data System (ADS)

    LeRoy, M.; Gill, B. C.; Sperling, E. A.

    2017-12-01

    The Cambrian SPICE (Steptoean Positive Carbon Isotope Excursion) is recognized as a major oceanographic event recorded in globally-distributed stratigraphic sections as positive isotopic excursions in marine carbonates (δ13Ccarb), organic matter (δ13Corg), sulfate (δ34SCAS) and pyrite (δ34Spy). A proposed mechanism for these observed isotopic trends is that a transient increase in the areal extent of anoxic conditions within the oceans fostered enhanced burial of organic carbon and pyrite. However, direct sedimentary (e.g., abundant black shale) and geochemical (e.g., redox proxy) evidence for such a shift is scant. While the antiquity of this event is likely responsible for loss of much of this evidence, through destruction by tectonic processes, a number of stratigraphic successions suitable for investigating this hypothesis exist. Here we explore the relationship between anoxia and the SPICE using previously published and novel data generated from core material from three sedimentary basins distributed along the margins of the Iapetus Ocean. The units studied are: the Nolichucky Formation of eastern Laurentia, the Alum Shale of Baltica, and the Outwoods Shale of Avalonia. Our iron speciation data indicate consistently oxic conditions prior to the SPICE along Laurentia, while Avalonia was oxic with intervals of anoxia, and Baltica was persistently anoxic. With the initiation of the SPICE, anoxic conditions intensified in Laurentia and Avalonia and continued to persist in Baltica. This redox shift was coupled with a sharp rise in δ34Spy at all three locations. Average total organic carbon (TOC) showed little change in relation to the SPICE at the Laurentia location ( 0.15 wt%), but showed an increase in conjunction with the excursion in both the Avalonia ( 1 to 1.5 wt%) and Baltica ( 8 to 12 wt%) sections. Large differences in nutrient availability and sedimentation rates are likely responsible for the between-site disparity in TOC, while overall, anoxia

  19. How one might miss early warning signals of critical transitions in time series data: A systematic study of two major currency pairs

    PubMed Central

    Ciamarra, Massimo Pica; Cheong, Siew Ann

    2018-01-01

    There is growing interest in the use of critical slowing down and critical fluctuations as early warning signals for critical transitions in different complex systems. However, while some studies found them effective, others found the opposite. In this paper, we investigated why this might be so, by testing three commonly used indicators: lag-1 autocorrelation, variance, and low-frequency power spectrum at anticipating critical transitions in the very-high-frequency time series data of the Australian Dollar-Japanese Yen and Swiss Franc-Japanese Yen exchange rates. Besides testing rising trends in these indicators at a strict level of confidence using the Kendall-tau test, we also required statistically significant early warning signals to be concurrent in the three indicators, which must rise to appreciable values. We then found for our data set the optimum parameters for discovering critical transitions, and showed that the set of critical transitions found is generally insensitive to variations in the parameters. Suspecting that negative results in the literature are the results of low data frequencies, we created time series with time intervals over three orders of magnitude from the raw data, and tested them for early warning signals. Early warning signals can be reliably found only if the time interval of the data is shorter than the time scale of critical transitions in our complex system of interest. Finally, we compared the set of time windows with statistically significant early warning signals with the set of time windows followed by large movements, to conclude that the early warning signals indeed provide reliable information on impending critical transitions. This reliability becomes more compelling statistically the more events we test. PMID:29538373

  20. How one might miss early warning signals of critical transitions in time series data: A systematic study of two major currency pairs.

    PubMed

    Wen, Haoyu; Ciamarra, Massimo Pica; Cheong, Siew Ann

    2018-01-01

    There is growing interest in the use of critical slowing down and critical fluctuations as early warning signals for critical transitions in different complex systems. However, while some studies found them effective, others found the opposite. In this paper, we investigated why this might be so, by testing three commonly used indicators: lag-1 autocorrelation, variance, and low-frequency power spectrum at anticipating critical transitions in the very-high-frequency time series data of the Australian Dollar-Japanese Yen and Swiss Franc-Japanese Yen exchange rates. Besides testing rising trends in these indicators at a strict level of confidence using the Kendall-tau test, we also required statistically significant early warning signals to be concurrent in the three indicators, which must rise to appreciable values. We then found for our data set the optimum parameters for discovering critical transitions, and showed that the set of critical transitions found is generally insensitive to variations in the parameters. Suspecting that negative results in the literature are the results of low data frequencies, we created time series with time intervals over three orders of magnitude from the raw data, and tested them for early warning signals. Early warning signals can be reliably found only if the time interval of the data is shorter than the time scale of critical transitions in our complex system of interest. Finally, we compared the set of time windows with statistically significant early warning signals with the set of time windows followed by large movements, to conclude that the early warning signals indeed provide reliable information on impending critical transitions. This reliability becomes more compelling statistically the more events we test.

  1. Childhood adversities and socioeconomic position as predictors of leisure-time physical inactivity in early adulthood.

    PubMed

    Kestilä, Laura; Mäki-Opas, Tomi; Kunst, Anton E; Borodulin, Katja; Rahkonen, Ossi; Prättälä, Ritva

    2015-02-01

    Limited knowledge exists on how childhood social, health-related and economic circumstances predict adult physical inactivity. Our aim was a) to examine how various childhood adversities and living conditions predict leisure-time physical inactivity in early adulthood and b) to find out whether these associations are mediated through the respondent's own education. Young adults aged 18-29 were used from the Health 2000 Study of the Finnish. The cross-sectional data were based on interviews and questionnaires including retrospective information on childhood circumstances. The analyses were carried out on 68% of the original sample (N = 1894). The outcome measure was leisure-time physical inactivity. Only a few of the 11 childhood adversities were related with physical activity in early adulthood. Having been bullied at school was associated with physical inactivity independently of the other childhood circumstances and the respondent's own education. Low parental education predicted leisure-time physical inactivity in men and the association was mediated by the respondent's own education. Respondents with only primary or vocational education were more likely to be physically inactive during leisure-time compared with those with secondary or higher education. There is some evidence that few specific childhood adversities, especially bullying at school, have long-lasting effects on physical activity levels.

  2. Optimal timing of early versus delayed adjuvant radiotherapy following radical prostatectomy for locally advanced prostate cancer.

    PubMed

    Kowalczyk, Keith J; Gu, Xiangmei; Nguyen, Paul L; Lipsitz, Stuart R; Trinh, Quoc-Dien; Lynch, John H; Collins, Sean P; Hu, Jim C

    2014-04-01

    Although post-radical prostatectomy (RP) adjuvant radiation therapy (ART) benefits disease that is staged as pT3 or higher, the optimal ART timing remains unknown. Our objective is to characterize the outcomes and optimal timing of early vs. delayed ART. From the Surveillance, Epidemiology and End Results-Medicare data from 1995 to 2007, we identified 963 men with pT3N0 disease receiving early (<4 mo after RP, n = 419) vs. delayed (4-12 mo after RP, n = 544) ART after RP. Utilizing propensity score methods, we compared overall mortality, prostate cancer-specific mortality (PCSM), bone-related events (BRE), salvage hormonal therapy utilization, and intervention for urethral stricture. We then used the maximal statistic approach to determine at what time post-RP ART had the most significant effect on outcomes of interest in men with pT3N0 disease. When compared with delayed ART in men with pT3 disease, early ART was associated with improved PCSM (0.47 vs. 1.02 events per 100 person-years; P = 0.038) and less salvage hormonal therapy (2.88 vs. 4.59 events per 100 person-years; P = 0.001). Delaying ART beyond 5 months is associated with worse PCSM (hazard ratio [HR] 2.3; P = 0.020), beyond 3 months is associated with more BRE (HR 1.6; P = 0.025), and beyond 4 months is associated higher rates of salvage hormonal therapy (HR 1.6; P = 0.002). ART performed after 9 months was associated with fewer urethral strictures (HR 0.6; P = 0.042). Initiating ART less than 5 months after RP for pT3 is associated with improved PCSM. Early ART is also associated with fewer BRE and less use of salvage hormonal therapy if administered earlier than 3 and 4 months after RP, respectively. However, ART administered later than 9 months after RP is associated with fewer urethral strictures. Our population-based findings complement randomized trials designed with fixed ART timing. © 2013 Published by Elsevier Inc.

  3. Seeking new potential in the early-late Permian Gharif Play, West Central Oman

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guit, F.; Al-Lawati, M.; Nederlof, P.

    1995-08-01

    West Central Oman is a relatively underexplored area where the hydrocarbons found to date occur mainly within the Early-Late Permian Gharif Formation. Structural definition of the low relief closures is hampered by seismic velocity variations caused by dune terrain. Recent exploration activity resulted in several Gharif discoveries, but highlighted reservoir distribution problems. The Gharif Formation, which consists of fluvio-marine sediments, conformably overlies the glacio-lacustine sediments of the Early Permian Al Khlata Formation. It is overlain by shallow marine carbonates of the Late Permian Khuff Formation, the main regional seal. The area is located distally from the main sediment sources tomore » the east. Reservoir development and lateral continuity are seen as the main risk. Most reservoirs are beyond seismic resolution, only the stacked sandstones of the incised valley fills could provide sufficient acoustic contrast to be recognized on seismic. Geochemical typing indicates that the hydrocarbons in the Gharif can be grouped in two main families: the Huqf and Q-hydrocarbons, which are believed to originate from Cambrian to Precambrian source rocks. Although the two hydrocarbon families are sometimes found in one well, they have very different spatial distributions. The Q-oils form continuous strings of accumulations below the main regional seal, whereas the Huqf hydrocarbons occur scattered throughout the area. Mixed accumulations are found where cross-faults or salt domes intercept a Q-oil fairway. Future exploration activities will be guided by refined sedimentological, stratigraphical and hydrocarbon migration models and by the continued efforts to recognize incised valley fills on seismic.« less

  4. Early relapse after autologous hematopoietic cell transplantation remains a poor prognostic factor in multiple myeloma but outcomes have improved over time.

    PubMed

    Kumar, S K; Dispenzieri, A; Fraser, R; Mingwei, F; Akpek, G; Cornell, R; Kharfan-Dabaja, M; Freytes, C; Hashmi, S; Hildebrandt, G; Holmberg, L; Kyle, R; Lazarus, H; Lee, C; Mikhael, J; Nishihori, T; Tay, J; Usmani, S; Vesole, D; Vij, R; Wirk, B; Krishnan, A; Gasparetto, C; Mark, T; Nieto, Y; Hari, P; D'Souza, A

    2018-04-01

    Duration of initial disease response remains a strong prognostic factor in multiple myeloma (MM) particularly for upfront autologous hematopoietic cell transplant (AHCT) recipients. We hypothesized that new drug classes and combinations employed prior to AHCT as well as after post-AHCT relapse may have changed the natural history of MM in this population. We analyzed the Center for International Blood and Marrow Transplant Research database to track overall survival (OS) of MM patients receiving single AHCT within 12 months after diagnosis (N=3256) and relapsing early post-AHCT (<24 months), and to identify factors predicting for early vs late relapses (24-48 months post-AHCT). Over three periods (2001-2004, 2005-2008, 2009-2013), patient characteristics were balanced except for lower proportion of Stage III, higher likelihood of one induction therapy with novel triplets and higher rates of planned post-AHCT maintenance over time. The proportion of patients relapsing early was stable over time at 35-38%. Factors reducing risk of early relapse included lower stage, chemosensitivity, transplant after 2008 and post-AHCT maintenance. Shorter post-relapse OS was associated with early relapse, IgA MM, Karnofsky <90, stage III, >1 line of induction and lack of maintenance. Post-AHCT early relapse remains a poor prognostic factor, even though outcomes have improved over time.

  5. Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution.

    PubMed

    Oji, Tatsuo; Dornbos, Stephen Q; Yada, Keigo; Hasegawa, Hitoshi; Gonchigdorj, Sersmaa; Mochizuki, Takafumi; Takayanagi, Hideko; Iryu, Yasufumi

    2018-02-01

    The Cambrian radiation of complex animals includes a dramatic increase in the depth and intensity of bioturbation in seafloor sediment known as the 'agronomic revolution'. This bioturbation transition was coupled with a shift in dominant trace fossil style from horizontal surficial traces in the late Precambrian to vertically penetrative trace fossils in the Cambrian. Here we show the existence of the first vertically penetrative trace fossils from the latest Ediacaran: dense occurrences of the U-shaped trace fossil Arenicolites from late Precambrian marine carbonates of Western Mongolia. Their Ediacaran age is established through stable carbon isotope chemostratigraphy and their occurrence stratigraphically below the first appearance of the trace fossil Treptichnus pedum . These Arenicolites are large in diameter, penetrate down to at least 4 cm into the sediment, and were presumably formed by the activity of bilaterian animals. They are preserved commonly as paired circular openings on bedding planes with maximum diameters ranging up to almost 1 cm, and as U- and J-shaped tubes in vertical sections of beds. Discovery of these complex penetrative trace fossils demonstrates that the agronomic revolution started earlier than previously considered.

  6. Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution

    PubMed Central

    Dornbos, Stephen Q.; Yada, Keigo; Hasegawa, Hitoshi; Gonchigdorj, Sersmaa; Mochizuki, Takafumi; Takayanagi, Hideko; Iryu, Yasufumi

    2018-01-01

    The Cambrian radiation of complex animals includes a dramatic increase in the depth and intensity of bioturbation in seafloor sediment known as the ‘agronomic revolution’. This bioturbation transition was coupled with a shift in dominant trace fossil style from horizontal surficial traces in the late Precambrian to vertically penetrative trace fossils in the Cambrian. Here we show the existence of the first vertically penetrative trace fossils from the latest Ediacaran: dense occurrences of the U-shaped trace fossil Arenicolites from late Precambrian marine carbonates of Western Mongolia. Their Ediacaran age is established through stable carbon isotope chemostratigraphy and their occurrence stratigraphically below the first appearance of the trace fossil Treptichnus pedum. These Arenicolites are large in diameter, penetrate down to at least 4 cm into the sediment, and were presumably formed by the activity of bilaterian animals. They are preserved commonly as paired circular openings on bedding planes with maximum diameters ranging up to almost 1 cm, and as U- and J-shaped tubes in vertical sections of beds. Discovery of these complex penetrative trace fossils demonstrates that the agronomic revolution started earlier than previously considered. PMID:29515908

  7. Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution

    NASA Astrophysics Data System (ADS)

    Oji, Tatsuo; Dornbos, Stephen Q.; Yada, Keigo; Hasegawa, Hitoshi; Gonchigdorj, Sersmaa; Mochizuki, Takafumi; Takayanagi, Hideko; Iryu, Yasufumi

    2018-02-01

    The Cambrian radiation of complex animals includes a dramatic increase in the depth and intensity of bioturbation in seafloor sediment known as the `agronomic revolution'. This bioturbation transition was coupled with a shift in dominant trace fossil style from horizontal surficial traces in the late Precambrian to vertically penetrative trace fossils in the Cambrian. Here we show the existence of the first vertically penetrative trace fossils from the latest Ediacaran: dense occurrences of the U-shaped trace fossil Arenicolites from late Precambrian marine carbonates of Western Mongolia. Their Ediacaran age is established through stable carbon isotope chemostratigraphy and their occurrence stratigraphically below the first appearance of the trace fossil Treptichnus pedum. These Arenicolites are large in diameter, penetrate down to at least 4 cm into the sediment, and were presumably formed by the activity of bilaterian animals. They are preserved commonly as paired circular openings on bedding planes with maximum diameters ranging up to almost 1 cm, and as U- and J-shaped tubes in vertical sections of beds. Discovery of these complex penetrative trace fossils demonstrates that the agronomic revolution started earlier than previously considered.

  8. Peer substance use as a mediator between early pubertal timing and adolescent substance use: longitudinal associations and moderating effect of maltreatment.

    PubMed

    Negriff, Sonya; Trickett, Penelope K

    2012-11-01

    Early pubertal timing has received considerable empirical support as a risk for adolescent substance use. However, few studies have examined the mediators linking these variables. Therefore, the aims of this study were (1) to examine peer substance use as a mediator between pubertal timing and adolescent substance use longitudinally and (2) to test gender and maltreatment experience as moderators of the mediational model. Data were obtained from time 1, 2, and 3 of a longitudinal study of maltreatment and development. At time 1 the sample was comprised of 303 maltreated and 151 comparison children aged 9-13 years (213 females and 241 males). Longitudinal mediation was tested using structural equation modeling and moderating effects were tested using multiple group analysis. Peer substance use mediated the relationship between early pubertal timing and later adolescent substance use for the total sample. Moderation analyses indicated this significant indirect effect did not differ for males and females. However, it did differ for maltreated versus comparison adolescents with the mediational effect only remaining significant for the comparison group. This is one of the first studies to examine peer substance use as a mediator of pubertal timing and adolescent substance use using a longitudinal design. Early maturing males are at equal risk to early maturing females for interacting with peers that may draw them into substance use. Additionally, the findings indicate that while peers are mediators for comparison adolescents a different mechanism may link early puberty to substance use for maltreated adolescents. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  9. The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago

    PubMed Central

    Feinberg, Todd E.; Mallatt, Jon

    2013-01-01

    Vertebrates evolved in the Cambrian Period before 520 million years ago, but we do not know when or how consciousness arose in the history of the vertebrate brain. Here we propose multiple levels of isomorphic or somatotopic neural representations as an objective marker for sensory consciousness. All extant vertebrates have these, so we deduce that consciousness extends back to the group's origin. The first conscious sense may have been vision. Then vision, coupled with additional sensory systems derived from ectodermal placodes and neural crest, transformed primitive reflexive systems into image forming brains that map and perceive the external world and the body's interior. We posit that the minimum requirement for sensory consciousness and qualia is a brain including a forebrain (but not necessarily a developed cerebral cortex/pallium), midbrain, and hindbrain. This brain must also have (1) hierarchical systems of intercommunicating, isomorphically organized, processing nuclei that extensively integrate the different senses into representations that emerge in upper levels of the neural hierarchy; and (2) a widespread reticular formation that integrates the sensory inputs and contributes to attention, awareness, and neural synchronization. We propose a two-step evolutionary history, in which the optic tectum was the original center of multi-sensory conscious perception (as in fish and amphibians: step 1), followed by a gradual shift of this center to the dorsal pallium or its cerebral cortex (in mammals, reptiles, birds: step 2). We address objections to the hypothesis and call for more studies of fish and amphibians. In our view, the lamprey has all the neural requisites and is likely the simplest extant vertebrate with sensory consciousness and qualia. Genes that pattern the proposed elements of consciousness (isomorphism, neural crest, placodes) have been identified in all vertebrates. Thus, consciousness is in the genes, some of which are already known. PMID

  10. The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago.

    PubMed

    Feinberg, Todd E; Mallatt, Jon

    2013-01-01

    Vertebrates evolved in the Cambrian Period before 520 million years ago, but we do not know when or how consciousness arose in the history of the vertebrate brain. Here we propose multiple levels of isomorphic or somatotopic neural representations as an objective marker for sensory consciousness. All extant vertebrates have these, so we deduce that consciousness extends back to the group's origin. The first conscious sense may have been vision. Then vision, coupled with additional sensory systems derived from ectodermal placodes and neural crest, transformed primitive reflexive systems into image forming brains that map and perceive the external world and the body's interior. We posit that the minimum requirement for sensory consciousness and qualia is a brain including a forebrain (but not necessarily a developed cerebral cortex/pallium), midbrain, and hindbrain. This brain must also have (1) hierarchical systems of intercommunicating, isomorphically organized, processing nuclei that extensively integrate the different senses into representations that emerge in upper levels of the neural hierarchy; and (2) a widespread reticular formation that integrates the sensory inputs and contributes to attention, awareness, and neural synchronization. We propose a two-step evolutionary history, in which the optic tectum was the original center of multi-sensory conscious perception (as in fish and amphibians: step 1), followed by a gradual shift of this center to the dorsal pallium or its cerebral cortex (in mammals, reptiles, birds: step 2). We address objections to the hypothesis and call for more studies of fish and amphibians. In our view, the lamprey has all the neural requisites and is likely the simplest extant vertebrate with sensory consciousness and qualia. Genes that pattern the proposed elements of consciousness (isomorphism, neural crest, placodes) have been identified in all vertebrates. Thus, consciousness is in the genes, some of which are already known.

  11. Occipital MEG Activity in the Early Time Range (<300 ms) Predicts Graded Changes in Perceptual Consciousness.

    PubMed

    Andersen, Lau M; Pedersen, Michael N; Sandberg, Kristian; Overgaard, Morten

    2016-06-01

    Two electrophysiological components have been extensively investigated as candidate neural correlates of perceptual consciousness: An early, occipitally realized component occurring 130-320 ms after stimulus onset and a late, frontally realized component occurring 320-510 ms after stimulus onset. Recent studies have suggested that the late component may not be uniquely related to perceptual consciousness, but also to sensory expectations, task associations, and selective attention. We conducted a magnetoencephalographic study; using multivariate analysis, we compared classification accuracies when decoding perceptual consciousness from the 2 components using sources from occipital and frontal lobes. We found that occipital sources during the early time range were significantly more accurate in decoding perceptual consciousness than frontal sources during both the early and late time ranges. These results are the first of its kind where the predictive values of the 2 components are quantitatively compared, and they provide further evidence for the primary importance of occipital sources in realizing perceptual consciousness. The results have important consequences for current theories of perceptual consciousness, especially theories emphasizing the role of frontal sources. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  12. Wormholes versus black holes: quasinormal ringing at early and late times

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Konoplya, R.A.; Zhidenko, A., E-mail: roman.konoplya@uni-tuebingen.de, E-mail: olexandr.zhydenko@ufabc.edu.br

    Recently it has been argued that the phantom thin-shell wormholes matched with the Schwarzschild space-time near the Schwarzschild radius ring like Schwarzschild black holes at early times, but differently at late times [1]. Here we consider perturbations of the wormhole which was constructed without thin-shells: the Bronnikov-Ellis wormhole supported by the phantom matter and electromagnetic field. This wormhole solution is known to be stable under specific equation of state of the phantom matter. We show that if one does not use the above thin-shell matching, the wormhole, depending on the values of its parameters, either rings as the black holemore » at all times or rings differently also at all times . The wormhole's spectrum, investigated here, posses a number of distinctive features. In the final part we have considered general properties of scattering around arbitrary rotating traversable wormholes. We have found that symmetric and non-symmetric (with respect to the throat) wormholes are qualitatively different in this respect: first, superradiance is allowed only if for those non-symmetric wormholes for which the asymptotic values of the rotation parameters are different on both sides from the throat. Second, the symmetric wormholes cannot mimic effectively the ringing of a black hole at a few various dominant multipoles at the same time, so that the future observations of various events should easily tell the symmetric wormhole from a black hole.« less

  13. Integrating real-time subsurface hydrologic monitoring with empirical rainfall thresholds to improve landslide early warning

    USGS Publications Warehouse

    Mirus, Benjamin B.; Becker, Rachel E.; Baum, Rex L.; Smith, Joel B.

    2018-01-01

    Early warning for rainfall-induced shallow landsliding can help reduce fatalities and economic losses. Although these commonly occurring landslides are typically triggered by subsurface hydrological processes, most early warning criteria rely exclusively on empirical rainfall thresholds and other indirect proxies for subsurface wetness. We explore the utility of explicitly accounting for antecedent wetness by integrating real-time subsurface hydrologic measurements into landslide early warning criteria. Our efforts build on previous progress with rainfall thresholds, monitoring, and numerical modeling along the landslide-prone railway corridor between Everett and Seattle, Washington, USA. We propose a modification to a previously established recent versus antecedent (RA) cumulative rainfall thresholds by replacing the antecedent 15-day rainfall component with an average saturation observed over the same timeframe. We calculate this antecedent saturation with real-time telemetered measurements from five volumetric water content probes installed in the shallow subsurface within a steep vegetated hillslope. Our hybrid rainfall versus saturation (RS) threshold still relies on the same recent 3-day rainfall component as the existing RA thresholds, to facilitate ready integration with quantitative precipitation forecasts. During the 2015–2017 monitoring period, this RS hybrid approach has an increase of true positives and a decrease of false positives and false negatives relative to the previous RA rainfall-only thresholds. We also demonstrate that alternative hybrid threshold formats could be even more accurate, which suggests that further development and testing during future landslide seasons is needed. The positive results confirm that accounting for antecedent wetness conditions with direct subsurface hydrologic measurements can improve thresholds for alert systems and early warning of rainfall-induced shallow landsliding.

  14. Collision of the Tacheng block with the Mayile-Barleik-Tangbale accretionary complex in Western Junggar, NW China: Implication for Early-Middle Paleozoic architecture of the western Altaids

    NASA Astrophysics Data System (ADS)

    Zhang, Ji'en; Xiao, Wenjiao; Luo, Jun; Chen, Yichao; Windley, Brian F.; Song, Dongfang; Han, Chunming; Safonova, Inna

    2018-06-01

    Western Junggar in NW China, located to the southeast of the Boshchekul-Chingiz (BC) Range and to the north of the Chu-Balkhash-Yili microcontinent (CBY), played a key role in the architectural development of the western Altaids. However, the mutual tectonic relationships have been poorly constrained. In this paper, we present detailed mapping, field structural geology, and geochemical data from the Barleik-Mayile-Tangbale Complex (BMTC) in Western Junggar. The Complex is divisible into Zones I, II and III, which are mainly composed of Cambrian-Silurian rocks. Zone I contains pillow lava, siliceous shale, chert, coral-bearing limestone, sandstone and purple mudstone. Zone II consists of basaltic lava, siliceous shale, chert, sandstone and mudstone. Zone III is characterized by basalt, chert, sandstone and mudstone. These rocks represent imbricated ocean plate stratigraphy, which have been either tectonically juxtaposed by thrusting or form a mélange with a block-in-matrix structure. All these relationships suggest that the BMTC is an Early-Middle Paleozoic accretionary complex in the eastern extension of the BC Range. These Early Paleozoic oceanic rocks were thrust onto Silurian sediments forming imbricate thrust stacks that are unconformably overlain by Devonian limestone, conglomerate and sandstone containing fossils of brachiopoda, crinoidea, bryozoa, and plant stems and leaves. The tectonic vergence of overturned folds in cherts, drag-related curved cleavages and σ-type structures on the main thrust surface suggests top-to-the-NW transport. Moreover, the positive εNd(t) values of volcanic rocks from the Tacan-1 drill-core, and the positive εHf(t) values and post-Cambrian ages of detrital zircons from Silurian and Devonian strata to the south of the Tacheng block indicate that its basement is a depleted and juvenile lithosphere. And there was a radial outward transition from coral-bearing shallow marine (shelf) to deep ocean (pelagic) environments, and from

  15. Early Tertiary Exhumation, Erosion, and Sedimentation in the Central Andes, NW Argentina

    NASA Astrophysics Data System (ADS)

    Carrapa, B.; Decelles, P. G.; Gerhels, G.; Mortimer, E.; Strecker, M. R.

    2006-12-01

    Timing of deformation and resulting sedimentation patterns in the Altiplano-Puna Plateau-Eastern Cordillera of the southern Central Andes are the subject of ongoing controversial debate. In the Bolivian Altiplano, sedimentation into a foreland basin system commenced during the Paleocene. Farther south in the Puna and Eastern Cordillera of NW Argentina, a lack of data has precluded a similar interpretation. Early Tertiary non-marine sedimentary rocks are preserved within the present day Puna Plateau and Eastern Cordillera of NW Argentina. The Salar de Pastos Grandes basin in the Puna Plateau contains more than 2 km of Eocene alluvial and fluvial strata in the Geste Formation, deposited in close proximity to orogenic source terrains. Sandstone and conglomerate petrographic data document Ordovician quartzites and minor phyllites and schists as the main source rocks. Detrital zircon U-Pb ages from both the Geste Formation and from underlying Ordovician quartzite cluster in the 900-1200 Ma (Grenville) and late Precambrian-Cambrian (Panafrican) ranges. Sparse late Eocene (~37-34 Ma) grains are also present; their large size, euhedral shape, and decreasing mean ages upsection suggest that these grains are volcanogenic (i.e. ash fall contamination), derived from an inferred magmatic arc to the west. The Eocene ages corroborate mammalian paleontological dates, defining the approximate begin of deposition of the Geste Formation. Alternatively, these young zircons could be of plutonic origin; however, no Eocene plutons are present in the surrounding source rocks and this interpretation is not likely. From W to E, fluvial rocks of the Quebrada de los Colorados Formation show similar sedimentological features as those observed for the Geste Formation, suggesting a genetic link between the two. Detrital zircon U-Pb data show mainly Panafrican ages, with sparse ages in the 860-935 Ma range and a few mid-Proterozoic ages. More importantly, a significant number of late Eocene

  16. Differentiating pedogenesis from diagenesis in early terrestrial paleoweathering surfaces formed on granitic composition parent materials

    USGS Publications Warehouse

    Driese, S.G.; Medaris, L.G.; Ren, M.; Runkel, Anthony C.; Langford, R.P.

    2007-01-01

    Unconformable surfaces separating Precambrian crystalline basement and overlying Proterozoic to Cambrian sedimentary rocks provide an exceptional opportunity to examine the role of primitive soil ecosystems in weathering and resultant formation of saprolite (weathered rock retaining rock structure) and regolith (weathered rock without rock structure), but many appear to have been affected by burial diagenesis and hydrothermal fluid flow, leading some researchers to discount their suitability for such studies. We examine one modern weathering profile (Cecil series), four Cambrian paleoweathering profiles from the North American craton (Squaw Creek, Franklin Mountains, Core SQ-8, and Core 4), one Neoproterozoic profile (Sheigra), and one late Paleoproterozoic profile (Baraboo), to test the hypothesis that these paleoweathering profiles do provide evidence of primitive terrestrial weathering despite their diagenetic and hydrothermal overprinting, especially additions of potassium. We employ an integrated approach using (1) detailed thin-section investigations to identify characteristic pedogenic features associated with saprolitization and formation of well-drained regoliths, (2) electron microprobe analysis to identify specific weathered and new mineral phases, and (3) geochemical mass balance techniques to characterize volume changes during weathering and elemental gains and losses of major and minor elements relative to the inferred parent materials. There is strong pedogenic evidence of paleoweathering, such as clay illuviation, sepic-plasmic fabrics, redoximorphic features, and dissolution and alteration of feldspars and mafic minerals to kaolinite, gibbsite, and Fe oxides, as well as geochemical evidence, such as whole-rock losses of Na, Ca, Mg, Si, Sr, Fe, and Mn greater than in modern profiles. Evidence of diagenesis includes net additions of K, Ba, and Rb determined through geochemical mass balance, K-feldspar overgrowths in overlying sandstone sections, and

  17. A Diploblastic Radiate Animal at the Dawn of Cambrian Diversification with a Simple Body Plan: Distinct from Cnidaria?

    PubMed Central

    Yasui, Kinya; Reimer, James D.; Liu, Yunhuan; Yao, Xiaoyong; Kubo, Daisuke; Shu, Degan; Li, Yong

    2013-01-01

    Background Microfossils of the genus Punctatus include developmental stages such as blastula, gastrula, and hatchlings, and represent the most complete developmental sequence of animals available from the earliest Cambrian. Despite the extremely well-preserved specimens, the evolutionary position of Punctatus has relied only on their conical remains and they have been tentatively assigned to cnidarians. We present a new interpretation of the Punctatus body plan based on the developmental reconstruction aided by recent advances in developmental biology. Results Punctatus developed from a rather large egg, gastrulated in a mode of invagination from a coeloblastura, and then formed a mouth directly from the blastopore. Spiny benthic hatchlings were distinguishable from swimming or crawling ciliate larvae found in cnidarians and sponges. A mouth appeared at the perihatching embryonic stage and was renewed periodically during growth, and old mouths transformed into the body wall, thus elongating the body. Growing animals retained a small blind gut in a large body cavity without partitioning by septa and did not form tentacles, pedal discs or holdfasts externally. A growth center at the oral pole was sufficient for body patterning throughout life, and the body patterning did not show any bias from radial symmetry. Conclusions Contrary to proposed cnidarian affinity, the Punctatus body plan has basic differences from that of cnidarians, especially concerning a spacious body cavity separating ectoderm from endoderm. The lack of many basic cnidarian characters in the body patterning of Punctatus leads us to consider its own taxonomic group, potentially outside of Cnidaria. PMID:23840375

  18. Religion in the National Historical Narrative of the Early Modern Times in Contemporary Ukrainian Schooling

    ERIC Educational Resources Information Center

    Shevchenko, Tetiana

    2015-01-01

    This article deals with religious discourse in modern history school textbooks in Ukraine that cover early modern times in Ukrainian history. It analyzes the place of religious discourse within national discourse, the correlation between local Ukrainian religious and more general discourse, and the representation of the relationships between…

  19. Stress responsiveness and anxiety-like behavior: The early social environment differentially shapes stability over time in a small rodent.

    PubMed

    Sangenstedt, Susanne; Jaljuli, Iman; Sachser, Norbert; Kaiser, Sylvia

    2017-04-01

    The early social environment can profoundly affect behavioral and physiological phenotypes. We investigated how male wild cavy offspring, whose mothers had either lived in a stable (SE) or an unstable social environment (UE) during pregnancy and lactation, differed in their anxiety-like behavior and stress responsiveness. At two different time points in life, we tested the offspring's anxiety-like behavior in a dark-light test and their endocrine reaction to challenge in a cortisol reactivity test. Furthermore, we analyzed whether individual traits remained stable over time. There was no effect of the early social environment on anxiety-like behavior and stress responsiveness. However, at an individual level, anxiety-like behavior was stable over time in UE- but not in SE-sons. Stress responsiveness, in turn, was rather inconsistent in UE-sons and temporally stable in SE-sons. Conclusively, we showed for the first time that the early social environment differentially shapes the stability of behavioral and endocrine traits. At first glance, these results may be surprising, but they can be explained by the different functions anxiety-like behavior and stress responsiveness have. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Classroom Technology Rollouts

    ERIC Educational Resources Information Center

    Blow, Deborah; McConnell, Sandy

    2012-01-01

    At Cambrian School District, educators are trying a new approach as they investigate new technologies. Rather than roll out a one-size-fits-all mandate that one will use this new "box," which may also sit gathering dust, they have implemented a new model. Early in the last school year they announced the Digital Media Academy, and in…

  1. Too Early for Physics? Effect of Class Meeting Time on Student Evaluations of Teaching in Introductory Physics

    ERIC Educational Resources Information Center

    Tobin, R. G.

    2017-01-01

    This paper reports observations that show a significant effect of class meeting time on student evaluations of teaching for an introductory college physics class. Students in a lecture section with an early-morning meeting time gave the class and instructors consistently lower ratings than those in an otherwise nearly identical section that met an…

  2. The Timing of Middle-Childhood Peer Rejection and Friendship: Linking Early Behavior to Early-Adolescent Adjustment

    ERIC Educational Resources Information Center

    Pedersen, Sara; Vitaro, Frank; Barker, Edward D.; Borge, Anne I. H.

    2007-01-01

    This study used a sample of 551 children surveyed yearly from ages 6 to 13 to examine the longitudinal associations among early behavior, middle-childhood peer rejection and friendedness, and early-adolescent depressive symptoms, loneliness, and delinquency. The study tested a sequential mediation hypothesis in which (a) behavior problems in the…

  3. Timing of terrane accretion in eastern and east-central Maine

    NASA Astrophysics Data System (ADS)

    Ludman, Allan

    1986-05-01

    The Norumbega fault zone is often cited as a post-Acadian suture between exotic blocks, even though stratigraphic, structural, and metamorphic data indicate that there is little offset of the Silurian-Devonian strata that the zone cuts in eastern Maine. Similarly, the Kingman fault zone has been shown by gravity and geochemical studies to separate distinct crustal blocks, whereas mapping shows that it lies entirely within a Silurian turbidite package. These conflicts are resolved if the two fault zones represent boundaries between Ordovician or older crustal blocks that had accreted to form a composite terrane prior to deposition of the cover sequences. The faults now mapped within these younger rocks formed by reactivation of the pre-Silurian boundaries during late Acadian time; movement continued until the late Carboniferous. Most of the accretionary history of Maine had thus ended before the Silurian. A complex composite terrane may have formed during Cambrian-Ordovician time that (1) interacted with cratonic North America during the Taconian orogeny and (2) became the “basement” upon which the Silurian and Lower Devonian strata of eastern Maine were deposited.

  4. Monitoring cow activity and rumination time for an early detection of heat stress in dairy cow

    NASA Astrophysics Data System (ADS)

    Abeni, Fabio; Galli, Andrea

    2017-03-01

    The aim of this study was to explore the use of cow activity and rumination time by precision livestock farming tools as early alert for heat stress (HS) detection. A total of 58 Italian Friesian cows were involved in this study during summer 2015. Based on the temperature humidity index (THI), two different conditions were compared on 16 primiparous and 11 multiparous, to be representative of three lactation phases: early (15-84 DIM), around peak (85-154 DIM), and plateau (155-224 DIM). A separate dataset for the assessment of the variance partition included all the cows in the herd from June 7 to July 16. The rumination time (RT2h, min/2 h) and activity index (AI2h, bouts/2 h) were summarized every 2-h interval. The raw data were used to calculate the following variables: total daily RT (RTt), daytime RT (RTd), nighttime RT (RTn), total daily AI (AIt), daytime AI (AId), and nighttime AI (AIn). Either AIt and AId increased, whereas RTt, RTd, and RTn decreased with higher THI in all the three phases. The highest decrease was recorded for RTd and ranged from 49 % (early) to 45 % (plateau). The contribution of the cow within lactation phase was above 60 % of the total variance for AI traits and a share from 33.9 % (for RTt) to 54.8 % (RTn) for RT traits. These observations must be extended to different feeding managements and different animal genetics to assess if different thresholds could be identified to set an early alert system for the farmer.

  5. Moving beyond Screen Time: Redefining Developmentally Appropriate Technology Use in Early Childhood Education. Policy Brief

    ERIC Educational Resources Information Center

    Daugherty, Lindsay; Dossani, Rafiq; Johnson, Erin-Elizabeth; Wright, Cameron

    2014-01-01

    Conversations about what constitutes "developmentally appropriate" use of technology in early childhood education have, to date, focused largely on a single, blunt measure--screen time--that fails to capture important nuances, such as what type of media a child is accessing and whether technology use is taking place solo or with peers.…

  6. Tectonic exhumation and boundary structure of the Kokchetav HP - UHP metamorphic belt (Northern Kazakhstan): constraints from 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Zhimulev, Fedor; de Grave, Johan; Travin, Aleksey; Buslov, Mikhail

    2010-05-01

    The Kokchetav metamorphic belt (KMB) is part of the Early Paleozoic orogenic belt of Northern Kazakhstan and constitutes one of the most famous, classical ultra-high pressure (UHP) metamorphic terranes. The KMB mainly consists of gneisses, mica schists and eclogites. These were formed by Cambrian continental subduction and associated metamorphism of the Precambrian Kokchetav microcontinent and subsequent exhumation of fragments of this metamorphosed continental crust. Several subterranes can be distinguished in the KMB: Barchi, Kumdi-Kol, Sulu-Tube, Enbek-Berlyk, Kulet and Borovoe. These subterranes differ not only in rock composition or in genetic pT conditions, but also in the age of the individual metamorphic events, including the timing of peak, and regressive stages. Most geochronological data indicate a Cambrian age of UHP and HP metamorphism and subsequent exhumation of the KMB. However, there is no field evidence of Cambrian geodynamic processes in the region: Cambrian sediments, volcanic rocks, or large magmatic bodies are completely absent in the KMB setting. The youngest geochronological information in the KMB was obtained on the garnet-mica schists from the Enbek-Berlyk subterrane. The 40Ar/39Ar ages of the muscovite from these schists lies in the range of 490 to 475 Ma (mainly 480-485 Ma). All 40Ar/39Ar stepwise heating experiments yield well-defined plateau and isochron ages. This age is considered to represent the time of emplacement of various heterogeneous nappes, including nappes that consist of HP - UHP metamorphic rocks, to upper crustal levels. To the north, the Kokchetav HP - UHP metamorphic belt is bounded by the Northern Kokchetav tectonic zone (NKTZ). This zone includes thin nappes of (1) Palaeo-Mesoproterozoic gneiss of the metamorphic basement of the Kokchetav microcontinent and Neoproterozoic meta-sandstones and dolomites of its deformed sedimentary cover, (2) pre-Ordovician volcanic rocks of island-arc affinity, (3) Early Ordovician

  7. Exploration in Ordovician of central Michigan Basin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fisher, J.H.; Barratt, M.W.

    1985-12-01

    Deep wells in the central Michigan basin have provided sufficient data to define two new mappable formations - the Foster Formation and the Bruggers Formation. Recent conodont studies have corrected the age assignments of the strata containing these formations. Previously, the lower section (Foster) was classified as mostly Cambrian, and the upper unit (Bruggers) was identified as Early Ordovician. Conodont identifications indicate an Early and Middle Ordovician age for the Foster Formation and a Middle Ordovician age for the Bruggers Formation. The Michigan basin existed in embryonic form in the Late Cambrian, but the full outline of the present-day basinmore » did not develop until Early Ordovician. Gas and condensate are produced from the Bruggers Formation as deep as 11,252 ft (3429 m). Geothermal investigations suggest that gas production is possible to the base of the Paleozoic section in the central basin (17,000 ft or 5181 m). Paleotemperatures were higher during the Paleozoic owing to 3000-4000 ft (914-1291 m) of additional sedimentary cover. Five wells are producing from the Bruggers Formation. All are deeper tests in anticlines producing from Devonian reservoirs discovered earlier. The structures are the result of vertical movements of basement fault blocks activated by regional stresses. 12 figures, 2 tables.« less

  8. Constraints on Early Triassic carbon cycle dynamics from paired organic and inorganic carbon isotope records

    NASA Astrophysics Data System (ADS)

    Meyer, K. M.; Yu, M.; Lehrmann, D.; van de Schootbrugge, B.; Payne, J. L.

    2013-01-01

    Large δ13C excursions, anomalous carbonate precipitates, low diversity assemblages of small fossils, and evidence for marine euxinia in uppermost Permian and Lower Triassic strata bear more similarity to Neoproterozoic carbonates than to the remainders of the Permian and Triassic systems. Middle Triassic diversification of marine ecosystems coincided with the waning of anoxia and stabilization of the global carbon cycle, suggesting that environment-ecosystem linkages were important to biological recovery. However, the Earth system behavior responsible for these large δ13C excursions remains poorly constrained. Here we present a continuous Early Triassic δ13Corg record from south China and use it to test the extent to which Early Triassic excursions in δ13Ccarb record changes in the δ13C of marine dissolved inorganic carbon (DIC). Regression analysis demonstrates a significant positive correlation between δ13Corg and δ13Ccarb across multiple sections that span a paleoenvironmental gradient. Such a correlation is incompatible with diagenetic alteration because no likely mechanism will alter both δ13Corg and δ13Ccarb records in parallel and therefore strongly indicates a primary depositional origin. A simple explanation for this correlation is that a substantial portion of the preserved Corg was derived from the contemporaneous DIC pool, implying that the observed excursions reflect variation in the δ13C of the exogenic carbon reservoir (ocean, atmosphere, biomass). These findings support existing evidence that large δ13C excursions are primary and therefore strengthen the case that large-scale changes to the carbon cycle were mechanistically linked to the low diversity and small size of Early Triassic fossils. Associated sedimentary and biogeochemical phenomena further suggest that similar associations in Neoproterozoic and Cambrian strata may reflect the same underlying controls.

  9. Influence of metabolic-linked early life factors on the eruption timing of the first primary tooth.

    PubMed

    Un Lam, Carolina; Hsu, Chin-Ying Stephen; Yee, Robert; Koh, David; Lee, Yung Seng; Chong, Mary Foong-Fong; Cai, Meijin; Kwek, Kenneth; Saw, Seang Mei; Godfrey, Keith; Gluckman, Peter; Chong, Yap Seng

    2016-11-01

    Early eruption of permanent teeth has been associated with childhood obesity and diabetes mellitus, suggesting links between tooth eruption and metabolic conditions. This longitudinal study aimed to identify pre-, peri- and postnatal factors with metabolic consequences during infancy that may affect the eruption timing of the first primary tooth (ETFT) in children from an ethnically heterogeneous population residing within the same community. Participants were recruited (n = 1033) through the GUSTO (Growing Up in Singapore Towards healthy Outcomes) birth cohort (n = 1237). Oral examinations were performed at 3-month intervals from 6 to 18 months of age. Crude and adjusted analyses, with generalized linear modelling, were conducted to link ETFT to potential determinants occurring during pregnancy, delivery/birth and early infancy. Overall mean eruption age of the first primary tooth was 8.5 (SD 2.6) months. Earlier tooth eruption was significantly associated with infant's rate of weight gain during the first 3 months of life and increased maternal childbearing age. Compared to their Chinese counterparts, Malay and Indian children experienced significantly delayed tooth eruption by 1.2 and 1.7 months, respectively. Infant weight gain from birth to 3 months, ethnicity and maternal childbearing age were significant determinants of first tooth eruption timing. Early life influences can affect primary tooth development, possibly via metabolic pathways. Timing of tooth eruption is linked to general growth and metabolic function. Therefore, it has potential in forecasting oral and systemic conditions such as caries and obesity.

  10. Early-time VLA Observations and Broadband Afterglow Analysis of the Fermi/LAT Detected GRB 130907A

    NASA Astrophysics Data System (ADS)

    Veres, Péter; Corsi, Alessandra; Frail, Dale A.; Cenko, S. Bradley; Perley, Daniel A.

    2015-09-01

    We present multi-wavelength observations of the hyper-energetic gamma-ray burst (GRB) 130907A, a Swift-discovered burst with early radio observations starting at ≈4 hr after the γ-ray trigger. GRB 130907A was also detected by the Fermi/LAT instrument and at late times showed a strong spectral evolution in X-rays. We focus on the early-time radio observations, especially at >10 GHz, to attempt to identify reverse shock signatures. While our radio follow-up of GRB 130907A ranks among the earliest observations of a GRB with the Karl G. Jansky Very Large Array, we did not see an unambiguous signature of a reverse shock. While a model with both reverse and forward shock can correctly describe the observations, the data is not constraining enough to decide upon the presence of the reverse-shock component. We model the broadband data using a simple forward-shock synchrotron scenario with a transition from a wind environment to a constant density interstellar medium (ISM) in order to account for the observed features. Within the confines of this model, we also derive the underlying physical parameters of the fireball, which are within typical ranges except for the wind density parameter (A*), which is higher than those for bursts with wind-ISM transition, but typical for the general population of bursts. We note the importance of early-time radio observations of the afterglow (and of well-sampled light curves) for unambiguously identifying the potential contribution of the reverse shock.

  11. Estimating formation properties from early-time oscillatory water levels in a pumped well

    USGS Publications Warehouse

    Shapiro, A.M.; Oki, D.S.

    2000-01-01

    Hydrologists often attempt to estimate formation properties from aquifer tests for which only the hydraulic responses in a pumped well are available. Borehole storage, turbulent head losses, and borehole skin, however, can mask the hydraulic behavior of the formation inferred from the water level in the pumped well. Also, in highly permeable formations or in formations at significant depth below land surface, where there is a long column of water in the well casing, oscillatory water levels may arise during the onset of pumping to further mask formation responses in the pumped well. Usually borehole phenomena are confined to the early stages of pumping or recovery, and late-time hydraulic data can be used to estimate formation properties. In many instances, however, early-time hydraulic data provide valuable information about the formation, especially if there are interferences in the late-time data. A mathematical model and its Laplace transform solution that account for inertial influences and turbulent head losses during pumping is developed for the coupled response between the pumped borehole and the formation. The formation is assumed to be homogeneous, isotropic, of infinite areal extent, and uniform thickness, with leakage from an overlying aquifer, and the screened or open interval of the pumped well is assumed to fully penetrate the pumped aquifer. Other mathematical models of aquifer flow can also be coupled with the equations describing turbulent head losses and the inertial effects on the water column in the pumped well. The mathematical model developed in this paper is sufficiently general to consider both underdamped conditions for which oscillations arise, and overdamped conditions for which there are no oscillations. Through numerical inversion of the Laplace transform solution, type curves from the mathematical model are developed to estimate formation properties through comparison with the measured hydraulic response in the pumped well. The

  12. Implementation of a landslide early warning system based on near-real-time monitoring, multisensor mapping and geophysical measurements

    NASA Astrophysics Data System (ADS)

    Teza, Giordano; Galgaro, Antonio; Francese, Roberto; Ninfo, Andrea; Mariani, Rocco

    2017-04-01

    An early warning system has been implemented to monitor the Perarolo di Cadore landslide (North-Eastern Italian Alps), which is a slump whose induced risk is fairly high because a slope collapse could form a temporary dam on the underlying torrent and, therefore, could directly threaten the close village. A robotic total station (RTS) measures, with 6h returning time, the positions of 23 retro-reflectors placed on the landslide upper and middle sectors. The landslide's kinematical behavior derived from these near-real-time (NRT) surface displacements is interpreted on the basis of available geomorphological and geological information, geometrical data provided by some laser scanning and photogrammetric surveys, and a landslide model obtained by means of 3D Electrical Resistivity Tomography (3D ERT) measurements. In this way, an analysis of the time series provided by RTS and a pluviometer, which cover several years, allows the definition of some pre-alert and alert kinematical and rainfall thresholds. These thresholds, as well as the corresponding operational recommendations, are currently used for early warning purposes by Authorities involved in risk management for the Perarolo landslide. It should be noted the fact that, as new RTS and pluviometric data are available, the thresholds can be updated and, therefore, a fine tuning of the early warning system can be carried out in order to improve its performance. Although the proposed approach has been implemented in a particular case, it can be used to develop an early warning system based on NRT data in each site where a landslide threatens infrastructures and/or villages that cannot be relocated.

  13. Siberia, the wandering northern terrane, and its changing geography through the Palaeozoic

    NASA Astrophysics Data System (ADS)

    Cocks, L. Robin M.; Torsvik, Trond H.

    2007-05-01

    interpolated and we discuss two different APW path alternatives that result in two very different convergence scenarios between Siberia and Baltica/Kazakh terranes. There are a newly-constructed succession of palaeogeographic maps of Siberia and its nearby areas at various times from the Cambrian to the Permian as, firstly, the peri-Siberian terranes and, secondly, the remainder of the Central Asian terranes accreted to it. Prior to the Early Ordovician, Siberia was in the southern hemisphere, but after that it drifted northwards and for most of the Phanerozoic it has been one of the few larger terranes in the northern hemisphere. The Cambrian and Ordovician maps are provisional for the Altai-Sayan and Mongolian areas, whose geology is highly complex and whose detailed palaeogeography is unresolved. The terms "Altaids" and "Paleo-Asian Ocean" have been used in so many different ways by so many different authors over so many geological periods that we reject their use. Wider issues considered include the possible links between the Cambrian Radiation (often wrongly termed "Explosion"), when metazoan animals first gained hard parts, and True Polar Wander (TPW). New Early Cambrian palaeomagnetic data from Siberia do not show rapid APW (< 10 cm/yr.) or dramatic velocity changes (< 4 cm/yr). It is concluded that the Cambrian Radiation occurred over a period approaching 20 Myr, and that rapid and large-scale TPW did not take place in the Cambrian. In addition, there are no traces of glaciogenic deposits in the very large area of Siberia during the Neoproterozoic, casting some doubt on the "Snowball Earth" hypothesis.

  14. Time resolved optical system for an early detection of prostate tumor

    NASA Astrophysics Data System (ADS)

    Hervé, Lionel; Laidevant, Aurélie; Debourdeau, Mathieu; Boutet, Jérôme; Dinten, Jean-Marc

    2011-02-01

    We developed an endorectal time-resolved optical probe aiming at an early detection of prostate tumors targeted by fluorescent markers. Optical fibers are embedded inside a clinical available ultrasound endorectal probe. Excitation light is driven sequentially from a femtosecond laser (775 nm) into 6 source fibers. 4 detection fibers collect the medium responses at the excitation and fluorescence wavelength (850 nm) by the mean of 4 photomultipliers associated with a 4 channel time-correlated single photon counting card. We also developed the method to process the experimental data. This involves the numerical computation of the forward model, the creation of robust features which are automatically correctly from numerous experimental possible biases and the reconstruction of the inclusion by using the intensity and mean time of these features. To evaluate our system performance, we acquired measurements of a 40 μL ICG inclusion (10 μmol.L-1) at various lateral and depth locations in a phantom. Analysis of results showed we correctly reconstructed the fluorophore for the lateral positions (16 mm range) and for a distance to the probe going up to 1.5 cm. Precision of localization was found to be around 1 mm which complies well with precision specifications needed for the clinical application.

  15. Real-time PCR for the early detection and quantification of Coxiella burnetii as an alternative to the murine bioassay.

    PubMed

    Howe, Gerald B; Loveless, Bonnie M; Norwood, David; Craw, Philip; Waag, David; England, Marilyn; Lowe, John R; Courtney, Bernard C; Pitt, M Louise; Kulesh, David A

    2009-01-01

    Real-time PCR was used to analyze archived blood from non-human primates (NHP) and fluid samples originating from a well-controlled Q fever vaccine efficacy trial. The PCR targets were the IS1111 element and the com1 gene of Coxiella burnetii. Data from that previous study were used to evaluate real-time PCR as an alternative to the use of sero-conversion by mouse bioassay for both quantification and early detection of C. burnetii bacteria. Real-time PCR and the mouse bioassay exhibited no statistical difference in quantifying the number of microorganisms delivered in the aerosol challenge dose. The presence of C. burnetii in peripheral blood of non-human primates was detected by real-time PCR as early after exposure as the mouse bioassay with results available within hours instead of weeks. This study demonstrates that real-time PCR has the ability to replace the mouse bioassay to measure dosage and monitor infection of C. burnetii in a non-human primate model.

  16. Combining multiple earthquake models in real time for earthquake early warning

    USGS Publications Warehouse

    Minson, Sarah E.; Wu, Stephen; Beck, James L; Heaton, Thomas H.

    2017-01-01

    The ultimate goal of earthquake early warning (EEW) is to provide local shaking information to users before the strong shaking from an earthquake reaches their location. This is accomplished by operating one or more real‐time analyses that attempt to predict shaking intensity, often by estimating the earthquake’s location and magnitude and then predicting the ground motion from that point source. Other EEW algorithms use finite rupture models or may directly estimate ground motion without first solving for an earthquake source. EEW performance could be improved if the information from these diverse and independent prediction models could be combined into one unified, ground‐motion prediction. In this article, we set the forecast shaking at each location as the common ground to combine all these predictions and introduce a Bayesian approach to creating better ground‐motion predictions. We also describe how this methodology could be used to build a new generation of EEW systems that provide optimal decisions customized for each user based on the user’s individual false‐alarm tolerance and the time necessary for that user to react.

  17. Palaeogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: palaeotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, A. C.; Guillocheau, F.; Robin, C.; Rohais, S.; Moulin, M.; Aslanian, D.

    2012-04-01

    The tectonic and sedimentary evolution of the Early Cretaceous rift of the central segment of the South Atlantic Ocean is debated. Our objective is to better constraint the timing of its evolution by drawing palaeogeographic and deformation maps. Eight palaeogeographic and deformations maps were drawn from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollens) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains that have a different history in terms of deformation and palaeogeography. The southern domain includes Namibe, Santos and Campos Basins. The northern domain extends from Espirito Santo and North Kwanza Basins, in the South, to Sergipe-Alagoas and North Gabon Basins to the North. Extension started in the northern domain during Late Berriasian (Congo-Camamu Basin to Sergipe-Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain. This is time of emplacement of the Parana-Etendeka Trapp (Late Hauterivian-Early Barremian). Extension started in this southern domain during Early Barremian. The brittle extensional period is shorter in the South (5-6 Ma, Barremian to base Aptian) than in the North (19 to 20 Myr, Upper Berriasian to Base Aptian). From Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower one, organic-rich with no more highs. The lake migrates southward in two steps, until Valanginian at the border between the northern and southern domains, until Early Barremian, North of Walvis Ridge. The Sag phase is of Middle to Late Aptian age. In the southern domain, the transition between the brittle rift and the sag phase is continuous. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age, possible period of mantle exhumation. Marine

  18. Monitoring cow activity and rumination time for an early detection of heat stress in dairy cow.

    PubMed

    Abeni, Fabio; Galli, Andrea

    2017-03-01

    The aim of this study was to explore the use of cow activity and rumination time by precision livestock farming tools as early alert for heat stress (HS) detection. A total of 58 Italian Friesian cows were involved in this study during summer 2015. Based on the temperature humidity index (THI), two different conditions were compared on 16 primiparous and 11 multiparous, to be representative of three lactation phases: early (15-84 DIM), around peak (85-154 DIM), and plateau (155-224 DIM). A separate dataset for the assessment of the variance partition included all the cows in the herd from June 7 to July 16. The rumination time (RT2h, min/2 h) and activity index (AI2h, bouts/2 h) were summarized every 2-h interval. The raw data were used to calculate the following variables: total daily RT (RTt), daytime RT (RTd), nighttime RT (RTn), total daily AI (AIt), daytime AI (AId), and nighttime AI (AIn). Either AIt and AId increased, whereas RTt, RTd, and RTn decreased with higher THI in all the three phases. The highest decrease was recorded for RTd and ranged from 49 % (early) to 45 % (plateau). The contribution of the cow within lactation phase was above 60 % of the total variance for AI traits and a share from 33.9 % (for RTt) to 54.8 % (RTn) for RT traits. These observations must be extended to different feeding managements and different animal genetics to assess if different thresholds could be identified to set an early alert system for the farmer.

  19. Research on intelligent scenic security early warning platform based on high resolution image: real scene linkage and real-time LBS

    NASA Astrophysics Data System (ADS)

    Li, Baishou; Huang, Yu; Lan, Guangquan; Li, Tingting; Lu, Ting; Yao, Mingxing; Luo, Yuandan; Li, Boxiang; Qian, Yongyou; Gao, Yujiu

    2015-12-01

    This paper design and implement security monitor system within a scenic spot for tourists, the scenic spot staff can be automatic real time for visitors to perception and monitoring, and visitors can also know about themselves location in the scenic, real-time and obtain the 3D imaging conditions of scenic area. Through early warning can realize "parent-child relation", preventing the old man and child lost and wandering. Research results to the further development of virtual reality to provide effective security early warning platform of the theoretical basis and practical reference.

  20. The practical application of adaptive study design in early phase clinical trials: a retrospective analysis of time savings.

    PubMed

    Lorch, U; Berelowitz, K; Ozen, C; Naseem, A; Akuffo, E; Taubel, J

    2012-05-01

    The interest in adaptive study design is evident from the growing amount of clinical research employing this model in the mid to later stages of medicines development. Little has been published on the practical application and merits of adaptive study design in early phase clinical research. This paper describes a retrospective analysis performed on a sample of 29 industry lead adaptive early phase studies commencing between 1 January 2006 and 31 December 2010 in a clinical trials unit in London, England. All studies containing at least one adaptive feature in the original protocol were included in the analysis. The scope of the analysis was to assess whether the use of adaptive study designs provided tangible benefits over the use of conventional study designs using time savings as the main measure. We conclude that the use of adaptive study design saves time in early phase research programs. This is achieved by abolishing the need for substantial amendments or by mitigating their impact on timelines and by using adaptive scheduling efficiencies.

  1. Tectonics of Antarctica

    USGS Publications Warehouse

    Hamilton, W.

    1967-01-01

    Antarctica consists of large and wholly continental east Antarctica and smaller west Antarctica which would form large and small islands, even after isostatic rebound, if its ice cap were melted. Most of east Antarctica is a Precambrian Shield, in much of which charnockites are characteristic. The high Transantarctic Mountains, along the Ross and Weddell Seas, largely follow a geosyncline of Upper Precambrian sedimentary rocks that were deformed, metamorphosed and intruded by granitic rocks during Late Cambrian or Early Ordovician time. The rocks of the orogen were peneplained, then covered by thin and mostly continental Devonian-Jurassic sediments, which were intruded by Jurassic diabase sheets and overlain by plateau-forming tholeiites. Late Cenozoic doming and block-faulting have raised the present high mountains. Northeastern Victoria Land, the end of the Transantarctic Mountains south of New Zealand, preserves part of a Middle Paleozoic orogen. Clastic strata laid unconformably upon the Lower Paleozoic plutonic complex were metamorphosed at low grade, highly deformed and intruded by Late Devonian or Early Carboniferous granodiorites. The overlying Triassic continental sedimentary rocks have been broadly folded and normal-faulted. Interior west Antarctica is composed of miogeosynclinal clastic and subordinate carbonate rocks which span the Paleozoic Era and which were deformed, metamorphosed at generally low grade, and intruded by granitic rocks during Early Mesozoic time and possibly during other times also. Patterns of orogenic belts, if systematic, cannot yet be defined; but fragmentation and rotation of crustal blocks by oroclinal folding and strike-slip faulting can be suggested. The Ellsworth Mountains, for example, consist of Cambrian-Permian metasedimentary rocks that strike northward toward the noncorrelative and latitudinally striking Mesozoic terrane of the Antarctic Peninsula in one direction and southward toward that of the Lower Paleozoic: terrane

  2. Trace- and rare-earth element geochemistry and Pb-Pb dating of black shales and intercalated Ni-Mo-PGE-Au sulfide ores in Lower Cambrian strata, Yangtze Platform, South China

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-Yong; Chen, Yong-Quan; Ling, Hong-Fei; Yang, Jing-Hong; Feng, Hong-Zhen; Ni, Pei

    2006-08-01

    The Lower Cambrian black shale sequence of the Niutitang Formation in the Yangtze Platform, South China, hosts an extreme metal-enriched sulfide ore bed that shows >10,000 times enrichment in Mo, Ni, Se, Re, Os, As, Hg, and Sb and >1,000 times enrichment in Ag, Au, Pt, and Pd, when compared to average upper continental crust. We report in this paper trace- and rare-earth-element concentrations and Pb-Pb isotope dating for the Ni-Mo-PGE-Au sulfide ores and their host black shales. Both the sulfide ores and their host black shales show similar trace-element distribution patterns with pronounced depletion in Th, Nb, Hf, Zr, and Ti, and extreme enrichment in U, Ni, Mo, and V compared to average upper crust. The high-field-strength elements, such as Zr, Hf, Nb, Ta, Sc, Th, rare-earth elements, Rb, and Ga, show significant inter-element correlations and may have been derived mainly from terrigenous sources. The redox sensitive elements, such as V, Ni, Mo, U, and Mn; base metals, such as Cu, Zn, and Pb; and Sr and Ba may have been derived from mixing of seawater and venting hydrothermal sources. The chondrite-normalized REE patterns, positive Eu and Y anomalies, and high Y/Ho ratios for the Ni-Mo-PGE-Au sulfide ores are also suggestive for their submarine hydrothermal-exhalative origin. A stepwise acid-leaching Pb-Pb isotope analytical technique has been employed for the Niutitang black shales and the Ni-Mo-PGE-Au sulfide ores, and two Pb-Pb isochron ages have been obtained for the black shales (531±24 Ma) and for the Ni-Mo-PGE-Au sulfide ores (521±54 Ma), respectively, which are identical and overlap within uncertainty, and are in good agreement with previously obtained ages for presumed age-equivalent strata.

  3. Comparison of organic geochemistry and metal enrichment in two black shales: Cambrian Alum Shale of Sweden and Devonian Chattanooga Shale of United States

    USGS Publications Warehouse

    Leventhal, J.S.

    1991-01-01

    In most black shales, such as the Chattanooga Shale and related shales of the eastern interior United States, increased metal and metalloid contents are generally related to increased organic carbon content, decreased sedimentation rate, organic matter type, or position in the basin. In areas where the stratigraphic equivalents of the Chattanooga Shale are deeply buried and and the organic material is thermally mature, metal contents are essentially the same as in unheated areas and correlate with organic C or S contents. This paradigm does not hold for the Cambrian Alum Shale Formation of Sweden where increased metal content does not necessarily correlate with organic matter content nor is metal enrichment necessarily related to land derived humic material because this organic matter is all of marine source. In southcentral Sweden the elements U, Mo, V, Ni, Zn, Cd and Pb are all enriched relative to average black shales but only U and Mo correlate to organic matter content. Tectonically disturbed and metamorphosed allochthonous samples of Alum Shale on the Caledonian front in western Sweden have even higher amounts for some metals (V, Ni, Zn and Ba) relative to the autochthonous shales in this area and those in southern Sweden. ?? 1991 Springer-Verlag.

  4. Simple Predictive Model of Early Failure among Patients Undergoing First-Time Arteriovenous Fistula Creation.

    PubMed

    Eslami, Mohammad H; Zhu, Clara K; Rybin, Denis; Doros, Gheorghe; Siracuse, Jeffrey J; Farber, Alik

    2016-08-01

    Native arteriovenous fistulas (AVFs) have a high 1 year failure rate leading to a need for secondary procedures. We set out to create a predictive model of early failure in patients undergoing first-time AVF creation, to identify failure-associated factors and stratify initial failure risk. The Vascular Study Group of New England (VSGNE) (2010-2014) was queried to identify patients undergoing first-time AVF creation. Patients with early (within 3 months postoperation) AVF failure (EF) or no failure (NF) were compared, failure being defined as any AVF that could not be used for dialysis. A multivariate logistic regression predictive model of EF based on perioperative clinical variables was created. Backward elimination with alpha level of 0.2 was used to create a parsimonious model. We identified 376 first-time AVF patients with follow-up data available in VSGNE. EF rate was 17.5%. Patients in the EF group had lower rates of hypertension (80.3% vs. 93.2%, P = 0.003) and diabetes (47.0% vs. 61.3%, P = 0.039). EF patients were also more likely to have radial artery inflow (57.6% vs. 38.4%, P = 0.011) and have forearm cephalic vein outflow (57.6% vs. 36.5%, P = 0.008). Additionally, the EF group was noted to have significantly smaller mean diameters of target artery (3.1 ± 0.9 vs. 3.6 ± 1.1, P = 0.002) and vein (3.1 ± 0.7 vs. 3.6 ± 0.9, P < 0.001). Multivariate analyses revealed that hypertension, diabetes, and vein larger than 3 mm were protective of EF (P < 0.05). The discriminating ability of this model was good (C-statistic = 0.731) and the model fits the data well (Hosmer-Lemeshow P = 0.149). β-estimates of significant factors were used to create a point system and assign probabilities of EF. We developed a simple model that robustly predicts first-time AVF EF and suggests that anatomical and clinical factors directly affect early AVF outcomes. The risk score has the potential to be used in clinical settings to stratify risk and make

  5. Tectonic history of the Illinois basin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kolata, D.R.; Nelson, J.W.

    1990-05-01

    The Illinois basin began as a failed rift that developed during breakup of a supercontinent approximately 550 Ma. A rift basin in the southernmost part of the present Illinois basin subsided rapidly and filled with about 3,000 m of probable Early and Middle Cambrian sediments. By the Late Cambrian, the rift-bounding faults became inactive and a broad relatively slowly subsiding embayment, extending well beyond the rift and open to the Iapetus Ocean, persisted through most of the Paleozoic Era. Widespread deformation swept through the proto-Illinois basin beginning in the latest Mississippian, continuing to the end of the Paleozoic Era. Upliftmore » of basement fault blocks resulted in the formation of many major folds and faults. The timing of deformation and location of these structures in the forelands of the Ouachita and Alleghanian orogenic belts suggest that much of the deformation resulted from continental collision between North America and Gondwana. The associated compressional stress reactivated the ancient rift-bounding faults, upthrusting the northern edge of a crustal block approximately 1,000 m within the rift. Concurrently, dikes (radiometrically dated as Early Permian), sills, and explosion breccias formed in or adjacent to the reactivated rift. Subsequent extensional stress, probably associated with breakup of Pangea, caused the crustal block within the rift to sink back to near its original position. High-angle, northeast- to east-west-trending normal faults, with as much as 1,000 m of displacement, formed in the southern part of the basin. These faults displace some of the northwest trending Early Permian dikes. Structural closure of the southern end of the Illinois basin was caused by uplift of the Pascola arch sometime between the Late Pennsylvanian and Late Cretaceous.« less

  6. Tectonic and regional metamorphic implications of the discovery of Middle Ordovician conodonts in cover rocks east of the Green Mountain massif, Vermont

    USGS Publications Warehouse

    Ratcliffe, N.M.; Harris, A.G.; Walsh, G.J.

    1999-01-01

    Middle Ordovician (late Arenigian - early Caradocian) conodonts were recovered from a dolostone lens in carbonaceous schist 30 m below the base of the Pinney Hollow Formation in the Eastern Cover sequence near West Bridgewater, Vermont. These are the first reported fossils from the metamorphic cover sequence rocks east of the Green Mountain, Berkshire, and Housatonic massifs of western New England. The conodonts are recrystallized, coated with graphitic matter, thermally altered to a color alteration index (CAI) of at least 5, and tectonically deformed. The faunule is nearly monospecific, consisting of abundant Periodon aculeatus Hadding? and rare Protopanderodus. The preponderance of Periodon and the absence of warm, shallow-water species characteristic of the North American Midcontinent Conodont Province suggest a slope or basin depositional setting. The conodont-bearing carbonaceous schist is traceable 3 km southeast to the Plymouth area, where it had been designated the uppermost member of the Plymouth Formation, previously regarded as Early Cambrian in age. The age and structural position of the carbonaceous schist above dolostones of the Plymouth Formation but below the Pinney Hollow Formation (upper Proterozoic and Lower Cambrian?) suggest that this unit may be correlative or time transgressive with the Ira Formation, which underlies the Taconic allochthons in the Vermont Valley. Such a correlation supports the concept of placing the western limit of the root zone of the Taconic allochthons beneath the Pinney Hollow Formation. An approximate absolute age assignment for the conodont-bearing rock is between 470 and 454 Ma. This suggests that dynamothermal metamorphism during the Taconian orogeny on the east flank of the Green Mountains was younger than early Caradocian, which is in accord with the middle Caradocian age of the Ira Formation west of the Green Mountain massif.

  7. The Relationship Between Cardiac Conduction Times, Cardiovascular Risk Factors, and Inflammation in Patients with Early Arthritis.

    PubMed

    Turk, Samina A; Heslinga, Sjoerd C; Dekker, Jill; Britsemmer, Linda; van der Lugt, Véronique; Lems, Willem F; van Schaardenburg, Dirkjan; Nurmohamed, Michael T

    2017-05-01

    To investigate the prevalence of conduction disorders in patients with early arthritis and the relationship with inflammation and traditional cardiovascular (CV) risk factors. Patients with rheumatoid arthritis (RA) have a 2-fold higher risk of sudden cardiac death, possibly owing to conduction disorders. This increased risk might already be present at the clinical onset of arthritis. Therefore, we assessed electrocardiography, blood pressure, 28-joint Disease Activity Score (DAS28), lipid profile, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) level in 480 patients with early arthritis at baseline and after 1 year. The prevalence of conduction disorders was 12.5%. Conduction times at baseline were not associated with DAS28, ESR, or CRP levels and did not change during antirheumatic treatment. Baseline and the improvement in DAS28 (European League Against Rheumatism response), ESR, and CRP were significantly associated with heart rate, lipid profile, and blood pressure. Elevated total cholesterol and blood pressure were associated with an increased QRS time. The change in heart rate differed 7.3 bpm between patients with the least versus largest DAS improvement. The prevalence of conduction disorders in patients with early arthritis was 12.5%, which is similar to the general population and was not associated with changes in inflammation markers. However, a high cholesterol was associated with a prolonged QRS time. Therefore, the emphasis of CV risk management in arthritis should not be only on treatment of disease activity but also on traditional CV risk factors. The relationship between the improvement in disease activity and heart rate is remarkable because this could imply a 10-year CV mortality risk difference of 24%.

  8. Early literacy and early numeracy: the value of including early literacy skills in the prediction of numeracy development.

    PubMed

    Purpura, David J; Hume, Laura E; Sims, Darcey M; Lonigan, Christopher J

    2011-12-01

    The purpose of this study was to examine whether early literacy skills uniquely predict early numeracy skills development. During the first year of the study, 69 3- to 5-year-old preschoolers were assessed on the Preschool Early Numeracy Skills (PENS) test and the Test of Preschool Early Literacy Skills (TOPEL). Participants were assessed again a year later on the PENS test and on the Applied Problems and Calculation subtests of the Woodcock-Johnson III Tests of Achievement. Three mixed effect regressions were conducted using Time 2 PENS, Applied Problems, and Calculation as the dependent variables. Print Knowledge and Vocabulary accounted for unique variance in the prediction of Time 2 numeracy scores. Phonological Awareness did not uniquely predict any of the mathematics domains. The findings of this study identify an important link between early literacy and early numeracy development. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. Mrc1 Marks Early-Firing Origins and Coordinates Timing and Efficiency of Initiation in Fission Yeast ▿ †

    PubMed Central

    Hayano, Motoshi; Kanoh, Yutaka; Matsumoto, Seiji; Masai, Hisao

    2011-01-01

    How early- and late-firing origins are selected on eukaryotic chromosomes is largely unknown. Here, we show that Mrc1, a conserved factor required for stabilization of stalled replication forks, selectively binds to the early-firing origins in a manner independent of Cdc45 and Hsk1 kinase in the fission yeast Schizosaccharomyces pombe. In mrc1Δ cells (and in swi1Δ cells to some extent), efficiency of firing is stimulated, and its timing is advanced selectively at those origins that are normally bound by Mrc1. In contrast, the late or inefficient origins which are not bound by Mrc1 are not activated in mrc1Δ cells. The enhanced firing and precocious Cdc45 loading at Mrc1-bound early-firing origins are not observed in a checkpoint mutant of mrc1, suggesting that non-checkpoint function is involved in maintaining the normal program of early-firing origins. We propose that prefiring binding of Mrc1 is an important marker of early-firing origins which are precociously activated by the absence of this protein. PMID:21518960

  10. Early, On-Time, and Late Behavioural Autonomy in Adolescence: Psychosocial Correlates in Young and Middle Adulthood

    ERIC Educational Resources Information Center

    Pavlova, Maria K.; Haase, Claudia M.; Silbereisen, Rainer K.

    2011-01-01

    Drawing on two nationally representative German studies (N[subscript 1] = 1744, N[subscript 2] = 759), we examined correlates of early, on-time, and late curfew autonomy, a retrospective indicator of behavioural autonomy, in young and middle adulthood (19-37 years of age). Adjustment in four domains was considered: educational attainment,…

  11. Early-Time Solution of the Horizontal Unconfined Aquifer in the Buildup Phase

    NASA Astrophysics Data System (ADS)

    Gravanis, Elias; Akylas, Evangelos

    2017-10-01

    We derive the early-time solution of the Boussinesq equation for the horizontal unconfined aquifer in the buildup phase under constant recharge and zero inflow. The solution is expressed as a power series of a suitable similarity variable, which is constructed so that to satisfy the boundary conditions at both ends of the aquifer, that is, it is a polynomial approximation of the exact solution. The series turns out to be asymptotic and it is regularized by resummation techniques that are used to define divergent series. The outflow rate in this regime is linear in time, and the (dimensionless) coefficient is calculated to eight significant figures. The local error of the series is quantified by its deviation from satisfying the self-similar Boussinesq equation at every point. The local error turns out to be everywhere positive, hence, so is the integrated error, which in turn quantifies the degree of convergence of the series to the exact solution.

  12. Assessment of Paleozoic terrane accretion along the southern central Andes using detrital zircon geochronology

    NASA Astrophysics Data System (ADS)

    McKenzie, R.; Horton, B. K.; Fuentes, F.; Fosdick, J. C.; Capaldi, T.; Stockli, D. F.; Alvarado, P. M.

    2015-12-01

    Two distinct Paleozoic terranes known as Cuyania and Chilenia occupy the southern central Andes of Argentina and Chile. Because the proposed terrane boundaries coincide with major structural elements of the modern Andean system at 30-36°S, it is important to understand their origins and potential role in guiding later Andean deformation. The Cuyania terrane of western Argentina encompasses the Precordillera (PC) and a thick-skinned thrust block of the western Sierras Pampeanas, persisting southward to the San Rafael Basin (SRB). Although recently challenged, Cuyania has been long considered a piece of southern Laurentia that rifted away during the early Cambrian and collided with the Argentine margin during the Ordovician. Chilenia is situated west of Cuyania and includes the Frontal Cordillera (FC) and Andean magmatic arc. This less-studied terrane was potentially accreted during an enigmatic Devonian orogenic event. We present new detrital zircon U-Pb age data from siliciclastic sedimentary rocks that span the entire Paleozoic to Triassic from the FC, PC, and SRB. Cambrian rocks of the PC exhibit similar zircon age distributions with prominent ~1.4 and subordinate ~1.1 Ga populations, which are distinct from other Paleozoic strata. Plutonic rocks with these ages are common in southern Laurentia, whereas ~1.4 Ga zircons are uncommon in South American age distributions. This supports a Laurentian origin for Cuyania in isolation from Argentina during the Cambrian. Upper Paleozoic strata from the PC, FC, and SRB all yield similar age data suggesting shared provenance across the proposed Cuyania-Chilenia suture. Age distributions also notably lack Devonian-age grains. The regional paucity of Devonian plutonic rocks and detrital zircon casts doubt on a possible arc system between these terranes at this time, a key requisite for the mid-Paleozoic transfer and accretion of Chilenia to the Argentine margin. Collectively, these data question the precise boundaries of the

  13. [Part time work instead of early retirement: successful breakthrough for flexible and later retirement?].

    PubMed

    Bäcker, G; Naegele, G

    1996-01-01

    In order to stop the trend towards early retirement in Germany a law to promote partial retirement recently has been passed by parliament. Concerning the impact on the labour market the raising of the pension age for older unemployed which is fixed in this law has to be seen as contraproductive and it will deteriorate the financial situation of unemployed older workers. Concerning the implementation of partial-retirement as such, there are momentous obstacles to realize part-time working arrangements in practice: the insufficient financial compensation for older workers and the obligation for employers to hire unemployed workers. Supplementary collective agreements are seen to be necessary to establish part-time work for older workers.

  14. Interest of waiting time for spontaneous early reconnection after cavotricuspid isthmus ablation: A monocentric randomized trial.

    PubMed

    Marchandise, Sébastien; Scavée, Christophe; Barbraud, Cynthia; de Meester de Ravenstein, Christophe; Balola Bagalwa, Mittérand; Goesaert, Cédric; Reis-Pinheiro, Ivone; le Polain de Waroux, Jean-Benoit

    2017-12-01

    The aim of this study was to determine the rate of recurrent atrial flutter (AFl) after isolated cavotricuspid isthmus (CTI) ablation and to evaluate the impact of a waiting period with the search for early resumption of the CTI block on the long-term outcome. Three hundred and nineteen consecutive patients referred for typical AFl ablation were randomly assigned to CTI ablation with continuous reevaluation of the CTI block during 30 minutes and early reablation if needed (waiting time [WT] + group, n  =  155) or to CTI ablation with no waiting period after proven bidirectional CTI block (WT - group, n  =  164). All patients were regularly followed-up. In the WT+ group, 10 patients (6%) presented a recovery across the CTI (time to recovery: 17 ± 7') and were reablated at the end of the waiting period. After a median follow-up of 21 months, the rate of recurrent AFl was significantly higher in the WT - group as compared to the WT+ group (11.6% [19/164] vs 2.5% [4/155], respectively; P  =  0.007). However, no significant differences in the subsequent rate of AF were observed between the two groups (29% [WT -] vs 32% [WT+], P  =  0.66). During the follow-up, 28 patients from the WT - group underwent a second ablation procedure (16 AFl redo and 12 AF ablation) versus 10 patients form the WT+ group (three AFl redo and seven AF ablation). Waiting 30 minutes after CTI ablation to check for early resumption and early reablation allows for decreasing significantly the rate of recurrent atrial flutter. © 2017 Wiley Periodicals, Inc.

  15. Early Adolescent Boys' Exposure to Internet Pornography: Relationships to Pubertal Timing, Sensation Seeking, and Academic Performance

    ERIC Educational Resources Information Center

    Beyens, Ine; Vandenbosch, Laura; Eggermont, Steven

    2015-01-01

    Research has demonstrated that adolescents regularly use Internet pornography. This two-wave panel study aimed to test an integrative model in early adolescent boys (M[subscript age] = 14.10; N = 325) that (a) explains their exposure to Internet pornography by looking at relationships with pubertal timing and sensation seeking, and (b) explores…

  16. Microbial mats in playa lakes and other saline habitats: Early Mars analog?

    NASA Technical Reports Server (NTRS)

    Bauld, John

    1989-01-01

    Microbial mats are cohesive benthic microbial communities which inhabit various Terra (Earth-based) environments including the marine littoral and both permanent and ephemeral (playa) saline lakes. Certain geomorphological features of Mars, such as the Margaritifer Sinus, were interpreted as ancient, dried playa lakes, presumably formed before or during the transition to the present Mars climate. Studies of modern Terran examples suggest that microbial mats on early Mars would have had the capacity to survive and propagate under environmental constraints that would have included irregularly fluctuating regimes of water activity and high ultraviolet flux. Assuming that such microbial communities did indeed inhabit early Mars, their detection during the Mars Rover Sample Return (MRSR) mission depends upon the presence of features diagnostic of the prior existence of these communities or their component microbes or, as an aid to choosing suitable landing, local exploration or sampling sites, geomorphological, sedimentological or chemical features characteristic of their playa lake habitats. Examination of modern Terran playas (e.g., the Lake Eyre basin) shows that these features span several orders of magnitude in size. While stromatolites are commonly centimeter-meter scale features, bioherms or fields of individuals may extend to larger scales. Preservation of organic matter (mats and microbes) would be favored in topographic lows such as channels or ponds of high salinity, particularly those receiving silica-rich groundwaters. These areas are likely to be located near former zones of groundwater emergence and/or where flood channels entered the paleo-playa. Fossil playa systems which may aid in assessing the applicability of this particular Mars analog include the Cambrian Observatory Hill Beds of the Officer Basin and the Eocene Wilkins Peak Member of the Green River Formation.

  17. Geologic Map of the Gold Creek Gold District, Elko County, Nevada

    USGS Publications Warehouse

    Ketner, Keith B.

    2007-01-01

    The Gold Creek, Nev. area displays important stratigraphic and structural relationships between Paleozoic and early Tertiary sedimentary strata in an area dominated by large intrusive bodies of Mesozoic age and extensive volcanic fields of middle to late Tertiary age. An autochthonous sequence includes the Cambrian and Proterozoic(?) Prospect Mountain Quartzite and the overlying Cambrian and Ordovician Tennessee Mountain Formation. This autochthon is overlain by three allochthonous plates each composed of a distinctive sequence of strata and having a distinctive internal structure. The structurally lowest plate is composed of the Havallah sequence, locally of Mississippian and Pennsylvanian age, which is folded on north-south trending axes. The next higher plate is composed of somewhat younger Pennsylvanian and Permian strata cut by east-west trending low-angle faults. The highest plate is composed of early Tertiary non-marine sedimentary and igneous rocks folded on varied but mainly north-south trending axes. The question of whether the allochthonous plates were emplaced by contractional or extensional forces is indeterminate from the local evidence. Mineral deposits include gold placers of moderate size and small pockets of base metals, none of which is currently being exploited.

  18. Petroleum geology and resources of the Nepa-Botuoba High, Angara-Lena Terrace, and Cis-Patom Foredeep, southeastern Siberian Craton, Russia

    USGS Publications Warehouse

    Ulmishek, Gregory F.

    2001-01-01

    . These rocks presently are deformed and metamorphosed, but they generated oil and gas before the deformation occurred in Late Silurian and Devonian time. Generated hydrocarbons migrated updip onto the craton margin. The time of migration and formation of fields is constrained by the deposition of Lower Cambrian salt and by the Late Silurian or Devonian metamorphism of source rocks. This time frame indicates that the TPS is one of the oldest petroleum systems in the world. All three provinces are exploration frontiers, and available geologic data are limited; therefore, only one assessment unit has been identified. The largest undiscovered hydrocarbon resources are expected to be in Vendian clastic reservoirs in both structural and stratigraphic traps of the Nepa-Botuoba High province. The petroleum potential of Vendian?lowermost Cambrian carbonate reservoirs is smaller. Nevertheless, these reservoirs may contain significant resources. Gas is expected to dominate over oil in the resource base.

  19. Petroleum geology and resources of the Baykit High province, East Siberia, Russia

    USGS Publications Warehouse

    Ulmishek, Gregory F.

    2001-01-01

    west of the Baykit high are probable source rocks. Their areal distribution extends from the foldbelt into the foredeep along the province?s western margin. Potential source rocks also are present in platform depressions in eastern areas of the province. Hydrocarbon generation and migration west of the province started as early as Riphean time, before the beginning of the deformation in the Yenisey Ridge foldbelt that occurred about 820?850 million years ago. However, the presently known oil and gas accumulations were formed after deposition of the Lower Cambrian salt seal. Available data allow identification of only one assessment unit, and it covers the entire TPS area. Undiscovered oil and gas resources are moderate, primarily due to the poor quality of reservoir rocks. However, the reserve growth in the Yurubchen-Tokhom zone may be large and may exceed the volume of undiscovered resources in the rest of the province. Most oil and gas resourcesareexpectedtobeinstructuralandstratigraphictrapsin Riphean carbonate reservoirs. Vendian clastic reservoirs are probably gas-prone.

  20. [Evaluation on stability of internal controls in human cardiac muscle by real-time RT-PCR during early postmortem interval].

    PubMed

    Zhang, Ping; Ma, Kai-Jun; Zhang, Heng; Wang, Hui-Jun; Shen, Yi-Wen; Chen, Long

    2012-04-01

    To explore the stability of internal controls in human cardiac muscle by real-time RT-PCR during early postmortem interval (PMI) in order to find the most stable marker. Ten individuals with similar environmental conditions (the average store temperature: 25 degrees C) and different PMI ranging from 4.3 to 22.3 h were selected. Total RNA was extracted from each sample and six commonly internal controls were used including beta-actin, GAPDH, B2M, U6, 18S rRNA and HSA-miR-1, and the expression was detected in cardiac muscle by real-time RT-PCR. The expression stability of internal controls was evaluated using genormPLUS software during early PMI. The internal control with the most stability was selected. The relationship between the most stable marker and its expression level affected by some other parameters such as age, gender and cause of death was also analyzed. The U6 showed the most stable expression during early PMI in cardiac muscle, and its expression level was not affected by those parameters including age, gender and cause of death (P > 0.05). U6 may be a valuable internal control for the study of relationship between PMI determination and degradation of nucleic acid in human cardiac muscle by real-time RT-PCR.

  1. Poverty and Awakening Cortisol in Adolescence: The Importance of Timing in Early Life

    PubMed Central

    McFarland, Michael J.; Hayward, Mark D.

    2015-01-01

    The deleterious effects of poverty on mental and physical health are routinely argued to operate, at least in part, via dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis, although empirical examinations connecting poverty with HPA axis functioning are rare. Research on the effects of timing of poverty is a particularly neglected aspect of this relationship. This study uses 15 years of prospective data from the Study of Early Child Care and Youth Development to assess how exposure to poverty during infancy, childhood, and adolescence is related to awakening cortisol (n = 826), a marker of HPA axis functioning. Among female participants, poverty exposure in infancy and adolescence, but not childhood, was negatively associated with awakening cortisol. Poverty exposure was unrelated to cortisol among male participants. The importance of timing and gender differences are discussed along with directions for future research. PMID:26140229

  2. Provenance, tectonic setting and source-area weathering of the lower Cambrian sediments of the Parahio valley in the Spiti basin, India

    NASA Astrophysics Data System (ADS)

    Pandey, Shivani; Parcha, Suraj K.

    2017-03-01

    The geochemical study of siliciclastic rocks from the Lower Cambrian of Parahio Valley has been studied to describe the provenance, chemical weathering and tectonic setting. The K2O/Al2O3 ratio and positive correlation of Co ( r=0.85), Ni ( r=0.86), Zn ( r=0.82), Rb ( r=0.98) with K2O reflects that the presence of clay minerals control the abundances of these elements and suggests a warm and humid climate for this region. The chondrite normalized REE pattern of the samples is equivalent to upper continental crust, which reflects enriched LREE and flat HREE with negative Eu anomaly. The tectonic setting discriminant diagram log[K2O/Na2O] vs. SiO2; [SiO2/Al2O3] vs. log[K2O/Na2O]; [SiO2/20] - [K2O+Na2O] - [TiO2+Fe2O3+MgO] indicates transitional tectonic setting from an active continental margin to a passive margin. The discriminant function plot indicates quartzose sedimentary provenance, and to some extent, the felsic igneous provenance, derived from weathered granite, gneissic terrain and/or from pre-existing sedimentary terrain. The CIA value indicates low to moderate degree of chemical weathering and the average ICV values suggests immature sediments deposited in tectonically active settings. The A-CN-K diagram indicates that these sediments were generated from source rocks of the upper continental crust.

  3. Maps showing petroleum exploration intensity and production in major Cambrian to Ordovician reservoir rocks in the Anadarko Basin

    USGS Publications Warehouse

    Henry, Mitch; Hester, Tim

    1996-01-01

    The Anadarko basin is a large, deep, two-stage Paleozoic basin (Feinstein, 1981) that is petroleum rich and generally well explored. The Anadarko basin province, a geogrphic area used here mostly for the convenience of mapping and data management, is defined by political boundaries that include the Anadarko basin proper. The boundaries of the province are identical to those used by the U.S. Geological Survey (USGS) in the 1995 National Assessment of United Stated Oil and Gas Resources. The data in this report, also identical to those used in the national assessment, are from several computerized data bases including Nehring Research Group (NRG) Associates Inc., Significant Oil and Gas Fields of the United States (1992); Petroleum Information (PI), Inc., Well History Control System (1991); and Petroleum Information (PI), Inc., Petro-ROM: Production data on CD-ROM (1993). Although generated mostly in response to the national assessment, the data presented here arc grouped differently and arc displayed and described in greater detail. In addition, the stratigraphic sequences discussed may not necessarily correlate with the "plays" of the 1995 national assessment. This report uses computer-generated maps to show drilling intensity, producing wells, major fields, and other geologic information relevant to petroleum exploration and production in the lower Paleozoic part of the Anadarko basin province as defined for the U.S. Geological Survey's 1995 national petroleum assessment. Hydrocarbon accumulations must meet a minimum standard of 1 million barrels of oil (MMBO) or 6 billion cubic feet of gas (BCFG) estimated ultimate recovery to be included in this report as a major field or revoir. Mapped strata in this report include the Upper Cambrian to Lower Ordovician Arbuckle and Low Ordovician Ellenburger Groups, the Middle Ordovician Simpson Group, and the Middle to Upper Ordovician Viola Group.

  4. Biostratigraphy, taxonomic diversity and patterns of morphological evolution of Ordovician acritarchs (organic-walled microphytoplankton) from the northern Gondwana margin in relation to palaeoclimatic and palaeogeographic changes

    NASA Astrophysics Data System (ADS)

    Vecoli, Marco; Le Hérissé, Alain

    2004-10-01

    Acritarchs, the fossilizable, resting cysts of phytoplanktonic algal protists, are the dominant component of marine organic-walled microfossils in the Palaeozoic. The majority of acritarchs show strong similarities with dinoflagellate cysts in morphological and biogeochemical features, as well as distributional patterns in the sediments. The production of these organic-walled microfossils and their distribution and survivorship in the sediments were controlled by differences in ecological tolerances and life cycle (autecology) of the planktonic parent organisms. Calculation of evolutionary rates and development of a detailed diversity curve at specific level, form the basis for discussing the influence of global palaeoenvironmental perturbations on the evolution of organic-walled microphytoplankton in northern Gondwana during latest Cambrian through Ordovician times. The potential of acritarchs for biostratigraphic correlation at the regional scale (northern Gondwana domain) is much improved by our detailed revision of distributional patterns of 245 acritarch taxa. The most important Cambro-Ordovician acritarch bio-events are short periods of diversification, which also correspond to introduction of morphological innovations, observed in latest Cambrian and earliest Tremadoc, late Tremadoc, early Arenig, basal Llanvirn, and latest Ashgill, and an important extinction phase in the early Caradoc. Overall, acritarch diversity increased from the basal Ordovician up to the middle Llanvirn, then declined in the early and middle Caradoc. During Ashgill times, the assemblages are poorly diversified at the generic level as a result of a combined effect of sea level drawdown and onset of glacial conditions, but no major extinction event is observed in connection with the end-Ordovician biotic crisis. The peak in acritarch diversity during Middle Ordovician times appears to be correlated to maximum spread of palaeogeographical assembly. Acritarch dynamics appear largely

  5. Deep brain stimulation effects in dystonia: time course of electrophysiological changes in early treatment.

    PubMed

    Ruge, Diane; Tisch, Stephen; Hariz, Marwan I; Zrinzo, Ludvic; Bhatia, Kailash P; Quinn, Niall P; Jahanshahi, Marjan; Limousin, Patricia; Rothwell, John C

    2011-08-15

    Deep brain stimulation to the internal globus pallidus is an effective treatment for primary dystonia. The optimal clinical effect often occurs only weeks to months after starting stimulation. To better understand the underlying electrophysiological changes in this period, we assessed longitudinally 2 pathophysiological markers of dystonia in patients prior to and in the early treatment period (1, 3, 6 months) after deep brain stimulation surgery. Transcranial magnetic stimulation was used to track changes in short-latency intracortical inhibition, a measure of excitability of GABA(A) -ergic corticocortical connections and long-term potentiation-like synaptic plasticity (as a response to paired associative stimulation). Deep brain stimulation remained on for the duration of the study. Prior to surgery, inhibition was reduced and plasticity increased in patients compared with healthy controls. Following surgery and commencement of deep brain stimulation, short-latency intracortical inhibition increased toward normal levels over the following months with the same monotonic time course as the patients' clinical benefit. In contrast, synaptic plasticity changed rapidly, following a nonmonotonic time course: it was absent early (1 month) after surgery, and then over the following months increased toward levels observed in healthy individuals. We postulate that before surgery preexisting high levels of plasticity form strong memories of dystonic movement patterns. When deep brain stimulation is turned on, it disrupts abnormal basal ganglia signals, resulting in the absent response to paired associative stimulation at 1 month. Clinical benefit is delayed because engrams of abnormal movement persist and take time to normalize. Our observations suggest that plasticity may be a driver of long-term therapeutic effects of deep brain stimulation in dystonia. Copyright © 2011 Movement Disorder Society.

  6. Saline-water resources of Texas

    USGS Publications Warehouse

    Winslow, Allen George; Kister, Lester Ray

    1956-01-01

    Most of the aquifers in Texas contain saline water in some parts, and a few are capable of producing large quantities of saline water. Of the early Paleozoic formations, the Hickory sandstone member of the Riley formation of Cambrian age and the Ellenburger group of Ordovician age are potential sources of small to moderate supplies of saline water in parts of central and west-central Texas.

  7. Neighborhood Poverty Impacts Children's Physical Health and Well-Being over Time: Evidence from the Early Development Instrument

    ERIC Educational Resources Information Center

    Cushon, Jennifer A.; Vu, Lan T. H.; Janzen, Bonnie L.; Muhajarine, Nazeem

    2011-01-01

    Research Findings: The purpose of this study was to investigate how neighborhoods and neighborhood socioeconomic disadvantage impact school readiness over time. School readiness was measured using the Early Development Instrument (EDI) for 3 populations of kindergartners in 2001, 2003, and 2005 in Saskatoon, Saskatchewan, Canada. EDI results…

  8. A three-dimensional simulation of transition and early turbulence in a time-developing mixing layer

    NASA Technical Reports Server (NTRS)

    Cain, A. B.; Reynolds, W. C.; Ferziger, J. H.

    1981-01-01

    The physics of the transition and early turbulence regimes in the time developing mixing layer was investigated. The sensitivity of the mixing layer to the disturbance field of the initial condition is considered. The growth of the momentum thickness, the mean velocity profile, the turbulence kinetic energy, the Reynolds stresses, the anisotropy tensor, and particle track pictures of computations are all examined in an effort to better understand the physics of these regimes. The amplitude, spectrum shape, and random phases of the initial disturbance field were varied. A scheme of generating discrete orthogonal function expansions on some nonuniform grids was developed. All cases address the early or near field of the mixing layer. The most significant result shows that the secondary instability of the mixing layer is produced by spanwise variations in the straining field of the primary vortex structures.

  9. The risk of early mortality of polytrauma patients associated to ISS, NISS, APACHE II values and prothrombin time.

    PubMed

    Mica, Ladislav; Rufibach, Kaspar; Keel, Marius; Trentz, Otmar

    2013-01-01

    The early hemodynamic normalization of polytrauma patients may lead to better survival outcomes. The aim of this study was to assess the diagnostic quality of trauma and physiological scores from widely used scoring systems in polytrauma patients. In total, 770 patients with ISS > 16 who were admitted to a trauma center within the first 24 hours after injury were included in this retrospective study. The patients were subdivided into three groups: those who died on the day of admission, those who died within the first three days, and those who survived for longer than three days. ISS, NISS, APACHE II score, and prothrombin time were recorded at admission. The descriptive statistics for early death in polytrauma patients who died on the day of admission, 1-3 days after admission, and > 3 days after admission were: ISS of 41.0, 34.0, and 29.0, respectively; NISS of 50.0, 50.0, and 41.0, respectively; APACHE II score of 30.0, 25.0, and 15.0, respectively; and prothrombin time of 37.0%, 56.0%, and 84%, respectively. These data indicate that prothrombin time (AUC: 0.89) and APACHE II (AUC: 0.88) have the greatest prognostic utility for early death. The estimated densities of the scores may suggest a direction for resuscitative procedures in polytrauma patients. "Retrospektive Analysen in der Chirurgischen Intensivmedizin"StV01-2008.

  10. Hypothermic machine perfusion permits extended cold ischemia times with improved early graft function.

    PubMed

    Guy, Alison; McGrogan, Damian; Inston, Nicholas; Ready, Andrew

    2015-04-01

    The logistics of deceased-donor renal transplants are largely affected by cold ischemia time. However, to attain successful outcomes, other issues must be considered. Extending cold ischemia time to accommodate these issues would be valuable. We investigated the role of hypothermic machine perfusion to extend cold ischaemia time. Deceased-donor kidneys were allocated to a storage method, depending on predicted time to operation. Kidneys to be transplanted from 8:00 AM to 8:00 PM in the transplant room remained in static cold storage. If predicted operating time was out of hours, the kidney was transferred to hypothermic machine perfusion and transplanted at the earliest opportunity on the dedicated transplant list. There were 74 kidneys transplanted from hypothermic machine perfusion and 101 kidneys from static cold storage. Median cold ischemia time was 23.85 hours in the hypothermic machine perfusion group, compared with 13 hours in the static cold storage group (P ≤ .0001). There were 20 kidneys (27%) from hypothermic machine perfusion that had delayed graft function, compared with 47 kidneys (47%) in the static cold storage group (P = .012). There were no other significant differences in graft or postoperative complications. This study demonstrated that improved early graft outcomes can be achieved following longer cold ischemia time by using hypothermic machine perfusion rather than static cold storage. This effect is likely multifactorial including the inherent effects of hypothermic machine perfusion, improved recipient preparation, and possibly better perioperative conditions.

  11. Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas.

    PubMed

    Vannier, J; García-Bellido, D C; Hu, S-X; Chen, A-L

    2009-07-22

    Exceptional fossil specimens with preserved soft parts from the Maotianshan Shale (ca 520 Myr ago) and the Burgess Shale (505 Myr ago) biotas indicate that the worldwide distributed bivalved arthropod Isoxys was probably a non-benthic visual predator. New lines of evidence come from the functional morphology of its powerful prehensile frontal appendages that, combined with large spherical eyes, are thought to have played a key role in the recognition and capture of swimming or epibenthic prey. The swimming and steering of this arthropod was achieved by the beating of multiple setose exopods and a flap-like telson. The appendage morphology of Isoxys indicates possible phylogenetical relationships with the megacheirans, a widespread group of assumed predator arthropods characterized by a pre-oral 'great appendage'. Evidence from functional morphology and taphonomy suggests that Isoxys was able to migrate through the water column and was possibly exploiting hyperbenthic niches for food. Although certainly not unique, the case of Isoxys supports the idea that off-bottom animal interactions such as predation, associated with complex feeding strategies and behaviours (e.g. vertical migration and hunting) were established by the Early Cambrian. It also suggests that a prototype of a pelagic food chain had already started to build-up at least in the lower levels of the water column.

  12. Very early reaction intermediates detected by microsecond time scale kinetics of cytochrome cd1-catalyzed reduction of nitrite.

    PubMed

    Sam, Katharine A; Strampraad, Marc J F; de Vries, Simon; Ferguson, Stuart J

    2008-10-10

    Paracoccus pantotrophus cytochrome cd(1) is a nitrite reductase found in the periplasm of many denitrifying bacteria. It catalyzes the reduction of nitrite to nitric oxide during the denitrification part of the biological nitrogen cycle. Previous studies of early millisecond intermediates in the nitrite reduction reaction have shown, by comparison with pH 7.0, that at the optimum pH, approximately pH 6, the earliest intermediates were lost in the dead time of the instrument. Access to early time points (approximately 100 micros) through use of an ultra-rapid mixing device has identified a spectroscopically novel intermediate, assigned as the Michaelis complex, formed from reaction of fully reduced enzyme with nitrite. Spectroscopic observation of the subsequent transformation of this species has provided data that demand reappraisal of the general belief that the two subunits of the enzyme function independently.

  13. Later Education Start Times in Adolescence: Time for Change

    ERIC Educational Resources Information Center

    Kelley, Paul; Lee, Clark

    2015-01-01

    School start times for adolescents in the United States are typically too early to be healthy for this age group. There is significant evidence from the research literature that early starts have serious negative impacts on students. In particular, early education start times in adolescence cause chronic sleep deprivation, which damages both…

  14. Influences of spawning timing, water temperature, and climatic warming on early life history phenology in western Alaska sockeye salmon

    USGS Publications Warehouse

    Sparks, Morgan M.; Falke, Jeffrey A.; Quinn, Thomas P.; Adkison, Milo D.; Schindler, Daniel E.; Bartz, Krista K.; Young, Daniel B.; Westley, Peter A. H.

    2018-01-01

    We applied an empirical model to predict hatching and emergence timing for 25 western Alaska sockeye salmon (Oncorhynchus nerka) populations in four lake-nursery systems to explore current patterns and potential responses of early life history phenology to warming water temperatures. Given experienced temperature regimes during development, we predicted hatching to occur in as few as 58 d to as many as 260 d depending on spawning timing and temperature. For a focal lake spawning population, our climate-lake temperature model predicted a water temperature increase of 0.7 to 1.4 °C from 2015 to 2099 during the incubation period, which translated to a 16 d to 30 d earlier hatching timing. The most extreme scenarios of warming advanced development by approximately a week earlier than historical minima and thus climatic warming may lead to only modest shifts in phenology during the early life history stage of this population. The marked variation in the predicted timing of hatching and emergence among populations in close proximity on the landscape may serve to buffer this metapopulation from climate change.

  15. The 2014 Mw 6.0 Napa Earthquake, California: Observations from Real-time GPS-enhanced Earthquake Early Warning

    NASA Astrophysics Data System (ADS)

    Johanson, I. A.; Grapenthin, R.; Allen, R. M.

    2014-12-01

    Recently, progress has been made to demonstrate feasibility and benefits of including real-time GPS (rtGPS) in earthquake early warning and rapid response systems. While most concepts have yet to be integrated into operational environments, the Berkeley Seismological Laboratory is currently running an rtGPS based finite fault inversion scheme in true real-time, which is triggered by the seismic-based ShakeAlert system and then sends updated earthquake alerts to a test receiver. The Geodetic Alarm System (G-larmS) was online and responded to the 2014 Mw6.0 South Napa earthquake in California. We review G-larmS' performance during this event and for 13 aftershocks, and we present rtGPS observations and real-time modeling results for the main shock. The first distributed slip model and a magnitude estimate of Mw5.5 were available 24 s after the event origin time, which could be reduced to 14 s after a bug fix (~8 s S-wave travel time, ~6 s data latency). The system continued to re-estimate the magnitude once every second: it increased to Mw5.9 3 s after the first alert and stabilized at Mw5.8 after 15 s. G-larmS' solutions for the subsequent small magnitude aftershocks demonstrate that Mw~6.0 is the current limit for alert updates to contribute back to the seismic-based early warning system.

  16. Evidence for hot Mississippi Valley-type brines in the Reelfoot Rift complex, south-central United States, in Late Pennsylvanian-Early Permian

    USGS Publications Warehouse

    Leach, D.L.; Apodaca, L.E.; Repetski, J.E.; Powell, J.W.; Rowan, E.L.

    1997-01-01

    Petrographic and fluid inclusion studies of sparry dolomite cement from Upper Cambrian to Lower Ordovician rocks and conodont thermal-alteration indices provide evidence that hot mississippi valley-type brines were once present in the Reelfoot Rift complex. The cathodoluminescent microstratigraphy of sparry dolomite cement in the Reelfoot Rift resembles that of sparry dolomite cement associated with widespread mississippi valley-type deposition in the Ozark region. If correlative cathodoluminescent zones in the sparry dolomite from the Ozark and Reelfoot Rift regions indicate broadly contemporaneous dolomite deposition, then the results show that the Ozark MVT-type hydrothermal system extended into the Reelfoot region and onto the western flank of the Nashville Dome. Independent evidence supports migration of MVT-type brines into the Ozark region from the Reelfoot Rift complex in late Paleozoic time.

  17. Early Radiosurgery Improves Hearing Preservation in Vestibular Schwannoma Patients With Normal Hearing at the Time of Diagnosis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Akpinar, Berkcan; Mousavi, Seyed H., E-mail: mousavish@upmc.edu; McDowell, Michael M.

    Purpose: Vestibular schwannomas (VS) are increasingly diagnosed in patients with normal hearing because of advances in magnetic resonance imaging. We sought to evaluate whether stereotactic radiosurgery (SRS) performed earlier after diagnosis improved long-term hearing preservation in this population. Methods and Materials: We queried our quality assessment registry and found the records of 1134 acoustic neuroma patients who underwent SRS during a 15-year period (1997-2011). We identified 88 patients who had VS but normal hearing with no subjective hearing loss at the time of diagnosis. All patients were Gardner-Robertson (GR) class I at the time of SRS. Fifty-seven patients underwent earlymore » (≤2 years from diagnosis) SRS and 31 patients underwent late (>2 years after diagnosis) SRS. At a median follow-up time of 75 months, we evaluated patient outcomes. Results: Tumor control rates (decreased or stable in size) were similar in the early (95%) and late (90%) treatment groups (P=.73). Patients in the early treatment group retained serviceable (GR class I/II) hearing and normal (GR class I) hearing longer than did patients in the late treatment group (serviceable hearing, P=.006; normal hearing, P<.0001, respectively). At 5 years after SRS, an estimated 88% of the early treatment group retained serviceable hearing and 77% retained normal hearing, compared with 55% with serviceable hearing and 33% with normal hearing in the late treatment group. Conclusions: SRS within 2 years after diagnosis of VS in normal hearing patients resulted in improved retention of all hearing measures compared with later SRS.« less

  18. Short-Term responses of breeding birds of grassland and early successional habitat to timing of haying in Northwestern Arkansas

    USGS Publications Warehouse

    Luscier, J.D.; Thompson, W.L.

    2009-01-01

    In 2003, we evaluated nest survival and density of the Dickcissel (Spiza americana), Eastern Meadowlark (Sturnella magna), Field Sparrow (Spizella pusilla), and Red-winged Blackbird (Agelaius phoeniceus) in four unhayed, two early-hayed (26-31 May) and three late-hayed (17-25 June) fields in northwestern Arkansas. Rope dragging and observations revealed 89 nests. Daily nest-survival rates (SE) prior to haying ranged from 0.94 (0.03) to 0.97 (0.02). Early haying affected both nest-survival rates and bird densities negatively, whereas late haying had minimal effects. Fifteen nests in hayed portions of early-hayed fields were destroyed, whereas only 2 of 52 nests were affected by late haying. Density was at least 0.98 birds ha-1 higher in unhayed than in early-hayed fields and 1.03 birds ha-1 higher in late-hayed than in early-hayed fields. In northwestern Arkansas, postponing haying until mid- to late June would allow time for nestlings to fledge, would have little effect on bird densities, and would affect hay nutrition and regrowth minimally. ?? The Cooper Ornithological Society, 2009.

  19. Health-related effects of early part-time sick leave due to musculoskeletal disorders: a randomized controlled trial.

    PubMed

    Shiri, Rahman; Kausto, Johanna; Martimo, Kari-Pekka; Kaila-Kangas, Leena; Takala, Esa-Pekka; Viikari-Juntura, Eira

    2013-01-01

    Previously we reported that early part-time sick leave enhances return to work (RTW) among employees with musculoskeletal disorders (MSD). This paper assesses the health-related effects of this intervention. Patients aged 18-60 years who were unable to perform their regular work due to MSD were randomized to part- or full-time sick leave groups. In the former, workload was reduced by halving working time. Using validated questionnaires, we assessed pain intensity and interference with work and sleep, region-specific disability due to MSD, self-rated general health, health-related quality of life (measured via EuroQol), productivity loss, depression, and sleep disturbance at baseline, 1, 3, 8, 12, and 52 weeks. We analyzed the repeated measures data (171-356 observations) with the generalized estimating equation approach. The intervention (part-time sick leave) and control (full-time sick leave) groups did not differ with regard to pain intensity, pain interference with work and sleep, region-specific disability, productivity loss, depression, or sleep disturbance. The intervention group reported better self-rated general health (adjusted P=0.07) and health-related quality of life (adjusted P=0.02) than the control group. In subgroup analyses, the intervention was more effective among the patients whose current problem began occurring <6 weeks before baseline and those with ≤30% productivity loss at baseline. Our findings showed that part-time sick leave did not exacerbate pain-related symptoms and functional disability, but improved self-rated general health and health-related quality of life in the early stage of work disability due to MSD.

  20. Real-time 3-D space numerical shake prediction for earthquake early warning

    NASA Astrophysics Data System (ADS)

    Wang, Tianyun; Jin, Xing; Huang, Yandan; Wei, Yongxiang

    2017-12-01

    In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.

  1. Are the early predictors of long-term work absence following injury time dependent? Results from the Prospective Outcomes of Injury Study

    PubMed Central

    Lilley, Rebbecca; Davie, Gabrielle; Derrett, Sarah

    2017-01-01

    Objectives Few studies examine the influence of early predictors of work absence beyond 12 months following injury or the time-dependent relative importance of these factors. This study aimed to identify the most important sociodemographic, occupational, health, lifestyle and injury predictors of work absence at 12 and 24 months following injury and to examine changes in the relative importance of these over time. Design Prospective cohort study. Setting The Prospective Outcomes of Injury Study, New Zealand. Participants 2626 injured New Zealand workers aged 18–64 years were identified from the Prospective Outcomes of Injury Study recruited form New Zealand’s monopoly injury compensation provider injury claims register: 2092 completed the 12-month interview (80% follow-up) and 2082 completed the 24-month interview (79% follow-up). Primary and secondary outcomes measures The primary outcomes of interest was absence from work at the time of the 12-month and 24-month follow-up interviews. Results Using modified Poisson regression to estimate relative risks, important groups of workers were identified at increased risk of work absence at both 12 and 24 months: males, low-income workers, trade/manual workers, temporary employees, those reporting two or more comorbidities and those experiencing a work-related injury. Important factors unique to predicting work absence at 12 months included financial insecurity, fixed-term employment and long weekly hours worked; unique factors at 24 months included job dissatisfaction, long weekly days worked, a prior injury and sustaining an injury that was perceived to be a threat to life. Conclusions Important early predictors of work absence at 12 or 24 months following injury are multidimensional and have a time dependent pattern. A consistent set of predictors was, however, present at both time periods that are prime for early intervention. Understanding the multidimensional, time-dependent patterns of early predictors of

  2. Socio-economic status and time trends associated with early ART initiation following primary HIV infection in Montreal, Canada: 1996 to 2015.

    PubMed

    Mehraj, Vikram; Cox, Joseph; Lebouché, Bertrand; Costiniuk, Cecilia; Cao, Wei; Li, Taisheng; Ponte, Rosalie; Thomas, Réjean; Szabo, Jason; Baril, Jean-Guy; Trottier, Benoit; Côté, Pierre; LeBlanc, Roger; Bruneau, Julie; Tremblay, Cécile; Routy, Jean-Pierre

    2018-02-01

    Guidelines regarding antiretroviral therapy (ART) initiation in HIV infection have varied over time, with the 2015 World Health Organization recommendation suggesting ART initiation at the time of diagnosis regardless of CD4 T-cell counts. Herein, we investigated the influence of socio-demographic and clinical factors in addition to time trends on early ART initiation among participants of the Montreal Primary HIV Infection Study. The Montreal Primary HIV Infection Study is a prospective cohort established in three community medical centres (CMCs) and two university medical centres (UMCs). Recently diagnosed HIV-infected adults were categorized as receiving early (vs. delayed) ART if ART was initiated within 180 days of the baseline visit. Associations between early ART initiation and socio-demographic, socio-economic and behavioural information were examined. Independent associations of factors linked with early ART initiation were determined using multivariable binary logistic regression analysis. A total of 348 participants had a documented date of HIV acquisition of <180 days. The median interquartile range (IQR) age of participants was 35 (28; 42) years and the majority were male (96%), having paid employment (63%), men who have sex with men (MSM) (78%) and one to four sexual partners in the last three months (70%). Participants presented with a median IQR HIV plasma viral load of 4.6 (3.7; 5.3) log 10 copies/ml, CD4 count of 510 (387; 660) cells/μl and were recruited in CMCs (52%) or UMCs (48%). Early ART initiation was observed in 47% of the participants and the trend followed a V-shaped curve with peaks in 1996 to 1997 (89%) and 2013 to 2015 (88%) with a dip in 2007 to 2009 (22%). Multivariable analyses showed that having a paid employment adjusted odds ratio (aOR: 2.43; 95% CI: 1.19, 4.95), lower CD4 count (aOR per 50 cell increase: 0.93; 95% CI: 0.87, 0.99) and care at UMCs (aOR: 2.03; 95% CI: 1.06 to 3.90) were independently associated with early ART

  3. Time well spent: the duration of foster care and early adult labor market, educational, and health outcomes.

    PubMed

    Fallesen, Peter

    2013-12-01

    Individuals who spent time in foster care as children fare on average worse than non-placed peers in early adult life. Recent research on the effect of foster care placement on early adult life outcomes provides mixed evidence. Some studies suggest negative effects of foster care placement on early adult outcomes, others find null effects. This study shows that differences in the average duration of foster care stays explain parts of these discordant findings and then test how foster care duration shapes later life outcomes using administrative data on 7220 children. The children experienced different average durations of foster care because of differences in exposure to a reform. Later born cohorts spent on average 3 months longer in foster care than earlier born cohorts. Isolating exogenous variation in duration of foster care, the study finds positive effects of increased duration of foster care on income and labor market participation. Copyright © 2013 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

  4. Time development in the early history of social networks: link stabilization, group dynamics, and segregation.

    PubMed

    Bruun, Jesper; Bearden, Ian G

    2014-01-01

    Studies of the time development of empirical networks usually investigate late stages where lasting connections have already stabilized. Empirical data on early network history are rare but needed for a better understanding of how social network topology develops in real life. Studying students who are beginning their studies at a university with no or few prior connections to each other offers a unique opportunity to investigate the formation and early development of link patterns and community structure in social networks. During a nine week introductory physics course, first year physics students were asked to identify those with whom they communicated about problem solving in physics during the preceding week. We use these students' self reports to produce time dependent student interaction networks. We investigate these networks to elucidate possible effects of different student attributes in early network formation. Changes in the weekly number of links show that while roughly half of all links change from week to week, students also reestablish a growing number of links as they progress through their first weeks of study. Using the Infomap community detection algorithm, we show that the networks exhibit community structure, and we use non-network student attributes, such as gender and end-of-course grade to characterize communities during their formation. Specifically, we develop a segregation measure and show that students structure themselves according to gender and pre-organized sections (in which students engage in problem solving and laboratory work), but not according to end-of-coure grade. Alluvial diagrams of consecutive weeks' communities show that while student movement between groups are erratic in the beginning of their studies, they stabilize somewhat towards the end of the course. Taken together, the analyses imply that student interaction networks stabilize quickly and that students establish collaborations based on who is immediately

  5. Famines in Africa: is early warning early enough?

    PubMed Central

    Kim, Jeeyon Janet; Guha-Sapir, Debarati

    2012-01-01

    Following the second Sahelian famine in 1984–1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the Sahel, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response. PMID:22745628

  6. Famines in Africa: is early warning early enough?

    PubMed

    Kim, Jeeyon Janet; Guha-Sapir, Debarati

    2012-01-01

    Following the second Sahelian famine in 1984-1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the Sahel, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response.

  7. Time-resolved metabolomics analysis of individual differences during the early stage of lipopolysaccharide-treated rats.

    PubMed

    Dai, Die; Gao, Yiqiao; Chen, Jiaqing; Huang, Yin; Zhang, Zunjian; Xu, Fengguo

    2016-10-03

    Lipopolysaccharide (LPS) can lead to uncontrollable cytokine production and eventually cause fatal sepsis syndrome. Individual toxicity difference of LPS has been widely reported. In our study we observed that two thirds of the rats (24/36) died at a given dose of LPS, while the rest (12/36) survived. Tracking the dynamic metabolic change in survival and non-survival rats in the early stage may reveal new system information to understand the inter-individual variation in response to LPS. As the time-resolved datasets are very complex and no single method can elucidate the problem clearly and comprehensively, the static and dynamic metabolomics methods were employed in combination as cross-validation. Intriguingly, some common results have been observed. Lipids were the main different metabolites between survival and non-survival rats in pre-dose serum and in the early stage of infection with LPS. The LPS treatment led to S-adenosly-methionine and total cysteine individual difference in early stage, and subsequent significant perturbations in energy metabolism and oxidative stress. Furthermore, cytokine profiles were analyzed to identify potential biological associations between cytokines and specific metabolites. Our collective findings may provide some heuristic guidance for elucidating the underlying mechanism of individual difference in LPS-mediated disease.

  8. On the use of variability time-scales as an early classifier of radio transients and variables

    NASA Astrophysics Data System (ADS)

    Pietka, M.; Staley, T. D.; Pretorius, M. L.; Fender, R. P.

    2017-11-01

    We have shown previously that a broad correlation between the peak radio luminosity and the variability time-scales, approximately L ∝ τ5, exists for variable synchrotron emitting sources and that different classes of astrophysical sources occupy different regions of luminosity and time-scale space. Based on those results, we investigate whether the most basic information available for a newly discovered radio variable or transient - their rise and/or decline rate - can be used to set initial constraints on the class of events from which they originate. We have analysed a sample of ≈800 synchrotron flares, selected from light curves of ≈90 sources observed at 5-8 GHz, representing a wide range of astrophysical phenomena, from flare stars to supermassive black holes. Selection of outbursts from the noisy radio light curves has been done automatically in order to ensure reproducibility of results. The distribution of rise/decline rates for the selected flares is modelled as a Gaussian probability distribution for each class of object, and further convolved with estimated areal density of that class in order to correct for the strong bias in our sample. We show in this way that comparing the measured variability time-scale of a radio transient/variable of unknown origin can provide an early, albeit approximate, classification of the object, and could form part of a suite of measurements used to provide early categorization of such events. Finally, we also discuss the effect scintillating sources will have on our ability to classify events based on their variability time-scales.

  9. Early-life predictors of leisure-time physical inactivity in midadulthood: findings from a prospective British birth cohort.

    PubMed

    Pinto Pereira, Snehal M; Li, Leah; Power, Chris

    2014-12-01

    Much adult physical inactivity research ignores early-life factors from which later influences may originate. In the 1958 British birth cohort (followed from 1958 to 2008), leisure-time inactivity, defined as activity frequency of less than once a week, was assessed at ages 33, 42, and 50 years (n = 12,776). Early-life factors (at ages 0-16 years) were categorized into 3 domains (i.e., physical, social, and behavioral). We assessed associations of adult inactivity 1) with factors within domains, 2) with the 3 domains combined, and 3) allowing for adult factors. At each age, approximately 32% of subjects were inactive. When domains were combined, factors associated with inactivity (e.g., at age 50 years) were prepubertal stature (5% lower odds per 1-standard deviation higher height), hand control/coordination problems (14% higher odds per 1-point increase on a 4-point scale), cognition (10% lower odds per 1-standard deviation greater ability), parental divorce (21% higher odds), institutional care (29% higher odds), parental social class at child's birth (9% higher odds per 1-point reduction on a 4-point scale), minimal parental education (13% higher odds), household amenities (2% higher odds per increase (representing poorer amenities) on a 19-point scale), inactivity (8% higher odds per 1-point reduction in activity on a 4-point scale), low sports aptitude (13% higher odds), and externalizing behaviors (i.e., conduct problems) (5% higher odds per 1-standard deviation higher score). Adjustment for adult covariates weakened associations slightly. Factors from early life were associated with adult leisure-time inactivity, allowing for early identification of groups vulnerable to inactivity. © The Author 2014. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  10. Early-Time Symmetry Tuning in the Presence of Cross-Beam Energy Transfer in ICF Experiments on the National Ignition Facility

    DOE PAGES

    Dewald, E. L.; Milovich, J. L.; Michel, P.; ...

    2013-12-01

    At the National Ignition Facility (NIF) we have successfully tuned the early time (~2 ns) lowest order Legendre mode (P 2) of the incoming radiation drive asymmetry of indirectly driven ignition capsule implosions by varying the inner power cone fraction. The measured P 2/P 0 sensitivity vs come fraction is similar to calculations, but a significant -15 to -20% P 2/P 0 offset was observed. This can be explained by a considerable early time laser energy transfer from the outer to the inner beams during the laser burn-through of the Laser Entrance Hole (LEH) windows and hohlraum fill gas whenmore » the LEH plasma is still dense and relatively cold.« less

  11. Integrated SeismoGeodetic Systsem with High-Resolution, Real-Time GNSS and Accelerometer Observation For Earthquake Early Warning Application.

    NASA Astrophysics Data System (ADS)

    Passmore, P. R.; Jackson, M.; Zimakov, L. G.; Raczka, J.; Davidson, P.

    2014-12-01

    The key requirements for Earthquake Early Warning and other Rapid Event Notification Systems are: Quick delivery of digital data from a field station to the acquisition and processing center; Data integrity for real-time earthquake notification in order to provide warning prior to significant ground shaking in the given target area. These two requirements are met in the recently developed Trimble SG160-09 SeismoGeodetic System, which integrates both GNSS and acceleration measurements using the Kalman filter algorithm to create a new high-rate (200 sps), real-time displacement with sufficient accuracy and very low latency for rapid delivery of the acquired data to a processing center. The data acquisition algorithm in the SG160-09 System provides output of both acceleration and displacement digital data with 0.2 sec delay. This is a significant reduction in the time interval required for real-time transmission compared to data delivery algorithms available in digitizers currently used in other Earthquake Early Warning networks. Both acceleration and displacement data are recorded and transmitted to the processing site in a specially developed Multiplexed Recording Format (MRF) that minimizes the bandwidth required for real-time data transmission. In addition, a built in algorithm calculates the τc and Pd once the event is declared. The SG160-09 System keeps track of what data has not been acknowledged and re-transmits the data giving priority to current data. Modified REF TEK Protocol Daemon (RTPD) receives the digital data and acknowledges data received without error. It forwards this "good" data to processing clients of various real-time data processing software including Earthworm and SeisComP3. The processing clients cache packets when a data gap occurs due to a dropped packet or network outage. The cache packet time is settable, but should not exceed 0.5 sec in the Earthquake Early Warning network configuration. The rapid data transmission algorithm was tested

  12. The effect of cerebral palsy on arithmetic accuracy is mediated by working memory, intelligence, early numeracy, and instruction time.

    PubMed

    Jenks, Kathleen M; de Moor, Jan; van Lieshout, Ernest C D M; Maathuis, Karel G B; Keus, Inge; Gorter, Jan Willem

    2007-01-01

    The development of addition and subtraction accuracy was assessed in first graders with cerebral palsy (CP) in both mainstream (16) and special education (41) and a control group of first graders in mainstream education (16). The control group out-performed the CP groups in addition and subtraction accuracy and this difference could not be fully explained by differences in intelligence. Both CP groups showed evidence of working memory deficits. The three groups exhibited different developmental patterns in the area of early numeracy skills. Children with CP in special education were found to receive less arithmetic instruction and instruction time was positively related to arithmetic accuracy. Structural equation modeling revealed that the effect of CP on arithmetic accuracy is mediated by intelligence, working memory, early numeracy, and instruction time.

  13. Statistical process control: A feasibility study of the application of time-series measurement in early neurorehabilitation after acquired brain injury.

    PubMed

    Markovic, Gabriela; Schult, Marie-Louise; Bartfai, Aniko; Elg, Mattias

    2017-01-31

    Progress in early cognitive recovery after acquired brain injury is uneven and unpredictable, and thus the evaluation of rehabilitation is complex. The use of time-series measurements is susceptible to statistical change due to process variation. To evaluate the feasibility of using a time-series method, statistical process control, in early cognitive rehabilitation. Participants were 27 patients with acquired brain injury undergoing interdisciplinary rehabilitation of attention within 4 months post-injury. The outcome measure, the Paced Auditory Serial Addition Test, was analysed using statistical process control. Statistical process control identifies if and when change occurs in the process according to 3 patterns: rapid, steady or stationary performers. The statistical process control method was adjusted, in terms of constructing the baseline and the total number of measurement points, in order to measure a process in change. Statistical process control methodology is feasible for use in early cognitive rehabilitation, since it provides information about change in a process, thus enabling adjustment of the individual treatment response. Together with the results indicating discernible subgroups that respond differently to rehabilitation, statistical process control could be a valid tool in clinical decision-making. This study is a starting-point in understanding the rehabilitation process using a real-time-measurements approach.

  14. Tectonics of Precambrian basement along the Pacific margin of Antarctica and relation to western North America

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goodge, J.W.; Hansen, V.L.; Walker, N.W.

    1993-02-01

    High-grade metamorphic rocks of the Precambrian Nimrod Group (NG) constitute one of few cratonal basement exposures in the Transantarctic Mountains. These rocks represent an outlier of the East Antarctic craton, evolved as part of Gondwana and pre-Gondwana (Rodinia) supercontinents. Despite pervasive, high-strain ductile deformation at T [>=] 650 C, they preserve petrologic and geochronologic evidence of an earlier history. Sm-Nd model ages from several NG lithologies, including that of a [approximately]1.7 Ga orthogneiss, range from about 2.7--2.9 Ga; these ages reflect both sedimentary and magmatic derivation from Archean crust. Individual detrital zircon U-Pb ages (about 1.7--2.6 Ga) from NG quartzitesmore » indicate clastic input from Archean to Paleoproterozoic source terrains. The Sm-Nd and U-Pb ages are reminiscent of both the Yavapai-Mazatzal (1.6--1.8 Ga) and Wyoming (> 2.5 Ga) provinces in western North America. U-Pb ages from syn-tectonic metaigneous and pelitic NG tectonites indicate that this basement complex was re-worked by the major ductile deformation in latest neoproterozoic to Early Cambrian time. Supracrustal assemblages that lie outboard of the Nimrod craton include Neoproterozoic graywacke, impure carbonate, and minor mafic volcanics (Beardmore Group), and Cambrian to Lower Ordovician carbonate and siliciclastic rocks (Byrd Group). Neoproterozoic ([approximately]750 Ma) rifting along the proto-Pacific margin of East Antarctica is reflected by deposition of Beardmore turbidites and coeval mafic magmatism. Latest Neoproterozoic to early Paleozoic orogenesis occurred along a left-oblique convergent plate margin of East Antarctica is reflected by deposition of Beardmore turbidites and coeval mafic magmatism.« less

  15. Understanding Predictors of Early Antenatal Care Initiation in Relationship to Timing of HIV Diagnosis in South Africa.

    PubMed

    Nattey, Cornelius; Jinga, Nelly; Mongwenyana, Constance; Mokhele, Idah; Mohomi, Given; Fox, Matthew P; Onoya, Dorina

    2018-06-01

    Effective prevention of mother-to-child transmission benefits from early presentation to antenatal care (ANC). It is, however, unclear whether a previous HIV diagnosis results in earlier initiation of ANC. We estimated the probability of early ANC initiation among women with a previous HIV-positive diagnosis compared to those who first tested for HIV during ANC and explored determinants of early ANC among HIV-positive women. We conducted an analysis of a cross-sectional survey among 411 HIV-positive adult (>18 years) women who gave birth at midwife obstetrics units in Gauteng between October 2016 and May 2017. Predictors of early ANC (defined as initiating ANC before or at 14 weeks of gestation) were assessed by multivariate log-binomial regression model. Overall, 51% (210) were diagnosed during pregnancy with 89% (188) initiating antiretroviral therapy on the same day of diagnosis. There was no meaningful difference in the timing of ANC initiation between women with previous HIV diagnosis [adjusted risk ratio (aRR) = 1.2; 95% confidence interval (95% CI): 0.9-1.7] compared with those diagnosed during pregnancy. Early ANC was predicted by planned pregnancy [aRR = 1.3; 95% CI: 1.1-1.7], parity (>2 children) [aRR = 0.6; 95% CI: 0.2-0.9] compared to not having a child, and tuberculosis diagnosis [aRR = 2.9; 95% CI: 1.4-6.1]. Our results suggest the need for a targeted intervention among HIV-positive women by improving the quality, content and outreach of ANC services to enhance early ANC uptake, and minimize mother-to-child transmission risk.

  16. The origin of animals: Can molecular clocks and the fossil record be reconciled?

    PubMed

    Cunningham, John A; Liu, Alexander G; Bengtson, Stefan; Donoghue, Philip C J

    2017-01-01

    The evolutionary emergence of animals is one of the most significant episodes in the history of life, but its timing remains poorly constrained. Molecular clocks estimate that animals originated and began diversifying over 100 million years before the first definitive metazoan fossil evidence in the Cambrian. However, closer inspection reveals that clock estimates and the fossil record are less divergent than is often claimed. Modern clock analyses do not predict the presence of the crown-representatives of most animal phyla in the Neoproterozoic. Furthermore, despite challenges provided by incomplete preservation, a paucity of phylogenetically informative characters, and uncertain expectations of the anatomy of early animals, a number of Neoproterozoic fossils can reasonably be interpreted as metazoans. A considerable discrepancy remains, but much of this can be explained by the limited preservation potential of early metazoans and the difficulties associated with their identification in the fossil record. Critical assessment of both records may permit better resolution of the tempo and mode of early animal evolution. © 2016 The Authors BioEssays Published by WILEY Periodicals, Inc.

  17. Early-time dynamics of gluon fields in high energy nuclear collisions

    NASA Astrophysics Data System (ADS)

    Chen, Guangyao; Fries, Rainer J.; Kapusta, Joseph I.; Li, Yang

    2015-12-01

    Nuclei colliding at very high energy create a strong, quasiclassical gluon field during the initial phase of their interaction. We present an analytic calculation of the initial space-time evolution of this field in the limit of very high energies using a formal recursive solution of the Yang-Mills equations. We provide analytic expressions for the initial chromoelectric and chromomagnetic fields and for their energy-momentum tensor. In particular, we discuss event-averaged results for energy density and energy flow as well as for longitudinal and transverse pressure of this system. For example, we find that the ratio of longitudinal to transverse pressure very early in the system behaves as pL/pT=-[1 -3/2 a (Qτ ) 2] /[1 -1/a (Qτ ) 2] +O (Qτ ) 4 , where τ is the longitudinal proper time, Q is related to the saturation scales Qs of the two nuclei, and a =ln(Q2/m̂2) with m ̂ a scale to be defined later. Our results are generally applicable if τ ≲1 /Q . As already discussed in a previous paper, the transverse energy flow Si of the gluon field exhibits hydrodynamiclike contributions that follow transverse gradients of the energy density ∇iɛ . In addition, a rapidity-odd energy flow also emerges from the non-Abelian analog of Gauss' law and generates nonvanishing angular momentum of the field. We discuss the space-time picture that emerges from our analysis and its implications for observables in heavy-ion collisions.

  18. Transformation and time-out: The role of alcohol in identity construction among Scottish women in early midlife

    PubMed Central

    Emslie, Carol; Hunt, Kate; Lyons, Antonia

    2015-01-01

    Despite the increase in drinking by women in early midlife, little alcohol research has focused on this group. We explore how alcohol is associated with the construction of gender identities among women aged 30–50 years in the west of Scotland, United Kingdom. We draw on qualitative data from 11 focus groups (five all-female, six mixed-sex) with pre-existing groups of friends and work colleagues in which women and men discuss their drinking behaviours. Analysis demonstrated how alcohol represented a time and space away from paid and unpaid work for women in a range of domestic circumstances, allowing them to relax and unwind. While women used alcohol to construct a range of identities, traditional notions of femininity remained salient (e.g. attention to appearance, drinking ‘girly’ drinks). Drinking enabled women to assert their identity beyond the roles and responsibilities often associated with being a woman in early midlife. For example, some respondents with young children described the transformative effects of excessive drinking which allowed them to return temporarily to a younger, carefree version of themselves. Thus, our data suggest that women's drinking in early midlife revolves around notions of ‘idealised’ femininity but simultaneously represents a way of achieving ‘time out’ from traditional female responsibilities such as caring for others. We consider these findings within a broader social and cultural context including alcohol marketing, domestic roles and motherhood and their implications for health promotion. PMID:25597015

  19. On the origin of optics

    NASA Astrophysics Data System (ADS)

    Parker, Andrew R.

    2011-03-01

    The first optical devices in animals evolved in the Cambrian period. The first reflector known dates from around 508 million years ago (Ma); the first eyes with lenses evolved at around 521 Ma. Consideration of the introduction of vision leads to a hypothesis for the cause of evolution's Big Bang—the Cambrian explosion. Suddenly, and for no obvious reason, the range and variety of life-forms erupted somewhere between 520 and 515 Ma (as limited by of our dating techniques). At no other time in Earth's history there has been such a profusion, such an exuberance, and such an overwhelming diversity in so short time, within one million years. Prior to this Cambrian explosion event, all animals were soft-bodied and mainly worm-like, as they had been for millions of years before that. But during the Cambrian explosion many of the major animal groups on Earth today independently evolved their hard body parts for the first time. Following the appearance of the first trilobites, some animals evolved shells and spines, some with bright colours, to visually warn of their new armour. Others evolved streamlined appearances and swimming oars to advise trilobites that they could not be caught. The Light Switch Theory provides an explanation for what triggered this event—that it was the development of vision (in trilobites); the introduction of optics. Once visual capability arose, it allowed predators to identify prey, triggering an arms race. From here on, vision became a dominant force of evolution and resulted in the eyes and reflecting optics that we have in nature today. This paper provides a summary of the first optical devices to evolve in animals, along with the implications of these in their relevance to the Big Bang of evolution, written for the physical sciences.

  20. Poor sleep quality predicts deficient emotion information processing over time in early adolescence.

    PubMed

    Soffer-Dudek, Nirit; Sadeh, Avi; Dahl, Ronald E; Rosenblat-Stein, Shiran

    2011-11-01

    There is deepening understanding of the effects of sleep on emotional information processing. Emotion information processing is a key aspect of social competence, which undergoes important maturational and developmental changes in adolescence; however, most research in this area has focused on adults. Our aim was to test the links between sleep and emotion information processing during early adolescence. Sleep and facial information processing were assessed objectively during 3 assessment waves, separated by 1-year lags. Data were obtained in natural environments-sleep was assessed in home settings, and facial information processing was assessed at school. 94 healthy children (53 girls, 41 boys), aged 10 years at Time 1. N/A. Facial information processing was tested under neutral (gender identification) and emotional (emotional expression identification) conditions. Sleep was assessed in home settings using actigraphy for 7 nights at each assessment wave. Waking > 5 min was considered a night awakening. Using multilevel modeling, elevated night awakenings and decreased sleep efficiency significantly predicted poor performance only in the emotional information processing condition (e.g., b = -1.79, SD = 0.52, confidence interval: lower boundary = -2.82, upper boundary = -0.076, t(416.94) = -3.42, P = 0.001). Poor sleep quality is associated with compromised emotional information processing during early adolescence, a sensitive period in socio-emotional development.