These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Sequence stratigraphic principles applied to the Miocene Hawthorn Group, west-central Florida  

SciTech Connect

Sequence boundaries for the Miocene Hawthorn Group in the ROMP 20 drill core from Osprey, Sarasota County, FL were generally delineated by lithologic variations recognized from core slabs, thin section analysis, and geophysical logs. At least six depositional sequences representing third order sea level fluctuations were identified. Depositional environments were determined on the basis of the characteristic lithologic constituents including rip-up clasts, pellets, fossils, laminations, burrow, degree of induration, and grain sorting. The sequence boundaries appear to have formed when the rate of the eustatic fall exceeded basin subsidence rates producing a relative sea level fall at a depositional shoreline break. As a result of the basinward facies shift associated with this sequence type, peritidal facies may directly overlie deeper water facies. Subaerial exposure and erosion can be expected. The sequence of facies representing progressively deeper water depositional environments, followed by a progressive shallowing, were present between bounding surfaces. Among the six sequences recognized, four were clearly delineated as representative of regression, subaerial exposure, and subsequent transgression. Two sequences were less clearly defined and probably represent transitional facies which had exposure surfaces developed. Comparison of the petrologically established sequence stratigraphy with published sea level curves resulted in a strong correlation between the number of sequences recognized and the number of coastal on-lap/off-lap cycles depicted for the early to middle Miocene. This correlation suggests that petrologic examination of core slabs, with supplemental thin section data, can provide useful information regarding the recognition of stratigraphic sequences and relative sea level fluctuations, particularly, in situations where seismic data may not be available.

Norton, V.L.; Randazzo, A.F. (Florida Univ., Gainesville, FL (United States). Dept. of Geology)

1993-03-01

2

Natural Arsenic in the Miocene Hawthorn Group, Florida: Wide Ranging Implications for ASR, Phosphate Mining, Private Well  

NASA Astrophysics Data System (ADS)

In order to understand the mineralogical association and distribution of arsenic (As) in the Hawthorn Group we examined in detail the chemical and mineralogical composition of 370 samples that were collected from 16 cores in central Florida. In our study area the Hawthorn group consists primarily of a basal carbonate unit (the Arcadia Formation) and an upper siliciclastic unit (The Peace River Formation). The Peace River Formation contains appreciable amounts of phosphate and is currently being exploited for phosphate ore. Samples were taken for each Formation at intervals of 25ft. In addition to the interval samples we also took samples that contained visible pyrite crystals, iron oxides, green clays, phosphatic and organic material. These additional samples were collected because of their potential of high As concentrations. Arsenic concentrations were determined by hydride generation - atomic fluorescence spectrometry (HG-AFS) after digestion with aqua regia (3:1 HCl and HNO3). The elements Fe, Na, Al, Si, Mg, Ca, S, P, and K were measured on the same solutions by inductively coupled plasma optical emission spectrometry (ICP-OES). The identification of discrete minerals was aided by scanning electron microscopy (SEM) and chemical compositions were obtained by electron-probe microanalyses (EMPA). Our study indicates that the average As concentrations significantly change from 9.0 ppm in the Peace River Formation to 3.0 ppm in the Tampa Member of the Arcadia Formation. As concentrations for all Hawthorn samples vary from 0.07 to 68.98 ppm ( ? = 5.6, ? = 7.1). Our detailed mineralogical and geochemical study demonstrates that: (1) The As in the Hawthorn group varies from the formation to formation and is mostly concentrated in trace minerals, such as pyrite; (2) Concentrations of the As in pyrite crystals can vary drastically from a minimum of 0 ppm to a maximum of 8260 ppm; (3) Pyrite is an unevenly distributed throughout the Hawthorn Group; (4) Phosphate and organic material, clays, and iron oxides contain lower As concentrations contrasted to pyrite; (5) Pyrite occurs in framboidal and euhedral forms. Because phosphorous, arsenic and sulfur are chemically closely related, they often occur together in nature, thus posing a potential problem for the phosphate industry. There have been several occurrences of swine fatalities due to arsenic poisoning as a result of phosphate feed supplements. Information about the concentration, distribution and mineralogical association of naturally occurring As is important, because this is a first step to forecast its behavior during anthropogenic induced physico-chemical changes in the aquifer. Recently, aquifer storage and recovery (ASR) facilities in central Florida reported As concentrations in excess of 100 ? g/L in recovered water. The ASR storage zone is the Suwannee Limestone, which directly underlies the Hawthorn sediments. It is crucial to the future of ASR in this area to understand the source and distribution of arsenic in the overlying Hawthorn Group and the cycling of arsenic in the Florida platform.

Lazareva, O. V.; Pichler, T.

2004-12-01

3

Hawthorn  

MedlinePLUS

... to make liquid extracts, usually with water and alcohol. Dry extracts can be put into capsules and ... Wilkins; 2000:182–191. Hawthorn. Natural Medicines Comprehensive Database Web site. Accessed at www.naturaldatabase.com on ...

4

Hawthorne in Salem  

NSDL National Science Digital Library

During his days as a clerk for the federal government in Salem, Massachusetts, Nathaniel Hawthorne began crafting some of his most notable works. The Hawthorne in Salem site celebrates his life and times in this very unique place. Created by the North Shore Community College in nearby Danvers, the site offers up an interactive timeline of dates from Hawthorne's life. Visitors can browse through six sections, including Life & Times, Literature, and Buildings and Houses. The Maps area is a delight, offering maps of Salem Village, Salem in HawthorneâÂÂs time, as well as Salem today. Accompanying articles also provide riveting insight into Salem around the time of HawthorneâÂÂs birth in 1804. The siteâÂÂs introductory video is also worth a look.

2000-05-01

5

Nathaniel Hawthorne Bicentennial Exhibition  

NSDL National Science Digital Library

Rightly regarded as one of the great figures of American letters, Nathaniel Hawthorne is best known for such works as The House of the Seven Gables, and of course one of America's oft-cited morality tales, The Scarlet Letter. He was part of a wide circle of other notable figures in 19th-century American literature that included Henry David Thoreau, Herman Melville, and Henry Wadsworth Longfellow. Given his strong connection with New England and his birth in Salem, Massachusetts, it is not surprising that the acclaimed Peabody Museum in that same town has mounted a significant exhibit to commemorate the bicentennial of Hawthorne's birth in 1804. For those who cannot make it to Salem in the coming months, this online exhibit is a true delight. The site includes the complete digitized images of "The Spectator", which was a hand-copied newspaper produced by Hawthorne when he was 16. Clearly, those with a penchant for learning about the life of Hawthorne will want to make several trips to this site.

6

The Phyllomedusa perinesos group (Anura: Hylidae) is derived from a Miocene Amazonian Lineage.  

PubMed

The Phyllomedusa perinesos group is composed of four species that inhabit cloud forests in the eastern Andean slopes. We estimated the phylogenetic relationships among them and their closest relatives using mitochondrial DNA sequences. Our results confirm the monophyly of the group and a close relationship with the Amazonian species Phyllomedusa atelopoides and Phyllomedusa tomopterna. A chronogram indicates that the group originated during the Miocene and the contemporary species diverged from their closest relatives during the Miocene and early Pliocene. The timing of the group's origin suggests that its evolution was linked to the rise of the eastern Andes. Based on the phylogeny we expand the species content of the group to include P. atelopoides and P. tomopterna. PMID:25112990

Ron, Santiago R; Almendariz, Ana; Cannatella, David C

2013-01-01

7

The Miocene Topanga Group of Southern California - A 100-Year History of Changes in Stratigraphic Nomenclature  

USGS Publications Warehouse

A review of selected literature summarizes the origin and chronology of changes in usage of 'Topanga' in the Miocene stratigraphic nomenclature of the Los Angeles Basin and adjacent areas in southern California. The review was done to summarize and reconcile some differences in Miocene stratigraphic nomenclature as applied to geologic map compilations of the Santa Ana (Morton, 2004), San Bernardino (Morton and Miller, 2003), Long Beach (Saucedo and others, 2003) and Los Angeles (Yerkes and Campbell, 2005) 30' x 60' quadrangles, all of which are products of the cooperative (California Geological Survey-U.S. Geological Survey) Southern California Areal Mapping Project (SCAMP). The deposition of the Topanga Group spans about 6 my (from as old as about 18 ma to as young as about 12 ma), and the sequence of included strata records changes in provenance and depositional environments that are contemporaneous with part of a major Miocene tectonic episode in southern California -- the 'basin-inception phase' in the evolution of the Neogene Los Angeles basin (Yerkes and others, 1965). The area of Topanga deposition extends to the southern, eastern, northern, and northwestern sides of the Los Angeles basin, as well as the southern part of the eastern Ventura Basin. Topanga beds are inferred to underlie the thick upper Miocene and Pliocene deposits of the central Los Angeles Basin and the southern part of the eastern Ventura Basin; however, they have been reached by drilling only in marginal areas, where the overlying deposits are relatively thin. Post-Topanga strata were deposited in more-restricted areas of rapid subsidence. Selected papers are summarized as they relate to the Topanga nomenclature, and are presented in chronological order.

Campbell, Russell H.; McCulloh, Thane H.; Vedder, John G.

2007-01-01

8

Depositional environments and paleogeography of the Upper Miocene Wassuk Group, west-central Nevada  

USGS Publications Warehouse

Fluvial and lacustrine deposits of the Miocene Wassuk Group, exposed in Coal Valley, west-central Nevada, are divided into five lithofacies: (1) diatomite, claystone, siltstone, and carbonaceous siltstone deposited in a lake with paludal conditions at the margin; (2) upward-coarsening sequences of sandstone deposited on a delta and fan-delta; (3) channel-form sandstone deposited on a distal braided alluvial plain; (4) clast-supported conglomerate deposited on a proxial braided alluvial plain or distal alluvial fan; and (5) matrix-supported conglomerate deposited on a distal to middle alluvial fan. Petrographic analysis records an upsection change from a predominantly andesitic to a predominantly plutonic provenance. This change, combined with the overall upward-coarsening of the Wassuk Group and the great thickness (2400 m) of the sequence, suggests active uplift and rapid subsidence during deposition of the group. Facies relationships and paleocurrent directions indicate source areas to the south, southeast and west of Coal Valley. The Miocene Wassuk Group was deposited in an intra-arc basin with penecontemporaneous volcanism and tectonic activity. Syndepositional faulting at the southern margin of Coal Valley between 13 and 11 m.y. ago suggests an early episode of northeast-southwest extension prior to the onset of east-west basin and range extension. ?? 1984.

Golia, R.T.; Stewart, J.H.

1984-01-01

9

A reproductive screening test of hawthorn  

Microsoft Academic Search

Aim of studyHawthorn (Crataegus) has a long history as a medicine. The current clinical use of hawthorn as a heart medicine dates back to the late 19th century. It is well tolerated clinically yet contraindicated in pregnancy.

Mei Yao; Helen E. Ritchie; Patricia D. Brown-Woodman

2008-01-01

10

Characterization of antioxidants present in hawthorn fruits  

Microsoft Academic Search

Hawthorn fruit extract has been shown to have many health benefits including being cardiovascular protective, hypotensive and hypocholesterolemic. The present study was carried out to characterize further the antioxidants of hawthorn fruit and their effect on the oxidation of human low density lipoprotein (LDL) and ?-tocopherol. The dry hawthorn fruit was extracted successively with ether, ethyl acetate, butanol and water.

Zesheng Zhang; Qi Chang; Min Zhu; Yu Huang; Walter K. K. Ho; Zhen-Yu Chen

2001-01-01

11

Lowell on Hawthorne: A Summary Exercise.  

ERIC Educational Resources Information Center

Because Robert Lowell's poem "Hawthorne" focuses on Puritan New England, both as a setting and a subject, and shows the dark side of human nature, and Hawthorne as the alienated artist with a definite place in American literature, it is a most appropriate conclusion for a teaching unit on Hawthorne.

Fanning, Charles

1977-01-01

12

Funalichnus bhubani isp. nov. from Bhuban Formation, Surma Group (Lower -Middle Miocene) of Aizawl, Mizoram, India.  

PubMed

A new ichnospecies of the ichnogenus Funalichnus Pokorný is described from the Middle Bhuban Unit, Bhuban Formation, Surma Group (Lower - Middle Miocene) of Aizawl, Mizoram, India. Funalichnus bhubani isp. Nov. Is a large burrow displaying cylindrical segments that are oriented nearly perpendicular to the bedding plane. The new ichnospecies can be identified on the basis of general form, size, unlined passive filling and twisted rod-like structure. The association of Funalichnus bhubani isp. Nov. With Arenicolites, Diplocraterion, Ophiomorpha Psilonichnus Skolithos and Thalassinoides points to its bathymetric restriction. The deep extension of the burrow in clastic sediments provides a favourable condition for preservation in the shoreface environment and occurrence in fine- to medium-grained clastic sediments may be a preservational preference. PMID:24204992

Tiwari, Raghavendra Prasad; Rajkonwar, Chinmoy; Patel, Satish Jaychandbhai

2013-01-01

13

Incremental Compositional Zoning in the Widespread Phonolitic Ayagaures Ignimbrite in Miocene Fataga Group on Gran Canaria (Canary Islands)  

Microsoft Academic Search

The widespread phonolitic Ayagaures Ignimbrite (AI) (11.8 Ma) is a moderately to highly welded cooling unit of the Miocene Fataga Group (ca 13.3 - ca 9 Ma) on Gran Canaria (GC) (Canary Islands). Most of the up to 20 flow units have been mapped throughout the exposed area of at least 250km2. AI (average thickness 20- 25 m) dips regularly

M. Jutzeler; H. Schmincke; M. Sumita

2006-01-01

14

Hawthorne effects and research into professional practice.  

PubMed

The Hawthorne studies in the 1930s demonstrated how difficult it is to understand workplace behaviour, and this includes professional performance. Studies of interventions to improve professional performance, such as audit, can provide useful information for those considering using such methods, but cannot replace judgement. In particular, there is no single phenomenon that can be labelled 'the Hawthorne effect'. The process of triangulation, considering a subject from different perspectives, might overcome the problems of Hawthorne effects better than using a single method such as controlled trials. PMID:11240840

Holden, J D

2001-02-01

15

Genetic relationships among some hawthorn (Crataegus spp.) species and genotypes.  

PubMed

The genus Crataegus is well distributed in Turkey as a wild plant, with numerous, inherently variable species and genotypes. RAPD markers were used to study 17 hawthorn genotypes belonging to Crataegus monogyna ssp. monogyna Jacq (2 genotypes), C. monogyna ssp. azarella Jacq (1), Crataegus pontica K.Koch (3), Crataegus orientalis var. orientalis Pallas Ex Bieb (3), Crataegus pseudoheterophylla Pojark (1), Crataegus aronia var. dentata Browicz (1), C. aronia var. aronia Browicz (4), and Crateagus x bornmuelleri Zabel (2). The 10 RAPD primers produced 72 polymorphic bands (88% polymorphism). A dendrogram based on Jaccard's index included four major groups and one outgroup according to taxa. The lowest genetic variability was observed within C. aronia var. aronia genotypes. The study demonstrated that RAPD analysis is efficient for genotyping wild-grown hawthorns. PMID:20640884

Yilmaz, Kadir Ugurtan; Yanar, Makbule; Ercisli, Sezai; Sahiner, Hatice; Taskin, Tuncer; Zengin, Yasar

2010-10-01

16

Entomosporium Leafspot of Photinia and Indian Hawthorn  

E-print Network

This leaflet describes the fungus Entomosporium, which attacks photinia and Indian hawthorn plants. The publication describes the disease cycle and recommends cultural practices to control and treat the disease....

Ong, Kevin

2003-03-12

17

The Hawthorne effect and energy awareness  

PubMed Central

The feeling of being observed or merely participating in an experiment can affect individuals’ behavior. Referred to as the Hawthorne effect, this inconsistently observed phenomenon can both provide insight into individuals' behavior and confound the interpretation of experimental manipulations. Here, we pursue both topics in examining how the Hawthorne effect emerges in a large field experiment focused on residential consumers’ electricity use. These consumers received five postcards notifying, and then reminding, them of their participation in a study of household electricity use. We found evidence for a Hawthorne (study participation) effect, seen in a reduction of their electricity use—even though they received no information, instruction, or incentives to change. Responses to a follow-up survey suggested that the effect reflected heightened awareness of energy consumption. Consistent with that interpretation, the treatment effect vanished when the intervention ended. PMID:24003110

Schwartz, Daniel; Fischhoff, Baruch; Krishnamurti, Tamar; Sowell, Fallaw

2013-01-01

18

The Hawthorne effect and energy awareness.  

PubMed

The feeling of being observed or merely participating in an experiment can affect individuals' behavior. Referred to as the Hawthorne effect, this inconsistently observed phenomenon can both provide insight into individuals' behavior and confound the interpretation of experimental manipulations. Here, we pursue both topics in examining how the Hawthorne effect emerges in a large field experiment focused on residential consumers' electricity use. These consumers received five postcards notifying, and then reminding, them of their participation in a study of household electricity use. We found evidence for a Hawthorne (study participation) effect, seen in a reduction of their electricity use--even though they received no information, instruction, or incentives to change. Responses to a follow-up survey suggested that the effect reflected heightened awareness of energy consumption. Consistent with that interpretation, the treatment effect vanished when the intervention ended. PMID:24003110

Schwartz, Daniel; Fischhoff, Baruch; Krishnamurti, Tamar; Sowell, Fallaw

2013-09-17

19

FLOWER IMAGERY IN HAWTHORNE'S POSTHUMOUS NARRATIVES  

Microsoft Academic Search

Extensive use of botanical imagery gives dimension to the theme of the Deathless Man in the posthumous publications of Nathaniel Hawthorne. Both Doctor Grimshawe's Secret and Septimius Felton employ sustained flower imagery in their investigation of the mysteries of life and death and in their study of the conflict between man's need to live a productive life and his desire

MAX L. AUTREY

1975-01-01

20

Black-fruited hawthorns of western North America one or more agamic complexes?  

Microsoft Academic Search

Black-fruited hawthorns in North America comprise two taxonomic groups within the genus Crataegus, section Brevispinae and section Douglasianae. The first of these has recently been shown to be monospecific, consisting of the blue- berry haw, Crataegus brachyacantha Sarg. & Engelm., of Louisiana and Texas. Crataegus section Douglasianae, however, comprises several taxa in a single clade that is not closely related

Timothy A. Dickinson; Eugenia Y. Y. Lo; Nadia Talent; Rhoda M. Love

2008-01-01

21

Correlation and analysis of Miocene paleochannels in the central Sierra Nevada, California, as displayed by the Stanislaus Group  

NASA Astrophysics Data System (ADS)

The proposed Neogene uplift of the Sierra Nevada has been debated for several decades. Although multiple lines of evidence indicate substantial uplift of the Sierran crest over the last ten million years, recent isotopic and paleobotanical methods have called the validity of these calculations into question. Our study focuses on the discontinuous units of the Miocene Stanislaus Group: Table Mountain Formation lavas, Dardenelles Formation lavas, and Eureka Valley Tuff (EVT) lava and tuffs. These units are significant because they have been used as a tilt indicator to calculate the uplift of the Sierra Nevada crest since their emplacement, 9.0-10.2 million years ago. Our research increased the quantity of primary data, which will be used to develop and verify a digitally-derived model of the paleodrainage systems of the ancient Sierra Nevada. The localities, Dorrington, Pikes Peak, Rancheria Mountain, Three Chimneys, and Sonora Pass are significant because they may represent the few remaining Table Mountain Formation (trachyandesite) outcrops of previously unmapped paleodrainage channels. To test this hypothesis, geochemical and paleomagnetic data were used to correlate the localities and thereby reconstruct the paleochannels. Outcrops near Dorrington, California contain biotite, display eutaxitic textures and are characterized by a reverse polarity indistinguishable from the Tollhouse Flat Member of the EVT. Previously mapped as Table Mountain Latite, we reclassify these units as Tollhouse Flat Member and eliminate the hypothesis that the units were once part of a potentially lava-back-flooded tributary of the paleo-Stanislaus River. The high potassium, columnar jointed lava at Pikes Peak, exhibits normal polarity; it is plausibly part of the Stanislaus Group and may be correlated to flows along the main 'cataract channel' of the Stanislaus Group. Results from Rancheria Mountain verify the presence of Stanislaus Group lavas and the EVT, previously mapped by Huber et al. (1989). The normal polarity trachyandesite lavas, which have a limited distribution, may be locally sourced; the reversed polarity lavas correlate to outcrops near the Stanislaus Group source area at Little Walker Caldera. Mapping near Three Chimneys confirms the presence of the EVT and a capping trachyandesite lava previously mapped by Huber (1983). We show that the capping lava is younger than the EVT and thus cannot be Table Mountain Formation, as attributed by Huber (1983). This high potassium normal-polarity lava could be part of the Lava Flow Member of the EVT or the Dardanelles Formation. Lastly, Ar/Ar geochronology on the reversed polarity lava of the 'Table Mountain Event' geomagnetic excursion within the Table Mountain Formation suggests that the dated lava erupted during the subchron C5n.2n-1, the first known direct dating of volcanic rocks of this subchron.

Jones, S.; Pluhar, C. J.; Farner, M. J.; Deino, A. L.

2013-12-01

22

Validation of the Antidiabetic and Hypolipidemic Effects of Hawthorn by Assessment of Gluconeogenesis and Lipogenesis Related Genes and AMP-Activated Protein Kinase Phosphorylation  

PubMed Central

Since with the increased use of antidiabetic and antihyperlipidemic effect of phytonutrients for daily supplement has gained considerable attention worldwide, we examine the effect and molecular mechanism of Crataegus pinnatifida Bge. var. major N.E. Br. (hawthorn) by quantifying the expression of hepatic gluconeogenesis and lipogenesis on diabetes and dyslipidemia in high-fat (HF)-fed C57BL/6J mice. Firstly, mice were divided randomly into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was given orally hawthorn extract (including 0.2, 0.5, 1.0?g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks afterward. Diabetic mice showed an increase in plasma glucose and insulin. Glucose lowering was comparable with Rosi-treated mice. This study demonstrated that hawthorn was effective in ameliorating the HF diet-induced hyperglycemia, hypertriglyceridemia and hypercholesterolaemia. Hawthorn extract significantly increases the hepatic protein contents of AMP-activated protein kinase (AMPK) phosphorylation and reduces expression of phosphenol pyruvate carboxykinase (PEPCK) and glucose production. Furthermore, hawthorn decreased in hepatic triacylglycerol and cholesterol synthesis (including sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), SREBP2). An increase in expressions of apoA-I gene and high-density lipoprotein cholesterol (HDL-C) was detected in HF-fed mice treated with high dose hawthorn. Our data suggest that hawthorn extract are capable of decreasing glucose production and triacylglycerol synthesis by inducing AMPK-phosphorylation and hawthorn is a candidate source of antidiabetic and antihyperlipidemic phytonutrients factors. PMID:23690849

Shih, Chun-Ching; Lin, Cheng-Hsiu; Lin, Yih-Jiun; Wu, Jin-Bin

2013-01-01

23

Incremental Compositional Zoning in the Widespread Phonolitic Ayagaures Ignimbrite in Miocene Fataga Group on Gran Canaria (Canary Islands)  

NASA Astrophysics Data System (ADS)

The widespread phonolitic Ayagaures Ignimbrite (AI) (11.8 Ma) is a moderately to highly welded cooling unit of the Miocene Fataga Group (ca 13.3 - ca 9 Ma) on Gran Canaria (GC) (Canary Islands). Most of the up to 20 flow units have been mapped throughout the exposed area of at least 250km2. AI (average thickness 20- 25 m) dips regularly 4-5° in southern to southwestern GC and has reached the sea at many places. Its mapped volume is approximately 4.5 km3. This plus tentatively correlated ODP syn-ignimbrite deposits (Sumita and Schmincke, 1998 and unpubl.) and its probable former widespread distribution over at least western GC suggest a total erupted magma volume of >50km3. Phonolitic AI contains up to 20 vol % of dominantly anorthoclase-sanidine and minor (<1 vol %) biotite, Fe- augite, titanite, haüyne and apatite. The cooling unit is compositionally zoned becoming more mafic upwards. Trace elements and REE show significant magma reservoir zoning in both bulk rock and phenocryst composition, while major elements change little. All phenocryst species were unzoned and their composition within each flow unit extremely homogeneous. The shallow level magma reservoir is interpreted to have been compositionally zoned but thermodynamically equilibrated. Strong mixing preceded the separation of the magma chamber into several small convective layers in which one single growth event of alkali feldspar and biotite occurred. The presence of large haüyne and titanite crystals within the topmost layers of the reservoir (basal flow unit) and a locally preserved highly evolved fallout tephra document a highly fractionated volatile-rich but small-volume cupola. AI represents the most evolved part of a larger partially evacuated magma reservoir. Progressive downward tapping of the reservoir was controlled by incremental caldera collapse. Unzoned phenocrysts, incremental CU zoning and evacuation reversals show that mixing did not occur after separation into layers.

Jutzeler, M.; Schmincke, H.; Sumita, M.

2006-12-01

24

Hawthorn (Crataegus spp.) in the treatment of cardiovascular disease  

PubMed Central

The medicinal properties of hawthorn (Crataegus spp., a genus comprising approximately 300 species) have been utilized by many cultures for a variety of therapeutic purposes for many centuries. In the Western world cardiovascular disease (CVD) has become one of the single most significant causes of premature death. Echoing this situation, more recent research into the therapeutic benefits of hawthorn preparations has focused primarily upon its cardiovascular effects. This review covers research into the various mechanisms of action proposed for Crataegus preparations, clinical trials involving Crataegus preparations, and the herb's safety profile. Clinical trials reviewed have been inconsistent in terms of criteria used (sample size, preparation, dosage, etc) but have been largely consistent with regard to positive outcomes. An investigation into data available to date regarding hawthorn preparations and herb/drug interactions reveals that theoretical adverse interactions have not been experienced in practice. Further, adverse reactions relating to the use of hawthorn preparations are infrequent and mild, even at higher dosage ranges. A recent retrospective study by Zick et al. has suggested a negative outcome for the long-term use of hawthorn in the prognosis of heart failure. These findings are examined in this paper. Although further research is needed in certain areas, current research to date suggests that hawthorn may potentially represent a safe, effective, nontoxic agent in the treatment of CVD and ischemic heart disease (IHD). PMID:22228939

Tassell, Mary C.; Kingston, Rosari; Gilroy, Deirdre; Lehane, Mary; Furey, Ambrose

2010-01-01

25

The Miocene rodents of Serbia  

Microsoft Academic Search

During the Miocene period a group of shallow lakes was created in depressions at the territory of present-day Serbia. This caused the present wide distribution of lacustrine sediments, which occasionally alternate with the alluvial and marsh sediments. The remains of large mammals are relatively common, while the remains of small mammals used to be known only from two localities -

Z. Markovic

2009-01-01

26

The Lockean Thesis and the Logic of Belief James Hawthorne  

E-print Network

satisfy the axioms of probability theory may quite rationally believe each of a large body of propositions USA e-mail: hawthorne@ou.edu 1 Foley cites Locke's An Essay Concerning Human Understanding, (1975), Book IV, Chapters xv and xvi. Foley discusses the thesis further in his (1993). 2 This is an instance

Fitelson, Branden

27

Fourth Period Discovers Hester as Mother: Hawthorne's Mother?  

ERIC Educational Resources Information Center

A teacher discusses how she used criticism of "The Scarlet Letter," when studying the book, in her honors class. The students were also intrigued by the biographical information they learned about Hawthorne, and eager to use it in interpreting his novel. (SRT)

Heginbotham, Eleanor

1986-01-01

28

Secular variation of the middle and late Miocene geomagnetic field recorded by the Columbia River Basalt Group in Oregon, Idaho and Washington, USA  

NASA Astrophysics Data System (ADS)

This study of 118 discrete volcanic flows from the Columbia River Basalt Group is aimed to determine their distribution of geomagnetic field directions and virtual geomagnetic poles (VGPs) and to compare the inherent secular variation parameters with those from other studies. The magnetic signature of these rocks is uniformly carried by primary titanomagnetite, indicating that magnetic changes are due to variations in the magnetic field. Although most flows are flat lying, those that are tilted pass the Tauxe and Watson tilt test. Sequential flows with statistically similar site means were grouped, and directions that were considered outliers were evaluated and removed using the Vandamme cut-off method. Three normal-polarity (N-polarity) and three reversed-polarity (R-polarity) intervals are revealed by the stratigraphically ordered flows and have mean directions of N polarity (dec/inc = 6.6°/+61.2°, k = 29.3, ?95 = 4.2°), and R polarity (dec/inc = 178.2°/-59.2°, k = 16, ?95 = 5.5°). Regression analysis indicates that the secular variation analysis has not been affected by regional rotation, and that apparent polar wander is negligible. The VGP distribution is almost perfectly circular and supports the preference of VGP positions for the dispersion analysis. Dispersion parameters with corrections for within-site scatter (Sb) show a range of 14.3°-25.5°, including error limits, and were consistently higher for R-polarity results than for those of N polarity. Published dispersion parameters for extrusives <5 Ma show Sb values slightly lower than ours, yielding values of 16°-19°, although the difference is not statistically significant. In contrast, published dispersion parameters from high quality data from the Cretaceous Normal Superchron are lower than those for the Neogene, which suggests that the noisiness of the magnetic field correlates with the frequency of reversals. Our new results allow us to extend the Plio-Pleistocene palaeosecular variation database to the bottom of the middle Miocene. Many Miocene formations on a variety of continents are suitable targets for future analysis. Furthermore, the significant difference between the reversed and N-polarity dispersion parameters is intriguing and needs substantiation.

Dominguez, Ada R.; Van der Voo, Rob

2014-06-01

29

The Burden of Secret Sin: Nathaniel Hawthorne's Fiction The fiction of Nathaniel Hawthorne has frequently been defined in musical terms on account of  

E-print Network

of his works contain elements of novelty that soften the sin- obsessed Puritan world-view. His in The House of the Seven Gables where the seven gables manifestly stand for the seven capital sins and evokeThe Burden of Secret Sin: Nathaniel Hawthorne's Fiction The fiction of Nathaniel Hawthorne has

Paris-Sud XI, Université de

30

Marine mammals from the Miocene of Panama  

NASA Astrophysics Data System (ADS)

Panama has produced an abundance of Neogene marine fossils both invertebrate (mollusks, corals, microfossils etc.) and vertebrate (fish, land mammals etc.), but marine mammals have not been previously reported. Here we describe a cetacean thoracic vertebra from the late Miocene Tobabe Formation, a partial cetacean rib from the late Miocene Gatun Formation, and a sirenian caudal vertebra and rib fragments from the early Miocene Culebra Formation. These finds suggest that Central America may yet provide additional fossil marine mammal specimens that will help us to understand the evolution, and particularly the biogeography of these groups.

Uhen, Mark D.; Coates, Anthony G.; Jaramillo, Carlos A.; Montes, Camilo; Pimiento, Catalina; Rincon, Aldo; Strong, Nikki; Velez-Juarbe, Jorge

2010-12-01

31

Fossil woods from the Lower Coal-bearing Formation of the Janggi Group (Early Miocene) in the Pohang Basin, Korea  

Microsoft Academic Search

Fourteen species of fossil wood belonging to eleven genera and seven families were identified from 38 well preserved specimens collected from the Lower Coal-bearing Formation of Janggi Group at Donghae-myeon, Pohang City, Gyeongsangbuk-do Prefecture, Korea. Seven new taxa were found and described; they are Carya koreana Jeong et Kim, Betula janggiensis Jeong et Kim, Carpinus donghaensis Jeong et Kim, Ostrya

Eun Kyoung Jeong; Kyungsik Kim; Mitsuo Suzuki; Jong Won Kim

2009-01-01

32

Effects on hawthorn the year after simulated spray drift.  

PubMed

This paper describes the effect of a herbicide applied at levels consistent with off target movement on hawthorn the year following exposure. In the experiment, metsulfuron-methyl was applied in five dosages to individual trees in seven different hawthorn hedgerows. Spraying was conducted both at the bud stage and at the early flowering. Five endpoints (i.e. leaves, buds, flowers, green berries and mature berries) were sampled and counted. All were significantly reduced with increasing exposure. Present day risk assessment of effects on non-target plants is therefore likely to overlook significant effects on perennial non-target plants in the spray drift zone due to the focus on results from short-term laboratory test studies. The significance of the present study is underlined by the fact that the effects observed were significant, even though other influential factors such as herbivory and differential pollination were not eliminated and that experiments were conducted in multiple locations. PMID:16169052

Kjaer, Christian; Strandberg, Morten; Erlandsen, Mogens

2006-05-01

33

Genetic Relationships Among Some Hawthorn ( Crataegus spp.) Species and Genotypes  

Microsoft Academic Search

The genus Crataegus is well distributed in Turkey as a wild plant, with numerous, inherently variable species and genotypes. RAPD markers were\\u000a used to study 17 hawthorn genotypes belonging to Crataegus monogyna ssp. monogyna Jacq (2 genotypes), C. monogyna ssp. azarella Jacq (1), Crataegus pontica K.Koch (3), Crataegus orientalis var. orientalis Pallas Ex Bieb (3), Crataegus pseudoheterophylla Pojark (1), Crataegus

Kadir Ugurtan Yilmaz; Makbule Yanar; Sezai Ercisli; Hatice Sahiner; Tuncer Taskin; Yasar Zengin

2010-01-01

34

Hawthorn ( Crataegus monogyna Jacq.) extract exhibits atropine-sensitive activity in a cultured cardiomyocyte assay  

Microsoft Academic Search

Hawthorn (Crataegus spp.) plant extract is used as a herbal alternative medicine for the prevention and treatment of various cardiovascular diseases.\\u000a Recently, it was shown that hawthorn extract preparations caused negative chronotropic effects in a cultured neonatal murine\\u000a cardiomyocyte assay, independent of beta-adrenergic receptor blockade. The aim of this study was to further characterize the\\u000a effect of hawthorn extract to

Satin Salehi; Shannon R. Long; Philip J. Proteau; Theresa M. Filtz

2009-01-01

35

Parasitism of the apple maggot, Rhagoletis pomonella , infesting hawthorns in Washington  

Microsoft Academic Search

Five species of larval parasitoids were reared fromRhagoletis pomonella (Walsh) infested fruit of hawthorn,Crataegus, collected from several locations in southwest Washington over a four year period. A braconid,Biosteres melleus (Gahan), parasitized larvae infesting fruits of a native hawthorn species,Crataegus douglasii Lindl. Another braconid,Opius downesi Gahan, emerged exclusively fromR. pomonella pupae reared from fruits of an introduced species of hawthorn,Crataegus monogyna

L. J. Gut; J. F. Brunner

1994-01-01

36

Miocene deepwater oceanography  

NASA Astrophysics Data System (ADS)

A global synthesis of Miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that Miocene thermohaline circulation evolved through three regimes corresponding approximately to early, middle, and late Miocene times. There is evidence for major qualitative differences between the circulation of the modern ocean and the Miocene ocean prior to 11 Ma. The 13C/12C ratios of the benthic foraminifera Cibicidoides are interpreted in terms of water mass aging, i.e., the progressive depletion of dissolved O2 and lowering of ?13C values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans. Both isotopic and faunal data indicate that the early Miocene regime, from 22 to 15 Ma, was the most different from today's. During that interval intermediate and deep waters of both the Atlantic and the Pacific oceans aged in a northward direction, and the intermediate waters of the Indian, the South Atlantic and the South Pacific oceans were consistently the youngest in the global ocean. We speculate that early Miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water, Tethyan Indian Saline Water, from the Tethys into the northern Indian Ocean. The isotopic and faunal data suggest that flow from the Tethyan region into the Indian Ocean diminished or terminated at about 14 Ma. Isotopic and faunal data give no evidence for North Atlantic Deep Water (NADW) formation prior to about 14.5 Ma (with the exception of a brief episode in the early Miocene). From 14.5 to 11 Ma NADW formation was weak, and circumpolar and Antarctic water flooded the deep South Atlantic and South Pacific as the Antarctic ice cap grew. From about 10 Ma to the end of the Miocene, thermohaline circulation resembled the modern circulation in many ways. In latest Miocene time (6 to 5 Ma) circulation patterns were very similar to today's except that NADW formation was greatly diminished. The distribution pattern of siliceous oozes in Miocene sediments is consistent with our proposed reconstruction of thermohaline circulation. Major changes which occurred in circulation during the middle Miocene were probably related to the closing of the Tethys and may have contributed to rapid middle Miocene growth of the Antarctic ice cap. Appendices 1, 4, 6, and 7 are available withentire article on microfiche. Order fromAmerican Geophysical Union, 2000 FloridaAvenue, N.W., Washington, DC 20009.Document 88P-002; $5.00. Payment mustaccompany order.

Woodruff, Fay; Savin, Samuel M.

1989-02-01

37

76 FR 67103 - Proposed Revision of Class D and Class E Airspace; Hawthorne, CA  

Federal Register 2010, 2011, 2012, 2013

...11-AWP-10] Proposed Revision of Class D and Class E Airspace; Hawthorne, CA AGENCY...SUMMARY: This action proposes to revise Class D and E airspace at Jack Northrop Field/Hawthorne...Regulations (14 CFR) Part 71 by revising Class D airspace and Class E airspace...

2011-10-31

38

Hawthorn fruit increases the antioxidant capacity and reduces lipid peroxidation in senescence-accelerated mice  

Microsoft Academic Search

Hawthorn fruit has long been used as a folk medicine with many medicinal benefits. HPLC analysis revealed that hawthorn fruit\\u000a extract (HFE) contained 19.86% procyanidin B2, 15.27% epicatechin, 3.10% chlorogenic acid, 2.91% hyperoside, and 1.34% isoquercitrin.\\u000a Antioxidants are essential for protection of the bodies against the damaging action of free radicals. And we hypothesized\\u000a that HFE could enhance antioxidant defenses

Hao WangZesheng; Zesheng Zhang; Ying Guo; Ping Sun; Xiaoling Lv; Yanbo Zuo

2011-01-01

39

Antarctic Miocene Climate  

NASA Astrophysics Data System (ADS)

Fossils from Antarctic Miocene terrestrial deposits, coupled with stratigraphic, geochemical and paleontological data from marine boreholes, provide new insights into the climatic history of the continent. During the Miocene, ice caps coalesced to form ice sheets and vegetated surfaces gave way to barren expanses. The cryospheric changes especially have global climatic implications. The fossil data consists of diatoms, pollen and spores, and macroscopic remains of plants, ostracods, insects, molluscs and a fish. Plant fossils include wood and leaves of Nothofagus (southern beech), seeds of several vascular plants, including Ranunculus (buttercup), Hippuris (mare's-tail) and Myriophyllum (watermilfoil), megaspores of Isoetes (quillwort), and moss species. The insect chitin consists of larval head capsules of Chironomidae (midges) and exoskeletal parts of Coleoptera (beetles). The molluscs include freshwater gastropods and bivalves. The majority of these taxa are likely descendants of taxa that had survived on the continent from the Paleogene or earlier. Even though early Miocene glaciations may have been large, the climate was never cold enough to cause the extinction of the biota, which probably survived in coastal refugia. Early Miocene (c. 20 Ma) macrofossils from the McMurdo Dry Valleys (77°S) support palynological interpretations from the Cape Roberts and ANDRILL marine records that the upland vegetation was a shrub tundra. Mean summer temperature (MST) in the uplands was c. 6°C and possibly higher at the coast. The climate was wet, supporting mires and lakes. By the mid-Miocene, even though the climate continued to be wet. MST was c. 4°C which was too cold to support Nothofagus and most vascular plant species. Stratigraphic evidence indicates that the time between the Early and Mid-Miocene was a time of repeated ice advances and retreats of small glaciers originating from ice caps. At c. 14 Ma there appears to have been a modal shift in climate to significantly colder and drier conditions that resulted in the extinction of the upland biota and a shift in glacial regimes from wet to cold-based. Paleontological and geochemical evidence from the deep marine record supports a major climatic event at this time. Based on pollen from the SHALDRIL cores a tundra biota survived until c. 12.8 Ma on the islands of the Antarctic Peninsula (65°S). Recently, sparse angiosperm pollen of chenopods or similar taxa, has been reported from deposits in the Prince Charles mountains (70°S) with a biostratigraphic age of Mid- to Late Miocene (12-9 Ma) making it possible that remnants of a tundra vegetation continued to exist on the edges of the continent after it had become extinct on the islands of the Antarctic Peninsula. Evidence for Pliocene warmth in the Ross Sea from thick diatomite sequence in ANDRILL cores is so far unsupported by terrestrial paleontological evidence. Pliocene wood-like structures reported from a DVDP core are interpreted as the remains of in situ shrubs but the evidence is unconvincing. Pliocene warmth in the Ross sea region, unaccompanied by an unambiguous terrestrial response can be explained in one of two ways: 1. Pliocene MSTs remained below the 3-4°C threshold needed to support shrub or herb tundra, or 2. Pliocene MSTs were warm enough but terrestrial taxa were unavailable because of extinction. Research supported by NSF 0739693,0947821.

Ashworth, A. C.; Lewis, A. R.

2013-12-01

40

Apatite (U-Th)/He Thermochronometry as an innovative Geothermal Exploration Tool - A case study from the Wassuk Range, Hawthorne, Nevada  

NASA Astrophysics Data System (ADS)

A utility-grade geothermal system requires increased, near-surface temperatures (>120°C), water to transfer heat, and structural or sedimentological fluid conduits. In extensional tectonic settings, geothermal anomalies often occur in areas with recent, high strain accumulation and complex faulting (i.e., cross-faults, accommodation zones) where exhumation and uplift of footwall rocks transfer heat, via advection, to the near-surface which is further carried by water through structural fluid conduits. Apatite helium (AHe) thermochronometric footwall age mapping can be used in conjunction with these genetic occurrence models to further focus regional-scale geothermal exploration efforts to areas of probabilistic increased fracture permeability and most recent, rapid footwall exhumation. Furthermore, partially reset apatites resulting from interaction with hydrothermal fluids (>40°C) will show which areas have been hottest most recently. This case study in the Wassuk Range, Hawthrone, NV confirms the utility of AHe thermochronometry as a geothermal exploration tool. A dense grid of footwall samples were collected adjacent to the Hawthorne geothermal anomaly (>85°C BHT) located in the hanging wall of the Wassuk Range block. Our data show that the location of the present-day geothermal anomaly correlates with the location of 1) the most recent episode of rapid footwall exhumation at 3.5-4 Ma, 2) km scale accommodation zones between differentially tilted Wassuk Range blocks, and 3) an elevated Miocene geothermal gradient. Furthermore, anomalously young AHe ages (<3.5 Ma) mimic the lateral extent of the Hawthorne geothermal anomaly and likely resulted from interaction with a deep-seated geothermal cell or hot hydrothermal fluids.

Gorynski, K. E.; Stockli, D. F.; Walker, J. D.

2010-12-01

41

Headspace solid-phase microextraction analysis of volatile compounds in hawthorn vinegars fermented by two strains of Acetobacter  

Microsoft Academic Search

Hawthorn (Crataegus oxyacantha), which is wildly distributed in northern China, has a long history as a medicinal substance, for the treatment of digestive ailments, dyspnea, kidney stones and cardiovascular disorders, etc. Today, it is currently used for the juice production and is used as the raw material for hawthorn wine and vinegar production. However, the flavor of fruit vinegars diversifies

Yu Zheng; Hongxiang Liu; Keping Zhang; Min Wang

2010-01-01

42

Identification of host fruit volatiles from domestic apple (Malus domestica), native black hawthorn (Crataegus douglasii) and introduced ornamental hawthorn (C. monogyna) attractive to Rhagoletis pomonella flies from the western United States.  

PubMed

The apple maggot fly, Rhagoletis pomonella, infests apple (Malus domestica) and hawthorn species (most notably the downy hawthorn, Crataegus mollis) in the eastern USA. Evidence suggests that the fly was introduced into the western USA sometime in the last 60 years. In addition to apple, R. pomonella also infests two species of hawthorns in the western USA as major hosts: the native black hawthorn (C. douglasii) and the introduced ornamental English hawthorn, C. monogyna. Apple and downy hawthorn-origin flies in the eastern USA use volatile blends emitted from the surface of their respective ripening fruit to find and discriminate among host trees. To test whether the same is true for western flies, we used coupled gas chromatography and electroantennographic detection (GC-EAD) and developed a 7-component apple fruit blend for western apple-origin flies, an 8-component black hawthorn fruit blend for flies infesting C. douglasii, and a 9-component ornamental hawthorn blend for flies from C. monogyna. Crataegus douglasii and C. monogyna-origin flies showed similar levels of upwind directed flight to their respective natal synthetic fruit blends in flight tunnel assays compared to whole fruit adsorbent extracts, indicating that the blends contain all the behaviorally relevant fruit volatiles to induce maximal response levels. The black and ornamental hawthorn blends shared four compounds in common including 3-methylbutan-1-ol, which appears to be a key volatile for R. pomonella populations in the eastern, southern, and western USA that show a preference for fruit from different Crataegus species. However, the blends also differed from one another and from domesticated apple in several respects that make it possible that western R. pomonella flies behaviorally discriminate among fruit volatiles and form ecologically differentiated host races, as is the case for eastern apple and hawthorn flies. PMID:22399441

Cha, Dong H; Yee, Wee L; Goughnour, Robert B; Sim, Sheina B; Powell, Thomas H Q; Feder, Jeffrey L; Linn, Charles E

2012-03-01

43

Comparative Protective Effect of Hawthorn Berry Hydroalcoholic Extract, Atorvastatin, and Mesalamine on Experimentally Induced Colitis in Rats  

PubMed Central

Abstract The protective effect of hydroalcoholic extract of hawthorn berries (HBE) on acetic acid (AA)–induced colitis in rats was investigated. Forty-two Wistar rats were divided into seven groups, including control and test groups (n=6). The control animals received saline, and the test animals were treated with saline (sham group), mesalamine (50?mg/kg; M group), atorvastatin (20?mg/kg; A group), HBE (100?mg/kg; H group), mesalamine and HBE (HM group), or atorvastatin plus HBE (HA group), 3 days before and a week after colitis induction. Colitis was induced by administration of 1?mL AA (4%) via a polyethylene catheter intrarectally. High-performance liquid chromatography analyses showed that HBE contained 0.13% and 0.5% oleanolic acid and ursolic acid, respectively. Elevated myeloperoxidase activity and lipid peroxidation were attenuated in the HA group. The H and HM groups showed marked reductions in colitis-induced decreases in total thiol molecules and body weight. The histopathological studies revealed that HBE decreased colitis-induced edema and infiltration of neutrophils. Our data suggest the anti-inflammatory and antioxidant effects of HBE and atorvastatin protect against AA-induced colitis. The anti-inflammatory effect of HBE may be attributable to its ability to decrease myeloperoxidase activity as a biomarker of neutrophil infiltration. PMID:23875899

Shafie-Irannejad, Vahid; Hobbenaghi, Rahim; Tabatabaie, Seyed Hamed; Moshtaghion, Seyed-Mehdi

2013-01-01

44

77 FR 7525 - Revision of Class D and Class E Airspace; Hawthorne, CA  

Federal Register 2010, 2011, 2012, 2013

...Docket No. 11-AWP-10] Revision of Class D and Class E Airspace; Hawthorne, CA AGENCY...SUMMARY: This action revises Class D and Class E airspace at Jack Northrop Field...the FAA. No comments were received. Class D airspace and Class E airspace...

2012-02-13

45

Curtobacterium flaccumfaciens Septic Arthritis following Puncture with a Coxspur Hawthorn Thorn ?  

PubMed Central

Curtobacterium species are recognized plant pathogens. We report the first well-documented case of Curtobacterium human infection, a child with septic arthritis following puncture with a Coxspur Hawthorn plant thorn. The organism isolated from synovial tissue and the plant thorn was identified as Curtobacterium flaccumfaciens by 16S rRNA gene sequence analysis. PMID:21562106

Francis, Michelle J.; Doherty, Richard R.; Patel, Minoo; Hamblin, John F.; Ojaimi, Samar; Korman, Tony M.

2011-01-01

46

Calcareous Nannofossil Evolution Vs. Climatic Evolution In The Miocene  

NASA Astrophysics Data System (ADS)

Miocene times were characterized by major changes in ocean circulation and global climate that were driven by a complex set of factors operating on tectonic, orbital and suborbital timescales (Zachos et al., 2001). This time dependent development of Miocene paleo-environmental conditions is reflected in the distribution and evolutionary patterns, often expressed in terms of biostratigraphic resolution, among the dominant sediment-forming oceanic plankton groups (Kennett & Srinivasan, 1983; Baldauf & Barron, 1990; Perch-Nielsen, 1985) including calcareous nannofossils. In the Miocene through Pleistocene interval, calcareous nannofossil evolutionary appearances or extinctions provide eight biostratigraphically useful biohorizons between 23 Ma and 14 Ma, giving an average rate of 1.5 biohorizon per million years. In the next following eight million years (14-5 Ma), the number of biohorizons are 29 (3.6 biohorizons/million years), representing well over a doubling of the rate of taxonomic evolution among open ocean calcareous nannofossils compared with that of the early half of the Miocene. This observation demonstrates that a distinct evolutionary response to climatic evolution throughout the Miocene, specifically to changing conditions in the photic zone of the middle and late Miocene oceans. This assumption is supported by the behavior of some nannofossil groups, in particular by the representatives of the genus Discoaster, a key group that gives nearly half (14 of 29) of biohorizons in the younger half of the Miocene. The Discoaster's environmental distribution and abundance may provide some information about the complex interaction between climatic evolution and biotic evolution in the plankton realm.

Raffi, I.; Backman, J.; Ciummelli, M.

2013-12-01

47

An overview of Miocene reefs  

SciTech Connect

Miocene reefs lived approximately within the latitudes of 27{degree}S to 48{degree}N compared with 25{degree}S and 32{degree}N for Holocene reefs. This expansion of reef-growing environments was the result of warm Miocene climates, aided by a eustatic sea level rise and tectonic styles that provided numerous foundations for reef development. The majority of Miocene reefs are found in three main areas: (1) Southeast Asia and the western Pacific, (2) the Mediterranean-Middle East, and (3) Middle America and the Caribbean. These regions, with their distinctive suites of coral and foramineral species, formed three biological provinces; respectively, they are the Indo-Pacific, Tethyan, and Western Atlantic provinces. Miocene reefs in Southeast Asia occur in several foreland basins as patch reef complexes on paleohighs and as barrier reefs in back-arc basins. Those reefs in the Mediterranean occur as fringing reefs, middle-shelf patch reefs, or as barrier reefs on the edges of tectonic blocks associated with Alpine thrust belts. Most reefs in the Caribbean grew on isolated open-ocean highs of volcanic origin. Miocene reefs display a diversity of framework types: (1) coral-encrusting, red algal boundstones with diverse coral faunas, (2) branching coral-encrusting, red algal boundstones with a limited Poritid fauna, (3) encrusting red algal boundstones. Barrier reef systems are especially rich in encrusting red algae and robust corals; grainstones are common as interbedded sediment. Patch reef complexes, however, display muddy carbonate textures, may have less diverse coral faunas, and commonly have larger foraminifera. The global distribution of Miocene reefs is important because (1) it provides insight into a paleoclimatic view of the earth during a major greenhouse stage and (2) Miocene buildups, such as the Arun (EUR of 14 tcf) and Bima fields (EUR of about 100 MMBO), are exploration targets.

Jordan, C.F. Jr. (Mobil Research and Development Corp., Dallas, TX (USA)); Colgan, M.W. (College of Charleston, SC (USA)); Frost, S.H. (Unocal, Los Angeles, CA (USA)); Glenn, E.C. (Phillips Petroleum, Bartlesville, OK (USA)); Bosence, D. (Royal Holloway and Bedford New College, Egham (England)); Esteban, M. (ERICO Petroleum Information Ltd., London (England))

1990-05-01

48

Composition and provenance of the Puente Formation (Miocene), Los Angeles Basin  

Microsoft Academic Search

The Puente Formation (PFm) is a middle to upper Miocene clastic unit lying unconformably on the middle to lower Miocene El Modeno Volcanics and Topanga Group, within the Los Angeles basin (LAB). The PFm, about 3900m thick, is composed of sandstone, conglomerate, and mudrock deposited on a submarine fan at bathyal depths. Several intrabasinal discordances suggest active tectonics during deposition.

S. Critelli; P. E. Rumelhart; R. V. Ingersoll

1994-01-01

49

A macroecological glance at the structure of late Miocene rodent assemblages from Southwest Europe  

NASA Astrophysics Data System (ADS)

Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time.

Cano, Ana Rosa Gómez; Cantalapiedra, Juan L.; Álvarez-Sierra, M. Ángeles; Fernández, Manuel Hernández

2014-10-01

50

A macroecological glance at the structure of late Miocene rodent assemblages from Southwest Europe  

PubMed Central

Deep-time perspectives in macroecology are essential with regard to understanding the impact of climate forcing on faunal communities. Using late Miocene rodent faunas (12 to 5?Ma) from two different biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are generalists in the southern province and specialists of forested habitats in the northern province. Finally, we identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the Miocene. These three broad ecological groups showed differential responses to a complex set of interconnected circumstances, including the biogeographic structure of the study area and climatic changes throughout time. PMID:25297009

Cano, Ana Rosa Gomez; Cantalapiedra, Juan L.; Alvarez-Sierra, M. Angeles; Fernandez, Manuel Hernandez

2014-01-01

51

1, 167188, 2006 Late Miocene River  

E-print Network

eED 1, 167­188, 2006 Late Miocene River Euphrates T. Demir et al. Title Page Abstract Introduction is the access reviewed discussion forum of eEarth Location of the River Euphrates in the Late Miocene; dating Miocene River Euphrates T. Demir et al. Title Page Abstract Introduction Conclusions References Tables

Boyer, Edmond

52

Diagenesis of the Oligocene-Miocene rocks of the Upper Floridan and Intermediate aquifer systems by meteoric and mixing-zone waters in southwest Florida  

SciTech Connect

Optical and SEM of samples from 6 cores of Oligocene and Miocene rocks that compose portions of the Florida and Intermediate aquifers and the intervening semiconfining unit documents meteoric and mixing-zone (seawater and fresh carbonate ground water) diagenesis inferred to have occurred over several cycles of sea level change. Dolomite, limestone, sandstone, and claystone of the Suwannee Formation and the Arcadia Formation (Hawthorn Group) were examined. Core samples from time-equivalent strata in two E--W transects in Manatee, Hardee, Highlands, Sarasota, and DeSoto Counties are estimated to be 16--33 Ma on the basis of [sup 87]Sr/[sup 86]Sr ratios from unaltered mollusk shells and by molluscan biostratigraphy. Lithostratigraphic correlations are based on examination of 19 cores, 62 thin sections, 60 geophysical logs, and mineralogy determined by X-ray diffraction. Diagenetic indicators that the authors tracked petrographically include shell micritization, shell dissolution, equant and (or) fibrous CaCO[sub 3] cement, neomorphism, dolomite, etched phosphate grains, echinoderm fragment syntaxial overgrowths, and amorphous silica pore lining. Infiltration of meteoric water caused dissolution of carbonate minerals, especially aragonite, and precipitation of equant calcite crystals in voids of dissolved fossils and in pore spaces between grains. The silica was precipitated as pore linings in zones having soil textures. Observed replacement of calcite by limpid dolomite is consistent with modeling predictions of mixing-zone diagenesis. Etched crystals of limpid dolomite may indicate freshwater dissolution of a mixing-zone precipitate. Mapping of regional unconformities revealed pronounced thickening and thinning of some units. Evidence of meteoric water diagenesis is observed in the upper 600 ft of the transects examined. Evidence of mixing-zone diagenesis is observed at varying depths, but appears to increase in abundance and thickness toward the west.

Weedman, S.D. (Pennsylvania State Univ., Univ. Park, PA (United States)); McCartan, L. (Geological Survey, Reston, VA (United States))

1993-03-01

53

Outcasts of the universe: a study of the scientists in Hawthorne's short stories.  

E-print Network

Universe at the end. of "Wakefield, " th. e story of a man;. ao one d. ay walks out of nis home, stays away for over twe, ty years, end. fails when he tries to return after t' at time to his old pattern of life. Of Wakefield. , Hawthorne says, Amid.... om to mend, and. , like a . jealous patenm e, on no account to make" (IZ, 54). Havirg forgotten tne failures of his previous attempts to d. iscover tne "elixir vitae, " ne resumes his studies with che hope cf findf ng the Becjs whj Qh wil) I...

Decker, Joseph Patrick

2012-06-07

54

Constitutive and herbivore?induced volatiles in pear, alder and hawthorn trees  

Microsoft Academic Search

Summary.   Qualitative and quantitative differences among pear cultivars were found\\u000a in constitutive and Cacopsylla-induced volatiles, depending on\\u000a experimental treatment of the trees (i.e., uninfested and partly or\\u000a completely infested by psyllids). Blend differences were also found\\u000a between pear cultivars and wild-type pear, alder and hawthorn–the\\u000a latter trees are frequently present in pear orchard\\u000a hedgerows. ¶Interesting differences were found in the

Petru Scutareanu; Jan Bruin; Maarten A. Posthumus; Bas Drukker

2003-01-01

55

Preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada  

SciTech Connect

Site characteristics pertinent to the geothermal development are described, including: physiography, demography, economy, and goals and objectives of the citizens as they relate to geothermal development. The geothermal reservoir is characterized on the basis of available information. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperature are indicated. Uses of the energy that seem appropriate to the situation both now and in the near future at Hawthorne are described. The essential institutional requirements for geothermal energy development are discussed, including the financial, environmental, and legal and regulatory aspects. The various steps that are necessary to accomplish the construction of the geothermal district heating system are described.

Not Available

1981-11-04

56

Metsulfuron spray drift reduces fruit yield of hawthorn (Crataegus monogyna L.).  

PubMed

This study was carried out to investigate whether spray drift of metsulfuron has a potential to negatively affect hawthorn (Crataegus monogyna) hedgerows near agricultural fields. For this purpose four doses of metsulfuron ranging from 5% to 40% of the field dose (4 g metsulfuron per hectare) were sprayed on trees in seven different hawthorn hedgerows. The actual deposition on the leaves was measured by means of a tracer (glycine). Spraying was conducted both at the bud stage and at early flowering. Leaves, flowers, green berries and mature berries were harvested and the number and weight of each were measured. The spraying at the bud stage caused a highly significant reduction in number and dry weight of berries, whereas it had no effects on leaf and flower production. The berry reduction was close to 100% at actual depositions relevant for spray drift under normal conditions. Spraying at early flowering also significantly reduced berries although the effect was smaller than for the spraying at bud stage. The early flower stage spraying caused no reduction in number and size of leaves. The possible ecological consequence is that metsulfuron spray drift from agricultural fields has a potential to reduce the amount of berries available for frugivorous birds in nearby hedgerows. A potential need for regulatory measures to reduce herbicide spray drift to hedgerows situated near agricultural fields with herbicide use is also indicated. PMID:15893364

Kjaer, Christian; Strandberg, Morten; Erlandsen, Mogens

2006-03-01

57

Preliminary plan for the development of geothermal energy in the town of Hawthorne, Nevada  

SciTech Connect

The results of the analyses as well as a plan for the development of the geothermal resource are described. Site characteristics pertinent to the geothermal development are described. These characteristics include physiography, demography, economy, and goals and ojectives of the citizens as they would relate to geothermal development. The geothermal resource is described. The reservoir is characterized on the basis of available information. The probable drilling depth to the reservoir, anticipated water production rates, water quality, and resource temperatures ae indicated. Uses of the energy that seem appropriate to the situation both now and in the near future at Hawthorne are described. The amounts and types of energy currently consumed by end users are estimated. Using this data base, conceptual engineering designs and cost estimates for three alternative district heating systems are presented. In addition, the results of a life cycle cost analysis for these alternatives are discussed. The essential institutional requirements for geothermal energy development, including the financial, environmental, and legal and regulatory aspects are discussed. The various steps that are necessary to accomplish the construction of the geothermal district heating system at Hawthorne are described. A time-line chart shows the tasks, the time estimated to be required for each, and the interrelationships among the activities.

Not Available

1981-11-04

58

A comparison of the composition of epicuticular wax from red raspberry ( Rubus idaeus L.) and hawthorn ( Crataegus monogyna Jacq.) flowers  

Microsoft Academic Search

Epicuticular waxes have been characterised from the flowers of raspberry and hawthorn, on both of which adult raspberry beetles (Byturus tomentosus) can feed. The flower wax from both species had similar alkane profiles and also contained long-chain alcohols, aldehydes and fatty acids. The range of the carbon numbers detected for these classes of compounds was broadly similar in both but

D. Wynne Griffiths; Graeme W Robertson; Tom Shepherd; A. Nicholas E Birch; Stuart C Gordon; J. A. Trefor Woodford

2000-01-01

59

A Revised Interpretation of 3D Seismic Data, Hawthorne Army Depot, Nevada: FaultedBasin Reflections or Sill Intrusions?  

E-print Network

Los Angeles Location of Photo Long Valley Caldera WalkerLaneBelt AA B !"##$%&'"()*& !"+%*,&-"%*& N 3d as seen in Long Valley, California (Bursik & Sieh, 1989) (figure 1). Figure 1: (A) Shows Hawthorne located in central western Nevada as well as the location of Long Valley, California. (B) The 3d seismic

60

Literary Work As Travel Guide: The Transformation of N. Hawthorne's THE MARBLE FAUN As A Photographically Illustrated Book  

Microsoft Academic Search

This paper analyzes a very unique photographically illustrated edition of Nathaniel Hawthorne's THE MARBLE FAUN (1860). When the novel was first published in England and the United States, there was no illustration. But soon the English-speaking tourists found the book useful as a guide to the city of Rome and a very special edition with photo images gradually emerged. Its

Yung-Hsiao Cheng

61

Transcript Assembly and Quantification by RNA-Seq Reveals Differentially Expressed Genes between Soft-Endocarp and Hard-Endocarp Hawthorns  

PubMed Central

Hawthorn (Crataegus spp.) is an important pome with a long history as a fruit, an ornamental, and a source of medicine. Fruits of hawthorn are marked by hard stony endocarps, but a hawthorn germplasm with soft and thin endocarp was found in Liaoning province of China. To elucidate the molecular mechanism underlying the soft endocarp of hawthorn, we conducted a de novo assembly of the fruit transcriptome of Crataegus pinnatifida and compared gene expression profiles between the soft-endocarp and the hard-endocarp hawthorn varieties. De novo assembly yielded 52,673 putative unigenes, 20.4% of which are longer than 1,000 bp. Among the high-quality unique sequences, 35,979 (68.3%) had at least one significant match to an existing gene model. A total of 1,218 genes, represented 2.31% total putative unigenes, were differentially expressed between the soft-endocarp hawthorn and the hard-endocarp hawthorn. Among these differentially expressed genes, a number of lignin biosynthetic pathway genes were down-regulated while almost all the flavonoid biosynthetic pathway genes were strongly up-regulated, concomitant with the formation of soft endocarp. In addition, we have identified some MYB and NAC transcription factors that could potentially control lignin and flavonoid biosynthesis. The altered expression levels of the genes encoding lignin biosynthetic enzymes, MYB and NAC transcription factors were confirmed by quantitative RT-PCR. This is the first transcriptome analysis of Crataegus genus. The high quality ESTs generated in this study will aid future gene cloning from hawthorn. Our study provides important insights into the molecular mechanisms underlying soft endocarp formation in hawthorn. PMID:24039819

Zhang, Feng; Liu, Zhongchi; Li, Xiaoming; Li, Wenran; Ma, Yue; Li, He; Liu, Yuexue; Zhang, Zhihong

2013-01-01

62

Transcript assembly and quantification by RNA-Seq reveals differentially expressed genes between soft-endocarp and hard-endocarp hawthorns.  

PubMed

Hawthorn (Crataegus spp.) is an important pome with a long history as a fruit, an ornamental, and a source of medicine. Fruits of hawthorn are marked by hard stony endocarps, but a hawthorn germplasm with soft and thin endocarp was found in Liaoning province of China. To elucidate the molecular mechanism underlying the soft endocarp of hawthorn, we conducted a de novo assembly of the fruit transcriptome of Crataegus pinnatifida and compared gene expression profiles between the soft-endocarp and the hard-endocarp hawthorn varieties. De novo assembly yielded 52,673 putative unigenes, 20.4% of which are longer than 1,000 bp. Among the high-quality unique sequences, 35,979 (68.3%) had at least one significant match to an existing gene model. A total of 1,218 genes, represented 2.31% total putative unigenes, were differentially expressed between the soft-endocarp hawthorn and the hard-endocarp hawthorn. Among these differentially expressed genes, a number of lignin biosynthetic pathway genes were down-regulated while almost all the flavonoid biosynthetic pathway genes were strongly up-regulated, concomitant with the formation of soft endocarp. In addition, we have identified some MYB and NAC transcription factors that could potentially control lignin and flavonoid biosynthesis. The altered expression levels of the genes encoding lignin biosynthetic enzymes, MYB and NAC transcription factors were confirmed by quantitative RT-PCR. This is the first transcriptome analysis of Crataegus genus. The high quality ESTs generated in this study will aid future gene cloning from hawthorn. Our study provides important insights into the molecular mechanisms underlying soft endocarp formation in hawthorn. PMID:24039819

Dai, Hongyan; Han, Guofen; Yan, Yujiao; Zhang, Feng; Liu, Zhongchi; Li, Xiaoming; Li, Wenran; Ma, Yue; Li, He; Liu, Yuexue; Zhang, Zhihong

2013-01-01

63

Phytochemical characterization of several hawthorn (Crataegus spp.) species sampled from the Eastern Mediterranean region of Turkey  

PubMed Central

Background: We evaluated the total phenolic content, antioxidant capacity as well as antioxidant activity of five Crataegus species (A1, A2, Y1, Y2, Y4 accessions of Crataegus aronia var. aronia; B2, B3, B5, B6, B7, B9, Y5 accessions of C. aronia var. dentata; B10 accession of C. aronia var. minuta; Y3 accession of Crataegus orientalis var. orientalis and A3 accession of Crataegus monogyna subsp. azarella). Materials and Methods: Antioxidant activity and total phenolic content of fruits were determined by ?-carotene bleaching and Folin–Ciocalteu assays. Antioxidant capacity was determined by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Results: C. monogyna subsp. azarella had the highest total phenol, antioxidant activity and antioxidant capacity of 55.2 mg gallic acid equivalents (GAE)/g dry weight (DW), 81.9% and 31.2%, respectively. C. aronia var. aronia was found to have the lowest total phenolic content (35.7 mg GAE/g DW). The antioxidant activities of fruit extracts increased in the order of C. orientalis var. orientalis < C. aronia var. minuta < C. aronia var. dentata < C. aronia var. aronia < C. monogyna subsp. azarella according to ?-carotene/linoleic acid assay. In recent years, C. aronia var. dentata has gained importance as a commercial species in this region. B3 and B7 accessions had fruit weight more than 14 g, and considerable total phenol content, antioxidant activity and antioxidant capacity. Conclusion: This investigation shows the potential value of hawthorn fruit species as a good source of natural antioxidants and that consumption of hawthorn fruit or its products may contribute substantial amounts of antioxidants to the diet. PMID:22438658

Caliskan, Oguzhan; Gunduz, Kazim; Serce, Sedat; Toplu, Celil; Kamiloglu, Onder; Sengul, Memnune; Ercisli, Sezai

2012-01-01

64

Panafrican distribution of Lower Miocene Hominoidea  

NASA Astrophysics Data System (ADS)

Palaeontological survey of the Neogene littoral deposits of the Namaqualand coastal strip, Northern Cape Province, South Africa, has resulted in the collection of the first Lower Miocene faunas from South Africa. Among the mammals from Ryskop and Hondeklip Bay is a gorilla-sized hominoid. This discovery greatly increases the geographic range of early Miocene hominoids and suggests that even at this remote epoch, the superfamily had a Panafrican distribution.

Senut, Brigitte; Pickford, Martin; Wessels, Dudley

1997-11-01

65

Updated chronology for the Miocene hominoid radiation in Western Eurasia  

PubMed Central

Extant apes (Primates: Hominoidea) are the relics of a group that was much more diverse in the past. They originated in Africa around the Oligocene/Miocene boundary, but by the beginning of the Middle Miocene they expanded their range into Eurasia, where they experienced a far-reaching evolutionary radiation. A Eurasian origin of the great ape and human clade (Hominidae) has been favored by several authors, but the assessment of this hypothesis has been hampered by the lack of accurate datings for many Western Eurasian hominoids. Here we provide an updated chronology that incorporates recently discovered Iberian taxa and further reevaluates the age of many previously known sites on the basis of local biostratigraphic scales and magnetostratigraphic data. Our results show that identifiable Eurasian kenyapithecins (Griphopithecus and Kenyapithecus) are much younger than previously thought (ca. 14 Ma instead of 16 Ma), which casts serious doubts on the attribution of the hominoid tooth from Engelswies (16.3–16.5 Ma) to cf. Griphopithecus. This evidence is further consistent with an alternative scenario, according to which the Eurasian pongines and African hominines might have independently evolved in their respective continents from similar kenyapithecin ancestors, resulting from an early Middle Miocene intercontinental range extension followed by vicariance. This hypothesis, which would imply an independent origin of orthogrady in pongines and hominines, deserves further testing by accurately inferring the phylogenetic position of European dryopithecins, which might be stem pongines rather than stem hominines. PMID:21436034

Casanovas-Vilar, Isaac; Alba, David M.; Garces, Miguel; Robles, Josep M.; Moya-Sola, Salvador

2011-01-01

66

Allopolyploidy, diversification, and the Miocene grassland expansion  

PubMed Central

The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation. PMID:25288748

Estep, Matt C.; McKain, Michael R.; Vela Diaz, Dilys; Zhong, Jinshun; Hodge, John G.; Hodkinson, Trevor R.; Layton, Daniel J.; Malcomber, Simon T.; Pasquet, Remy; Kellogg, Elizabeth A.

2014-01-01

67

Allopolyploidy, diversification, and the Miocene grassland expansion.  

PubMed

The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation. PMID:25288748

Estep, Matt C; McKain, Michael R; Vela Diaz, Dilys; Zhong, Jinshun; Hodge, John G; Hodkinson, Trevor R; Layton, Daniel J; Malcomber, Simon T; Pasquet, Rémy; Kellogg, Elizabeth A

2014-10-21

68

Abundance of apple maggot, Rhagoletis pomonella, across different areas in central Washington, with special reference to black-fruited hawthorns.  

PubMed

The apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), infests non-commercial apple (Malus domestica (Borkh.) Borkh.) and native black-fruited hawthorns (mostly Crataegus douglasii Lindl.) in central Washington, but little has been published on the abundance of the fly in this region. In this paper, the abundance of R. pomonella across different sites near apple-growing areas in central Washington is documented in order to assess the threat of the fly to commercial apple orchards. The fly was first detected on traps in Klickitat, Yakima, and Kittitas Counties in 1981, 1995, and 1997, respectively. From 1981-2010 in Kittitas and Yakima Counties, only 0 to 4.7% of traps on apple, crabapple, and hawthorn trees were positive for flies, whereas in Klickitat County, located farther from commercial apple orchards, 0 to 41.9% of traps were positive. In 2008, in Yakima County and Goldendale in Klickitat County, 7.8% of black-fruited hawthorn trees were infested, with 0 to 0.00054 larvae per fruit. In 2010, in Kittitas and Yakima Counties and Goldendale in Klickitat County, 25.0% of C. douglasii trees were infested, with 0.00042 to 0.00248 larvae per fruit. In 2010, in a remote forested area of Klickitat County far from commercial apple orchards, 94.7% of C. douglasii trees were infested, with 0.20813 larvae per fruit. Overall results suggest R. pomonella is unlikely to develop high populations rapidly near major commercial apple-growing areas in central Washington, including in black-fruited hawthorns, increasing chances it can be kept out of commercial orchards. PMID:23451979

Yee, Wee L; Klaus, Michael W; Cha, Dong H; Linn, Charles E; Goughnour, Robert B; Feder, Jeffrey L

2012-01-01

69

Identification of fruit volatiles from green hawthorn (Crataegus viridis) and blueberry hawthorn (Crataegus brachyacantha) host plants attractive to different phenotypes of Rhagoletis pomonella flies in the southern United States.  

PubMed

The apple maggot fly, Rhagoletis pomonella, infests several hawthorn species in the southern USA. In a companion paper, we showed that R. pomonella flies infesting two different mayhaw species (Crataegus opaca and C. aestivalis) can discriminate between volatile blends developed for each host fruit, and that these blends are different from previously constructed blends for northern fly populations that infest domestic apple (Malus domestica), downy hawthorn (Crataegus mollis), and flowering dogwood (Cornus florida). Here, we show by using coupled gas chromatography and electroantennographic detection (GC-EAD), gas chromatography with mass spectrometry (GC-MS), and flight tunnel bioassays, that two additional southern hawthorn fly populations infesting C. viridis (green hawthorn) and C. brachyacantha (blueberry hawthorn) also can discriminate between volatile blends for each host fruit type. A 9-component blend was developed for C. viridis (3-methylbutan-1-ol [5%], butyl butanoate [19.5%], propyl hexanoate [1.5%], butyl hexanoate [24%], hexyl butanoate [24%], pentyl hexanoate [2.5%], 1-octen-3-ol [0.5%], pentyl butanoate [2.5%], and (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) [20.5%]) and an 8-component blend for C. brachyacantha (3-methylbutan-1-ol [0.6%], butyl acetate [50%], pentyl acetate [3.5%], butyl butanoate [9%], butyl hexanoate [16.8%], hexyl butanoate [16.8%], 1-octen-3-ol [0.3%], and pentyl butanoate [3%]). Crataegus viridis and C. brachyacantha-origin flies showed significantly higher levels of upwind oriented flight to their natal blend in flight tunnel assays compared to the alternate, non-natal blend and previously developed northern host plant blends. The presence of DMNT in C. viridis and butyl acetate in C. brachyacantha appeared to be largely responsible for driving the differential response. This sharp behavioral distinction underscores the diversity of odor response phenotypes in the southern USA, points to possible host race formation in these populations, and despite the presence of several apple volatiles in both blends, argues against a functional apple race existing on southern host plants prior to the introduction of apple to North America. PMID:21887525

Cha, Dong H; Powell, Thomas H Q; Feder, Jeffrey L; Linn, Charles E

2011-09-01

70

Hawthorn-infesting populations of Rhagoletis pomonella in Mexico and speciation mode plurality.  

PubMed

Categorizing speciation into dichotomous allopatric versus nonallopatric modes may not always adequately describe the geographic context of divergence for taxa. If some of the genetic changes generating inherent barriers to gene flow between populations evolved in geographic isolation, whereas others arose in sympatry, then the mode of divergence would be mixed. The apple maggot fly, Rhagoletis pomonella, has contributed to this emerging concept of a mixed speciation mode "plurality." Genetic studies have implied that a source of diapause life-history variation associated with inversions and contributing to sympatric host race formation and speciation for R. pomonella in the United States may have introgressed from the Eje Volcanico Trans Mexicano (EVTM; a.k.a. the Altiplano) in the past. A critical unresolved issue concerning the introgression hypothesis is how past gene flow occurred given the current 1200-km disjunction in the ranges of hawthorn-infesting flies in the EVTM region of Mexico and the southern extreme of the U.S. population in Texas. Here, we report the discovery of a hawthorn-infesting population of R. pomonella in the Sierra Madre Oriental Mountains (SMO) of Mexico. Sequence data from 15 nuclear loci and mitochondrial DNA imply that the SMO flies are related to, but still different from, U.S. and EVTM flies. The host affiliations, diapause characteristics, and phylogeography of the SMO population are consistent with it having served as a conduit for gene flow between Mexico and the United States. We also present evidence suggesting greater permeability of collinear versus rearranged regions of the genome to introgression, in accord with recent models of chromosomal speciation. We discuss the implications of the results in the context of speciation mode plurality. We do not argue for abandoning the terms sympatry or allopatry, but caution that categorizing divergence into either/or geographic modes may not describe the genetic origins of all species. For R. pomonella in the United States, the proximate selection pressures triggering race formation and speciation stem from sympatric host shifts. However, some of the phenological variation contributing to host-related ecological adaptation and reproductive isolation in sympatry at the present time appears to have an older history, having originated and become packaged into inversion polymorphism in allopatry. PMID:17492964

Xie, Xianfa; Rull, Juan; Michel, Andrew P; Velez, Sebastian; Forbes, Andrew A; Lobo, Neil F; Aluja, Martin; Feder, Jeffrey L

2007-05-01

71

Additional material of the enigmatic Early Miocene mammal Kelba and its relationship to the order Ptolemaiida  

PubMed Central

Kelba quadeemae, a fossil mammal from the Early Miocene of East Africa, was originally named on the basis of three isolated upper molars. Kelba has previously been interpreted as a creodont, a pantolestid, an insectivoran, and a hemigaline viverrid. The true affinities of this taxon have remained unclear because of the limited material and its unique morphology relative to other Miocene African mammals. New material of Kelba from several East African Miocene localities, most notably a skull from the Early Miocene locality of Songhor in Western Kenya, permits analysis of the affinities of Kelba and documents the lower dentition of this taxon. Morphological comparison of this new material clearly demonstrates that Kelba is a member of the order Ptolemaiida, a poorly understood group whose fossil record was previously restricted to the Oligocene Fayum deposits of northern Egypt. Phylogenetic analysis supports the monophyly of the Ptolemaiida, including Kelba, and recovers two monophyletic clades within the order. We provide new family names for these groups and an emended diagnosis for the order. The discovery of ptolemaiidans from the Miocene of East Africa is significant because it extends the known temporal range of the order by >10 million years and the geographic range by >3,200 km. Although the higher-level affinities of the Ptolemaiida remain obscure, their unique morphology and distribution through a larger area of Africa (and exclusively Africa) lend support to the idea that Ptolemaiida may have an ancient African origin. PMID:17372202

Cote, Susanne; Werdelin, Lars; Seiffert, Erik R.; Barry, John C.

2007-01-01

72

Miocene reef carbonates of Mariana Islands  

SciTech Connect

Miocene carbonates in the southern Mariana Islands are impressive for their lithologic diversity, thicknesses (over 250 m), and geographic extent (> 20% combined outcrop coverage over four major high islands: Guam, Rota, Tinian and Saipan). Sections are dominated either by lagoonal algal-foraminiferal wackestones and mudstones with locally abundant high-energy shelly-skeletal facies, or by rubbly to muddy, fore-reef-to-bank deposits of packstones and grainstones with highly diverse and variable biogenic clasts. Fresh to deeply weathered volcaniclastic material may comprise at least 80% of some high-energy fore-reef facies, whereas lagoonal and bank deposits usually contain less than 0.5% terrigenous material. Surprisingly, the Miocene in the Marianas lacks almost completely any reef-core facies. Several poorly developed coral-rich mounds on Saipan and localized laminated red algal buildups on Guam appear to constitute the extant reef-wall facies in the Miocene. The lack of buildups may be a matter of differential survival; it may result from headland erosion and benching associated with emergence of narrow reef tracts as has been postulated by others for south Guam. Alternatively, the authors are proposing that Miocene bathymetry and the volume of terrigenous influx militated against significant reef core formation. Radiometric age dating of these reef carbonates has proven unsuccessful because pervasive diagenesis has transformed the entire Miocene section into low-magnesium calcite with minor and occasional dolomite. Freshwater phreatic diagenesis accounts for the principal porosity variation and trace element distribution.

Siegrist, H.G. Jr.

1988-02-01

73

Nanomechanics and Sodium Permeability of Endothelial Surface Layer Modulated by Hawthorn Extract WS 1442  

PubMed Central

The endothelial glycocalyx (eGC) plays a pivotal role in the physiology of the vasculature. By binding plasma proteins, the eGC forms the endothelial surface layer (ESL) which acts as an interface between bloodstream and endothelial cell surface. The functions of the eGC include mechanosensing of blood flow induced shear stress and thus flow dependent vasodilation. There are indications that levels of plasma sodium concentrations in the upper range of normal and beyond impair flow dependent regulation of blood pressure and may therefore increase the risk for hypertension. Substances, therefore, that prevent sodium induced endothelial dysfunction may be attractive for the treatment of cardiovascular disease. By means of combined atomic force - epifluorescence microscopy we studied the impact of the hawthorn (Crataegus spp.) extract WS 1442, a herbal therapeutic with unknown mechanism of action, on the mechanics of the ESL of ex vivo murine aortae. Furthermore, we measured the impact of WS 1442 on the sodium permeability of endothelial EA.hy 926 cell monolayer. The data show that (i) the ESL contributes by about 11% to the total endothelial barrier resistance for sodium and (ii) WS 1442 strengthens the ESL resistance for sodium up to about 45%. This mechanism may explain some of the vasoprotective actions of this herbal therapeutic. PMID:22253842

Peters, Wladimir; Drueppel, Verena; Kusche-Vihrog, Kristina; Schubert, Carola; Oberleithner, Hans

2012-01-01

74

Miocene precursors to Great Barrier Reef  

SciTech Connect

Huge reefs of Miocene age are present in the Gulf of Papua north of the present-day Great Barrier Reef and to the east on the Marion and Queensland Plateaus. In the Gulf of Papua, Miocene barrier reefs formed the northern forerunner of the Great Barrier Reef, extending for many hundreds of kilometers along the eastern and northern margin of the Australian craton within a developing foreland basin. Barrier reefs, slope pinnacle reefs, and platform reefs are seen in seismic sections and drill holes. Leeside talus deposits testify to the high energy impinging on the eastern margin of these Miocene reefs. The Queensland Plateau is a marginal plateau east of the central Great Barrier Reef and separated from it by a rift trough. Miocene reefs occupied an area of about 50,000 km/sup 2/ and grew on salt-controlled highs on the western margin of the plateau and on a regional basement high extending from the platform interior to its southern margin. Reef growth has continued to the present day, although two major contractions in the area covered by reefs occurred during the Miocene. The Marion Plateau is present directly east of the Great Barrier Reef and during the Micoene formed a 30,000-km/sup 2/ platform with barrier reefs along its northern margin and huge platform reefs and laggons on the platform interior. These reefs grew on a flat peneplained surface, the whole area forming a large shallow epicontinental sea. In all three areas, the middle Miocene formed the acme of reef expansion in the region.

Davies, P.J.; Symonds, P.A.; Feary, D.A.; Pigram, C.

1988-01-01

75

A warm Miocene climate at low atmospheric CO2 levels  

Microsoft Academic Search

Proxy records from the Miocene epoch (~23-5 Ma) indicate a warmer climate than today in spite of lower atmospheric carbon dioxide (CO2) concentrations in the range of preindustrial levels. As yet the simulation of a warm Miocene climate with these low CO2 values has proven to be a challenge. In this study we present climate simulations of the Late Miocene

G. Knorr; M. Butzin; A. Micheels; G. Lohmann

2011-01-01

76

Aquifer characteristics and water quality of Miocene–Pleistocene sediments, Kuwait  

Microsoft Academic Search

Al-Atraf is one of the water well fields of Kuwait supplying Kuwait City with the brackish groundwater obtained from the Kuwait Group aquifer of Miocene–Pleistocene age. The study determined the hydrogeological and hydrochemical characteristics of the groundwater in order to identify the major chemical processes that influence the groundwater quality of the study area. The results of the aquifer test

F. M. Al-Ruwaih; H. A. Qabazard

2005-01-01

77

Miocene reef carbonates of Mariana Islands  

SciTech Connect

Miocene carbonates in the southern Mariana Islands are impressive for their lithologic diversity, thicknesses (over 250 m), and geographic extend (>20% combined outcrop coverage over four major high islands: Guam, Rota, Tinian and Saipan). Sections are dominated either by lagoonal algal-foraminiferal wackestones and mudstones with locally abundant high-energy shelly-skeletal facies, or by rubbly to muddy, fore-reef-to-bank deposits of packstones and grainstones with highly diverse and variable biogenic clasts. Fresh to deeply weathered volcaniclastic material may comprise at least 80% of some high-energy fore-reef facies, whereas lagoonal and bank deposits usually contain less than 0.5% terrigenous material. Surprisingly, the Miocene in the Marianas lacks almost completely any reef-core facies. Several poorly developed coral-rich mounds on Saipan and localized laminated red algal buildups on Guam appear to constitute the extant reef-wall facies in the Miocene. The lack of buildups may be a matter of differential survival; it may result from headland erosion and benching associated with emergency of narrow reef tracts as has been postulated by others for south Guam. Radiometric age dating of these reef carbonates has proven unsuccessful because pervasive diagenesis has transformed the entire Miocene section into low-magnesium calcite with minor and occasional dolomite. Freshwater phreatic diagenesis accounts for the principal porosity variation and trace element distribution.

Siegrist, H.G. Jr.

1988-01-01

78

Murky details of the Miocene Atlantic Ocean  

NASA Astrophysics Data System (ADS)

We examine Atlantic Ocean circulation during the Miocene based on published modelling and data. It has long been recognised that the Atlantic Ocean played a key role in climate changes throughout the Quaternary and determining whether this was the case earlier in the Cenozoic may be important for understanding the details of Miocene climate evolution. Current geochemical, sedimentological and micropaleontologic evidence allows for multiple interpretations of deep water activity, which is further hampered by a lack of precise dating of ocean gateway closures. Previous ocean modelling studies have shown strong increases in deep water formation due to closure of the Panama gateway but have disagreed on the oceanographic importance of the Tethys gateway and bathymetry of the far North Atlantic. This combination of ambiguous data and conflicting modelling results leaves the current state of knowledge of the Miocene ocean lacking. We propose several avenues of research to improve our knowledge of the Miocene Atlantic Ocean, which will ultimately improve our understanding of its response to climate change and vice versa.

Herold, N. K.; Huber, M.; Shevenell, A.; Müller, D.

2013-12-01

79

The genetic structure of hawthorn-infesting Rhagoletis pomonella populations in Mexico: implications for sympatric host race formation.  

PubMed

The genetic origins of species may not all trace to the same time and place as the proximate cause(s) for population divergence. Moreover, inherent gene-flow barriers separating populations may not all have evolved under the same geographical circumstances. These considerations have lead to a greater appreciation of the plurality of speciation: that one geographical mode for divergence may not always be sufficient to describe a speciation event. The apple maggot fly, Rhagoletis pomonella, a model system for sympatric speciation via host-plant shifting, has been a surprising contributor to the concept of speciation mode plurality. Previous studies have suggested that past introgression of inversion polymorphism from a hawthorn-fly population in the trans-Mexican volcanic belt (EVTM) introduced diapause life-history variation into a more northern fly population that subsequently contributed to sympatric host race formation and speciation in the United States (US). Here, we report results from a microsatellite survey implying (i) that volcanic activity in the eastern EVTM may have been responsible for the initial geographical isolation of the Mexican and northern hawthorn-fly populations c. 1.57 mya; and (ii) that flies in the Sierra Madre Oriental Mountains (SMO) likely served as a conduit for past gene flow from the EVTM into the US. Indeed, the microsatellite data suggest that the current US population may represent a range expansion from the northern SMO. We discuss the implications of these findings for sympatric race formation in Rhagoletis and speciation theory. PMID:17614903

Michel, Andrew P; Rull, Juan; Aluja, Martin; Feder, Jeffrey L

2007-07-01

80

The westernmost tarsier: a new genus and species from the Miocene of Pakistan.  

PubMed

As the closest living sister group of anthropoids, tarsiers (Family Tarsiidae) are an important group in primate evolution. However, their fossil record is poor: only four species have been described, two from the Eocene of China and two from the Miocene of Thailand. All are from outside the range of the living species, which occur only on islands off Southeast Asia. Here, we describe a new fossil tarsier from Pakistan, a significant range extension. This record consists of two lower molars, an upper molar, and a lower premolar found in the Miocene Manchar Formation (~18-16 Ma [millions of years ago]) of Sindh Province, southern Pakistan. The Pakistani tarsier is morphologically distinct from all living and fossil tarsiers, but most similar to the middle Miocene Thai species Tarsius thailandicus. Though living tarsiers have traditionally been classified in a single genus, a recent revision proposed a division into three genera, which is strongly supported by molecular data. The Pakistani species is not referable to any of these genera, and we create for it and T. thailandicus a new tarsiid genus. This discovery broadens our understanding of the geographic range and morphological diversity of Miocene tarsiers and helps to put the living tarsiers into their evolutionary context. PMID:23928350

Zijlstra, Jelle S; Flynn, Lawrence J; Wessels, Wilma

2013-11-01

81

Oligocene early Miocene Antarctic nearshore diatom biostratigraphy  

Microsoft Academic Search

Lower Oligocene (ca. 31 Ma) to lower Miocene (ca. 18.5 Ma) biosiliceous microfossils recovered from the Cape Roberts Project (CRP-2\\/2A) drill cores provide both paleoenvironmental and biostratigraphic information, enhancing our understanding of the geological history of the Victoria Land Basin, Antarctica. The biochronostratigraphic record obtained provides key data with which time space facies models may be developed. Assemblages of neritic

Matthew P. Olney; Reed P. Scherer; David M. Harwood; Steven M. Bohaty

2007-01-01

82

Late Miocene “washhouse” climate in Europe  

Microsoft Academic Search

We present two eight-million year long proxy records of precipitation for Southwest and Central Europe, covering the middle to late Miocene (5.3–13 Ma) at a temporal resolution of about 60 kyr and 150 kyr, respectively. The estimates of precipitation are based on the ecophysiological structure of herpetological assemblages (amphibians and reptiles). From 13.0 Ma until about 9 Ma, both records show a similar trend, evolving

Madelaine Böhme; August Ilg; Michael Winklhofer

2008-01-01

83

Miocene cercopithecoidea from the Tugen Hills, Kenya.  

PubMed

Miocene to Pleistocene fossiliferous sediments in the Tugen Hills span the time period from at least 15.5 Ma to 0.25 Ma, including time periods unknown or little known elsewhere in Africa. Consequently, the Tugen Hills deposits hold the potential to inform us about crucial phylogenetic events in African faunal evolution and about long-term environmental change. Among the specimens collected from this region are a number of discoveries already important to the understanding of primate evolution. Here, we describe additional cercopithecoid material from the Miocene deposits in the Tugen Hills sequence, including those from securely dated sites in the Muruyur Beds (16-13.4 Ma), the Mpesida Beds (7-6.2 Ma) and the Lukeino Formation (? 6.2-5.7 Ma). We also evaluate previously described material from the Ngorora Formation (13-8.8 Ma). Identified taxa include Victoriapithecidae gen. et sp. indet., cf. Parapapio lothagamensis, and at least two colobines. Specimens attributed to cf. Pp. lothagamensis would extend the species' geographic range beyond its type locality. In addition, we describe specimens sharing derived characters with modern African colobines (Tribe: Colobina), a finding that is congruent with previous molecular estimates of colobine divergence dates. These colobine specimens represent some of the earliest known members of the modern African colobine radiation and, in contrast to previous hypotheses, suggest that early African colobines were mainly arboreal and that semi-terrestrial Late Miocene and Plio-Pleistocene colobine taxa were secondarily derived in their locomotor adaptations. PMID:20889183

Gilbert, Christopher C; Goble, Emily D; Hill, Andrew

2010-11-01

84

Miocene rifting of Fuerteventura (Canary Islands)  

NASA Astrophysics Data System (ADS)

The older geological units of the volcanic island of Fuerteventura (Canary Islands), i.e., the so-called basal complex and the lower part of the subaerial volcanic rocks, show abundant structures indicative of a long-lived period of Miocene tectonic activity. These structures include faults, dike swarms, kilometer-scale folds, tilted sequences, and fissural and central volcanic edifices. A detailed structural study, based on geological mapping and the use of fault slip inversion techniques and statistical analysis of dike orientation, has allowed the identification of three separated Miocene deformation phases: M-D1, M-D2, and M-D3. The average extension directions determined for these phases are NW-SE, NNE-SSW, and ENE-WSW, respectively. A model of oceanic lithosphere rifting is proposed to account for this deformation history. A buoyant, anomalous sublithosphere mantle triggered the extension in the lithosphere beneath Fuerteventura, isolating it during the early and middle Miocene from the plate-scale collision regime predominant in the NW corner of the African plate.

FernáNdez, Carlos; Casillas, Ramón; GarcíA Navarro, Encarnación; GutiéRrez, Margarita; Camacho, Manuel A.; Ahijado, Agustina

2006-12-01

85

Paleomagnetism of the Miocene Columbia River Basalt Group in Oregon and Washington from the Pacific Coast to the Columbia Plateau: Magnetostratigraphy, Vertical-Axis Rotations, Paleosecular Variation, and Remagnetization  

NASA Astrophysics Data System (ADS)

Identification of individual flows within the Columbia River Basalt Group (CRBG) has mostly relied on minor differences in geochemistry, but magnetic polarity has also proved useful in differentiating flows and establishing a temporal framework. Within the thick, rapidly erupted Grande Ronde Basalt four major polarity chrons (R1 to N2) have been identified. Because cooling times of CRBG flows are brief compared to rates of paleosecular variation (PSV), within-flow paleomagnetic directions are expected to be constant across the extensive east-west reaches of these flows. Vertical-axis rotations in OR and WA, driven by northward-oblique subduction of the Juan de Fuca plate, thus can be measured by comparing directions for western sampling localities to directions for the same flow units on the relatively stable Columbia Plateau. Clockwise rotations calculated for outcrop locations within the Coast Range (CR) block are uniformly about 30° (N=102 sites). East of the northwest-trending en échelon Mt. Angel-Gales Creek, Portland Hills, and northern unnamed fault zones, as well as north of the CR block's northern boundary (~Columbia River), clockwise rotations abruptly drop to about 15° (N=39 sites), with offsets in these bounding fault zones corresponding to the Portland and Willamette pull-apart basins. The general agreement of vertical- axis rotation rates estimated from CRBG magnetizations with those determined from modern GPS velocities indicates a relatively steady rate over the last 10 to 15 Myr. Unusual directions due to PSV, field excursions, or polarity transitions could provide useful stratigraphic markers. Individual flow directions, however, have not been routinely used to identify flows. One reason this has been difficult is that remagnetization is prevalent, particularly in the Coast Ranges, coupled with earlier demagnetization techniques that did not completely remove overprint components. Except for the Ginkgo and Pomona flows of the Wanapum and Saddle Mountains Basalts, reference Plateau directions for the CRBG are poorly known. Moreover, field and drill- core relations indicate that flows with different chemistries were erupted at the same time. Renewed sampling, therefore, has been undertaken eastward from the Portland area into the Columbia River Gorge and out onto the Plateau. Resampling of the Patrick Grade section (23 flows) in southeastern WA has shown that overprint magnetizations were not successfully removed in many flows at this locality in an earlier study [1]. This brings into question blanket demagnetization studies of the CRBG as well as polarity measurements routinely made in the field with hand-held fluxgate magnetometers. [1] Choiniere and Swanson, 1979, Am. J. Sci., 279, p. 755

Hagstrum, J. T.; Wells, R. E.; Evarts, R. C.; Niem, A. R.; Sawlan, M. G.; Blakely, R. J.

2008-12-01

86

JF\\H:\\data\\maps-library\\Hawthorn Library Map_2014_April.doc/11/04/2014 Hawthorn Campus Library Map  

E-print Network

Library Conference Room LB311 (Penang Room) Group Study Rooms 3A 3B Group Study Rooms 3C 3D Computers 2 April 2014 Level 1 ­ Journal / Microfilm Collection Level 2 ­ Recreational Reading / Subject Materials (Reserve) Collection JohnStreet Printers/card machine Carrels, desks Fire Escape Stairs EW Lifts & Toilets

Liley, David

87

Retained Hawthorn fragment in a child's foot complicated by infection: diagnosis and excision aided by localization with ultrasound.  

PubMed

Puncture wounds in children are very common and often result in foreign body retention. Organic materials in the form of plant thorns present problems in identification and localization because they are not visualized with plain radiographs. A case of a 10-year-old girl with a small piece of retained hawthorn is presented. Correct diagnosis and treatment were delayed because of misinterpretation of magnetic resonance image studies. Ultrasound ultimately located the foreign body, and assisted in its excision. Plant thorns may be toxic and produce an intense local inflammatory response. In the case described in this article, deep infection caused by Enterobacter cloacae and Pantoea agglomerans was associated with the retained thorn. The small size of the foreign body, misinterpretation of diagnostic images, and the deep infection highlight the challenges that can be encountered by physicians managing puncture wounds in children. PMID:19962326

Harris, Edwin J

2010-01-01

88

Petrofacies and provenance of the Puente Formation (middle to upper Miocene), Los Angeles basin, southern California: Implications for rapid uplift and accumulation rates  

Microsoft Academic Search

The Peunte Formation is a Middle-Upper Miocene clastic unit lying unconformably on the Lower-Middle Miocene El Modeno Volcanics and Topanga Group, in the Los Angeles basin. The Puente Formation, about 3900 m thick, is composed of conglomerate, sandstone, and mudrock deposit;ed as a submarine fan at bathyal depths. Several intrabasinal discordances suggest tectonic activity during deposition. The succession consists of

S. Critelli; P. E. Rumelhart; R. V. Ingersoll

1995-01-01

89

Opal and organic carbon in laminated diatomaceous sediments: Saanich Inlet, Santa Barbara Basin and the Miocene Monterey Formation  

Microsoft Academic Search

Laminated biosiliceous sediments from Saanich Inlet, British Columbia (SI), the Monterey Formation, California (MF), and Santa Barbara Basin, California (SBB) are organic-rich and were studied to assess the suitability of SI and SBB as modern analogs of the Miocene MF and to explore the controls on distributions of opal and organic carbon. To this end, individual laminae and groups of

K. M Johnson; K. A Grimm

2001-01-01

90

A paleo-Brahmaputra? Subsurface lithofacies analysis of Miocene deltaic sediments in the Himalayan Bengal system, Bangladesh  

NASA Astrophysics Data System (ADS)

The Bengal foreland basin contains a succession of up to 16+ km of dominantly deltaic deposits, eroded from the eastern Himalayas and the Indo-Burman ranges and carried by major river systems similar to the present-day Ganges and Brahmaputra. Analysis of electric logs and core descriptions acquired during oil and gas exploration in Bangladesh allows construction of lithofacies maps, which constrain depositional patterns of Miocene strata. Compilations of sand thickness and sand/shale ratio of the Miocene Surma Group show that Lower to Middle Miocene strata of the Bhuban Formation accumulated in a large, elongate trough. Sand thickness and percentage both decrease markedly away from this depocenter, which describes a large-scale bend, running initially westward from Rashidpur (northeast Bengal basin) and curving southward toward the Bengal fan. Middle to Upper Miocene strata of the Boka Bil Formation show a similar geographic trend in deposition of coarsest and thickest sediment, but the major depocenter had shifted northward relative to that of the Bhuban Formation by some 30 km, passing near Beani Bazar. These trends suggest that deltaic deposits of the Surma Group filled the Sylhet trough of the northeast Bengal basin from the east. Published seismic data from western Bangladesh show that additional large channels also contributed materials to the Bengal basin from the northwest during the Late Miocene, but these channels resulted in very little accumulation in the northwestern part of the basin, probably due to restricted subsidence of underlying continental crust. This study suggests that there was a major drainage system similar to the modern Brahmaputra River during Miocene time, which carried orogenic sediments eroded from the uplifted terranes of the eastern Himalayas and Indo-Burman ranges to the eastern Bengal delta.

Uddin, Ashraf; Lundberg, Neil

1999-02-01

91

Grouping  

NSDL National Science Digital Library

This interactive Flash applet models the measurement interpretation of division. A child or teacher chooses a total number of objects and a divisor representing the size of equal groups. The applet allows the user to move the objects into equal groups and links the process to jumps on a number line. The applet can be used to introduce children to remainders and to reinforce the language and notation of division. It works well on an interactive white board or projector. A teacher's guide to this collection of applets is cataloged separately.

2006-01-01

92

Optimization of high-speed counter-current chromatography for separation of polyphenols from the extract of hawthorn ( Crataegus laevigata) with response surface methodology  

Microsoft Academic Search

Separation and purification of polyphenols from the extract of hawthorn (Crataegus laevigata) was investigated with high-speed counter-current chromatography (HSCCC). Solvent systems were examined according to partition coefficients of target components and n-butanol–ethyl acetate–water (1:1:2, v\\/v\\/v) system was chosen. The critical experimental parameters of HSCCC were optimized and determined with response surface methodology (RSM) as following: Revolution speed was 850rpm, flow-rate

Hai-Yan Cui; Xiao-Yan Jia; Xia Zhang; Jing Zhang; Zhi-Qi Zhang

2011-01-01

93

Middle and upper Miocene natural gas sands in onshore and offshore Alabama  

Microsoft Academic Search

Thirty Miocene natural gas fields have been established in onshore and offshore Alabama since the discovery of Miocene gas in this area in 1979. These fields have produced over 16 bcf of natural gas from the middle Miocene Amos sand (24 fields) and upper Miocene Luce (3 fields), Escambia (1 field), and Meyer (3 fields) sands. Production from the Amos

R. M. Mink; E. A. Mancini; B. L. Bearden; C. C. Smith

1988-01-01

94

Giant Miocene landslides and the evolution of Fuerteventura  

Microsoft Academic Search

Fuerteventura is the oldest island in the Canaries archipelago; following the growth of a pre-Miocene seamount, its shield stage began 20.6 Ma ago, and ended in the mid-Miocene. There followed a very extended period of quiescence, then very minor Quaternary post-erosional volcanism. The shield stage produced volcanoes up to 3000 m above sea level which were rapidly eroded by 17.5

Canary Islands; C. J. Stillman

95

Giant Miocene landslides and the evolution of Fuerteventura, Canary Islands  

Microsoft Academic Search

Fuerteventura is the oldest island in the Canaries archipelago; following the growth of a pre-Miocene seamount, its shield stage began 20.6 Ma ago, and ended in the mid-Miocene. There followed a very extended period of quiescence, then very minor Quaternary post-erosional volcanism. The shield stage produced volcanoes up to 3000 m above sea level which were rapidly eroded by 17.5

C. j. Stillman

1999-01-01

96

Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico  

E-print Network

graded Miocene sands with interbedded laminites and mineralogical assemblages of plutonic and volcanic rock fragments from the cored depths of 800-900 meters below the sediment-water interface. This anomalous occurrence of coarse sand and rock... graded Miocene sands with interbedded laminites and mineralogical assemblages of plutonic and volcanic rock fragments from the cored depths of 800-900 meters below the sediment-water interface. This anomalous occurrence of coarse sand and rock...

Kuzela, Robert Christian

2012-06-07

97

Biomarkers challenge early Miocene loess and inferred Asian desertification  

NASA Astrophysics Data System (ADS)

Fine-grained Miocene sediments from Tianshui Basin, northeastern Tibetan Plateau, have received intense attention recently because these sediments were identified as loess. The presence of early Miocene loess pushes the timing of initiation of inland Asian desertification from 8 Ma back to 22 Ma. However, mudflat/distal fan and shallow lake sediments of Miocene have also been reported in Tianshui Basin. Consequently, the origin of these fine-grained Miocene sediments in this area remains controversial. Here we investigate the n-alkane biomarker characteristics of Neogene sediments from a north-south transect of exposures within Tianshui Basin and compare these molecular distributions with those published Quaternary loess to help resolve the disputed origin. We found that n-C23 and n-C25 alkanes, sourced from either aquatic macrophytes or palustrine plants, are ubiquitous in the Miocene sediments from Tianshui Basin but are largely absent in Quaternary loess. This striking difference between n-alkane distributions in the Tianshui samples and the Quaternary loess casts doubt on an eolian origin for the Tianshui samples and challenges the hypothesis of an early Miocene onset of Asian interior desertification.

Peng, Tingjiang; Li, Jijun; Song, Chunhui; Zhao, Zhijun; Zhang, Jun; Hui, Zhengchuang; King, John W.

2012-03-01

98

A molecular organic carbon isotope record of miocene climate changes  

SciTech Connect

The difference in carbon-13 ([sup 13]C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in [sup 18]O ([delta][sup 18]O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes ([delta][sup 13]C = 25.4 [+-] 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C[sub 35] hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing [sup 13]C concentrations in Middle and Late Miocene samples ([delta][sup 13]C = 29.5 to [minus]31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone.

Schoell, M. (Chevron Petroleum Technology Co., La Habra, CA (United States)); Schouten, S.; Sinninghe Damste', J.S.; Leeuw, J.W. de (Netherlands Institute of Sea Research, Texel (Netherlands)); Summons, R.E. (Australian Geological Survey Organization, Canberra (Australia))

1994-02-25

99

Miocene sequence biostratigraphy of the northern Gulf of Mexico  

SciTech Connect

The Miocene floral pulse model of Jiang and Watkins is revised. The new revision suggests that the Gulf of Mexico Miocene floral pulses, corresponding to the traditional foraminiferal tops, are transgression surfaces of the fourth-order sequences. These pulses show diverse magnitudes and when they are plotted on a depth (or time) tract, their relative magnitudes show an orderly wavy pattern comparable to the Haq et al.'s third-order cycles in the Miocene. After iterative comparison, the condensed intervals of these Miocene third-order sequences have been determined as, in descending order, Cyclammina 3, the second Cibicides carstensi, the second Textularia W, Cristellaria I, Robulus 43, Discorbis B, the third Marginulina A, and Textularia panamensis (= fauna unit II). The least prominent pulses suggesting the third-order cycle highstands (or shelf-margin wedges) are suggested as, in descending order, Textularia X, Bolivina thalmanni, Globorotalia fohsi robusta, Bigenerina humblei, Cibicides opima, Saracenaria schencki, Marginulina A (= second Robulus chambersi), and Siphonina davisi. Redeposited Cretaceous nanno species are an important component in the Gulf of Mexico middle and lower Miocene. Significant concentrations of these species are found primarily in the third-order cycle highstands, one exception being the Marginulina A third-order cycle highstand that in the High Island and West Cameron areas contained only rare redeposited Cretaceous nannos.

Jiang, M.M. (ARCO Oil and Gas Company, Houston, TX (United States))

1993-09-01

100

Long-period orbital control on middle Miocene global cooling: Integrated stratigraphy and astronomical tuning  

E-print Network

Long-period orbital control on middle Miocene global cooling: Integrated stratigraphy in the middle Miocene global cooling (13.82 Ma ± 0.03) coincides with minimum eccentricity values associated with the major step in middle Miocene global cooling and provides a level suitable for placing the physical

Utrecht, Universiteit

101

Stratigraphical and palaeontological characteristics of the Miocene deposits at Soluq area, NE Libya: First Results  

NASA Astrophysics Data System (ADS)

The north-south scarp that runs in the middle of Soluq area, about 70 km southeast of Benghazi, attains altitudes towards the north, reaching a maximum of about 300 meters above sea level at wadi al Qattarah. The scarp fades gradually towards the south till at Antelat area and is represented by few meters high hills. The plateau, however, extends eastwards rising to altitudes more than 450 meters above sea level. The plain (known as Soluq plain) extends westwards till near the Mediterranean coast with average width of about 50 kilometers. Several outcrops along the main escarpment have been visited and spot sampled and two carbonate rock units separated by reduced deposits of clastic origin have been recognised based on lithology and faunal contents. The oldest rock unit is representing by the Benghazi Formation and the youngest rock unit is representing by Wadi al Qattarah Formation. Both rock units, nevertheless, are belonging to the Miocene Ar Rajmah Group and cover the greater part of the Soluq area. The lower Benghazi Formation has been dated as Middle Miocene based on the presence of Lepidocyclina (Eulepidina) dilatat (Michelotti) and Borelis melo melo (Fichiteli). The latter taxon was recognized in different local areas of the same time-interval. The inconsistent occurrences and broken nature of tests of Borelis melo melo in some levels in the upper Wadi al Qattarah Formation, however, indicates that this taxon has been subjected to extensive reworking and Late Miocene age is ascribed to the major deposits of the later rock unit. This assumption may explain the occurrences of a number of lenses and irregular bodies of gypsum of the Messenian event in study region. The high variety of the microfacies and fossil assemblages recognised in this study reflects (1) the variety of environmental settings and (2) the effect of the lithofacies on the fossil recovery. In general, larger and small foraminifera from the Miocene Ar Rajmah Group are a mix of infaunal and epifaunal taxa in which a prevalence of free, larger epifaunal types has been recorded. The depositional history of the studied sequence, however, has been interpreted in terms of Wilson standard carbonate facies belts and indicate an overall shallowing upward trend, from open platform (Benghazi Formation) to restricted platform and restricted lagoon-saline conditions (Wadi al Qattarah Formation).

Abdulsamad, E. O.; El Zanati, S. M.

2012-04-01

102

Ptychoptera deleta Novák, 1877 from the Early Miocene of the Czech Republic: redescription of the first fossil attributed to Ptychopteridae (Diptera)  

PubMed Central

Abstract The first fossil that was described in Ptychopteridae, Ptychoptera deletaNovák, 1877 from the classical Early Miocene locality Mok?ina (Krottensee) in western Bohemia is re-examined. The re-description of the holotype including a new line drawing and remarks summarizing the scarce fossil record of this group is provided. PMID:22259284

Krzemi?ski, Wieslaw; Prokop, Jakub

2011-01-01

103

Middle Miocene paleoclimate change at Bryce Burn, southern New Zealand  

Microsoft Academic Search

New Zealand's isolated position in the Southwest Pacific and the quality of its marine and terrestrial sedimentary record make it a valuable source of information for studies of global climate change. A section at Bryce Burn in Southland, South Island, provides a record of middle Miocene global cooling associated with buildup of an extensive semi?permanent ice sheet on Antarctica. The

B. D. Field; M. P. Crundwell; G. L. Lyon; D. C. Mildenhall; H. E. G. Morgans; C. Ohneiser; G. S. Wilson; J. P. Kennett; F. Chanier

2009-01-01

104

Tectonic implications of early Miocene volcanic rocks, San Joaquin basin  

Microsoft Academic Search

The early Miocene (22 Ma) Tecuya volcanic rocks of the San Emigdio Mountains were erupted during a regional episode of crustal extension in coastal California. These rocks are correlative with similar rocks in outcrops and the subsurface over at least 800 kmz in the southern San Joaquin basin. Initial dacitic eruptions produced laterally continuous subaerial to submarine pyroclastic flows. These

R. B. Cole; P. G. Decelles

1990-01-01

105

Shallow and deep rotations in the Miocene Alps  

Microsoft Academic Search

Mapping and the construction of balanced cross-sections reveal dextral rotation in addition to N-S contraction during the late middle to late Miocene Jura phase both at the northern and the southern front of the Central Alps (Jura and Lombardic Southern Alps, respectively). These rotations may be ascribed to one and the same shallow domain or sublid, rotated clockwise around a

H. Laubscher

1996-01-01

106

Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America  

PubMed Central

Four groups of equids, “Anchitheriinae,” Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate. PMID:24587267

Famoso, Nicholas A.; Davis, Edward Byrd

2014-01-01

107

Paleomagnetic Evidence for Spatially Distributed Post-Miocene Rotation of Western Washington and Oregon  

NASA Astrophysics Data System (ADS)

Anomalous paleomagnetic directions have been determined for 17 sites in the Frenchmans Springs member of the Wanapum basalt formation, Columbia River basalt group. These sites are located in the Ginkgo flows from near Vantage, Washington, to Portland, Oregon, a distance of approximately 300 km. The average paleomagnetic direction for six of these sites, centered around Vantage is D = 147°, I = 41°, ?95 = 4.5°. The expected Miocene field direction is D = 355°, I = 65°. At some localities there are two distinct Ginkgo flows, in direct stratigraphic succession, with statistically identical anomalous directions. Their anomalous paleomagnetic direction makes these flows a valuable marker horizon in the Columbia River basalt group. The nondipole field direction of the Ginkgo flows correlates well with available results from the Miocene Cape Foulweather basalts of Oregon. This correlation strongly supports the hypothesis that these coastal basalts of Oregon are the distal ends of Columbia Plateau derived basalt flows. The spatial distribution of these anomalous field directions suggests about 14° of clockwise rotation between Vantage and Portland. Combining these data with data from the Oregon Coast basalts allows a maximum declination difference of about 35°. The increase in declination can be best explained by clockwise rotation, about nearby vertical axes, increasing to the southwest across the Columbia Plateau and Oregon coast.

Sheriff, Steven D.

1984-06-01

108

Did tectonic activity stimulate oligo-miocene speciation in the Indo-West Pacific?  

PubMed

Analyses of molecular phylogenies of three unrelated tropical marine gastropod genera, Turbo, Echinolittorina, and Conus, reveal an increase in the rate of cladogenesis of some Indo-West Pacific (IWP) clades beginning in the Late Oligocene or Early Miocene between 23.7 and 21.0 million years ago. In all three genera, clades with an increased rate of diversification reach a maximum of diversity, in terms of species richness, in the central IWP. Congruence in both the geographical location and the narrow interval of timing suggests a common cause. The collision of the Australia and New Guinea plate with the southeast extremity of the Eurasian plate approximately 25 Mya resulted in geological changes to the central IWP, including an increase in shallow-water areas and length of coastline, and the creation of a mosaic of distinct habitats. This was followed by a period of rapid diversification of zooxanthellate corals between 20 and 25 Mya. The findings reported here provide the first molecular evidence from multiple groups that part of the present-day diversity of shallow-water gastropods in the IWP arose from a rapid pulse of speciation when new habitats became available in the Late Oligocene to Early Miocene. After the new habitats were filled, the rate of speciation likely decreased and this combined with high levels of extinction (in some groups), resulted in a slow down in the rate of diversification in the genera examined. PMID:18410535

Williams, Suzanne T; Duda, Thomas F

2008-07-01

109

Provenance study conflict Miocene eolian deposit in central China  

NASA Astrophysics Data System (ADS)

The dispute of fine-grained Miocene sediments from Tianshui Basin, northeastern Tibetan Plateau as eolian loess-paleosol or neptunian mudflat/distal fan is an unresolved hot topic in Cenozoic palaeoclimatology , impacting further research of Asian monsoon and the mechanism of its variations. Tratigraphic correlation and constraining the sedimentary age with paleomagnetic method show that hundreds miles of foreland basin stratums occurred in north of West Qinling mountain belt in Miocene. The tratums are about 2000 m thick in the south foredeep range, thinning to less than 300 m thick in the north backbulge range. Similar heavy minerals composition and detrital ziron U/Pb ages distribution also show that the materials in the basin were from the same denuded regions. Such evidences conform that the Miocene sedimentary sections identified as loess in Tianshui basin could be distal fan and flood plain in the united foreland basin system. Comprehensive provenance techniques of heavy minerals and detrital zircon U/Pb ages show differences between Miocene Tianshui sediments and Pliocene- Quaternary loess- red clay from Chinese loess Plateau. Specifically, samples from Tianshui basin have more than 20% of Magnetite and 30% of Epidote, but Amphibole is lacking. Loess-red clay samples consist of 21% Amphibole on average. Classifying degree of correction of Amphibole proves that weathering erosion is not the reason for this dissimilarity. More Amphibole rich iginous rocks or matemorphoic rocks could exist widely in loess's source region. Most zircon U/Pb ages in this study fall into similar ranges, especially from 200Ma to 500Ma. There is a significant age peak from 200Ma to 250Ma in Tianshui sediments and modern river sands originating from West Qinling mountain belt, which is rare in loess-red clay samples. A part of zircons from loess and red clay contain very low U and Th elements, implying some of Mafic or intermediate rocks in eolian source area. Both Mafic and intermediate rocks can be found in north of Tibetan Plateau, the recommended initial source area of Quaternary loess. West Qinling mountain belt is composed mainly of Mesozoic sedimentary rocks and granite, which can only provide materials absent of amphiboles and some local peaks of zircon U/Pb ages. They have been confirmed in Tianshui Miocene samples. We propose that the materials from recommended source areas of Pliocene- Quaternary loess-red clay did not join in the Tianshui basin in Miocene. This conclusion may also challenge previous viewpoints that Asian monsoon can be dated back to early Miocene.

Liu, S.; Stockli, D. F.; Li, J.; Song, C.

2013-12-01

110

C4 expansion in the central Inner Mongolia during the latest Miocene and early Pliocene  

NASA Astrophysics Data System (ADS)

The emergence of C4 photosynthesis in plants as a significant component of terrestrial ecosystems is thought to be an adaptive response to changes in atmospheric CO 2 concentration and/or climate during Neogene times and has had a profound effect on the global terrestrial biosphere. Although expansion of C4 grasses in the latest Miocene and Pliocene has been widely documented around the world, the spatial and temporal variations in the C4 expansion are still not well understood and its driving mechanisms remain a contentious issue. Here we present the results of carbon and oxygen isotope analyses of fossil and modern mammalian tooth enamel samples from the central Inner Mongolia. Our samples represent a diverse group of herbivorous mammals including deer, elephants, rhinos, horses and giraffes, ranging in age from the late Oligocene to modern. The ?13C values of 91 tooth enamel samples of early late-Miocene age or older, with the exception of two 13 Ma rhino samples (- 7.8 and - 7.6‰) and one 8.5 Ma suspected rhino sample (- 7.6‰), were all less than - 8.0‰ (VPDB), indicating that there were no C4 grasses present in their diets and thus probably few or no C4 grasses in the ecosystems of the central Inner Mongolia prior to ~ 8 Ma. However, 12 out of 26 tooth enamel samples of younger ages (~ 7.5 Ma to ~ 3.9 Ma) have ?13C values higher than - 8.0‰ (up to - 2.4‰), indicating that herbivores in the area had variable diets ranging from pure C3 to mixed C3-C4 vegetation during that time interval. The presence of C4 grasses in herbivores' diets (up to ~ 76% C4) suggests that C4 grasses were a significant component of the local ecosystems in the latest Miocene and early Pliocene, consistent with the hypothesis of a global factor as the driving mechanism of the late Miocene C4 expansion. Today, C3 grasses dominate grasslands in the central Inner Mongolia area. The retreat of C4 grasses from this area after the early Pliocene may have been driven by regional climate change associated with tectonic processes in central Asia as well as global climate change.

Zhang, Chunfu; Wang, Yang; Deng, Tao; Wang, Xiaoming; Biasatti, Dana; Xu, Yingfeng; Li, Qiang

2009-10-01

111

First Hominoid from the Late Miocene of the Irrawaddy Formation (Myanmar)  

PubMed Central

For over a century, a Neogene fossil mammal fauna has been known in the Irrawaddy Formation in central Myanmar. Unfortunately, the lack of accurately located fossiliferous sites and the absence of hominoid fossils have impeded paleontological studies. Here we describe the first hominoid found in Myanmar together with a Hipparion (s.l.) associated mammal fauna from Irrawaddy Formation deposits dated between 10.4 and 8.8 Ma by biochronology and magnetostratigraphy. This hominoid documents a new species of Khoratpithecus, increasing thereby the Miocene diversity of southern Asian hominoids. The composition of the associated fauna as well as stable isotope data on Hipparion (s.l.) indicate that it inhabited an evergreen forest in a C3-plant environment. Our results enlighten that late Miocene hominoids were more regionally diversified than other large mammals, pointing towards regionally-bounded evolution of the representatives of this group in Southeast Asia. The Irrawaddy Formation, with its extensive outcrops and long temporal range, has a great potential for improving our knowledge of hominoid evolution in Asia. PMID:21533131

Jaeger, Jean-Jacques; Naing Soe, Aung; Chavasseau, Olivier; Coster, Pauline; Emonet, Edouard-Georges; Guy, Franck; Lebrun, Renaud; Maung, Aye; Aung Khyaw, Aung; Shwe, Hla; Thura Tun, Soe; Linn Oo, Kyaw; Rugbumrung, Mana; Bocherens, Herve; Benammi, Mouloud; Chaivanich, Kamol; Tafforeau, Paul; Chaimanee, Yaowalak

2011-01-01

112

A study of uranium favorability of Cenozoic sedimentary rocks, Basin and Range Province, Arizona: Part I, General geology and chronology of pre-late Miocene Cenozoic sedimentary rocks  

USGS Publications Warehouse

This study focuses attention on Cenozoic sedimentary rocks in the Basin and Range Province of Arizona. The known occurrences of uranium and anomalous radioactivity in these rocks are associated with sediments that accumulated in a low energy environment characterized by fine-grained clastics, including important tuffaceous materials, and carbonate rocks. Most uranium occurrences, in these rocks appear to be stratabound. Emphasis was placed on those sedimentary materials that pre-date the late Cenozoic Basin and Range disturbance. They are deformed and crop out on pedimented range blocks and along the province interface with the Transition Zone. Three tentative age groups are recognized: Group I - Oligocene, pre-22 m.y., Group II - early Miocene - 22 m.y. - 16 m.y., and Group III - middle Miocene - 16 m.y. to 13--10 m.y. Regionally, these three groups contain both coarse to fine-grained red clastics and low energy lighter colored 'lacustrine' phases. Each of the three groups has been the object of uranium exploration. Group II, the early Miocene strata, embraces the Anderson Mine - Artillery region host rocks and also the New River - Cave Creek early Miocene beds-along the boundary with the Transition Zone. These three groups of rocks have been tectonically deformed to the extent that original basins of deposition cannot yet be reconstructed. However, they were considerably more extensive in size than the late Cenozoic basins the origin of which deformed the former. Group II rocks are judged to be of prime interest because of: (1) the development and preservation of organic matter in varying lithologies, (2) apparent contemporaneity with silicic volcanic centers, (3) influence of Precambrian crystalline rocks, and (4) relative outcrop continuity near the stable Transition Zone. The Transition Zone, especially along its boundary with the Basin and Range Province, needs additional geologic investigation, especially as regards the depositional continuity of Group II sediment s.

Scarborough, Robert Bryan; Wilt, Jan Carol

1979-01-01

113

Upper Miocene reef complex of Mallorca, Balearic Islands, Spain  

SciTech Connect

The late Tortonian-Messinian coral reef platform of south Mallorca onlaps a folded middle late Miocene carbonate platform on which progradation of up to 20 km occurs. Vertical sea cliffs (up to 100 m high) superbly show the last 5 km of this progradation and complement the numerous water-well cores from the island interior. The Mallorca reef presents the most complete facies zonation of the Miocene reefs of the western Mediterranean. The reef wall framework is up to 20 m thick and shows (1) erosional reef flat with reef breccia and small corals; (2) spur-and-grove zone with large, massive corals; (3) deep buttresses and pinnacles with terraces of branching corals; and (4) deep reef wall with flat, laminar coral colonies, branching red algae, and Halimeda sands.

Pomar, L.

1988-02-01

114

Giant Miocene landslides and the evolution of Fuerteventura, Canary Islands  

NASA Astrophysics Data System (ADS)

Fuerteventura is the oldest island in the Canaries archipelago; following the growth of a pre-Miocene seamount, its shield stage began 20.6 Ma ago, and ended in the mid-Miocene. There followed a very extended period of quiescence, then very minor Quaternary post-erosional volcanism. The shield stage produced volcanoes up to 3000 m above sea level which were rapidly eroded by 17.5 Ma. Both Fuerteventura and Lanzarote, the older eastern-most islands, are in a post-erosional stage and have subdued topography with elevations rarely rising above 400 m. The western islands, La Palma and El Hierro, together with Tenerife, are the youngest in the archipelago, and are still in their shield stage which began at most 7.5 Ma ago. They have a rugged topography with peaks rising to several thousand metres. Volcanic activity persists in these islands and in Lanzarote. The shield-stage construction of the volcanically active western islands demonstrates that recent eruptive activity has concentrated in volcanic centres aligned in well-defined rift zones in which major dyke emplacement has taken place, and that volcano flank collapse has occurred with giant landslides initiated on the rifts. In Fuerteventura, most of the shield-stage volcanic rocks have been removed; however, evidence has now been advanced to show that major dyke swarms were emplaced in the Oligocene and Miocene. These belonged to a line of intrusive complexes above which, by the early to mid-Miocene, volcanic peaks had been constructed. Three volcanic centres have been identified and in the central one, a peak as high as the present Mount Teide on Tenerife was rapidly denuded in less than 2 Ma. In the west of the island, this erosion has exposed a window of more than 300 km 2 of submarine volcanics and sediments belonging to the pre-shield phase seamount. The principal mechanism of erosion seems to have been the generation of giant landslides analogous to those seen in the younger islands. These appear to have removed some 3500 km 3 of lavas and volcaniclastics, stripping the western sectors of the Miocene volcanoes down to the pre-shield phase "Basal Complex", and transporting the mass of volcanic material into the Atlantic ocean as debris flows. Remnants of the shield volcanoes still exist in the eastern part of the island. Present day topographic variation indicates that the Miocene base level of erosion is still visible in a "Central Depression" which runs through the axis of the island, the eastern hills are composed of the Miocene shield-stage volcanics which still preserve a drainage pattern initiated on these peaks, and the "Basal Complex" in the west has a juvenile landscape suggesting incision on a post-Miocene domal uplift of the volcano core. Structural links between intra-island volcano-tectonic events and the South Atlas Fault zone are not thought to be likely.

Stillman, C. J.

1999-12-01

115

Oligocene–early Miocene Antarctic nearshore diatom biostratigraphy  

Microsoft Academic Search

Lower Oligocene (ca. 31Ma) to lower Miocene (ca. 18.5Ma) biosiliceous microfossils recovered from the Cape Roberts Project (CRP-2\\/2A) drill cores provide both paleoenvironmental and biostratigraphic information, enhancing our understanding of the geological history of the Victoria Land Basin, Antarctica. The biochronostratigraphic record obtained provides key data with which time–space–facies models may be developed. Assemblages of neritic and pelagic microfossils such

Matthew P. Olney; Reed P. Scherer; David M. Harwood; Steven M. Bohaty

2007-01-01

116

Across the Pacific: Climate Evolution in the Middle Miocene  

NASA Astrophysics Data System (ADS)

We present the first high-resolution (3 kyr) astronomically-tuned record of ?18O and ?13C from planktonic foraminifera for the equatorial Pacific Ocean (16.5-13.5 Myr). Our data provides exciting new information on sea surface temperatures and primary productivity changes at the tropics during the middle Miocene at a resolution not achieved in any previous study, which sheds new light on the middle Miocene climatic transition (MMCT) and associated carbon-isotope excursion. Reliable sea surface temperature estimates are crucial to any reconstruction and modelling of past ocean salinity and density, water column stratification, thermohaline circulation, and ice volume. Despite extensive studies of benthic foraminifera, existing planktonic foraminiferal records of this interval are extremely scarce and of low resolution, with samples representing time intervals of 2x105and 5x105 years. Previous studies have been hindered by the absence of biogenic carbonate (e.g., Leg 199). Consequently the impact of global warming and cooling on tropical surface waters and the propagation of orbital cycles in the Earth System are unknown. In 2009 Integrated Ocean Drilling Program Expedition 320/321 recovered lower-middle Miocene sediments with high sedimentation rates (30m/myr), continuous recovery, and orbital cyclicity from the east equatorial Pacific Ocean. At Site U1338 planktonic foraminifera are abundant and diverse in the lower and middle Miocene sediments and exceptionally well preserved. Scanning electron microscope studies revealed open pore spaces, little evidence of calcitic overgrowth on the wall surface and in many cases preserved spines (Fox and Wade, 2013). We compare our data from Site U1338 to Site 1146 in the western equatorial Pacific Ocean, to reconstruct bottom and surface water conditions and changes in ocean dynamics across the equatorial Pacific during this highly complex interval of climate history.

Fox, Lyndsey; Wade, Bridget; Holbourn, Ann; Leng, Melanie

2014-05-01

117

Across the Pacific: Climate Evolution in the Middle Miocene  

NASA Astrophysics Data System (ADS)

We present the first high-resolution (3 kyr) astronomically-tuned record of ?18O and ?13C from planktonic foraminifera for the equatorial Pacific Ocean (16.5-13.5 Myr). Our data provides exciting new information on sea surface temperatures and primary productivity changes at the tropics during the middle Miocene at a resolution not achieved in any previous study, which sheds new light on the middle Miocene climatic transition (MMCT) and associated carbon-isotope excursion. Reliable sea surface temperature estimates are crucial to any reconstruction and modelling of past ocean salinity and density, water column stratification, thermohaline circulation, and ice volume. Despite extensive studies of benthic foraminifera, existing planktonic foraminiferal records of this interval are extremely scarce and of low resolution, with samples representing time intervals of 2x105 and 5x105 years. Previous studies have been hindered by the absence of biogenic carbonate (e.g., Leg 199). Consequently the impact of global warming and cooling on tropical surface waters and the propagation of orbital cycles in the Earth System are unknown. In 2009 Integrated Ocean Drilling Program Expedition 320/321 recovered lower-middle Miocene sediments with high sedimentation rates (30m/myr), continuous recovery, and orbital cyclicity from the east equatorial Pacific Ocean. At Site U1338 planktonic foraminifera are abundant and diverse in the lower and middle Miocene sediments and exceptionally well preserved. Scanning electron microscope studies revealed open pore spaces, little evidence of calcitic overgrowth on the wall surface and in many cases preserved spines (Fox and Wade, in press). We compare our data from Site U1338 to Site 1146 in the western equatorial Pacific Ocean, to reconstruct bottom and surface water conditions and changes in ocean dynamics across the equatorial Pacific during this highly complex interval of climate history.

Fox, L. R.; Wade, B.; Holbourn, A. E.; Leng, M. J.

2013-12-01

118

North Atlantic Deep Water formed by the later middle Miocene  

Microsoft Academic Search

There is evidence that in Mesozoic and Palaeogene times both north and south subpolar areas had a mild climate1,2. Unlike the present day climatic symmetry, with warm equatorial regions and ice-covered polar regions, a strong planetary asymmetry developed in the middle Miocene, when the Antarctic ice cap was established while the northern high latitudes remained unglaciated3. The symmetry was restored

P.-L. Blanc; D. Rabussier; C. Vergnaud-Grazzini; J.-C. Duplessy

1980-01-01

119

Preservation of Miocene glacier ice in East Antarctica  

Microsoft Academic Search

ANTARCTIC climate during the Pliocene has been the subject of considerable debate. One view holds that, during part of the Pliocene, East Antarctica was largely free of glacier ice and that vegetation survived on the coastal mountains1á¤-4. An alternative viewpoint argues for the development of a stable polar ice sheet by the middle Miocene, which has persisted since then5á¤-10. Here

David E. Sugden; David R. Marchant; Noel Potter; Roland A. Souchez; George H. Denton; Carl C. Swisher III; Jean-Louis Tison

1995-01-01

120

Human evolution from the Miocene to the Present  

Microsoft Academic Search

Based on morphological, palaeoanthropological and molecular biological studies, human evolution from the Miocene to the Present\\u000a has been reviewed. The initial divergence of orangutan from the hominoid stock, the divergence of man from the last common\\u000a ancestor with the African apes, the origin and expansion ofHomo lineage and the advent of modern man have been discussed.

Shama Barnabas

1990-01-01

121

Effects on growth and cost of production of Arizona ash, Indian hawthorn, Southern waxmyrtle, and live oak sequentially produced in combinations of Cu-treated and non-treated 0.24 L., 2.7 L and 10.4 L or 12.7 L containers  

E-print Network

velutina Torr. (Arizona ash), Quercus virginians Mill. (live oak), and Rapheolepis indica Lindl. (lndian hawthorn) and two-hundred forty seedlings of Myrica cerebra L. (waxmyrtle) were grown in College Station, Texas in 0.24 L containers half...

Obst, Steven Paul

2012-06-07

122

Early Miocene anatexis identified in the western syntaxis, Pakistan Himalaya  

NASA Astrophysics Data System (ADS)

Evidence for typical Himalayan Early to Middle Miocene anatexis has remained elusive in the Nanga Parbat massif in the western Himalaya of Pakistan; previous work has identified only young plutonism (10-1 Ma). New U-(Th)-Pb data from the Southern Chichi granite, a leucogranite in southern Nanga Parbat, reveal that crustal melting occurred during the Early Miocene. This largely undeformed, fine-grained pluton intrudes the Indian metasedimentary cover sequence adjacent to the Rupal shear, a major shear zone at Nanga Parbat. Th-Pb ion microprobe analyses of monazites from the Chichi granite yield ages between 22 Ma and 16 Ma, with the majority of analyses lying at 19-18 Ma. U/Pb zircon analyses yield ages which fall along a chord with a lower intercept age of 19 Ma. The zircons also contain an ˜1850 Ma inherited component. These data indicate that the Early Miocene anatexis that is ubiquitous in central portions of the Himalayan orogen, unreported anywhere in the NW Himalaya, also occurred in the western Himalayan syntaxis, and demonstrates that Nanga Parbat has a protracted melting history. A small granitic dike that cross-cuts the outer portion of the Rupal shear yields monazite ages between 22 Ma and 9 Ma, where the young ages correlate with high U concentrations. 40Ar- 39Ar biotite ages from adjacent gneisses indicate cooling by 10 Ma, requiring significant displacement on this portion of the Rupal shear to be older than ˜10 Ma and possibly as old as ˜20 Ma.

Schneider, D. A.; Edwards, M. A.; Kidd, W. S. F.; Zeitler, P. K.; Coath, C. D.

1999-04-01

123

Miocene detachment in Crete and exhumation PTt paths of high-pressure metamorphic rocks  

Microsoft Academic Search

A major problem posed by the geology of Crete is the horizontal contact of an upper unit without Miocene metamorphism onto a metamorphosed lower one with Early Miocene high pressure\\/low temperature (HP\\/LT) parageneses. This very sharp contact is roughly parallel to the major Oligo-Miocene thrust planes which were reactivated as a large-scale detachment which allowed exhumation of high-pressure units. We

L. Jolivet; B. Goffé; P. Monié; C. Truffert-Luxey; M. Patriat; M. Bonneau

1996-01-01

124

Transitional directions from Early Miocene Lavas at Samothraki Island, N. Greece  

NASA Astrophysics Data System (ADS)

The North Hellenic orogen was formed at the expenses of the Variscan and Jurassic oceanic crust, preserved in scattered ophiolitic massifs. Strong post-orogenic extension with coeval emplacement of granodioritic plutons, deposition of clastic sediments and calc-alkaline volcanism appeared from the Middle-Late Eocene to the Middle Miocene. These widespread Tertiary volcanic products, outcropping also in north and central Aegean, have been extensively studied as far as their emplacement conditions are concerned. In parallel, they have been the object of several palaeomagnetic studies, all consistently indicating a general pattern of clockwise rotations. The island of Samothraki belongs to the Circum-Rhodope Zone, a series of Triassic-Jurassic continental margin sedimentary and volcanic rocks that surround the crystalline Serbo-Macedonian and Rhodope Massifs. The geochronological data, along with the morphology and the eruption mode of the Samothraki Tertiary volcanic rocks, allow a division into three groups, namely the "old", the "intermediate" and the "young" ones. Several radiometric ages have been assigned to the three groups, spanning from 25 to 19 Ma. Isotope and trace-element modeling do not favor a continuous evolution of these magmas. The major granitic and volcanic formations of the island have been subjected to paleomagnetic studies. The results revealed a complex pattern with coexisting straightforward directions and puzzling ones, only within the younger lavas, mostly domes. These samples are characterized by a medium temperature component with an eastward declination and a positive inclination and a high temperature one with a negative inclination. Experiments of absolute paleointensity have been conducted on twenty-eight samples from 3 separate domes with ages between 22-19 Ma using a modified Thellier technique with very narrow 4°C to 10°C temperature steps between 500°C and 595°C. The results indicate significantly low field values at two sites. The presence of low paleointensities combined with intermediate directions suggest that they recorded a transitional field state. Interestingly, similar directions were obtained in miocene volcanics from the nearby island of Lemnos as well as from the mainland Thrace area. A further study of these formations will hopefully improve our knowledge of the field behavior in Early Miocene.

Kondopoulou, Despina; Valet, Jean-Pierre; Zananiri, Irene; Voidomatis, Philippos

2014-05-01

125

The genus Macroteleia Westwood in Middle Miocene amber from Peru (Hymenoptera, Platygastridae s.l., Scelioninae).  

PubMed

A new species of the scelionine genus Macroteleia Westwood (Platygastridae s.l., Scelioninae) is described and figured from a female beautifully preserved in Middle Miocene amber from Peru. Macroteleia yaguarum Perrichot & Engel, sp. n., shows a unique combination of characters otherwise seen independently within its congeners. It is most similar to the modern M. surfacei Brues, but differs from it by the non-foveolate notauli, the contiguous punctures of the vertex, and the continuous propodeum. The new species is the first New World fossil of the genus, suggesting a Cretaceous origin for the group and a relatively old age of the South American, tropical African, and Australian faunas, and a younger age of the modern Holarctic faunas. PMID:25147461

Perrichot, Vincent; Antoine, Pierre-Olivier; Salas-Gismondi, Rodolfo; Flynn, John J; Engel, Michael S

2014-01-01

126

The genus Macroteleia Westwood in Middle Miocene amber from Peru (Hymenoptera, Platygastridae s.l., Scelioninae)  

PubMed Central

Abstract A new species of the scelionine genus Macroteleia Westwood (Platygastridae s.l., Scelioninae) is described and figured from a female beautifully preserved in Middle Miocene amber from Peru. Macroteleia yaguarum Perrichot & Engel, sp. n., shows a unique combination of characters otherwise seen independently within its congeners. It is most similar to the modern M. surfacei Brues, but differs from it by the non-foveolate notauli, the contiguous punctures of the vertex, and the continuous propodeum. The new species is the first New World fossil of the genus, suggesting a Cretaceous origin for the group and a relatively old age of the South American, tropical African, and Australian faunas, and a younger age of the modern Holarctic faunas. PMID:25147461

Perrichot, Vincent; Antoine, Pierre-Olivier; Salas-Gismondi, Rodolfo; Flynn, John J.; Engel, Michael S.

2014-01-01

127

Astronomical tuning of the La Vedova High Cliff section (Ancona, Italy)--Implications of the Middle Miocene Climate Transition for Mediterranean sapropel formation  

E-print Network

: Middle Miocene Mediterranean astronomical tuning paleomagnetism biostratigraphy environmental changes orbital forcing sapropels Continuous marine successions covering the Middle Miocene Climate Transition, which reflects the rapid expansion of the East Antarctic Ice Sheet in the middle Miocene. The onset

Utrecht, Universiteit

128

Life-History Traits of the Miocene Hipparion concudense (Spain) Inferred from Bone Histological Structure  

PubMed Central

Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentidueña (Segovia, Spain) has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentidueña together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain). The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens’ age within groups enabled us to characterize the age structure of both samples, which is typical of attritional assemblages. PMID:25098950

Martinez-Maza, Cayetana; Alberdi, Maria Teresa; Nieto-Diaz, Manuel; Prado, Jose Luis

2014-01-01

129

Miocene Vetigastropoda and Neritimorpha (Mollusca, Gastropoda) of central Chile  

NASA Astrophysics Data System (ADS)

Species of Vetigastropoda (Fissurellidae, Turbinidae, Trochidae) and one species of Neritimorpha (Neritidae) from the Navidad area, south of Valpara?´so, and the Arauco Peninsula, south of Concepción, are described. Among these, the Fissurellidae comprise Diodora fragilis n. sp., Diodora pupuyana n. sp., two additional unnamed species of Diodora, and a species resembling Fissurellidea. Turbinidae are represented by Cantrainea sp., and Trochidae include Tegula (Chlorostoma) austropacifica n. sp., Tegula (Chlorostoma) chilena n. sp., Tegula (Chlorostoma) matanzensis n. sp., Tegula (Agathistoma) antiqua n. sp., Bathybembix mcleani n. sp., Gibbula poeppigii [Philippi, 1887] n. comb., Diloma miocenica n. sp., Fagnastesia venefica [Philippi, 1887] n. gen. n. comb., Fagnastesia matanzana n. gen. n. sp., Calliostoma mapucherum n. sp., Calliostoma kleppi n. sp., Calliostoma covacevichi n. sp., Astele laevis [Sowerby, 1846] n. comb., and Monilea riorapelensis n. sp. The Neritidae are represented by Nerita (Heminerita) chilensis [Philippi, 1887]. The new genus Fagnastesia is introduced to represent low-spired trochoideans with a sculpture of nodes below the suture, angulated whorls, and a wide umbilicus. This Miocene Chilean fauna includes genera that have lived at the coast and in shallow, relatively warm water or deeper, much cooler water. This composition therefore suggests that many of the Miocene formations along the central Chilean coast consist of displaced sediments. A comparison with different fossil and Recent faunas from around the Pacific and South America indicates that the vetigastropod and neritid fauna from the Miocene of Chile has only minor affinities with taxa living near New Zealand, Argentina, and the tropical eastern Pacific at that time.

Nielsen, Sven N.; Frassinetti, Daniel; Bandel, Klaus

2004-09-01

130

Early Miocene basin evolution in northern Hungary: Tectonics and eustasy  

NASA Astrophysics Data System (ADS)

It is presumed that the Oligocene-early Miocene basin evolution in northern Hungary was primarily driven by compressional tectonics, producing a major second-order transgressive-regressive faciès cycle. The early Miocene basin evolution is best understood in terms of "molasse" sedimentation in an overfilled flexural basin. During this time the gradual cessation of thrusting in the adjacent West Carpathian thrust-fold belt resulted in its uplift and subaerial exposure. Significant amounts of sediment were delivered to the flexural basin filling it up to sea level. During the late-stage uplift of the flexural basin a shallow-marine depositional environment developed, as a result of isostatic rebound, and signals of third-order eustatic sea-level changes can be revealed. Sedimentological studies of outcrops of the Lower Miocene succession proved marked changes in facies. Along the gently dipping distal (southeastern) flank of the basin a sudden inception of shallow-marine coarse elastics on top of siltstones, deposited in significantly deeper water, may have been the result of a third-order eustatic sea-level fall shortly before the Burdigalian (at the boundary of the NN1/NN2 nannofossil zones). During the resulting lowstand, various tide-dominated facies aggraded, which were subsequently flooded by the "Burdigalian sea-level rise". The highstand is represented by upwards shallowing progradational units due to accelerating sedimentation and/or tectonic uplift. The typically elongated and narrow flexural basin, characterized by small water depth, had dimensions which were particularly suitable for the amplification of tidal motions. This resulted in the deposition of tide-influenced sandy sediments. In contrast to examples where the evolution of a strong tidal influence is related to transgressions, here such conditions developed following a drop of sea level.

Sztanó, O.; Tari, G.

1993-11-01

131

Multiple Miocene Melastomataceae dispersal between Madagascar, Africa and India.  

PubMed Central

Melastomataceae sensu stricto (excluding Memecylaceae) comprise some 3000 species in the neotropics, 1000 in Asia, 240 in Africa, and 230 in Madagascar. Previous family-wide morphological and DNA analyses have shown that the Madagascan species belong to at least three unrelated lineages, which were hypothesized to have arrived by trans-oceanic dispersal. An alternative hypothesis posits that the ancestors of Madagascan, as well as Indian, Melastomataceae arrived from Africa in the Late Cretaceous. This study tests these hypotheses in a Bayesian framework, using three combined sequence datasets analysed under a relaxed clock and simultaneously calibrated with fossils, some not previously used. The new fossil calibration comes from a re-dated possibly Middle or Upper Eocene Brazilian fossil of Melastomeae. Tectonic events were also tentatively used as constraints because of concerns that some of the family's fossils are difficult to assign to nodes in the phylogeny. Regardless of how the data were calibrated, the estimated divergence times of Madagascan and Indian lineages were too young for Cretaceous explanations to hold. This was true even of the oldest ages within the 95% credibility interval around each estimate. Madagascar's Melastomeae appear to have arrived from Africa during the Miocene. Medinilla, with some 70 species in Madagascar and two in Africa, too, arrived during the Miocene, but from Asia. Gravesia, with 100 species in Madagascar and four in east and west Africa, also appears to date to the Miocene, but its monophyly has not been tested. The study afforded an opportunity to compare divergence time estimates obtained earlier with strict clocks and single calibrations, with estimates based on relaxed clocks and different multiple calibrations and taxon sampling. PMID:15519967

Renner, Susanne S

2004-01-01

132

The beaver Anchitheriomys from the Miocene of Central Europe  

SciTech Connect

New finds of teeth and mandibles of Anchitheriomys from the Hambach opencast lignite mine in Northwest Germany and the first detailed descriptions of other mandibles from South Germany and Switzerland allow a review of the Central European specimens of this rare beaver genus. The metric variation of cheek teeth and especially the great differences in dimensions of incisors can be much better assessed. The observed range in size can be attributed to ontogenetic changes, and all material is assigned to Anchitheriomys suevicus. Stratigraphically, this species is restricted to the early middle Miocene, European Mammalian Neogene biozones MN 5-6.

Stefen, C.; Mors, T. [Museum Tierkunde, Dresden (Germany)

2008-09-15

133

Miocene reef facies of pelagian block, central Mediterranean  

SciTech Connect

Miocene reefs outcrop in the Maltese Islands, southeastern Sicily, and the pelagian island of Lampedusa. Several rapid eustatic sea level fluctuations affected these late Tortonian-early Messinian build-ups; normal salinities appear to have been maintained during these events. In addition to sea floor topography, reef development appears to have been controlled by turbulence. Encruster-dominated patch reefs are typical of platform and shallow ramp situations where turbulence is high. Branching and massive coral assemblages are typical of fore-reef curtains and steep slope substrates.

Pedley, H.M.

1988-02-01

134

Natural product terpenoids in Eocene and Miocene conifer fossils.  

PubMed

Numerous saturated and aromatic hydrocarbons, but not polar compounds, originating from plants and microorganisms (biomarkers) have been reported in sediments, coals, and petroleum. Here we describe natural product terpenoids found in two fossil conifers, Taxodium balticum (Eocene) and Glyptostrobus oregonensis (Miocene). A similar terpenoid pattern is also observed in extant Taxodium distichum. The preservation of characteristic terpenoids (unaltered natural products) in the fossil conifers supports their systematic assignment to the Cypress family (Cupressaceae sensu lato). The results also show that fossil conifers can contain polar terpenoids, which are valuable markers for (paleo)chemosystematics and phylogeny. PMID:12202827

Otto, Angelika; White, James D; Simoneit, Bernd R T

2002-08-30

135

Ventilation of the Miocene Arctic Ocean: An idealized model study Bijoy Thompson,1  

E-print Network

Ventilation of the Miocene Arctic Ocean: An idealized model study Bijoy Thompson,1 Johan Nilsson,2 Ridge in the central Arctic Ocean, which suggests a transition from anoxic to oxic condition during indicate that the early Miocene Arctic Ocean became well ventilated when the Fram Strait reached a width

Nycander, Jonas

136

PRELIMINARY ASSESSMENT OF THE LATE MIOCENE AVIFAUNA FROM LEMUDONG'O, KENYA  

Microsoft Academic Search

The small collection of avian skeletal remains, including those of an eagle, an owl, and possibly a pheasant, from Lemudong'o provides additional information about terrestrial late Miocene avifaunas in east Africa. Large phasianids are known elsewhere in the Miocene of Africa, but pheasants are naturally absent today from the continent. The presence of two predatory bird species at the locality

THOMAS A. STIDHAM

137

Quantitative reconstruction of Miocene climate patterns and evolution in Southern China based on plant fossils  

Microsoft Academic Search

Southern China, especially Yunnan, has undergone high tectonic activity caused by the uplift of Himalayan Mountains during the Neogene, which led to a fast changing palaeogeography. Previous study shows that Southern China has been influenced by the Asian Monsoon since at least the Early Miocene. However, it is yet not well understood how intense the Miocene monsoon system was. In

Yi-Feng Yao; Angela A. Bruch; Volker Mosbrugger; Cheng-Sen Li

2011-01-01

138

Marine mammals from the Miocene of Panama Mark D. Uhen a,*, Anthony G. Coates b  

E-print Network

d Laboratory of Evolutionary Biology, Department of Anatomy, Howard University, WA 20059, USA a r marine fossils both invertebrate (mollusks, corals, microfossils etc.) and vertebrate (fish, land mammals vertebra from the late Miocene Tobabe Formation, a partial cetacean rib from the late Miocene Gatun

Bermingham, Eldredge

139

A Miocene tectonic inversion in the Ionian Sea (central Mediterranean): Evidence from  

E-print Network

of the fault pattern and a plate tectonic reorganization prior to the main phase of back-arc openingA Miocene tectonic inversion in the Ionian Sea (central Mediterranean): Evidence from multichannel (2011), A Miocene tectonic inversion in the Ionian Sea (central Mediterranean): Evidence from

Brest, Université de

140

Variations in Miocene phytoplankton growth rates in the southwest Atlantic: Evidence for changes in ocean circulation  

Microsoft Academic Search

Changes in ocean circulation are often credited as the primary control on large-scale climate change during the Miocene. This study investigates the latest Oligocene to middle Miocene evolution of Southern Ocean circulation by evaluating stable isotopic trends of shallow- and deep-dwelling planktonic foraminifera, as well as ?p records reconstructed from the carbon isotopic composition of diunsaturated alkenones in the southwestern

Mark Pagani; Michael A. Arthur; Katherine H. Freeman

2000-01-01

141

Early and Middle Miocene stable isotopes: Implications for Deepwater circulation and climate  

Microsoft Academic Search

The middle Miocene ?18O increase represents a fundamental change in the ocean-atmosphere system which, like late Pleistocene climates, may be related to deepwater circulation patterns. There has been some debate concerning the early to early middle Miocene deepwater circulation patterns. Specifically, recent discussions have focused on the relative roles of Northern Component Water (NCW) production and warm, saline deep water

James D. Wright; Kenneth G. Miller; Richard G. Fairbanks

1992-01-01

142

Application of (U-Th)/He thermochronometry as a geothermal exploration tool in extensional tectonic settings: the Wassuk Range, Hawthorne, Nevada  

E-print Network

at the latitude of Lake Tahoe. The entire range is characterized by several intact fault blocks composed of Mesozoic age plutonic rocks and Jurassic metavolcanics bounded to the east by high- angle normal faults (Dilles and Wright 1988; Dilles, 1992; Dilles... and Gans, 1995; Surpless, 1999). Mesozoic metavolcanics and plutonic rocks in the central Wassuk Range are nonconformably overlain by Oligocene to Miocene age silicic ash-flow tuffs (e.g., Mickey Pass and Singaste), andesite flows (e.g., Lincoln Flat...

Gorynski, Kyle; Stockli, Danny; Walker, J. Douglas; Sabin, Andrew

2010-01-01

143

Palaeoenvironmental Shifts Drove the Adaptive Radiation of a Noctuid Stemborer Tribe (Lepidoptera, Noctuidae, Apameini) in the Miocene  

PubMed Central

Between the late Oligocene and the early Miocene, climatic changes have shattered the faunal and floral communities and drove the apparition of new ecological niches. Grassland biomes began to supplant forestlands, thus favouring a large-scale ecosystem turnover. The independent adaptive radiations of several mammal lineages through the evolution of key innovations are classic examples of these changes. However, little is known concerning the evolutionary history of other herbivorous groups in relation with this modified environment. It is especially the case in phytophagous insect communities, which have been rarely studied in this context despite their ecological importance. Here, we investigate the phylogenetic and evolutionary patterns of grass-specialist moths from the species-rich tribe Apameini (Lepidoptera, Noctuidae). The molecular dating analyses carried out over the corresponding phylogenetic framework reveal an origin around 29 million years ago for the Apameini. Ancestral state reconstructions indicate (i) a potential Palaearctic origin of the tribe Apameini associated with a major dispersal event in Afrotropics for the subtribe Sesamiina; (ii) a recent colonization from Palaearctic of the New World and Oriental regions by several independent lineages; and (iii) an ancestral association of the tribe Apameini over grasses (Poaceae). Diversification analyses indicate that diversification rates have not remained constant during the evolution of the group, as underlined by a significant shift in diversification rates during the early Miocene. Interestingly, this age estimate is congruent with the development of grasslands at this time. Rather than clade ages, variations in diversification rates among genera better explain the current differences in species diversity. Our results underpin a potential adaptive radiation of these phytophagous moths with the family Poaceae in relation with the major environmental shifts that have occurred in the Miocene. PMID:22859979

Toussaint, Emmanuel F. A.; Condamine, Fabien L.; Kergoat, Gael J.; Capdevielle-Dulac, Claire; Barbut, Jerome; Silvain, Jean-Francois; Le Ru, Bruno P.

2012-01-01

144

Composition and provenance of the Puente Formation (Miocene), Los Angeles Basin  

SciTech Connect

The Puente Formation (PFm) is a middle to upper Miocene clastic unit lying unconformably on the middle to lower Miocene El Modeno Volcanics and Topanga Group, within the Los Angeles basin (LAB). The PFm, about 3900m thick, is composed of sandstone, conglomerate, and mudrock deposited on a submarine fan at bathyal depths. Several intrabasinal discordances suggest active tectonics during deposition. The succession consists of two main upward thickening and coarsening megacycles reflecting submarine fan progradation. The PFm is characterized up-section by: (1) thin-bedded fine sandstone and shale (La Vida M.) grading to thick-bedded coarse sandstone an conglomerate (soquel M.); (2) thin-bedded siltstone, mudrock and sandstone (Yorba M.) grading to thick- to very thick-bedded coarse-grained sandstone and conglomerate (Sycamore Canyon M.). Sandstones of the PFm are quartzofeldspathic and suggest a probable local provenance from the plutonic, volcanic, and metamorphic rocks of the San Gabriel Mountains. Petrological parameters, however, suggest variable contribution of these source rock units through time. Coarse-grained plutonic rock fragments are abundant for the entire succession and consist of plagioclase-rich plutonic rocks perhaps sourced from the Lowe granodiorite. Microlitic, lathwork to felsitic volcanic lithic grains are also present in the lower and middle part. In the Yorba M. there is a local increase of volcanic detritus (Lv/L - 0.80), represented by larger volcanic lithics and abundant volcaniclastic matrix. Metamorphic detritus is not very abundant; it is concentrated in the La Vida M. the PFm represents sedimentation during tectonically active time in the evolution of southern California.

Critelli, S. (Instituto de Rierca per la Protezione Idrogeologica Nell'Italia Meridionale ed Insulare, Roges de Rende (Italy)); Rumelhart, P.E.; Ingersoll, R.V. (Univ. of California, Los Angeles, CA (United States))

1994-04-01

145

Middle to late Miocene oxygen isotope stratigraphy of ODP site 1085 (SE Atlantic): new constrains on Miocene climate variability and sea-level fluctuations  

Microsoft Academic Search

The middle Miocene ?18O increase represents a fundamental change in earth's climate system due to a major expansion and permanent establishment of the East Antarctic Ice Sheet accompanied by some effect of deepwater cooling. The long-term cooling trend in the middle to late Miocene was superimposed by several punctuated periods of glaciations (Mi-Events) characterized by oxygen isotopic shifts that have

T. Westerhold; T. Bickert; U. Röhl

2005-01-01

146

Paleomagnetism of Miocene sediments from the Turfan Basin, Northwest China: no significant vertical-axis rotation during Neotectonic compression within the Tian Shan Range, Central Asia  

Microsoft Academic Search

Paleomagnetic results are reported from 377 samples of Miocene red sediments in the Turfan Basin of East Tian Shan, Northwest China. Thermal demagnetization for most specimens isolates a low-temperature component that groups around the present geomagnetic field. A high-temperature characteristic component is isolated from four localities and interpreted as primary remanent magnetization from apparent pre-folding origin and positive reversal test.

B. C. Huang; Y. C. Wang; T. Liu; T. S. Yang; Y. A. Li; D. J. Sun; R. X. Zhu

2004-01-01

147

A revision of the fossil genus Miocepphus and other Miocene Alcidae (Aves: Charadriiformes) of the Western North Atlantic Ocean  

Microsoft Academic Search

This study reviews and describes all known fossils of Alcidae from the Miocene of the western North Atlantic. Because the majority of alcid fossils recovered from Miocene sediments are allied with the genus Miocepphus Wetmore, 1940, the genus is revised here. Three new species of Miocepphus are described: Miocepphus bohaskai and Miocepphus blowi from the Early to Late Miocene, and

Erik Wijnker; Storrs L. Olson

2009-01-01

148

Millennial scale climatic responses through a Late Miocene precession cycle  

NASA Astrophysics Data System (ADS)

Late Miocene (11.61-5.33 Ma) climate is thought to have been warmer and wetter than the present, with nearly ice-free conditions over the Northern Hemisphere, and significant differences in vegetation distribution. There still is considerable uncertainty in the reconstructed CO2 levels for this time period, fostered by the temporally and spatially biased distribution of the available proxy record. Previous model-data comparison studies (i.e. Bradshaw et al., 2012; Pound et al., 2011) highlighted the mismatch between model results and proxy data for this time period. Here, we investigate how taking into account the variability due to changes in orbital forcing can account for some of these differences. We also explore the orbital control on the monsoonal systems at millennial scale resolution, as well as the impact of background CO2 on orbital sensitivity. Long-term changes in seasonal and latitudinal solar insolation are generated by periodic oscillations in the Earth's orbit and tilt relative to the Sun. These cycles have a modulating effect on climate and ocean circulation patterns. A record of this signal can be found in a number of terrestrial and marine sedimentary sequences. A series of 22 fully coupled atmosphere-ocean-vegetation simulations has been run through an entire precession cycle during the Late Miocene (~6.5 Ma). These experiments were performed using HadCM3L (Hadley Centre Coupled Model, Version 3 - Low resolution ocean) with TRIFFID (Top-down Representation of Interactive Foliage and Flora Including Dynamics) to test the climatic response to changes in orbital forcing. The Mediterranean Sea provides a remarkable geological record for this time slice. Several sequences around the basin margins have been astronomically tuned so that high resolution geological data can be directly compared with our model results. However, this is not the case for the rest of the world, where the distribution of climate proxy data for the Late Miocene is sparse, patchy and is typically constrained by a low-resolution age model. Model results show the effect of different orbital configurations on the North African summer monsoon, with highly intensified precipitation patterns over these regions at times of minimum precession (maximum insolation), triggering significant changes in vegetation belts. Our simulations are compared quantitatively with the palaeorecord and show that orbital forcing could explain some, but not all, of the published model-data mismatch. Bradshaw, C. D., Lunt, D. J., Flecker, R., Salzmann, U., Pound, M. J., Haywood, A. M., and Eronen, J. T.: The relative roles of CO2 and palaeogeography in determining late Miocene climate: results from a terrestrial model-data comparison, Clim. Past, 8, 1257-1285, 2012. Pound, M. J., Haywood, A. M., Salzmann, U., Riding, J. B., Lunt, D. J., and Hunter, S. J.: A Tortonian (late Miocene, 11.61-7.25 Ma) global vegetation reconstruction, Palaeogeogr. Palaeocl., 300, 29-45, 2011.

Marzocchi, Alice; Lunt, Dan; Flecker, Rachel; Bradshaw, Catherine

2014-05-01

149

Ostracoda (Arthropoda, Crustacea) in a Miocene oxygen minimum zone, Trinidad, West Indies: A test of the Platycopid Signal Hypothesis  

NASA Astrophysics Data System (ADS)

Studies of Recent ostracodes around the area of South America shed little light on the paleoenvironmental interpretation of Miocene assemblages. Consequently, interpretations of the Miocene ostracode assemblages must be supplemented using evidence from better documented taxa. Benthic foraminifera in samples from the Lower to Middle Miocene Brasso Formation at Brasso Village, Trinidad, have previously been used to distinguish three sample groupings (Beneath, Within and Above) around an oxygen minimum zone (OMZ), this being a layer of water within which dissolved oxygen concentrations can be as low as 0.1-1.0 mL/L. Using these same samples and the foraminiferal assemblage demarcations relative to the OMZ, this paper examines the associated and rich ostracode fauna of the Brasso Formation. The mean recovery of ostracode valves per sample was approximately three times greater in the Within OMZ sample group than in either of the Beneath OMZ or Above OMZ groups, perhaps reflecting the exclusion of macro-predators from within the OMZ. Individual rarefaction of species richness S to N = 300 valves was conducted for each sample group. This showed that S did not differ between the sample groups, ranging from 22.4 to 24.8. We used all ostracode species to model group separation. Based upon the Mahalanobis' criterion, we obtained significant group separation using a model with four taxa: Munseyella ex gr. minuta, Argilloecia posterotruncata, Munseyella sp. and Xestoleberis sp., while a fifth, Argilloecia spp., provided a significant but minor increase in separation probabilities over all groups. The two most abundant species (Bradleya sp., Gangamocytheridea reticulata) were thus not the best species for detecting the OMZ. Platycopid ostracodes of the genus Cytherella were found throughout the section, rather than concentrated within the OMZ, which contradicts the Platycopid Signal Hypothesis that OMZs are characterized by platycopid dominance. The total distribution and turnover of both ostracodal and foraminiferal assemblages were compared and contrasted quantitatively using a total assemblage turnover index (ATI) and the paleoenvironmental importance evaluated. The correlated between-sample ATI is for both groups lowest within the OMZ.

Wilson, Brent; Coimbra, João C.; Hayek, Lee-Ann C.

2014-10-01

150

A mantle plume beneath California? The mid-Miocene Lovejoy Flood Basalt, northern California  

USGS Publications Warehouse

The Lovejoy basalt represents the largest eruptive unit identified in California, and its age, volume, and chemistry indicate a genetic affinity with the Columbia River Basalt Group and its associated mantle-plume activity. Recent field mapping, geochemical analyses, and radiometric dating suggest that the Lovejoy basalt erupted during the mid-Miocene from a fissure at Thompson Peak, south of Susanville, California. The Lovejoy flowed through a paleovalley across the northern end of the Sierra Nevada to the Sacramento Valley, a distance of 240 km. Approximately 150 km3 of basalt were erupted over a span of only a few centuries. Our age dates for the Lovejoy basalt cluster are near 15.4 Ma and suggest that it is coeval with the 16.1-15.0 Ma Imnaha and Grande Ronde flows of the Columbia River Basalt Group. Our new mapping and age dating support the interpretation that the Lovejoy basalt erupted in a forearc position relative to the ancestral Cascades arc, in contrast with the Columbia River Basalt Group, which erupted in a backarc position. The arc front shifted trenchward into the Sierran block after 15.4 Ma. However, the Lovejoy basalt appears to be unrelated to volcanism of the predominantly calc-alkaline Cascade arc; instead, the Lovejoy is broadly tholeiitic, with trace-element characteristics similar to the Columbia River Basalt Group. Association of the Lovejoy basalt with mid-Miocene flood basalt volcanism has considerable implications for North American plume dynamics and strengthens the thermal "point source" explanation, as provided by the mantle-plume hypothesis. Alternatives to the plume hypothesis usually call upon lithosphere-scale cracks to control magmatic migrations in the Yellowstone-Columbia River basalt region. However, it is difficult to imagine a lithosphere-scale flaw that crosses Precambrian basement and accreted terranes to reach the Sierra microplate, where the Lovejoy is located. Therefore, we propose that the Lovejoy represents a rapid migration of plume-head material, at ??20 cm/yr to the southwest, a direction not previously recognized. ?? 2008 The Geological Society of America.

Garrison, N.J.; Busby, C.J.; Gans, P.B.; Putirka, K.; Wagner, D.L.

2008-01-01

151

Porosity evolution of upper Miocene reefs, Almeria Province, southern Spain  

USGS Publications Warehouse

Sea cliffs 40 km east of Almeria, southeastern Spain, expose upper Miocene reefs and patch reefs of the Plomo formation. These reefs are formed of scleractinian corals, calcareous algae, and mollusks. The reef cores are as much as 65 m thick and several hundred meters wide. Fore-reef talus beds extend 1,300 m across and are 40 m thick. The reefs and reef breccias are composed of calcific dolomite. They lie on volcanic rocks that have a K-Ar date of 11.5 m.y. and in turn are overlain by the upper Miocene Vicar Formation. In the reef cores and fore-reef breccia beds, porosity is both primary and postdepositional. Primary porosity is of three types: (a) boring clam holes in the scleractinian coral heads, cemented reef rocks, and breccias; (b) intraparticle porosity within the corals, Halimeda plates, and vermetid worm tubes; and (c) interparticle porosity between bioclastic fragments and in the reef breccia. Postdepositional moldic porosity was formed by the solution of aragonitic material such as molluscan and coral fragments. The Plomo reef carbonate rocks have high porosity and permeability, and retain a great amount of depositional porosity. Pores range in size from a few micrometers to 30 cm. The extensive intercrystalline porosity and high permeability resulted from dolomitization of micritic matrix. Dolomite rhombs are between 10 and 30 ? across. More moldic porosity was formed by the dissolution of the calclte bioclasts. Some porosity reduction has occurred by incomplete and partial sparry calcite infilling of interparticular, moldic, and intercrystalline voids. The high porosity and permeability of these reefs make them important targets for petroleum exploration in the western Mediterranean off southern Spain. In these offshore areas in the subsurface the volcanic ridge and the Plomo reef complex are locally onlapped or overlapped by 350 m or more of Miocene(?) and Pliocene fine-grained sedimentary rocks. The possibility exists that the buried Plomo reef deposits may form traps for oil and gas in the offshore areas southwest of the type locality. Stratigraphic traps also may occur where the Neogene sequence above the Plomo reef complex onlaps the volcanic ridge.

Armstrong, A. K.; Snavely, P. D.; Addicott, W. O.

1980-01-01

152

Biostratigraphic sequence analysis of two Lower Miocene to Pliocene sections, Eastern Falcon, Northwestern Venezuela  

SciTech Connect

The eastern region of the Falcon Basin in northwestern Venezuela comprises a thick sedimentary sequence deposited from a deep marine bathyal to neritic environment, ranging in age from the Middle Eocene to the Pliocene. A detailed biostratigraphic study (foraminifera and calcareous nannoplankton) was carried out in two sedimentary sequences outcropping in Cumarebo and Piritu, adjacent areas of eastern Falcon, representing: platform, slope and basinal settings. The Cumarebo section is continuous in the studied interval, from the Middle Miocene to the Pliocene. The Piritu section is continuous from the Lower to the lower Upper Miocene, terminating unconformably beneath a thin interval of middle Pliocene platform sediments, indicating tectonism during the latest Miocene. The sequence stratigraphical interpretation was based on the biostratigraphic analysis of the benthic and planktonic fossils, facies distribution and sedimentological data. Systems tracts, sequence boundaries and maximum flooding surfaces from cycles TB2.4 to TB3.5 of the cycle chart were identified. In the Cumarebo section, the upper Middle and Upper Miocene is mostly composed of shales, with some turbiditic sands belonging to a LSW system tract. The upper most Miocene contains a thick carbonate buildup (HST), and it is overlain by a Pliocene section that shallows upward from upper slope to outer shelf depositional environments. In the basinal (Piritu) section, most of the sediments are deep-water shales belonging to a LSW system tract, with some turbiditic sands in the upper Lower Miocene. TST and HST sediments, with scattered carbonate buildups in the upper Middle Miocene were also identified.

Diaz De Gamero, M.L. (Universidad Central de Venezuela, Caracus (Venezuela)); Giffuni, G.; Castro Mora, M. (Lagoven S.A., Caracus (Venezuela))

1993-02-01

153

Scope and construction of a gas and oil atlas series of the Gulf of Mexico: Examples from Texas offshore lower Miocene plays  

SciTech Connect

An atlas series about the offshore northern Gulf of Mexico will group gas and oil reservoirs into subregional plays and will display reservoir data on a computerized geographical information system. The atlas series will provide critically compiled reservoir engineering data to help the private sector explore and develop hydrocarbons and to help the public sector analyze the hydrocarbon endowment in this basin. In this report, we cover aspects of the play-analysis procedure and provide specific examples of lower Miocene plays from the upper Texas coast and Federal Outer Continental Shelf (OCS). Play analysis emphasizes using broad classes of structural style, depositional style and environments, and defining attributes to group reservoirs into plays. To date, we have identified 4 Oligocene and 25 Miocene plays in Texas State offshore waters and 115 plays in the Federal OCS. Texas State offshore plays are gas prone (cumulative production 3.7 TcF) and are preferentially trapped in rollover anticlines. Miocene plays include submarine-fan Lenticulina sandstones; progradational Dicorbis b., Siphonina d., Marginulina a., and Lenticulina sandstones; transgressive sandstones associated with a barrier-bar system in the Matagorda Area; and transgressive Amphistegina B sandstones. Particularly productive gas-prone plays are progradational Sihonina d. deltas in the High Island Area and progradational Marginulia a. shelf and deltaic sandstones in the Matagorda Island and Brazos Areas.

Seni, S.J.; Desselle, B.A.; Standen, A. [Univ. of Texas, Austin, TX (United States)

1994-12-31

154

Ruminant diets and the Miocene extinction of European great apes.  

PubMed

The successful evolutionary radiations of European hominoids and pliopithecoids came to an end during the Late Miocene. Using ruminant diets as environmental proxies, it becomes possible to detect variations in vegetation over time with the potential to explain fluctuations in primate diversity along a NW-SE European transect. Analysis shows that ruminants had diverse diets when primate diversity reached its peak, with more grazers in eastern Europe and more browsers farther west. After the drop in primate diversity, grazers accounted for a greater part of western and central European communities. Eastwards, the converse trend was evident with more browsing ruminants. These opposite trends indicate habitat loss and an increase in environmental uniformity that may have severely favoured the decline of primate diversity. PMID:20519220

Merceron, Gildas; Kaiser, Thomas M; Kostopoulos, Dimitris S; Schulz, Ellen

2010-10-22

155

Simultaneous Miocene Extension and Shortening in the Himalayan Orogen  

NASA Astrophysics Data System (ADS)

The South Tibetan detachment system separates the high-grade metamorphic core of the Himalayan orogen from its weakly metamorphosed suprastructure. It is thought to have developed in response to differences in gravitational potential energy produced by crustal thickening across the mountain front. Geochronologic data from the Rongbuk Valley, north of Qomolangma (Mount Everest) in southern Tibet, demonstrate that at least one segment of the detachment system was active between 19 and 22 million years ago, an interval characterized by large-scale crustal thickening at lower structural levels. These data suggest that decoupling between an extending upper crust and a converging lower crust was an important aspect of Himalayan tectonics in Miocene time.

Hodges, K. V.; Parrish, R. R.; Housh, T. B.; Lux, D. R.; Burchfiel, B. C.; Royden, L. H.; Chen, Z.

1992-11-01

156

Ruminant diets and the Miocene extinction of European great apes  

PubMed Central

The successful evolutionary radiations of European hominoids and pliopithecoids came to an end during the Late Miocene. Using ruminant diets as environmental proxies, it becomes possible to detect variations in vegetation over time with the potential to explain fluctuations in primate diversity along a NW–SE European transect. Analysis shows that ruminants had diverse diets when primate diversity reached its peak, with more grazers in eastern Europe and more browsers farther west. After the drop in primate diversity, grazers accounted for a greater part of western and central European communities. Eastwards, the converse trend was evident with more browsing ruminants. These opposite trends indicate habitat loss and an increase in environmental uniformity that may have severely favoured the decline of primate diversity. PMID:20519220

Merceron, Gildas; Kaiser, Thomas M.; Kostopoulos, Dimitris S.; Schulz, Ellen

2010-01-01

157

Miocene climate seasonality in southern India - first direct evidence for a weak Indian monsoon during the Middle Miocene Climate Optimum  

NASA Astrophysics Data System (ADS)

The Asian monsoon is an integral component of the global climate system. This large-scale atmospheric circulation comprises the East Asian summer and winter monsoon and the Indian monsoon subsystems, all characterized by seasonal reversing winds and precipitation changes associated with asymmetric heating of land and sea. The Neogene monsoon history is mainly reconstructed from chemical and physical weathering rates recorded in widely continuous marine sequences of the Indus Fan, Bengal Fan and South China Sea, which, depending on the source, physiography and sediment, indicate drier or wetter climates. These indirect climate proxies display an unusually dry period during the Middle Miocene Climate Optimum (MMCO, 16.5-15 Ma). As part of the FWF-projects P18189, P21414 and P23492, we present an Early/Middle Miocene coastal palynoflora record from the siliciclastic Ambalapuzha Formation at the coastal cliff of Varkala (Kerala Basin, SW India). Pollen assemblages and facies document a coastal wetland with mangrove vegetation. The Coexistence Approach was applied for palaeoclimatic reconstructions. This method uses climatic tolerances of all nearest living relatives known for a fossil flora by assuming that the tolerances of a fossil taxon are not significantly different from its modern counterpart. The maximum overlap of the environmental tolerances of all nearest living relatives (coexistence interval) is then regarded as being indicative of the most likely palaeoenvironment. By enquiring the Palaeoflora Database (http://www.palaeoflora.de/), the palaeoclimatic parameters of the pollen flora were calculated. The reconstructed climatic parameters for the MMCO show a seasonal precipitation pattern with a dry and a wet period and moderate rainfalls during the warmest period, which is comparable to the present day annual precipitation cycle in coastal Kerala, and affirms the presence of a monsoon-like atmospheric circulation over South India during the MMCO. However, the precipitation amounts during the wet (average 75%) and the warmest period (average 68%) were significantly reduced compared to today, while the rainfalls during the dry seasons are in the same order. This implies a weak Indian monsoon during the MMCO and a low thermal land - sea gradient between the Eurasian landmass and the Indian Ocean. Although a ~3°C warmer global climate during the MMCO and a weaker monsoon accounts for a higher near-surface air temperature during summer, the calculated mean annual temperature (MAT; 24.4°C) is 2.7°C lower than at present. The estimated warmest month temperature is, however, in the same range as today. Therefore, the low coldest month temperature (CMT; 20.6-22.8°C) in the Miocene has to account for the high MAT difference. This parameter represents the lower temperature threshold of the Varkala flora, and displays only the minimum temperature during the coldest month, which is significantly lower than the average CMT. Accordingly, the Miocene CMT approximates the present 24-h minimum temperature during the coldest month in Kerala (22.4°C). The reconstructed seasonal temperature cycle supports climate models, which suggest a higher temperature increase in mid-latitudes than in low-latitudes as well as warmer equatorial sea surface temperatures during the MMCO.

Piller, W. E.; Reuter, M.; Kern, A. K.; Harzhauser, M.

2012-04-01

158

Herds Overhead: Nimbadon lavarackorum (Diprotodontidae), Heavyweight Marsupial Herbivores in the Miocene Forests of Australia  

PubMed Central

The marsupial family Diprotodontidae (Diprotodontia, Vombatiformes) is a group of extinct large-bodied (60–2500 kg) wombat-like herbivores that were common and geographically widespread in Cenozoic fossil deposits of Australia and New Guinea. Typically they are regarded to be gregarious, terrestrial quadrupeds and have been likened in body form among placental groups to sheep, rhinoceros and hippopotami. Arguably, one of the best represented species is the zygomaturine diprotodontid Nimbadon lavarackorum which is known from exceptionally well-preserved cranial and postcranial material from the middle Miocene cave deposit AL90, in the Riversleigh World Heritage Area, northwestern Queensland. Here we describe and functionally analyse the appendicular skeleton of Nimbadon lavarackorum and reveal a far more unique lifestyle for this plesiomorphic and smallest of diprotodontids. Striking similarities are evident between the skeleton of Nimbadon and that of the extant arboreal koala Phascolarctos cinereus, including the powerfully built forelimbs, highly mobile shoulder and elbow joints, proportionately large manus and pes (both with a semi-opposable digit I) and exceedingly large, recurved and laterally compressed claws. Combined with the unique (among australidelphians) proportionately shortened hindlimbs of Nimbadon, these features suggest adept climbing ability, probable suspensory behaviour, and an arboreal lifestyle. At approximately 70 kg, Nimbadon is the largest herbivorous mammal to have occupied the forest canopies of Australia - an ecological niche that is no longer occupied in any Australian ecosystem and one that further expands the already significant niche diversity displayed by marsupials during the Cenozoic. PMID:23185250

Black, Karen H.; Camens, Aaron B.; Archer, Michael; Hand, Suzanne J.

2012-01-01

159

Paleomagnetism of Miocene East African Rift sediments and the calibration of the geomagnetic reversal time scale  

NASA Astrophysics Data System (ADS)

Paleomagnetic stratigraphy and K-Ar age determinations are reported for the type section of the middle Miocene Ngorora Formation, found in the Kenya rift valley. The magnetostratigraphy is well correlated to the geomagnetic reversal time scale (GRTS) and spans from the lower part of Chron C5 (9) to Chron C5AB-r (14). K-Ar dates were determined for euhedral sanidines, handpicked from seven tuff horizons within the Ngorora Formation and the underlying Turn phonolite flow. These dates can therefore be tied directly to the GRTS. The eight dates fall into three discrete groups averaging 12.5±0.22 Ma (mean and standard deviation of results from four tuffs), 11.6±0.06 Ma (mean and standard deviation from three tuffs), and 10.16±0.38 (average of three analyses from one tuff). We interpret the age groups as resulting from three successive eruptive episodes, the stratigraphic positions of which are well constrained. In spite of episodic supply at the eruptive source, sediment accumulation is continuous at the resolution of the GRTS. This suggests that accumulation is controlled by basin subsidence rather than sediment supply. Sanidine dates support an age for the older boundary of marine magnetic anomaly 5 of about 10 Ma, as opposed to 11.12 Ma, suggested by the most recent results from Icelandic basaltic lava flows.

Tauxe, L.; Monaghan, M.; Drake, R.; Curtis, G.; Staudigel, H.

1985-05-01

160

Extent of underthrusting of the Indian plate beneath Tibet controlled the distribution of Miocene porphyry Cu-Mo ± Au deposits  

NASA Astrophysics Data System (ADS)

Miocene igneous rocks in the 1,600 km-long E-W Gangdese belt of southern Tibet form two groups separated at longitude ˜89° E. The eastern group is characterized by mainly intermediate-felsic calc-alkaline plutons with relatively high Sr/Y ratios (23 to 342), low (87Sr/86Sr)i ratios (0.705 to 0.708), and high ?Ndi values (+5.5 to -6.1). In contrast, the western group is characterized by mainly potassic to ultrapotassic volcanic rocks with relatively high Th and K2O contents, low Sr/Y ratios (11 to 163), high (87Sr/86Sr)i ratios (0.707 to 0.740), and low ?Ndi values (-4.1 to -17.5). The eastern plutonic group is associated with several large porphyry Cu-Mo ± Au deposits, whereas the western group is largely barren. We propose that the sharp longitudinal distinction between magmatism and metallogenic potential in the Miocene Gangdese belt reflects the breakoff of the Greater India slab and the extent of underthrusting by the Indian continental lithosphere at that time. Magmas to the east of ˜89° E were derived by partial melting of subduction-modified Tibetan lithosphere (mostly lower crust) triggered by heating of hot asthenospheric melt following slab breakoff. These magmas remobilized metals and volatile residual in the crustal roots from prior arc magmatism and generated porphyry Cu-Mo ± Au deposits upon emplacement in the upper crust. In contrast, magmas to the west of ˜89° E were formed by smaller volume partial melting of Tibetan lithospheric mantle metasomatized by fluids and melts released from the underthrust Indian plate. They are less hydrous and oxidized and did not have the capacity to transport significant amounts of metals into the upper crust.

Wang, Rui; Richards, Jeremy P.; Hou, Zengqian; Yang, Zhiming

2014-02-01

161

Late Miocene lineage divergence and ecological differentiation of rare endemic Juniperus blancoi: clues for the diversification of North American conifers.  

PubMed

Western North America and Mexico contain a large number of conifer species. This diversity could be the product of orographic and climate changes of the late Tertiary and Quaternary. In this study, we focus on the evolutionary history of Juniperus blancoi, in order to determine the impact of climate change and environmental heterogeneity on population differentiation. We estimated the population structure, phylogenetic relationships and historical demography of J. blancoi populations using nuclear genes. We correlated genetic structure with ecological differentiation, divergence times and changes in population size. Populations of J. blancoi are differentiated into three lineages that correspond to low-, mid- and high-altitude populations. The three groups diversified in the late Miocene, early Pliocene, with only a few events of gene flow since then. Two lineages in the north exhibited a pattern of population growth during the Pleistocene that could be linked to climate changes. Populations of J. blancoi experienced significant ecological differentiation and early divergence events, which correspond to periods of global cooling and mountain uplift during the Miocene. This suggests that mountain ranges in tropical and subtropical latitudes play an important role in the speciation and persistence of conifer taxa in diversity hotspots, by providing diverse environmental conditions. PMID:24611638

Moreno-Letelier, Alejandra; Mastretta-Yanes, Alicia; Barraclough, Timothy G

2014-07-01

162

Late Miocene paleoenvironment of the Lambert Graben embayment, East Antarctica, evident from: Mollusc paleontology, sedimentology and geochemistry  

NASA Astrophysics Data System (ADS)

The Upper Miocene (10.7-9.0 Ma) Battye Glacier Formation was deposited ˜250 km inland from the modern Amery Ice Shelf edge in Prydz Bay, East Antarctica. The composition of clay minerals distinguishes a Lower Member, which reflects regional erosion of Precambrian metamorphic basement, from an Upper Member, which records increased erosion of local Permian-Triassic Amery Group strata. The Upper Member was deposited in an ice-proximal environment akin to the modern fjords of East Greenland, with substantial diamict deposition resulting from melting iceberg discharge. The Lower Member was deposited in an ice-distal environment and included the accumulation of the fossil-bearing McLeod Beds. The McLeod Beds contain much siliceous biogenic sediment (? 15% opal), which is rare to absent in the predominantly hemipelagic mud of modern East Greenland fjords. The McLeod Beds also contain largely monospecific in situ Hiatella sp. mollusc assemblages suggestive of environmental stress, potentially caused by low salinity melt-water and a high input of terrigenous sediment, which excluded most other benthic taxa. Geochemical results from primary aragonite in Hiatella shells imply large freshwater input into the marine environment during mollusc growth, causing low ?18O, Na, Mg and high Fe values. The present study indicates that iceberg melt-water influence entering the marine environment was greater during the Late Miocene than today around Antarctica, and documents the paleoenvironment associated with a discrete period of ice margin retreat and marine incursion into the Lambert embayment.

Whitehead, Jason M.; Ehrmann, Werner; Harwood, David M.; Hillenbrand, Claus-Dieter; Quilty, Patrick G.; Hart, Charles; Taviani, Marco; Thorn, Vanessa; McMinn, Andrew

2006-04-01

163

Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)  

E-print Network

The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or ...

Ulrich, Kotthoff; Torsten, Wappler; Engel, Michael S.

2011-03-10

164

Miocene karst drainage system: seismic stratigraphy of the continental shelf west of Florida  

Microsoft Academic Search

High-resolution geophysical data recorded on the continental shelf west of Tampa Bay, Florida show three stratigraphic units: Holocene, Plio-Pleistocene, and Miocene. Within the Miocene unit is an expansive drainage system extending about 80 kilometers offshore. In most areas, a system such as this would typically be characterized as a paleo-fluvial system. Although this drainage system probably initiated fluvially, geophysical data

1985-01-01

165

Widespread Miocene deep-sea hiatuses: coincidence with periods of global cooling.  

USGS Publications Warehouse

High-resolution biostratigraphic analyses of Miocene deep-sea cores reveal eight intervals of widespread hiatuses in the world ocean. In complete sections these hiatuses correspond to intervals of cool faunal and floral assemblages, rapid enrichment of delta 18O, and sea-level regressions. These factors suggest that Miocene deep-sea hiatuses result from an increased intensity of circulation and corrosiveness of bottom currents during periods of increased polar refrigeration.-Authors

Barron, J. A.; Keller, G.

1982-01-01

166

Depositional and structural evolution of the Middle Miocene depositional episode, east-central Gulf of Mexico  

Microsoft Academic Search

Two widespread, transgressive deposits associated with the faunal top Amphistegina B (15.5 Ma) and Textularia W (12.1 Ma) define the Middle Miocene depositional episode. An extensive stratigraphic correlation framework established in this study allowed tracing of the middle Miocene sediment dispersal system from the shelf through the slope to the basin floor in the complex paleogeography of the east-central Gulf

Ricardo Ignacio Combellas Bigott

2003-01-01

167

Paleomagnetic and geochronologic constraints on the Miocene evolution of semi-isolated basins in southeastern Europe  

Microsoft Academic Search

This thesis addresses the Miocene evolution of the Central Paratethys and neighboring Dinaride Mountains. The Central Paratethys was a vast epicontinental sea covering most of central and southeastern Europe during the Oligo-Miocene. The Dinarides were situated along the southwestern border of the former Central Paratethys, separating it from the Mediterranean. An extensive long-lived lake system thrived in the orogen’s intra-montane

J. H. W. M. de Leeuw

2011-01-01

168

Early and Middle Miocene stable isotopes: Implications for Deepwater circulation and climate  

NASA Astrophysics Data System (ADS)

The middle Miocene ?18O increase represents a fundamental change in the ocean-atmosphere system which, like late Pleistocene climates, may be related to deepwater circulation patterns. There has been some debate concerning the early to early middle Miocene deepwater circulation patterns. Specifically, recent discussions have focused on the relative roles of Northern Component Water (NCW) production and warm, saline deep water originating in the eastern Tethys. Our time series and time slice reconstructions indicate that NCW and Tethyan outflow water, two relatively warm deepwater masses, were produced from ˜20 to 16 Ma. NCW was produced again from 12.5 to 10.5 Ma. Another feature of the early and middle Miocene oceans was the presence of a high ?13C intermediate water mass in the southern hemisphere, which apparently originated in the Southern Ocean. Miocene climates appear to be related directly to deepwater circulation changes. Deep-waters warmed in the early Miocene by ˜3°C (˜20 to 16 Ma) and cooled by a similar amount during the middle Miocene ?18O increase (14.8 to 12.6 Ma), corresponding to the increase (˜20 Ma) and subsequent decrease (˜16 Ma) in the production of NCW and Tethyan outflow water. Large (>0.6 ‰), relatively rapid (˜0.5 m.y.) ?18O increases in both benthic and planktonic foraminifera (i.e., the Mi zones of Miller et al. (1991a) and Wright and Miller (1992a)) were superimposed in the long-term deepwater temperature changes; they are interpreted as reflecting continental ice growth events. Seven of these m.y. glacial/interglacial cycles have been recognized in the early to middle Miocene. Two of these glacial/interglacial cycles (Mi3 and Mi4) combined with a 2° to 3°C decrease in deepwater temperatures to produce the middle Miocene ?18O shift.

Wright, James D.; Miller, Kenneth G.; Fairbanks, Richard G.

1992-06-01

169

Correlation of Miocene sequences and hydrogeologic units, New Jersey Coastal Plain  

Microsoft Academic Search

We have developed a Miocene sequence stratigraphic framework using data from recently drilled boreholes in the New Jersey Coastal Plain. Sequences are shallowing upward, unconformity-bounded units; fine-grained shelf and prodelta sediments grade upward to delta front and shallow-marine sands, corresponding to confining bed—aquifer couplets. By dating Miocene sequences using Sr-isotope stratigraphy, and mapping with borehole data and geophysical logs, we

Peter J. Sugarman; Kenneth G. Miller

1997-01-01

170

Miocene karst drainage system: seismic stratigraphy of the continental shelf west of Florida  

SciTech Connect

High-resolution geophysical data recorded on the continental shelf west of Tampa Bay, Florida show three stratigraphic units: Holocene, Plio-Pleistocene, and Miocene. Within the Miocene unit is an expansive drainage system extending about 80 kilometers offshore. In most areas, a system such as this would typically be characterized as a paleo-fluvial system. Although this drainage system probably initiated fluvially, geophysical data showing much evidence of karstification suggest that this system probably formed on the inner shelf as a result of large scale dissolution and collapse of Miocene limestones during lowered sea-level. The overlying Plio-Pleistocene unit infills the Miocene drainage system, while exiguously covering Miocene rocks in areas where the system is absent. Deposition of this unit probably took place during high-stands of sea-level, followed by erosion and transport of sediment farther offshore, exposing Miocene rocks. The Holocene unit sporadically covers underlying units throughout the study area. Sediments making up this unit have been reworked into several bedform types probably resulting from various boundary layer flow events such as hurricanes, storms, currents and tides. This scenario is probably not unique to the continental shelf west of Tampa Bay, Florida, but may also characterize other karstic shelves where paleo-fluvial processes were previously thought to be the dominant mechanism forming paleo-coastal drainage systems.

Herbert, J.A.

1985-01-01

171

Early Miocene origin and cryptic diversification of South American salamanders  

PubMed Central

Background The currently recognized species richness of South American salamanders is surprisingly low compared to North and Central America. In part, this low richness may be due to the salamanders being a recent arrival to South America. Additionally, the number of South American salamander species may be underestimated because of cryptic diversity. The aims of our present study were to infer evolutionary relationships, lineage diversity, and timing of divergence of the South American Bolitoglossa using mitochondrial and nuclear sequence data from specimens primarily from localities in the Andes and upper Amazon Basin. We also estimated time of colonization of South America to test whether it is consistent with arrival via the Panamanian Isthmus, or land bridge connection, at its traditionally assumed age of 3 million years. Results Divergence time estimates suggest that Bolitoglossa arrived in South America from Central America by at least the Early Miocene, ca. 23.6 MYA (95% HPD 15.9-30.3 MYA), and subsequently diversified. South American salamanders of the genus Bolitoglossa show strong phylogeographic structure at fine geographic scales and deep divergences at the mitochondrial gene cytochrome b (Cytb) and high diversity at the nuclear recombination activating gene-1 (Rag1). Species often contain multiple genetically divergent lineages that are occasionally geographically overlapping. Single specimens from two southeastern localities in Ecuador are sister to the equatoriana-peruviana clade and genetically distinct from all other species investigated to date. Another single exemplar from the Andes of northwestern Ecuador is highly divergent from all other specimens and is sister to all newly studied samples. Nevertheless, all sampled species of South American Bolitoglossa are members of a single clade that is one of several constituting the subgenus Eladinea, one of seven subgenera in this large genus. Conclusions The ancestors of South American salamanders likely arrived at least by the Early Miocene, well before the completion of the Late Pliocene Panamanian land bridge (widely accepted as ca. 3 MYA). This date is in agreement with recent, controversial, arguments that an older, perhaps short-lived, land connection may have existed between South America and present-day Panama 23–25 MYA. Since its arrival in South America, Bolitoglossa has diversified more extensively than previously presumed and currently includes several cryptic species within a relatively small geographic area. Rather than two upper Amazonian species currently recorded for this region, we propose that at least eight should be recognized, although these additional lineages remain to be formally described. PMID:23497060

2013-01-01

172

Subcellular preservation in giant ostracod sperm from an early Miocene cave deposit in Australia.  

PubMed

Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 µm in length, but they are the only group to have aflagellate, filamentous giant sperm. The evolution and function of this highly unusual feature of reproduction with giant sperm are currently unknown. The hypothesis of long-term evolutionary persistence of this kind of reproduction has never been tested. We here report giant sperm discovered by propagation phase contrast X-ray synchrotron micro- and nanotomography, preserved in five Miocene ostracod specimens from Queensland, Australia. The specimens belong to the species Heterocypris collaris Matzke-Karasz et al. 2013 (one male and three females) and Newnhamia mckenziana Matzke-Karasz et al. 2013 (one female). The sperm are not only the oldest petrified gametes on record, but include three-dimensional subcellular preservation. We provide direct evidence that giant sperm have been a feature of this taxon for at least 16 Myr and provide an additional criterion (i.e. longevity) to test hypotheses relating to origin and function of giant sperm in the animal kingdom. We further argue that the highly resistant, most probably chitinous coats of giant ostracod sperm may play a role in delaying decay processes, favouring early mineralization of soft tissue. PMID:24827442

Matzke-Karasz, Renate; Neil, John V; Smith, Robin J; Symonová, Radka; Mo?kovský, Libor; Archer, Michael; Hand, Suzanne J; Cloetens, Peter; Tafforeau, Paul

2014-07-01

173

The Quilon Limestone (Kerala Basin/India) - an archive for Miocene Indo-Pacific seagrass beds  

NASA Astrophysics Data System (ADS)

The Quilon Formation of the Kerala Basin (SW India) is characterized by carbonate rocks which belong to the Warkalli Group and are interbedded between siliciclastic formations. It comprises at least 2 horizons of fossiliferous limestone with marine fauna. The lower limestone horizon is characterized by colonial corals, while the upper horizon represents a larger foraminiferal Pseudotaberina malabarica facies which is well developed at the type locality, the coastal cliffs of Ashtamudi Lake at Padappakkara in SW India. The sediment there is either a weakly cemented carbonate sand rich in foraminifers and gastropods or a fossiliferous limestone. Facies and faunal composition clearly indicate a seagrass environment. Recent seagrasses have their centre of generic richness in the Indo-Pacific where they cover wide areas in the tidal and shallow subtidal zones. However, their geological record is only fragmentary and their palaeobiogeographic record has a big gap in the Western Indo-Pacific region. The newly reported nannoplankton flora and planktonic foraminifers from the Quilon Formation demonstrate that the deposition of the studied seagrass bed occurred in nannoplankton biozone NN3. This timing suggests a formation during the closure of the Tethyan Seaway. It designates the Quilon Limestone as an early Western Indo-Pacific seagrass bed and documents an important step in the history of seagrass communities. The large discoidal soritid foraminifer Pseudotaberina malabarica is considered as proxy for Miocene seagrass communities in the Indo-Pacific region.

Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias; Kroh, Andreas; Rögl, Fred; Coric, Stjepan

2010-05-01

174

Resource partitioning among top predators in a Miocene food web  

PubMed Central

The exceptional fossil sites of Cerro de los Batallones (Madrid Basin, Spain) contain abundant remains of Late Miocene mammals. From these fossil assemblages, we have inferred diet, resource partitioning and habitat of three sympatric carnivorous mammals based on stable isotopes. The carnivorans include three apex predators: two sabre-toothed cats (Felidae) and a bear dog (Amphicyonidae). Herbivore and carnivore carbon isotope (?13C) values from tooth enamel imply the presence of a woodland ecosystem dominated by C3 plants. ?13C values and mixing-model analyses suggest that the two sabre-toothed cats, one the size of a leopard and the other the size of a tiger, consumed herbivores with similar ?13C values from a more wooded portion of the ecosystem. The two sabre-toothed cats probably hunted prey of different body sizes, and the smaller species could have used tree cover to avoid encounters with the larger felid. For the bear dog, ?13C values are higher and differ significantly from those of the sabre-toothed cats, suggesting a diet that includes prey from more open woodland. Coexistence of the sabre-toothed cats and the bear dog was likely facilitated by prey capture in different portions of the habitat. This study demonstrates the utility of stable isotope analysis for investigating the behaviour and ecology of members of past carnivoran guilds. PMID:23135673

Domingo, M. Soledad; Domingo, Laura; Badgley, Catherine; Sanisidro, Oscar; Morales, Jorge

2013-01-01

175

Miocene vegetation and climatic changes reconstructed from a sporopollen record of the Tianshui Basin, NE Tibetan Plateau  

Microsoft Academic Search

The Miocene vegetation and climate history of western China remains unclear. However, widely-distributed Miocene sediments of the Tianshui Basin in the NE Tibetan Plateau provide a great potential for deciphering the Miocene vegetation and climate history of this region. This paper presents first sporopollen record from these sediments, covering the period from 17.1 to 6.1Ma. Sporopollen data reveal that temperate,

Zhengchuang Hui; Jijun Li; Qinghai Xu; Chunhui Song; Jun Zhang; Fuli Wu; Zhijun Zhao

2011-01-01

176

More evidence for a glacial world prior to the middle Miocene oxygen-isotope enrichment event: resolution of early Miocene glacioeustatic sea-level cyclicity from North Carolina  

SciTech Connect

Benthic delta/sup 18/O analyses from DSDP sites worldwide have documented a positive excursion (similarly ordered + 1.5%) through the early-middle Miocene. These data are traditionally interpreted as marking the transition from an ice-free world to one that was extensively glaciated. Recently, however, this doctrine has been challenged, and an alternative hypothesis suggests the benthic delta/sup 18/O excursion primarily reflects a temperature drop within a previously glaciated world. Within the North Carolina continental margin, a chronostratigraphic framework consisting of 6 discrete early Miocene depositional sequences was established via stratigraphic interpretations from over 21,000 Km of high-resolution seismic reflection profiles. Each sequence is bound by unconformities which were mapped throughout the continental margin. Biostratigraphic analyses of 140 vibracores penetrating these sequences demonstrate that each sequence is a consequence of 4th-order (10/sup 5/yrs) sea-level cyclicity, similar in duration (100-300 Ka) and amplitude (100-150 m) to the glacioeustatic sea-level fluctuations of the Quaternary Epoch. Recognition of late Burdigalian high-frequency (4th-order) sea-level cyclicity demonstrates that continental ice-sheets were large enough during the early Miocene to drive eustatic sea-level fluctuations with Milankovitch-type periodicities. This further supports Matthews (1984) hypothesis that continental ice-caps existed on Antarctica PRIOR to the well-documented middle Miocene benthic delta/sup 18/O global enrichment event.

Synder, S.W.; Synder, S.W.; Waters, V.J.; Steinmetz, J.C.; Hine, A.C.; Riggs, S.R.

1985-01-01

177

Regional biostratigraphy and paleoenvironmental history of Miocene of onshore and offshore Alabama  

SciTech Connect

Subsurface Miocene sediments of coastal Alabama and the adjoining state and federal waters consist of a clastic wedge varying in thickness from less than 1,000 ft in southern Alabama to a maximum of about 6,000 ft in the northeastern portion of the Main Pass area. Relatively deep-water and open-marine transgressive basal Miocene clays and shales unconformably overlie a gently southwestward-dipping late Oligocene-earliest Miocene carbonate platform. Middle and late Miocene sediments consist of a regressive offlapping sequence of sand and shale deposited in varying neritic paleoenvironments. Analysis of planktonic and benthonic foraminifera has resulted in a refined biostratigraphic zonation of these sediments, permitting the recognition of several regional time-equivalent datum levels, or biohorizons. These biohorizons are shown on a series of subsurface cross sections that show the dramatic southwestward thickening of middle and late Miocene sediments as well as illustrate the relationships of the producing intervals within the Cibicides carstensi and Discorbis 12 interval zones. The paleoenvironmental history of the Miocene has been reconstructed on a series of paleobathymetric maps drawn for selected regional biohorizons. Among other features, these maps have proven the existence and outlined the margins of previously unrecognized shallow-meritic deltaic sediments in southeastern Mobile County and in the Chandeleur and Viosca Knoll (north) areas. Analysis of sedimentation rates, which range from less than 25 to 1,370 ft/m.y., further aids in understanding the coastal shelf, deltaic, and open-marine depositional history of the Miocene of Alabama and the adjoining state and federal waters.

Smith, C.C. (Geological Survey of Alabama, Tuscaloosa (USA))

1989-09-01

178

Miocene ungulates and terrestrial primary productivity: Where have all the browsers gone?  

PubMed Central

Progressive changes are observed in both the composition of mammal faunas and vegetation during the Miocene epoch [24–5 mega-annum (Ma)]. These changes are usually interpreted as a response to climatic changes. In the traditional view, forests or woodlands gradually gave way to more open habitats, with grazing (grass-eating) ungulate (hoofed) mammal species replacing the browsing (leafy-vegetation-eating) species as grasslands expanded. However, data from fossil assemblages in the Great Plains region of North America show that this faunal change was not a one-for-one replacement of browsers by grazers, as usually thought. Typical late early Miocene (17 Ma) fossil communities included extraordinarily high numbers of browsing ungulate species, comprising a fauna that cannot be directly analogized with any present-day community. Both maximum species richness of all ungulates and the proportion of browsers declined steadily in ungulate communities through the middle Miocene, to levels comparable to those of the present by the late Miocene. The resulting dramatic, cumulative loss of browsing species constitutes one of the strongest faunal signals of the late Tertiary (but was not a single “event”). We suggest that the early Miocene browser-rich communities may reflect higher levels of primary productivity in Miocene vegetation, compared with equivalent present-day vegetation types. The observed decline in species richness may represent a gradual decline in primary productivity, which would be consistent with one current hypothesis of a mid-Miocene decrease in atmospheric CO2 concentrations from higher mid-Cenozoic values. PMID:10884422

Janis, Christine M.; Damuth, John; Theodor, Jessica M.

2000-01-01

179

Miocene fluvial-tidal sedimentation in a residual forearc basin of the Northeastern Pacific Rim: Cook Inlet, Alaska case study  

SciTech Connect

Cook Inlet in southern Alaska represents a Cenozoic residual forearc basin in a convergent continental margin, where the Pacific Plate is being subducted beneath the North American Plate. This basin accumulated the >6,700-m-thick, mainly nonmarine, Eocene-Pliocene Kenai Group. These rocks contain biogenic coal-bed methane estimated to be as high as 245 TCF. Lignites to subbituminous coals with subsurface R{sub o} ranging from 0.38 to 0.73 percent and the stage of clay-mineral diagenesis and expandibility indicate a thermally {open_quotes}cool{close_quotes} basin. Miocene Tyonek and Beluga Formations compose 65 percent (>4,300 m thick) of the Kenai Group. The Tyonek includes conglomeratic sandstones, siltstones, mudstones, coals, and carbonaceous shales, interpreted as braided- stream deposits. These fluvial deposits are interbecided with burrowed, lenticular, and flaser-bedded sandstones, siltstones, and mudstones, interpreted as tidal deposits. Tyonek framework conglomerates formed in wet alluvial fans incised on paleovalleys of the Chugach terrane. Coal-forming mires are well developed on abandoned braided-stream deposits. Tyonek drainages formed in high-gradient alluvial plains inundated by tides similar to environments in the modern upper Cook Inlet. The upper Miocene Beluga consists of sandstones, siltstones, mudstones, carbonaceous shales, and coals deposited in meandering (low sinuosity) and anastomosed fluvial systems. These fluvial deposits alternated vertically with deposits of coal-forming mires. The Beluga drainages formed in low-gradient alluvial plains. The high-gradient Tyonek alluvial plain was probably controlled by provenance uplift and eustatic change, whereas the low-gradient Beluga alluvial plain was influenced by subdued provenance uplift and rapid basin subsidence. Rapid sedimentation on both these low- and high-gradient alluvial plains, which kept up with subsidence, produced a thermally {open_quotes}cool{close_quotes} basin.

Stricker, G.D.; Flores, R.M. [Geological Survey, Denver, CO (United States)

1996-12-31

180

Miocene Coral Skeleton Rare Earth Element Patterns Reflect River Discharge  

NASA Astrophysics Data System (ADS)

Rare Earth Element (REE) patterns of modern coral skeletons usually reflect the REE composition of ambient seawater which is characterized by heavy REE enriched relative to light REE with NASC (North American Shale Composite) normalized La/Lu ratios of typically <0.4. The REE concentration in coral aragonite is enriched by 3 to 4 orders of magnitude compared to ambient seawater. Here we report trace element data including REE of coral skeletons of Late Miocene age (~9 Ma, Tortonian) from Crete (Eastern Mediterranean). Analyses were done using a 213 nm Nd:YAG laser coupled to an Element2 ICP-MS along the growth axis of the coral skeletons. The profiles show that Ba/Ca ratios have a seasonally induced pattern with high values around the winter months which are identified by ?18O analyses. REE/Ca ratios co-vary with Ba/Ca ratios. Since the Ba/Ca ratio is a proxy used to monitor river discharge, the co-variation suggests the REE/Ca ratio to be a proxy of comparable quality. NASC-normalized REE patterns of the Tortonian corals have negative Ce anomalies like modern corals. However, the Tortonian corals have REE patterns highly enriched in LREE with (La/Lu)N ratios of 4 to 30 which is 1 to 2 orders of magnitude higher compared to modern corals. Al concentrations are low (<10 ppm) and do not correlate with REE concentrations indicating an insignificant fraction of terrigenous material included in the skeleton. Applying distribution coefficients typical for modern corals, the REE composition of the Tortonian ambient water yields (La/Lu)N of about 2 to 16. This range can be explained by binary mixing of modern Eastern Mediterranean sea surface water ((La/Lu)N=0.35, sea surface salinity (SSS) ~38 ‰) with highly LREE-enriched river water ((La/Lu)N >3, salinity ~0.5 ‰) transporting suspended and colloid phases, also highly enriched, especially in LREE, at a ratio of ~9 (seawater):1 (river water). The river water component is considered because paleoenvironmental reconstructions suggest the reef to have grown close to a river mouth. The calculated mixing ratio corresponds to a SSS of the ambient water >34 ‰ compatible with environmental conditions favorable for coral growth. As possible sources of the REE transported by river water, weathering products of Cretan hinterland rocks must be considered. During the Miocene, drained hinterland was formed by a diversity of magmatic, metamorphic and sedimentary lithologies, essentially represented by granitoids, ophiolitic rocks, siliciclastic sediments and carbonates. A detailed identification of sources as well as quantification of corresponding fractions of REE contributing to the bulk river water component is principally possible in cases where the drained system shows a more limited variation in rock lithologies, however, is difficult to apply to the complex Cretan situation. This study demonstrates that the REE patterns of coral skeletons can be suitable to reconstruct the bulk REE composition of the drainage system in the reef’s hinterland. Also, we suggest to use REE/Ca and Ba/Ca ratios likewise in order to identify fluctuations in river discharge to marine environments.

Mertz-Kraus, R.; Brachert, T. C.; Jochum, K. P.

2010-12-01

181

Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension  

NASA Astrophysics Data System (ADS)

Post-Miocene extension in Central Anatolia; It's linkage to Aegean extension Anatolian Plate, -where Central Anatolia situated on-, escapes westward onto African plate along Eastern Mediterranean-Cyprus subduction zone, sliding by North and East Anatolian faults. Central Anatolia is bounded by dextral North Anatolian Fault from north, Taurides from south and it is fragmented by strike slip faults evolving under N-S compression in east and by Aegean horst and grabens evolving under N-S extension in west. To be able to delineate and understand the deformational order in Central Anatolia and its linkage to Aegean region, various sectors with the Anatolia are chosen, namely, Ankara region (Beypazar? to Kazan Miocene basins), Eski?ehir region (Mihall?ç?k to ?nönü Miocene basins) in Central Anatolia, Gediz-Ala?ehir Graben and Efes areas in Western Anatolia are selected. To sum up, in a wide region from Central Anatolia to Western Anatolia, i. Unconformities btw uppermost Late Miocene and Plio-Quaternary, and btw Plio-Quaternary and Quaternary are clearly identified in both regions, ii) ENE-WSW to N-S compression (intense post-Late Miocene - pre-Pliocene folding) with almost E-W extension operates during post-Miocene (during Pliocene) is followed by a short lived strike slip deformation during Early Pliocene, and finally by NW-SE to WNW-ESE oriented multi directional extension during post-Plio-Quaternary. And in Gediz-Ala?ehir Graben and Efes (western Anatolia); a continuous NNE-SSW to NE-SW multi directed extension since post-Late Miocene following almost N-S compression (post-Early Miocene) operated. Dextral strike slip faulting with normal components and normal faulting with right lateral strike slip components are recorded on same fault planes, iii) Quaternary normal faulting post dates folding, reverse and strike slip faulting in both regions. However, right lateral strike slip faulting is recorded to the NW tip of the normal faults like Efes, Manisa and Eski?ehir faults, iv) under the new kinematic findings, the boundary conditions of neotectonic domains should have to be redefined in Anatolian plate, and v) during the escape of Anatolian plate towards east-southeast, based on the shift of principal stress directions counterclockwise block rotations can be operated along the "microplates" where northern blocks of the "microplates" are downthrown. Key words: normal faulting, extension, neotectonic domains, post-Miocene, central Anatolia.

Rojay, Bora; Özsay?n, Erman

2013-04-01

182

Tectonic implications of early Miocene volcanic rocks, San Joaquin basin  

SciTech Connect

The early Miocene (22 Ma) Tecuya volcanic rocks of the San Emigdio Mountains were erupted during a regional episode of crustal extension in coastal California. These rocks are correlative with similar rocks in outcrops and the subsurface over at least 800 kmz in the southern San Joaquin basin. Initial dacitic eruptions produced laterally continuous subaerial to submarine pyroclastic flows. These facies rapidly buried alluvial fan deposits of the lower Tecuya Formation and marine sandstone of the Temblor Formation farther west. Following dacitic volcanism, massive basalt was deposited subaerially along the southeastern basin margin. Farther west, the basalt triples in thickness across synvolcanic, high-angle faults and consists of hyaloclastite and submarine basalt flows. Facies associations, thickness and tectural trends, and paleodispersal directions of the volcanic rocks were controlled by synvolcanic extensional faulting throughout the southern San Joaquin basin. The regional extent of these volcanic rocks provides an important chronostratigraphic marker and potential stratigraphic trap in a variety of depositional settings, from nonmarine to outer shelf and slope. Preliminary rare-earth element data indicate that both dacites and basalts exhibit LREE enrichment patterns. The {epsilon}{sub Nd}(O) values cluster around +3. Although these data are typical of island arc volcanic rocks, geological data clearly indicate that the Tecuya volcanic rocks were erupted in an extensional tectonic setting near the continental margin. Some other model, perhaps involving crustal contamination of magmas produced along the subducted East Pacific Rise, followed by syntectonic eruption along normal faults, is needed to explain this enigmatic combination of geochemical and geological data.

Cole, R.B.; Decelles, P.G. (Univ. of Rochester, NY (USA))

1990-05-01

183

Organic geochemical evaluations of bituminous rock and coals in Miocene Himmetoglu basin (Bolu, Turkey)  

SciTech Connect

The studied area is a lake basin located in Bolu basin in Turkey. In the basin, from Upper Cretaceous to Upper Miocene 3,000-m thickness sediments were deposited. Upper Miocene Himmetoglu formation consisted of sandstone, claystone, and marl. To the middle level of the formation are located coal, bituminous limestone, and bituminous shales. In the basin, there are two coal beds whose thicknesses range from 1 to 13 m. The coals are easily breakable and black in color. In the coal beds exists some bituminous limestone and bituminous shales, and their thicknesses are between 5 and 45 cm. The amount of organic matter of the bituminous rocks from the Upper Miocene Himmetoglu formation are between 6.83 and 56.34 wt%, and the amount of organic matter of the bituminous limestone from the formation are between 13.58 and 57.16 wt%. These values indicate that these rocks have very good source potential. According to hydrogen index (HI), S2/S3, HI-T{sub max}, and HI-OI (oxygen index) parameters, kerogen types of the bituminous rocks and coals belonging to Upper Miocene Himmetoglu formation are Type I, Type II, and Type III. In accordance with HI, S2/S3, HI-T{sub max}, and HI-OI parameters, the bituminous rocks and coals from the Upper Miocene Himmetoglu formation are mostly immature.

Sari, A.; Geze, Y. [Ankara University, Ankara (Turkey). Faculty of Engineering

2008-07-01

184

Miocene-Pliocene transition in the southern Cyprus basins: The sedimentary expression of regional tectonic events  

SciTech Connect

In the southern part of Cyprus, a Maastrichtian-Pleistocene sedimentary area fringes Troodos Mountain, a fragment of an ancient crust. During the Neogene, three basins formed in this area: Polemi, Pissouri, and Psematismenos. A deep marine condition has prevailed since the Maastrichtian. During the Paleocene and early Miocene, the sea gradually become shallower until the Messinian, where the most spectacular sedimentary event concerns the deposition of evaporites contemporaneous with other Mediterranean evaporites. Some sedimentary phenomena express the tectonic instability during the upper Miocene. A well-known tectonic event affecting the east Mediterranean region generally referred to as the Miocene-Pliocene phase occurs at the Miocene-Pliocene limit. Recent sedimentological studies indicate this event is in fact complex. The Tortonian-lower Pliocene period is marked by a constraint involving an N20 distension in the Polemi and Pissouri basins and an N100 distension in the Psematismenos basin. Sedimentologic studies have demonstrated three tectonic pulsations during the Messinian prior to the Pliocene transgression. These are expressed by two episodes of seismic brecciation and a paleoemersion indicated by paleosols and detrital discharges. These phenomena suggest brief tectonic instability during the Messinian. Microtectonic studies reveal that the main change in tectonic constraint does not coincide with the Miocene-Pliocene contact but occurs at the top of the lower Pliocene.

Orzag-Sperber, F.; Rouchy, J.M. (Universite Paris XI, Orsay (France))

1988-08-01

185

Distribution history and climatic controls of the Late Miocene Pikermian chronofauna  

PubMed Central

The Late Miocene development of faunas and environments in western Eurasia is well known, but the climatic and environmental processes that controlled its details are incompletely understood. Here we map the rise and fall of the classic Pikermian fossil mammal chronofauna between 12 and 4.2 Ma, using genus-level faunal similarity between localities. To directly relate land mammal community evolution to environmental change, we use the hypsodonty paleoprecipitation proxy and paleoclimate modeling. The geographic distribution of faunal similarity and paleoprecipitation in successive timeslices shows the development of the open biome that favored the evolution and spread of the open-habitat adapted large mammal lineages. In the climate model run, this corresponds to a decrease in precipitation over its core area south of the Paratethys Sea. The process began in the latest Middle Miocene and climaxed in the medial Late Miocene, about 7–8 million years ago. The geographic range of the Pikermian chronofauna contracted in the latest Miocene, a time of increasing summer drought and regional differentiation of habitats in Eastern Europe and Southwestern Asia. Its demise at the Miocene-Pliocene boundary coincides with an environmental reversal toward increased humidity and forestation, changes inevitably detrimental to open-adapted, wide-ranging large mammals. PMID:19571012

Eronen, Jussi T.; Ataabadi, Majid Mirzaie; Micheels, Arne; Karme, Aleksis; Bernor, Raymond L.; Fortelius, Mikael

2009-01-01

186

Mineralogy and diagenesis of miocene and pleistocene sediments, Northeastern Gulf of Mexico  

SciTech Connect

Cored Miocene and Pleistocene sediments from the northeastern Gulf of Mexico (ranging in depth from 1,400 to 2,000 m) consist of interbedded sands, silts, and muds with varying degrees of consolidation. Samples selected from these sediments were studied for their mineralogy and diagenesis. The Miocene sediments represent various subenvironments of the ancestral Mississippi River delta complex; Pleistocene sediments are marine shelf deposits. Sands from both Miocene and Pleistocene cores are fine to very fine-grained feldspathic litharenites with abundant (approx. = 25%) matrix fines and minor (<7%) carbonate clasts and shell fragments. Carbonate diagenesis is a continuing process in these sediments. Clayey sands contain disseminated siderite crystallites formed during organic matter fermentation. In clean sands, scattered thin (<15 cm) bands of poikilotopic carbonate-cemented sand are present in the middle of thicker unconsolidated intervals. Cemented bands are thicker in the Miocene section, having grown during burial through dissolution of shell fragments and reprecipitation at the margin of cemented zones. Diagenetic events evident in the Miocene core illustrate processes that could occur in the Pleistocene sediments with continued burial. These are: (1) dolomitization of some calcite cements, (2) precipitation of Fe-carbonate as crystallites, rims on dolomite cements, and overgrowths on siderite crystallites, and (3) zeolite formation on amorphous silica substrates. Amorphous silica is associated with limited dissolution of feldspars or lithic fragments.

Conner, S.P.; Denham, M.E.; Tieh, T.T.

1988-01-01

187

Reflections on the Hawthorne Effect  

ERIC Educational Resources Information Center

When researchers carry out an experiment, they do so in a systematic and regulated manner, attempting to note all of the circumstances and outcomes very carefully, so that they can come to some firm conclusions about causes and effects. Sometimes, however, unaccountable outcomes do occur. Researchers are clearly very interested in such events and…

Merrett, Frank

2006-01-01

188

An interview of Geoffrey Hawthorn  

E-print Network

Scrubs and that is the last I saw of him; my mother then lived on her own until she died ten years ago in local authority housing, a very sad unsatisfactory life for her; the one thing that she did feel as a result of her own experience was that education... ; by sixteen-seventeen there were girls, then university ? 17:50:09 I remember reading very intensively and rereading, particularly nineteenth and twentieth century poetry; I loved the language, music and imagery; for a child who was a dreamer it was wonderful...

Hawthorn, Geoffrey

2009-04-23

189

A new Early/Middle Miocene mammal locality from Macedonia, Greece  

NASA Astrophysics Data System (ADS)

A new fossiliferous locality with macro- and micro-mammals was found near the village of Agios Antonios, about 26 km southeast of Thessaloniki, Macedonia, Greece. The fossils are recovered from the fissure fillings of the karstified Mesozoic limestones of the basement. The fissures were filled in and covered by the clastic sediments of Antonios Fm, representing the first Neogene deposits of the Axios-Thermaikos Neogene palaeobasin. The age of the fauna indicates a time span from the end of the Early Miocene to the beginning of the Middle Miocene (upper part of MN 4 to lower part of MN 5). The deposition of Antonios Fm must have started during or a little earlier than the end of the Early Miocene, and consequently the Neogene Axios-Thermaikos palaeobasin was created during this time or a little earlier.

Koufos, George D.; Syrides, George E.

1997-10-01

190

The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems  

PubMed Central

The Miocene is characterized by a series of key climatic events that led to the founding of the late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments, and particularly the role of atmospheric CO2 as a forcing factor, are poorly understood. Here we present a CO2 record based on stomatal frequency data from multiple tree species. Our data show striking CO2 fluctuations of ?600–300 parts per million by volume (ppmv). Periods of low CO2 are contemporaneous with major glaciations, whereas elevated CO2 of 500 ppmv coincides with the climatic optimum in the Miocene. Our data point to a long-term coupling between atmospheric CO2 and climate. Major changes in Miocene terrestrial ecosystems, such as the expansion of grasslands and radiations among terrestrial herbivores such as horses, can be linked to these marked fluctuations in CO2. PMID:18174330

Kürschner, Wolfram M.; Kva?ek, Zlatko; Dilcher, David L.

2008-01-01

191

Ramu basin, Papua New Guinea: A record of late Miocene terrane collision  

SciTech Connect

The Ramu basin lies along a plate boundary where the Finisterre terrane is colliding with the Indo-Australian plate. Estimates for the age of initial collision range from early Miocene to middle Pliocene. Two unsuccessful wells (Keram 1 and Tsumba 1) drilled to basement and two-dimensional seismic data show that folded and faulted early to middle Miocene carbonates and clastics (the Wogamush sequence) are overlain by relatively undeformed Pliocene marine clastics (the Wewak sequence) along a regional unconformity. The pre-Pliocene section, which is at the crux of resolving the age of initial collision, has been correlated previously to the Finisterre terrane. Clastics within that section, derived from older terranes south of the basin, imply an early Miocene age for collision. I propose that Miocene sedimentary and volcanic rocks in the two wells are correlative with the Wogamush beds of the Maramuni arc. The Ramu basin can then be viewed as having a two-stage evolution. During the Miocene, the basin was part of the Maramuni arc, the polarity of which is unresolved. A collisional successor basin developed in the late Miocene as the Finisterre terrane (Adelbert block) collided with the arc. Thrust faults on the northeastern side of the basin, truncated by a regional unconformity, are interpreted to mark the suture of the Adelbert block. A northern earliest Pliocene sediment source for the basal Wewak sequence was probably the Finisterre terrane, but multiple source areas are inferred for the rest of that sequence. Middle Pliocene inversion of the basin`s northeastern flank, characterized by reverse faulting and forced folding, is attributed to plate boundary reorganization caused by rifting in the Bismarck Sea. The Ramu basin has numerous untested structures related to both collision and basin inversion. Gas-prone source rocks are present, but are largely immature. Reservoir and charge considerations place the Ramu basin in the very high risk sector for exploration.

Cullen, A.B. [Univ. of Oklahoma, Norman, OK (United States)

1996-05-01

192

Architecture and growth history of a Miocene carbonate platform from 3D seismic reflection data; Luconia province, offshore Sarawak, Malaysia  

Microsoft Academic Search

Using 3D seismic reflection data and wireline logs we reconstruct in detail the architecture and growth history of a Miocene carbonate platform in the Luconia province, offshore Sarawak, Malaysia. Platform growth started in the Late Oligocene to Early Miocene, by coalescence of isolated patch reefs. The growth history includes phases of progradation, backstepping and occasional collapsing of platform flanks, guided

Valentina Zampetti; Wolfgang Schlager; Jan-Henk van Konijnenburg; Arnout-Jan Everts

2004-01-01

193

A NEW LATE MIOCENE SPECIES OF PARACOLOBUS AND OTHER CERCOPITHECOIDEA (MAMMALIA: PRIMATES) FOSSILS FROM LEMUDONG'O, KENYA  

Microsoft Academic Search

The Colobinae (Mammalia: Primates) are relatively unknown from the middle to late Miocene of eastern Africa. When they appear in the Pliocene fossil record they are unambiguous and fairly diverse taxonomically, geographically, and ecologically. The primate fauna from the late Miocene of Lemudong'o is dominated by colobines and therefore represents one of the richest fossil assemblages yet published of this

LESLEA J. HLUSKO

194

Miocene and Pliocene dominated diversification of the lichen-forming fungal genus Melanohalea (Parmeliaceae, Ascomycota) and Pleistocene population expansions  

PubMed Central

Background Factors promoting diversification in lichen symbioses remain largely unexplored. While Pleistocene events have been important for driving diversification and affecting distributions in many groups, recent estimates suggest that major radiations within some genera in the largest clade of macrolichens (Parmeliaceae, Ascomycota) vastly predate the Pleistocene. To better understand the temporal placement and sequence of diversification events in lichens, we estimated divergence times in a common lichen-forming fungal genus, Melanohalea, in the Northern Hemisphere. Divergence times were estimated using both concatenated gene tree and coalescent-based multilocus species tree approaches to assess the temporal context of major radiation events within Melanohalea. In order to complement our understanding of processes impacting genetic differentiation, we also evaluated the effects of Pleistocene glacial cycles on population demographics of distinct Melanohalea lineages, differing in reproductive strategies. Results We found that divergence estimates, from both concatenated gene tree and coalescent-based multilocus species tree approaches, suggest that diversification within Melanohalea occurred predominantly during the Miocene and Pliocene, although estimated of divergence times differed by up to 8.3 million years between the two methods. These results indicate that, in some cases, taxonomically diagnostic characters may be maintained among divergent lineages for millions of years. In other cases, similar phenotypic characters among non-sister taxa, including reproductive strategies, suggest the potential for convergent evolution due to similar selective pressures among distinct lineages. Our analyses provide evidence of population expansions predating the last glacial maximum in the sampled lineages. These results suggest that Pleistocene glaciations were not inherently unfavorable or restrictive for some Melanohalea species, albeit with apparently different demographic histories between sexually and vegetatively reproducing lineages. Conclusions Our results contribute to the understanding of how major changes during the Miocene and Pliocene have been important in promoting diversification within common lichen-forming fungi in the northern Hemisphere. Additionally, we provide evidence that glacial oscillations have influenced current population structure of broadly distributed lichenized fungal species throughout the Holarctic. PMID:22963132

2012-01-01

195

Paleomagnetic Study of a Miocene Deformation in a Region Close to the Camargo Volcanic Field, Chihuahua, Mexico  

NASA Astrophysics Data System (ADS)

The Sierra the Aguachile is a Miocene volcanic sequence located in the SE of Chihuahua State NW of the Camargo volcanic field and belongs to the Agua Mayo Group, which unconformably overlays Mesozoic calcareous units. The Sierra de Aguachile sequence defines a structure that may be interpreted as a plunging fold, which could be the result of a reactivation of the San Marcos Fault. This major fault is well known more to the east but may extend into the study area where it would be covered by the younger volcanic sequences; its main activity has been reported to be during the the Neocomian with reactivation phases in the Paleogene and Miocene. To test if the observed structure is the result of a tectonic deformation that happened after the emplacement of the volcanic sequence, a paleomagnetic study was carried out. A total of 14 sites were sampled from different parts of the structure, all in the capping ignimbrite layers. Site mean directions were determined using AF demagnetization. The fold test was applied to analyze if the remanence was acquired in situ or before the proposed folding. Precision parameters k before and after application of the tectonic corrections are 25.38 and 31.43, respectively. This indicates that the Sierra de Aguachile indeed was folded after emplacement of the ignimbrites, which restricts the age of the corresponding tectonic event to be younger than 31.3 +/- 0.7 Ma. Due to the gentle folding though, the difference in precision parameters is not significant at the 95% probability level.

Wogau-Chong, K.; Bohnel, H.; Aranda Gomez, J.

2009-05-01

196

Stratigraphical investigations on a new Miocene fossil-bearing sequence in Central Inner Mongolia, China  

NASA Astrophysics Data System (ADS)

Central Inner Mongolia has been an area of great paleontological interest since the beginning of the 20th century. Although the area has produced numerous diverse collections of Miocene faunas, fossil records from the early Miocene of Inner Mongolia are relatively rare. The localities occur mainly as scattered faunal horizons and their stratigraphy is challenging owing to lack of continuous vertical exposures. Consequently, most age estimations of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently based on paleomagnetics. The Damiao site in Siziwang Qi, Inner Mongolia, was discovered in 2006, and during the following four years extensive field activities were undertaken. The focus was on paleontological studies and on the stratigraphy of the Neogene sediments. The field survey led to the recovery of approximately 30 new fossiliferous localities, which have produced a rich mammalian fauna, including pliopithecid remains. The bulk of the vertebrate fossils and localities have been recovered from three main fossil horizons. We have interpreted the Damiao sequence as the remains of a fluvio-lacustrine system comprising channels, subaerially exposed floodplains and ephemeral/marginal lacustrine environments. This study presents the litho- and magnetostratigraphy of the Damiao area and provides age estimations for the important fossil-bearing localities. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with important vertebrate fossil localities. The western section is about 30 m thick and includes fossil locality DM16 while the eastern section spans up 40 m and comprises localities DM01 and DM02. The paleomagnetic results and faunal evidence suggest a correlation in the magnetozones C6Ar through C5r with an age range of ca 21 to 11 Ma. The interval of reversed polarity at the base of the section (C6Ar) coincides with fossil locality DM16. The pliopithecid locality DM01 represents late middle Miocene and has an age estimate of about 12 Ma while the locality DM02 represents earliest late Miocene with an age estimate of about 11.6- 11.7 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the most continuous sequences in Inner Mongolia with early, middle and late Miocene fossil faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmenal evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests relatively humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for Central Asia since Early Miocene.

Kaakinen, Anu; Aziz, Hayfaa Abdul; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Krijgsman, Wout; Fortelius, Mikael

2014-05-01

197

A radiolarian dated sponge microsclere assemblage from the Miocene Dos Bocas Formation of Ecuador  

NASA Astrophysics Data System (ADS)

An assemblage of siliceous sponge microscleres, previously unknown in the fossil record, are described from the Miocene Dos Bocas Formation of coastal Ecuador. The fauna includes several species previously known only from Holocene faunas, and a new taxa Conciliaspongia rarus Gen. et sp. nov. The microsclere assemblage is interpreted as being deposited in close proximity to a shallow (< 25 m) reef area, representing a transition between the localized San Pedro Member and the basin-wide facies of the Dos Bocas Formation. Radiolaria occurring in association with the microsclere assemblage indicate a mid-Early Miocene age ( Stichocorys delmontensis zone), and illustrate their biostratigraphic usefulness in enigmatic/exotic facies.

Robinson, P. D.; Haslett, S. K.

1995-04-01

198

Miocene Blanca Fan, Northern Channel Islands, California: Small fans reflecting tectonism and volcanism  

USGS Publications Warehouse

Blanca fan is a submarine fan composed of Miocene volcaniclastic strata. Parts of the fan system are exposed on Santa Cruz and Santa Rosa Islands, and possibly correlative strata crop out on San Miguel and Santa Catalina Islands. The Blanca fan and underlying breccia reflect regional transcurrent faulting in the California Continental Borderland and development of a system of rapidly subsiding basins and uplifted linear ridges during early and middle Miocene time. Erosion of uplifted crystalline basement rocks followed by the onset of silicic volcanism created linear sediment sources for the alluvial and submarine fans, respectively. ?? 1984 Springer-Verlag New York Inc.

McLean, H.; Howell, D. G.

1984-01-01

199

The Miocene Sommières basin, SE France: Bioclastic carbonates in a tide-dominated depositional system  

NASA Astrophysics Data System (ADS)

The Miocene Sommières Basin in SE France is a semi-enclosed depression that was connected to the Mediterranean Sea by a flooded paleo-incised valley and then filled by a suite of sediments comprising carbonate grains coming from temperate factories that were largely deposited in tidal-dominated paleoenvironments. The strata are partitioned into two sequences that reflect repeated flooding of the incised valley system, one of several similar situations in this region of France. The carbonate grains are mostly bioclasts, namely from barnacles, bryozoans, coralline algae (encrusting, branching, and rhodoliths), echinoids, and benthic foraminifers (large and small) with ostracods, sponge spicules and planktic foraminifers prominent in muddy facies. Particles were produced by shallow water carbonate factories on hard substrates (valley walls in particular), associated with subaqueous dunes, and in deeper water basinal settings. Each depositional sequence is underlain by an eroded and bored hard surface that is progressively overlain by TST subaqueous tidal dunes or storm deposits that grade up, in one case, into HST marls (the HST of the upper sequence has been removed by erosion). The lower sequence is ebb tide dominated whereas the upper sequence is flood tide dominated. The succession is interpreted to represent a TST whose tidal currents were focused by the narrow valley and a HST that reflected flooding of the overbanks. This stratigraphic and depositional motif is comparable to that in other spatially separated Neogene paleovalleys that are filled with tide-dominated clastic carbonates in the region. Together with other recently documented similar systems, these limestones constitute an important new group of carbonate sand bodies in the carbonate depositional realm.

Reynaud, Jean-Yves; James, Noël P.

2012-12-01

200

Magnetostratigraphy and depositional history of the Miocene Wushan basin on the NE Tibetan plateau, China: Implications for middle Miocene tectonics of the West Qinling fault zone  

Microsoft Academic Search

Based on field mapping, section measurement and magnetostratigraphy, ?1700m of sedimentary rocks have accumulated in the Wushan basin between ?16Ma and ?6Ma. Basin geometry, sedimentation characteristics and the early syn-depositional deformation along the northern margin of the basin indicate that formation of the Wushan basin was related to tectonic deformation along the West Qinling fault zone during the middle Miocene.

Zhicai Wang; Peizhen Zhang; Carmala N. Garzione; Richard O. Lease; Guangliang Zhang; Dewen Zheng; Brian Hough; Daoyang Yuan; Chuanyou Li; Jianhui Liu; Qinglong Wu

201

Mediterranean proto-sapropels in the Middle Miocene: implications for the strength of the African monsoon and link to Miocene glaciations  

NASA Astrophysics Data System (ADS)

The strength of the African monsoon is known to have played a major role in determining sedimentation patterns in the Mediterranean during the Plio-Pleistocene. Increased meteoric water input by strong monsoons reduced surface water salinity, and the resulting slower water-mixing rate triggered the deposition of organic-rich layers called "sapropels". Here we present some proxy data coming from a mixed siliciclastic-carbonate section outcropping on the Maltese Islands that suggests that sapropels deposits already existed in the Middle Miocene. This implies that an enhanced monsoonal climate was likely active at that time. Our primary evidences for the existence of "proto-sapropels" are runoff proxies (clay mineral assemblages and abundance) coupled with oxygen isotopes. These indicate that a direct link existed between increased runoff regarded here as a proxy for the strength of the Monsoon- and Miocene global climate (Antarctic glaciation). Each Miocene phase of glaciation is reflected in the section as an increased flux of continental-derived material. Moreover, stable isotopes of carbon and Corg:Norg ratio analyses of organic matter revealed a higher mixing rate of terrigenous and marine organic matters during times of increased sedimentation. This is in good agreement with a monsoon model where increased sedimentation is linked to increased continental runoff. Spectral analysis of the section revealed the presence of Milankovitch-scaled cycles with a strong 100 k.y. frequency. Astronomically calibrated age model for the section shows that the African monsoon has probably initiated around 16.7 Ma and underwent a major strengthening around 13.8 Ma, a time corresponding to enhanced siliciclastic deposition on the Malta-Ragusa platform and to the global cooling phase of the Mi3 Antarctic ice-buildup phase. We argue that the strong coherence between Miocene glaciation phases and increased runoff into the Mediterranean is due to a link between Antarctic cooling, Northward migration of the ITCZ due to increased thermal gradient, and enhances precipitation over North Africa.

John, C. M.; Mutti, M.; Adatte, T.; Laskar, J.

2003-04-01

202

Diagenetic gypsum related to sulfur deposits in evaporites (Libros Gypsum, Miocene, NE Spain)  

NASA Astrophysics Data System (ADS)

The Libros Gypsum is the thickest evaporite unit of the Miocene infill of the Teruel Basin in NE Spain. During the deposition of this unit, intense bacterial sulfate-reducing (BSR) activity in the lake depocenter generated a native sulfur deposit. Diagenetic gypsum resulted from subsequent sulfur oxidation. The different processes involved in these transformations were first investigated by Anadón et al. (1992). The present paper is concerned with this diagenetic gypsum from the stratigraphic, petrographic, isotopic and genetic points of view. Diagenetic gypsum occurs mainly as continuous or discontinuous layers, individual levels or lenses, irregular masses, nodules and micronodules, and veins. Its main textures are coarse-crystalline anhedral and fine-grained (alabastrine), both of which can replace any former lithology (carbonate, gypsum, and sulfur). The following sequence of processes and mineral/textural transformations is deduced: primary gypsum deposition — BSR and biodiagenetic carbonate/H 2S production — growth of native sulfur — growth of diagenetic gypsum — partial recrystallization of the diagenetic gypsum textures. The gypsification of the native sulfur generated two types of banded structures in the diagenetic gypsum: (1) concentric structures of centripetal growth, and (2) expansive, roughly concentric structures. In the first type, the gypsification operated from the outer boundaries towards the inner parts. In the second type, part of the carbonate hosting the sulfur was also gypsified (replaced/cemented). In the diagenetic gypsum, the ?34S values are in agreement with a native sulfur and H 2S provenance. The ?18O sulfate values, however, enable us to differentiate two main groups of values: one with positive values and the other with negative values. In the group of positive values, interstitial (evaporated) solutions participated in the sulfur oxidation; this process presumably occurred in a first oxidation stage during shallow-to-deeper burial of the Libros Gypsum unit. In the group of negative values, however, only meteoric waters participated in the oxidation, which presumably occurred in a second oxidation stage during the final exhumation of the unit. A third group of values is characterized by very high sulfur and oxygen values, suggesting that BSR residual solutions also participated in the oxidation processes locally. During the two oxidation stages, both the textural characteristics and the isotopic composition of the diagenetic gypsum indicate that gypsification operated as a multistadic process.

Ortí, Federico; Rosell, Laura; Anadón, Pere

2010-07-01

203

High-resolution record of Early to Middle Miocene climate variability from Site 1195, Marion Plateau, NE Queensland margin  

NASA Astrophysics Data System (ADS)

Constraining and quantifying eustatic variations has been a priority for stratigraphers since the publication of the first global sea level curves by the Exxon research group in the late 1970s. Quantifying the glacio-eustatic component of sea level signals has become a greater focus as more recent work has demonstrated that far-field effects like ice-sheet gravitation and isostasy imprint on the "true" eustatic signal of waxing and waning ice sheets so that coeval signals from disparate sites may show significantly different local sea level variations. To this end, the Miocene sediments on the Marion Plateau, a drowned carbonate platform on the Queensland margin of Australia, were drilled by ODP Leg 194 to provide an independent, southern hemisphere test of the sea level record of the New Jersey Margin of North America, the most complete and oft-cited record of Cenozoic sea level variability. A high-resolution record is critical to compare sea level variations across hemispheres. Natural Gamma Ray (NGR) logs of core holes can provide a complete, high-resolution record independent of any problems with core recovery or sampling interval. We here present a NGR record of ODP Site 1195 tied to recently completed nannofossil assemblage data, planktic/benthic foraminiferal ratios, sedimentary particle counts, and benthic foraminifera stable isotopes. Peaks in glauconite and clay content correspond to peaks in NGR. The largest of these peaks correspond to sequence boundaries (lowstands), as glauconite accumulates during periods of low sedimentation along this carbonate-dominated margin. These sequence boundaries, in turn, are each associated with marine oxygen isotope events ("Mi Events") and correlate to sequences on the New Jersey margin, the Gulf of Papua, Great Australian Bight, and McMurdo Sound, indicating that these sequences are eustatically controlled. Although sedimentary particle counts only show strong peaks of glauconite at sequence boundaries, the NGR record shows long-period, low-amplitude variations in NGR between 20 and 18 Ma, a time corresponding to a pre-platform muddy ramp, short-period, high-amplitude variations between 18 and 14.8 Ma, a period of higher sea levels during the Miocene Climatic Optimum (MCO) and a dramatic spike corresponding to Mi3a at 14.8 Ma during the Middle Miocene Climate Transition (MMCT) followed by a slow decrease in the amplitude and frequency of variation during subsequent Antarctic ice growth and the drowning of the Marion Plateau. The variations in the NGR profile correspond directly (at a higher resolution) to variations in the oxygen isotope record, allowing us to create a cyclostratigraphic record that reflects fluctuations in oxygen isotopes. Calcareous nannofossil populations respond to variations in surface water nutrient availability and temperature; these changes coincide with climatic events of the early Miocene, including the MCO, the MMCT and the stepwise formation of ice sheets on Antarctica (<13.6 Ma). Calcareous nannofossil data show evidence for significantly cooler surface water at the Marion Plateau coinciding with the end of the MCO.

Lowery, C.; Browning, E.; Leckie, R. M.; John, C. M.

2012-12-01

204

ORIGINAL PAPER Late Miocene to Pleistocene potassic volcanism  

E-print Network

groups may be distinguished. The first group has a shoshonitic affinity and occurs in the Kozuf Massif Province type" affinity (Group III of Foley, Venturelli, Green, Toscani, Earth Sci Rev 24:81­134, 1987 related to the opposite propagation of extension in the Aegean and Pannonian basins (respectively SW

Doglioni, Carlo

205

Isotopic and molecular characteristics of Miocene-reservoired oils of the Kutei Basin, Indonesia  

Microsoft Academic Search

Thirty-two oils reservoired in Miocene sands of the Kutei Basin of Indonesia have been examined isotopically and molecularly for the purposes of determining source-defined families and estimating the depositional and compositional characteristics of their source rocks. The oil set is geographically distributed within, north, east, and south of the Mahakam River delta, and comprises oils from wells drilled onshore, on

J. Curiale; R. Lin; J. Decker

2005-01-01

206

Age and paleo-oceanographic significance of silica-carbonate cycles in Miocene Monterey Formation, California  

Microsoft Academic Search

Middle Miocene Monterey Formation cherts are often cyclically interbedded with laminated dolomites. Their co-occurrence is paradoxical because cherts are produced in relatively cold water, whereas dolomite is associated with warm water. Chert and dolomite intervals generally have poor age control, which has hindered further paleo-oceanographic interpretations. Examination of diatom assemblages that are well preserved in the dolomites has resulted in

Lisa D. White

1987-01-01

207

Paleoecology of middle and late Miocene Monterey Formation, Upper Newport Bay, Newport Beach, California  

Microsoft Academic Search

The Miocene Monterey Formation exposed along the cliffs of Upper Newport Bay represents a lower calcareous facies dominated by foraminifera and coccoliths, indicating warm climate and low nutrient waters, and a siliceous facies consisting of diatomaceous rocks, which records high productivity as a result of climatic deterioration and intensified upwelling. Using the distribution and preservation of foraminifera in the California

A. P. Carlos; R. G. Douglas

1986-01-01

208

Trace fossils in diatomaceous strata of Miocene Monterey Formation: their character and implications  

Microsoft Academic Search

Younger parts of the Miocene Monterey Formation are commonly characterized by relatively unaltered diatomaceous strata. A common characteristic of these deposits is the preservation of varvelike lamination, indicative of deposition under anoxic or nearly anoxic conditions. Although laminated rock types are volumetrically dominant, bioturbated intervals are by no means rare, but little attention has been paid to the trace fossils

C. E. Savdra; D. J. Bottjer

1986-01-01

209

Palynology of the Monterey formation (Miocene) phosphatic facies at Lions head, Santa Maria area, California  

Microsoft Academic Search

A rich palynomorph assemblage of early Miocene age was obtained from the phosphatic facies mudstone samples of the lower Monterey Formation exposed in the basal Lions Head section in the Santa Maria area, California. Angiosperm pollen of Acer, Achillea, Bombacaceae, Carya, Ericaceae, Onagraceae, Salix, and Ulmus occurs commonly. Among conifers, bisaccate Pinus pollen is well represented. Azolla glochidia and spores

Satish K. Srivastava

1984-01-01

210

Miocene Glacioeustasy and Carbonate Sequences on the Marion Plateau, Northeastern Australia: Inferences from Distal Slope Records  

Microsoft Academic Search

Understanding the timing and magnitude of eustatic changes (global sea-level) is key to improving sequence stratigraphic and sedimentologic models, with wide implications for environmental changes and future exploration of fossil fuels. In the Oligo-Miocene, the magnitude of eustatic changes also provides a clue on Antarctic ice volume. The current best eustatic curve is largely based on records from the New

C. M. John; E. Browning; M. Leckie; G. Karner

2008-01-01

211

OligoceneMiocene middle crustal flow in southern Tibet: geochronology of Mabja Dome  

E-print Network

Oligocene­Miocene middle crustal flow in southern Tibet: geochronology of Mabja Dome J. LEE1 , W ages provide constraints on the timing of formation and exhumation of the Mabja Dome, southern Tibet of middle crustal rocks in southern Tibet. Zircons from a deformed leucocratic dyke swarm yield a U­Pb age

Lee, Jeff

212

A re-examination of Palaeostruthus hatcheri (Shufeldt), a late Miocene sparrow from kansas  

Microsoft Academic Search

Palaeostruthus hatcheri (Shufeldt), from the late Miocene (late Clarendonian-early Hemphillian) Long Island local fauna, Kansas, is the oldest recorded species of Emberizidae. The holotype and only specimen of P. hatcheri is a complete rostrum which, upon re-examination, is seen to be extremely similar to that of Ammodramus savannarum, the living grasshopper sparrow. Therefore, the genus Palaeostruthus Wetmore is synonymized with

David W. Steadman

1981-01-01

213

New fossil crocodilians from the Middle\\/Upper Miocene of Tunisia  

Microsoft Academic Search

New crocodilian material from the Beglia Formation (Middle\\/Upper Miocene) of Tunisia, although fragmentary, is reported. However, due to its fragmentary nature very little can be said about its affinities, and only the genus Euthecodon can be identified with certainty.

Eduardo Llinas Agrasar

2003-01-01

214

Original article A new fossil bee from the Oligo-Miocene  

E-print Network

Original article A new fossil bee from the Oligo-Miocene Dominican amber (Hymenoptera 19 February 1997; accepted 11 April 1997) Summary — A new species of fossil bee, Oligochlora the Dominican Republic. The genus Oligochlora is not represented among the modern fauna and was originally based

Paris-Sud XI, Université de

215

Evidence for sediment fan deposition on outer Texas shelf during Miocene eustatic sea level highstands  

SciTech Connect

Four types of data were reviewed in an attempt to clearly define the environments of deposition for reservoir sands in the Matagorda 668 field: well log curve shapes, seismic amplitude responses, micropaleontology, and thin section sedimentary petrology. All four lines of evidence support the interpretation that these lower Miocene sands were deposited as fan complexes.

Riese, W.C.; Olsen, R.S.; Rosen, R.N.

1988-02-01

216

A remarkable new pygmy grasshopper (Orthoptera, Tetrigidae) in Miocene amber from the Dominican Republic  

PubMed Central

Abstract A new genus and species of pygmy grasshopper (Orthoptera: Tetrigidae) is described from Early Miocene (Burdigalian) Dominican amber. Electrotettix attenboroughi Heads & Thomas, gen. et sp. n. is assigned to the subfamily Cladonotinae based on the deeply forked frontal costa, but is remarkable for the presence of tegmina and hind wings, hitherto unknown in this subfamily. PMID:25147472

Heads, Sam W.; Thomas, M. Jared; Wang, Yinan

2014-01-01

217

New fossil discoveries from the Miocene of Nepal include a hominoid  

Microsoft Academic Search

We present here preliminary findings of recent field studies on Miocene Lower Siwaliks deposits of southwestern Nepal. Twenty-four vertebrate taxa are now represented from over 50 localities. The fauna is largely aquatic, being dominated by fish, turtles, crocodiles and aquatic snakes. Lithologies indicate deposition in sluggish streams and associated environments. Biostratigraphy indicates correlation between the composite Nepal fauna and Lower

Jens Munthe; Bishnu Dongol; J. Howard Hutchison; William F. Kean; Kathleen Munthe; Robert M. West

1983-01-01

218

Miocene sharks in the Kendeace and Grand Bay formations of Carriacou, The Grenadines, Lesser Antilles  

Microsoft Academic Search

The Miocene chondrichthyan fauna from the Kendeace and Grand Bay formations consists of five species which have been identified from the remains of teeth. These are Carcharias taurus (sand-tiger shark), Isurus oxyrinchus (shortfin mako shark), Carcharocles megalodon (mega-tooth shark), Carcharhinus obscurus (requiem shark) and Hemipristis serra (extinct snaggletooth shark). No further skeletal fish remains, Chondrichthyes or Actinopterygii, were discovered. Teeth

ROGER W. PORTELL; G ORDON HUBBELL; S TEPHEN K. DONOVAN; J EREMY L. GREEN; DAVID A. T. HARPER; RON PICKERILL

219

The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru  

Microsoft Academic Search

The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid

Olivier Lambert; Giovanni Bianucci; Klaas Post; Christian de Muizon; Rodolfo Salas-Gismondi; Mario Urbina; Jelle Reumer

2010-01-01

220

Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama  

E-print Network

Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama Catalina that the extinct Carcharocles megalodon was the biggest shark that ever lived. Previous proposed paleo by fossil marine mammals. We now present the first definitive evidence of ancient nurseries for C. megalodon

Bermingham, Eldredge

221

The development of the Amazonian mega-wetland (Miocene; Brazil, Colombia, Peru, Bolivia)  

Microsoft Academic Search

The scenery of Western Amazonia once consisted of fluvial systems that originated on the Amazonian Craton and were directed towards the sub-Andean zone and the Caribbean. In the course of the Early Miocene these fluvial systems were largely replaced by lakes, swamps, tidal channels and marginal marine embayments, forming a mega-wetland. In this chapter we will review the characteristics of

C. Hoorn; F. P. Wesselingh; J. Hovikoski; J. Guerrero

2010-01-01

222

Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula  

Microsoft Academic Search

Before the formation of the Central American Isthmus, there was a Central American Peninsula. Here we show that southern Central America existed as a peninsula as early as 19 Ma, based on new lithostratigraphic, biostratigraphic and strontium chemostratigraphic analyses of the formations exposed along the Gaillard Cut of the Panama Canal. Land mammals found in the Miocene Cucaracha Formation have

Michael Xavier Kirby; Douglas S. Jones; Bruce J. MacFadden

2008-01-01

223

A new kentriodontid dolphin (Cetacea; Delphinoidea) from the middle Miocene Choptank Formation, Maryland  

Microsoft Academic Search

A new odontocete genus and species, Macrokentriodon morani, is described from the middle Miocene Choptank Formation of Maryland. This specimen consists of the skull, periotic, and teeth of a single individual. It is placed in the Family Kentriodontidae and the Subfamily Kentriodontinae based on the morphology of the cranial vertex, which is unique to kentriodontines, and features of the periotic.

Susan D. Dawson

1996-01-01

224

Trace fossils on penguin bones from the Miocene of Chubut, southern Argentina  

Microsoft Academic Search

Several traces of biological interaction were found on penguin bones from the basal levels (Aquitanian) of the Miocene Gaiman Formation in the lower Chubut valley of the Provincia del Chubut, Argentina. The fossil-bearing beds were deposited in littoral to sublittoral environments within sediments of mostly pyroclastic origin. We interpret many traces to have been produced by predators and\\/or scavengers while

Alberto Luis Cione; Carolina Acosta Hospitaleche; Leandro Martín Pérez; Jose Herminio Laza; Inés César

2010-01-01

225

Syn-tectonic sedimentary evolution of the Miocene atallar Basin, southwestern Turkey  

E-print Network

farther to the north (Lycian Nappes) or to the east (Antalya Nappes). The origin of these ophiolitic: Sedimentology; Biostratigraphy; Source of detritals; Miocene; Basin analyses; Lycian Nappes 1. Introduction In southwestern Turkey, two sets of nappes are thrust over the Bey Dalari carbonate platform: the Lycian Nappes

Boyer, Edmond

226

Ross sea region in the middle miocene: a glimpse into the past.  

PubMed

Fossil diatoms and pollen from sea-floor sediments beneath the Ross Ice Shelf indicate that a permanent ice cover was not present in the Ross Sea and that vegetation including angiosperms, gymnosperms, and ferns existed on at least some parts of the largely glaciated Antarctic mainland in the late middle Miocene. PMID:17734135

Brady, H; Martin, H

1979-02-01

227

Pliocene and latest Miocene anisotropy of magnetic susceptibility (AMS) from the Wilkes Land margin (Invited)  

NASA Astrophysics Data System (ADS)

During IODP Expedition 318, Sites U1359 and U1361 were drilled on the continental rise offshore the Wilkes Subglacial Basin to reconstruct the stability of the East Antarctic Ice Sheet (EAIS) during Neogene warm periods, such as the late Miocene and the early Pliocene. As the drilled core contains a complex history of compaction, erosion (thus hiatuses), and likely artificial disturbances, identifying these is important for reconstructing paleoenvironments. Anisotropy of magnetic susceptibility (AMS) is sensitive to lithological changes and differential compaction. At both sites, highly anisotropic layers correspond with turbidite units, lithologic boundaries and hiatuses. In places, it appears that low anisotropy is controlled by the bioturbated units and high productivity layers. Here we present a detailed study of the relationships between sediment compaction, based on AMS fabric variations in sedimentary records, and magnetic mineralogy. A clear correlation can be found between the degree of anisotropy and moisture content and diatom abundance during the Pliocene, but this pattern breaks down in the late Miocene. There are also strong rock magnetic indications for changes in the sources of the magnetic minerals throughout the Miocene to Pliocene. Furthermore, a significant difference exists between magnetic minerals at Sites U1359 and U1361. We will use our AMS and rock magnetic study to 1) characterize sediment compaction with biological productivity, and 2) detect the source of magnetic mineralogy throughout the late Miocene to Pliocene at both sites.

Sugisaki, S.; Tauxe, L.; Iwai, M.; van de Flierdt, T.; Cook, C.; Jimenez, F. J.; Khim, B.; Patterson, M. 0; Mckay, R. M.; Passchier, S.; Roehl, U.; González, J. J.; Escutia, C.

2013-12-01

228

Paleomagnetic quantification of upper-plate deformation during Miocene detachment faulting in the Mohave Mountains, Arizona  

Microsoft Academic Search

Paleomagnetic data from Miocene (?20 Ma) volcanic rocks and dikes of west central Arizona reveal the tilt history of Proterozoic crystalline rocks in the hanging wall of the Chemehuevi-Whipple Mountains detachment fault. We obtained magnetization data from dikes and flows in two structural blocks encompassing Crossman Peak and Standard Wash in the Mohave Mountains. In the Crossman block the dike

V. Pease; J. W. Hillhouse; R. E. Wells

2005-01-01

229

American Journal of Botany 84(8): 981991. 1997. FOSSIL MUSHROOMS FROM MIOCENE AND CRETACEOUS  

E-print Network

981 American Journal of Botany 84(8): 981­991. 1997. FOSSIL MUSHROOMS FROM MIOCENE AND CRETACEOUS Two species of fossil mushrooms that are similar to extant Tricholomataceae are described from to hypotheses that the cosmopolitan distributions of certain mushroom taxa could be due to fragmentation

Hibbett, David S.

230

Late Miocene and Pliocene large land mammals and climatic changes in Eurasia  

Microsoft Academic Search

The fossil teeth of land mammals offer a powerful tool to map the regional details of past climate change in the terrestrial realm. We use mean plant-eater hypsodonty (molar crown height) of late Neogene mammal localities to map late Miocene and Pliocene palaeoprecipitation on the Eurasian continent and, with higher temporal resolution, in Europe. The results show that the mid-latitude

Mikael Fortelius; Jussi Eronen; Liping Liu; Diana Pushkina; Alexey Tesakov; Inesa Vislobokova; Zhaoqun Zhang

2006-01-01

231

Miocene stable isotope record: a detailed deep Pacific Ocean study and its paleoclimatic implications  

SciTech Connect

Deep Sea Drilling Project site 289 in the western equatorial Pacific has yielded an extremely detailed record of the carbon and oxygen isotopic changes in the Miocene deep ocean. The isotopic record reflects major changes in paleoclimate and paleoceanography, probably dominated by a major phase of Antarctic ice-cap growth.

Woodruff, F. (Univ. of Southern California, Los Angeles); Savin, S.M.; Douglas, R.G.

1981-05-08

232

Detrital geochronology and geochemistry of CretaceousEarly Miocene strata of Nepal: implications for timing and  

E-print Network

Detrital geochronology and geochemistry of Cretaceous­Early Miocene strata of Nepal: implications of the southern Lesser Himalayan zone of central Nepal. The Cretaceous­ Paleocene(?) Amile Formation is dominated documented by the U­Pb zircon ages. The fact that middle Eocene strata in Nepal were derived from

Najman, Yani

233

Miocene faulting at plate tectonic velocity in the Himalaya of central Nepal  

E-print Network

Miocene faulting at plate tectonic velocity in the Himalaya of central Nepal Matthew J. Kohna, Tri-Chandra Campus, Ghantaghar, Kathmandu, Nepal, United States Received 7 April 2004; received (MCT) and affiliated faults in central Nepal. Inferred rates were 1.5F0.9 cm/yr (Langtang Thrust, ~19

234

Paleomagnetic data bearing on style of Miocene deformation in the Lake Mead area, southern Nevada  

Microsoft Academic Search

Paleomagnetic and structural data from intermediate to mafic composition lava flows and related dikes in all major blocks of the late Miocene Hamblin–Cleopatra Volcano, which was structurally dismembered during the development of the Lake Mead Fault System (LMFS), provide limits on the magnitude and sense of tilting and vertical axis rotation of crust during extension of this part of the

Tim F Wawrzyniec; John W Geissman; R. Ernest Anderson; Steve S Harlan; James Faulds

2001-01-01

235

Miocene vegetation pattern and climate change in the northwestern Central Paratethys domain (Czech and Slovak Republic)  

NASA Astrophysics Data System (ADS)

The case study area covers the slopes of the tectonically quiet European platform and foreland of the tectonically active Carpathian mountain chain (Carpathian Foredeep and Vienna Basin). Therefore the research on pollen spectra mirrors not only the evolution of landscape in two areas with different geodynamics, but also climatic changes in the Central Paratethys domain during the studied time interval. According to the pollen data, the Early to Middle Miocene vegetation reflects subtropical climate with very mild (negligible) cooling events during this period. This is indicated by common occurrence of thermophilous taxa in the whole sedimentary record. The Middle Miocene landscape evolution, conditioned by uplift of the Carpathian mountain chain and subsidence of adjacent lowlands, led to commencement of the altitudinal zonation. The terrestrial and aquatic ecosystems confirm a subtropical climate (Miocene Climatic Optimum, Mi3 event) with some possible long term changes in humidity. The Late Miocene paleogeographical changes, but also general climatic oscillations in the northwestern Central Paratethys realm, resulted in decrease of the number of thermophilous taxa during this time (change in latitudinal position of the vegetation cover). Variously high mountain relief of the uplifted mountain chains (altitudinal zonality) created ideal conditions for mixed mesophytic forests (to open woodland — open grassland type), still with presence of evergreen taxa. A subtropical climate with gradual transition to warm temperate climatic conditions is supposed on the basis of the reconstructed vegetation cover.

Ková?ová, Marianna; Doláková, Nela; Ková?, Michal

2011-06-01

236

Ocean Circulation and Gateway Closures During the Late Miocene (~13-5 Ma)  

Microsoft Academic Search

Long-term climate change is driven by tectonic influences, including changes in ocean circulation that are the result of ocean gateway closure. During the middle to late Miocene (~13-5 Ma), both tropical ocean circulation and deep water production were reorganized due to the increasing constriction of the Indonesian and Central American seaways. For example, the waters of the modern Pacific equatorial

S. A. Nathan; R. M. Leckie

2004-01-01

237

Miocene -Quaternary tectonic evolution of the northern eastern California shear zone  

E-print Network

in California and Nevada: tectonics, stratigraphy and hydrogeology: Pacific Section, SEPM (Society173 1 Miocene - Quaternary tectonic evolution of the northern eastern California shear zone Kurt L the eastern California shear zone. This field trip includes 12 stops focused on the active tectonics

Lee, Jeff

238

Tectonic control on past circulation of the Mediterranean Sea: A model study of the Late Miocene  

Microsoft Academic Search

We examine the effect of Late Miocene paleogeography on the circulation and water properties of the Mediterranean Sea by using an ocean circulation model. Results obtained for the past are compared to a control experiment with the present-day geometry. To focus on paleogeography, atmospheric forcing is always based on the present-day climatology. We seek insight that allows us to test

P. Th. Meijer; R. Slingerland; M. J. R. Wortel

2004-01-01

239

MEDITERRANEAN AND PARATETHYS. FACTS AND HYPOTHESES OF AN OLIGOCENE TO MIOCENE PALEOGEOGRAPHY (SHORT OVERVIEW)  

Microsoft Academic Search

Paleogeographical considerations on the development of the Paratethys and the Mediterranean during Oligocene and Miocene are presented in twelve time-slices. Plate tectonic activities and the collision of India with Asia caused the destruction of the Western Tethys Ocean in the Late Eocene. The Mediterranean and the intracontinental Paratethys basins came into existence as new marine realms. In the Mediterranean Basin

FRED R ÷ GL

240

Middle Miocene exhumation of the Laji Shan, Northeastern Tibetan Plateau  

NASA Astrophysics Data System (ADS)

New data from northeastern Tibet uplift and associated basin tectonic evolution provides constraints on the mechanics of plateau growth and tectonic/climate interactions related to the aridification of central Asia and the intensification of the east Asian and Indian monsoons. Evolution of the large Longzhong Basin - including the Xining, Lanzhou, Linxia, Gonghe and Guide sub-basins - is well-constrained by recent advances in magnetostratigraphic dating of climatic and tectonic records. In particular, aridification is associated to global cooling at the Eocene-Oligocene transtion 34 yrs ago (see Hoorn et al., this meeting, Session T17), and tectonic activity is associated to widespread clockwise rotations of paleomagnetic directions at ca. 41 Ma and 17-11 Ma (see Dai et al., this meeting, Session GP12). However, poorly constrained thermal histories in adjacent fault- bounded ranges make linkages between tectonic, exhumation/sedimentation and climate tentative. We present here preliminary apatite (U-Th)/He and Fission track (FT) ages from the Laji Shan, a mountain range presently separating the Guide-Gonghe basins from the Xining-Linxia-Lanzhou basins. Sampling was performed at three elevation profiles (MD, LJ and TG;) in plutonic rocks from 2068 m to 4114 m. (U-Th)/He results from the lower elevation profile MD transect indicate fast exhumation between 14 Ma to 8 Ma, while the higher elevation profiles LJ and TG results indicate widespread ages from 40 to 110 Ma typical of partial retention zone. Obtained apatite FT dates of the MD elevation profile range from 16 to 35 Ma and all samples have long Mean Tracks Lengths (MTL) indicating fast cooling through the partial annealing zone for all samples. There is a clear correlation between elevation and FT date. The data indicate that a fossil partial zone has been uplifted. The sample at the lowest elevation (2068 m) with an apatite FT age of 16.2 Ma has the highest MTL suggesting that rock uplift of some 6 km has taken place since 16 My ago, assuming a geothermal gradient of 25°C/km. Obtained apatite FT datesof the LJ elevation profile cluster around 60 ± 10 Ma and do not differ much over the entire sampled elevation range. MTL are shorter for samples from the high elevation part of the profile, compared to longer MTL from the lowest samples. This is interpreted in reflecting a fossil partial annealing zone that has been uplifted since 55 My ago, as indicated by the sample with the longest MTL of 14 ? and FT age of 52.4 Ma. The total amount of rock uplift since that time amount to 6-7 km (assuming 25°C/km). Obtained apatite FT dates from the TG elevation profile cluster around 130 ± 10 Ma. The FT data reveal a fast cooling of the rocks around 160-170 Ma ago and all samples seem to have passes through the partial annealing zone in a similar way, suggesting a continuous exhumation of the rocks. Taken together these data suggest that significant midlle Miocene (ca. 15 Ma) unroofing in the Laji Shan belt can be associated to compartmentalization of the large Longzhong basin with tectonic rotation and onset of sedimentation in the Gonghe-Guide basins.

Dupont-Nivet, G.; Andriessen, P.; Juez-Larre, J.; Foeken, J.; Jiang, X.

2007-12-01

241

Tracking Arabia-India motion from Miocene to Present  

NASA Astrophysics Data System (ADS)

Although small, the present-day Arabia-India motion has been captured by several global and regional geodetic surveys that consistently show dextral motion of a few mm/yr, either transpressive or transtensive (Fournier et al., 2008). This motion is accommodated along the Owen Fracture Zone, an active strike-slip boundary that runs for more than 700 km from the Somalia-India-Arabia triple junction in the south to the Dalrymple trough in the north. Two recent marine cruises conducted along this fault aboard the BHO Beautemps-Beaupré (AOC 2006 and OWEN 2009) using a high resolution multibeam sounder (Simrad EM120, 10 m vertical resolution) provided a complete map of the active fault and confirmed a present-day pure dextral motion. The surface breaks closely follow a small circle of the Arabia-India motion, with several pull-part basins at the junctions between the main segments of the fault. Geomorphologic offsets reach 10 km, suggesting that the mapped fault has been active with the same style for past several million years. When did this motion start? The difficulty in tracking the past Arabia-India motion is that there is no direct kinematic indicator available, since the boundary has been strike-slip and/or convergent during the Tertiary. Motion was most probably sinistral during the rapid northward travelling of India towards Eurasia in the early Tertiary, Arabia being rigidly attached to Africa until the opening of the Gulf of Aden. However, the nature and location of the Arabia-India boundary at that time remain speculative. Throughout the Miocene, the relative motion between India and Arabia has been indirectly recorded at the Sheba and Carslberg ridges, the former recording Arabia-Somalia motion (opening of the Gulf of Aden) and the latter India-Somalia motion (Indian Ocean opening). Both ridges have been studied with some details recently, using up to date magnetic lineations identification (Merkouriev and DeMets, 2006; Fournier et al., 2009). We combine these studies to derive Arabia/India kinematics for the past 20 Myrs. As observed today, opening rates at Sheba ridge and at Carlsberg ridge remained closed since Chron 5D (17.2 Ma), thus pointing to small differential motion between Arabia and India. However, our kinematic model suggests that dextral shearing prevailed since the very beginning of opening of the Gulf of Aden. This has significant implications for the forces that drive the Arabia plate and Arabia-India coupling at their transform boundary. Fournier et al., 2008, In-situ evidence for dextral active motion at the Arabia-India plate boundary, Nature Geoscience, doi:10.1038/ngeo.2007.24. Fournier et al., 2009, Arabia-Somalia plate kinematics, evolution of the Aden-Owen-Carlsberg triple junction, and opening of the Gulf of Aden, J. Geophys. Res., in revision. Merkouriev and DeMets, 2006, Constraints on Indian plate motion since 20 Ma from dense Russian magnetic data: Implications for Indian plate dynamics, Geochem. Geophys. Geosyst., doi:10.1029/2005GC001079.

Chamot-Rooke, N. R.; Fournier, M.

2009-12-01

242

Interim report on the ground-water resources of Manatee County, Florida  

USGS Publications Warehouse

Manatee County comprises an area of about 800 square miles adjacent to the Gulf of Mexico in the southwestern part of the Florida peninsula. The county is underlain at depths ranging from about 200 to 350 feet by a series of limestone formations of Tertiary age having a total thickness of several thousand feet. The upper part of the limestone section consists of the Ocala group of Eocene age, the Suwannee limestone of Oligocene age, and the Tampa formation of early Miocene age. These limestone formations are overlain by the Hawthorn formation of middle Miocene age which consists of interbedded clay, limestone, and sand. The Hawthorn is overlain by undifferentiated deposits of sand, limestone, and shell of Pliocene(?) and Pleistocene age that range in thickness from a few feet to about 75 feet.

Peek, Harry M.; Anders, Robert B.

1955-01-01

243

Late Miocene to Pleistocene potassic volcanism in the Republic of Macedonia  

NASA Astrophysics Data System (ADS)

The potassic (K) to ultrapotassic (UK) volcanic rocks cropping out in the Vardar Zone of Macedonia and southern Serbia span in age from Late Miocene (6.57 ??) to Pleistocene (1.47 ??). The main identified outcrops are in the Kumanovo, Sveti Nikole, Shtip and Demir Kapia areas; the southernmost occurrences of these volcanic rocks are located in the large Kozuf Massif (Voras Massif in Greece) at the Macedonia Greek border. Three distinct groups may be distinguished. The first group has a shoshonitic affinity and occurs in the Kozuf Massif (LMg-K group); it includes shoshonites to rare rhyolites, with latites and trachytes being the most widespread products. The second group consists of potassic rocks (HMg-K group, K2O/Na2O between 1.0 and 1.8) occurring in both southern Serbia (Cer and Slavujevci) and Macedonia (Djuristhe, near Sveti Nikole). The third group, present only in Macedonia, consists of ultrapotassic rocks (UK group, K2O/Na2O >1.8, Mg# >71) classified as UK shoshonites, UK latites and UK phonotephrites; overall, they show a “Roman Province type” affinity (Group III of Foley, Venturelli, Green, Toscani, Earth Sci Rev 24:81 134, 1987). Geochemically, the studied rocks exhibit strong enrichment in LILE, Th and Pb, as well as relative depletion in Ta Nb and Hf; such signatures are typical of magmas generated in convergent geotectonic settings. In the HMg-K and UK rocks, Sr and Nd isotopic ratios vary from 0.70768 to 0.71040, and 0.51243 to 0.512149, respectively. The rocks of the LMg-K group show relatively limited Sr and Nd isotope variations (0.7087 0.7093 and 0.51233 0.51229), which correlate with a decrease in MgO and increase in SiO2 contents. The geochemical features of the LMg-K volcanic rocks indicate that their evolution was mainly driven by fractional crystallization coupled with contamination by feldspar-rich crustal materials. In contrast, the HMg-K and UK rocks have not been significantly modified by crustal contamination, and their geochemical features are considered to reflect lithospheric mantle heterogeneity acquired during the subduction of the Western Vardar Ocean and the Apulian plate. The metasomatizing agent was apparently more enriched in Zr, Th, Ta and Ce than in fluid-mobile elements, such as Pb and Cs, suggesting that it was characterized by a high melt/fluid ratio. The potassic and ultrapotassic magmatic activity developed in response to the Pliocene Pleistocene extension in the Vardar Zone, in turn related to the opposite propagation of extension in the Aegean and Pannonian basins (respectively SW and NE).

Yanev, Yotzo; Boev, Blazo; Doglioni, Carlo; Innocenti, Fabrizio; Manetti, Piero; Pecskay, Zoltan; Tonarini, Sonia; D'Orazio, Massimo

2008-09-01

244

The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru.  

PubMed

The modern giant sperm whale Physeter macrocephalus, one of the largest known predators, preys upon cephalopods at great depths. Lacking a functional upper dentition, it relies on suction for catching its prey; in contrast, several smaller Miocene sperm whales (Physeteroidea) have been interpreted as raptorial (versus suction) feeders, analogous to the modern killer whale Orcinus orca. Whereas very large physeteroid teeth have been discovered in various Miocene localities, associated diagnostic cranial remains have not been found so far. Here we report the discovery of a new giant sperm whale from the Middle Miocene of Peru (approximately 12-13 million years ago), Leviathan melvillei, described on the basis of a skull with teeth and mandible. With a 3-m-long head, very large upper and lower teeth (maximum diameter and length of 12 cm and greater than 36 cm, respectively), robust jaws and a temporal fossa considerably larger than in Physeter, this stem physeteroid represents one of the largest raptorial predators and, to our knowledge, the biggest tetrapod bite ever found. The appearance of gigantic raptorial sperm whales in the fossil record coincides with a phase of diversification and size-range increase of the baleen-bearing mysticetes in the Miocene. We propose that Leviathan fed mostly on high-energy content medium-size baleen whales. As a top predator, together with the contemporaneous giant shark Carcharocles megalodon, it probably had a profound impact on the structuring of Miocene marine communities. The development of a vast supracranial basin in Leviathan, extending on the rostrum as in Physeter, might indicate the presence of an enlarged spermaceti organ in the former that is not associated with deep diving or obligatory suction feeding. PMID:20596020

Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle

2010-07-01

245

Paleogeographic and structural setting of Miocene strata in central western Nevada  

SciTech Connect

Late Cenozoic sedimentary rocks as old as 19 Ma are widely distributed in central western Nevada. They are greatly more abundant than older Cenozoic strata and are commonly interpreted to have formed in fault-bounded basins that mark the onset of widespread extension in the Basin and Range Province. Miocene strata are largely coeval with a magmatic arc that extended south southeast near the boundary of the Basin and Range and Sierra Nevada Provinces. This arc produced voluminous andesitic flows and lahars that locally interfinger with the Miocene strata. Miocene depositional basins apparently varied greatly in size. The largest that can be defined clearly is the Esmeralda Basin that was at least 65 km long and 45 km wide. Other basins may have been larger but are difficult to reconstruct; still other basins may be small and isolated, particularly within the magmatic arc. Lacustrine deposits and minor interfingering deltaic and distal fluvial units predominate; near-source, coarse alluvial-fan and megabreccia landslide deposits are locally conspicuous. coarse near-source deposits, particularly landslide deposits, are interpreted to be adjacent to basin-bounding normal faults. The Esmeralda, Coal Valley, and Gabbs Valley-Stewart Valley-Tonopah Basins are interpreted to be related to large-scale Miocene extension. Other basins may be (1) pull-apart structures related to strike-slip faults, (2) downdropped blocks in areas of cross-cutting normal and/or strike-slip faults related to changes in the extension direction or (3) grabens or half-grabens related to uniform extension. Younger Cenozoic basins, including present-day basins, overprint and cut across the Miocene basins.

Stewart, J.H. (Geological Survey, Menlo Park, CA (United States))

1993-04-01

246

Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records  

USGS Publications Warehouse

Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10??Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10??Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12??Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the No??rdlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum. ?? 2008 Elsevier B.V.

Klemm, V.; Frank, M.; Levasseur, S.; Halliday, A.N.; Hein, J.R.

2008-01-01

247

Style and age of late Oligocene-early Miocene deformation in the southern Stillwater Range, west central Nevada: Paleomagnetism, geochronology, and field relations  

USGS Publications Warehouse

Paleomagnetic and geochronologic data combined with geologic mapping tightly restrict the timing and character of a late Oligocene to early Miocene episode of large magnitude extension in the southern Stillwater Range and adjacent regions of west central Nevada. The southern Stillwater Range was the site of an Oligocene to early Miocene volcanic center comprising (1) 28.3 to 24.3 Ma intracaldera ash flow tuffs, lava flows, and subjacent plutons associated with three calderas, (2) 24.8 to 20.7 Ma postcaldera silicic dikes and domes, and (3) unconformably overlying 15.3 to 13.0 Ma dacite to basalt lava flows, plugs, and dikes. The caldera-related tuffs, lava flows, and plutons were tilted 60°-70° either west or east during the initial period of Cenozoic deformation that accommodated over 100% extension. Directions of remanent magnetization obtained from these extrusive and intrusive, caldera-related rocks are strongly deflected from an expected Miocene direction in senses appropriate for their tilt. A mean direction for these rocks after tilt correction, however, suggests that they were also affected by a moderate (33.4° ± 11.8°) component of counterclockwise vertical axis rotation. Paleomagnetic data indicate that the episode of large tilting occurred during emplacement of 24.8 to 20.7 Ma postcaldera dikes and domes. In detail, an apparent decrease in rotation with decreasing age of individual, isotopically dated bodies of the postcaldera group indicates that most tilting occurred between 24.4 and 24.2 Ma. The onset of tilting immediately following after the final caldera eruptions suggests that the magmatism and deformation were linked. Deformation was not driven by magma buoyancy, however, because tilting equally affected the caldera systems of different ages, including their plutonic roots. It is more likely that regional extension was focused in the southern Stillwater Range due to magmatic warming and reduction of tensile strength of the brittle crust. Faults that accommodated deformation in the southern Stillwater Range initially dipped steeply and cut deeply to expose more than 9 km of crustal section. The exposed crustal sections are probably rotated blocks above an unexposed basal detachment that lay near the early Miocene brittle-ductile transition.

Hudson, Mark R.; John, David A.; Conrad, James E.; McKee, Edwin H.

2000-01-01

248

Absolute magnitude of the second-order middle to late Miocene sea-level fall, Marion Plateau, northeast Australia  

SciTech Connect

The Miocene carbonate platform of the Marion Plateau in northeast Australia preserves an excellent record of sea-level fluctuations. The warm-water platform consists of an early to middle Miocene second-order highstand complex, whereas the late Miocene platform is a second-order lowstand complex. Analysis of the sea-level fall that led to this relation shows that the amplitude of this event was at least 180 m. Furthermore, the authors suggest a methodology for determining the amplitude of sea-level fluctuations based on measurement of sea-level falls in structurally simple parts of passive margins or in distal parts of foreland basins.

Pigram, C.J.; Davies, P.J.; Feary, D.A.; Symonds, P.A. (Bureau of Mineral Resources, Canberra (Australia))

1992-09-01

249

Tectonics or climate: What drove the Miocene global expansion of C4 grasslands?  

NASA Astrophysics Data System (ADS)

Investigations into the most plausible causes which triggered the Late Miocene global expansion of C4 grasslands have reached no consensus and are still being debated. The global decline in CO2 levels in the Late Miocene has been thought to be the most common driver. Although C4 grassland expansion was largely confined to the Late Miocene, their first appearance varied significantly in different parts of the Old and New world and therefore emphasizes role of local and/or regional factors may or may not be in combination with one or more global factors. The dynamic Himalayan orogen constitutes a significant global tectonic event that is believed to have affected global climate. Hence, a study of the Himalayan foreland basin sediments could help in gleaning out possible causes behind this major paleoecologic event, which could perhaps be directly or indirectly related. Stable carbon isotope analyses of a total of 141 pedogenic carbonates in the Mio-Pleistocene Siwalik paleosols of the Ramnagar sub-basin are coherent, providing a better insight into paleovegetational changes across the sub-basin on temporal and spatial scales. Furthermore, paleovegetational history during Oligocene is reconstructed from Dagshai paleosols exposed in the Subathu sub-basin. The isotopic results show dominance of C3 vegetation pre-7 Ma and dominance of C4 vegetation post-5 Ma. Percentage abundance of C4 vegetation was less than 20 % pre-7 Ma but increased to more than 40 % post-5 Ma, reaching up to 100 % in the youngest analyzed sediments. There is exclusive dominance of C3 vegetation during Oligocene. These results conform to the pattern of change in vegetation documented in other parts of the Himalayan belt. The global expansion of C4 grasslands largely during Late Miocene have long been linked with then climate changes, particularly brought by declining atmospheric CO2 level, large-scale fires, intensification of monsoon, seasonality, and aridity as demonstrated by various researchers. These major hypotheses explaining expansion of C4 grasslands during Late Miocene are not very convincing due to significant shortcomings associated with them, for example, expansion of C4 grasslands in non-monsoonal regions put serious constraints on the monsoonal intensification hypothesis. Likewise, aridity as being the primary driver of C4 grassland expansion seems hard to support since there is no substantial evidence that could suggest global onset of arid conditions at about same geologic time, and some most arid periods, like the Triassic, show no evidence of C4 plants. We suggest that the initial lowering of CO2 below 450 ppmV created an environment for the beginning of C4 vegetation, but the persistence of this threshold value for a considerable time during Late Miocene appears to be the probable cause of the Late Miocene global expansion of C4 grasslands irrespective of their time of first appearance. It has been deduced through the correlation of Himalayan tectonic events with atmospheric CO2 levels and paleovegetational changes since Upper Miocene times that it was indeed the Late Miocene continuous, intense tectonic instability of the Himalayas that significantly decreased atmospheric CO2 levels and which perhaps played a key role in changing the nature of photosynthetic pathways.

Singh, Seema; Awasthi, A. K.; Parkash, B.; Kumar, S.

2013-04-01

250

Highly extended terrains, lateral segmentation of the substratum, and basin development: The middle-late Miocene Radicondoli Basin (inner northern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

This paper deals with the evolution of sedimentary basins not delimited by normal faults, with a substratum characterized by an upward concave shape and with infilling sediments synclinally deformed. We describe the middle-late Miocene Radicondoli Basin, representing an example of such bowl-shaped basins. Its tectonic origin is controversial, being related both to compression and extension; these opposite interpretations bear significant consequences on the geodynamic context in which the inner northern Apennines developed during the middle-late Miocene. The results of our structural studies, carried out in the substratum and infilling sediments, indicate that the Radicondoli Basin is an example of a hanging wall basin developed in an extensional setting. Extensional tectonics determined the lateral segmentation of the substratum competent levels (i.e., Tuscan Nappe and Verrucano Group) and the consequent collapse of overlying less competent levels (i.e., the Ligurian units) with the formation of a bowl-shaped tectonic depression. Here, the syntectonic sediments (Serravallian-late Messinian) are deformed in a large syncline, characterized by minor gravity-driven folds, with vergences toward the depocenter and traces of their axial planes parallel to the basin margins. This paper highlights the role of the competence contrast during the postcollisional tectonic evolution and the influence of substratum lateral segmentation for the accommodation of syntectonic sediments.

Brogi, Andrea; Liotta, Domenico

2008-09-01

251

The antiquity of riverine adaptations in Iniidae (Cetacea, Odontoceti) documented by a humerus from the late Miocene of the Ituzaingó Formation, Argentina.  

PubMed

"River dolphins" are a paraphyletic group of toothed whales (Odontoceti) that represent independent secondary invasions of freshwater habitats. Different "river dolphin" lineages display suites of convergent morphological specializations that commonly reflect adaptations to riverine and freshwater environments, such as longirostry, reduced orbits, and wide, paddle-like flippers. One lineage, the Iniidae, is presently endemic to South America, and includes several extinct Neogene taxa along with their sole extant genus, Inia (the Amazon River dolphin). We report here a humerus recovered from the late Miocene deposits of the Ituzaingó Formation in the Paraná Basin of Argentina. The specimen exhibits diagnostic features of the family Iniidae, including a scapular-sternal joint of the humerus, which is a unique anatomical connection among mammals. This joint permits enhanced parasagittal adduction of the flipper as a control surface, relative to other odontocetes, providing Inia with a high degree of maneuverability in its structurally complex and heterogenous riverine habitat. This unique anatomical connection, here documented from the late Miocene (?9 million years-6.5 million years old), not only provides the oldest diagnostic record for Iniidae, but it also indicates a similar habitat use for this lineage, a finding coincident with the current paleoenvironmental interpretation for the Ituzaingó Formation. PMID:24585575

Gutstein, Carolina Simon; Cozzuol, Mario Alberto; Pyenson, Nicholas D

2014-06-01

252

Sedimentation/preservation of the Miocene Atacama Gravels in the Pedernales-Chaaral Area, Northern Chile: Climatic or Tectonic  

E-print Network

ignimbrites date the beginning of the Atacama Gravels sedimentation at around the Oligocene- Miocene boundary across different climate zones must be considered to explain north- south variations in tectonic style

Paris-Sud XI, Université de

253

A new fossil thryonomyid from the Late Miocene of the United Arab Emirates and the origin of African cane rats.  

PubMed

Cane rats (Thryonomyidae) are represented today by two species inhabiting sub-Saharan Africa. Their fossil record is predominately African, but includes several Miocene species from Arabia and continental Asia that represent dispersal events from Africa. For example, Paraulacodus indicus, known from the Miocene of Pakistan, is closely related to living Thryonomys. Here we describe a new thryonomyid, Protohummus dango, gen. et sp. nov., from the late Miocene Baynunah Formation of the United Arab Emirates. The new thryonomyid is less derived than "Thryonomys" asakomae from the latest Miocene of Ethiopia and clarifies the origin of crown Thryonomys and the evolutionary transition from Paraulacodus. A phylogenetic analysis shows Protohummus dango to be morphologically intermediate between Paraulacodus spp. and extinct and living Thryonomys spp. The morphological grade and phylogenetic position of Protohummus dango further supports previous biochronological estimates of the age of the Baynunah Formation (ca. 6-8 Ma). PMID:23625517

Kraatz, Brian P; Bibi, Faysal; Hill, Andrew; Beech, Mark

2013-05-01

254

Provenance of middle to late Miocene clastic sedimentary rocks in the central to eastern Cibao basin, northern Hispaniola  

E-print Network

by electron microprobe analysis indicate derivation from plutonic, metamorphic, and possibly volcanic sources. Trace elements and REE data demonstrate that the middle and late Miocene sediments in the central to eastern Cibao basin display two geochemically...

Yao, Meng

2012-06-07

255

A new species of long-necked turtle (Pleurodira: Chelidae: Chelodina) from the late Miocene Alcoota Local Fauna, Northern Territory, Australia  

PubMed Central

The new species Chelodina (Chelodina) murrayi is described from the late Miocene Alcoota Local Fauna of central Australia, in the Northern Territory. The new species is based on shell fragments and can be diagnosed by a ventrally reflexed anterior margin of the plastron, a ventrally narrowed cervical scute and strongly dorsally curved margins of the carapace extending from approximately peripheral two to peripheral nine or ten as well as by a unique combination of characters. Within Chelodina the new species is part of the nominal subgenus and within that subgenus it is most closely related to the Chelodina (Chelodina) novaeguineae species group. This is not only the oldest record but also the most southerly occurrence of this species group. PMID:24133635

2013-01-01

256

Miocene climate as recorded on slope carbonates : examples from Malta (Central Mediterranean) and Northeastern Australia (Marion Plateau, ODP LEG 194)  

Microsoft Academic Search

This study investigated the slope carbonates of two Miocene carbonate systems: the Maltese Islands (in the Central Mediterranean) and the Marion Plateau (Northeastern Australia, drilled during ODP Leg 194). The aim of the study was to trace the impact of the Miocene cooling steps (events Mi1-Mi6) in these carbonate systems, especially the Mi3 event, which took place around 13.6 Ma

Cédric Michaël John

2003-01-01

257

Seismic facies and growth history of Miocene carbonate platforms, Wonocolo Formation, North Madura area, East Java Basin, Indonesia  

E-print Network

SEISMIC FACIES AND GROWTH HISTORY OF MIOCENE CARBONATE PLATFORMS, WONOCOLO FORMATION, NORTH MADURA AREA, EAST JAVA BASIN, INDONESIA A Thesis by RAHADIAN ADHYAKSAWAN Submitted to the Office of Graduate Studies of Texas A&M University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 2002 Major Subject: Geophysics SEISMIC FACIES AND GROWTH HISTORY OF MIOCENE CARBONATE PLATFORMS, WONOCOLO FORMATION, NORTH MADURA AREA, EAST JAVA BASIN, INDONESIA...

Adhyaksawan, Rahadian

2012-06-07

258

Review of the fossil pufferfish genus Archaeotetraodon (Teleostei, Tetraodontidae), with description of three new taxa from the Miocene of Italy  

Microsoft Academic Search

Three new species of the extinct pufferfish genus Archaeotetraodon are described from the Middle to Upper Miocene of Italy (A. bannikovi nov. sp., A. dicarloi nov. sp. and A. zafaranai nov. sp.), and compared in detail with the three previously described taxa of the genus [A. jamestyleri (Bannikov), A. winterbottomi Tyler and Bannikov and A. cerrinaferoni Carnevale and Santini], which are known, respectively, from the Miocene

Giorgio Carnevale; James C. Tyler

2010-01-01

259

High-resolution ice-volume estimates for the early Miocene: Evidence for a dynamic ice sheet in Antarctica  

Microsoft Academic Search

Ice-volume estimates for the early Miocene (23–16 Ma ATS) were determined by applying ?18O to sea-level calibrations to high-resolution ?18O records from ODP Sites 1090 and 1218. These calibrated records indicate that ice-volume ranged between 50% and 125% of the present day East Antarctic Ice Sheet (EAIS) during most of the early Miocene (23–17 Ma). Maximum ice-volume occurred at each

Stephen F. Pekar; Robert M. DeConto

2006-01-01

260

Miocene strike-slip and normal fault controls on Au-Ag mineralization in the Talapoosa district, Lyon County, Nevada  

Microsoft Academic Search

Structurally controlled epithermal stockwork Au-Ag mineralization formed at the intersection of three complexly interacting fault sets in intermediate Miocene volcanic rocks at the Talapoosa District (TD) on the western margin of the Walker Lane during the mid.-late Miocene. The TD lies at the intersection of the N 75[degree] W Talapoosa-Gooseberry (T-G) lineament with the N 70[degree] E Carson River fault

P. A. Dilles; A. S. Carpenter

1993-01-01

261

Paleodietary reconstruction of Miocene faunas from Pa?alar, Turkey using stable carbon and oxygen isotopes of fossil tooth enamel  

Microsoft Academic Search

Miocene-age (? 15 Ma) deposits at Pa?alar in northwest Turkey contain abundant and well-preserved dental remains from a variety of herbivores. We used the carbon and oxygen isotopic compositions of inorganic carbonate in enamel from these teeth to reconstruct the paleodiet and sources of body water, respectively, of Miocene mammals. The ?13C (PDB) values of carbonate in the enamel fall

Jay Quade; Thure E. Cerling; Peter Andrews; Berna Alpagut

1995-01-01

262

Facies analysis of the Plateau Sandstones (Eocene to early Miocene?), Bako National Park, Sarawak, Malaysia  

NASA Astrophysics Data System (ADS)

Sandstones, located in the Kuching area, western Sarawak, are known as the 'Plateau Sandstones' (of possible Eocene to early Miocene age). However, based on a number of factors, including: (i) anomalous kerogene compositions; (ii) proximity of the on-lap surface; and (iii) palaeocurrent direction (generally to the NNE), it is thought that the sands exposed on the Bako Peninsula are unrelated to the Plateau Formation (located to the south of the Bako Penisula) and therefore a new name is coined; the Bako Sandstones, which form a subgroup of the Bako Sandstone Group. The Bako Sandstones form the Bako Peninsula, a flat-topped cliffed plateau which extends into the South China Sea at a latitude of 1°30'N. The plateau has a gently dipping surface, sloping northwards from a height of about 300 to 150 m. The sandstones form a succession of very thick bedded sandstones (up to 6 m thick), with lenses of conglomerates and subordinate sandy mudstones. The sandstones consist of pebbly coarse-medium grained sands, interbedded with polymictic pebble conglomerates. The sandstones are mainly lithic arenite, poorly to moderately sorted and consist of subangular to subrounded grains. Isolated pebbles are common throughout the sandstones. The most common structure in both sandstones and conglomerates is cross-bedding; planar cross-bedding and trough cross-bedding, together with thick sequences of climbing ripples. These structures suggest extensive tractional transport, forming both ripple and dune structures along the base of the channel. The geometry of the sands is either (i) lensoidal, or (ii) tabular, with the channel-fill interpreted as scour-fill channels or migrating dunes, respectively. Both types are commonly stacked vertically or amalgamate laterally to form thick interconnected units. The conglomeratic lenses, scour-fill features and rip-up shale clasts are related to higher energy erosional events, whilst the mud-draped ripples, ripple rejuvenation surfaces and two-tiered channel margins indicate a lower energy and stasis period. Slope instabilities at the channel margin are inferred from the slump structures present and shale clast slurries. The sandstones at Bako are thought to have formed within a braided channel environment (subject to exposure, from the presence of mud cracks within the formation).

Johansson, M.

1999-04-01

263

Palynology of the Heath Formation (Miocene) from the Progreso Basin, Peru  

SciTech Connect

A diverse and well preserved assemblage of pollen, spores, dinoflagellates, and acritarchs were recovered from outcrop samples of the Heath Formation, exposed along Bocapan Creek near Tumbes, Peru. The pollen and spores include representatives of Arecipites, Bombacacidites, Caryapollenites, Cicatricosisporites, Couperipollis, Cyathidites, Diporisporites, Distaverrusporites, Dyadosporites, Echiperiporites, Faramea, Foveodiporites, Foveotriletes, Fusiformisporites, Gothanipollis, Granitricolpites, Hymenophyllum, Hexpollenties, Involutisporites, Laevigatosporites, Lygodiumsporites, Magniperiporites, Malvacearumpollis, Monocolpopollenites, Perissyncolporites, Peritheciumites, Phragmothyrites, Polyadadporites, Polypodiaceisporites, Polypodiisporites, Retibrevitricolpites, Striadisporites, Tetracolporites, Tricolporopollenties, and Verrucosisporites. Plankton are assignable to Lejeunecysta, Operculodinium, Pterospermella, Selenopemphix, Spiniferites, Sumatradinium, Tythodiscus, and Tuberculodinium. The palynomorph assemblage can be placed in the Early Miocene based on the co-occurrence of Cicatricosisporites dorogensis, Couperipollis rarispinosus, Echiperiporites estelae, Magniperiporites echinatus, Perisyncolporites porkornii, Polypodiaceoisporites minor, P. potoniei, Reticolporites guianesnsis, R. irregularis, Scabriporites asymetricus, Selenopemphix nephroides and Tuberculodinium vancampoae. This is an agreement with foraminiferal evidence which positions the Heath Formation in the Early Miocene Catapsydrax dissimilis, Catapsydrax stainforthi and oldest portion of the Globigerinatella insueta zones.

Engelhardt, D.W. (Univ. of South Carolina, Columbia (United States)); Wood, G.D. (Amoco Production Co., Houston, TX (United States))

1993-02-01

264

Eocene to post-Miocene kinematic evolution of the central Cyclades (Greece)  

NASA Astrophysics Data System (ADS)

Due to the extraordinary geotectonic location of the Aegean above an active subduction zone and an exceptional high seismicity, this area and especially the Cyclades have been in the focus of structural investigations for several decades. The present deformation is the result of ongoing plate tectonic movements in this area since at least the Miocene. The ductile structures of the Miocene extension and related metamorphic core type deformation are quite well studied and understood. Equally well investigated are the active tectonic deformation and associated brittle structures through several decades of seismic records. However, due to the difficulties of dating brittle faults, the kinematic evolution from the early to middle Miocene ductile structures, to later Miocene brittle-ductile and brittle faults is much less understood. For these reasons detailed structural fieldwork, combined with Ar-Ar geochronology and P-T studies, have been carried out on the uninhabited island of Despotiko, SW of Antiparos, which is situated virtually in the center of the Cycladic islands. This island has been selected because the existence of metamorphic rocks penetrated by Messinian rhyolite pipes and Pleistocene eolianites provide exceptional age constraints for Eocene to post-Miocene deformation structures. Despotiko is part of lower structural levels of the polymetamorphic Blueschist Unit of the Attic-Cycladic Metamorphic Belt and correlated lithologically with the Parikia gneisses and Marathi unit of Paros. Foliation is shallowly dipping towards the SSW. The main lithologies of the island, from the footwall to the hanging wall, consist of dark to pale grey, strongly foliated, mylonitic granite gneiss with abundant pegmatite dikes. The gneiss is overlain by prominent white, strongly foliated, mylonitic gneiss. Above are medium-grained, white calcite marble followed by greenish-white, mylonitic gneiss and an alternation of mica schist, greenschist, thin marble layers and some small serpentinite lenses. The structurally highest levels, in the south and southwest of the island, comprise several tens of meters of dolomite marble. This metamorphic succession has been cut by six Messinian rhyolitic volcanic vents and all crystalline rocks have been covered by late Pleistocene eolianites. The kinematic evolution of the investigation area can be divided based on the deformation style and age. (1) The ductile deformation results in NE-SW trending stretching lineation and shear senses both top-to NE and top-to SW. Ar-Ar white mica cooling ages indicate an early Miocene age for this ductile deformation. (2) The brittle/ductile structures, which gradually advance from the previous ductile deformation, start with small but pervasive flanking folds, followed by larger shear bands and finally faults with tourmaline slickenlines. The shear sense is consistently top-to SW with middle to late Miocene age constrained by Ar-Ar white mica cooling ages and zircon fission-track data from Paros. (3a) Large, subvertical, sinistral strike-slip faults cross-cut the metamorphic rocks and show up to hundreds of meters displacement. Late Miocene age is constrained by apatite fission-track data from Paros and the observation that these faults are sealed by Messinian rhyolites. (3b) The Messinian volcanic rocks are almost exclusively deformed by E-W striking conjugate brittle normal faults, which started already during the formation of the volcanic rocks. No unequivocal tectonic deformation structures have been observed in the Pleistocene eolianites.

Draganits, E.; Huet, B.; Grasemann, B.; Schneider, D.; Ertl, A.

2012-04-01

265

Depositional and structural evolution of the Middle Miocene depositional episode, east-central Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Two widespread, transgressive deposits associated with the faunal top Amphistegina B (15.5 Ma) and Textularia W (12.1 Ma) define the Middle Miocene depositional episode. An extensive stratigraphic correlation framework established in this study allowed tracing of the middle Miocene sediment dispersal system from the shelf through the slope to the basin floor in the complex paleogeography of the east-central Gulf of Mexico. The Middle Miocene depositional episode is recorded in four genetic cycles (˜1 to 2 Ma), bounded by regional maximum flooding surfaces in the shelf and shelf margin setting, and three equivalent seismic sequences punctuated by condensed sections in the slope and basin floor. Two principal, long-lived extrabasinal fluvial/delta axes, the ancestral Mississippi and the Tennessee systems, provided the bulk of sediments that infilled the middle Miocene depocenters. Salt-related structural provinces controlled the configuration of the depocenters. Structural linked systems, dominated by gravity spreading, and a minibasin province, driven by differential subsidence, were established during the Middle Miocene depositional episode. Sediment supply coupled with wave energy flux, high-frequency sea-level changes, and salt tectonism determined the time and space distribution of progradation, aggradation, and retrogradation of system tracts. Middle Miocene shelf margins have prograded 20 to 40 miles from the relict lower Miocene shelf margin. Two depositional systems tracts characterize the constructional shelf margin: (1) a mixed-load fluvial-dominated platform delta/shelf-margin delta/delta-fed apron systems tract; and (2) a strandplain/shelf/muddy slope systems tract. However, the constructional, offlapping shelf margin systems were locally punctuated by a large-scale phase of retreat and erosion, named the Harang collapse system, in which a large volume of sediments bypassed the shelf margin to be deposited on the slope and basin floor. The Harang collapse system is a type of large-scale slope failure produced by massive salt-withdrawal, retreat of major delta systems, and high-frequency sea-level fluctuations. A large volume of sediment bypassed the confined minibasin province and the unconfined Florida slope at the flank of active deltaic depocenters, forming the long-lived MCAVLU submarine fan system (named for its location beneath the Mississippi Canyon, Atwater Valley, and Lund continental shelf (OCS areas) in the linked, primary minibasin corridor of the lower slope and basin floor. The MCAVLU submarine fan system evolved from a structurally-controlled, elongate sand-rich to mixed sand/mud fan to a large radial, mixed sand/mud fan. Significant untapped middle Miocene hydrocarbon resources remain in the confined channel fills and lobes of the Harang collapse system and sand-rich ponded facies assemblages of the MCAVLU submarine fan system.

Combellas Bigott, Ricardo Ignacio

266

New high-resolution record of middle to late Miocene climate evolution  

NASA Astrophysics Data System (ADS)

After the fairly warm Miocene climate optimum about 17-15 million years ago, Earth's climate began to cool. Holbourn et al. present a new high-resolution record of climate evolution over the middle to late Miocene, from 12.9 to 8.4 million years ago, based on stable isotopes in sedimentary benthic foraminifera in the western Pacific Ocean. They also combined their data with previously published data going back to 16 million years ago from the same location to study the transition from a warmer climate to a cooler one. They focus on the relationship between climate and changes in the eccentricity and obliquity of Earth's orbit around the Sun.

Balcerak, Ernie

2014-01-01

267

Astronomically forced teleconnection between Paratethyan and Mediterranean sediments during the Middle and Late Miocene  

Microsoft Academic Search

A high-resolution correlation between an orbital tuned Middle and early Late Miocene record of the Central Paratethys and an astronomically calibrated Mediterranean deep marine composite record is proposed. The astronomical tuning of the Sarmatian and Pannonian sedimentary record in the Vienna Basin confirms that the beginning of the Pannonian regional stage (lower Tortonian), dated in this work at 11.42 My, is

F. Lirer; M. Harzhauser; N. Pelosi; W. E. Piller; H. P. Schmid; M. Sprovieri

2009-01-01

268

Inferred relation of Miocene Bealville Fanglomerate to Edison Fault, Caliente Canyon area, Kern County, California  

SciTech Connect

The Bealville Fanglomerate is a very coarse, local, eastern torrential facies of the middle Tertiary marine sedimentary sequence of southern San Joaquin basin. This fanglomerate is exposed in lower Caliente Canyon east of Bakersfield. It is composed of unsorted boulder-size detritus of granitic rocks now exposed in the highlands on the east and south. The fanglomerate intertongues northwestward into the overlying Miocene fluvial Bena Gravel and probably partly into the underlying Oligocene-Miocene fluvial Walker Formation. In its eastern exposure, the Bealville Fanglomerate laps onto granitic basement. The Bealville Fanglomerate, as thick as 7000 ft (2200 m), dips southward into the north-dipping Edison fault. Pre-Tertiary granitic basement was elevated on the Edison fault to the south when the fault was contemporaneously active during the Miocene. Both the fanglomerate terrane north of the fault and the adjacent granitic basement terrane south of it are now eroded to low relief, so the fault is not expressed physiographically and is inactive. In contrast, the active White Wolf fault to the southeast is expressed by the northwest-facing escarpment slope of Bear Mountain. The Bealville Fanglomerate was deposited during the early and middle Miocene as coarse alluvial detritus on the western base of the rising Sierra Nevada uplift of granitic terrane. This southward-dipping fanglomerate is coarser and thicker than other formations deposited on the eastern margin of the San Joaquin basin. These conditions indicate that the fanglomerate was deposited rapidly on a southward-tilting block against a block of granitic basement being elevated on the Edison fault to the south, and it was derived from the adjacent granitic terrane to the east and from that elevated on the Edison fault to the south.

Dibblee, T.W. Jr.; Warne, A.H.

1986-04-01

269

Miocene tectonics of the Maramures area (Northern Romania): implications for the Mid-Hungarian fault zone  

Microsoft Academic Search

The interplay between the emplacement of crustal blocks (e.g. ``ALCAPA'', ``Tisza'', ``Dacia'') and subduction retreat is a key issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides new kinematic data from this transfer zone.

M. Tischler; H. R. Gröger; B. Fügenschuh; S. M. Schmid

2007-01-01

270

A map-view restoration of the Alpine-Carpathian-Dinaridic system for the Early Miocene  

Microsoft Academic Search

A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate tectonic configuration\\u000a before the onset of Miocene to recent deformations. Estimates of shortening and extension from the entire orogenic system\\u000a allow for a semi-quantitative restoration of translations and rotations of tectonic units during the last 20 Ma. Our restoration\\u000a yielded the following results: (1) The

Kamil Ustaszewski; Stefan M. Schmid; Bernhard Fügenschuh; Matthias Tischler; Eduard Kissling; Wim Spakman

2008-01-01

271

Miocene tectonics of the Maramures area (Northern Romania): implications for the Mid-Hungarian fault zone  

Microsoft Academic Search

The interplay between the emplacement of crustal blocks (e.g. “ALCAPA”, “Tisza”, “Dacia”) and subduction retreat is a key\\u000a issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by\\u000a transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides\\u000a new kinematic data from this transfer zone.

M. Tischler; H. R. Gröger; B. Fügenschuh; S. M. Schmid

2007-01-01

272

Functional anatomy of the limbs of erethizontidae (Rodentia, Caviomorpha): Indicators of locomotor behavior in Miocene porcupines.  

PubMed

Functional analysis of the limb bones of the erethizontid Steiromys duplicatus, one of the most abundant Miocene porcupines from Patagonia, provides evidence to infer their locomotor behavior. Remains of the giant Neosteiromys pattoni (Late Miocene of Northeast Argentina) are also analyzed. Osteological and myological features of extant porcupines were evaluated and used as a model to interpret the functional significance of Miocene species' limbs. Several features in erethizontids are compatible with the ability to climb: the low humeral tuberosities indicate a mobile gleno-humeral joint; the prominent and distally extended deltopectoral crest indicates a powerful pectoral muscle, which is particularly active when climbing; the humero-ulnar and humero-radial joints are indicative of pronation-supination movements; the well-developed lateral epicondylar ridge and the medially protruding entepicondyle are in agreement with an important development of the brachioradialis, supinator, flexor digitorum profundus, and pronator teres muscles, acting in climbing and grasping functions; the mechanical advantage of the biceps brachii would be emphasized because of its distal attachment on the bicipital tuberosity. As with extant porcupines, in Miocene species, the large femoral head would have permitted a broad range of abduction of the femur, and the medially protruding lesser trochanter would have emphasized the abduction and outward rotation of the femur by the action of the ilio-psoas complex. In S. duplicatus, the shape of the hip, knee, and cruro-astragalar, calcaneo-astragalar, and astragalo-navicular joints would have allowed lateral and rotational movements, although probably to a lesser degree than in extant porcupines. Foot features of S. duplicatus (e.g., great medial sesamoid bone, medial astragalar head, complete hallux) indicate that this species would have had grasping ability, but would not have achieved the high degree of specialization of Coendou. Steiromys duplicatus would have been a semiarboreal dweller, resembling Erethizon dorsatum. PMID:18157864

Candela, Adriana M; Picasso, Mariana B J

2008-05-01

273

Filling the gap: a fossil frogfish, genus Antennarius (Teleostei, Lophiiformes, Antennariidae), from the Miocene of Algeria  

Microsoft Academic Search

A new species of frogfish, Antennarius monodi sp. nov., is described from the Upper Miocene (Messinian) of Raz-el-Ain, near Oran, north-east Algeria. The type and only specimen of this taxon is the first articulated skeleton belonging to the family Antennariidae ever recorded as a fossil. The morphological and meristic characters observed support the inclusion of this species in the Antennarius

G. Carnevale; T. W. Pietsch

2006-01-01

274

Miocene Bahean stratigraphy in the Longzhong Basin, northern central China and its implications in environmental change  

Microsoft Academic Search

Fossil mammal-riched Neogene strata are widely distributed in the southeast corner of the huge Longzhong Basin at Tianshui,\\u000a Gansu Province, northern central China. Hipparion weihoense, a typical member of late Middle Miocene Bahean stage, was recently excavated at Yaodian along a well-exposed outcrop. Owing\\u000a to the importance of the Bahean stage in the mammalian evolution and its potential for environmental

Jijun Li; Jun Zhang; Chunhui Song; Zhijun Zhao; Yong Zhang; Xiuxi Wang; Jianming Zhang; Qiaoyu Cui

2006-01-01

275

Middle Miocene climate instability associated with high-amplitude CO2 variability  

NASA Astrophysics Data System (ADS)

amplitude of climatic change, as recorded in the benthic oxygen isotope record, has varied throughout geological time. During the late Pleistocene, changes in the atmospheric concentration of carbon dioxide (CO2) are an important control on this amplitude of variability. The contribution of CO2 to climate variability during the pre-Quaternary however is unknown. Here we present a new boron isotope-based CO2 record for the transition into the middle Miocene Climatic Optimum (MCO) between 15.5 and 17 Myr that shows pronounced variability between 300 ppm and 500 ppm on a roughly 100 kyr time scale during the MCO. The CO2 changes reconstructed for the Miocene are ~2 times larger in absolute terms (300 to 500 ppm compared to 180 to 280 ppm) than those associated with the late Pleistocene and ~15% larger in terms of climate forcing. In contrast, however, variability in the contemporaneous benthic oxygen isotope record (at ~1‰) is approximately two thirds the amplitude of that seen during the late Pleistocene. These observations indicate a lower overall sensitivity to CO2 forcing for Miocene (Antarctic only) ice sheets than their late Pleistocene (Antarctic plus lower latitude northern hemisphere) counterparts. When our Miocene CO2 record is compared to the estimated changes in contemporaneous ?18Osw (ice volume), they point to the existence of two reservoirs of ice on Antarctica. One of these reservoirs appears stable, while a second reservoir shows a level of dynamism that contradicts the results of coupled climate-ice sheet model experiments given the CO2 concentrations that we reconstruct.

Greenop, Rosanna; Foster, Gavin L.; Wilson, Paul A.; Lear, Caroline H.

2014-09-01

276

The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system  

Microsoft Academic Search

On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian–Mesopotamian mammalian biozones, spanning 9–6.5Ma. Additionally, we present results that demonstrate

Edgardo M. Latrubesse; Mario Cozzuol; Silane A. F. da Silva-Caminha; Catherine A. Rigsby; Maria Lucia Absy; Carlos Jaramillo

2010-01-01

277

The Middle Miocene to Recent Davis Strait Drift Complex: implications for Arctic–Atlantic water exchange  

Microsoft Academic Search

A large-scale contourite drift complex has been recognised on multi-channel 2D reflection seismic data acquired in the south-eastern\\u000a Davis Strait and adjacent Labrador Sea slope offshore West Greenland between 63°–66°N. Based on well-tie data, the drift complex\\u000a developed from the Middle Miocene to the Recent. It has been mapped in a wide variety of water depths ranging from about 700 m,

Tove Nielsen; Claus Andersen; Paul C. Knutz; Antoon Kuijpers

278

Paleomagnetic evidence for Late Miocene counterclockwise rotation of north coast carbonate sequence, Puerto Rico  

SciTech Connect

A paleomagnetic study of the essentially undeformed middle Tertiary carbonate sequence along the north coast of Puerto Rico reveals statistically significant pre-Pliocene discordance of characteristic component directions against those expected from cratonic North America for much of the section. Despite generally weak to moderately weak magnetic intensities, confirmation of the magnetization as primary in origin comes from the presence of two distinct components of magnetization, intrasite bipolarity, and/or the reproducibility of measurements. The mean geographic direction for the upper Oligocene to middle Miocene strata is 335.2{degree}/32.9{degree} and the corrected mean paleomagnetic pole is 207.6{degree}/66.5{degree}, (N = 3, {alpha}95 = 4.3{degree}). This suggests a counter-clockwise (CCW) block rotation of Puerto Rico and its microplate of 24.5{degrees} ({plus minus} 5.8{degrees}) during the late Miocene. Using a width of 250 km for the Northern Caribbean Plate Boundary Zone (NCPBZ) between the North American Plate and Caribbean Plate, the mean left lateral displacement implied is 1.8 to 2.4 cm/yr, which agrees fairly well with published relative motion rates for the two plates. Average rotation rate for 50 Ma to 20 Ma was 0.7{degree}/my but perhaps as great as 4{degree}/my in the Miocene. Resolution of mean paleolatitude indicates northward motion of a degree or less during the period of rotation. Causes of this short-lived rotation may include (1) tectonic escape from the inhibiting presence of the Bahama Banks and Beata Ridge during eastward motion of Puerto Rico along the sinistral transpressive Puerto Rico Trench and Muertos Trough fault systems or (2) changes in relative plate motions of the Caribbean and North American Plate during the late Miocene.

Reid, J.A.; Plumley, P.W. (Syracuse Univ., NY (United States)); Schellekens, J.H. (Univ. of Puerto Rico, Mayaguez (Puerto Rico))

1991-03-01

279

Confirmation of a late Oligocene-early Miocene age of the Deseadan Salla Beds of Bolivia  

Microsoft Academic Search

Three new fission-track (zircon) and four new K-Ar (biotite) dates corroborate a late Oligocene-early Miocene age (22-28 Ma) for the Salla Beds of Bolivia. These ages contrast markedly with the previously accepted age of about 35 Ma for these strata and their contained faunas, and recasts of order and chronology of interchange between New World and Old World mammals.

Charles W. Naeser; Edwin H. McKee; Noye M. Johnson; Bruce J. MacFadden

1987-01-01

280

Confirmation of a late Oligocene-early Miocene age of the Deseadan Salla Beds of Bolivia  

SciTech Connect

Three new fission-track (zircon) and four new K-Ar (biotite) dates corroborate a late Oligocene-early Miocene age (22-28 Ma) for the Salla Beds of Bolivia. These ages contrast markedly with the previously accepted age of about 35 Ma for these strata and their contained faunas, and recasts of order and chronology of interchange between New World and Old World mammals.

Naeser, C.W.; McKee, E.H.; Johnson, N.M.; MacFadden, B.J.

1987-11-01

281

Palaeoclimatic interpretation based on Middle Miocene planktonic Foraminifera: the Silesia Basin (Paratethys) and Monferrato (Tethys) records  

Microsoft Academic Search

A comparative study of the distribution and palaeoclimatic interpretation of temperature-related taxa of Middle Miocene planktonic foraminifera from the Paratethys Silesia Basin (southern Poland) and Tethys Monferrato area (northwestern Italy) is presented. The time span considered (Badenian–Langhian\\/Serravallian) is the last period of significant connection between the Paratethys and Mediterranean Tethys, even though the depositional conditions, water circulation and connection with

Erica Bicchi; Elena Ferrero; Malgorzata Gonera

2003-01-01

282

Characterization of Miocene-Pliocene carbonate platforms, southern Southwest Palawan Basin, Philippines  

E-print Network

CHARACTERIZATION OF MIOCENE-PLIOCENE CARBONATE PLATFORMS, SOUTHERN SOUTHWEST PALAWAN BASIN, PHILIPPINES A Thesis by MA. CORAZON VICTOR STA. ANA Submitted to the Office of Graduate Studies of Texas A&M University... A Thesis by MA. CORAZON VICTOR STA. ANA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee...

Sta. Ana, Ma. Corazon Victor

2009-06-02

283

40. MIOCENE-PLIOCENE SURFACE-WATER HYDROGRAPHY OF THE EASTERN EQUATORIAL ATLANTIC 1  

Microsoft Academic Search

Stable isotope analyses of four species of planktonic foraminifers and the benthic foraminifer, Cibicides wuellerstorfi, from Ocean Drilling Program Site 959 show that the Gulf of Guinea had a strong, shallow thermocline during the latest Miocene and early Pliocene prior to the first appearance of the Guinea Current at about 4.9 Ma. Gradients of ?18O between the surface-water species, Globigerinoides

Richard D. Norris

284

The age of the Miocene-Pliocene boundary in the Capo Rossello area (Sicily)  

NASA Astrophysics Data System (ADS)

Detailed correlations of magnetostratigraphy, biostratigraphy and lithostratigraphy reveal that the basal Pliocene is equally complete in the Eraclea Minoa and Capo Rossello sections (Sicily) and the Singa section (Calabria), and that, in accordance with the model of the Pliocene flooding event in the Mediterranean, the deposition of the pelagic marls of the Trubi Formation started synchronously on Sicily and in adjacent Calabria. In addition, the data obtained from the Trubi in the Eraclea Minoa section allows the age of the Miocene-Pliocene boundary to be adjusted slightly from 4.83-4.84 [1] to 4.86 Ma because downward extrapolation of both sedimentation rate and average duration of small-scale sedimentary cycles in the Trubi yields this age for the boundary in this section. Linearly interpolated ages for the top of the Sphaeroidinellopsis acme and the first substantial increase in Globorotalia margaritae (the FOD of this species is non-existent in the Mediterranean Pliocene) at Eraclea Minoa arrive at 4.74 and 4.63 Ma respectively. Because of the detailed magnetostratigraphy and the very accurate dating of the Miocene-Pliocene boundary, it is preferable to select the Eraclea Minoa section as the boundary stratotype rather than the Capo Rossello section. Finally, this age of 4.86 Ma for the Miocene-Pliocene boundary suggests that the beginning of the Pliocene is connected with the termination of a series of latest Miocene glaciations and that the re-establishment of open marine conditions in the Mediterranean might be of glacio-eustatic origin.

Hilgen, F. J.; Langereis, C. G.

1988-12-01

285

Confirmation of a late Oligocene-early Miocene age of the Deseadan Salla Beds of Bolivia.  

USGS Publications Warehouse

Three new fission-track (zircon) and four new K-Ar (biotite) dates corroborate a late Oligocene-early Miocene age (22-28 Ma) for the Salla Beds of Bolivia. These ages contrast markedly with the previously accepted age of about 35 Ma for these strata and their contained faunas, and recasts of order and chronology of interchange between New World and Old World mammals. -Authors

Naeser, C.W.; McKee, E.H.; Johnson, N.M.; Macfadden, B.J.

1987-01-01

286

Tectonic control on past circulation of the Mediterranean Sea : a model study of the late Miocene  

Microsoft Academic Search

We examine the effect of Late Miocene paleogeography on the circulation and water properties of the\\u000aMediterranean Sea by using an ocean circulation model. Results obtained for the past are compared to a control\\u000aexperiment with the present-day geometry. To focus on paleogeography, atmospheric forcing is always based on\\u000athe present-day climatology. We seek insight that allows us to test

P. Th. Meijer; R. Slingerland; M. J. R. Wortel

2004-01-01

287

Paleoenvironmental conditions in the Spanish Miocene-Pliocene boundary: isotopic analyses of Hipparion dental enamel.  

PubMed

Expansion of C(4) grasses during Late Miocene and Early Pliocene constitutes one of the most remarkable biotic events of the Cenozoic era. The Teruel-Alfambra region (northeastern Spain) contains one of the most complete Miocene-Pliocene sequences of mammalian fossil sites in the world. In this study, stable isotope (delta (13)C and delta (18)O) analyses have been performed on the tooth enamel from the equid Hipparion from 19 localities spanning a time interval from approximately 10.9 to 2.7 Ma. This time range starts with the first appearance of this genus in Spain and ends at its extinction. An increase in delta (13)C at about 4.2 Ma has been observed, indicative of a shift toward a more open habitat. This shift may be related to a large scale vegetation change which occurred across the Miocene-Pliocene boundary when C(4) grasses expanded. This expansion might in turn be linked to global tectonic events such as the uplift of the Himalaya and/or the closure of the Panama Isthmus. However, other more regional factors may have ultimately enhanced the trend toward more open habitats in the Western Mediterranean Basin. The Messinian Salinity Crisis was a major environmental event that may have been responsible for the isotopic changes seen in the equid Hipparion from the Iberian Peninsula along with an increase in the aridity detected approximately 4.6 Ma ago in the Sahara. Even though the exact factor triggering the isotopic change observed in the Hipparion enamel remains mostly unknown, this study demonstrates that the global environmental changes detected across the Miocene-Pliocene boundary are also recorded in the realm of the Iberian Peninsula. PMID:19190888

Domingo, Laura; Grimes, Stephen T; Domingo, M Soledad; Alberdi, M Teresa

2009-04-01

288

Middle Miocene hiatus in volcanic activity in the Great Basin area of the Western United States  

USGS Publications Warehouse

A summary of potassium-argon dates shows that a high level of igneous activity in the Great Basin and adjacent regions during middle Tertiary time (40 to 20 my ago) was followed by a period of relative quiescence in middle Miocene time that lasted for several million years (from 20 to 17 my ago). Volcanism resumed 16 my ago mainly at the margins of the region and has continued to the present. ?? 1970.

McKee, E.H.; Noble, D.C.; Silberman, M.L.

1970-01-01

289

The interaction between Aegean back-arc extension and Anatolia escape since Middle Miocene  

NASA Astrophysics Data System (ADS)

The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Lithosphere-scale analogue models were employed to display that the overall pattern of Aegean extension requires not only the combination of trench retreat and Anatolia escape since middle Miocene but also the presence of an inherited lithosphere-scale mechanical discontinuity: the Vardar Suture Zone (VSZ). The reactivation in dextral shear of the eastern branch of the VSZ accommodates both the trench retreat (NS stretching) and the westward escape of Anatolia (EW shortening) in the Cyclades area since middle Miocene. Additionally, our model shows that the North Anatolian Fault (NAF) is a late structure in the evolution of the Aegean, initiated around 10 Ma after the onset of Anatolia escape. The displacement field at the surface of the model allows the identification of sub-domains, which result from strain partitioning instead of being “rigid microplates”, directly comparable to the present-day displacement field (GPS) of the Aegean and western Anatolia. Our model provides a simple but powerful way to look at the dynamics of Aegean extension in two main stages. From middle Eocene to middle Miocene, extension was only driven by the southward retreat of the Hellenic trench at a rate lower than 1 cm·y- 1. Since middle Miocene, the combination of slab rollback with Anatolia westward escape resulted in a southwest direction of trench retreat, with an accelerating rate of up to 3 cm·y- 1.

Philippon, Mélody; Brun, Jean-Pierre; Gueydan, Frédéric; Sokoutis, Dimitrios

2014-09-01

290

Paleoaltimetry of the Early Miocene-Pliocene Oiyug basin, southern Tibet  

NASA Astrophysics Data System (ADS)

The stable isotope composition of carbonate and organic samples from the Oiyug basin in southern Tibet allows for model calculations of the Miocene-Pliocene paleoelevation of the Tibetan Plateau. We measured the oxygen isotope composition of pedogenic and lacustrine carbonates, and hydrogen isotope composition of n-alkanes from epicuticular plant waxes to reconstruct the ?18O and ?D of Oiyug basin paleometeoric waters. Calculated ?18O and ?D values from Oiyug carbonate and organic samples, respectively, are in close agreement, suggesting the preservation of an unaltered paleometeoric water isotopic signal for both archives. Calculated early-middle Miocene (~20-15 Ma) paleoelevation estimates for the Oiyug basin range from 3000-5400 m with an average of ~4700 m. Individual and average elevation estimates are identical within uncertainty to paleoelevation estimates based on Oiyug basin fossil floral physiognomy from the same interval. This is the first time that three independent paleoaltimeters have been directly compared and are in accord. Calculated late Miocene-Pliocene (~5 Ma) paleoelevation estimates range from 5300-6400 m with an average of ~5600 m. Given that the modern hypsometric mean elevation of the Oiyug basin is ~5000 m, our results allow for a possible decrease in the average elevation of the southern part of the Tibetan Plateau since the late Miocene, compatible with widespread east-west extension in Tibet since at least that time. The results of our study further demonstrate the utility of lipid-based estimates of paleoelevation and the value of a multiple-proxy approach of testing the fidelity of isotope-based paleoelevation records.

Currie, B. S.; Polissar, P. J.; Rowley, D. B.; Freeman, K. H.

2008-12-01

291

The role of fire in Miocene to Pliocene C4 grassland and ecosystem evolution  

NASA Astrophysics Data System (ADS)

Modern savannah grasslands were established during the late Miocene and Pliocene (8-3 million years ago). In the tropics, grasslands are dominated by grasses that use the C4 photosynthetic pathway, rather than the C3 pathway. The C4 pathway is better adapted to warm, dry and low-CO2 conditions, leading to suggestions that declining atmospheric CO2 levels, increasing aridity and enhanced rainfall seasonality allowed grasses using this pathway to expand during this interval. The role of fire in C4 expansion may have been underestimated. Here we use analyses of pollen, microscopic charcoal and the stable isotopic composition of plant waxes from a marine sediment core off the coast of Namibia to reconstruct the relative timing of changes in plant composition and fire activity for the late Miocene and Pliocene. We find that in southwestern Africa, the expansion of C4 grasses occurred alongside increasing aridity and enhanced fire activity. During further aridification in the Pliocene, the proportion of C4 grasses in the grasslands increased, while the grassland contracted and deserts and semi-deserts expanded. Our results are consistent with the hypothesis that ecological disturbance by fire was an essential feedback mechanism leading to the establishment of C4 grasslands in the Miocene and Pliocene.

Hoetzel, Sebastian; Dupont, Lydie; Schefuß, Enno; Rommerskirchen, Florian; Wefer, Gerold

2013-12-01

292

Terpenoid Compositions and Botanical Origins of Late Cretaceous and Miocene Amber from China  

PubMed Central

The terpenoid compositions of the Late Cretaceous Xixia amber from Central China and the middle Miocene Zhangpu amber from Southeast China were analyzed by gas chromatography-mass spectrometry (GC-MS) to elucidate their botanical origins. The Xixia amber is characterized by sesquiterpenoids, abietane and phyllocladane type diterpenoids, but lacks phenolic abietanes and labdane derivatives. The molecular compositions indicate that the Xixia amber is most likely contributed by the conifer family Araucariaceae, which is today distributed primarily in the Southern Hemisphere, but widely occurred in the Northern Hemisphere during the Mesozoic according to paleobotanical evidence. The middle Miocene Zhangpu amber is characterized by amyrin and amyrone-based triterpenoids and cadalene-based sesquiterpenoids. It is considered derived from the tropical angiosperm family Dipterocarpaceae based on these compounds and the co-occurring fossil winged fruits of the family in Zhangpu. This provides new evidence for the occurrence of a dipterocarp forest in the middle Miocene of Southeast China. It is the first detailed biomarker study for amber from East Asia. PMID:25354364

Shi, Gongle; Dutta, Suryendu; Paul, Swagata; Wang, Bo; Jacques, Frederic M. B.

2014-01-01

293

Palynostratigraphy, palaeoclimates and palaeodepositional environments of the Miocene aged Agbada Formation in the Niger Delta, Nigeria  

NASA Astrophysics Data System (ADS)

A diverse assemblage of palynomorphs dominated by terrestrially derived pollen and spores is reported from three wells penetrating the Miocene Agbada Formation. The pteridophyte and bryophyte spores which form the background assemblages in the three wells are good indicators of humid tropical climates which might have prevailed in the Niger Delta during the Miocene. The abundance and variations of climate-sensitive taxa including mangrove affiliated pollen and spore types Acrostichumsporites, Psilatricolporites crassus, Zonocostites ramonae and Graminidites annulatus representing the savannah vegetation cover indicate a complex interplay between periods of wetter and drier climates. Marine-derived dinoflagellate cysts and foraminiferal test linings are significantly present in the three wells. Taxa indicating freshwater contributions including Botryococcus spp., Chomotriletes minor, Ovoidites parvus and Pediastrum spp. are also represented numerically across the three wells. The presence of age diagnostic palynomorphs such as Crassoretitriletes vanraadshooveni, Retibrevitricolporites obodoensis, Tuberculodinium vancampoae, Zonocostites ramonae and Tuberculodinium vancampoae recovered in the three sections studied suggest a Miocene age for the investigated Agbada Formation. The proposed age is supported by the ranges of key palynomorphs in contemporaneous basins in Africa, northern South America and other parts of the World.

Bankole, Samson I.; Schrank, Eckart; Osterloff, Peter L.

2014-07-01

294

Seastacks buried beneath newly reported Lower Miocene sandstone, northern Santa Barbara County, California  

SciTech Connect

Three large, isolated exposures of a light-gray, coarse-grained, thick-bedded sandstone unit occur in the northern San Rafael Mountains of Santa Barbara County, California. These rocks are moderately fossiliferous and contain Vertipecten bowersi, Amussiopecten vanvlecki, Aequipecten andersoni, Otrea howelli, shark teeth, whale bones, and regular echinoid spines. The fossils indicate that the sandstone unit, although previously reported as upper(.) Miocene, correlates best with the lower Miocene Vaqueros Formation. This unit was deposited in angular unconformity on a Cretaceous, greenish-gray turbidite sequence of interbedded sandstone and shale, and onlaps the unconformity erosion surface from west to east, the unit being thicker in the west and older at its base. The underlying Cretaceous sandstone beds are well indurated, and during the eastward transgression of the early Miocene sea, they resisted wave erosion and stood as seastacks offshore of the advancing coastline, thus creating a very irregular topographic surface upon which the Vaqueros Formation was deposited. Some seastacks were as much as 4 m tall, as indicated by inliers of Cretaceous rock surrounded by 4-m thick sections of the Vaqueros Formation.

Fritsche, A.E.; Hanna, F.M.

1985-04-01

295

Late Miocene remagnetization within the internal sector of the Northern Apennines, Italy  

USGS Publications Warehouse

Paleomagnetic and geologic evidence indicates that Upper Jurassic radiolarian cherts of both the Tuscan Cherts Formation (continental margin, Tuscan Units) and the Monte Alpe Cherts Formation (oceanic crust, Ligurian Units) were remagnetized during Miocene orogenesis of the Northern Apennines of Italy. Characteristic overprint magnetizations with reversed polarities have been found over a large area within the internal sector of the Northern Apennines, including eastern Liguria, Elba Island and the Thyrrenian margin, and west of the Middle Tuscan Ridge. The reversed-polarity overprint (average direction: D=177??, I=-52??, ??95=15??) was most likely acquired during Late Miocene uplift and denudation of the orogenic chain, and thermochemical remagnetization was a probable consequence of increased circulation of orogenic fluids. Similarly, mostly reversed-polarity directions of magnetization have been found by other workers in overlying post-orogenic Messinian sediments (D=177??, I=-57??, ??95=3??), which show little counterclockwise (CCW) vertical-axis rotation with respect to stable Europe (-8??5??). The Monte Alpe Cherts sampled at sites in the external sector of the Northern Apennines, close to major tectonic features, have normal- polarity overprint directions with in situ W-SW declinations. Since the overlying post-orogenic Messinian sediments have not been substantially rotated about vertical axes, the evidence points to an earlier,pre-Late Miocene remagnetization in the external parts of the orogenic chain. ?? 2004 Elsevier B.V. All rights reserved.

Aiello, I.W.; Hagstrum, J.T.; Principi, G.

2004-01-01

296

Miocene honey bees from the Randeck Maar of southwestern Germany (Hymenoptera, Apidae)  

PubMed Central

Abstract The Miocene Randeck Maar (southwestern Germany) is one of the only sites with abundant material of fossil honey bees. The fauna has been the focus of much scrutiny by early authors who recognized multiple species or subspecies within the fauna. The history of work on the Randeck Maar is briefly reviewed and these fossils placed into context with other Tertiary and living species of the genus Apis Linnaeus (Apinae: Apini). Previously unrecorded specimens from Randeck Maar were compared with earlier series in an attempt to evaluate the observed variation. A morphometric analysis of forewing venation angles across representative Recent and Tertiary species of Apis as well as various non-Apini controls was undertaken to evaluate the distribution of variation in fossil honey bees. The resulting dendrogram shows considerable variation concerning the wing venation of Miocene Apini, but intergradation of other morphological characters reveals no clear pattern of separate species. This suggests that a single, highly variable species was present in Europe during the Miocene. The pattern also supports the notion that the multiple species and subspecies proposed by earlier authors for the Randeck Maar honey bee fauna are not valid, and all are accordingly recognized as Apis armbrusteri Zeuner. PMID:21594072

Kotthoff, Ulrich; Wappler, Torsten; Engel, Michael S.

2011-01-01

297

Juvenile hominoid cranium from the late Miocene of southern China and hominoid diversity in Asia  

PubMed Central

The fossil ape Lufengpithecus is known from a number of late Miocene sites in Yunnan Province in southern China. Along with other fossil apes from South and Southeast Asia, it is widely considered to be a relative of the extant orangutan, Pongo pygmaeus. It is best represented at the type site of Shihuiba (Lufeng) by several partial to nearly complete but badly crushed adult crania. There is, however, an additional, minimally distorted cranium of a young juvenile from a nearly contemporaneous site in the Yuanmou Basin, which affords the opportunity to better assess the relationships between Lufengpithecus and Pongo. Comparison with similarly aged juvenile skulls of extant great apes reveals no features suggesting clear affinities to orangutans, and instead reveals a morphological pattern largely consistent with a stem member of the hominid (great ape and human) clade. The existence at this time of other hominids in South Asia (Sivapithecus) and Southeast Asia (Khoratpithecus) with clear craniofacial affinities to Pongo suggests both more diversity among Asian Late Miocene apes and more complex patterns of dispersal than previously supposed. Major differences in the associated mammal faunas from the southern China sites and those from South and Southeast Asia are consistent with these findings and suggest more than one dispersal route of apes into East Asia earlier in the Miocene. PMID:22511723

Kelley, Jay; Gao, Feng

2012-01-01

298

Genesis of siderite in the Upper Miocene, offshore Sarawak: Constraints on pore fluid chemistry and diagenetic history  

SciTech Connect

The cored sequence of the Upper Miocene reservoir of Baram field, offshore Sarawak, consists of cyclic deltaic-related quartz-rich sandstones and mudstones interpreted to have been deposited during storm events in shallow to midshelf water depths. The sequence is intercalated with minor tidal intervals. Authigenic siderite is common in sandstones throughout the sequence. Siderite cemented zones are up to 2 m thick. The cement is found in four different sandstone types: laminated sandstone, massive sandstone, bioturbated sandstone, and in association with shell fragments. Whole-rock XRD gives estimates of 20 to 40% siderite in bioturbated sandstones and 10 to 25% for the others. Petrographic analysis reveals that diagenetic siderite occurs in four different crystal morphologies: rhombic, [open quotes]bundles,[close quotes] acicular, and cylindrical. The rhombic siderite, which commonly occurs in bioturbated sandstone, has the most adverse effect on the poroperm characteristics of the sandstones, reducing porosity to 10% and permeability to 2 md. [sigma][sup 13]C and [sigma][sup 18]O plots show groupings based on morphology. Bundled and acicular siderite show ranges of [sigma][sup 13]C[sub PDB] of [minus]15 to [minus]25 and [sigma][sup 18]O[sub PDB] of 0 to [minus]1. The late Miocene seawater [sigma][sup 18]O estimate for the region is [minus]0.8 PDB. This would give the bundles/acicular siderite a temperature of formation range of 26[degrees] to 30[degrees]C. The [sigma][sup 18]O values are compatible with precipitation at shallow burial depth from unaltered seawater; [sigma][sup 13]C values are inherited from sulfate reduction horizons. Rhombic siderite has ranges of [sigma][sup 13]C[sub PDB] of [minus]5 to [minus]15 and [sigma][sup 18]O[sub PDB] of [minus]3 to [minus]4. The range of [sigma][sup 13]C indicates that siderite diagenesis occurred within both the shallow sulfate reduction zone and at deeper levels within the zone of decarboxylation.

Abdul Hadi, A.R.; Astin, T.R. (Univ. of Reading (United Kingdom))

1994-07-01

299

The incrementally zoned Miocene Ayagaures ignimbrite (Gran Canaria, Canary Islands)  

Microsoft Academic Search

The 20–25m thick trachyphonolitic Ayagaures ignimbrite cooling unit [(AY); 11.8Ma] exposed over 250km2 (onshore volume ca. 4.5km3 DRE) is the uppermost and most voluminous cooling unit of the Middle Fataga Formation (MFF), part of the Fataga Group (ca. 13.3–ca. 9Ma) on Gran Canaria (GC), Canary Islands (28°00? N, 15°35? W). Up to 19 flow units (named b–t) subdividing the AY

Martin Jutzeler; Hans-Ulrich Schmincke; Mari Sumita

2010-01-01

300

Chewing through the Miocene: an examination of the feeding musculature in the ground sloth Hapalops from South America (Mammalia: Pilosa)  

PubMed Central

Hapalops, a smaller-sized and early sloth of the Megatheroidea, appeared in the middle Miocene Santa Cruz formation of Argentina. This genus is part of the group from which later, larger megatheroids arose, i.e., Nothrotheriops and Megatherium. Many cranial characters support this idea; however Hapalops is not merely a smaller antecedent of the later forms. Specifically, Hapalops retains short anterior caniniform teeth, and a temporomandibular joint elevated above the cheek tooth row; a combination distinct among sloths. An elevated temporomandibular joint occurs in Bradypus, a tree sloth with anterior chisel-shaped teeth instead of caniniforms, and the tree sloth Choloepus, which is aligned with the megalonychids, has anterior caniniforms. Hapalops has an elongated zygomatic ascending process that is reminiscent of that in Bradypus; however, the Bradypus skull is extremely foreshortened while that of Hapalops is elongated, as in nothrotheres, but not deepened as in megatheres. Previous work identified many sloth cranial character complexes, and functional limitations on skull feature combinations. The unique Hapalops character patterns indicate a selective feeder with a mediolaterally oriented grinding stroke during mastication. PMID:25075299

Naples, Virginia L.; McAfee, Robert K.

2014-01-01

301

Soft-sediment deformation structures in seismically affected deep-sea Miocene turbidites (Cilento Basin, southern Italy)  

NASA Astrophysics Data System (ADS)

Soft-sediment deformation structures (SSDS) are widespread in the upper part of the S. Mauro Formation (Cilento Group, Middle-Late Miocene). The succession is represented mainly by thick and very thick, massive, coarse-grained sandstones, deposited by rapid sedimentation of high-density turbidity currents. The most common SSDS are short pillars, dishes, sedimentary sills and convolutions. They occur mostly in the upper parts of sandstone beds. Vertical tubes of 4-5 cm in diameter and up to 50 cm long constitute the most striking structures. They begin in the middle part of sandstone beds, which are basically massive or contain faint dish structures. These tubes can bifurcate upwards and/ or pass into bedding-parallel veins or dikes. The vertical tubes sometimes form sand volcanoes on the then sedimentary surface. The SSDS are interpreted as the result of earthquake-triggered liquefaction and/or fluidisation of the turbidites that were affected by the seismic shocks. This implies that the deformed layers should be considered as seismites.

Valente, Alessio; ?l?czka, Andrzej; Cavuoto, Giuseppe

2014-07-01

302

Geological and Hydrodynamical Examination of the Bathyal Tsunamigenic Origin of Miocene Conglomerates in Chita Peninsula, Central Japan  

NASA Astrophysics Data System (ADS)

A conglomerate appears on a rocky coast called "Tsubutega-ura Coast", located on the southwestern coast near the southern tip of the Chita Peninsula, Aichi Prefecture, central Japan. The conglomerate belongs to Miocene sedimentary rocks termed the Morozaki Group. The conglomerate includes meter-scale boulders, indicating that it was formed by an extraordinary event. In the geological investigation, we observed that the conglomerate shows alternate changes of paleocurrent directions between seaward and landward. This feature is supposed to be formed by tsunami currents. In the hydrodynamical investigation, we obtained following results: (1) the lowest limit of a current velocity to move a boulder of about 3 m in diameter would be about 2-3 m/s, (2) the speed of tsunami currents reproduced by tsunami simulation exceeds 3 m/s at 300 m in depth when the tsunami is generated by a gigantic earthquake with magnitude 9.0 or more, (3) the transport distance of the boulder would be several hundred meters to several kilometers by one tsunami event caused by a gigantic earthquake. We conclude that tsunamis best explain the formation of the conglomerate deposited in upper bathyal environments about 200-400 m depth, both from geological and hydrodynamical viewpoints.

Tachibana, Toru; Tsuji, Yoshinobu

2011-06-01

303

Stratigraphy and paleomagnetism of a 3-km-thick Miocene lava pile in the Mjoifjördur area, eastern Iceland  

NASA Astrophysics Data System (ADS)

We have carried out stratigraphic mapping in the Upper Miocene basalt lava pile around the fjords Mjoifjördur and Seydisfjördur, eastern Iceland. The mapping is based on conventional methods including the use of interbasaltic clastic horizons and petrographically distinct lava groups. These units are also used to provide correlations with the Nordfjördur area south of Mjoifjördur. We present a 3-km composite stratigraphic column for the area between Mjoifjördur and Seydisfjördur. The geology of this area shows some differences from the classical model of Walker for the structure of eastern Iceland partly due to the fact that most of Mjoifjördur is not in the vicinity of central volcanoes. Detailed laboratory measurements of remanent magnetization were carried out on oriented core samples from 363 lavas in 10 selected profiles. The local paleomagnetic polarity stratigraphy supports correlations made on the basis of other criteria. Over 20 geomagnetic reversals are recorded in the eastern Iceland lava pile in a period approximately 13-10 Ma ago. The geomagnetic field during this period averages to a central axial dipole field, and its overall statistical properties resemble those obtained in earlier surveys in Iceland.

Kristjansson, Leo; Gudmundsson, Agust; Haraldsson, Hreinn

1995-12-01

304

Stratigraphy and paleomagnetism of a 3-km-thick Miocene lava pile in the Mjoifjördur area, eastern Iceland  

NASA Astrophysics Data System (ADS)

We have carried out stratigraphic mapping in the Upper Miocene basalt lava pile around the fjords Mjoifjördur and Seydisfjördur, eastern Iceland. The mapping is based on conventional methods including the use of interbasaltic clastic horizons and petrographically distinct lava groups. These units are also used to provide correlations with the Nordfjördur area south of Mjoifjördur. We present a 3-km composite stratigraphic column for the area between Mjoifjördur and Seydisfjördur. The geology of this area shows some differences from the classical model of Walker for the structure of eastern Iceland partly due to the fact that most of Mjoifjördur is not in the vicinity of central volcanoes. Detailed laboratory measurements of remanent magnetization were carried out on oriented core samples from 363 lavas in 10 selected profiles. The local paleomagnetic polarity stratigraphy supports correlations made on the basis of other criteria. Over 20 geomagnetic reversals are recorded in the eastern Iceland lava pile in a period approximately 13-10Ma ago. The geomagnetic field during this period averages to a central axial dipole field, and its overall statistical properties resemble those obtained in earlier surveys in Iceland.

Kristjansson, Leo; Gudmundsson, Agust; Haraldsson, Hreinn

305

Local Group(s)  

E-print Network

The properties of the galaxies of the Local Group are reviewed, followed by a brief discussion of nearby groups. The galaxy groups in our vicinity - the M81 group, the Cen A group, and the IC 342/Maffei group - are in many respects Local Group analogs: Their luminosity functions, galaxy content, fractional galaxy type distribution, crossing times, masses, and zero-velocity surface radii are similar to those of the Local Group. Also, the nearby groups usually consist of two subgroups, some of which approach each other and may ultimately merge to form a fossil group. These poor groups contrast with the less evolved, loose and extended galaxy ``clouds'' such as the Scl group and the CVn I cloud. These are characterized by long crossing times, are dominated by gas-rich, late-type galaxies, and lack gas-deficient, low luminosity early-type dwarfs. These clouds may be groups still in formation. The local Hubble flow derived from the clouds and groups is very cold.

Eva K. Grebel

2006-05-22

306

Fluids circulation during the Miocene rifting of the Penedès half-graben, NE Iberian Peninsula  

NASA Astrophysics Data System (ADS)

The Penedès half-graben, located in the north-western part of the Mediterranean, is a NE-SW oriented basin generated during the Miocene rifting. This graben is bounded to the northwest by the SE-dipping Vallès-Penedès fault, which places the Mesozoic rocks in contact with the Miocene basin-fill. The basin is filled with an up to 4 km thick succession of sediments divided into three lithostratigraphic units. From base to top: (1) a lower continental complex, (2) a continental to marine complex and (3) an upper continental complex. These units are covered by Pliocene deposits which onlap a Messinian regional erosive surface. The structural features within the Penedès half-graben allow defining three deformational phases during the Miocene rifting. The first, during the syn-rift, two successive stages of NE-SW normal faults were formed. The second, during the early post-rift, one stage of NE-SW normal faults and one minor compression phase with a dextral directional developed. The third, during the late post-rift, two successive stages of N-S trending extensional fractures (faults and joints) and one minor compression with a sinistral component developed. The fractures related to the syn-rift stage acted as conduits for meteoric fluids both, in the phreatic and in the vadose zone. During the early post-rift, Fe2+- rich fluids precipitated oxides along the NE-SW fault planes. The dextral directional faults served as conduits for meteoric fluids which reequilibrated totally the marine Miocene host rocks under the phreatic environment. The late post-rift stage was characterized by marine fluids upflowing through the N-S fractures, probably derived from the Miocene marine interval, which mixed with meteoric fluids producing dolomitization. The second set of N-S fractures served as conduits for meteoric fluids characterised by ?13C-depleted soil-derived CO2 attributed to precipitation in the vadose zone. The change from phreatic to vadose meteoric environment and the prevailing of these vadose conditions is interpreted as the falling-down of the meteoric water table related to a generalized sea level fall in the Mediterranean area during the Messinian and/or with the uplift of the basin.

Baqués, Vinyet; Travé, Anna; Cantarero, Irene

2013-04-01

307

The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system  

NASA Astrophysics Data System (ADS)

On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian-Mesopotamian mammalian biozones, spanning 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimões Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes (˜ 3°-15°S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary basin, and became instead an erosional area that contributed sediments to the Amazon fluvial system. At that time, the lowland fluvial systems of southwestern Amazonia (the Purus, Jurua and Javarí basins) become isolated from the Andes by the newly formed north-flowing Ucayali system and south-east flowing Madre de Dios System. It was during the early Pliocene that the Amazon fluvial system integrated regionally and acquired its present appearance, and also when it started to drain water and sediments on a large scale to the Atlantic Ocean.

Latrubesse, Edgardo M.; Cozzuol, Mario; da Silva-Caminha, Silane A. F.; Rigsby, Catherine A.; Absy, Maria Lucia; Jaramillo, Carlos

2010-05-01

308

Pacific warm pool and cold tongue evolution since late Miocene: Implications for El Niño  

NASA Astrophysics Data System (ADS)

El Niño - Southern Oscillation (ENSO) is a consequence of tropical Pacific ocean-atmosphere dynamics and exerts control on Earth's interannual climate variability. Sea surface temperatures (SSTs) in the Pacific warm pool and cold tongue have been shown to be diagnostic for the strength of the Walker Circulation and ENSO conditions. Ancient SST reconstructions suggest that the temperature of the Pacific warm pool was invariant during the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and then subsequently cooled. The appearance of a negligible east-west equatorial Pacific Ocean temperature gradient during the Pliocene is used to infer substantially reduced cold water equatorial upwelling, a weak Walker Circulation, and a "permanent" El Niño. Some recent records suggest otherwise. For example, high-resolution records in Pacific and Mediterranean region show quasi-periodic climate variability (2-7 years) during the late Miocene - Pliocene, consistent with ENSO conditions and in conflict with the prevailing climate paradigm. Here we show a multi-proxy (TEX86, Uk'37), multi-site reconstruction of SSTs in the Pacific warm pool (ODP Sites 806 and 1143) and cold tongue (ODP 846 and 850) since late Miocene (~12 Ma). TEX86 temperatures from both sites show long-term cooling of the western warm pool since late Miocene, in contrast to an apparent invariant temporal character previously assumed. At Site 850, cold tongue temperatures from both TEX86 and Uk'37 also show a cooling trend, with TEX86 much more variable than Uk'37. Further, TEX86-calculated temperatures are consistently cooler than Uk'37 temperatures since ~6 Ma, and suggest different production depths or seasons, whereas deviations of TEX86 and Uk'37 signals might be recording physical/chemical property changes in the cold tongue (e.g., the strength and seasonality of upwelling, stratification and nutrient supply). When all records are stacked, a ~3°C zonal temperature gradient persists between 12 and 6 Ma, and then increases toward modern-day conditions. Considering sedimentary records that show interannual variability during late Miocene - Pliocene, a ~3°C mean zonal gradient might be large enough to sustain El Niño - La Niña variability and thus directly challenges the notion of a permanent El Niño state during warmer global conditions. The persistence a significant and consistent zonal gradient during warmer Miocene conditions suggests that the Pliocene evolution of stronger E-W equatorial SST gradients was driven by non-linear effects related to declining global temperatures or resulted from threshold effects related to the tectonic evolution of the region.

Zhang, Y.; Pagani, M.

2012-12-01

309

Paleomagnetic quantification of upper-plate deformation during Miocene detachment faulting in the Mohave Mountains, Arizona  

USGS Publications Warehouse

Paleomagnetic data from Miocene (???20 Ma) volcanic rocks and dikes of west central Arizona reveal the tilt history of Proterozoic crystalline rocks in the hanging wall of the Chemehuevi-Whipple Mountains detachment fault. We obtained magnetization data from dikes and flows in two structural blocks encompassing Crossman Peak and Standard Wash in the Mohave Mountains. In the Crossman block the dike swarm records two components of primary magnetization: (1) CNH, a normal polarity, high-unblocking-temperature or high-coercivity component (inclination, I = 48.5??, declination, D = 6.4??), and (2) CRHm, a reversed polarity, high-temperature or high-coercivity component (I = -33.6??, D = 197.5??). Argon age spectra imply that the dikes have not been reheated above 300??C since their emplacement, and a baked-contact test suggests that the magnetization is likely to be Miocene in age. CRHm deviates from the expected direction of the Miocene axial dipole field and is best explained as a result of progressive tilting about the strike of the overlying andesite flows. These data suggest that the Crossman block was tilted 60?? to the southwest prior to intrusion of the vertical dike swarm, and the block continued to tilt during a magnetic field reversal to normal polarity (CNH). Miocene dikes in the Crossman block are roughly coplanar, so the younger dikes with normal polarity magnetization intruded along planes of weakness parallel to the earlier reversed polarity swarm. An alternative explanation involves CNH magnetization being acquired later during hydrothermal alteration associated with the final stages of dike emplacement. In the Standard Wash block, the primary component of magnetization is a dual-polarity, high-temperature or high-coercivity component (SWHl, I = 7.2??,D= 0.7??). To produce agreement between the expected Miocene magnetic direction and the SWH component requires (1) correcting for a 56?? tilt about the strike of flow bedding and (2) removing a counterclockwise vertical-axis rotation of 20??. The two rotations restore the Standard Wash dikes to vertical, make parallel the dike layering in the Crossman and Standard Wash blocks, and align the strikes of bedding in both blocks. Geologic mapping, geochemical evidence, and paleomagnetic data are consistent with the upper plate of the Mohave Mountains having tilted in response to formation of the underlying detachment fault.

Pease, V.; Hillhouse, J. W.; Wells, R. E.

2005-01-01

310

Palinspastic reconstruction of southeastern California and southwestern Arizona for the middle Miocene  

NASA Technical Reports Server (NTRS)

A paleogeographic reconstruction of southeastern California and southwestern Arizona at 10 Ma was made based on available geologic and geophysical data. Clockwise rotation of 39 deg was reconstructed in the eastern Transverse Ranges, consistent with paleomagnetic data from late Miocene volcanic rocks, and with slip estimates for left-lateral faults within the eastern Transverse Ranges and NW-trending right lateral faults in the Mojave Desert. This domain of rotated rocks is bounded by the Pinto Mountain fault on the north. In the absence of evidence for rotation of the San Bernardino Mountains or for significant right slip faults within the San Bernardino Mountains, the model requires that the late Miocene Pinto Mountain fault become a thrust fault gaining displacement to the west. The Squaw Peak thrust system of Meisling and Weldon may be a western continuation of this fault system. The Sheep Hole fault bounds the rotating domain on the east. East of this fault an array of NW-trending right slip faults and south-trending extensional transfer zones has produced a basin and range physiography while accumulating up to 14 km of right slip. This maximum is significantly less than the 37.5 km of right slip required in this region by a recent reconstruction of the central Mojave Desert. Geologic relations along the southern boundary of the rotating domain are poorly known, but this boundary is interpreted to involve a series of curved strike slip faults and non-coaxial extension, bounded on the southeast by the Mammoth Wash and related faults in the eastern Chocolate Mountains. Available constraints on timing suggest that Quaternary movement on the Pinto Mountain and nearby faults is unrelated to the rotation of the eastern Transverse Ranges, and was preceded by a hiatus during part of Pliocene time which followed the deformation producing the rotation. The reconstructed Clemens Well fault in the Orocopia Mountains, proposed as a major early Miocene strand of the San Andreas fault, projects eastward towards Arizona, where early Miocene rocks and structures are continuous across its trace. The model predicts a 14 deg clockwise rotation and 55 km extension along the present trace of the San Andreas fault during late Miocene and early Pliocene time. Palinspastic reconstructions of the San Andreas system based on this proposed reconstruction may be significantly modified from current models.

Richard, Stephen M.

1992-01-01

311

Ionic liquid-based one-step micellar extraction of multiclass polar compounds from hawthorn fruits by ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry.  

PubMed

An ionic liquid (IL)-based one-step micellar extraction procedure was developed for the extraction of multiclass polar analytes (protocatechuic acid, chlorogenic acid, epicatechin, hyperoside, isoquercitrin, quercetin) from hawthorn fruits and their determination using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF/MS). Compared to conventional organic solvent extractions, this newly proposed method was much easier, more sensitive, environmentally friendly, and effective as well. Several important parameters influencing the micellar extraction efficiency are discussed, such as selection of ILs, surfactant concentration, and extraction time. Under the optimal conditions, good linearity was achieved for each analyte with correlation coefficients (r(2)) ranging from 0.9934 to 0.9999, and the recovery values ranged from 89.3 to 106% with relative standard deviations lower than 5.5%. Results suggest that the IL-based one-step micellar extraction could be an alternative and promising means in future food analysis. PMID:24845828

Hu, Shuai-Shuai; Yi, Ling; Li, Xing-Ying; Cao, Jun; Ye, Li-Hong; Cao, Wan; Da, Jian-Hua; Dai, Han-Bin; Liu, Xiao-Juan

2014-06-11

312

Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California  

USGS Publications Warehouse

The right lateral San Gabriel Fault Zone in southern California extends from the northwestern corner of the Ridge Basin southeastward to the eastern end of the San Gabriel Mountains. It bifurcates to the southeast in the northwestern San Gabriel Mountains. The northern and older branch curves eastward in the range interior. The southern younger branch, the Vasquez Creek Fault, curves southeastward to merge with the Sierra Madre Fault Zone, which separates the San Gabriel Mountains from the northern Los Angeles Basin margin. An isolated exposure of partly macrofossiliferous nearshore shallow-marine sandstone, designated the Gold Canyon beds, is part of the southwest wall of the fault zone 5.5 km northwest of the bifurcation. These beds contain multiple subordinate breccia-conglomerate lenses and are overlain unconformably by folded Pliocene-Pleistocene Saugus Formation fanglomerate. The San Gabriel Fault Zone cuts both units. Marine macrofossils from the Gold Canyon beds give an age of 5.2+-0.3 Ma by 87Sr/86Sr analyses. Magnetic polarity stratigraphy dates deposition of the overlying Saugus Formation to between 2.6 Ma and 0.78 Ma. Distinctive metaplutonic rocks of the Mount Lowe intrusive suite in the San Gabriel Range are the source of certain clasts in both the Gold Canyon beds and Saugus Formation. Angular clasts of nondurable Paleocene sandstone also occur in the Gold Canyon beds. The large size and angularity of some of the largest of both clast types in breccia-conglomerate lenses of the beds suggest landslides or debris flows from steep terrain. Sources of Mount Lowe clasts, originally to the north or northeast, are now displaced southeastward by faulting and are located between the San Gabriel and Vasquez Creek faults, indicating as much as 12+-2 km of post-Miocene Vasquez Creek Fault right separation, in accord with some prior estimates. Post-Miocene right slip thus transferred onto the Vasquez Creek Fault southeast of the bifurcation. The right separation on the Vasquez Creek Fault adds to the generally accepted 22-23 km of middle-late Miocene right separation established for the San Gabriel Fault east of the bifurcation, resulting in total right separation of 34-35 km northwest of the bifurcation. Clast sizes and lithologies in Saugus Formation deformed alluvial fan deposits in the Gold and Little Tujunga Canyons area indicate that alluvial stream flow was from the north or north-northeast. The alluvial fan complex is beheaded at the San Gabriel Fault Zone, and no correlative deposits have been found north of the fault zone. Likely sources of several distinctive clast types are east of the bifurcation and north of the Vasquez Creek Fault. Combining these data with right slip caused by the 34 deg +-6 deg of clockwise local block rotation suggests that post-Saugus Formation (<2.6 to 0.78 Ma) right separation along the fault zone is 4+-2 km. The fossils, lithology, and age of the Gold Canyon beds correlate with the basal Pico Formation. The beds presumably connected southward or southwestward to a more open marine setting. A search for correlative strata to the south and southwest found that some strata previously mapped as Towsley Formation correlate with the Modelo Formation. Oyster spat in some Modelo Formation beds are the first recorded fossil occurrences and are especially remarkable because of associations with Miocene bathyal benthic foraminifers, planktonic calcareous nannofossils, and diatoms. Topanga Group basalt resting on basement rocks between Little and Big Tujunga Canyons gives an age of 16.14+-0.05 Ma from 40Ar/39Ar analysis. Improved understanding of the upper Miocene stratigraphy indicates large early movement on the eastern Santa Susana Fault at about 7-6 Ma.

Beyer, Larry A.; McCulloh, Thane H.; Denison, Rodger E.; Morin, Ronald W.; Enrico, Roy J.; Barron, John A.; Fleck, Robert J.

2009-01-01

313

Geochronology of clasts in allochthonous Miocene sedimentary sequences on Mykonos and Paros Islands: implications for back-arc extension in the Aegean Sea  

Microsoft Academic Search

In the Cyclades, low-angle normal faults juxtaposed Miocene sedimentary rock units lying over Alpine blueschist- and greenschist-facies metamorphic rocks and Miocene granites. The sedimentary units in the hanging wall were deposited in fault-bounded basins while their footwalls progressively emerged through the ductile and brittle crust. The sedimentation in the basins evolved from marine turbidites in the Early Miocene to shallow\\/

M. SANCHEZ-GOMEZ; D. AVIGAD; A. HEIMANN

2002-01-01

314

The Middle Miocene climatic transition in the Southern Ocean: Evidence of paleoclimatic and hydrographic changes at Kerguelen plateau from planktonic foraminifers and stable isotopes  

Microsoft Academic Search

Middle Miocene (14.8–11.9 Ma) deep-sea sediments from ODP Hole 747A (Kerguelen Plateau, southern Indian Ocean) contain abundant, well-preserved and diverse planktonic foraminiferal assemblages. A detailed study of the climatic and hydrographic changes that occurred in this region during the Middle Miocene Climatic Transition led to the identification of an intense cooling phase (the Middle Miocene Shift). Abundance fluctuations of planktonic foraminiferal

M. Verducci; L. M. Foresi; G. H. Scott; M. Sprovieri; F. Lirer; N. Pelosi

2009-01-01

315

Paleo-environment in the upper amazon basin during early to middle Miocene times  

NASA Astrophysics Data System (ADS)

The Amazon River has the largest catchment in the world and is responsible for the largest water discharge from land to the ocean. The river system that flows from the Andes to the Atlantic Equatorial Margin exists since the late Miocene, and results from Andean uplift which strongly affected erosion/deposition and major flow patterns in northern South-America. Two outcrop sites from the Solimões basin, Mariñame (17.7-16.1 Ma) and Los Chorros (14.2-12.7 Ma), may shed light on the inland paleo-environmental conditions during a period of active Andean uplift in the early to middle Miocene. Earlier works revealed the Mariñame outcrops to represent a river born in Amazonia. Instead the Los Chorros outcrops are relics of the Amazon River system, characterized by extensive wetlands consisting of swamps, shallow lakes, crevasse splays channels and crevasse-delta lakes (e.g. Hoorn et al., 2010). The freshwater ecosystems alternate with some intervals that are rich in marine palynomorphs (such as dinocysts), mangrove pollen, brackish tolerant molluscs and ostracods, which indicate brackish conditions and a marine influence. It is thought that these marine incursion are related to phases of global sea-level rise and rapid subsidence in the Andean foreland (Marshall & Lundberg, 1996). Still, much remains unknown about the Miocene river systems, like the extent and diversity of the wetland system and the nature of the marine incursions. To get a better understanding of the sources of the (in)organic material, geochemical methods were used. Strontium (Sr) and Neodymium (Nd) isotopes were analyzed on bulk sediments, and used for a paleo-provenance study. The Sr and Nd isotopic signature in the older section (Mariñame) is in general more radiogenic compared to the Los Chorros section. The most radiogenic values are comparable to those found nowadays in the the Precambrian Guyana shield. A Guyana sediment source would suggest a distinctly different flow direction of the major rivers during early-middle Miocene. The younger Los Chorros sediments show Sr and Nd values comparable to those nowadays found in the Solimões region, indicating an Andean source existed already during early-middle Miocene times. Lipid biomarkers were identified and quantified and carbon isotopic compositions of organic matter for whole samples were determined to identify the sources of organic matter. Ratio's between typically terrestrial and aquatic GDGTs indicate shifts between more terrestrial settings and more aquatic settings. Intervals which suggest a more aquatic setting often contain marine palynomorphs and thus could result from a marine incursion at the time. Changes in the overall composition of biomarker lipids at each site reflects the diversity and dynamic features of the wetland. Differences in both provenance and biomarker composition between the two sites demonstrate the diversity within the basin. This diversity could either be geographical diversity since the two sites are located about 380 km from each other. Or, considering the differences in age between the two sites of 2-5 Myrs, it could also reflect the fast changing environmental conditions as a result of Andean uplift. Hoorn, C. et al (2010). The Development of the Amazonian Mega-Wetland (Miocene; Brazil, Colombia, Peru, Bolivia). In: C. Hoorn and F. Wesselingh (eds) Amazonia: Landscape and Species Evolution: A look into the past. Wiley-Blackwell Publishing Ltd., pp. 123- 142. Marshall, L.G., Lundberg, J.G. (1996) Miocene deposits in the Amazonian Foreland Basin. Science 273, 123-124.

van Soelen, Els; Hoorn, Carina; Santos, Roberto V.; Dantas, Elton L.; Sinninghe Damsté, Jaap S.; Kim, Jung-Hyun

2014-05-01

316

Evidence for Late Oligocene-Early Miocene episode of transtension along San Andreas Fault system in central California  

SciTech Connect

The San Andreas is one of the most intensely studied fault systems in the world, but many aspects of its kinematic history remain controversial. For example, the period from the late Eocene to early Miocene is widely believed to have been a time of negligible strike-slip movement along the San Andreas fault proper, based on the rough similarity of offset of the Eocene Butano-Point of rocks Submarine Fan, the early Miocene Pinnacles-Neenach volcanic center, and an early Miocene shoreline in the northern Gabilan Range and San Emigdio Mountains. Nonetheless, evidence indicates that a late Oligocene-early Miocene episode of transtension, or strike-slip motion with a component of extension, occurred within the San Andreas fault system. The evidence includes: (1) about 22-24 Ma, widespread, synchronous volcanic activity occurred at about 12 volcanic centers along a 400-km long segment of the central California coast; (2) most of these volcanic centers are located along faults of the San Andreas system, including the San Andreas fault proper, the San Gregorio-Hosgri fault, and the Zayante-Vergeles fault, suggesting that these and other faults were active and served as conduits for magmas rising from below; (3) during the late Oligocene and early Miocene, a pull-apart basin developed adjacent to the San Andreas fault proper in the La Honda basin near Santa Cruz; and (4) during the late Oligocene and early Miocene, active faulting, rapid subsidence, and marine transgression occurred in the La Honda and other sedimentary basins in central California. The amount of right-lateral displacement along the San Andreas fault proper during this transtentional episode is unknown but was probably about 7.5-35 km, based on model studies of pull-apart basin formation. This small amount of movement is well within the range of error in published estimates of the offset of the Eocene to early Miocene geologic features noted.

Stanley, R.G.

1986-04-01

317

Late cenozoic evolution of Fortymile Ash: Major change in drainage pattern in the Yucca Mountain, Nevada region during late miocene volcanism  

SciTech Connect

Analysis of sedimentary provenance and altitude distribution of volcanic strata along Fortymile Wash, the primary desert wash east of Yucca Mountain, NV, indicates a major change in surface drainage basins related to late Miocene volcanic disruption. This event resulted in the establishment of the modern Fortymile Wash basin before 3 Ma, and probably by latest Miocene time. An understanding of this event is useful for evaluation of extensive alluviation east of Yucca Mountain and its relation to paleoclimate, hydrology and tectonics. To the northeast of Yucca Mountain, Fortymile Wash provides southward surface drainage from 60% of the area of the 11 Ma Timber Mountain caldera via Fortymile Canyon, a major breach in the caldera wall. In the southeast caldera moat, the distribution of volcanic units that predate and include the 9.4 Ma Thirsty Canyon Group and the characteristics of intercalated sediments indicate a northward paleoslope and sediment transport from a major drainage divide near Dome Mountain, a shield volcano now deeply incised by Fortymile Canyon. Eruption of the Thirsty Canyon Group from the Black Mountain area, 10 km northwest of the Timber Mountain caldera, is likely to have dammed a counterclockwise drainage system of the east moat. Following drainage disruption, the east moat filled with sediment up to the level of a new southward outlet at the saddle between Dome Mountain and the onlapping rhyolite of Shoshone Mountain. An older canyon south of this saddle received the overflow from the east moat and became the throughgoing Fortymile Canyon, integrating the east moat basin with a lower base level in Jackass Flats. Well-integrated southward drainage existed by the time the trachybasalt flows of Buckboard Mesa (2.8 Ma) were emplaced, because basal elevations of these flows slope southward about 100 m above modern Fortymile Wash.

Lundstrom, S.C. [Geological Survey, Las Vegas, NV (United States); Warren, R.G. [Los Alamos National Lab., NM (United States)

1994-12-31

318

S concentrations and its speciation in Miocene basaltic magmas north and south of Gran Canaria (Canary Islands): constraints from glass inclusions in olivine and clinopyroxene  

NASA Astrophysics Data System (ADS)

We report S concentrations and relative proportions of SO 42- and S 2- in OL- and CPX-hosted glass inclusions and in host glassy lapilli from Miocene basaltic hyaloclastites drilled north and south of Gran Canaria during ODP Leg 157. Compositions of glass inclusions and lapilli resemble those of subaerial Miocene shield basalts on Gran Canaria and comprise mafic to more evolved tholeiitic to alkali basalt and basanite (10.3-3.7 wt.% MgO, 44.5-56.9 wt.% SiO 2). Glass inclusions fall into three groups based on their S concentrations: a high-sulfur group (1050 to 5810 ppm S), an intermediate-sulfur group (510 to 1740 ppm S), and a low-sulfur group (<500 ppm S). The most S-rich inclusions have the highest and nearly constant proportion of sulfur dissolved as sulfate determined by electron microprobe measurements of S K? peak shift. Their average S 6+/S total value is 0.75 ± 0.09, unusually high for ocean island basalt magmas. The low-sulfur group inclusions have low S 6+/S total ratios (0.08 ± 0.05), whereas intermediate sulfur group inclusions show a wide range of S 6+/S total (0.05-0.83). Glassy lapilli and their crystal-hosted glass inclusions with S concentrations of 50 to 1140 ppm S have very similar S 6+/S total ratios of 0.36 ± 0.06 implying that sulfur degassing does not affect the proportion of SO 42- and S 2- in the magma. The oxygen fugacities estimated from S 6+/S total ratios and from Fe 3+/Fe 2+ ratios in spinel inclusions range from NNO-1.1 to NNO+1.8. The origin of S-rich magmas is unclear. We discuss (1) partial melting of a mantle source at relatively oxidized fO 2 conditions, and (2) magma contamination by seawater either directly or through magma interaction with seawater-altered Jurassic oceanic crust. The intermediate sulfur group inclusions represent undegassed or slightly degassed magmas similar to submarine OIB glasses, whereas the low-sulfur group inclusions are likely to have formed from magmas significantly degassed in near-surface reservoirs. Mixing of these degassed magmas with stored volatile-rich ones or volatile-rich magma replenishing the chamber filled by partially degassed magmas may produce hybrid melts with strongly varying S concentrations and S 6+/S total ratios.

Gurenko, Andrey A.; Schmincke, Hans-Ulrich

2000-07-01

319

Middle to late Miocene canyon cutting on the New Jersey continental slope: biostratigraphic and seismic stratigraphic evidence  

SciTech Connect

The authors have identified and dated a major Miocene erosional surface (M1) on the New Jersey continental slope. This surface was penetrated at Deep Sea Drilling Project (DSDP) Site 612, which was drilled near the thalweg of a buried V-shaped canyon. Biostratigraphic data at Site 612 firmly constrain the age of strata above the buried canyon surface as Zones CN7 (N=NN9) and N16 (lowermost upper Miocene); the upper Miocene surface at Site 612 lies above lowermost Oligocene strata because of coalesced unconformities. The authors traced the M1 erosional surface to the COST B-3 well where upper middle Miocene strata underlie it. Biostratigraphic studies of other New Jersey continental slope boreholes (ASP 14, ASP 15) suggest that elsewhere the sediments immediately below the M1 surface encompass the Globorotalia fohsi robusta Zone (=Zone N12-earliest N13; middle middle Miocene). The best age estimate is that M1 was eroded between 11.5 and 10.0 Ma. This erosional event apparently correlates with a similar even on the Irish and Florida continental margins and with oxygen-isotope evidence for a glacio-eustatic lowering.

Miller, K.G.; Melillo, A.J.; Mountain, G.S.; Farre, J.A.; Poag, C.W.

1987-06-01

320

A drastic lower Miocene regolith evolution triggered by post obduction slab break-off and uplift in New Caledonia  

NASA Astrophysics Data System (ADS)

lower Miocene coarse conglomerate that crops out in the Népoui Peninsula does not represent the base of the marine transgression that followed obduction in New Caledonia. Instead, the conglomeratic alluvial fan that contains peridotite cobbles and reworked weathering products records a short-lived episode of terrestrial erosion intercalated between two intervals of subsidence marked by marine carbonate deposition. Considering the Miocene sea level evolution reported in the literature, it is concluded that neither lower Miocene transgression nor erosion were driven by sea level variation. In contrast, a southeastward propagating slab tear that initiated at the latitude of the high pressure/low temperature metamorphic complex of northern New Caledonia likely generated east to west tilting of New Caledonia, subsidence along the West Coast and hence fringing reef development together with moderate erosion of older regolith. Coincidence between conglomerate deposition and hence prominent erosion that closely followed emplacement of postobduction granitoids influenced by a slab window suggests a genetic link. Therefore, it is concluded that short-lived lower Miocene erosion was due to slab breakoff and subsequent uplift that occurred at ~ 22 Ma. Lower Miocene erosion profoundly dissected the Peridotite Nappe and in the northern half of New Caledonia only left isolated klippes along the West Coast.

Sevin, Brice; Cluzel, Dominique; Maurizot, Pierre; Ricordel-Prognon, Caroline; Chaproniere, George; Folcher, Nicolas; Quesnel, Florence

2014-09-01

321

The Owen Ridge uplift in the Arabian Sea: Implications for the sedimentary record of Indian monsoon in Late Miocene  

NASA Astrophysics Data System (ADS)

The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the previously unidentified Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drilling to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ˜8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ˜8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

Rodriguez, Mathieu; Chamot-Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

2014-05-01

322

The Owen Ridge uplift in the Arabian Sea: implications for the sedimentary record of Indian monsoon in Late Miocene  

NASA Astrophysics Data System (ADS)

The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the unidentified fossil Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drillings to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ~8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ~8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

Rodriguez, Mathieu; Chamot Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

2014-05-01

323

The incrementally zoned Miocene Ayagaures ignimbrite (Gran Canaria, Canary Islands)  

NASA Astrophysics Data System (ADS)

The 20-25 m thick trachyphonolitic Ayagaures ignimbrite cooling unit [(AY); 11.8 Ma] exposed over 250 km 2 (onshore volume ca. 4.5 km 3 DRE) is the uppermost and most voluminous cooling unit of the Middle Fataga Formation (MFF), part of the Fataga Group (ca. 13.3-ca. 9 Ma) on Gran Canaria (GC), Canary Islands (28°00' N, 15°35' W). Up to 19 flow units (named b-t) subdividing the AY have been identified throughout most of the area from proximally to the caldera wall to distally as far as 14 km away. Individual flow units were distinguished from each other and logged using mainly chemical criteria. Single and/or packages of flow units (A, B and C) are tentatively interpreted to correspond to compositionally distinct magma bodies erupted from the same magma reservoir. These source-controlled flow units are interpreted to reflect successive eruptive pulses during incremental subsidence of Tejeda caldera. We subdivided AY cooling unit into four welding facies. Tentative correlation with a major syn-ignimbrite turbidite drilled during ODP Leg 157 suggests a total DRE volume of > 50 km 3. The cooling unit as a whole becomes less evolved upwards as shown by major elements, trace elements and REE of bulk rock and phenocrysts. All phenocryst phases, dominantly sanidine-anorthoclase (up to 20 vol.%), with minor biotite, augite, titanite, haüyne and apatite, are unzoned and show an incremental compositional zoning in the stratigraphy. The shallow level parent magma reservoir is interpreted to have undergone strong mixing prior to starting its final compositional zoning in a thermodynamically equilibrated reservoir. Compositional zoning resulted in three main bodies. This compositional and physical layering may have been triggered by rapid growth of alkali feldspar and biotite throughout the erupted part of the magma chamber. Abundant titanite and haüyne phenocrysts in basal flow units and in a locally preserved, highly evolved fallout tephra are interpreted to reflect initial evacuation of a small volume, highly fractionated cupola. AY represents the most evolved part of a large, partially evacuated magma reservoir. Progressive downward tapping of the reservoir is interpreted to have been controlled by incremental caldera collapse. Absence of less evolved magmas suggests that the magma chamber was only partially evacuated. Incremental compositional zoning of the cooling unit, but unzoned phenocrysts and evacuation reversals show that mixing did not occur following initiation of alkali feldspar growth.

Jutzeler, Martin; Schmincke, Hans-Ulrich; Sumita, Mari

2010-09-01

324

New primate carpal bones from Rudabánya (late Miocene, Hungary): taxonomic and functional implications.  

PubMed

We describe a scaphoid and two capitates from the late Miocene site of Rudabánya, Hungary using qualitative and quantitative comparisons to a large sample of hominoid, cercopithecoid, and platyrrhine primates. The scaphoid (RUD 202) is not fused to the os centrale and in this way is like most primates other than African apes and humans (hominines). Qualitatively, its morphology is most similar to Pongo, and univariate analyses generally confirm an ape-like morphology with an increased range of mobility. One capitate (RUD 167) is compatible in size to the scaphoid, and its morphology suggests a combination of monkey-like generalized arboreality and ape-like enhanced mobility. RUD 203 is a smaller, fragmentary capitate, about half the size of RUD 167, and preserves only the distal portion of the body with the third metacarpal articular surface. Its morphology is virtually identical to that of RUD 167, and an exact randomization test revealed that it is statistically likely to find two carpal bones of such disparate sizes within one taxon. However, due to morphological similarities with other Miocene hominoids as well as implications for size variation within one taxon and sex, we consider the taxonomic affiliation of RUD 203 to be unresolved. We attribute the scaphoid and RUD 167 capitate to the hominine Rudapithecus hungaricus (formerly Dryopithecus brancoi; see Begun et al., 2008) based on overall morphological similarity to extant apes, particularly Pongo, and not to the pliopithecoid Anapithecus hernyaki, the only other primate known from Rudabánya. The similarities in carpal morphology to suspensory taxa are consistent with previous interpretations of Rudapithecus positional behavior. The scaphoid and the RUD 167 capitate are consistent in size with a partial skeleton including associated postcranial and craniodental specimens from the same level at the locality and may be from the same individual. These are the first carpal bones described from Rudabánya and from this taxon, and they add to our understanding of the evolution of arboreal locomotion in late Miocene apes. PMID:19709719

Kivell, Tracy L; Begun, David R

2009-12-01

325

Coarse-grained deltaic sedimentation in the Miocene Cuyama strike-slip basin, California coast ranges  

SciTech Connect

The Cuyama basin, located in the southern Coast Ranges southwest of the San Andreas fault developed early in the history of the San Andreas transform system. The Miocene marine basin formed in a transtensional setting along a dextral strike-slip fault of the transform system, the San Juan-Chimineas fault following Oligocene nonmarine basin formation in an extensional setting. The lower and middle Miocene Vaqueros Formation in the northwestern part of the basin, which represents the first of two transgressive-regressive cycles, consists of eight facies making up two depositional systems. The 400-m-thick Soda Lake Shale Member constitutes a basinal system consisting of deep-basin and starved-basin facies. The overlying 2,200-m-thick Painted Rock Sandstone Member consists mostly of coarse-grained, pebbly sandstone and constitutes a deltaic depositional system of prodelta, slope channel, delta front, tidal channel, interdistributary bay, and fluvial channel facies. The basinal depositional system consists of turbidite sand and mud, and hemipelagic and pelagic sediments that were deposited in a rapidly subsiding basin. The deltaic depositional system prograded into the deep basin and had a steep prodelta slope that extended to bathyal depths. The delta is inferred to be a river-dominated fan delta in which coarse sediment was transported down the prodelta slope into deep water by sediment gravity flows. The overall basin history and geometry of the northwestern Cuyama basin are typical of strike-slip basins. The initial rapid subsidence to bathyal depths at rates of more than 500 m/m.y. in the early Miocene is interpreted to be a result of extension at the releasing bend of a dextral strike-slip fault.

Bartow, J.A. (Geological Survey, Menlo Park, CA (USA))

1990-05-01

326

Late Miocene decoupling of oceanic warmth and atmospheric carbon dioxide forcing.  

PubMed

Deep-time palaeoclimate studies are vitally important for developing a complete understanding of climate responses to changes in the atmospheric carbon dioxide concentration (that is, the atmospheric partial pressure of CO(2), p(co(2))). Although past studies have explored these responses during portions of the Cenozoic era (the most recent 65.5 million years (Myr) of Earth history), comparatively little is known about the climate of the late Miocene (?12-5 Myr ago), an interval with p(co(2)) values of only 200-350?parts per million by volume but nearly ice-free conditions in the Northern Hemisphere and warmer-than-modern temperatures on the continents. Here we present quantitative geochemical sea surface temperature estimates from the Miocene mid-latitude North Pacific Ocean, and show that oceanic warmth persisted throughout the interval of low p(co(2)) ?12-5 Myr ago. We also present new stable isotope measurements from the western equatorial Pacific that, in conjunction with previously published data, reveal a long-term trend of thermocline shoaling in the equatorial Pacific since ?13?Myr ago. We propose that a relatively deep global thermocline, reductions in low-latitude gradients in sea surface temperature, and cloud and water vapour feedbacks may help to explain the warmth of the late Miocene. Additional shoaling of the thermocline after 5?Myr ago probably explains the stronger coupling between p(co(2)), sea surface temperatures and climate that is characteristic of the more recent Pliocene and Pleistocene epochs. PMID:22678287

LaRiviere, Jonathan P; Ravelo, A Christina; Crimmins, Allison; Dekens, Petra S; Ford, Heather L; Lyle, Mitch; Wara, Michael W

2012-06-01

327

Rapid syn-convergent Exhumation of Miocene-aged Lower Orogenic Crust in the Eastern Himalaya  

NASA Astrophysics Data System (ADS)

Rare granulitized eclogites exposed in the eastern Himalaya provide an insight into conditions and processes deep within the orogen. SHRIMP U-Pb, Ti and REE data from zircons in mafic granulitized eclogites located in the upper structural levels of the GHS in Bhutan show that zircon crystallized under eclogite facies metamorphic conditions, between 15.3 ± 0.3 and 14.4 ± 0.3 Ma, within a couple of million years of the later granulite-facies overprint. In conjunction with pressure estimates of the eclogite and granulite facies stages of metamorphism, the age data suggest that initial exhumation occurred at plate tectonic rates (cm yr-1). These extremely rapid syn-convergence exhumation rates during the later stages of the India-Asia collision require a revision of theories about how crustal materials are transported and exhumed during continental collisions. In contrast to western Himalayan examples, the eastern Himalayan eclogites cannot be tectonically related to steep subduction of India beneath Asia. Instead, they more likely represent fragments from the base of the over-thickened Tibetan crust. Based on the zircon age and trace element data we hypothesize that the protolith of the mafic granulites are Middle Miocene mafic intrusions into the lower crust of southern Tibet, linked to the Miocene volcanism in the Lhasa block. We suggest that a transient tectonic event, possibly the indenting of a strong Indian crustal ramp into crust under southern Tibet weakened by partial melting, may have promoted exhumation of the eclogitized lower crust under Tibet. Mafic magmatism and volcanism themselves may be related to the convective thinning of the lithospheric mantle triggered by the reduction in India-Eurasia convergence rate during the Middle Miocene, which in turn could have helped the rapid extrusion of the lower crust over the earlier exhumed middle crust.

Grujic, D.; Warren, C. J.; Wooden, J. L.

2011-12-01

328

Small mammal carbon isotope ecology across the Miocene-Pliocene boundary, northwestern Argentina  

NASA Astrophysics Data System (ADS)

The late Miocene expansion of plants using the C4 photosynthetic pathway in South America has been documented by tooth enamel carbon isotope ratios (?13Cen). However, a more detailed understanding of this ecological event is hampered by poor chronological control on the widespread fossil localities from which isotopic data are derived. This study develops a ?13Cen record from a single 2500 m-thick stratigraphic section in subtropical South America. Strata at Puerta de Corral Quemado (PCQ), northwestern Argentina, span 9 to 3.5 Ma in age, and existing paleosol carbonate data (?13Cpc) document C4 expansion across the Miocene-Pliocene boundary. Comparison of ?13Cen data with ?13Cpc data at high stratigraphic resolution refines understanding of this ecological event in South America. Small mammal ?13Cen data in particular are complementary to that of large mammal and paleosol ?13C data. Small mammal teeth integrate isotopic data over much shorter temporal and spatial scales than large mammal teeth, providing a sensitive measure of local vegetation and placing constraints on the landscape distribution of C3 and C4 plants. Explicit consideration of the distinctive carbon isotope enrichment factor between enamel and diet for rodents (?*en-diet = 11‰, as opposed to 14‰ for large mammals) allows for unequivocal inference of C4 vegetation ~ 1 Ma prior to that inferred from large mammal ?13Cen data, and ~ 2 Ma prior to ?13Cpc data. This multiproxy record demonstrates that C4 plants were a stable component of the ecosystem hundreds of thousands of years prior to their major ecological expansion, and that the expansion of C4 plants was pulsed at PCQ. Two periods of ecological change are demonstrated by ?13C and ?18O data at ~ 7 Ma and 5.3 Ma (coincident with the Miocene-Pliocene boundary). Development of small mammal ?13Cen records on other continents may provide similar insight into the early stages of the global C4 event.

Hynek, Scott A.; Passey, Benjamin H.; Prado, José Luis; Brown, Francis H.; Cerling, Thure E.; Quade, Jay

2012-03-01

329

Atmosphere, ecology and evolution: what drove the Miocene expansion of C4 grasslands?  

PubMed Central

Grasses using the C4 photosynthetic pathway dominate today's savanna ecosystems and account for ?20% of terrestrial carbon fixation. However, this dominant status was reached only recently, during a period of C4 grassland expansion in the Late Miocene and Early Pliocene (4–8 Myr ago). Declining atmospheric CO2 has long been considered the key driver of this event, but new geological evidence casts doubt on the idea, forcing a reconsideration of the environmental cues for C4 plant success. Here, I evaluate the current hypotheses and debate in this field, beginning with a discussion of the role of CO2 in the evolutionary origins, rather than expansion, of C4 grasses. Atmospheric CO2 starvation is a plausible selection agent for the C4 pathway, but a time gap of around 10 Myr remains between major decreases in CO2 during the Oligocene, and the earliest current evidence of C4 plants. An emerging ecological perspective explains the Miocene expansion of C4 grasslands via changes in climatic seasonality and the occurrence of fire. However, the climatic drivers of this event are debated and may vary among geographical regions. Uncertainty in these areas could be reduced significantly by new directions in ecological research, especially the discovery that grass species richness along rainfall gradients shows contrasting patterns in different C4 clades. By re-evaluating a published data set, I show that increasing seasonality of rainfall is linked to changes in the relative abundance of the major C4 grass clades Paniceae and Andropogoneae. I propose that the explicit inclusion of these ecological patterns would significantly strengthen climate change hypotheses of Miocene C4 grassland expansion. Critically, they allow a new series of testable predictions to be made about the fossil record. Synthesis. This paper offers a novel framework for integrating modern ecological patterns into theories about the geological history of C4 plants. PMID:18784799

Osborne, Colin P

2008-01-01

330

Miocene-Quaternary structural evolution of the Uyuni-Atacama region, Andes of Chile and Bolivia  

NASA Astrophysics Data System (ADS)

We describe the Miocene-Quaternary geological-structural evolution of the region between the Salar de Uyuni and de Atacama, Andes of Chile and Bolivia. We recognized four main tectonic events based on fold geometry, fault kinematics and stratigraphic data. The oldest event, of Miocene age, is characterized by folding and reverse faulting of the sedimentary successions with an E-W direction of shortening in the northern part of the studied area and a WNW-ESE shortening in the southern part. The following two events, of Pliocene age, are characterized by lower shortening amounts; they occurred first by reverse faulting with a NW-SE-trending greatest principal stress ( ?1, computed with striated fault planes) and a vertical least principal stress ( ?3), followed by pervasive strike-slip faulting with the same NW-SE-trending ?1 and a horizontal NE-SW ?3. The fourth event, dating to the late Pliocene-Quaternary is characterized by normal faulting: the ?3 still trends NE-SW, whereas the intermediate principal stress ?2 exchanged with ?1. Volcanism accompanied both the contractional, transcurrent and extensional tectonic phases. The Mio-Pliocene compression appears directly linked to a rapid convergence and an apparently important coupling between the continental and oceanic plates. The E-W to WNW-ESE direction of shortening of the Miocene structures and the NW-SE ?1 of the Pliocene structures seem to be more linked to an intra-Andean re-orientation of structures following the WNW-directed absolute motion of the South-American Plate. The extensional deformations can be interpreted as related to gravity forces affecting the highest parts of the volcanic belt in a sort of asymmetrical (SW-ward) collapse of the belt.

Tibaldi, A.; Corazzato, C.; Rovida, A.

2009-06-01

331

Model study of the Miocene Mediterranean Sea and Paratethys: closure of the Indian gateway  

NASA Astrophysics Data System (ADS)

The proto-Mediterranean Sea and Paratethys were both connected to the Indian Ocean until the Middle Miocene, when the convergence of the Eurasian plate and African-Arabian plate caused the constriction and closure of the Indian gateway. This interrupted the water exchange with the Indian Ocean and gave birth to the present-day Mediterranean basin. Although there are lots of uncertainties concerning the timing of the closure and the consequences that this entailed, it is broadly accepted that it had had a large effect on water properties and ocean dynamics on the regional and global scales, and in that way may have also played a role in the evolution of climate. While, from a modeling perspective, considerable research has been devoted to the Late Miocene period on the Mediterranean region, rather less attention has been paid to the Early and Middle Miocene. The purpose of this work is to investigate the palaeocirculation of the Mediterranean Sea and Paratethys during the different stages of closure. For this purpose we use of a regional ocean model and a Burdigalian (about 20 Ma) palaeogeographic map from the Peri-Tethys Atlas. In the interest of gaining insight into the first-order effects of the gateway evolution on marine circulation, different experiments, ranging from a deep gateway to a completely closed one, have been carried out. In addition, different sets of values for the atmospheric forcing have been applied in order to understand the role of the temperature and net evaporation on the marine circulation and the strait dynamics. The series of experiments allows us to analyze different scenarios, helping us to understand the evolution of such a complex system, and sheds a new light on the interpretation of the sedimentary record. Consequently, the information derived from this work can be useful for other studies focused on strait dynamics and could be a valid starting point for subsequent research on this gateway.

de la Vara Fernandez, Alba; Meijer, Paul Th.; Wortel, Rinus M. J.

2013-04-01

332

Provenance of the upper Miocene-Pliocene red clay deposits of the Chinese Loess Plateau  

NASA Astrophysics Data System (ADS)

A clear understanding of the provenance of late Cenozoic Chinese loess and the underlying red-clay deposits will shed light on the history and mechanisms of Asian aridification. Although much progress has been made in understanding the source of Quaternary loess in the Chinese Loess Plateau (CLP), the provenance of the underlying upper Miocene-Pliocene red-clay sequence is largely unknown. Here we present a provenance history of the red-clay sequence based on zircon U-Pb ages from the central CLP. Non-metric multi-dimensional scaling (MDS) statistical analyses of the U-Pb age populations allow clear identification of sediment source trends and reveal that the red-clay deposited during 5.5-3 Ma has a western Kunlun provenance, suggesting that the distal Taklimakan desert was the principal source and that dusts were transported to the CLP via westerly winds. By contrast, late Quaternary loess appears to have source signatures from more proximal regions such as NE Tibet, West Mu Us desert, and Qaidam desert, as well as the Yellow River and distal Taklimakan desert, suggesting that dusts were transported to the CLP via winter monsoon, the Yellow River, and westerly winds. Furthermore, MDS analyses reveal that the East Mu Us desert is less likely to be major source region for the CLP during the past 8 Ma. These results demonstrate that 1) Asian desertification has a pattern of eastward expansion since the late Miocene and 2) the provenance shift from the upper Miocene-Pliocene red-clay to the late Quaternary loess is associated with formation of the proximal deserts and Yellow River.

Nie, J.; Stevens, T.; Song, Y.; Moeller, A.; Stockli, D. F.; Horton, B. K.; Fang, X.

2013-12-01

333

Climate aberrations during the middle Miocene: evidence from the eastern North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

During the Middle Miocene Climatic Optimum (MMCO; 17-14.5 Ma) the relatively warm climate of the Miocene reached peak temperatures. After the MMCO, the global climate started cooling through several short-lived cooling events, represented by positive oxygen isotope excursions: the Mi-events (Miocene isotope events). One of the more severe events, Mi-3, is associated with East Antarctic Ice Sheet growth and potential Northern Hemisphere ice expansion, as well as marine and terrestrial species turnover and aridification. The causes and consequences of the Mi-events are not well constrained yet. CO2 reconstructions combined with the abovementioned consequences suggest that a drawdown of CO2 and/or changes in ocean led to the changes surrounding Mi-3. A minimum node in both eccentricity and obliquity amplitude modulation, an orbital configuration creating favourable conditions for ice growth, has been suggested as a possible triggering mechanism as well. However, an exact cause cannot be pinpointed yet and more high-resolution records are needed in order to investigate the impact and order of events surrounding the Mi-events. Integrated Ocean Drilling Program (IODP) Leg 307 recovered such a high resolution record from the middle Miocene of the Porcupine Basin (offshore south-western Ireland). We have analyzed well-preserved palynomorphs (mainly organic-walled dinoflagellate cysts, acritarchs and pollen) and organic molecules for paleothermometry (e.g. TEX86 and UK'37) from site U1318. With these proxies, the development of the Mi-3 event and following Mi-4 have been reconstructed in high resolution (ca. 13 kyr), by assessing e.g. temperature, sea level, thermocline depth and productivity. A pronounced cooling can be observed at Mi-3, and to a lesser degree in Mi-4 as well, together with a sea-level fall and a turnover in the dinocyst record. Our findings also include indications of aridification and a change in wind patterns during Mi-3. This confirms the dramatic impact of the Mi-3 event, not only on the North Atlantic Ocean, but also on the continent.

Quaijtaal, W.; Donders, T.; Schouten, S.; Louwye, S.

2013-12-01

334

Skull and skeleton of a mustelid, Brachypsalis, from the Miocene of northeastern Colorado  

E-print Network

of Brachypsalis modi- 2.—Parts of postcranial skeleton of Gulo luscus (LIN- cus MATTHEW 3 NAEUS ) and Brachypsalis modicus MArniEw.. 7 ABSTRACT Skull, jaw and parts of the postcranial skeleton of Brachypsalis modicus MArrHEw from ?upper Miocene deposits... by their generic names alone are to the following named species: Canis latrans SAY ( for example, adult, no. 156-361); Procyon lotor (LuszNAEus ) (young and adult specimens); Gulo luscus (LaNNAEus) ( skull of adult; skeleton otherwise of young to subadult and adult...

Galbreath, E. C.

1955-01-01

335

Genetic stratigraphy of a part of the Miocene Congo Fan, West Africa  

NASA Astrophysics Data System (ADS)

The stratigraphic framework and reservoir distribution are essential factors controlling the accumulation of petroleum in the Miocene Congo Fan. Analysis of cores, well logs, and seismic data suggest that the submarine fan autocycle (genetic cycle) is presented by sequence of slump, debrite, densite currents, and turbidites, whereas allocycles (long-term cycles) may be composed of several autocycles (short-term cycles) that, appear as a stacking pattern or retrogradational fan. Scour surfaces at the base of gravity flow channel, stable hemipelagic mudstone section, and the surface between fan retrogradation and progradation can be used for the correlations.

Jiang, Zhenglong; Wang, Rong; Zheng, Wenbo

2014-07-01

336

Widespread Miocene deep-sea hiatuses: Coincidence with periods of global cooling  

Microsoft Academic Search

High-resolution biostratigraphic analyses of Miocene deep-sea cores reveal eight intervals of widespread hiatuses in the world ocean at 23.0 22.5, 20.0 18.0, 16.0 15.0, 13.5 12.5, 12.0 11.0, 10.0 9.0, 7.5 6.2, and 5.2 4.7 m.y. ago. In complete sections these hiatuses correspond to intervals of cool faunal and floral assemblages, rapid enrichment of delta18O, and sea-level regressions. These factors

John A. Barron; Gerta Keller

1982-01-01

337

New constrains on the thermal history of the Miocene Jarando basin (Southern Serbia)  

NASA Astrophysics Data System (ADS)

The Jarando basin, located in the internal Dinarides, formed in the course of the Miocene extension affecting the whole Alpine-Carpathian-Dinaride system (Schmid et al., 2008). In the study area Miocene extension led to the formation of a core-complex in the Kopaonik area (Schefer et al., 2011) with the Jarando basin located in the hanging wall of the detachment fault. The Jarando basin is characterized by the presence of bituminous coals, whereas in the other intramontane basins in Serbia coalification did not exceed the subbituminous stage within the same stratigraphic level. Furthermore, the basin hosts boron mineralizations (borates and howlite) and a magnesite deposit, which again implies elevated temperatures. This thermal overprint is possibly due to post-magmatic activity related to the emplacement of Oligocene I-type Kopaonik and Miocene S-type Polumir granitoid (Schefer et al., 2011.). This research project is aimed at providing new information about the thermal history of the Jarando basin. Fifteen core samples from three boreholes and 10 samples from the surrounding outcrops were processed for apatite fission-track analysis. Additionally, vitrinite reflectance was measured for 11 core samples of shales from one borehole and 5 samples of coal from an underground mine. VR data of Early to Middle Miocene sediments reveal a strong post-depositional overprint. Values increase with the depth from 0.66-0.79% to 0.83-0.90%. Thus organic matter reached the bituminous stage and experienced temperatures of around 110-120?C (Barker and Pawlewicz, 1994). FT single grain ages for apatite scatter between 45 Ma to 10 Ma with a general trend towards younger ages with depth. Both, the spread in single grain ages together with the bimodal track lengths distribution clearly point to partial annealing of the detrital apatites. With the temperature given from the VR values the partial annealing points to a rather short-lived thermal event. This is assisted by thermal modelling of our fission track data indicating that maximum temperatures of <120°C around 15-12 Ma. We correlate the thermal event with the extension and core-complex formation followed by the syn-extensional intrusion of the Polumir granite. Later cooling from 10 Ma onwards is related to basin inversion and erosion.

Andri?, Nevena; Životi?, Dragana; Fügenschuh, Bernhard; Cvetkovi?, Vladica

2013-04-01

338

Mid-Miocene Silicic Volcanism of the Three Fingers - Mahogany Mountain Area, SE Oregon - Revisited  

NASA Astrophysics Data System (ADS)

Earlier work identified two adjacent caldera systems, the Mahogany Mountain and Three Fingers calderas as the centerpiece of voluminous rhyolitic volcanism on the eastern margin of the Oregon-Idaho graben during the mid-Miocene. Silicic volcanism of Three Fingers-Mahogany Mtn. area is part of the Lake Owyhee volcanic field, Oregon and belongs to widespread rhyolites associated with the Columbia River Basalt province. Here we revisit field evidence and establish relationships between intra-caldera units of Three Fingers and Mahogany Mtn. calderas, and their outflow facies, the tuffs of Spring Creek and Leslie Gulch. In addition, we assess the distribution of entrained mafic clasts and their often anomalously high, nearly ore-grade concentrations of rare earth elements (REE). Previous mapping identified two groups of intra-caldera rhyolite units: 1) intra-caldera tuffs of Spring Creek and Leslie Gulch and 2) younger rhyolite lavas (Trp) within Three Fingers Caldera and cross-cutting rhyolite dikes within the core of Mahogany Mtn. Caldera. Our mapping determines that devitrified Trp of Three Fingers area is equivalent to surrounding often glassy, pumiceous to dense or brecciated rhyolite flows mapped before as intra-caldera tuff of Spring Creek, and all are compositionally indistinguishable from cross-cutting dikes within Mahogany Mtn. Reinterpreted rhyolites of Three Fingers Caldera lack vitroclastic textures and are geochemically distinct from outflow tuff of Spring Creek which in turn can be distinguished from the tuff of Leslie Gulch. Outflow tuff of Spring Creek is Fe-rich, low silica rhyolite (~74 wt.% SiO2, 3 wt.% FeO, ~1600 ppm Ba) as compared to less Fe rich, high-silica rhyolite (~77 wt.% SiO2, 2 wt.% FeO, ~200 ppm Ba) of intra-caldera units. Outflow tuff of Leslie Gulch is also high-silica rhyolite but Ba rich (~1500 ppm). We interpret the investigated Three Fingers area as a rhyolite dome field, erupting subsequent to caldera collapse. There, abundant post-collapse rhyolite volcanism resulted in a complex stratigraphic overlap of rhyolite flows and clastic debris issued from closely-spaced domes. The predominance of high-standing dome interiors reflects the more resistant nature of dense devitrified rhyolite as compared to pumiceous, glassy, or brecciated rhyolite. New 40Ar/39Ar data reveal intra-caldera rhyolites and outflow tuff of Spring Creek to be indistinguishable at 15.64 × 0.08 Ma yet field evidence indicates eruption of post-caldera rhyolites occurred after sedimentation within the caldera. The existence of two outflow tuff units suggests two collapse structures and ages indicate the Mahogany Mtn. Caldera preceded the younger rhyolites by ~200,000 years. Mafic clasts present in dense glassy or porous intra-caldera rhyolites of Three Fingers are reworked fragments of preexisting lava flows that were entrained by subsequent eruptions. Ore-grade REE enrichment of over 2400 ppm Nd in these clasts is likely facilitated by mobilization of REE from earlier rhyolites during renewed rhyolite magmatism and subsequent deposition.

Marcy, P.; Streck, M. J.; Ferns, M.

2013-12-01

339

New primate genus from the Miocene of Argentina Marcelo F. Tejedor, Adn A. Tauber, Alfred L. Rosenberger, Carl C. Swisher, III, and Mara E.  

E-print Network

New primate genus from the Miocene of Argentina Palacios Marcelo F. Tejedor, Adán A. Tauber, Alfred, 2005 (received for review August 4, 2005) Killikaike blakei is a new genus and species of anthropoid of pre-Pleistocene fossil New World anthropoids are exceedingly rare (1­3). Of the five Miocene genera

Rosenberger, Alfred H.

340

Punctuated Evolution of Global Climate Cooling during the late Middle to early Late Miocene: High-Resolution Planktonic Foraminiferal and Oxygen Isotope Records from the Mediterranean  

NASA Astrophysics Data System (ADS)

High-resolution planktonic foraminiferal and oxygen isotope records are presented from a deep marine succession of late Middle to early Late Miocene age in the Mediterranean, dated astronomically between 12.12 and 9.78 Ma. Long-term changes in the faunal composition reflect the overall late Neogene cooling trend. The planktonic and benthic oxygen isotope records are punctuated by two episodes of ? 18O increase, which have astronomical ages of 11.4 and 10.4 Ma and correspond to the Mi5 and Mi6 events of Miller et al. (1991a). The first-order comparison with the astronomical time series for the variations in the tilt of the Earth's axis revealed that these ice growth events coincide with low amplitude variations in the 1.2 myr obliquity cycle. This phase relation is different from that found during the last 5 myr, pointing to a fundamentally different response of the ice sheets to long-term obliquity induced variations in insolation. The inferred global cooling during Mi5 and Mi6 is accompanied by significant faunal changes in the Mediterranean, such as the arrival of neogloboquadrinids, the increase in abundance of the G. apertura-G. obliquus group, and the areal differentiation between N. atlantica and N. acostaensis. Other faunal events, such as the disappearance of P. mayeri and the coiling changes in neogloboquadrinids are not related to these glacial episodes, but may have been controlled by short-term climate fluctuations superimposed on long-term astronomically and/or tectonically induced climate changes. Short-term variations in the planktonic foraminiferal and oxygen isotope records correspond to dominantly precession-controlled sedimentary cycles. The micropaleontological and stable isotopic features of sapropel/grey marl layers are identical to those observed for Late Miocene to Pleistocene sapropels, indicating that the short-term astronomically controlled circum-Mediterranean climate changes remained basically the same over the last 12 myr.

Turco, E.; Hilgen, F. J.; Lourens, L. J.; Shackleton, N. J.; Zachariasse, W. J.; Kruk, R. W.

2001-05-01

341

Correlation of Miocene strata on the submarine St. Croix Ridge and onland St. Croix, US Virgin Islands  

NASA Astrophysics Data System (ADS)

The nannofossils of an hydraulic piston core from the steep scarp between the St. Croix Ridge and Virgin Islands Basin were restudied. Formerly thought to represent a Pliocene debris flow, we interpret it as an early Miocene (NN1/2) hemipelagic deposit. We correlate the seismic unit sampled by piston core with the Kingshill-Jealousy Formation present on St. Croix. These sediments likely belong to an extensive, thick, deep marine cover of the St. Croix Ridge, deposited on a metamorphic—igneous basement between early Eocene and early Miocene time. Faulting did not evidently affect this sediment cover until the late Neogene.

von Salis, Katharina; Speed, Robert

1995-03-01

342

Miocene benthic foraminifera from Nosy Makamby and Amparafaka, Mahajanga Basin, northwestern Madagascar  

NASA Astrophysics Data System (ADS)

Madagascar is well known for its fossil deposits and hosts one of the world's most important Upper Cretaceous terrestrial faunal sites (in the Mahajanga and Morondava Basins in the west and northwest of the island). Cenozoic marine fossils are also described from Madagascar, but these have received far less attention from the paleontological community, with most of this work dating from the 19th and early 20th centuries. Our study reports a new comprehensive microfossil assemblage from a Miocene sequence on the island of Nosy Makamby. After washing, sieving and sorting (?30 kg), twenty-five genera of foraminifera were identified including Alveolina, Ammodiscus, Ammonia, Archaias, Bolivina, Borelis, Cassidulina, Cyclammina, Cycloforina, Dentalina, Elphidium, Hauerina, Lagena, Lepidocyclina, Nodosaria, Nonion, Nonionella, Peneroplis, Pyrgo, Quinqueloculina, Rhabdammina, Spirillina, Spirolina, Spiroloculina and Triloculina. Ostracods are found in association with the foraminifera, as well as many other macroinvertebrate fossils (including bivalves, gastropods, and echinoids) in addition to vertebrate fossils. Together, the assemblage indicates that during the late Miocene, Nosy Makamby was a tropical, near-shore environment, probably similar to that seen today. Furthermore, the existence of epiphytic foraminiferans (e.g., Elphidium) suggests that sea-grass beds were likely present.

Ramihangihajason, Tolotra N.; Andrianavalona, Tsiory H.; Razafimbelo, Rachel; Rahantarisoa, Lydia; Ali, Jason R.; Samonds, Karen E.

2014-12-01

343

A geochemical study of macerals from a Miocene lignite and an Eocene bituminous coal, Indonesia  

USGS Publications Warehouse

Optical and chemical studies of maceral concentrates from a Miocene lignite and an Eocene high-volatile bituminous C coal from southeastern Kalimantan, Indonesia were undertaken using pyro-Lysis, optical, electron microprobe and FTIR techniques Pyrolysis products of vitrinite from bituminous coal were dominated by straight-chain aliphatics and phenols. The huminite of the Miocene lignite produced mostly phenolic compounds upon pyrolysis. Differences in the pyrolysis products between the huminite and vitrinite samples reflect both maturation related and paleobotanical differences. An undefined aliphatic source and/or bacterial biomass were the likely contributors of n-alkyl moieties to the vitrinite. The resinite fraction in the lignite yielded dammar-derived pyrolysis products, as well as aliphatics and phenols as the products of admixed huminite and other liptinites. The optically defined resinite-rich fraction of the bituminous coal from Kalimantan produced abundant n-aliphatic moieties upon pyrolysis, but only two major resin markers (cadalene and 1,6-dimethylnaphthalene). This phenomenon is likely due to the fact that Eocene resins were not dammar-related. Data from the electron microprobe and Fourier transform infrared spectrometry strongly support the results obtained by Py GC MS and microscopy.

Stankiewicz, B.A.; Kruge, M.A.; Mastalerz, M.

1996-01-01

344

Age and paleo-oceanographic significance of silica-carbonate cycles in Miocene Monterey Formation, California  

SciTech Connect

Middle Miocene Monterey Formation cherts are often cyclically interbedded with laminated dolomites. Their co-occurrence is paradoxical because cherts are produced in relatively cold water, whereas dolomite is associated with warm water. Chert and dolomite intervals generally have poor age control, which has hindered further paleo-oceanographic interpretations. Examination of diatom assemblages that are well preserved in the dolomites has resulted in high-resolution age dating and estimation of cycle duration in 200 m of section exposed at Pt. Ano Nuevo, northern California. The age of the section ranges from late Luisian to early Mohnian, at approximately 15-12 Ma. Cycle duration estimates for the Pt. Ano Nuevo section imply that the chert-dolomite cycles may be on the order of 100,000 and 50,000 years. Such durations are consistent with, and were perhaps influenced by, changes in the earth's orbital parameters (Milankovich cycles), namely eccentricity and tilt. Warm and cold cycles have been identified by previous investigators in nondiagenetically altered middle Miocene sections of the Monterey Formation and in northeastern Pacific DSDP cores. These cycles are recognized and dated by the use of abundance fluctuations of planktonic foraminifera and diatoms. The chert-dolomite cycles are likely time equivalent to the microfossil-based cold-warm cycles and further strengthen the paleo-oceanographic and paleoclimatic interpretation.

White, L.D.

1987-05-01

345

New specimens of a fossil ostrich from the Miocene of Kenya  

NASA Astrophysics Data System (ADS)

Fossilised hind limb bones from the late Middle Miocene (approximately 14 million-year-old [MYA]) Fort Ternan, Kadianga West and Ngorora localities in Western Kenya indicate the presence of a new representative of the ostrich genus Struthio. These new fossils represent some of the oldest known records for Struthio yet described, slightly younger than Struthio coppensi, from the Lower Miocene of Namibia. Because the four sub-species of the modern-day ostrich ( Struthio camelus camelus, Struthio camelus australis, Struthio camelus massaicus, and Struthio camelus molybdophanes) inhabit the plains of Africa, and as recently as the 1940s, a fifth sub-species was also present in the Middle East and Saudi Arabia ( Struthio camelus syriacus), records of Struthio from Kenya and Namibia testify to the much wider distribution of these cursorial birds in the relatively recent past. This is further supported by the very high frequency of ostrich eggshell fragments found across Africa and Eurasia, which vastly outweighs the amount of skeletal material uncovered over the last century.

Leonard, Leona M.; Dyke, Gareth J.; Walker, Cyril A.

2006-08-01

346

Biostratigraphic sequence analysis of Oligocene-Lower Miocene sections in the Orocual Field, Eastern Venezuela Basin  

SciTech Connect

A detailed biostratigraphic study of the Oligocene-Miocene boundary was carried out in sections 1000 ft thick of ten wells of the Orocual Field, Eastern Venezuela, The sequences under investigation carry a rich microfauna of benthic and planktonic foraminifera and calcareous nannoplankton. About 500 samples were analyzed and nearly 150 species of foraminifera and 60 of nannoplankton calcareous were identified. The planktonic assemblages allow the identification of zones N3 and N4 of Blow, 1969; zones NP23, NP24, NP25 and NN1 of Martini, 1971; and zones F and E of Stainforth et al., 1959 of the Carapita Formation. The paleoenvironments of these sediments were determined rather precisely and vary from inner shelf to middle slope. Paleobathymetric curves of several wells are included. High and low fossil abundance and diversity peaks were used to recognize two sequences of the third order and five of the fourth order between 24.8 Ma and 26.5 Ma. A generalized transgressive trend is evident from the Late Oligocene to the Early Miocene.

Giffuni, G.; Castro-Mora, M. [Departamento de Geologia, Lagoven, S.A., Caracas (Venezuela)

1996-08-01

347

Rock Magnetic Record of the Middle Miocene Climatic Transition at ODP Site 747, Southern Ocean  

NASA Astrophysics Data System (ADS)

ODP Site 747, located on the central Kerguelen Plateau, contains a compete record of the Middle Miocene Climatic Transition (MMCT) - a major cooling event that followed the warm mid-Miocene Climatic Optimum and culminated in an 'icehouse' climate regime. Because of its unusually well preserved and rich foraminiferal assemblages, the MMCT interval at Site 747 has been a focus of several high-resolution paleoclimatic studies that have effectively established this sequence as a reference for the Southern Ocean. Major changes in species abundances across the MMCT are conventionally interpreted to reflect changes in water temperature and salinity. Our XRF and rock magnetic study reveals a good correlation between terrigenous input (likely from local volcanic sources) and the abundances of the dominant planktonic foraminiferal species. Such a correlation suggests that nutrient flux (iron fertilization) played a significant role in controlling microplankton communities during the MMCT at Site 747. Concentration-dependent rock magnetic parameters appear to be a useful proxy for nutrient flux in this pelagic marine environment.

Abrajevitch, A.; Roberts, A. P.; Kodama, K.

2013-12-01

348

Paleoclimatic controls on sedimentation, diagnesis, and reservior quality: Lessons from Miocene carbonates  

SciTech Connect

Miocene carbonates worldwide were deposited in a wide range of paleogeographic and tectonic settings and form important reservoirs in several regions. The reservoir quality of these carbonates appears to have been primarily controlled by the prevailing paleoclimate, which exerted a major control of both the depositional patterns and diagenetic pathways. Two end members are discussed here: (1) humid, oceanic tropical-subtropical settings, and (2) arid, land-locked temperate-subtropical settings. In humid, oceanic tropical-subtropical settings (e.g., Miocene of Southeast Asia), a warming trend paralleled by generally rising sea level allowed thick coral reefs and skeletal banks to develop, most of which are seismically resolvable. These carbonates typically represent several stages or cycles of development (largely third-order) separated by discontinuities in platform growth with episodic subaerial exposure. Development of economic reservoirs is mainly related to relative sea level falls and associated meteoric diagenesis. Trends and patterns of reservoir distribution can be predicted within a sequence stratigraphic framework. Basal transgressive carbonates are mostly tight because of their relatively fine-grained textures, intense compaction, and isolation from meteoric water influence. Best reservoir quality is commonly developed beneath subaerial unconformities in highstand buildups where effect of meteoric water leaching and karstification are most intense. 80 refs., 18 figs., 1 tab.

Sun, S.Q. (MASERA International, London (United Kingdom)); Esteban, M. (Moli d'en Moix, Palma de Mallorca (Spain))

1994-04-01

349

An amphisbaenian skull from the European miocene and the evolution of Mediterranean worm lizards.  

PubMed

The evolution of blanid amphisbaenians (Mediterranean worm lizards) is mainly inferred based on molecular studies, despite their fossils are common in Cenozoic European localities. This is because the fossil record exclusively consists in isolated elements of limited taxonomic value. We describe the only known fossil amphisbaenian skull from Europe - attributed to Blanus mendezi sp. nov. (Amphisbaenia, Blanidae) - which represents the most informative fossil blanid material ever described. This specimen, from the Middle Miocene of Abocador de Can Mata (11.6 Ma, MN7+8) in the Vallès-Penedès Basin (Catalonia, NE Iberian Peninsula), unambiguously asserts the presence of Blanus in the Miocene of Europe. This reinforces the referral to this genus of the previously-known, much more incomplete and poorly-diagnostic material from other localities of the European Neogene. Our analysis - integrating the available molecular, paleontological and biogeographic data - suggests that the new species postdates the divergence between the two main (Eastern and Western Mediterranean) extant clades of blanids, and probably precedes the split between the Iberian and North-Western African subclades. This supports previous paleobiogeographic scenarios for blanid evolution and provides a significant minimum divergence time for calibrating molecular analyses of blanid phylogeny. PMID:24896828

Bolet, Arnau; Delfino, Massimo; Fortuny, Josep; Almécija, Sergio; Robles, Josep M; Alba, David M

2014-01-01

350

Amazonian Amphibian Diversity Is Primarily Derived from Late Miocene Andean Lineages  

PubMed Central

The Neotropics contains half of remaining rainforests and Earth's largest reservoir of amphibian biodiversity. However, determinants of Neotropical biodiversity (i.e., vicariance, dispersals, extinctions, and radiations) earlier than the Quaternary are largely unstudied. Using a novel method of ancestral area reconstruction and relaxed Bayesian clock analyses, we reconstructed the biogeography of the poison frog clade (Dendrobatidae). We rejected an Amazonian center-of-origin in favor of a complex connectivity model expanding over the Neotropics. We inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. We found three episodes of lineage dispersal with two interleaved periods of vicariant events between South and Central America. During the late Miocene, Amazonian, and Central American-Chocoan lineages significantly increased their diversity compared to the Andean and Guianan-Venezuelan-Brazilian Shield counterparts. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago (MYA), rather than in situ diversification. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. The effects of Miocene paleogeographic events on Neotropical diversification dynamics provided the framework under which Quaternary patterns of endemism evolved. PMID:19278298

Santos, Juan C; Coloma, Luis A; Summers, Kyle; Caldwell, Janalee P; Ree, Richard; Cannatella, David C

2009-01-01

351

An rbcL sequence from a Miocene Taxodium (bald cypress).  

PubMed Central

During the past decade, ancient DNAs from both animals and plants have been successfully extracted and analyzed. Recently, the age of DNA that can be recovered and sequenced was increased manyfold by the amplification and sequencing of a DNA fragment from a Magnolia fossil obtained from the Miocene Clarkia deposit (17-20 million yr old). However, the validity of this report has been questioned based on models predicting that DNA should be completely degraded after 4 million yr. We report here the successful amplification, sequencing, and analysis of a 1320-base-pair portion of the chloroplast gene rbcL from a Miocene Taxodium specimen, also from the Clarkia site. These data not only validate the earlier report of sequence data for a Magnolia species from the same site but also suggest that it may be possible to isolate and sequence DNAs routinely from the Clarkia deposit. The ability to recover and sequence DNAs of such age offers enormous research possibilities in the areas of molecular evolution, biogeography, and systematics. PMID:1729716

Soltis, P S; Soltis, D E; Smiley, C J

1992-01-01

352

Late Miocene episodic lakes in the arid Tarim Basin, western China.  

PubMed

The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing much of the Asian eolian dust sources, is only a geologically recent phenomenon. Here we report episodic occurrences of lacustrine environments during the Late Miocene and investigate how the episodic lakes vanished in the basin. Our oxygen isotopic (?(18)O) record demonstrates that before the prevailing desert environment, episodic changes frequently alternating between lacustrine and fluvial-eolian environments can be linked to orbital variations. Wetter lacustrine phases generally corresponded to periods of high eccentricity and possibly high obliquity, and vice versa, suggesting a temperature control on the regional moisture level on orbital timescales. Boron isotopic (?(11)B) and ?(18)O records, together with other geochemical indicators, consistently show that the episodic lakes finally dried up at ?4.9 million years ago (Ma), permanently and irreversibly. Although the episodic occurrences of lakes appear to be linked to orbitally induced global climatic changes, the plateau (Tibetan, Pamir, and Tianshan) uplift was primarily responsible for the final vanishing of the episodic lakes in the Tarim Basin, occurring at a relatively warm, stable climate period. PMID:25368156

Liu, Weiguo; Liu, Zhonghui; An, Zhisheng; Sun, Jimin; Chang, Hong; Wang, Ning; Dong, Jibao; Wang, Huanye

2014-11-18

353

Snake fangs from the Lower Miocene of Germany: evolutionary stability of perfect weapons  

NASA Astrophysics Data System (ADS)

There is a general consensus that most of today’s nonvenomous snakes are descendants of venomous snakes that lost their venomous capabilities secondarily. This implies that the evolutionary history of venomous snakes and their venom apparatus should be older than the current evidence from the fossil record. We compared some of the oldest-known fossil snake fangs from the Lower Miocene of Germany with those of modern viperids and elapids and found their morphology to be indistinguishable from the modern forms. The primary function of recent elapid and viperid snake fangs is to facilitate the extremely rapid, stab-like application of highly toxic venoms. Our findings therefore indicate that the other components of the venom-delivery system of Early Miocene vipers and elapids were also highly developed, and that these snakes used their venom in the same way as their modern relatives. Thus, the fossil record supports the view that snakes used their venoms to rapidly subdue prey long before the mid-Tertiary onset of the global environmental changes that seem to have supported the successful radiation of venomous snakes.

Kuch, Ulrich; Müller, Johannes; Mödden, Clemens; Mebs, Dietrich

2006-02-01

354

Diversity dynamics of Miocene mammals in relation to the history of tectonism and climate  

PubMed Central

Continental biodiversity gradients result not only from ecological processes, but also from evolutionary and geohistorical processes involving biotic turnover in landscape and climatic history over millions of years. Here, we investigate the evolutionary and historical contributions to the gradient of increasing species richness with topographic complexity. We analysed a dataset of 418 fossil rodent species from western North America spanning 25 to 5 Ma. We compared diversification histories between tectonically active (Intermontane West) and quiescent (Great Plains) regions. Although diversification histories differed between the two regions, species richness, origination rate and extinction rate per million years were not systematically different over the 20 Myr interval. In the tectonically active region, the greatest increase in originations coincided with a Middle Miocene episode of intensified tectonic activity and global warming. During subsequent global cooling, species richness declined in the montane region and increased on the Great Plains. These results suggest that interactions between tectonic activity and climate change stimulate diversification in mammals. The elevational diversity gradient characteristic of modern mammalian faunas was not a persistent feature over geologic time. Rather, the Miocene rodent record suggests that the elevational diversity gradient is a transient feature arising during particular episodes of Earth's history. PMID:20427339

Finarelli, John A.; Badgley, Catherine

2010-01-01

355

New species of Agriotherium (Mammalia, Carnivora) from the late Miocene to early Pliocene of central Myanmar  

NASA Astrophysics Data System (ADS)

Here we describe a new species of giant short-faced fossil bears, Agriotheriummyanmarensis sp. nov. (Ursidae, Carnivora), from the latest Miocene to early Pliocene Irrawaddy sediments in the Chaingzauk area, central Myanmar. A. myanmarensis has a short mandible and a deep premasseteric fossa, both of which are the typical feature of Agriotherium. There are two specimens discovered so far: in the type specimen the inferior border of the mandibular corpus is rectilinearly-shaped, the m1 talonid is rather reduced, m1 metaconid larger than the entoconid-entoconulid ridge, the diastema between canine and p4 is very short, and the postcanine teeth are so reduced that existing cheek teeth are very crowded. Agriotherium had been widely distributed from the late Miocene through Pleistocene in Europe, East Asia (China), North America, and South Africa, but no fossil record has been reported from Southeast Asia. Except its extreme short snout, A. myanmarensis is most similar to that of the European form, Agriotheriuminsigne, rather than to the Asian species from Siwalik or China, such as Agriotheriumpalaeindicus, Agriotheriumsivalensis, and Agriotheriuminexpetans, suggesting the phylogenetic closeness to the European rather than to the South/East Asian forms.

Ogino, Shintaro; Egi, Naoko; Zin-Maung-Maung-Thein; Thaung-Htike; Takai, Masanaru

2011-08-01

356

Migration of sharks into freshwater systems during the Miocene and implications for Alpine paleoelevation  

NASA Astrophysics Data System (ADS)

Trace-element and isotopic compositions of fossilized shark teeth sampled from Miocene marine sediments of the north Alpine Molasse Basin, the Vienna Basin, and the Pannonian Basin generally show evidence of formation in a marine environment under conditions geochemically equivalent to the open ocean. In contrast, two of eight shark teeth from the Swiss Upper Marine Molasse locality of La Molière have extremely low ?18O values (10.3‰ and 11.3‰) and low 87Sr/86Sr ratios (0.707840 and 0.707812) compared to other teeth from this locality (21.1‰ 22.4‰ and 0.708421 0.708630). The rare earth element (REE) abundances and patterns from La Molière not only differ between dentine and enameloid of the same tooth, but also between different teeth, supporting variable conditions of diagenesis at this site. However, the REE patterns of enameloid from the “exotic” teeth analyzed for O and Sr isotopic compositions are similar to those of teeth that have O and Sr isotopic compositions typical of a marine setting at this site. Collectively, this suggests that the two “exotic” teeth were formed while the sharks frequented a freshwater environment with very low 18O-content and Sr isotopic composition controlled by Mesozoic calcareous rocks. This is consistent with a paleogeography of high-elevation (˜2300 m) Miocene Alps adjacent to a marginal sea.

Kocsis, László; Vennemann, Torsten W.; Fontignie, Denis

2007-05-01

357

The early Miocene onset of a ventilated circulation regime in the Arctic Ocean.  

PubMed

Deep-water formation in the northern North Atlantic Ocean and the Arctic Ocean is a key driver of the global thermohaline circulation and hence also of global climate. Deciphering the history of the circulation regime in the Arctic Ocean has long been prevented by the lack of data from cores of Cenozoic sediments from the Arctic's deep-sea floor. Similarly, the timing of the opening of a connection between the northern North Atlantic and the Arctic Ocean, permitting deep-water exchange, has been poorly constrained. This situation changed when the first drill cores were recovered from the central Arctic Ocean. Here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ('ventilated') conditions in the Arctic Ocean occurred during the later part of early Miocene times. We attribute this pronounced change in ventilation regime to the opening of the Fram Strait. A palaeo-geographic and palaeo-bathymetric reconstruction of the Arctic Ocean, together with a physical oceanographic analysis of the evolving strait and sill conditions in the Fram Strait, suggests that the Arctic Ocean went from an oxygen-poor 'lake stage', to a transitional 'estuarine sea' phase with variable ventilation, and finally to the fully ventilated 'ocean' phase 17.5 Myr ago. The timing of this palaeo-oceanographic change coincides with the onset of the middle Miocene climatic optimum, although it remains unclear if there is a causal relationship between these two events. PMID:17581581

Jakobsson, Martin; Backman, Jan; Rudels, Bert; Nycander, Jonas; Frank, Martin; Mayer, Larry; Jokat, Wilfried; Sangiorgi, Francesca; O'Regan, Matthew; Brinkhuis, Henk; King, John; Moran, Kathryn

2007-06-21

358

Confirmation of Late Miocene Age for Marine Strata on Isla Tiburón, Gulf of California, México  

NASA Astrophysics Data System (ADS)

Marine strata exposed on southwest corner of Isla Tiburón have been cited as the only exposed evidence for extensive middle Miocene marine incursion in the Gulf of California. Two sets of isotopic ages bracket the age of the marine strata: a capping rhyodacite flow and dike dated 11.2 ± 1.3 Ma, 4.2 ± 1.8 Ma and 3.7 ± 0.9 Ma, and pyroclastic flows previously interpreted to be intercalated near the base of the marine section, including a rhyolitic tuff dated 5.7 ± 0.2 Ma and an andesitic breccia dated 12.9 ± 0.5 Ma. The older ages, reported together by Smith et al. (1985), suggest marine sedimentation throughout the ca. 12 to 6 Ma proto-Gulf period, prior to lithispheric rupture in the adjacent Tiburón Basin. The younger late Miocene and Pliocene ages are consistent with marine microfossils reported from the marine strata, leading Oskin and Stock (2003) to reject a proto-Gulf origin for these sediments. Here we report new, detailed geologic mapping and geochronology that confirms that the southwest Isla Tiburón marine section is latest Miocene to early Pliocene age. New, 60 cm-resolution satellite imagery not available to earlier researchers greatly aided field mapping efforts, and shows previously undocumented shear and compressional structures likely related to transpression adjacent to the dextral La Cruz fault. We find that a distinct package of four rock units underlies the marine section. The lowest unit is (1) comprised of andesitic volcaniclastic rocks and lava flows. This unit is unconformably overlain by (2) a rhyolitic non- to poorly-welded ash flow tuff (10% lithic fragments and 15% phenocrysts: quartz ? K-spar > hornblende > biotite > muscovite). This tuff yielded an inverse isochron 40Ar/39Ar date of 6.7 ± 0.8 Ma. The tuff is conformably overlain by (3) bedded air fall and lapilli tuff, and (4) a mono-lithologic landslide breccia comprised of welded rhyolite tuff clasts. The emplacement of thicker landslide breccia deposits caused minor diaperic deformation in underlying tuffs. The landslide breccia (unit 4) provides a key marker exposed below the marine rocks, thus confirming that the marine rocks are younger than middle Miocene. Olistrosomal blocks of the breccia are also present in the basal marine conglomerate. We relocated the exact outcrop of andesitic breccia dated by Smith et al. (1985). The outcrop is located in the bottom of an arroyo, geographically near the base of the marine section. In this outcrop the landslide breccia (unit 4) directly overlies the andesitic breccia. This observation clearly places the andesitic breccia within the underlying andesitic volcaniclastic rocks (unit 1) and thus its age does not reflect the age of the marine strata. In summary, the earliest marine deposition on southwest Isla Tiburón is now better constrained to post-date 6.7 ± 0.8 Ma, more consistent with a latest Miocene marine incursion coincident with lithospheric rupture in the northern Gulf of California

Buckmaster, N. G.; Bennett, S. E.; Oskin, M. E.; Ford, J. A.

2009-12-01

359

Late Miocene biomarker and pollen records in Southeast Atlantic Ocean sediments indicate environmental changes  

NASA Astrophysics Data System (ADS)

The Late Miocene epoch is characterized by fundamental changes in Earth‘s climate system: sea-level variability, changes in surface- and deep-water circulation, increase in upwelling intensity along the coasts and turnover in marine and terrestrial biota [1,2]. It is thought that plants using the CO2 concentrating C4 mechanism for photosynthesis potentially evolved during times of a global drop in atmospheric CO2 content and at relatively hot and dry habitats. During the Late Miocene C4 plants expanded nearly simultaneously at different places in the world, while temperatures declined and global CO2 levels exhibited no corresponding change [1,3]. Our objectives concern the climatic and environmental change of Miocene Southwest Africa between ~14 to ~5 Myrs BP and how these conditions may be linked to the C4 plant expansion. We use a variety of organic geochemical techniques combined with palynology on sediments of ODP Site 1085. The site is situated in the Cape Basin at the south-west African continental margin, within the today's upwelling zone of the Benguela Coastal Current. Miocene sea surface temperature (SST) estimates applying two indices (TEX86 and UK'37) suggest a transition to cooler temperatures from above 27 to 18°C over a time period from ~14 to ~5 Myrs BP, but are different in rate and timing. Increased upwelling leads to cooler SSTs and enhanced marine primary production as implied by a small but clear overall shift in total organic carbon content after 11 Myrs BP. Concurrently, the abundance of both marine cysts and terrestrial pollen and spores increase and the relative contribution river run-off from the nearby Orange River declines, as indicated by the BIT-index (from ~0.8 to <0.1). We connect these findings to a change in strength and the predominant direction of the wind combined with an intensification of the Benguela upwelling current bringing cold, nutrient-rich waters from the South Atlantic and the Antarctic circumpolar current, probably driven by the formation of the West Antarctic ice sheet [1,2]. The transport way for terrestrial organic matter, pollen and spores changed from riverine to predominantly airborne contribution potentially accompanied by a change of the source area. However, pollen records and molecular stable carbon and hydrogen isotopic measurements of plant leaf wax n-alkanes exhibit spreading grassy vegetation due to a stepwise growing aridity in South Africa. After 8 Myrs BP terrestrial floral assemblages got more affinity to those of the Pleistocene and mark the beginning of the floral change towards C4-dominance. We infer that by the end of the Miocene C4 grasslands became important in Southwest Africa. References [1] Zachos, J. et al. (2001) Science 292, 686-693. [2] Diester-Haass, L.D., et al. (1990) Paleoceanogr. 5, 685-707. [3] Tipple, B.J., Pagani, M. (2007) Annu. Rev. Earth Planet. Sci. 35, 435-461.

Rommerskirchen, Florian; Dupont, Lydie; Condon, Tegan; Mollenhauer, Gesine; Schefuß, Enno

2010-05-01

360

Oligocene and Miocene Vegetation and climate development on the Atlantic Coastal Plain (IODP Expedition 313)  

NASA Astrophysics Data System (ADS)

The major aims of IODP Expedition 313 are estimating amplitudes, rates and mechanisms of sea-level change and the evaluation of sequence stratigraphic facies models that predict depositional environments, sediment compositions, and stratal geometries in response to sea-level change. Cores from three Sites (313-M0027, M0028, and M0029; 45 to 67 km off the coast of New Jersey) from the New Jersey shallow shelf (water depth approximately 35 m) were retrieved during May to July 2009, using an ECORD "mission-specific" jack-up platform. The recovery rate for the three sites exceeded 80%; in total, more than 1300 m core length were achieved. The oldest sediments were recovered from Hole M0027A, and dated as late Eocene/early Oligocene according to biostratigraphy, sequence-stratigraphy, and Sr-isotopy-based age estimates. We have investigated the palynology of sediment cores from Sites M0027 and M0029. The cores examined span ca. 33 to 13 million years before present together with additional samples from younger sediments. The palynological results were complemented with pollen-based quantitative climate reconstructions using bioclimatic analysis, a mutual climate range NLR approach. Until the Pleistocene, the hinterland vegetation of the New Jersey shelf was characterized by oak-hickory forests in the lowlands and conifers in the highlands. The Oligocene witnessed several downward expansions of conifer forest, which were probably related to cooling events. The pollen-based climate data show a temperature increase during the Rupelian and at the Chattian-Aquitanian transition, with mean annual temperatures surpassing 15 °C. For the Miocene, mean annual temperatures varied around ~13.5 °C. Generally, the Miocene ecosystem and climate conditions were similar to those of the Oligocene in the hinterland of the New Jersey shelf. We conjecture that the Miocene uplift of the Appalachian Mountains led to the proliferation of mountainous taxa and thus to an increase of related pollen taxa in the palynological record. This explains the comparatively low annual temperatures reconstructed for this time interval. The vegetation changed after the Miocene, with increasing conifers, and understorey and swamp taxa. A Miocene to Pleistocene expansion of grasslands is not evident for the hinterland of the New Jersey shelf. The pollen-based annual temperature curve shows general agreement with global oxygen isotope data; however, there seems to be a shift to younger ages in the dataset from the New Jersey shallow shelf; thus for some time intervals, regional terrestrial temperature may have been decoupled from marine conditions. Transport-caused bias of the pollen assemblages was identified via the analysis of the terrestrial/marine palynomorph ratio and these were considered when interpreting palaeo-vegetation and climate from the pollen data.

Kotthoff, Ulrich; McCarthy, Francine; Greenwood, David; Hesselbo, Stephen

2013-04-01

361

Individual to Community-Level Faunal Responses to Environmental Change from a Marine Fossil Record of Early Miocene Global Warming  

PubMed Central

Modern climate change has a strong potential to shift earth systems and biological communities into novel states that have no present-day analog, leaving ecologists with no observational basis to predict the likely biotic effects. Fossil records contain long time-series of past environmental changes outside the range of modern observation, which are vital for predicting future ecological responses, and are capable of (a) providing detailed information on rates of ecological change, (b) illuminating the environmental drivers of those changes, and (c) recording the effects of environmental change on individual physiological rates. Outcrops of Early Miocene Newport Member of the Astoria Formation (Oregon) provide one such time series. This record of benthic foraminiferal and molluscan community change from continental shelf depths spans a past interval environmental change (?20.3-16.7 mya) during which the region warmed 2.1–4.5°C, surface productivity and benthic organic carbon flux increased, and benthic oxygenation decreased, perhaps driven by intensified upwelling as on the modern Oregon coast. The Newport Member record shows that (a) ecological responses to natural environmental change can be abrupt, (b) productivity can be the primary driver of faunal change during global warming, (c) molluscs had a threshold response to productivity change while foraminifera changed gradually, and (d) changes in bivalve body size and growth rates parallel changes in taxonomic composition at the community level, indicating that, either directly or indirectly through some other biological parameter, the physiological tolerances of species do influence community change. Ecological studies in modern and fossil records that consider multiple ecological levels, environmental parameters, and taxonomic groups can provide critical information for predicting future ecological change and evaluating species vulnerability. PMID:22558424

Belanger, Christina L.

2012-01-01

362

Group Assignment-1 Group A Group B Group C  

E-print Network

Group Assignment-1 Group A Group B Group C Shirkhodai, Arta ( artashir ) Kurozumi, Dean ( kurozumi ) Trang, Derrick ( trangd ) Yim, Gilbert ( gyim ) Marchant, Richard ( rmarchan) Young, Garrett ( garrettz

Zhang, Rui

363

Group Assignment-2 Group A Group B Group C  

E-print Network

Group Assignment-2 Group A Group B Group C Shirkhodai, Arta ( artashir ) Kurozumi, Dean ( kurozumi ( cobatake ) Shultz, Allen ( shultzam ) Yamakawa, Kelsie ( kayama ) Young, Garrett ( garrettz ) Walser, Ryan

Zhang, Rui

364

Strawberry Rhyolites, Oregon: Northwestern extent of mid-Miocene flood basalt related rhyolites of the Pacific Northwest  

NASA Astrophysics Data System (ADS)

Rhyolitic volcanism associated with the Columbia River-Steens flood basalts of the Pacific Northwest has traditionally been viewed to be centered at McDermitt caldera near the Oregon-Nevada border starting at ~16.5 Ma. In recent years, more rhyolitic centers along this latitude with ages between 16.5-15.5 Ma have been identified and associated with the inception of the Yellowstone hotspot. However the footprint of plume-head related rhyolites becomes much larger when silicic centers of mid-Miocene age in eastern Oregon are included extending the distribution of such rhyolites to areas near the towns of Baker City and John Day ~250 km north of McDermitt. This study addresses one of these rhyolitic centers that was virtually unknown and that constitutes the northwestern extent of mid-Miocene rhyolites. Rhyolites are centered ~40 km SSW of John Day and are considered part of the Strawberry Volcanic Field (SVF), which consists of a diverse group of volcanic rocks ranging from basalt to rhyolite with abundant intermediate compositions. One existing age date of 17.3 Ma ± 0.36 (Robyn, 1977) - if confirmed by our ongoing study - places these rhyolites at the very onset of plume-head related rhyolites. Strawberry rhyolitic lavas are most voluminous in the southwestern portion of the SVF covering approximately 500 km2 between Bear and Logan Valley. The rhyolitic lavas tend to be phenocryst-poor (<3%) and range from obsidian to devitrified flow banded rhyolites. The major phenocryst phases include plagioclase, quartz, and occasional biotite. Field evidence suggests that the aphyric high-silica rhyolite lavas (~77 wt. % SiO2) erupted first, followed by rhyolite lava flows with increasing phenocryst proportions and decreasing SiO2 (70 wt. %). Lastly, phenocryst-rich dacite lava erupted on top, capping the rhyolite. There is no evidence of significant time gaps between lavas flows, suggesting eruption in short succession. Rhyolites from the SVF are high-K, calc-alkaline lavas and are mostly metaluminous (e.g. 11.1 - 15.2 wt. % Al2O3, 0.06 - 2.70 wt. % CaO). Trace elements of Strawberry Rhyolites show minor variability except in, Sr (10 - 200 ppm), Zr (65 - 450 ppm), Ti (300 - 3500 ppm), and Ba (350 - 1600 ppm). When normalized to upper crustal values, Strawberry Rhyolites plot around 1 with significant troughs at Sr, P, Ti, and minor troughs in Ba, Nb, and Zr. REE patterns indicate slight LREE enrichment with LaN/YbN values ranging from 2.5 to 8.3 and higher values correlate positively with other differentiation indices (e.g. Ba, Sr, Eu/Eu*). Furthermore, major elements (e.g. SiO2 and FeO*) and trace elements (e.g. Ba, Sr, La, Zr/Hf) display common liquid lines of decent with Eu/Eu*. This suggests that the Strawberry Rhyolites are likely products of variable degrees of differentiation. Future petrogenetic evaluations will further investigate the origin of the Strawberry Rhyolites.

Steiner, A. R.; Streck, M. J.

2011-12-01

365

Paleomagnetism of the early Miocene Kani group in southwest Japan and its implication for the opening of the Japan Sea  

SciTech Connect

Paleomagnetic directions of a volcanic and sedimentary sequence of the Kani Basin, ranging from 22 to 15 Ma, show a clockwise declination shift of about 50{degree}. This result implies that detectable rotation of Southwest Japan did not occur in this period, but after 15 Ma. The initial opening of the Japan Sea before 15 Ma might have caused a southeastward translation of Southwest Japan, which was then followed by clockwise rotation between 16 and 14 Ma.

Hayashida, Akira; Fukui, Takako (Doshisha Univ., Kyoto (Japan)); Torii, Masayuki (Kyoto Univ. (Japan))

1991-06-01

366

Dietary niche partitioning among fossil bovids in late Miocene C 3 habitats: Consilience of functional morphology and stable isotope analysis  

Microsoft Academic Search

Teeth of late Miocene bovids referred to Bovini and “Boselaphini” were subjected to enamel stable carbon and oxygen isotope analysis to test paleoecological reconstructions based on dental morphology. Teeth of Bovini possess derived characters–including larger size, higher crowns, and increased enamel surface area–that are indicative of feeding on a more fibrous and gritty diet, probably grass. In contrast, teeth of

Faysal Bibi

2007-01-01

367

Magnetostratigraphy and paleontology of Aït Kandoula basin (High Atlas, Morocco) and the African-European late Miocene terrestrial fauna exchanges  

Microsoft Academic Search

A magnetostratigraphic study has been carried out on a middle Miocene to upper Pliocene lacustrine sedimentary deposit in the central part of the Aït Kandoula basin, which contains micromammal faunas and is situated in the southern High Atlas (Morocco). In total, 113 samples were subjected to paleomagnetic analysis: 60 out of the 113 studied samples representing 52 different stratigraphic levels

Mouloud Benammi; Manuel Calvo; Michel Prévot; Jean-Jacques Jaeger

1996-01-01

368

Ichnology and Sedimentology Reveal Depositional Characteristics of Bay-Margin Parasequences in the Miocene Amazonian Foreland Basin  

Microsoft Academic Search

Proposed depositional models for Miocene Amazon fore- land basin strata (Pebas Formation, Peru) are controversial. Recent depositional models include lacustrine and tidally influenced, brackish- water embayment. This paper presents data that support tidally influ- enced, brackish-water deposition for at least part of Pebas time (10- 14 Ma). Two parasequences are presented (Santa Julia and Tamshi- yacu). Both crop out along

MURRAY K. GINGRAS; MATTI E. RASANEN; S. GEORGE PEMBERTON; LIDIA P. ROMERO

2002-01-01

369

Using ecological niche modeling for quantitative biogeographic analysis: a case study of Miocene and Pliocene Equinae in the  

E-print Network

the late Miocene. Here we use ecological niche modeling (ENM), specifically the GARP (Genetic Algorithm each species' fundamental niche. The geographic range of each species is then predicted to occupy the fundamental niche occurs. We analyze changes in the predicted distributions of individual species between time

Barnosky, Anthony D.

370

Regional trends in clay mineral fluxes to the Queensland margin and ties to middle Miocene global cooling  

Microsoft Academic Search

Three ODP sites located on the Marion Plateau, Northeast Australian margin, were investigated for clay mineral and bulk mineralogy changes through the early to middle Miocene. Kaolinite to smectite (K\\/S) ratios, as well as mass accumulation rates of clays, point to a marked decrease in accumulation of smectite associated with an increase in accumulation of kaolinite starting at ?15.6 Ma,

Cédric M. John; Thierry Adatte; Maria Mutti

2006-01-01

371

Carcharodon megalodon from the Upper Miocene of Denmark, with comments on elasmobranch tooth enameloid: coronoi'n  

Microsoft Academic Search

C5 C. megalodon, not previously known from deposits in Denmark, is recorded from a large, but imperfect tooth derived from the marine clay exposed at the type locality for the Upper Miocene Gram Formation. Detached, large vertebral centra from this locality, probably belonging to the same species, are considered as well as the nomenclature and phylogenetic relationships of the genus

SVEND ERIK BENDIX-ALMGREEN

372

Paleoenvironmental significance of a new species of freshwater sponge from the Late Miocene Quillagua Formation (N Chile)  

Microsoft Academic Search

This paper reports the first fossil (Tertiary) occurrence of freshwater sponges of the genus Ephydatia in the southern hemisphere. The sponges appear in diatomite lacustrine sediments of Late Miocene Quillagua Formation (Chile, Atacama region). The investigated specimens represent a new species, Ephydatia chileana sp. nov., which is close to the Recent cosmopolitan E. fluviatilis. On the basis of sedimentological and

A. Pisera; A Sáez

2003-01-01

373

An exceptionally well-preserved short-snouted bandicoot (Marsupialia; Peramelemorphia) from Riversleigh's Oligo-Miocene deposits, northwestern Queensland, Australia  

Microsoft Academic Search

We describe Galadi speciosus, gen. et sp nov., the second peramelemorphian (Yarala burchfieldi being the first) to be described from Oligo-Miocene deposits of Riversleigh World Heritage Property, northwestern Queensland. G. speciosus is represented by relatively complete craniodental material, including an exceptionally well-preserved skull. This taxon exhibits several apomorphies that clearly place it in the order Peramelemorphia, but it appears to

K. J. TRAVOUILLON; Y. GUROVICH; R. M. D. BECK; J. MUIRHEAD

2010-01-01

374

Palaeoenvironment and Its Control on the Formation of Miocene Marine Source Rocks in the Qiongdongnan Basin, Northern South China Sea  

PubMed Central

The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter. PMID:25401132

Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

2014-01-01

375

Miocene to recent ice elevation variations from the interior of the West Antarctic Ice sheet: Constraints from geologic observations, cosmogenic  

E-print Network

-term West Antarctic Ice Sheet (WAIS) behavior can be used to test and constrain dynamic ice sheet models-term (Miocene-Holocene) WAIS elevation from the interior of the ice sheet near the WAIS divide. We use geologic observations and measurements of cosmogenic 21 Ne and 10 Be in bedrock surfaces to constrain WAIS elevation

Mukhopadhyay, Sujoy

376

ELSEVIER Marine Micropaleontology 27 (1996) 253-27 1 Miocene and Pliocene paleoclimate of the Dry Valleys region,  

E-print Network

ELSEVIER Marine Micropaleontology 27 (1996) 253-27 1 Miocene and Pliocene paleoclimate of the Dry western Dry Valleys region above 1200 m elevation during late Pliocene time. Overall, our paleoclimate-271 1. Introduction A detailed late Cenozoic paleoclimate record for the Transantarctic Mountains

Marchant, David R.

377

Conifer and angiosperm biomarkers in clay sediments and fossil plants from the Miocene Clarkia Formation, Idaho, USA  

Microsoft Academic Search

The aliphatic lipids and terpenoids of conifer and angiosperm macrofossils and the clay sediment from a new site (P-37) of the Miocene Clarkia Formation, Idaho, USA, were analyzed to evaluate the preservation of characteristic conifer and angiosperm biomarkers in the sediment. Series of aliphatic lipids, terpenoids and steroids similar to the biomarkers found in type locality Clarkia P-33 were the

Angelika Otto; Bernd R. T. Simoneit; William C. Rember

2005-01-01

378

DISCOVERY OF DESEADAN FOSSILS IN THE UPPER MOQUEGUA FORMATION (LATE OLIGOCENE--?EARLY MIOCENE) OF SOUTHERN PERU  

E-print Network

NOTE DISCOVERY OF DESEADAN FOSSILS IN THE UPPER MOQUEGUA FORMATION (LATE OLIGOCENE--?EARLY MIOCENE. The Deseadan SALMA fossils were found in the Upper Mo- quegua Formation at the summits of Cerro Pan de Azúcar OF THE UPPER MOQUEGUA FORMATION The most common fossils so far encountered in the Upper Moquegua Formation

Sargis, Eric J.

379

Diets of modern and late Miocene hippopotamids: Evidence from carbon isotope composition and micro-wear of tooth enamel  

Microsoft Academic Search

Carbon isotope composition and micro-wear analyses of tooth enamel were used to reconstruct the diet of late Miocene hippopotamids unearthed in the Toros-Ménalla area, Chad, contemporary to the oldest known hominids. A large sample of wild modern Hippopotamus amphibius from various locations in Africa was also analysed for comparison. Isotopic analyses showed that the modern hippo, reputedly a strict grazer,

Jean-Renaud Boisserie; Antoine Zazzo; Gildas Merceron; Cécile Blondel; Patrick Vignaud; Andossa Likius; Hassane Taïsso Mackaye; Michel Brunet

2005-01-01

380

Early Miocene repetitive vegetation and climatic changes in the lacustrine deposits of the Rubielos de Mora Basin (Teruel, NE Spain)  

E-print Network

conditions for developing riparian forests. The vegetation was clearly controlled by the water availability. mesothermic­riparian) reflects the influence of the cyclicity of temperature and precipitation on the lakeEarly Miocene repetitive vegetation and climatic changes in the lacustrine deposits of the Rubielos

Jiménez-Moreno, Gonzalo

381

Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene and early Pliocene  

E-print Network

Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene discharges of icebergs from Wilkes Land and Adélie Land, more than 1500 kilometers to the east of the depositional site. This distant source of icebergs is clearly defined by the presence of IRD hornblende grains

Long, Bernard

382

Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene and early Pliocene  

E-print Network

Evidence for iceberg armadas from East Antarctica in the Southern Ocean during the late Miocene discharges of icebergs from Wilkes Land and Ad�lie Land, more than 1500 kilometers to the east of the depositional site. This distant source of icebergs is clearly de ned by the presence of IRD hornblende grains

Hemming, Sidney R

383

Timing and magnitude of Miocene eustasy derived from the mixed siliciclastic-carbonate stratigraphic record of the northeastern Australian margin  

Microsoft Academic Search

Eustasy is a key parameter to understand sedimentary sequences on continental margins and to reconstruct continental ice volume in the Cenozoic, but timing and magnitude of global sea level changes remain controversial, especially for the Miocene Epoch. We analyzed sediment cores recovered from the Marion Plateau, offshore northeastern Australia, during Ocean Drilling Program (ODP) Leg 194 to define the mechanisms

Cédric M. John; Garry D. Karner; Emily Browning; R. Mark Leckie; Zenon Mateo; Brooke Carson; Chris Lowery

2011-01-01

384

Paleoenvironmental conditions preceding the Messinian Salinity Crisis in the Central Mediterranean: Integrated data from the Upper Miocene Trave section (Italy)  

E-print Network

: Integrated data from the Upper Miocene Trave section (Italy) Agata Di Stefano a, , Marina Verducci b a Dipartimento di Scienze Geologiche, University of Catania, Corso Italia 55, 95129 Catania, Italy b Dipartimento di Scienze della Terra, University of Siena, Via Laterina 8, 53100 Siena, Italy c Istituto per l

Utrecht, Universiteit

385

Formation of patterned ground and sublimation till over Miocene glacier ice in Beacon Valley, southern Victoria Land, Antarctica  

Microsoft Academic Search

A thin glacial diamicton, informally termed Granite drift, oc- cupies the floor of central Beacon Valley in southern Victoria Land, Antarctica. This drift is ,1.0 m thick and rests with sharp planar contacts on stagnant glacier ice reportedly of Miocene age, older than 8.1 Ma. The age of the ice is based on 40 Ar\\/ 39 Ar analyses of presumed

D. R. Marchant; A. R. Lewis; W. M. Phillips; E. J. Moore; R. A. Souchez; G. H. Denton; D. E. Sugden; N. Potter Jr.; G. P. Landis

2002-01-01

386

Dietary and environmental reconstruction with stable isotope analyses of herbivore tooth enamel from the Miocene locality of Fort Ternan, Kenya  

Microsoft Academic Search

Tooth enamel of nine Middle Miocene mammalian herbivores from Fort Ternan, Kenya, was analyzed for ?13C and ?18O. The ?18O values of the tooth enamel compared with pedogenic and diagenetic carbonate confirm the use of stable isotope analysis of fossil tooth enamel as a paleoenvironmental indicator. Furthermore, the ?18O of tooth enamel indicates differences in water sources between some of

Thure E. Cerling; John M. Harris; Stanley H. Ambrose; Meave G. Leakey; Nikos Solounias

1997-01-01

387

Galaxias fossils from Miocene lake deposits, Otago, New Zealand: The earliest records of the Southern Hemisphere family Galaxiidae (Teleostei)  

Microsoft Academic Search

Galaxiid fishes are commonly assumed to exhibit a Gondwanan distribution, but little fossil evidence has been available to support or refute this assumption until now. Here we report on three species of fossil Galaxias, represented by exquisitely preserved, almost entire skeletons, together with jaw and skull fragments, from several Miocene lacustrine deposits in Otago, South Island, New Zealand. These are

D. E. Lee; R. M. McDowall; J. K. Lindqvist

2007-01-01

388

Provenance analysis of the Miocene accretionary prism of the Hengchun Peninsula, southern Taiwan, and regional geological significance  

NASA Astrophysics Data System (ADS)

Petrographic analysis, detrital zircon U-Pb geochronology and Neodymium isotope are applied to the Middle-Late Miocene turbidite sequences in the Hengchun accretionary prism, southern Taiwan, to constrain the provenance and nature of sedimentation in the Manila subduction system. Both petrographic study and detrital zircon U-Pb ages show that the Middle-Late Miocene turbidite sequences were primarily derived from Mesozoic granites and volcanic rocks of the Cathaysian Block in SE China, which were transported southeastward via rivers like Minjiang and Jiulongjiang to the Taiwan area. This conclusion is further supported by Nd isotope analyses of shales intercalated within sandstone sequences showing negative ?Nd values (-13.3 to -10.5) of a continental origin. During the Late Miocene when global sea-level fell significantly, the SE China coastline shifted seaward to the eastern part of the present Taiwan Strait, which would have facilitated these continent-derived sediments being transported southeastward to the shelf-upper slope of the Chinese continental margin. These turbidite sequences were then deformed and accreted into the accretionary prism of the Hengchun Peninsula when the South China Sea oceanic lithosphere subducted eastward beneath the Philippine Sea Plate in the Late Miocene. Our study suggests that sedimentary deposition of the turbidite sequences in the Hengchun Peninsula could be strongly controlled by different river system supply, submarine channeling transport and fluctuations of sea-level.

Zhang, Xinchang; Yan, Yi; Huang, Chi-Yue; Chen, Duofu; Shan, Yehua; Lan, Qin; Chen, Wenhuang; Yu, Mengming

2014-05-01

389

Late miocene-pliocene paleoclimatic evolution documented by terrestrial mollusk populations in the western Chinese Loess Plateau.  

PubMed

The Neogene eolian deposits in the Chinese Loess Plateau (CLP) are one of the most useful continental deposits for understanding climatic changes. To decipher Late Neogene paleoclimatic changes in the CLP, we present a terrestrial mollusk record spanning the time interval between 7.1 and 3.5 Ma from the western CLP. The results indicate four stages of paleoclimatic evolution: From 7.1 to 6.2 Ma, cold and dry climatic conditions prevailed as evidenced by high values of the total number of cold-aridiphilous (CA) mollusk species and by low values of all of the thermo-humidiphilous (TH) mollusk indices. From 6.2 to 5.4 Ma, the climate remained cold and dry but was not quite as dry as during the preceding phase, as indicated by the dominance of CA mollusks and more TH species and individuals. From 5.4 to 4.4 Ma, a warm and moist climate prevailed, as indicated by high values of the TH species and individuals and by the sparsity of CA species and individuals. From 4.4 to 3.5 Ma, all of the CA indices increased significantly and maintained high values; all of the TH indices exhibit high values from 4.4 to 4.0 Ma, an abrupt decrease from 4.0 Ma and a further increase from 3.7 Ma. The CA species of Cathaica pulveraticula, Cathaica schensiensis, and Pupopsis retrodens are only identified in this stage, indicating that the CA species were diversified and that the climate was becoming drier. Moreover, the CA mollusk group exhibits considerable diversity from 7.1 to 5.4 Ma when a cold, dry climate prevailed; whereas the diversity of the TH group was high during the relatively warm, wet interval from 5.4 to 4.4 Ma. This indicates that variations in the diversity of the CA and TH mollusk groups were closely related to climatic changes during the Late Miocene to Pliocene. PMID:24752586

Li, Fengjiang; Wu, Naiqin; Rousseau, Denis-Didier; Dong, Yajie; Zhang, Dan; Pei, Yunpeng

2014-01-01

390

Late Miocene-Pliocene Paleoclimatic Evolution Documented by Terrestrial Mollusk Populations in the Western Chinese Loess Plateau  

PubMed Central

The Neogene eolian deposits in the Chinese Loess Plateau (CLP) are one of the most useful continental deposits for understanding climatic changes. To decipher Late Neogene paleoclimatic changes in the CLP, we present a terrestrial mollusk record spanning the time interval between 7.1 and 3.5 Ma from the western CLP. The results indicate four stages of paleoclimatic evolution: From 7.1 to 6.2 Ma, cold and dry climatic conditions prevailed as evidenced by high values of the total number of cold-aridiphilous (CA) mollusk species and by low values of all of the thermo-humidiphilous (TH) mollusk indices. From 6.2 to 5.4 Ma, the climate remained cold and dry but was not quite as dry as during the preceding phase, as indicated by the dominance of CA mollusks and more TH species and individuals. From 5.4 to 4.4 Ma, a warm and moist climate prevailed, as indicated by high values of the TH species and individuals and by the sparsity of CA species and individuals. From 4.4 to 3.5 Ma, all of the CA indices increased significantly and maintained high values; all of the TH indices exhibit high values from 4.4 to 4.0 Ma, an abrupt decrease from 4.0 Ma and a further increase from 3.7 Ma. The CA species of Cathaica pulveraticula, Cathaica schensiensis, and Pupopsis retrodens are only identified in this stage, indicating that the CA species were diversified and that the climate was becoming drier. Moreover, the CA mollusk group exhibits considerable diversity from 7.1 to 5.4 Ma when a cold, dry climate prevailed; whereas the diversity of the TH group was high during the relatively warm, wet interval from 5.4 to 4.4 Ma. This indicates that variations in the diversity of the CA and TH mollusk groups were closely related to climatic changes during the Late Miocene to Pliocene. PMID:24752586

Li, Fengjiang; Wu, Naiqin; Rousseau, Denis-Didier; Dong, Yajie; Zhang, Dan; Pei, Yunpeng

2014-01-01

391

Unlocking the Ice House: Oligocene-Miocene oxygen isotopes, eustasy, and margin erosion  

NASA Astrophysics Data System (ADS)

Oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on Antarctica since the earliest Oligocene (circa 35 Ma). The growth and decay of ice sheets during the Oligocene to modern "ice house world" caused glacioeustatic sea level changes. The early Eocene was an ice-free "greenhouse world," but it is not clear if ice sheets existed during the middle to late Eocene "doubt house world." Benthic foraminiferal ?18O records place limits on the history of glaciation, suggesting the presence of ice sheets at least intermittently since the earliest Oligocene. The best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic ?18O records. Although planktonic isotope records from the western equatorial regions are limited, subtropical planktonic foraminifera may also record such ice volume changes. It is difficult to apply these established principles to the Cenozoic ?18O record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events. We improved Oligocene to Miocene correlations of ?18O records and erected eight oxygen isotope zones (Oi1-Oi2, Mi1-Mi6). Benthic foraminiferal ?18O increases which are associated with the bases of Zones Oil (circa 35.8 Ma), Oi2 (circa 32.5 Ma), and Mil (circa 23.5 Ma) can be linked with ?18O increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near Antarctica. Our new correlations of middle Miocene benthic and western equatorial planktonic ?18O records show remarkable agreement in timing and amplitude. We interpret benthic-planktonic covariance to reflect substantial ice volume increases near the bases of Zones Mi2 (circa 16.1 Ma), Mi3 (circa 13.6 Ma), and possibly Mi5 (circa 11.3 Ma). Possible glacioeustatic lowerings are associated with the ?18O increases which culminated with the bases of Zone Mi4 (circa 12.6 Ma) and Mi6 (circa 9.6 Ma), although low-latitude planktonic ?18O records are required to test this. These inferred glacioeustatic lowerings can be linked to seismic and rock disconformities. For example, we link 12 Oligocene-early late Miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries (= inferred eustatic lowerings) of Haq et al. (1987).

Miller, Kenneth G.; Wright, James D.; Fairbanks, Richard G.

1991-04-01

392

Thermochronologic evidence for Miocene mid-crustal tectonic exhumation of the Huachuca Mountains, southeast Arizona  

NASA Astrophysics Data System (ADS)

Zircon double dating of detrital grains from the northward flowing upper San Pedro river valley at Murray Springs in southeastern Arizona yields abundant zircons with variable U/Pb crystallization ages of ~70-1400 Ma, but a restricted range of (U-Th)/He cooling ages of ~18-25 Ma. This combination of diverse formation ages but uniform mid-Miocene cooling ages is characteristic of zircons from the core complexes and deeply exhumed Santa Catalina, Rincon, and Pinaleno Mountains, which experienced tectonic exhumation from mid-crustal depths during mid-Miocene extension. But all these sources are far downstream or outside the watershed of the upper San Pedro valley. To trace the source of these detrital grains and understand the implications for regional tectonics, we also measured U/Pb and (U-Th)/He dates of zircons from the Tombstone Hills and Huachuca Mountains, proximal to the Murray Springs site. Magmatic rocks in the Tombstone Hills yielded U/Pb dates of 76-83 Ma and zircon He ages of 53-60 Ma. In contrast, crystalline basement of the Huachucas yields Cretaceous through 1.5-Ga U/Pb ages and zircon He ages of 17-25 Ma, with most between 21-22 Ma. These data require that a large region of the Huachucas contains rocks that cooled rapidly below temperatures of at least 180 oC in the mid-Miocene. Assuming typical geothermal gradients of 20-30 oC, this requires exhumation of at least 7-9 km of crust, likely within 1-2 Myr. While it is possible that erosion contributed, it is more likely that denudation was accommodated by deep tectonic exhumation. Faults are observed on the basin-bounding east-side of the Huachucas, but most are inferred to accommodate Laramide-age thrusting, and the normal faults have been interpreted as high-angle and unlikely to cause significant tectonic exhumation. Our new data suggest that a large part of the presently exposed Huachucas was exhumed from depths at least as great as ~7-9 km, requiring a considerable revision of structural interpretations for the range. In addition, the inferred large-magnitude eastside-down sense of motion in this region, also required for the Whetstone Mountains to the north, requires a major north-south change in the geometry of extension accommodation, to separate it from the westside-down Catalina-Rincon core complex system to the north.

King, C. C.; Orme, D. A.; Biswas, A.; Reiners, P. W.

2011-12-01

393

Late Miocene tilting of the Resting Spring Range, California, with implications for mechanisms of crustal extension  

NASA Astrophysics Data System (ADS)

Competing models for crustal extension across the Death Valley region of eastern California and adjacent Nevada can be evaluated on the basis of different expectations for patterns of fault timing. Field data, paleomagnetic analysis, and 40Ar/39Ar geochronology in the Resting Spring Range, located 50 km east of Death Valley, suggest that 52-55% of extension-related tilting of Miocene sedimentary and volcanic rocks occurred between ~11.6 and 9.8 Ma, while 45-48% of tilting occurred after ~9.8 Ma. We attribute the earlier tilting to displacement on a fault system marking the western flank of the Nopah Range to the east and a fault that cuts obliquely through the Resting Spring Range at Resting Spring Pass. Tilting after 9.8 Ma occurred primarily through slip on the fault system that marks the western flank of Resting Spring Range. Previous workers (Heydari, 1981, Penn State M.S. thesis; Niemi et al., 2001, GSAB) inferred that the welded ash-flow tuff at Resting Spring Pass, for which we have obtained an age of 9.8 ± 0.2 Ma, is close to flat-lying, implying no significant range tilting after its emplacement. However, paleomagnetic data collected from the tuff indicate that the unit dips at least 20° E at Resting Spring Pass, consistent with significant extensional tilting after deposition. Approximately 16° of the tilt expressed by the Neoproterozoic to Cambrian stratigraphy that unconformably underlies the Miocene rocks is thought to pre-date extension. This interpretation is based on the observation that Miocene paleovalleys and fluvial paleocurrents are oriented between north and west, approximately parallel to the present-day range, and orthogonal to the dip of underlying rocks. These data from the Resting Spring Range, when combined with constraints on the timing of faulting and exhumation in the Black Mountains to the west, are inconsistent with the pattern of sequentially younger faulting to the northwest that is expected in the rolling hinge model for crustal extension across this region. Our results are more consistent with a model of discrete normal faulting, for which no systematic, spatiotemporal pattern of faulting is implied.

Tremblay, M. M.; Christie-Blick, N.; Hemming, S. R.; Anders, M. H.

2012-12-01

394

Provenance, Offset Equivalent and Palinspastic Reconstruction of the Miocene Cajon Valley Formation, Southern California  

NASA Astrophysics Data System (ADS)

Petrographic, conglomerate and detrital-zircon analyses of formations in southern California can determine consanguineous petrofacies and lithofacies that help constrain paleotectonic and paleogeographic reconstructions of the southwestern United States. Arkosic sandstone of the lower Middle Miocene Cajon Valley formation is exposed on the southwest edge of the Mojave block and juxtaposed against Mesozoic and Paleozoic rocks by the San Andreas fault (SAf). Early work in Cajon Valley referred to the formation as Punchbowl, due to its similar appearance to the Punchbowl Formation at Devil's Punchbowl (northwest along the SAf). However, paleontological work placed Cajon Valley strata in the Hemingfordian-Barstovian (18-14 Ma), as opposed to the Clarendonian-Hemphillian (13-9 Ma) Punchbowl Formation. Since the Cajon Valley formation was deposited prior to being truncated by the San Andreas fault, the 2400m-thick, laterally extensive subaerial deposits likely were deposited across what is now the fault trace. Restoring 310 km of dextral slip on the SAf system should indicate the location of offset equivalent sandstone. Restoration of slip on the SAf system places Cajon Valley adjacent to the Caliente and La Panza Ranges, east of San Luis Obispo. Although analysis of detrital zircon from Cenozoic sandstone throughout southern California has been crucial in establishing paleodrainage areas, detrital zircon from the Cajon Valley and equivalent formations had not been analyzed prior to this study. Paleocurrents measured throughout the Cajon Valley formation indicate a source to the NE, in the Mojave Desert. Sandstone samples analyzed in thin section using the Gazzi-Dickinson method of point-counting are homogeneously arkosic, with slight compositional variability, making differentiation of the Cajon Valley formation and potential offset equivalents problematic. However, Branch Canyon Sandstone and Santa Margarita Formation samples are compositionally the best match for the Cajon Valley formation. Detrital-zircon ages were determined from the Cajon Valley formation and related strata. These data are slightly more variable than sandstone composition, with distinct age peaks at 85-90 Ma, 150 Ma and 250 Ma. These ages correlate with batholiths in the SW Mojave Desert. Of the nine samples from six formations collected as potential offset equivalents, Branch Canyon and Santa Margarita samples are most similar to Cajon Valley samples, in terms of both detrital-zircon ages and sandstone composition. Based on 310km of post-Miocene offset on the San Andreas fault system, the Cajon Valley formation restores adjacent to shallow-marine sandstone of the Santa Margarita Formation and Branch Canyon Sandstone Member of the Monterey Formation in the Caliente and La Panza ranges. Cajon Valley sandstone is interpreted to represent a Miocene fluvial system on a coastal plain, flowing toward a delta on a narrow continental shelf.

Stang, Dallon Michael

395

Impact of climate changes from Middle Miocene onwards on evolutionary diversification in Eurasia: insights from the mesobuthid scorpions.  

PubMed

The aridification from Middle Miocene onwards has transformed the Asian interior into an arid environment, and the Pleistocene glacial-interglacial oscillations exerted further ecological impact. Therefore, both aridification and glaciation would have considerably influenced the evolution of many mid-latitude species in temperate Asia. Here, we tested this perspective by a phylogeographic study of the mesobuthid scorpions across temperate Asia using one mitochondrial and three nuclear genes. Concordant mitochondrial and nuclear gene trees were obtained, which are consistent with species tree inferred using a Bayesian approach. The age of the most recent common ancestor (MRCA) of all the studied scorpions was estimated to be 12.49 Ma (late Middle Miocene); Mesobuthus eupeus diverged from the clade composing Mesobuthus caucasicus and Mesobuthus martensii in early Late Miocene (10.21 Ma); M. martensii diverged from M. caucasicus at 5.53 Ma in Late Miocene. The estimated MRCA ages of M. martensii and the Chinese lineage of M. eupeus were 2.37 and 0.68 Ma, respectively. Central Asia was identified as the ancestral area for the lineage leading to M. martensii and M. caucasicus and the Chinese lineage of M. eupeus. The ancestral habitat of the genus Mesobuthus is likely to have been characterized by an arid environment; a shift towards more humid habitat occurred in the MRCA of M. martensii and a lineage of M. caucasicus, finally leading to the adaptation of M. martensii to humid environment. Our data strongly support the idea that the stepwise intensified aridifications from Mid-Miocene onwards drove the diversification of mesobuthid scorpions, and suggest that M. martensii and M. eupeus observed today in China originated from an ancestral lineage distributed in Central Asia. Both the colonization and the ensuing evolution of these species in East Asia appear to have been further moulded by Quaternary glaciations. PMID:23356513

Shi, Cheng-Min; Ji, Ya-Jie; Liu, Lin; Wang, Lei; Zhang, De-Xing

2013-03-01

396

The Miocene phosphogenic episode on the Florida platform: Implications for the positive. delta. sup 13 C excursion  

SciTech Connect

The authors propose that deposition and later alteration of the enormous phosphorite deposits of the southeastern US best explain the Miocene {delta}{sup 13}C excursion. The positive {delta}{sup 13}C shift in the early to early middle Miocene resulted from increased organic carbon burial rates when transgressive seas flooded the Florida platform and forced the Gulf Stream to migrate landward. Gulf Stream flow around topographic highs produced upwelling of P-rich water capable of sustaining high surface productivity. Organic carbon burial lowered P{sub CO{sub 2}} and eventually resulted in global cooling (reverse greenhouse effect). Cooling intensified oceanic circulation (coastal and equatorial upwelling), increased ice volume, and lowered eustatic sea level. The overall decrease in sea level exposed shallow-water shelf sediments to subaerial and supergene weathering. Most of the buried early Miocene organic matter was oxidized and caused {delta}{sup 13}C to shift back to its preexcursion level by the middle Miocene. Meteoric alteration removed organic matter and oxidized pyrite, but much of the diagenetic phosphorite, dolomite, and silica remained. The greenhouse effect from increased P{sub CO{sub 2}} eventually led to a marked slowdown in cooling and ice buildup as reflected in the slope of the global {delta}{sup 18}O curve. Available age dates for the organic-rich phosphatic member of the Monterey Formation suggest it was deposited after the maximum {delta}{sup 13}C positive shift. Oxidation of large amounts of organic carbon on the Florida platform may have lowered atmospheric O{sub 2} and enhanced organic matter preservation in deep-water basins of the circum Pacific during the middle Miocene.

Compton, J.S. (Univ. of South Florida, St. Petersburg (USA)); Snyder, S.W. (North Carolina State Univ., Raleigh (USA))

1990-05-01

397

Levoglucosan and other cellulose markers in pyrolysates of Miocene lignites: geochemical and environmental implications  

SciTech Connect

Using the pyrolysis-gas chromatography-mass spectrometry and off-line pyrolysis/silylation methods for lignites from three Miocene brown coal basins of Poland resulted in the characterization of many organic compounds, including dominant cellulose degradation products such as levoglucosan, 1,6-anhydro-{beta}-D-glucofuranose, and 1,4:3,6-dianhydroglucopyranose. Levoglucosan is a general source-specific tracer for wood smoke in the atmosphere and recent sediments. The presence of unusually high levels of this compound in brown coal pyrolysates suggests that a portion of this compound concentration in some airsheds may originate from lignite combustion. On the other hand, nonglucose anhydrosaccharides, in particular, mannosan and galactosan, typical of hemicellulose, are not detected in those lignite pyrolysates investigated. This indicates that mannosan and galactosan are better specific tracers for combustion of contemporary biomass in those regions where the utilization of brown coals containing fossilized cellulose is important. 7 refs., 2 figs., 3 tabs.

Daniele Fabbri; Leszek Marynowski; Monika J. Fabianska; Michal Zaton; Bernd R.T. Simoneit [University of Bologna, Ravenna (Italy)

2008-04-15

398