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

NASA Astrophysics Data System (ADS)

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

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

Closure Time of the Junggar-Balkhash Ocean: Constraints From Late Paleozoic Volcano-Sedimentary Sequences in the Barleik Mountains, West Junggar, NW China

NASA Astrophysics Data System (ADS)

Liu, Bo; Han, Bao-Fu; Chen, Jia-Fu; Ren, Rong; Zheng, Bo; Wang, Zeng-Zhen; Feng, Li-Xia

2017-12-01

The Junggar-Balkhash Ocean was a major branch of the southern Paleo-Asian Ocean. The timing of its closure is important for understanding the history of the Central Asian Orogenic Belt. New sedimentological and geochronological data from the Late Paleozoic volcano-sedimentary sequences in the Barleik Mountains of West Junggar, NW China, help to constrain the closure time of the Junggar-Balkhash Ocean. Tielieketi Formation (Fm) is dominated by littoral sediments, but its upper glauconite-bearing sandstone is interpreted to deposit rapidly in a shallow-water shelf setting. By contrast, Heishantou Fm consists chiefly of volcanic rocks, conformably overlying or in fault contact with Tielieketi Fm. Molaoba Fm is composed of parallel-stratified fine sandstone and sandy conglomerate with graded bedding, typical of nonmarine, fluvial deposition. This formation unconformably overlies the Tielieketi and Heishantou formations and is conformably covered by Kalagang Fm characterized by a continental bimodal volcanic association. The youngest U-Pb ages of detrital zircons from sandstones and zircon U-Pb ages from volcanic rocks suggest that the Tielieketi, Heishantou, Molaoba, and Kalagang formations were deposited during the Famennian-Tournaisian, Tournaisian-early Bashkirian, Gzhelian, and Asselian-Sakmarian, respectively. The absence of upper Bashkirian to Kasimovian was likely caused by tectonic uplifting of the West Junggar terrane. This is compatible with the occurrence of coeval stitching plutons in the West Junggar and adjacent areas. The Junggar-Balkhash Ocean should be finally closed before the Gzhelian, slightly later or concurrent with that of other ocean domains of the southern Paleo-Asian Ocean.

Late paleozoic fusulinoidean gigantism driven by atmospheric hyperoxia.

PubMed

Payne, Jonathan L; Groves, John R; Jost, Adam B; Nguyen, Thienan; Moffitt, Sarah E; Hill, Tessa M; Skotheim, Jan M

2012-09-01

Atmospheric hyperoxia, with pO(2) in excess of 30%, has long been hypothesized to account for late Paleozoic (360-250 million years ago) gigantism in numerous higher taxa. However, this hypothesis has not been evaluated statistically because comprehensive size data have not been compiled previously at sufficient temporal resolution to permit quantitative analysis. In this study, we test the hyperoxia-gigantism hypothesis by examining the fossil record of fusulinoidean foraminifers, a dramatic example of protistan gigantism with some individuals exceeding 10 cm in length and exceeding their relatives by six orders of magnitude in biovolume. We assembled and examined comprehensive regional and global, species-level datasets containing 270 and 1823 species, respectively. A statistical model of size evolution forced by atmospheric pO(2) is conclusively favored over alternative models based on random walks or a constant tendency toward size increase. Moreover, the ratios of volume to surface area in the largest fusulinoideans are consistent in magnitude and trend with a mathematical model based on oxygen transport limitation. We further validate the hyperoxia-gigantism model through an examination of modern foraminiferal species living along a measured gradient in oxygen concentration. These findings provide the first quantitative confirmation of a direct connection between Paleozoic gigantism and atmospheric hyperoxia. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Global plate boundary evolution and kinematics since the late Paleozoic

NASA Astrophysics Data System (ADS)

Matthews, Kara J.; Maloney, Kayla T.; Zahirovic, Sabin; Williams, Simon E.; Seton, Maria; Müller, R. Dietmar

2016-11-01

Many aspects of deep-time Earth System models, including mantle convection, paleoclimatology, paleobiogeography and the deep Earth carbon cycle, require high-resolution plate motion models that include the evolution of the mosaic of plate boundaries through time. We present the first continuous late Paleozoic to present-day global plate model with evolving plate boundaries, building on and extending two previously published models for the late Paleozoic (410-250 Ma) and Mesozoic-Cenozoic (230-0 Ma). We ensure continuity during the 250-230 Ma transition period between the two models, update the absolute reference frame of the Mesozoic-Cenozoic model and add a new Paleozoic reconstruction for the Baltica-derived Alexander Terrane, now accreted to western North America. This 410-0 Ma open access model provides a framework for deep-time whole Earth modelling and acts as a base for future extensions and refinement. We analyse the model in terms of the number of plates, predicted plate size distribution, plate and continental root mean square (RMS) speeds, plate velocities and trench migration through time. Overall model trends share many similarities to those for recent times, which we use as a first order benchmark against which to compare the model and identify targets for future model refinement. Except for during the period 260-160 Ma, the number of plates (16-46) and ratio of "large" plates (≥ 107.5 km2) to smaller plates ( 2.7-6.6) are fairly similar to present-day values (46 and 6.6, respectively), with lower values occurring during late Paleozoic assembly and growth of Pangea. This temporal pattern may also reflect difficulties in reconstructing small, now subducted oceanic plates further back in time, as well as whether a supercontinent is assembling or breaking up. During the 260-160 Ma timeframe the model reaches a minima in the number of plates, in contrast to what we would expect during initial Pangea breakup and thus highlighting the need for refinement

Devonian paleomagnetism of the North Tien Shan: Implications for the middle-Late Paleozoic paleogeography of Eurasia

NASA Astrophysics Data System (ADS)

Levashova, Natalia M.; Mikolaichuk, Alexander V.; McCausland, Philip J. A.; Bazhenov, Mikhail L.; Van der Voo, Rob

2007-05-01

The Ural-Mongol belt (UMB), between Siberia, Baltica and Tarim, is widely recognized as the locus of Asia's main growth during the Paleozoic, but its evolution remains highly controversial, as illustrated by the disparate paleogeographic models published in the last decade. One of the largest tectonic units of the UMB is the Kokchetav-North Tien Shan Domain (KNTD) that stretches from Tarim in the south nearly to the West Siberian Basin. The KNTD comprises several Precambrian microcontinents and numerous remnants of Early Paleozoic island arcs, marginal basins and accretionary complexes. In Late Ordovician time, all these structures had amalgamated into a single contiguous domain. Its paleogeographic position is of crucial importance for elucidating the Paleozoic evolution of the UMB in general and of the Urals in particular. The Aral Formation, located in Kyrgyzstan in the southern part of the KNTD, consists of a thick Upper Devonian (Frasnian) basalt-andesite sequence. Paleomagnetic data show a dual-polarity characteristic component (Dec/Inc = 286° / + 56°, α95 = 9°, k = 21, N = 15 sites). The primary origin of this magnetization is confirmed by a positive test on intraformational conglomerates. We combine this result with other Paleozoic data from the KNTD and show its latitudinal motion from the Late Ordovician to the end of the Paleozoic. The observed paleolatitudes are found to agree well with the values extrapolated from Baltica to a common reference point (42.5°N, 73°E) in our sampling area for the entire interval; hence coherent motion of the KNTD and Baltica is strongly indicated for most of the Paleozoic. This finding contradicts most published models of the UMB evolution, where the KNTD is separated from Baltica by a rather wide Ural Ocean containing one or more major plate boundaries. An exception is the model of Şengör and Natal'in [A.M.C. Şengör, B.A. Natal'in, Paleotectonics of Asia: fragments of a synthesis, in: A. Yin and M. Harrison (eds

Tectonic transition associated with Kazakhstan Orocline in the Late Paleozoic: magmatic archives of western Chinese Tianshan

NASA Astrophysics Data System (ADS)

Cai, Keda

2016-04-01

Kazakhstan accretionary system was a principle component of the Central Asian Orogenic Belt (CAOB) that is one of the largest accretionary orogens on earth. The Kazakhstan composite continent could have been established in the Early Paleozoic by the Kazakhstan accretionary system in the form of progressively amalgamations of diverse tectonic units, such as continental ribbon, accretionary prim, oceanic remnant and arc material. Subsequently, the composite continent was bended to form a spectacular U-shaped architecture that probably occurred in the Late Paleozoic. The western Chinese Tianshan is situated on the south wing of the Kazakhstan Orocline, featured by extensive magmatim, intense deformation and voluminous mineralization. Our new geochronological and geochemical data suggest a noticeable magmatic gap between Late Devonian and Early carboniferous and contrasting magma sources of these magmatic rocks. The significant shifts correspond to the tectonic transition from terrane amalgamation to mountain bending in the Early Paleozoic. This study was financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China (2014CB448000), Xinjiang outstanding youth scientific grant (2013711003) and the Talent Awards to KDC from the China Government under the 1000 Talent Plan.

Late Paleozoic tectonic evolution of the Central Asian Orogenic Belt: Constraints from multiple arc-basin systems in Altai-Junggar area, NW China

NASA Astrophysics Data System (ADS)

Li, D.

2015-12-01

In this study, we report results from integrated geological, geophysical and geochemical investigations on the Wulungu Depression of the Junggar Basin to understand the Late Paleozoic continental growth of the Junggar area and its amalgamation history with the Altai terrane, within the broad tectonic evolution of the Altai-Junggar area. Based on seismic and borehole data, the Wulungu Depression can be divided into two NW-trending tectonic units by southward thrust faults. The Suosuoquan Sag is composed of gray basaltic andesite, andesite, tuff, tuffaceous sandstone and tuffite, and the overlying Early Carboniferous volcano-sedimentary sequence with lava gushes and marine sediments from a proximal juvenile provenance, compared to the andesite in the Hongyan High. The SIMS Zircon U-Pb ages for andesites from Late Paleozoic strata indicate that these volcanics in Suosuoquan Sag and Hongyan High erupted at 376.3Ma and 313.4Ma, respectively. Most of the intermediate-mafic volcanic rocks exhibit calc-alkaline affinity, low initial 87Sr/86Sr and positive ɛNd(t) and ɛHf(t) values. Furthermore, these rocks have high Th/Yb and low Ce/Pb and La/Yb ratios as well as variable Ba/Th and Ba/La ratios. These features imply that the rocks were derived from partial melting of a mantle wedge metasomatized by subduction-related components in an island arc setting. The basin filling pattern and the distribution of island arc-type volcanics and their zircon Hf model ages with the eruptive time suggest that the Wulungu Depression represents an island arc-basin system with the development of a Carboniferous retro-arc basin. The gravity and magnetic anomaly data suggest that Altai-Junggar area incorporates three arc-basin belts from north to south: the Karamaili-Luliang-Darbut, Yemaquan-Wulungu, and Dulate-Fuhai-Saur. The recognition of the Wulungu arc-basin system demonstrates that the northern Junggar area is built by amalgamation of multiple Paleozoic linear arcs and accretionary

Late-paleozoic granitoid complexes of the southwest Primorye: geochemistry, age and typification

NASA Astrophysics Data System (ADS)

Veldemar, A. A.; Vovna, G. M.

2017-12-01

The article presents the first data of geochemical studies of the Late Permian granitoids of the Gamov Complex located in the southwestern part of the Voznesenskiy terrane. The purpose of the study was to identify the main geochemical features of the Late Paleozoic granitoids of the southwestern Primorye, which in the future will allow us to draw conclusions about the petrogenesis of these granitoids. Elemental analysis of 20 samples was carried out, conducted statistical and mathematical processing of the data, have been constructed representative diagrams and graphs for this group of rocks. Elemental analysis was performed by atomic emission (ICP-AES) and inductively-coupled-plasma (ICP-MS) mass spectrometry, at the Analytical Center FEGI FEB RAS.

Provenance analysis of the Late Paleozoic sedimentary rocks in the Xilinhot Terrane, NE China, and their tectonic implications

NASA Astrophysics Data System (ADS)

Han, Jie; Zhou, Jian-Bo; Wilde, Simon A.; Song, Min-Chun

2017-08-01

The Xilinhot Terrane is located in the eastern segment of the Central Asian Orogenic Belt in NE China, and is a key to a hotly debated issue on the Paleozoic tectonic evolution of this giant progenic belt. To constrain the tectonic evolution of the Xilinhot Terrane in the Late Paleozoic, we undertook zircon U-Pb dating and geochemical analyses of the Zhesi and Benbatu formations in the Suolun and Xi Ujimqin areas in the Xilinhot Terrane. Samples of the Benbatu Formation yield detrital zircon U-Pb ages ranging from 2659 Ma to 316 Ma, with four age populations at: 2659-1826 Ma, 1719-963 Ma, 590-402 Ma, and 396-316 Ma, whereas samples from the Zhesi Formation yield detrital zircon U-Pb ages ranging from 1967 Ma to 250 Ma, with four age populations at: 1967-1278 Ma, 971-693 Ma, 561-403 Ma, and 399-250 Ma. The age groups of both the Benbatu and Zhesi formations in the Xilinhot Terrane are similar to those in other parts of the Central Asian Orogenic Belt (CAOB). This evidence indicates that the Xilinhot Terrane is a microcontinent, and not an accretionary complex as previously thought. Furthermore, the youngest zircon grains in the Benbatu and Zhesi formations yield weighted mean 206Pb/238U ages of 322 ± 12 Ma (MSDW = 0.12, n = 4) and 257 ± 2.8 Ma (MSDW = 1.6, n = 8), respectively. Combined with fossil data, our new data suggest that the Benbatu and Zhesi formations in the Xilinhot Terrane were possibly deposited at ∼322 Ma and ∼257 Ma, respectively. Based on the provenance of the Carboniferous-Permian sandstones came from the blocks of NE China, we speculate that the Xilinhot Terrane is the western part of the Songliao block.

Criteria for the recognition and correlation of sandstone units in the Precambrian and Paleozoic-Mesozoic clastic sequence in the near east

NASA Astrophysics Data System (ADS)

Weissbrod, T.; Perath, I.

A systematic study of the Precambrian and Paleozoic-Mesozoic clastic sequences (Nubian Sandstone) in Israel and Sinai, and a comparative analysis of its stratigraphy in neighbouring countries, has shown that besides the conventional criteria of subdivision (lithology, field appearance, photogeological features, fossil content), additional criteria can be applied, which singly or in mutual conjuction enable the recognition of widespread units and boundaries. These criteria show lateral constancy, and recurrence of a similar vertical sequence over great distances, and are therefore acceptable for the identification of synchronous, region-wide sedimentary units (and consequently, major unconformities). They also enable, once the units are established, to identify detached (not in situ) samples, samples from isolated or discontinous outcrops, borehole material or archive material. The following rock properties were tested and found to be usefuls in stratigraphic interpretation, throughout large distribution areas of the clastic sequence: Landscape, which is basically the response of a particular textural-chemic al aggregate to atmospheric weathering. Characteristic outcrop feature — styles of roundness or massivity, fissuring or fliatin, slope profile, bedding — express a basic uniformity of these platform-type clastics. Colors are often stratigraphically constant over hundreds of kilometers, through various climates and topographies, and express some intrinsic unity of the rock bodies. Grain size and sorting, when cross-plotted, enable to differentiate existing unit. The method requires the analysis of representative numbers of samples. Vertical trends of median grain size and sorting show reversals, typically across unconformities. Feldstar content diminishes from 15-50% in Precambrian-Paleozoic rocks to a mere 5% or less in Mesozoic sandstones — a distinctive regionwide time trend. Dominance of certain feldstar types characterizes Precambrian and Paleozoic

Mineralogy and diagenesis of low-permeability sandstones of Late Cretaceous age, Piceance Creek Basin, northwestern Colorado

USGS Publications Warehouse

Hansley, Paula L.; Johnson, Ronald C.

1980-01-01

This report presents preliminary results of a mineralogic and diagenetic study of some low-permeability sandstones from measured surface sections and cores obtained from drill holes in the Piceance Creek Basin of northwestern Colorado. A documentation of the mineralogy and diagenetic history will aid in the exploration for natural gas and in the development of recovery technology in these low-permability sandstones. These sandstones are in the nonmarine upper part of the Mesaverde Formation (or Group) of Late Cretaceous age and are separated from overlying lower Tertiary rocks by a major regional unconformity. Attention is focused on the sandstone units of the Ohio Creek Member, which directly underlies the unconformity; however, comparisons between the mineralogy of the Ohio Creek strata and that of the underlying sandstone units are made whenever possible. The Ohio Creek is a member of the Hunter Canyon Formation (Mesaverde Group) in the southwestern part of the basin, and the Mesaverde Formation in the southern and central parts of the basin. The detrital mineralogy is fairly constant throughout all of these nonrnarine Cretaceous sandstone units; however, in the southeastern part of the basin, there is an increase in percentage of feldspar, quartzite, and igneous rock fragments in sandstones of the Ohio Creek Member directly underlying the unconformity. In the southwestern part of the basin, sandstones of the Ohio Creek Member are very weathered and are almost-entirely comprised of quartz, chert, and kaolinite. A complex diagenetic history, partly related to the overlying unconformity, appears to be responsible for transforming these sandstones into potential gas reservoirs. The general diagenetic sequence for the entire Upper Cretaceous interval studied is interpreted to be (early to late): early(?) calcite cement, chlorite, quartz overgrowths, calcite cement, secondary porosity, analcime (surface only), kaolinite and illite, and late carbonate cements

The development of floristic provinciality during the Middle and Late Paleozoic

USGS Publications Warehouse

Wnuk, C.

1996-01-01

Phytogeographic reconstructions have been published for most Paleozoic series since the Pr??i??doli??, but there have been few attempts to synthesize this data into a comprehensive review of the characteristics and causes of the changing phytogeographic patterns for the whole Paleozoic history of the vascular flora. Existing floristic analyses have been compiled in this manuscript and the resulting data are used to reconstruct the evolution of floristic provinces since the Silurian. The earliest plant fossil records indicate that provinciality was characteristic of terrestrial vascular plant distributions right from the beginning of terrestrial colonization by vascular plants. This interpretation differs markedly from the views of many workers who still maintain that pre-Upper Carboniferous floras were uniform and cosmopolitan in distribution. Three of the four major phytogeographic units, i.e. Angara, Euramerica, and Gondwana, can be recognized in the earliest fossil floras. The fourth unit, Cathaysia, differentiated from Euramerica during the late Upper Carboniferous. Phytogeographic differentiation occurs in direct response to climatic gradients and physiographic barriers. As these gradients and barriers change, provincial boundaries expand and contract, fragment, reassemble and reassort. Phytogeographic units are dynamic through time. ?? 1996 Elsevier Science B.V. All rights reserved.

Carboniferous - Early Permian magmatic evolution of the Bogda Range (Xinjiang, NW China): Implications for the Late Paleozoic accretionary tectonics of the SW Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Wali, Guzalnur; Wang, Bo; Cluzel, Dominique; Zhong, Linglin

2018-03-01

The Late Paleozoic magmatic evolution of the Bogda Range (Chinese North Tianshan) is important for understanding the accretionary history of the Central Asian Orogenic Belt. We investigated the Carboniferous and Lower Permian volcanic and sedimentary sequences of the Daheyan section, southern Bogda Range, and present new zircon U-Pb ages and whole-rock geochemical data for the volcanic rocks. One Carboniferous rhyolite is dated at 298 ± 8 Ma; a Permian basalt yielded many Proterozoic zircon xenocrysts, and its maximum age (∼297 Ma) is constrained by the detrital zircon ages of the sandstone that stratigraphically underlies it. These volcanic rocks belong to calc-alkaline series. We further synthesize previous geochronological, geochemical and isotopic data of magmatic and sedimentary rocks in the Bogda Range. The available data indicate that the magmatism occurred continuously from 350 Ma to 280 Ma. A comprehensive analysis allows us to propose that: (1) the Carboniferous to Early Permian magmatic rocks of the Bogda Range generally show consistent arc-type features; (2) increasing mantle input through time suggests intra-arc extension in a supra-subduction zone; (3) the localized occurrence of Early Permian alkaline pillow basalts and deep water sediments close to the major shear zone advocate a transtensional crustal thinning during the transition from Carboniferous convergence to Early Permian transcurrent tectonics; (4) occurrence of a large number of Proterozoic zircon xenocrysts in the Late Paleozoic magmatic rocks, and Proterozoic detrital zircons in the coeval clastic sediments suggest a continental or transitional basement of the Bogda Arc; (5) subduction in the Bogda area terminated prior to the deposition of Middle Permian terrestrial sediments.

The rise and fall of late Paleozoic trilobites of the United States

USGS Publications Warehouse

Brezinski, D.K.

1999-01-01

Based on range data and generic composition, four stages of evolution are recognized for late Paleozoic trilobites of the contiguous United States. Stage 1 occurs in the Lower Mississippian (Kinderhookian-Osagean) and is characterized by a generically diverse association of short-ranging, stenotopic species that are strongly provincial. Stage 2 species are present in the Upper Mississippian and consist of a single, eurytopic, pandemic genus, Paladin. Species of Stage 2 are much longer-ranging than those of Stage 1, and some species may have persisted for as long as 12 m.y. Stage 3 is present within Pennsylvanian and Lower Permian strata and consists initially of the eurytopic, endemic genera Sevillia and Ameura as well as the pandemic genus Ditomopyge. During the middle Pennsylvanian the very long-ranging species Ameura missouriensis and Ditomopyge scitula survived for more than 20 m.y. During the late Pennsylvanian and early Permian, a number of pandemic genera appear to have immigrated into what is now North America. Stage 4 is restricted to the Upper Permian (late Leonardian-Guadalupian) strata and is characterized by short-ranging, stenotopic, provincial genera. The main causal factor controlling the four-stage evolution of late Paleozoic trilobites of the United States is interpreted to be eustacy. Whereas Stage 1 represents an adaptive radiation developed during the Lower Mississippian inundation of North America by the Kaskaskia Sequence, Stage 2 is present in strata deposited during the regression of the Kaskaskia sea. Stage 3 was formed during the transgression and stillstand of the Absaroka Sequence and, although initially endemic, Stage 3 faunas are strongly pandemic in the end when oceanic circulation patterns were at a maximum. A mid-Leonardian sea-level drop caused the extinction of Stage 3 fauna. Sea-level rise near the end of the Leonardian and into the Guadalupian created an adaptive radiation of stentopic species of Stage 4 that quickly became

Late Paleozoic to Cenozoic reconstruction of the Arctic

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

Smith, D.G.

1985-04-01

The plate tectonic evolution of the Arctic is reassessed in the context of the known histories of the North Atlantic and North Pacific Oceans, and of the tectono-stratigraphic development of the lands around the Arctic Ocean. Computer map-drawing facilities were used to provide geometrical constraints on the reconstructions, which are presented to in the form of eight palinispatic maps. Stratigraphic similarities among presently dispersed continental areas identify fragments of a former Barents plate. Collision of this plate with the Euramerican plate was the cause of the Late Devonian Ellesmerian orogeny. In later Paleozoic time, the Siberian continent also joined Pangeamore » by collision with the combined Barents and Euramerican plates along the Ural-Taymyr suture. The Mesozoic-Cenozoic history of the Arctic is concerned with the fragmentation and dispersal of the former Barents plate, as well as the accretion of new continental fragments from the Pacific.« less

The Implementation of 2-D Resistivity Method in Verifying Paleozoic Aquifer Properties at Bukit Chondong, Perlis (Malaysia)

NASA Astrophysics Data System (ADS)

Maslinda, Umi; Nordiana, M. M.; Bery, A. A.; Afiq Saharudin, Muhamad; Hisham, Hazrul; Taqiuddin, Z. M.; Sulaiman, Nabila; Nur Amalina, M. K. A.; Nordiana, A. N.

2017-04-01

The research was conducted using 2-D resistivity in verifying Paleozoic aquifer. Since most geologic materials behave as electrical insulators, surface measurements of earth resistivity are controlled by the electrolytic ability of interstitial water. The subsurface distribution of water is controlled by the porosity of the formations. The study area is at Bukit Chondong, Beseri, Perlis. Bukit Chondong is made of sedimentary rock which mostly is sandstone. Bukit Chondong is from uppermost of the Kubang Pasu Formation that represented by a thick unit of grey mudstone interbedded with sandstone. The Kubang Pasu Formation was influenced by shallow marine during the early age. Paleocurrent and fossils traces were found on the mudstone at the study area. The area is suspected to be a Paleozoic aquifer because the sandstone can be a productive aquifer with diffuse flow. The water movement in sandstone is through the fractures and joints. Most of the water stores and transmits in sandstone. The interbedded sandstone and mudstone is one of the aquifer characteristic. Sandstone and mudstone are water-bearing rocks and low-permeable rocks respectively. The data was processed according to the geological information of the study area since there was an outcrop. The study area have low resistivity value which both sandstone and mudstone give less than 800 Ohm-m due to the water content (Sulphide and clay).

U-Pb Detrital Zircon Geochronologic Constraints on Depositional Age and Sediment Source Terrains of the Late Paleozoic Tepuel-Genoa Basin

NASA Astrophysics Data System (ADS)

Griffis, N. P.; Montanez, I. P.; Isbell, J.; Gulbranson, E. L.; Wimpenny, J.; Yin, Q. Z.; Cúneo, N. R.; Pagani, M. A.; Taboada, A. C.

2014-12-01

The late Paleozoic Ice Age (LPIA) is the longest-lived icehouse of the Phanerozoic and the only time a metazoan dominated and vegetated world transitioned from an icehouse climate into a greenhouse. Despite several decades of research, the timing, extent of glaciation and the location of ice centers remain unresolved, which prohibits reconstruction of ice volume. The Permo-Carboniferous sediments in the Tepuel-Genoa Basin, Patagonia contains a near complete record of sedimentation from the lower Carboniferous through lower Permian. Outsized clasts, thin pebble-rich diamictites and slumps represent the last of the late Paleozoic glacially influenced deep-water marine sediments in the Mojón de Hierro Fm. and the Paleozoic of Patagonia. U-Pb analysis of detrital zircons separated from slope sediments reveal groupings (20 myr bins, n≥5 zircons) with peak depositional ages of 420, 540 to 660 and 1040 Ma. Zircon age populations recovered from the Mojón de Hierro Fm. compare well with bedrock ages of the Deseado Massif of SE Patagonia, suggesting this may be a potential source of sediments. The maximum depositional age of the sediments is 306.05 ± 3.7 Ma (2σ) as determined by the median age of the two youngest concordant zircons that overlap in error. The youngest zircon from the analysis yields a 238U/206Pb age of 301.3 ± 4.5 Ma (2σ; MSWD = 2.3). Younger zircons from the analysis compare well with the age of granite bedrock exposed along the basin margin to the E-NE suggesting they may reflect a more proximal source. These data, which indicate a maximum age of late Carboniferous for the Mojón de Hierro Fm, provide the first geochemical constraints for the timing of final deposition of glaciomarine sediments in the Tepuel-Genoa Basin, and contributes to the biostratigraphic correlation of the late Paleozoic succession in Patagonia with other key LPIA basins that has thus far been hindered by faunal provincialism.

A New Paleozoic Symmoriiformes (Chondrichthyes) from the Late Carboniferous of Kansas (USA) and Cladistic Analysis of Early Chondrichthyans

PubMed Central

Pradel, Alan; Tafforeau, Paul; Maisey, John G.; Janvier, Philippe

2011-01-01

Background The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians) into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters. Methodology/Principal Findings On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii) form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters. Conclusions/Significance Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters. PMID:21980367

A new paleozoic Symmoriiformes (Chondrichthyes) from the late Carboniferous of Kansas (USA) and cladistic analysis of early chondrichthyans.

PubMed

Pradel, Alan; Tafforeau, Paul; Maisey, John G; Janvier, Philippe

2011-01-01

The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians) into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters. On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii) form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters. Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters.

Conodonts of the western Paleozoic and Triassic belt, Klamath Mountains, California and Oregon

USGS Publications Warehouse

Irwin, William P.; Wardlaw, Bruce R.; Kaplan, T.A.

1983-01-01

Conodonts were extracted from 32 samples of limestone and 5 samples of chert obtained from the Western Paleozoic and Triassic belt of the Klamath Mountains province. Triassic conodonts were found in 17 samples, and late Paleozoic conodonts in 7 samples. Conodonts of the remaining 13 samples cannot be dated more closely than early or middle Paleozoic through Triassic. The late Paleozoic conodonts are restricted to the North Fork and Hayfork terranes. The Hayfork terrane also contains Early, Middle, and Late Triassic conodonts; mostly Neogondolella. Conodonts from samples of the Rattlesnake Creek terrane and the northern undivided part of the belt are all Late Triassic and are generally Epigondolella. The conodont data support the concept that many of the limestone bodies are olistoliths or tectonic blocks in melange. Color alteration of the conodonts indicates that the rocks of the Western Paleozoic and Triassic belt have been heated to temperatures between 300 degrees and 500 degrees C during regional tectonism.

Late Paleozoic tectonic evolution and concentrated mineralization in Balkhash and West Junggar, western part of the Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Dong, Shuwen; Chen, Xuanhua; Chen, Zhengle

2016-04-01

The Central Asia Orogenic Belt (CAOB) is an important area with significant growth of the crust and metallogeny in the Late Paleozoic. The Balkhash-Junggar tectono-metallogenic belt consists of the Balkhash, the West Junggar, and the East Junggar tectono-metallogenic belts in western part of the Central Asian Orogenic Belt (CAOB). According to the structural geological relationship, the East Junggar, the West Junggar, and the Balkhash belts are considered to be once a continuous E-W-trending tectono-metallogenic belt in Late Carboniferous. The West Junggar belt is featured with NE-trending left-lateral strike-slip faulting tectonic system (WJTS), while the left-lateral strike-slip faults are E-W-trending in the Balkhash belt. The WJTS consists of the Darabut, the Mayile, and the Baerluke faults, and the blocks among them. All these left-lateral strike-slip faults are forming due to the transition of tectonic settings from syn-collisional orogeny to post-collisional extension during the closure of the ocean (the Junggar Sea) in Late Carboniferous, with significant intrusion of batholiths and crust growth occurred in this period. These faults are truncated by the right-lateral strike-slip faults, such as the Chingiz-Junggar fault, and the Central Balkhash fault in Mesozoic. The Balkhash-Junggar tectono-metallogenic belt is important for the occurrence of many well-known super-large and large porphyry Cu-Mo deposits (such as the Kounrad, the Aktogai, the Borly, and the Baogutu deposits), large skarn Cu deposits (in the Sayak ore-filed), large rare metal deposits (such as the East Kounrad, the Zhanet, and the Akshatau deposits), and large gold deposits (such as the Hatu deposit). Zircon U-Pb ages, Re-Os isotopic dating of molybdenites, 40Ar/39Ar thermochronology of hornblendes, muscovites, biotites, and K-feldspars, and zircon and apatite fission track (FT) and (U-Th)/He dating and thermal history modeling, provide a multidisciplinary approach to constrain the whole

Geology of Paleozoic Rocks in the Upper Colorado River Basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, Excluding the San Juan Basin

USGS Publications Warehouse

Geldon, Arthur L.

2003-01-01

The geology of the Paleozoic rocks in the Upper Colorado River Basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, was studied as part of the U.S. Geological Survey's Regional Aquifer-System Analysis Program to provide support for hydrogeological interpretations. The study area is segmented by numerous uplifts and basins caused by folding and faulting that have recurred repeatedly from Precambrian to Cenozoic time. Paleozoic rocks in the study area are 0-18,000 feet thick. They are underlain by Precambrian igneous, metamorphic, and sedimentary rocks and are overlain in most of the area by Triassic formations composed mostly of shale. The overlying Mesozoic and Tertiary rocks are 0-27,000 feet thick. All Paleozoic systems except the Silurian are represented in the region. The Paleozoic rocks are divisible into 11 hydrogeologic units. The basal hydrogeologic unit consisting of Paleozoic rocks, the Flathead aquifer, predominantly is composed of Lower to Upper Cambrian sandstone and quartzite. The aquifer is 0-800 feet thick and is overlain gradationally to unconformably by formations of Cambrian to Mississippian age. The Gros Ventre confining unit consists of Middle to Upper Cambrian shale with subordinate carbonate rocks and sandstone. The confining unit is 0-1,100 feet thick and is overlain gradationally to unconformably by formations of Cambrian to Mississippian age. The Bighom aquifer consists of Middle Cambrian to Upper Ordovician limestone and dolomite with subordinate shale and sandstone. The aquifer is 0-3,000 feet thick and is overlain unconformably by Devonian and Mississipplan rocks. The Elbert-Parting confining unit consists of Lower Devonian to Lower Mississippian limestone, dolomite, sandstone, quartzite, shale, and anhydrite. It is 0-700 feet thick and is overlain conformably to unconformably by Upper Devonian and Mississippian rocks. The Madison aquifer consists of two zones of distinctly different lithology. The lower (Redwall-Leadville) zone

The Juchatengo complex: an upper-level ophiolite assemblage of late Paleozoic age in Oaxaca, southern Mexico

NASA Astrophysics Data System (ADS)

Grajales-Nishimura, José Manuel; Ramos-Arias, Mario Alfredo; Solari, Luigi; Murillo-Muñetón, Gustavo; Centeno-García, Elena; Schaaf, Peter; Torres-Vargas, Ricardo

2018-04-01

The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated by late Paleozoic magmatism. It consists of mafic and sedimentary rocks that have oceanic affinities, with internal pseudostratigraphic, structural and metamorphic characteristics, which resemble a typical upper-level ophiolite assemblage. New U-Pb zircon and previous hornblende K-Ar analyses yield ages of ca. 291-313 Ma (U-Pb) for plagiogranites and ca. 282-277 Ma for tonalites intruding the entire sequence, including pelagic sediments at the top, with a maximum deposition age of ca. 278 Ma and noteworthy local provenance. These data constrain the age of the JC to the Late Pennsylvanian-Early Permian period. Hf isotopic analyses obtained from zircons in the JC plagiogranite and tonalite show that they come from a similar primitive mantle source (176Hf/177Hf: 0.282539-0.283091; ƐHf(t): + 3.2 to + 15.0). ƐHf(t) values from near 0 to - 2.8 in the tonalites indicate a contribution from the continental crust. Trace elements and REE patterns in whole rock and zircons point to a primitive mantle source for differentiated mafic, plagiogranite dykes and tonalitic plutons. Geochronological and geochemical data address the generation of new oceanic crust above the subduction zone, probably in a backarc setting. In this tectonic scenario, the JC ophiolite originated due to the convergence of the paleo-Pacific plate below the already integrated Oaxacan and Acatlán complexes in western Pangea. The dextral displacement places the deformation in a transtensional regime during the late Paleozoic age.

Paleoclimatic and paleomagnetic constraints on the Paleozoic reconstructions of south China, north China and Tarim

NASA Astrophysics Data System (ADS)

Shangyou, Nie

1991-10-01

Paleomagnetic and paleoclimatic data provide the most useful latitudinal constraints for plate reconstructions. Distributions through the Paleozoic of five types of climatically sensitive sediments (coals, evaporites, reefs, dolomites and limestones) for south China, north China and Tarim are shown on 15 maps that include 1578 reliable data points. These paleoclimatic data agree reasonably well with available paleomagnetic directions, although significant divergence between the two exists for the Early Paleozoic. These data indicate the following: (1) South China was in low latitudes during the entire Paleozoic, with a subtropical position in the Cambrian. (2) North China also remained near the equator in the Early and Late Paleozoic, except for the Ordovian and the Late Permian when extensive evaporites suggest slightly higher latitudinal positions, while its Middle Paleozoic position is uncertain due to the missing stratigraphie record. (3) In south China, local tectonics appears to have played a dominant role in determining paleogeography and therefore marine sedimentation, especially after the Late Ordovician-Early Silurian, because the areal coverage of marine sediments through time is distinctly different from what would be expected from published global sea-level curves. (4) Paleoclimatic and paleomagnetic data are compatible with biogeographic data which suggest that south China was part of eastern Gondwana in the Early Paleozoic, but was widely separated from Gondwana in the Late Paleozoic, and the split between the two probably happened in the Devonian, giving rise to a major break-up unconformity in central south China.

Assessment of Appalachian basin oil and gas resources: Utica-Lower Paleozoic Total Petroleum System: Chapter G.10 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

Both conventional oil and gas resources and continuous (unconventional) gas resources are present in the UticaLower Paleozoic TPS. Conventional oil and gas resources in the Utica-Lower Paleozoic TPS were assessed by the U.S. Geological Survey (USGS) in 2002 in the following assessment units (AU): (1) the Lower Paleozoic Carbonates in Thrust Belt AU, (2) the Knox Unconformity AU, (3) the Black River-Trenton Hydrothermal Dolomite AU, and (4) the Lockport Dolomite AU. The total estimated undiscovered oil and gas resources for these four AUs, at a mean value, was about 46 million barrels of oil (MMBO) and about 3 trillion cubic feet of gas (TCFG), respectively. In contrast, continuous (unconventional) gas resources in the TPS were assessed by the USGS in 2002 in four AUs associated with the “Clinton” sandstone, Medina sandstone, Medina Group sandstones, Tuscarora Sandstone, and sandstones in the Queenston Shale. The total estimated undiscovered gas for these four AUs, at a mean value, was about 26.8 TCFG. A hypothetical Utica Shale AU for oil(?) and continuous gas is identified in this report. In 2012, the Utica Shale was recognized by the USGS as a continuous AU and was assessed by Kirschbaum and others (2012).

Paleozoic subduction complex and Paleozoic-Mesozoic island-arc volcano-plutonic assemblages in the northern Sierra terrane

USGS Publications Warehouse

Hanson, Richard E.; Girty, Gary H.; Harwood, David S.; Schweickert, Richard A.

2000-01-01

This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly Complex) overlain by submarine arc-related deposits that record the evolution of three separate island-arc systems in the Late Sevonian-Early Mississippian, Permian, and Late Triassic-Jurassic. The two Paleozoic are packages and the underlying Shoo Fly Complex have an important bearing on plate-tectonic processes affecting the convergent margin outboard of the Paleozoic Cordilleran miogeocline, although their original paleogeographic relations to North America are controversial. The third arc package represents an overlap assemblage that ties the terrane to North America by the Late Triassic and helps constrain the nature and timing of Mesozoic orogenesis. Several of the field-trip stops examine the record of pre-Late Devonian subduction contained in the Shoo Fly Complex, as well as the paleovolcanology of the overlying Devonian to Jurassic arc rocks. Excellent glaciated exposures provide the opportunity to study a cross section through a tilted Devonian volcano-plutonic association. Additional stops focus on plutonic rocks emplaced during the Middle Jurassic arc magmatism in the terrane, and during the main pulse of Cretaceous magmatism in the Sierra Nevada batholith to the east.

Detrital zircon age distribution from Devonian and Carboniferous sandstone in the Southern Variscan Fold-and-Thrust belt (Montagne Noire, French Massif Central), and their bearings on the Variscan belt evolution

NASA Astrophysics Data System (ADS)

Lin, Wei; Faure, Michel; Li, Xian-hua; Chu, Yang; Ji, Wenbin; Xue, Zhenhua

2016-05-01

In the Southern French Massif Central, the Late Paleozoic sedimentary sequences of the Montagne Noire area provide clues to decipher the successive tectonic events that occurred during the evolution of the Variscan belt. Previous sedimentological studies already demonstrated that the siliciclastic deposits were supplied from the northern part of the Massif Central. In this study, detrital zircon provenance analysis has been investigated in Early Devonian (Lochkovian) conglomerate and sandstone, and in Carboniferous (Visean to Early Serpukhovian) sandstone from the recumbent folds and the foreland basin of the Variscan Southern Massif Central in Montagne Noire. The zircon grains from all of the samples yielded U-Pb age spectra ranging from Neoarchean to Late Paleozoic with several age population peaks at 2700 Ma, 2000 Ma, 980 Ma, 750 Ma, 620 Ma, 590 Ma, 560 Ma, 480 Ma, 450 Ma, and 350 Ma. The dominant age populations concentrate on the Neoproterozoic and Paleozoic. The dominant concordant detrital zircon age populations in the Lochkovian samples, the 480-445 Ma with a statistical peak around 450 Ma, are interpreted as reflecting the rifting event that separated several continental stripes, such as Armorica, Mid-German Crystalline Rise, and Avalonia from the northern part of Gondwana. However, Ediacaran and Cambrian secondary peaks are also observed. The detrital zircons with ages at 352 - 340 Ma, with a statistical peak around 350 Ma, came from the Early Carboniferous volcanic and plutonic rocks similar to those exposed in the NE part of the French Massif Central. Moreover, some Precambrian grains recorded a more complex itinerary and may have experienced a multi-recycling history: the Archean and Proterozoic grains have been firstly deposited in Cambrian or Ordovician terrigenous rocks, and secondly re-sedimented in Devonian and/or Carboniferous formations. Another possibility is that ancient grains would be inherited grains, scavenged from an underlying but not

Climate and vegetational regime shifts in the late Paleozoic ice age earth.

PubMed

DiMichele, W A; Montañez, I P; Poulsen, C J; Tabor, N J

2009-03-01

The late Paleozoic earth experienced alternation between glacial and non-glacial climates at multiple temporal scales, accompanied by atmospheric CO2 fluctuations and global warming intervals, often attended by significant vegetational changes in equatorial latitudes of Pangaea. We assess the nature of climate-vegetation interaction during two time intervals: middle-late Pennsylvanian transition and Pennsylvanian-Permian transition, each marked by tropical warming and drying. In case study 1, there is a catastrophic intra-biomic reorganization of dominance and diversity in wetland, evergreen vegetation growing under humid climates. This represents a threshold-type change, possibly a regime shift to an alternative stable state. Case study 2 is an inter-biome dominance change in western and central Pangaea from humid wetland and seasonally dry to semi-arid vegetation. Shifts between these vegetation types had been occurring in Euramerican portions of the equatorial region throughout the late middle and late Pennsylvanian, the drier vegetation reaching persistent dominance by Early Permian. The oscillatory transition between humid and seasonally dry vegetation appears to demonstrate a threshold-like behavior but probably not repeated transitions between alternative stable states. Rather, changes in dominance in lowland equatorial regions were driven by long-term, repetitive climatic oscillations, occurring with increasing intensity, within overall shift to seasonal dryness through time. In neither case study are there clear biotic or abiotic warning signs of looming changes in vegetational composition or geographic distribution, nor is it clear that there are specific, absolute values or rates of environmental change in temperature, rainfall distribution and amount, or atmospheric composition, approach to which might indicate proximity to a terrestrial biotic-change threshold.

The distribution and tectonic framework of Late Paleozoic volcanoes in the Junggar basin and its adjacent area, NW China

NASA Astrophysics Data System (ADS)

Mao, X.; Li, J. H.

2012-04-01

We analyse the distribution and characteristics of 145 late Paleozoic volcanoes in north Xinjiang, NW China, including 32 volcanoes on the edge of the Junggar basin. These volcanoes are clustered and can be divided into calderas, volcanic domes, and volcanic necks. There are also 85 volcanoes inside the Junggar basin, which are dominantly distributed in the Ke-Bai fractured zone of the northwestern margin of Junggar Basin, 4 depressions (Dongdaohaizi Depression, Dishuiquan Depression, Sannan Depression and Wucaiwan Depression) and 7 uplifts (Baijiahai uplift, Beisantai uplift, Dibei uplift, Dinan uplift, Sangequan uplift, Shixi uplift and Xiayan uplift). The volcanoes inside the basin are principally controlled by Hercynian Fault Systems, along NE and nearly EW trending faults and most developed in the interjunctions of the faults. The long modification by late-stage weathering and leaching made the volcanoes difficult to identify. Remaining volcanic landforms, changing trends of the volcanic lithofacies and the typical volcanic rock, such as the crypto- explosive breccia, are the typical marks of the late Paleozoic volcanoes in the field; and the concealed volcanic edifices are identified by the techniques of seismic identification, such as seismic slicing, analysis of the attribute and tectonic trend plane. The ages of the volcanic rocks are focused on from 340 Ma to 320Ma and from 300 Ma to 295 Ma, corresponding to the subducting periods of West Junggar and East Junggar. From early Carboniferous to late Carboniferous, the volcanic activities in Junggar Basin and its adjacent areas show a variation trend from undersea to continental, from deep water to shallow water and from continental margin to intracontinental.

Textural and Rb-Sr isotopic evidence for late Paleozoic mylonitization within the Honey Hill fault zone southeastern Connecticut

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

O'Hara, K.D.; Gromet, L.P.

A petrographic and Rb-Sr isotopic study of rocks within and near the Honey Hill fault zone places important constraints on its history of movement. Rb-Sr apparent ages for micas and plagioclase from these rocks have been reset and range from Permian to Triassic, considerably younger than the minimum stratigraphic age (Ordovician) of the rocks studied or of Acadian (Devonian) regional metamorphism. Permian Rb-Sr ages of dynamically recrystallized muscovite date the development of mylonite fabric. An older age is precluded by the excellent preservation of unrecovered quartz, which indicates that these rocks did not experience temperatures high enough to anneal quartzmore » or thermally reset Rb-Sr isotopic systems in muscovite since the time of mylonitization. Metamorphic mineral assemblages and mineral apparent ages in rocks north of the fault zone indicate recrystallization under similar upper greenschist-lower amphibolite grade conditions during Permian to Triassic time. Collectively these results indicate that the Honey Hill fault zone was active during the Late Paleozoic and that ductile deformation and metamorphism associated with the Alleghanian orogeny extend well into southern Connecticut. An Alleghanian age for mylonitization within the Honey Hill fault zone suggests it should be considered as a possible site for the major Late Paleozoic strike-slip displacements inferred from paleomagnetic studies for parts of coastal New England and maritime Canada.« less

Paleozoic Hydrocarbon-Seep Limestones

NASA Astrophysics Data System (ADS)

Peckmann, J.

2007-12-01

To date, five Paleozoic hydrocarbon-seep limestones have been recognized based on carbonate fabrics, associated fauna, and stable carbon isotopes. These are the Middle Devonian Hollard Mound from the Antiatlas of Morocco [1], Late Devonian limestone lenses with the dimerelloid brachiopod Dzieduszyckia from the Western Meseta of Morocco [2], Middle Mississippian limestones with the dimerelloid brachiopod Ibergirhynchia from the Harz Mountains of Germany [3], Early Pennsylvanian limestones from the Tantes Mound in the High Pyrenees of France [4], and Late Pennsylvanian limestone lenses from the Ganigobis Shale Member of southern Namibia [5]. Among these examples, the composition of seepage fluids varied substantially as inferred from delta C-13 values of early diagenetic carbonate phases. Delta C-13 values as low as -50 per mil from the Tantes Mound and -51 per mil from the Ganigobis limestones reveal seepage of biogenic methane, whereas values of -12 per mil from limestones with Dzieduszyckia associated with abundant pyrobitumen agree with oil seepage. Intermediate delta C-13 values of carbonate cements from the Hollard Mound and Ibergirhynchia deposits probably reflect seepage of thermogenic methane. It is presently very difficult to assess the faunal evolution at seeps in the Paleozoic based on the limited number of examples. Two of the known seeps were typified by extremely abundant rhynchonellide brachiopods of the superfamily Dimerelloidea. Bivalve mollusks and tubeworms were abundant at two of the known Paleozoic seep sites; one was dominated by bivalve mollusks (Hollard Mound, Middle Devonian), another was dominated by tubeworms (Ganigobis Shale Member, Late Pennsylvanian). The tubeworms from these two deposits are interpreted to represent vestimentiferan worms, based on studies of the taphonomy of modern vestimentiferans. However, this interpretation is in conflict with the estimated evolutionary age of vestimentiferans based on molecular clock methods

Origin of the Nubian and similar sandstones

USGS Publications Warehouse

McKee, E.D.

1963-01-01

The Nubian Sandstone and similar sandstone bodies exposed across much of northern Africa and adjoining parts of Asia are characteristically formed of clean sand that is conspicuously cross stratified throughout. Such sandstone, here called Nubian-type sandstone, ranges from Cambrian through Cretaceous in age and its genesis has been interpreted in many ways. Studies of its primary structures, and of the direction of sand transport, based on statistical measurements of foreset dip directions, have contributed new data on its genesis. By far the most common structure in Nubian-type sandstone is a medium-scale planar-type cross stratification in which sets of evenly dipping cross beds are bounded by essentially flat-lying top and bottom surfaces to form tabular bodies. Other less numerous but typical structures are large-scale, truncated-wedge cross strata, trough-type cross strata, intraformational recumbent folds, small-scale ripple laminae, and dipping sets of tabular-planar cross beds. An analysis of these structures suggests that in the typical Nubian Sandstone of Cretaceous age eolian deposits are not represented and normal marine types probably also are lacking; flood plain, pond or lagoon, and other continental and marginal environments are indicated. In the Carboniferous rocks of Sinai Peninsula some beach sandstone and possibly some eolian, in addition to the types described, form part of the sequence. Direction of sand transport, as determined from cross-bed dips, was northerly in the Cretaceous Nubian of Libya, Sudan, and Egypt; easterly in the Jurassic Adigrat of Ethiopia; westerly in the Carboniferous of Sinai; northwesterly in the early Paleozoic of Jordan. ?? 1963 Ferdinand Enke Verlag Stuttgart.

Provenance of sandstones in the Golconda terrane, north central Nevada

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

Jones, E.A.

1991-02-01

The upper Paleozoic Golconda terrane of north-central Nevada is a composite of several structurally bounded subterranes made of clastic, volcanic, and carbonate rocks. The clastic rocks provide important clues for the interpretation of the provenance and paleogeographic settings of the different lithologic assemblages found in these subterranes. Two petrographically distinct sandstones are identified in the Golconda terrane in the Osgood Mountains and the Hot springs Range of north-central Nevada. The sandstone of the Mississippian Farrel Canyon Formation, part of the Dry Hills subterrane, is characterized by quartzose and sedimentary and lithic-rich clasts with a small feldspar component. in contrast, themore » sandstone of the Permian Poverty Peak (II) subterrane is a silty quartzarenite with no lithic component, and a very limited feldspar component. The sandstone of the Farrel Canyon Formation is similar to nonvolcanic sandstones reported from elsewhere in the Golconda terrane. Modal data reflect a provenance of a recycled orogen and permit the interpretation that it could have been derived from the antler orogen as has been proposed for other sandstones of the golconda terrane. The sandstone of the Poverty Peak (II) subterrane is more mature than any of the other sandstones in either the Golconda terrane, the Antler overlap sequence, or the Antler foreland basin sequence. Modal data put the Poverty Peak (II) sandstone in the continental block provenance category. The distinct extrabasinal provenances represented in these different sandstones support the idea that the Golconda basin was made up of complex paleogeographic settings, which included multiple sources of extrabasinal sediment.« less

Paleozoic tectonics of the Ouachita Orogen through Nd isotopes

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

Gleason, J.D.; Patchett, P.J.; Dickinson, W.R.

1992-01-01

A combined isotopic and trace-element study of the Late Paleozoic Ouachita Orogenic belt has the following goals: (1) define changing provenance of Ouachita sedimentary systems throughout the Paleozoic; (2) constrain sources feeding into the Ouachita flysch trough during the Late Paleozoic; (3) isolate the geochemical signature of proposed colliding terranes to the south; (4) build a data base to compare with possible Ouachita System equivalents in Mexico. The ultimate aim is to constrain the tectonic setting of the southern margin of North America during the Paleozoic, with particular emphasis on collisional events leading to the final suturing of Pangea. Ndmore » isotopic data identify 3 distinct groups: (1) Ordovician passive margin sequence; (2) Carboniferous proto-flysch (Stanley Fm.), main flysch (Jackfork and Atoka Fms.) and molasse (foreland Atoka Fm.); (3) Mississippian ash-flow tuffs. The authors interpret the Ordovician signature to be essentially all craton-derived, whereas the Carboniferous signature reflects mixed sources from the craton plus orogenic sources to the east and possibly the south, including the evolving Appalachian Orogen. The proposed southern source is revealed by the tuffs to be too old and evolved to be a juvenile island arc terrane. They interpret the tuffs to have been erupted in a continental margin arc-type setting. Surprisingly, the foreland molasse sequence is indistinguishable from the main trough flysch sequence, suggesting the Ouachita trough and the craton were both inundated with sediment of a single homogenized isotopic signature during the Late Carboniferous. The possibility that Carboniferous-type sedimentary dispersal patterns began as early as the Silurian has important implications for the tectonics and paleogeography of the evolving Appalachian-Ouachita Orogenic System.« less

Depositional environments and tectonic significance of the Wajid Sandstone of southern Saudi Arabia

NASA Astrophysics Data System (ADS)

Dabbagh, Mohamed E.; Rogers, John J. W.

The Wajid Sandstone, of probable Early Paleozoic age, rests disconformably on crystalline rocks of the southern part of the Arabian shield. Scattered outcrops extend over an area about 450 km north-south and 300 km east-west. The southern part of the formation, near the Yemen border, consists of fluvial sandstones and very minor siltstones and silty shales. The fluvial origin is demonstrated by the presence of fining-upward cycles, channels, trough cross bedding, and absence of all organic traces. The northern part of the outcrop area consists of internally homogeneous, tabular cross-bedded, horizontally bedded sandstones apparently formed in a shallow marine environment. These marine rocks contain trace fossils broadly similar to Skolithos. Abundant cross bedding in both facies of the Wajid indicates a northward transport direction, toward what is now the center of the Arabian shield. The southern part of the Arabian shield, which was cratonized about 500 to 600 Ma ago (Pan-African age), was apparently still a depositional area receiving sediments from a southern source in Early Paleozoic time. Other, older, shields also show a tendency to be areas of deposition shortly after their apparent age of stabilization, becoming sources of clastic sediments only after several hundreds of millions of years. The conversion from basin to uplifted source may indicate a prolonged process of shield maturation after initial stabilization.

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

NASA Astrophysics Data System (ADS)

Abbasi, Iftikhar Ahmed

2017-04-01

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

Petrology and stratigraphy of Paleogene nonmarine sandstones, Cascade Range, Washington

USGS Publications Warehouse

Frizzell, Virgil A.

1979-01-01

The Cascade Range of Washington north of 47? latitude is composed of probable Paleozoic and Mesozoic metamorphic rocks and Mesozoic and Tertiary plutonic rocks. Several Paleogene nonmarine arkosic sandstone units fringe and in part occur within the complex crystalline core. The early to middle Eocene Chuckanut Formation is present on the west side of the crystalline core in the western foothills of the Cascades. The early to middle Eocene Swauk Formation partially encircles the Mt. Stuart massif of the central Cascades. In the western foothills of the Cascades, between the main body of Chuckanut Formation near Bellingham and the main outcrop area of the Swauk Formation south of Mt. Stuart, many smaller bodies of arkosic sandstone have variously been referred to either the Swauk or Chuckanut Formations. The early Eocene Manastash Formation occurs locally in an area south of the Yakima River. The middle to late Eocene Chumstick Formation is mostly confined to the Chiwaukum graben within the crystalline core and is separated from the Swauk Formation on the southwest by the Leavenworth Fault. The Oligocene Wenatchee Formation unconformably over lies the Chumstick Formation near Wenatchee. The middle to late Eocene Roslyn Formation crops out north of the Yakima River and is underlain by the Teanaway Basalt which separates the Roslyn from the older Swauk Formation. The middle Eocene to early Oligocene Naches Formation forms a north-trending body that crosses the Yakima River and is in fault contact with both the Swauk and Manastash Formations. The middle to late Eocene Puget Group underlies the Quaternary deposits of the Puget Lowland southeast of Seattle on the western flank of the Cascades. The various formations are all composed predominantly of fine- to medium-grained sandstones with lesser amounts of interbedded shale, conglomerate and coal. Compositionally, the units are predominantly either feldspathic or litho-feldspathic subquartzose sandstones. Volcanic rocks

Paleozoic tectonics in the eastern part of Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Liu, Yongjiang; Li, Weimin; Feng, Zhiqiang; Neubauer, Franz

2017-04-01

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogen in the world, which is responsible for considerable Phanerozoic juvenile crustal growth. The NE China and its adjacent areas compose the eastern segment of the CAOB, which is a key area for providing important evidence of the CAOB evolution and understanding the NE Asian tectonics. The eastern segment of the CAOB is composed tectonically of four micro-blocks and four sutures, i.e. Erguna block (EB), Xing'an block (XB), Songliao-Xilinhot block (SXB), Jiamusi block (JB), Xinlin-Xiguitu suture (XXS), Heihe-Hegenshan suture (HHS), Mudanjiang-Yilan suture (MYS) and Solonker-Xar Moron-Changchun-Yanji suture (SXCYS). The EB and XB were amalgamated by westward subduction, oceanic island accretions and final collision in ca. 500 Ma. The XB and SXB were amalgamated by subduction-related Early Paleozoic marginal arc, Late Paleozoic marginal arc and final collision in the late Early Carboniferous to early Late Carboniferous. The JB probably had been attached to the SXB in the Early Paleozoic, but broken apart from the SXB in the Triassic and collided back in the Jurassic. The closure of Paleo-Asian Ocean had experienced a long continue/episodic subduction-accretion processes on margins of the NCC to the south and the SXB to the north from the Early to Late Paleozoic. The final closure happened along the SXCYS, from west Solonker, Sonid Youqi, Kedanshan (Keshenketengqi), Xar Moron River through Songliao Basin via Kailu, Tongliao, Horqin Zuoyizhongqi, Changchun, to the east Panshi, Huadian, Dunhua, Yanji, with a scissors style closure in time from the Late Permian-Early Triassic in the west to the Late Permian-Middle Triassic in the east. The amalgamated blocks should compose a united micro-continent, named as Jiamusi-Mongolia Block (JMB) after Early Carboniferous, which bounded by Mongo-Okhotsk suture to the northwest, Solonker-Xar Moron-Changchun suture to the south and the eastern margin of JB to the

The Cottage Grove fault system (Illinois Basin): Late Paleozoic transpression along a Precambrian crustal boundary

USGS Publications Warehouse

Duchek, A.B.; McBride, J.H.; Nelson, W.J.; Leetaru, H.E.

2004-01-01

The Cottage Grove fault system in southern Illinois has long been interpreted as an intracratonic dextral strike-slip fault system. We investigated its structural geometry and kinematics in detail using (1) outcrop data, (2) extensive exposures in underground coal mines, (3) abundant borehole data, and (4) a network of industry seismic reflection profiles, including data reprocessed by us. Structural contour mapping delineates distinct monoclines, broad anticlines, and synclines that express Paleozoic-age deformation associated with strike slip along the fault system. As shown on seismic reflection profiles, prominent near-vertical faults that cut the entire Paleozoic section and basement-cover contact branch upward into outward-splaying, high-angle reverse faults. The master fault, sinuous along strike, is characterized along its length by an elongate anticline, ???3 km wide, that parallels the southern side of the master fault. These features signify that the overall kinematic regime was transpressional. Due to the absence of suitable piercing points, the amount of slip cannot be measured, but is constrained at less than 300 m near the ground surface. The Cottage Grove fault system apparently follows a Precambrian terrane boundary, as suggested by magnetic intensity data, the distribution of ultramafic igneous intrusions, and patterns of earthquake activity. The fault system was primarily active during the Alleghanian orogeny of Late Pennsylvanian and Early Permian time, when ultramatic igneous magma intruded along en echelon tensional fractures. ?? 2004 Geological Society of America.

Burning experiments and late Paleozoic high O2 levels

NASA Astrophysics Data System (ADS)

Wildman, R.; Essenhigh, R.; Berner, R.; Hickey, L.; Wildman, C.

2003-04-01

The Paleozoic rise of land plants brought about increased burial of organic matter and a resulting increase in atmospheric oxygen concentrations. Levels as high as 30-35% O2 may have been reached during the Permo-Carboniferous (Berner and Canfield, 1989; Berner, 2001). However, burning experiments based solely on paper (Watson, 1978) have challenged these results, the claim being that if the oxygen made up more than 25% of the atmosphere, the frequency and intensity of forest fires would increase sufficiently to prevent the continued existence of plant life. Thus, since plants have persisted, it is possible that fires served as a negative feedback against excessive oxygen levels. An initial study of Paleozoic wildfire behavior via thermogravimetric analysis (TGA) was conducted under ambient and enriched oxygen conditions to simulate present and ancient atmospheres. The tests focused on natural fuels, specifically tree leaves and wood, tree fern fibers, and sphagnum peat-moss, simulating Permo-Carboniferous upland and swampland ecosystems, respectively. Three conclusions are: (1) enriched oxygen increases the rate of mass loss during burning; (2) fuel chemistry (cellulose vs. lignin) influences burning patterns; and (3) in geometrically heterogeneous fuels, geometry affects burning rate significantly. Both geometrically and chemically, paper resists fire poorly; thus, we found that it loses its mass at lower temperatures than forest materials and is therefore a poor proxy for Paleozoic ecosystems. Further study of Paleozoic wildfire spread behavior is currently being conducted. Fires are lit using pine dowels, which allow for reproducible fuel density. Steady-state, one-dimensional flame-spread is measured with thermocouples anchored two inches above the fuel bed. Both oxygen concentration of the air supply to the fire and moisture content of the fuels are varied, as we suspect that these are two main controls of wildfire spread. Burning fuels of varying moisture

Artesian pressures and water quality in Paleozoic aquifers in the Ten Sleep area of the Bighorn Basin, north-central Wyoming

USGS Publications Warehouse

Cooley, Maurice E.

1986-01-01

The major Paleozoic artesian aquifers, the aquifers most favorable for continued development, in the Ten Sleep area of the Bighorn Basin of Wyoming are the Tensleep Sandstone, the Madison Limestone and Bighorn Dolomite (Madison-Bighorn aquifer), and the Flathead Sandstone. The minor aquifers include the Goose Egg and Park City Formations (considered in the Ten Sleep area to be the lateral equivalent of the Phosphoria Formation) and the Amsden Formation. Most wells completed in the major and minor aquifers flow at the land surface. Wellhead pressures generally are less than 50 pounds per square inch for the Tensleep Sandstone, 150-250 pounds per square inch for the Madison-Bighorn aquifer, and more than 400 pounds per square inch for the Flathead Sandstone. Flowing wells completed in the Madison-Bighorn aquifer and the Flathead Sandstone yield more than 1,000 gallons per minute. The initial test of one well completed in the Madison-Bighorn aquifer indicated a flow rate of 14,000 gallons per minute. Transmissivities range from 500 to 1,900 feet squared per day for the Madison-Bighorn aquifer and from about 90 to 325 feet squared per day for the Tensleep and Flathead Sandstones. Significant secondary permeability from fracturing in the Paleozoic aquifers allows local upward interformational movement of water, and this affects the altitude of the potentiometric surfaces of the Tensleep Sandstone and the Madison-Bighorn aquifer. Water moves upward from the Tensleep and other formations, through the Goose Egg Formation, to discharge at the land surface as springs. Much of the spring flow is diverted for irrigation or is used for rearing fish. Decreases from original well pressures were not apparent in wells completed in the Tensleep Sandstone or in the Madison-Bighorn aquifer in the study area except for a few wells in or near the town of Ten Sleep. Most wells completed in the Flathead Sandstone, which also are open to the Madison-Bighorn aquifer, show a decrease of

Paleozoic-involving thrust array in the central Sierras Interiores (South Pyrenean Zone, Central Pyrenees): regional implications

NASA Astrophysics Data System (ADS)

Rodriguez, L.; Cuevas, J.; Tubía, J. M.

2012-04-01

This work deals with the structural evolution of the Sierras Interiores between the Tena and Aragon valleys. The Sierras Interiores is a WNW-trending mountain range that bounds the South Pyrenean Zone to the north and that is characterized by a thrust-fold system with a strong lithological control that places preferably decollements in Triassic evaporites. In the studied area of the Sierras Interiores Cenomanian limestones cover discordantly the Paleozoic rocks of the Axial Zone because there is a stratigraphic lacuna developed from Triassic to Late Cretaceous times. A simple lithostratigraphy of the study area is made up of Late Cenomanian to Early Campanian limestones with grey colour and massive aspect in landscape (170 m, Lower calcareous section), Campanian to Maastrichtian brown coloured sandstones (400-600 m, Marboré sandstones) and, finally, Paleocene light-coloured massive limestones (130-230 m), that often generate the higher topographic levels of the Sierras Interiores due to their greater resistance to erosion. Above the sedimentary sequence of the Sierras Interiores, the Jaca Basin flysch succession crops out discordantly. Based on a detailed mapping of the studied area of the Sierras Interiores, together with well and structural data of the Jaca Basin (Lanaja, 1987; Rodríguez and Cuevas, 2008) we have constructed a 12 km long NS cross section, approximately parallel to the movement direction deduced for this region (Rodríguez et al., 2011). The main structure is a thrust array made up of at least four Paleozoic-involving thrusts (the deeper thrust system) of similar thickness in a probably piggyback sequence, some of which are blind thrusts that generate fold-propagation-folds in upper levels. The higher thrust of the thrust array crops out duplicating the lower calcareous section all over the Sierras Interiores. The emplacement of the deeper thrust system generated the tightness of previous structures: south directed piggyback duplexes (the upper

Paleozoic intrusive rocks from the Dunhuang tectonic belt, NW China: Constraints on the tectonic evolution of the southernmost Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Zhao, Yan; Sun, Yong; Diwu, Chunrong; Zhu, Tao; Ao, Wenhao; Zhang, Hong; Yan, Jianghao

2017-05-01

The Dunhuang tectonic belt (DTB) is of great importance for understanding the tectonic evolution of the southernmost Central Asian Orogenic Belt (CAOB). In this study, the temporal-spatial distribution, petrogenesis and tectonic setting of the Paleozoic representative intrusive rocks from the DTB were systematically investigated to discuss crustal evolution history and tectonic regime of the DTB during Paleozoic. Our results reveal that the Paleozoic magmatism within the DTB can be broadly divided into two distinct episodes of early Paleozoic and late Paleozoic. The early Paleozoic intrusive rocks, represented by a suite metaluminous-slight peraluminous and medium- to high-K calc-alkaline I-type granitoids crystallized at Silurian (ca. 430-410 Ma), are predominantly distributed along the northern part of the DTB. They were probably produced with mineral assemblage of eclogite or garnet + amphibole + rutile in the residue, and were derived from magma mixing source of depleted mantle materials with various proportions of Archean-Mesoproterozoic continental crust. The late Paleozoic intrusive rocks can be further subdivided into two stages of late Devonian stage (ca. 370-360 Ma) and middle Carboniferous stage (ca. 335-315 Ma). The former stage is predominated by metaluminous to slight peraluminous and low-K tholeiite to high-K calc-alkaline I-type granitic rocks distributed in the central part of the DTB. They were also generated with mineral assemblage of amphibolite- to eclogite-facies in the residue, and originated from magma source of depleted mantle materials mixed with different degrees of old continental crust. The later stage is represented by adakite and alkali-rich granite exposed in the southern part of the DTB. The alkali-rich granites studied in this paper were possibly produced with mineral assemblage of granulite-facies in the residue and were generated by partial melting of thickened lower continental crust. Zircon Hf isotopes and field distribution of

Late paleozoic base and precious metal deposits, East Tianshan, Xinjiang, China: Characteristics and geodynamic setting

USGS Publications Warehouse

Mao, J.; Goldfarb, R.J.; Wang, Y.; Hart, C.J.; Wang, Z.; Yang, J.

2005-01-01

The East Tianshan is a remote Gobi area located in eastern Xinjiang, northwestern China. In the past several years, a number of gold, porphyry copper, and Fe(-Cu) and Cu-Ag-Pb-Zn skarn deposits have been discovered there and are attracting exploration interest. The East Tianshan is located between the Junggar block to the north and early Paleozoic terranes of the Middle Tianshan to the south. It is part of a Hercynian orogen with three distinct E-W-trending tectonic belts: the Devonian-Early Carboniferous Tousuquan-Dananhu island arc on the north and the Carboniferous Aqishan - Yamansu rift basin to the south, which are separated by rocks of the Kanggurtag shear zone. The porphyry deposits, dated at 322 Ma, are related to the late evolutionary stages of a subduction-related oceanic or continental margin arc. In contrast, the skarn, gold, and magmatic Ni-Cu deposits are associated with post-collisional tectonics at ca. 290-270 Ma. These Late Carboniferous - Early Permian deposits are associated with large-scale emplacement and eruption of magmas possibly caused by lithosphere delamination and rifting within the East Tianshan.

A-type granitoid in Hasansalaran complex, northwestern Iran: Evidence for extensional tectonic regime in northern Gondwana in the Late Paleozoic

NASA Astrophysics Data System (ADS)

Azizi, Hossein; Kazemi, Tahmineh; Asahara, Yoshihiro

2017-07-01

The Hasansalaran plutonic complex is one of the main intrusive bodies with a wide range of granite, monzonite, diorite and syenite that crop out in northwest Iran. This body includes Paleozoic granitoids that are surrounded and cut by Cretaceous granitoids. Zircon U-Pb age dating shows that the crystallization of this body occurred at 360 Ma ago in the Early Carboniferous. Whole rock compositions of the investigated intrusive body, show high contents of Ga (11.1-76.3 ppm), Zr (73.5-1280 ppm), Zn (43.7-358 ppm), Y(17.9-177 ppm), enrichment of rare earth elements (REEs) together with high Ga/Al ratios and a strong Eu negative anomaly, fairly consistent with typical A-type signature. The low εNd(t = 360 Ma) value (< + 3) and high variation of 87Sr/86Sr(initial) ratios are evidence of the role of the continental component for the evolution of A-type granitoids in the Hasansalaran area. Because of the high contents of Ta, Yb, Nb and Y, all samples are plotted in the within-plate tectonic regime without interfering oceanic released fluids in the subduction zone. These high Nb content rocks (37.2-342 ppm without one sample) are classified as A1-type granitoids. Based on the distribution of A1- and A2-type granitoids in the Late Paleozoic in northwest Iran, the existence of some gabbroic rocks with tholeiitic to alkali composition and a long gap for magmatic activities in the area from 550 to 360 Ma (approximately 180 my.a.) between the Zagros and Tabriz faults, we suggest a new thematic model for evolution of northwest Iran in the Late Paleozoic. Based on our model, the upwelling of a mantle plume, probably due to the proto-Tethys oceanic rollback activity beneath northern Gondwana, had a crucial role in the uplifting of the continental crust and resulted in the crystallization of A-type granitoids with some gabbroic rocks in northwest Iran.

High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: The role of special conditions of cratonic interiors in development of stratal architecture

USGS Publications Warehouse

Runkel, Anthony C.; Miller, J.F.; McKay, R.M.; Palmer, A.R.; Taylor, John F.

2007-01-01

continuum of variable stratigraphic packages reflecting variable controls such as subsidence and shelf physiography. Special conditions of exceptionally slow subsidence rate, shallow bathymetry, and nearly flat regional shelf gradient are manifest mostly by the presence of individual systems tracts of relatively long duration that extend for much greater distances across depositional strike than those that characterize successions deposited in more dynamic tectonic and physiographic settings. These results suggest that if other cratonic interior successions are as anomalous as reported, a low sediment supply may have played a primary role in development of their apparently condensed stratal architecture. The results also lead us to suggest that a nonvegetated lower Paleozoic landscape played a relatively insignificant role in the development of what are commonly perceived to be enigmatic stratigraphic features of sheet sandstones, particularly their widespread yet thin geometry, and a scarcity of shale and siltstone. ?? 2007 Geological Society of America.

Geochemical evidence for Paleozoic crustal growth and tectonic conversion in the Northern Beishan Orogenic Belt, southern Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Yuan, Yu; Zong, Keqing; He, Zhenyu; Klemd, Reiner; Jiang, Hongying; Zhang, Wen; Liu, Yongsheng; Hu, Zhaochu; Zhang, Zeming

2018-03-01

The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446-430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466-428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon εHf(t) values between - 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145-0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330-281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon εHf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037-0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of

Tectonic Recycling in the Paleozoic Ouachita Assemblage from U-Pb Detrital Zircon Studies

NASA Astrophysics Data System (ADS)

Gleason, J. D.; Gehrels, G. E.; Finney, S. C.

2001-05-01

The Paleozoic Ouachita deep-marine clastic sedimentary assemblage records a complex provenance over the course of its 200 m.y. history, with evidence for mixed sources and multiple dispersal paths. Combined neodymium and U-Pb detrital zircon work has established that most of the assemblage in Arkansas and Oklahoma is derived from Laurentian sources, meaning that regardless of the multiple pathways by which sediment was delivered to Ouachita seafloor, the material had its ultimate origin on the North American continent. More detailed work is in progress to elucidate specific dispersal paths, in particular for the middle to late Ordovician when a major change in provenance is recorded, and during the Carboniferous when voluminous turbidites entered the basin. We sampled three formations for U-Pb detrital zircon studies: the lower Middle Ordovician Blakely Sandstone, the Upper Ordovician/Lower Silurian Blaylock Sandstone, and the Pennsylvanian Jackfork Group. Individual zircon ages from these units document a major change in provenance between deposition of the Blakely Sandstone and Blaylock Sandstone, which is also reflected in the neodymium isotopic signature. Both units have a large population of Grenvillian-age zircons (1.0-1.2 Ga), and a less abundant population of 1.3-1.4 Ga zircons likely derived from sources in the mid-continent region. The Blakely Sandstone also contains abundant Archean zircons (2.5-2.7 Ga, likely derived from the Superior Province), and one grain apparently derived from the Penokean orogen (1.9 Ga). Zircon morphology (highly rounded, spherical), combined with the pure quartz sandstone lithology of the Blakely Sandstone, indicates very mature sedimentary sources. We conclude that zircons from this source were recycled ultimately from source terranes in the North American craton. This is reinforced by neodymium isotopes (eNd = -15), paleocurrents (from the north) and olistoliths (1.3 Ga granites), the latter indicating that Blakely turbidites

"Sydney sandstone": Heritage Stone from Australia

NASA Astrophysics Data System (ADS)

Cooper, Barry; Kramar, Sabina

2014-05-01

Sydney is Australia's oldest city being founded in 1788. The city was fortunate to be established on an extensive and a relatively undeformed layer of lithified quartz sandstone of Triassic age that has proved to be an ideal building stone. The stone has been long identified by geologists as the Hawkesbury Sandstone. On the other hand the term "Sydney sandstone" has also been widely used over a long period, even to the extent of being utilised as the title of published books, so its formal designation as a heritage stone will immediately formalise this term. The oldest international usage is believed to be its use in the construction of the Stone Store at Kerikeri, New Zealand (1832-1836). In the late 19th century, public buildings such as hospitals, court houses as well as the prominent Sydney Town Hall, Sydney General Post Office, Art Gallery of New South Wales, State Library of New South Wales as well as numerous schools, churches, office building buildings, University, hotels, houses, retaining walls were all constructed using Sydney sandstone. Innumerable sculptures utilising the gold-coloured stone also embellished the city ranging from decorative friezes and capitals on building to significant monuments. Also in the late 19th and early 20th century, Sydney sandstone was used for major construction in most other major Australian cities especially Melbourne, Adelaide and Brisbane to the extent that complaints were expressed that suitable local stone materials were being neglected. Quarrying of Sydney sandstone continues today. In 2000 it was recorded noted that there were 33 significant operating Sydney sandstone quarries including aggregate and dimension stone operations. In addition sandstone continues to be sourced today from construction sites across the city area. Today major dimension stone producers (eg Gosford Quarries) sell Sydney sandstone not only into the Sydney market but also on national and international markets as cladding and paving products

Paleomagnetism and alteration of lower Paleozoic rocks and Precambrian basement in the SHADS No. 4 drill core, Oklahoma

NASA Astrophysics Data System (ADS)

Evans, S. C.; Hamilton, M.; Hardwick, J.; Terrell, C.; Elmore, R. D.

2017-12-01

The chacterization of the lower Paleozoic sedimentary rock and the underlying Precambrian basement in northern Oklahoma is currently the subject of research to better understand induced seismicity in Oklahoma. We are investigating approximately 140 meters of igneous basement and over 300 meters of Ordovician Arbuckle Group carbonates and underlying sandstone in the Amoco SHADS No. 4 drill core from Rogers Co., Oklahoma, to better understand the nature, origin, and timing of fluid alteration and the relationship between fluid flow in the Arbuckle Group and the basement. Preliminary attempts to orient the core using the viscous remanent magnetization (VRM) method were unsuccessful, probably due to a steep drilling-induced component. The dolomitized Arbuckle Group contains a characteristic remanent magnetization (ChRM) with shallow inclinations (-5°) and variable declinations that, based on unblocking temperatures, is interpreted to reside in magnetite. This ChRM is interpreted as a chemical remanent magnetization (CRM) acquired in the Permian based on the shallow inclinations. The CRM could be related to hydrothermal fluids which migrated into the rocks in the late Paleozoic, as other studies in northern Oklahoma have reported. The Arbuckle Group dolomites are porous and extensively altered and consist of several generations of dolomite, including baroque dolomite. The basement rock is andesitic to trachytic ignimbrite that exhibits extensive alteration. There are many near-vertical fractures mineralized with epidote that are cross cut by calcite-filled fractures. Anisotropy of magnetic susceptibility (AMS) measurements indicate an oblate fabric in the top of the basement and the overlying sandstones. At greater depths, the AMS is variable and may include both alteration and primary fabrics. Demagnetization of the basement rocks is in the initial stages. We are currently investigating if and how far the alteration in the Arbuckle Group extended into the basement

Braided fluvial sedimentation in the lower paleozoic cape basin, South Africa

NASA Astrophysics Data System (ADS)

Vos, Richard G.; Tankard, Anthony J.

1981-07-01

Lower Paleozoic braided stream deposits from the Piekenier Formation in the Cape Province, South Africa, provide information on lateral and vertical facies variability in an alluvial plain complex influenced by a moderate to high runoff. Four braided stream facies are recognized on the basis of distinct lithologies and assemblages of sedimentary structures. A lower facies, dominated by upward-fining conglomerate to sandstone and mudstone channel fill sequences, is interpreted as a middle to lower alluvial plain deposit with significant suspended load sedimentation in areas of moderate to low gradients. These deposits are succeeded by longitudinal conglomerate bars which are attributed to middle to upper alluvial plain sedimentation with steeper gradients. This facies is in turn overlain by braid bar complexes of large-scale transverse to linguoid dunes consisting of coarse-grained pebbly sandstones with conglomerate lenses. These bar complexes are compared with environments of the Recent Platte River. They represent a middle to lower alluvial plain facies with moderate gradients and no significant suspended load sedimentation or vegetation to stabilize channels. These bar complexes interfinger basinward with plane bedded medium to coarse-grained sandstones interpreted as sheet flood deposits over the distal portions of an alluvial plain with low gradients and lacking fine-grained detritus or vegetation.

Origin of a classic cratonic sheet sandstone: Stratigraphy across the Sauk II-Sauk III boundary in the Upper Mississippi Valley

USGS Publications Warehouse

Runkel, Anthony C.; McKay, R.M.; Palmer, A.R.

1998-01-01

The origin of cratonic sheet sandstones of Proterozoic and early Paleozoic age has been a long-standing problem for sedimentologists. Lower Paleozoic strata in the Upper Mississippi Valley are best known for several such sandstone bodies, the regional depositional histories of which are poorly understood. We have combined outcrop and subsurface data from six states to place the Upper Cambrian Wonewoc (Ironton and Galesville) Sandstone in a well-constrained stratigraphic framework across thousands of square kilometers. This framework makes it possible for the first time to construct a regional-scale depositional model that explains the origin of this and other cratonic sheet sandstones. The Wonewoc Sandstone, although mapped as a single contiguous sheet, is a stratigraphically complex unit that was deposited during three distinct conditions of relative sea level that span parts of four trilobite zones. During a relative highstand of sea level in Crepicephalus Zone time, quartzose sandstone lithofacies aggraded more or less vertically in nearshore-marine and terrestrial environments across much of the present-day out-crop belt around the Wisconsin arch. At the same time, finer grained, feldspathic sandstone, siltstone, and shale aggraded in deeper water immediately seaward of the quartzose sand, and shale and carbonate sediment accumulated in the most distal areas. During Aphelaspis and Dunderbergia Zones time a relative fall in sea level led to the dispersal of quartzose sand into a basinward-tapering, sheet-like body across much of the Upper Mississippi Valley. During early Elvinia Zone time a major transgression led to deposition of a second sheet sandstone that is generally similar to the underlying regressive sheet. The results of this investigation also demonstrate how subtle sequence-bounding unconformities may be recognized in mature, cratonic siliciclastics. We place the Sauk II-Sauk III subsequence boundary at the base of the coarsest bed in the Wonewoc

Timing, petrogenesis and tectonic setting of the Late Paleozoic gabbro-granodiorite-granite intrusions in the Shalazhashan of northern Alxa: Constraints on the southernmost boundary of the Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Shi, Xingjun; Wang, Tao; Zhang, Lei; Castro, Antonio; Xiao, XuChang; Tong, Ying; Zhang, Jianjun; Guo, Lei; Yang, Qidi

2014-11-01

The Late Paleozoic tectonic setting and location of the southernmost boundary of the Central Asian Orogenic Belt (CAOB) with respect to the Alxa Block or Alxa-North China Craton (ANCC) are debated. This paper presents new geochronological, petrological, geochemical and zircon Hf isotopic data of the Late Paleozoic intrusions from the Shalazhashan in northern Alxa and discusses the tectonic setting and boundary between the CAOB and ANCC. Using zircon U-Pb dating, intrusions can be broadly grouped as Late Carboniferous granodiorites (~ 301 Ma), Middle Permian gabbros (~ 264 Ma) and granites (~ 266 Ma) and Late Permian granodiorites, monzogranites and quartz monzodiorites (254-250 Ma). The Late Carboniferous granodiorites are slightly peraluminous and calcic. The remarkably high zircon Hf isotopes (εHf(t) = + 6-+ 10) and characteristics of high silica adakites suggest that these granodiorites were mainly derived from "hot" basaltic slab-melts of the subducted oceanic crust. The Middle Permian gabbros exhibited typical cumulate textures and were derived from the partial melting of depleted mantle. The Middle Permian granites are slightly peraluminous with high-K calc-alkaline and low εHf(t) values from - 0.9 to + 2.9. These granites were most likely derived from juvenile materials mixed with old crustal materials. The Late Permian granodiorites, monzogranites and quartz monzodiorites are characterized as metaluminous to slightly peraluminous, with variable Peacock alkali-lime index values from calc-alkalic to alkali-calcic. These rocks were mainly derived from juvenile crustal materials, as evidenced by their high εHf(t) values (+ 3.3 to + 8.9). The juvenile sources of the above intrusions in the Shalazhashan are similar to those of the granitoids from the CAOB but distinct from the granitoids within the Alxa Block. These findings suggest that the Shalazhashan Zone belongs to the CAOB rather than the Alxa Block and that its boundary with the Alxa block can be

Correlation of Late Precambrian and Paleozoic events in the East European platform and the adjacent paleooceanic domains

NASA Astrophysics Data System (ADS)

Kheraskova, T. N.; Volozh, Yu. A.; Antipov, M. P.; Bykadorov, V. A.; Sapozhnikov, R. B.

2015-01-01

The correlation of geological events and structure-forming processes occurring contemporaneously in the inner parts of cratons and the adjacent paleooceanic basins is discussed in order to understand the effects of these processes on sedimentation and structural rearrangements. For this purpose, a series of paleodynamic reconstructions of the Riphean, Vendian, and Paleozoic epicontinental basins of the East European Platform and zones of their transition to marginal basins of the same age once situated in the Ural, Timan, Caucasus, Scandinavian fold regions and in the Scythian-Turan Plate have been performed on the basis of the available original and published data combined with interpretation of seismic profiles. As a result, a set of structural-facies maps of this territory have been compiled for several time intervals from the Late Riphean to Early Permian.

Reservoir assessment of the Nubian sandstone reservoir in South Central Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

El-Gendy, Nader; Barakat, Moataz; Abdallah, Hamed

2017-05-01

The Gulf of Suez is considered as one of the most important petroleum provinces in Egypt and contains the Saqqara and Edfu oil fields located in the South Central portion of the Gulf of Suez. The Nubian sandstone reservoir in the Gulf of Suez basin is well known for its great capability to store and produce large volumes of hydrocarbons. The Nubian sandstone overlies basement rocks throughout most of the Gulf of Suez region. It consists of a sequence of sandstones and shales of Paleozoic to Cretaceous age. The Nubian sandstone intersected in most wells has excellent reservoir characteristics. Its porosity is controlled by sedimentation style and diagenesis. The cementation materials are mainly kaolinite and quartz overgrowths. The permeability of the Nubian sandstone is mainly controlled by grain size, sorting, porosity and clay content especially kaolinite and decreases with increase of kaolinite. The permeability of the Nubian Sandstone is evaluated using the Nuclear Magnetic Resonance (NMR technology) and formation pressure data in addition to the conventional logs and the results were calibrated using core data. In this work, the Nubian sandstone was investigated and evaluated using complete suites of conventional and advanced logging techniques to understand its reservoir characteristics which have impact on economics of oil recovery. The Nubian reservoir has a complicated wettability nature which affects the petrophysical evaluation and reservoir productivity. So, understanding the reservoir wettability is very important for managing well performance, productivity and oil recovery.

Structural evolution of the Irtysh Shear Zone: implication for the Late Paleozoic amalgamation of multiple arc systems in Central Asia

NASA Astrophysics Data System (ADS)

Li, Pengfei; Sun, Min; Rosenbaum, Gideon

2015-04-01

The NW-SE Irtysh Shear Zone represents a major tectonic boundary in the Central Asian Orogenic Belt, recording the amalgamation history between the peri-Siberian orogenic system and the Kazakhstan orogenic system. The structural evolution and geodynamics of this shear zone is still poorly documented. Here we present new structural data complemented by chronological data in an attempt to unravel the geodynamic significance of the Irtysh Shear Zone in the context of accretion history of the Central Asian Orogenic Belt. Our results show three episodes of deformation for the shear zone. D1 foliation is locally recognized in low strain area and recorded by garnet inclusions, whereas D2 is represented by a sub-horizontal fabric and related NW-SE lineation. D3 is characterized by a transpersonal deformation event, to form a series of NW-SE mylonitic belts with sinistral kinematics, and to overprint D2 fabric forming regional-scale NW-SE upright folds. A paragneiss sample from the shear zone yielded the youngest detrital zircon peaks in the late Carboniferous, placing a maximum age constraint on the deformation, which overlaps in time with the late Paleozoic collision between the Chinese Altai and the intraoceanic arc system of the East Junggar and West Junggar. We interpret three episodes of deformation to represent orogenic thickening (D1), collapse (D2) and thickening (D3) in response to this collisional event. Sinistral shearing (D3) together with the coeval dextral shearing in the Tianshan accommodate eastward extrusion of the Kazakhstan orogenic system during the late Paleozoic amalgamation of the Central Asian Orogenic Belt. Acknowledgements: This study was financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China (Grant: 2014CB440801), Hong Kong Research Grant Council (HKU705311P and HKU704712P), National Science Foundation of China (41273048, 41273012) and a HKU CRCG grant. The work is a contribution of the Joint

Collision of the Tacheng block with the Mayile-Barleik-Tangbale accretionary complex in Western Junggar, NW China: Implication for Early-Middle Paleozoic architecture of the western Altaids

NASA Astrophysics Data System (ADS)

Zhang, Ji'en; Xiao, Wenjiao; Luo, Jun; Chen, Yichao; Windley, Brian F.; Song, Dongfang; Han, Chunming; Safonova, Inna

2018-06-01

Western Junggar in NW China, located to the southeast of the Boshchekul-Chingiz (BC) Range and to the north of the Chu-Balkhash-Yili microcontinent (CBY), played a key role in the architectural development of the western Altaids. However, the mutual tectonic relationships have been poorly constrained. In this paper, we present detailed mapping, field structural geology, and geochemical data from the Barleik-Mayile-Tangbale Complex (BMTC) in Western Junggar. The Complex is divisible into Zones I, II and III, which are mainly composed of Cambrian-Silurian rocks. Zone I contains pillow lava, siliceous shale, chert, coral-bearing limestone, sandstone and purple mudstone. Zone II consists of basaltic lava, siliceous shale, chert, sandstone and mudstone. Zone III is characterized by basalt, chert, sandstone and mudstone. These rocks represent imbricated ocean plate stratigraphy, which have been either tectonically juxtaposed by thrusting or form a mélange with a block-in-matrix structure. All these relationships suggest that the BMTC is an Early-Middle Paleozoic accretionary complex in the eastern extension of the BC Range. These Early Paleozoic oceanic rocks were thrust onto Silurian sediments forming imbricate thrust stacks that are unconformably overlain by Devonian limestone, conglomerate and sandstone containing fossils of brachiopoda, crinoidea, bryozoa, and plant stems and leaves. The tectonic vergence of overturned folds in cherts, drag-related curved cleavages and σ-type structures on the main thrust surface suggests top-to-the-NW transport. Moreover, the positive εNd(t) values of volcanic rocks from the Tacan-1 drill-core, and the positive εHf(t) values and post-Cambrian ages of detrital zircons from Silurian and Devonian strata to the south of the Tacheng block indicate that its basement is a depleted and juvenile lithosphere. And there was a radial outward transition from coral-bearing shallow marine (shelf) to deep ocean (pelagic) environments, and from

Electrical structures in the northwest margin of the Junggar basin: Implications for its late Paleozoic geodynamics

NASA Astrophysics Data System (ADS)

Zhang, Sheng; Xu, Yixian; Jiang, Li; Yang, Bo; Liu, Ying; Griffin, W. L.; Luo, Yong; Huang, Rong; Zhou, Yong; Zhang, Liangliang

2017-10-01

Recent geological, geochemical and geophysical data have inclined to support the presence of a remnant Paleozoic oceanic lithosphere beneath the Western Junggar, southwestern Chinese Altaids. However, regional high-resolution geophysical data have been rarely deployed to image its geometry, making it difficult to trace its evolution and final geodynamic setting. Presently, two magnetotelluric (MT) profiles are deployed across the northwest margin of the Junggar basin and the southern Darbut belt to image the electrical structure of the crust and lithospheric mantle. High-quality data at 102 sites and the quasi-2D indications of phase tensor skew angles and impedance phase ellipses for relatively short periods (up to 500 s) allow us to invert the two profile data by a 2-D scheme. The resistivity cross-section of a NW-SE striking LINE2 sheds light on a fossil intraoceanic subduction system, and reveals the Miaoergou intrusions as a bowl-like pluton, indicating that the multi-phase intrusions primarily formed in a post-collisional setting. The resistivity cross-section of striking NE-SW LINE1 reveals a possible oceanic slab with relatively lower resistivity underlying the low-resistivity sedimentary strata and high-resistivity mélange. Given that the profile of LINE1 cuts the out-rise zone of a subducted slab developed during the late Paleozoic, the 2-D resistivity model may thus represent the zone that have experienced heterogeneous deformation, reflecting subduction with barrier variation parallel to the ancient trench. Moreover, as shown in previous results, the new MT data also illustrate that the Darbut Fault is a thin-skinned structure, which has been erased at depths during the subsequent magmatism.

Isotopically zoned carbonate cements in Early Paleozoic sandstones of the Illinois Basin: δ18O and δ13C records of burial and fluid flow

NASA Astrophysics Data System (ADS)

Denny, Adam C.; Kozdon, Reinhard; Kitajima, Kouki; Valley, John W.

2017-11-01

SEM/SIMS imaging and analysis of δ18O and δ13C in sandstones from a transect through the Illinois Basin (USA) show systematic μm-scale isotopic zonation of up to 10‰ in both carbonate and quartz cements of the middle-Ordovician St. Peter and Cambrian Mt. Simon formations. Quartz δ18O values are broadly consistent with the model of Hyodo et al. (2014), wherein burial and heating in the Illinois Basin is recorded in systematically zoned quartz overgrowths. Observations of zoned dolomite/ankerite cements indicate that they preserve a more extended record of temperature and fluid compositions than quartz, including early diagenesis before or during shallow burial, and late carbonates formed after quartz overgrowths. Many carbonate cements show innermost dolomite with δ18O values (21-25‰ VSMOW) that are too low to have formed by deposition at low temperatures from ancient seawater (δ18O > - 3‰) and most likely reflect mixing with meteoric water. A sharp increase in Fe content is commonly observed in zoned carbonate cements to be associated with a drop in δ18O and an abrupt shift in δ13C to higher or lower values. These changes are interpreted to record the passage of hot metal-rich brines through sandstone aquifers, that was associated with Mississippi-Valley Type (MVT) Pb-Zn deposits (ca. 270 Ma) of the Upper Mississippi Valley. Local variability and individual trends in δ13C are likely controlled by the sources of carbon and the degree to which carbon is sourced from adjacent carbonate units or thermal maturation of organic matter. Quartz overgrowths in sandstones provide an excellent record of conditions during burial, heating, and pressure-solution, whereas carbonate cements in sandstones preserve a more-extended record including initial pre-burial conditions and punctuated fluid flow events.

Paleozoic carbonate buildup (reef) inventory, central and southeastern Idaho

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

Isaacson, P.E.

1987-08-01

Knowledge of central and southeastern Idaho's Paleozoic rocks to date suggest that three styles of buildup (reef) complexes occur in Late Devonian, Mississippian, and Pennsylvanian-Permian time. The Late Devonian Jefferson Formation has stromatoporoid and coral (both rugosan and tabulate) organisms effecting a buildup in the Grandview Canyon vicinity; Early Mississippian Waulsortian-type mud mounds occur in the Lodgepole formation of southeastern Idaho; there are Late Mississippian Waulsortian-type mounds in the Surrett Canyon Formation of the Lost River Range; and cyclic Pennsylvanian-Permian algal and hydrozoan buildups occur in the Juniper gulch Member of the Snaky Canyon Formation in the Arco Hills andmore » Lemhi Range. Late Devonian (Frasnian) carbonates of the Jefferson formation show buildup development on deep ramp sediments.« less

The potential of paleozoic nonmarine trace fossils for paleoecological interpretations

USGS Publications Warehouse

Maples, C.G.; Archer, A.W.

1989-01-01

Many Late Paleozoic environments have been interpreted as marine because of the co-occurrence of supposedly exclusively marine trace fossils. Beginning in the Late Ordovician, however, nonmarine trace-fossil diversity increased throughout the Paleozoic. This diversification of nonmarine organisms and nonmarine trace fossils was especially prevalent in Devonian and later times. Diversification of freshwater organisms is indicated by the large number of freshwater fish, arthropods, annelids and molluscs that had developed by the Carboniferous. In addition to diverse freshwater assemblages, entirely terrestrial vertebrate and invertebrate ecosystems had developed by the Devonian. This rapid diversification of freshwater and terrestrial organisms is inherently linked to development and diversification of land plants and subsequent shedding of large quantities of organic detritus in nonmarine and marginal-marine areas. Nearshore marine organisms and their larvae that are able to tolerate relatively short periods of lowered salinities will follow salt-water wedges inland during times of reduced freshwater discharge. Similarly, amphidromous marine organisms will migrate periodically inland into nonmarine environments. Undoubtedly, both of these processes were active in the Paleozoic. However, both processes are restricted to stream/distributary channels, interdistributary bays, or estuaries. Therefore, the presence of diverse trace-fossil assemblages in association with floodplain deposits is interpreted to reflect true nonmarine adaptation and diversity. Conversely, diverse trace-fossil assemblages in association with stream/distributary channel deposits, interdistributary-bay deposits, or estuarine deposits may reflect migration of salt-water wedges inland, or migration of marine organisms into freshwater environments (amphidromy), or both. ?? 1989.

Lithostratigraphic, conodont, and other faunal links between lower Paleozoic strata in northern and central Alaska and northeastern Russia

USGS Publications Warehouse

Dumoulin, Julie A.; Harris, Anita G.; Gagiev, Mussa; Bradley, Dwight C.; Repetski, John E.

2002-01-01

Lower Paleozoic platform carbonate strata in northern Alaska (parts of the Arctic Alaska, York, and Seward terranes; herein called the North Alaska carbonate platform) and central Alaska (Farewell terrane) share distinctive lithologic and faunal features, and may have formed on a single continental fragment situated between Siberia and Laurentia. Sedimentary successions in northern and central Alaska overlie Late Proterozoic metamorphosed basement; contain Late Proterozoic ooid-rich dolostones, Middle Cambrian outer shelf deposits, and Ordovician, Silurian, and Devonian shallow-water platform facies, and include fossils of both Siberian and Laurentian biotic provinces. The presence in the Alaskan terranes of Siberian forms not seen in wellstudied cratonal margin sequences of western Laurentia implies that the Alaskan rocks were not attached to Laurentia during the early Paleozoic.The Siberian cratonal succession includes Archean basement, Ordovician shallow-water siliciclastic rocks, and Upper Silurian–Devonian evaporites, none of which have counterparts in the Alaskan successions, and contains only a few of the Laurentian conodonts that occur in Alaska. Thus we conclude that the lower Paleozoic platform successions of northern and central Alaska were not part of the Siberian craton during their deposition, but may have formed on a crustal fragment rifted away from Siberia during the Late Proterozoic. The Alaskan strata have more similarities to coeval rocks in some peri-Siberian terranes of northeastern Russia (Kotelny, Chukotka, and Omulevka). Lithologic ties between northern Alaska, the Farewell terrane, and the peri-Siberian terranes diminish after the Middle Devonian, but Siberian afµnities in northern and central Alaskan biotas persist into the late Paleozoic.

The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration

PubMed Central

Scott, Andrew C.; Glasspool, Ian J.

2006-01-01

By comparing Silurian through end Permian [≈250 million years (Myr)] charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long-term variations in fire occurrence and fire system diversification are related to fluctuations in Late Paleozoic atmospheric oxygen concentration. Charcoal, a proxy for fire, occurs in the fossil record from the Late Silurian (≈420 Myr) to the present. Its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13% to 35% (the “fire window”). Herein, we observe that, as predicted, atmospheric oxygen levels rise from ≈13% in the Late Devonian to ≈30% in the Late Permian so, too, fires progressively occur in an increasing diversity of ecosystems. Sequentially, data of note include: the occurrence of charcoal in the Late Silurian/Early Devonian, indicating the burning of a diminutive, dominantly rhyniophytoid vegetation; an apparent paucity of charcoal in the Middle to Late Devonian that coincides with a predicted atmospheric oxygen low; and the subsequent diversification of fire systems throughout the remainder of the Late Paleozoic. First, fires become widespread during the Early Mississippian, they then become commonplace in mire systems in the Middle Mississippian; in the Pennsylvanian they are first recorded in upland settings and finally, based on coal petrology, become extremely important in many Permian mire settings. These trends conform well to changes in atmospheric oxygen concentration, as predicted by modeling, and indicate oxygen levels are a significant control on long-term fire occurrence. PMID:16832054

Paleomagnetic results from Northeast Anatolia: remagnetization in Late Cretaceous sandstones and tectonic rotation at the Eastern extension of the Izmir-Ankara-Erzincan suture zone

NASA Astrophysics Data System (ADS)

Cengiz Çinku, Mualla

2017-12-01

Paleomagnetic results obtained from Upper Cretaceous sandstones in Northeastern Anatolia demonstrate that the entire area from Erzincan to Kars has been remagnetised. The remagnetisation was acquired before the Middle Eocene collision between the Eastern Pontides and the Arabian Platform because Middle Eocene sandstones carry primary natural remanent magnetisations. The post-folding in situ mean direction of the Upper Cretaceous sandstones is compared with mean directions of younger, Middle Eocene to present rock formations. As a result, a two-stage antagonistic rotation mechanism is proposed. First, the collision between the Pontides and the Taurides between Late Cretaceous and Middle Eocene was associated by clockwise rotation of 26°. In the second stage between Middle Eocene and Middle Miocene and beyond, counterclockwise rotations up to 52° of the Pontide and Anatolide blocks and clockwise rotations of the Van Block were characterised by regional shortening and westward escape.

Paleogeography of the upper Paleozoic basins of southern South America: An overview

NASA Astrophysics Data System (ADS)

Limarino, Carlos O.; Spalletti, Luis A.

2006-12-01

The paleogeographic evolution of Late Paleozoic basins located in southern South America is addressed. Three major types of basins are recognized: infracratonic or intraplate, arc-related, and retroarc. Intraplate basins (i.e., Paraná, Chaco-Paraná, Sauce Grande-Colorado, and La Golondrina) are floored by continental or quasi-continental crust, with low or moderate subsidence rates and limited magmatic and tectonic activity. Arc-related basins (northern and central Chile, Navidad-Arizaro, Río Blanco, and Calingasta-Uspallata basins and depocenters along Chilean Patagonia) show a very complex tectonic history, widespread magmatic activity, high subsidence rates, and in some cases metamorphism of Late Paleozoic sediments. An intermediate situation corresponds to the retroarc basins (eastern Madre de Dios, Tarija, Paganzo, and Tepuel-Genoa), which lack extensive magmatism and metamorphism but in which coeval tectonism and sedimentation rates were likely more important than those in the intraplate region. According to the stratigraphic distribution of Late Paleozoic sediments, regional-scale discontinuities, and sedimentation pattern changes, five major paleogeographic stages are proposed. The lowermost is restricted to the proto-Pacific and retroarc basins, corresponds to the Mississippian (stage 1), and is characterized by shallow marine and transitional siliciclastic sediments. During stage 2 (Early Pennsylvanian), glacial-postglacial sequences dominated the infracratonic (or intraplate) and retroarc basins, and terrigenous shallow marine sediments prevailed in arc-related basins. Stage 3 (Late Pennsylvanian-Early Cisuralian) shows the maximum extension of glacial-postglacial sediments in the Paraná and Sauce Grande-Colorado basins (intraplate region), whereas fluvial deposits interfingering with thin intervals of shallow marine sediments prevailed in the retroarc basins. To the west, arc-related basins were dominated by coastal to deep marine conditions

Biostratigraphy and petrography of upper Paleozoic rocks of Sierra Las Pintas, northern Baja California

NASA Astrophysics Data System (ADS)

Navas-Parejo, Pilar; Lara-Peña, R. Aaron; Torres-Martínez, Miguel Angel; Martini, Michelangelo

2018-07-01

A transported crinoid fauna is herein described for the first time in the Paleozoic succession cropping out in the Sierra Las Pintas, northern Baja California, northwestern Mexico. The fossil association includes Heterostelechus texanus Moore and Jeffords, Preptopremnum laeve? Moore and Jeffords, and Mooreanteris perforatus Moore and Jeffords, which indicates a Middle Pennsylvanian-early Permian time-averaged age. The studied area corresponds with the northernmost outcrop of definitely late Paleozoic deep-water facies in northwestern Mexico and the southern United States. Petrographic analyses indicate that the studied metasandstones were primarily derived from high-grade metamorphic rocks and from a shallow-water platform environment dominated by crinoid meadows. These results allow the correlation of the studied metasedimentary rocks with the Carboniferous Rancho Nuevo Formation of the Sonora allochthon, which crops out in central Sonora. The Sonora allochthon includes an Early Ordovician-Late Pennsylvanian sedimentary succession that was deposited in the oceanic basin located south of the Laurentian craton. Therefore, upper Paleozoic metasedimentary rocks of the Sierra Las Pintas were deposited along the same continental margin of Laurentia as those rocks in the Sonora allochthon, and were mostly derived from metamorphic rocks of the continental craton and by the typical Carboniferous encrinites, which characterize the shallow-water rocks of central and northern Sonora.

North American Paleozoic land snails with a summary of other Paleozoic nonmarine snails

USGS Publications Warehouse

Solem, Alan; Yochelson, Ellis Leon

1979-01-01

family placement of Anthracopupa, growth forms of modern pupillid and tornatellinid snails have been distinguished. The apertural barriers in Anthracopupa are identical in placement and growth pattern with those of living Tornatellinidae and independently confirm the family placement derived from study of the general form. One new species, A. sturgeoni, has been named. Anthracopupa is found most commonly in thin limestones interpreted as having been deposited in pools into which the small shells floated. Dendropupa is most commonly found in erect tree stumps that were covered by rapid sedimentation. Both environments are similar to those in which the shells of allied living species may be found today, and the fossils support environmental interpretations made entirely from lithology. A survey of the few European occurrences of Paleozoic land snails indicates that both Anthracopupa and Dendropupa occur in Lower Permian strata; Anthracopupa is known from beds as old as Westphalian B. These genera cannot be used for determining the Carboniferous-Permian boundary. Both the long local stratigraphic range of A. brittanica and D. vetusta reported in the literature and the moderately long range and great variability of A. ohioensis suggest that the land snails have little stratigraphic utility. On the other hand, the occurrence of these land snails in the late Paleozoic of the Northern Hemisphere provides further fossil evidence suggestive of a closed Atlantic Ocean at that time. A comparison of the Paleozoic and the present distributions of land -snail families on both sides of the Atlantic provides some interesting data on geographic shifts of organisms. Finally, the assignment of the earliest land snails to extant taxa at the family level indicates that the subclass Pulmonata has been very conservative in its evolution after initial radiation. A few notes on Paleozoic freshwater snails complete this survey.

Early paleozoic gabbro-amphibolites in the structure of the Bureya Terrane (eastern part of the Central Asian Fold Belt): First geochronological data and tectonic position

NASA Astrophysics Data System (ADS)

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

2012-07-01

Resulting from U-Pb geochronological study, it has been found that the gabbro-amphibolites composing the Bureya (Turan) Terrane in the eastern part of the Central Asian Fold Belt are Early Paleozoic (Early Ordovician; 455 ± 1.5 Ma) in age rather than Late Proterozoic as was believed earlier. The gabbro-amphibolites and associated metabasalts are close to tholeiites of the intraoceanic island arcs in terms of the geochemical properties. It is suggested that the tectonic block composed of these rocks was initially a seafloor fragment that divided the Bureya and Argun terranes in the Early Paleozoic and was later tectonically incorporated into the modern structure of the Bureya Terrane as a result of Late Paleozoic and Mesozoic events.

Late Paleozoic closure of the Ob-Zaisan Ocean along the Irtysh/Chara shear zone and implications for arc amalgamation and oroclinal bending in the western Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Li, Pengfei; Sun, Min; Rosenbaum, Gideon

2016-04-01

The Irtysh/Chara Shear Zone is one of the largest strike-slip systems in the Central Asian Orogenic Belt (CAOB). It records collisional processes of the peri-Siberian orogenic system with the West Junggar-Kazakhstan-Tianshan orogenic system following the closure of the Ob-Zaisan Ocean, but the exact timing of these events remains enigmatic. We conducted detailed structural analysis along the Irtysh Shear Zone (NW China), which together with new geochronological data allows us to reconstruct the tectonic evolution during the final closure of the Ob-Zaisan Ocean. Our results showed that subduction-accretion processes lasted at least until the Late Carboniferous in the Chinese Altai and the East/West Junggar. The subsequent arc amalgamation is characterized by a cycle of crustal thickening, orogenic collapse and transpressional thickening. On a larger scale, the West Junggar- Kazakhstan -Tianshan orogenic system defines a U-shape oroclinal structure (e.g. Xiao et al., 2010). A major phase of oroclinal bending that involved ~110° rotation may have occurred during the Late Devonian to Early Carboniferous (Levashova et al., 2012). Previous authors have linked oroclinal bending with the late Paleozoic amalgamation of the western CAOB, and proposed that a quasi-linear West Junggar- Kazakhstan -Tianshan orogenic system was buckled during the convergence of the Siberian and Tarim cratons following the closure of the Ob-Zaisan Ocean (in the north) and the South Tianshan Ocean (in the south) (e.g. Abrajevitch et al., 2008). This model, however, is not supported by our new data that constrain the closure of the Ob-Zaisan Ocean to the Late Carboniferous. Alternatively, we propose that oroclinal bending may have involved two phases of bending, with the ~110° rotation in the Late Devonian to Early Carboniferous possibly associated with trench retreat. Further tightening may have occurred in response to the convergence of the Siberian and Tarim cratons during the Late

Nature and classification of waterlain glaciogenic sediments, exemplified by Pleistocene, Late Paleozoic and Late Precambrian deposits

NASA Astrophysics Data System (ADS)

Gravenor, C. P.; von Brunn, V.; Dreimanis, A.

1984-03-01

This study of waterlain glaciogenic sediments is designed to present both a review and new information on glaciogenic subaquatic deposits of differing age in a number of localities in North and South America and South Africa. The Late Paleozoic glaciogenic deposits of the ParanáBasin in Brazil and the Karoo Basin of South Africa are singled out for special attention as they show a reasonably complete lateral sequence of terrestrial to off-shore glaciogenic sedimentation. Although the environment of subaquatic glaciogenic sedimentation varies from one area to the next, certain common elements are found which can be used to develop a generalized model for both glaciomarine and glaciolacustrine sedimentation. For descriptive purposes, the model is divided into two broad categories: a shelf facies and a basinal facies. The shelf facies is marked by massive diamicton(ite) which may be 200 m or more in thickness and which is frequently overlain by a complex of clastic sediments consisting primarily of gravity and fluid flows. The basinal facies is marked by products of subaquatic slumps and more distal turbidites and glaciomarine sediments. New terminology is introduced. The massive diamicton(ite), which is diagnostic of the shelf facies, probably represents deposition from the base of active ice in a subaquatic environment and is termed undermelt diamicton(ite). The gravity and fluid flows which are usually found overlying undermelt diamicton(ite) and in the basinal facies are subdivided into six categories: glaciogenic subaquatic outwash, glaciogenic suspension flow, glaciogenic chaotic debris flow, glaciogenic subaquatic debris flow, glaciogenic slurry flow and glaciogenic turbidity flow. The relative abundance of undermelt diamicton(ite) and the various types of gravity and fluid flows can be used to define inner shelf, outer shelf, inner basin and outer basin facies of glaciomarine sedimentation.

Late Paleozoic to Jurassic chronostratigraphy of coastal southern Peru: Temporal evolution of sedimentation along an active margin

NASA Astrophysics Data System (ADS)

Boekhout, F.; Sempere, T.; Spikings, R.; Schaltegger, U.

2013-11-01

We present an integrated geochronological and sedimentological study that significantly revises the basin and magmatic history associated with lithospheric thinning in southern coastal Peru (15-18°S) since the onset of subduction at ˜530 Ma. Until now, estimating the age of the sedimentary and volcanic rocks has heavily relied on paleontologic determinations. Our new geochronological data, combined with numerous field observations, provide the first robust constraints on their chronostratigraphy, which is discussed in the light of biostratigraphical attributions. A detailed review of the existing local units simplifies the current stratigraphic nomenclature and clarifies its absolute chronology using zircon U-Pb ages. We observe that the Late Paleozoic to Jurassic stratigraphy of coastal southern Peru consists of two first-order units, namely (1) the Yamayo Group, a sedimentary succession of variable (0-2 km) thickness, with apparently no nearby volcanic lateral equivalent, and (2) the overlying Yura Group, consisting of a lower, 1-6 km-thick volcanic and volcaniclastic unit, the Chocolate Formation, and an upper, 1-2 km-thick sedimentary succession that are in markedly diachronous contact across the coeval arc and back-arc. We date the local base of the Chocolate Formation, and thus of the Yura Group, to 216 Ma, and show that the underlying Yamayo Group spans a >110 Myr-long time interval, from at least the Late Visean to the Late Triassic, and is apparently devoid of significant internal discontinuities. The age of the top of the Chocolate Formation, i.e. of the volcanic arc pile, varies from ˜194 Ma to less than ˜135 Ma across the study area. We suggest that this simplified and updated stratigraphic framework can be reliably used as a reference for future studies.

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

USGS Publications Warehouse

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

1987-01-01

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

Abiotic and biotic responses to Milankovitch-forced megamonsoon and glacial cycles recorded in South China at the end of the Late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

Fang, Qiang; Wu, Huaichun; Hinnov, Linda A.; Tian, Wenqian; Wang, Xunlian; Yang, Tianshui; Li, Haiyan; Zhang, Shihong

2018-04-01

At the end of the Late Paleozoic Ice Age (LPIA) from late Early Permian to early Late Permian, the global climate was impacted by a prevailing megamonsoon and Gondwanan deglaciation. To better understand the abiotic and biotic responses to Milankovitch-forced climate changes during this time period, multi-element X-ray fluorescence (XRF) geochemistry analyses were conducted on 948 samples from the late Early-late Middle Permian Maokou Formation at Shangsi, South China. The Fe/Ti, S/Ti, Ba/Ti and Ca time series, which were calibrated with an existing "floating" astronomical time scale (ATS), show the entire suite of Milankovitch rhythms including 405 kyr long eccentricity, 128 and 95 kyr short eccentricity, 33 kyr obliquity and 20 kyr precession. Spectral coherency and cross-phase analysis reveals that chemical weathering (monitored by Fe/Ti) and upwelling (captured by S/Ti and Ba/Ti) are nearly antiphase in the precession band, which suggests a contrast between summer and winter monsoon intensities. Strong obliquity signal in the Ba/Ti series is proposed to derive from changes in thermohaline circulation intensity from glaciation dynamics in southern Gondwana. The abundance of foraminifer, brachiopod and ostracod faunas within the Maokou Formation were mainly controlled by the 1.1 Myr obliquity modulation cycle. The obliquity-forced high-nutrient and oxygen-depleted conditions generally produced a benthic foraminifer bloom, but threatened the brachiopod and ostracod faunas.

Paleomagnetism of the Santa Fé Group, central Brazil: Implications for the late Paleozoic apparent polar wander path for South America

NASA Astrophysics Data System (ADS)

Brandt, Daniele; Ernesto, Marcia; Rocha-Campos, Antonio Carlos; Dos Santos, Paulo Roberto

2009-02-01

Paleomagnetic and rockmagnetic data are reported for the Floresta Formation (Santa Fé Group) of the Sanfranciscana Basin, central Brazil. This formation represents the Permo-Carboniferous glacial record of the basin and comprises the Brocotó (diamictites and flow diamictites), Brejo do Arroz (red sandstones and shales with dropstones and invertebrate trails), and Lavado (red sandstones) members, which crop out near the cities of Santa Fé de Minas and Canabrava, Minas Gerais State. Both Brejo do Arroz and Lavado members were sampled in the vicinities of the two localities. Alternating field and thermal demagnetizations of 268 samples from 76 sites revealed reversed components of magnetization in all samples in accordance with the Permo-Carboniferous Reversed Superchron. The magnetic carriers are magnetite and hematite with both minerals exhibiting the same magnetization component, suggesting a primary origin for the remanence. We use the high-quality paleomagnetic pole for the Santa Fé Group (330.9°E 65.7°S; N = 60; α95 = 4.1°; k = 21) in a revised late Carboniferous to early Triassic apparent polar wander path for South America. On the basis of this result it is shown that an early Permian Pangea A-type fit is possible if better determined paleomagnetic poles become available.

Electrofacies vs. lithofacies sandstone reservoir characterization Campanian sequence, Arshad gas/oil field, Central Sirt Basin, Libya

NASA Astrophysics Data System (ADS)

Burki, Milad; Darwish, Mohamed

2017-06-01

The present study focuses on the vertically stacked sandstones of the Arshad Sandstone in Arshad gas/oil field, Central Sirt Basin, Libya, and is based on the conventional cores analysis and wireline log interpretation. Six lithofacies types (F1 to F6) were identified based on the lithology, sedimentary structures and biogenic features, and are supported by wireline log calibration. From which four types (F1-F4) represent the main Campanian sandstone reservoirs in the Arshad gas/oil field. Lithofacies F5 is the basal conglomerates at the lower part of the Arshad sandstones. The Paleozoic Gargaf Formation is represented by lithofacies F6 which is the source provenance for the above lithofacies types. Arshad sediments are interpreted to be deposited in shallow marginal and nearshore marine environment influenced by waves and storms representing interactive shelf to fluvio-marine conditions. The main seal rocks are the Campanian Sirte shale deposited in a major flooding events during sea level rise. It is contended that the syn-depositional tectonics controlled the distribution of the reservoir facies in time and space. In addition, the post-depositional changes controlled the reservoir quality and performance. Petrophysical interpretation from the porosity log values were confirmed by the conventional core measurements of the different sandstone lithofacies types. Porosity ranges from 5 to 20% and permeability is between 0 and 20 mD. Petrophysical cut-off summary of the lower part of the clastic dominated sequence (i. e. Arshad Sandstone) calculated from six wells includes net pay sand ranging from 19.5‧ to 202.05‧, average porosity from 7.7 to 15% and water saturation from 19 to 58%.

Tectono-thermal Evolution of the Lower Paleozoic Petroleum Source Rocks in the Southern Lublin Trough: Implications for Shale Gas Exploration from Maturity Modelling

NASA Astrophysics Data System (ADS)

Botor, Dariusz

2018-03-01

The Lower Paleozoic basins of eastern Poland have recently been the focus of intensive exploration for shale gas. In the Lublin Basin potential unconventional play is related to Lower Silurian source rocks. In order to assess petroleum charge history of these shale gas reservoirs, 1-D maturity modeling has been performed. In the Łopiennik IG-1 well, which is the only well that penetrated Lower Paleozoic strata in the study area, the uniform vitrinite reflectance values within the Paleozoic section are interpreted as being mainly the result of higher heat flow in the Late Carboniferous to Early Permian times and 3500 m thick overburden eroded due to the Variscan inversion. Moreover, our model has been supported by zircon helium and apatite fission track dating. The Lower Paleozoic strata in the study area reached maximum temperature in the Late Carboniferous time. Accomplished tectono-thermal model allowed establishing that petroleum generation in the Lower Silurian source rocks developed mainly in the Devonian - Carboniferous period. Whereas, during Mesozoic burial, hydrocarbon generation processes did not develop again. This has negative influence on potential durability of shale gas reservoirs.

Artesian pressures and water quality in Paleozoic aquifers in the Ten Sleep area of the Bighorn Basin, north-central Wyoming

USGS Publications Warehouse

Cooley, M.E.

1985-01-01

Major Paleozoic artesian aquifers in the southeastern Bighorn Basin of Wyoming area, in descending order, the Tensleep Sandstone; the Madison Limestone and Bighorn Dolomite, which together form the Madison-Bighorn aquifer; and the Flathead Sandstone. Operating yields commonly are more than 1,000 gallons per minute from flowing wells completed in the Madison-Bighorn aquifer. The initial test of one well indicated a flow of 14,000 gallons per minute. Wellhead pressures range from less than 50 to more than 400 pounds per square inch. Transmissivities are 500-1,900 feet squared per day for the Madison-Bighorn aquifer and 90-325 feet squared per day for the Tensleep and Flathead Sandstones. Despite extensive development for irrigation there have been few decreases in pressure. Some decreases in pressure have occurred in wells completed in the Flathead Sandstone. Fractures along linear structural features result in significant secondary permeability and allow upward interformational movement of water that affects the altitude of the potentiometric surfaces in the Tensleep Sandstone and Madison-Bighorn aquifer. Upward-moving water from the Tensleep and other formations discharges at the land surface as springs along or near these lineations. Water from the aquifers generally contains minimal concentrations of dissolved solids and individual constituents but has excessive hardness. The water is satisfactory for irrigation and other purposes when hardness is not a detrimental factor. Wellhead temperatures range from 11 degrees to 27.5 degrees C, giving a geothermal gradient of about 0.44 degrees C per 100 feet. (USGS)

The Timan-Pechora Basin province of northwest Arctic Russia; Domanik, Paleozoic total petroleum system

USGS Publications Warehouse

Lindquist, Sandra J.

1999-01-01

The Domanik-Paleozoic oil-prone total petroleum system covers most of the Timan-Pechora Basin Province of northwestern Arctic Russia. It contains nearly 20 BBOE ultimate recoverable reserves (66% oil). West of the province is the early Precambrian Eastern European craton margin. The province itself was the site of periodic Paleozoic tectonic events, culminating with the Hercynian Uralian orogeny along its eastern border. The stratigraphic record is dominated by Paleozoic platform and shelf-edge carbonates succeeded by Upper Permian to Triassic molasse siliciclastics that are locally present in depressions. Upper Devonian (Frasnian), deep marine shale and limestone source rocks ? with typically 5 wt % total organic carbon ? by middle Mesozoic time had generated hydrocarbons that migrated into reservoirs ranging in age from Ordovician to Triassic but most focused in Devonian and Permian rocks. Carboniferous structural inversions of old aulacogen borders, and Hercynian (Permian) to Early Cimmerian (Late Triassic to Early Jurassic) orogenic compression not only impacted depositional patterns, but also created and subsequently modified numerous structural traps within the province.

Provenance and depositional conditions of Cretaceous-Paleogene boundary sandstones from northeastern Mexico

NASA Astrophysics Data System (ADS)

Rehrmann, Stephanie; Augustsson, Carita; Izaguirre Valdez, Rocio Nereyda; Jenchen, Uwe; Schulte, Peter

2012-12-01

We compare Late Maastrichtian siliciclastic sandstone in northeastern Mexico with those representing the Cretaceous-Paleogene (K-Pg) boundary to reveal differences in provenance and depositional conditions between background sedimentation and K-Pg sand. Lithology and compositional variations are presented for the deep-water Burgos Basin and the shallow-water La Popa Basin. The Late Maastrichtian sandstones in the Burgos Basin have sharp lower contacts, contain abundant trace fossils and are separated by meter-thick marl layers. They represent sporadic mass flows from coastal areas separated by long phases of hemipelagic sedimentation. The K-Pg sandstone layers are amalgamated, contain thin marl intercalations only in the uppermost part and trace fossils are present in the top sandstone layer only. Also this succession represents mass-flow deposits, but the sand may have been deposited during a very short period. The La Popa Basin sandstones represent deltaic sedimentation interrupted by submarine channel deposition during the K-Pg boundary transition with abundant rip-up clasts and bioclasts at the base. The sandstones of the Burgos Basin are quartz to akosic wacke dominated by quartz (> 90%) and some feldspar (< 10%) in calcite cement and matrix. Lithic fragments are rare and dominated by chert and bioclasts. Ultra-stable heavy minerals (ZTR = 50-80) and plutonic quartz grains (ca. 40% of the total quartz population) are particularly common in the K-Pg sandstones. In the Maastrichtian sandstones, metamorphic heavy minerals, particularly chlorite, clinozoisite, and tourmaline (20-50% of the heavy mineral population), and metamorphic quartz (80% of the quartz population) have higher abundances. The La Popa sandstones are subarkose to arkose and arkosic wacke and have a high abundance of feldspar (15-30%) and lithic fragments (5-20%), mainly of siltstone and carbonate. The sandstones from both basins have chemical compositions typical for recycling (Zr/Sc = 12-27 and

Sedimentary record of late Paleozoic to Recent tectonism in central Asia — analysis of subsurface data from the Turan and south Kazak domains

NASA Astrophysics Data System (ADS)

Thomas, J. C.; Cobbold, P. R.; Shein, V. S.; Le Douaran, S.

1999-11-01

The Turan and south Kazak domains (TSK) are in central Asia, between the Caspian Sea and the Tien Shan. The area is covered by sediments, deposited since the Late Permian during a series of tectonic events closely related to the history of two oceanic domains, Paleotethys and Neotethys. Sedimentary basins on the TSK therefore provide constraints on the tectonic development of the southern margin of Eurasia since the Late Permian. Our study is based on structure-contour maps and isopach maps of five key stratigraphic markers, of Late Permian to Tertiary age. Isopach maps help locate major faults and delimit sedimentary basins, providing information on vertical motions and, in some instances, horizontal motions. Subsidence associated with extension appears to have dominated the TSK, from the Late Permian to the Eocene. The extension may have been of back-arc type in southern Eurasia, next to the active margin, where the Paleotethys and Neotethys successively subducted toward the north. Here, sedimentary basins are both wide and deep (up to 15 km). During the Mesozoic, two compressional events of regional significance occurred in association with accretion of continental blocks at the southern margin of Eurasia. The first one, at the end of the Triassic, led to strong selective inversion of basins over the Turan domain. The second one, during the Late Jurassic-Early Cretaceous, had weaker effects. Since the Oligocene, following collision of both India and Arabia with Eurasia, inversion has become more generalized and compressional basins have formed on the TSK. Throughout the entire history of development of the TSK, from the Late Permian to the Tertiary, structures of Paleozoic and early Mesozoic age have exerted a strong control on sedimentation and especially on the location of depocenters. The south Kazak domain has registered little subsidence, in comparison with the Turan domain, where some basins have become very deep.

Kaolinite, illite and quartz dissolution in the karstification of Paleozoic sandstones of the Furnas Formation, Paraná Basin, Southern Brazil

NASA Astrophysics Data System (ADS)

Melo, Mário Sérgio de; Guimarães, Gilson Burigo; Chinelatto, Adilson Luiz; Giannini, Paulo César Fonseca; Pontes, Henrique Simão; Chinelatto, Adriana Scoton Antonio; Atencio, Daniel

2015-11-01

Karstification processes in sandstones of the Furnas Formation, Silurian to Devonian of the Paraná Basin, have been described since the mid-twentieth century. However, some geologists still doubt the idea of true karst in sandstones. Studies carried out in the Campos Gerais region, Paraná State, Southern Brazil, aimed at investigating the nature of erosion processes in Furnas Formation and the role of the dissolution in the development of their notorious erosive features and underground cavities. These studies have led to the recognition of dissolution macro to micro features ('furnas', caves, ponds, sinks, ruiniform relief on cliffs and rocky surfaces, grain corrosion, speleothems, mineral reprecipitation and incrustation). The analysis (scanning electron microscopy, energy dispersive spectrometry and x-ray diffractometry) of sandstones and their alterites has indicated significant dissolution of clay cement along with discrete quartz grain dissolution. This mesodiagenetic cement (kaolinite and illite) is dissolved and reprecipitated as clay minerals with poorly developed crystallinity along with other minerals, such as variscite and minerals of the alunite supergroup, suggesting organic participation in the processes of dissolution and incrustation. The mineral reprecipitation usually forms centimetric speleothems, found in cavities and sheltered rocky surfaces. The cement dissolution associated with other factors (fractures, wet weather, strong hydraulic gradient, antiquity of the landforms) leads to the rock arenisation, the underground erosion and the appearance of the karst features. Carbonate rocks in the basement may locally be increasing the karst forms in the overlying Furnas Formation. The recognition of the karst character of the Furnas Formation sandstones has important implications in the management of underground water resources (increasingly exploited in the region), in the use of the unique geological heritage and in the prevention of geo

Assessment of Appalachian Basin Oil and Gas Resources: Utica-Lower Paleozoic Total Petroleum System

USGS Publications Warehouse

Ryder, Robert T.

2008-01-01

The Utica-Lower Paleozoic Total Petroleum System (TPS) is an important TPS identified in the 2002 U.S. Geological Survey (USGS) assessment of undiscovered, technically recoverable oil and gas resources in the Appalachian basin province (Milici and others, 2003). The TPS is named for the Upper Ordovician Utica Shale, which is the primary source rock, and for multiple lower Paleozoic sandstone and carbonate units that are the important reservoirs. Upper Cambrian through Upper Silurian petroleum-bearing strata that constitute the Utica-Lower Paleozoic TPS thicken eastward from about 2,700 ft at the western margin of the Appalachian basin to about 12,000 ft at the thrust-faulted eastern margin of the Appalachian basin. The Utica-Lower Paleozoic TPS covers approximately 170,000 mi2 of the Appalachian basin from northeastern Tennessee to southeastern New York and from central Ohio to eastern West Virginia. The boundary of the TPS is defined by the following geologic features: (1) the northern boundary (from central Ontario to northeastern New York) extends along the outcrop limit of the Utica Shale-Trenton Limestone; (2) the northeastern boundary (from southeastern New York, through southeastern Pennsylvania-western Maryland-easternmost West Virginia, to northern Virginia) extends along the eastern limit of the Utica Shale-Trenton Limestone in the thrust-faulted eastern margin of the Appalachian basin; (3) the southeastern boundary (from west-central and southwestern Virginia to eastern Tennessee) extends along the eastern limit of the Trenton Limestone in the thrust-faulted eastern margin of the Appalachian basin; (4) the southwestern boundary (from eastern Tennessee, through eastern Kentucky, to southwestern Ohio) extends along the approximate facies change from the Trenton Limestone with thin black shale interbeds (on the east) to the equivalent Lexington Limestone without black shale interbeds (on the west); (5) the northern part of the boundary in southwestern Ohio

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

USGS Publications Warehouse

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

2003-01-01

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

Land plants, weathering, and Paleozoic climatic evolution

NASA Astrophysics Data System (ADS)

Goddéris, Yves; Maffre, Pierre; Donnadieu, Yannick; Carretier, Sébastien

2017-04-01

At the end of the Paleozoic, the Earth plunged into the longest and most severe glaciation of the Phanerozoic eon (Montanez et al., 2013). The triggers for this event (called the Late Paleozoic Ice Age, LPIA) are still debated. Based on field observations and laboratory experiments showing that CO2 consumption by rock weathering is enhanced by the presence of plants, the onset of the LPIA has been related to the colonization of the continents by vascular plants in the latest Devonian. By releasing organic acids, concentrating respired CO2 in the soil, and by mechanically breaking rocks with their roots, land plants may have increased the weatherability of the continental surfaces. The "greening" of the continents may also have contributed to an enhanced burial of organic carbon in continental sedimentary basins, assuming that lignin decomposers have not yet evolved (Berner, 2004). As a consequence, CO2 went down, setting the conditions for the onset of the LPIA. This scenario is now widely accepted in the scientific community, and reinforces the feeling that biotic evolutionary steps are main drivers of the long-term climatic evolution. Although appealing, this scenario suffers from some weaknesses. The timing of the continent colonization by vascular plants was achieved in the late Devonian, several tens of million years before the onset of the LPIA (Davies and Gibling, 2013). Second, lignin decomposer fungi were present at the beginning of the Carboniferous, 360 million years ago while the LPIA started around 340-330 Ma (Nelsen et al., 2016). Land plants have also decreased the continental albedo, warming the Earth surface and promoting runoff. Weathering was thus facilitated and CO2 went down. Yet, temperature may have stayed constant, the albedo change compensating for the CO2 fall (Le Hir et al., 2010). From a modelling point of view, the effect of land plants on CO2 consumption by rock weathering is accounted for by forcing the weatherability of the

Late Ordovician (Ashgillian) glacial deposits in southern Jordan

NASA Astrophysics Data System (ADS)

Turner, Brian R.; Makhlouf, Issa M.; Armstrong, Howard A.

2005-11-01

The Late Ordovician (Ashgillian) glacial deposits in southern Jordan, comprise a lower and upper glacially incised palaeovalley system, occupying reactivated basement and Pan-African fault-controlled depressions. The lower palaeovalley, incised into shoreface sandstones of the pre-glacial Tubeiliyat Formation, is filled with thin glaciofluvial sandstones at the base, overlain by up to 50 m of shoreface sandstone. A prominent glaciated surface near the top of this palaeovalley-fill contains intersecting glacial striations aligned E-W and NW-SE. The upper palaeovalley-fill comprises glaciofluvial and marine sandstones, incised into the lower palaeovalley or, where this is absent, into the Tubeiliyat Formation. Southern Jordan lay close to the margin of a Late Ordovician terrestrial ice sheet in Northwest Saudi Arabia, characterised by two major ice advances. These are correlated with the lower and upper palaeovalleys in southern Jordan, interrupted by two subsidiary glacial advances during late stage filling of the lower palaeovalley when ice advanced from the west and northwest. Thus, four ice advances are now recorded from the Late Ordovician glacial record of southern Jordan. Disturbed and deformed green sandstones beneath the upper palaeovalley-fill in the Jebel Ammar area, are confined to the margins of the Hutayya graben, and have been interpreted as structureless glacial loessite or glacial rock flour. Petrographic and textural analyses of the deformed sandstones, their mapped lateral transition into undeformed Tubeiliyat marine sandstones away from the fault zone, and the presence of similar sedimentary structures to those in the pre-glacial marine Tubeiliyat Formation suggest that they are a locally deformed facies equivalent of the Tubeiliyat, not part of the younger glacial deposits. Deformation is attributed to glacially induced crustal stresses and seismic reactivation of pre-existing faults, previously weakened by epeirogenesis, triggering sediment

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

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

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

1988-02-01

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

Paleozoic and mesozoic evolution of East-Central California

USGS Publications Warehouse

Stevens, C.H.; Stone, P.; Dunne, G.C.; Greene, D.C.; Walker, J.D.; Swanson, B.J.

1997-01-01

East-central California, which encompasses an area located on the westernmost part of sialic North America, contains a well-preserved record of Paleozoic and Mesozoic tectonic events that reflect the evolving nature of the Cordilleran plate margin to the west. After the plate margin was formed by continental rifting in the Neoproterozoic, sediments comprising the Cordilleran miogeocline began to accumulate on the subsiding passive margin. In east-central California, sedimentation did not keep pace with subsidence, resulting in backstepping of a series of successive carbonate platforms throughout the early and middle Paleozoic. This phase of miogeoclinal development was brought to a close by the Late Devonian-Early Mississippian Antler orogeny, during the final phase of which oceanic rocks were emplaced onto the continental margin. Subsequent Late Mississippian-Pennsylvanian faulting and apparent reorientation of the carbonate platform margin are interpreted to have been associated with truncation of the continental plate on a sinistral transform fault zone. In the Early Permian, contractional deformation in east-central California led to the development of a narrow, uplifted thrust belt flanked by marine basins in which thick sequences of deep-water strata accumulated. A second episode of contractional deformation in late Early Permian to earliest Triassic time widened and further uplifted the thrust belt and produced the recently identified Inyo Crest thrust, which here is correlated with the regionally significant Last Chance thrust. In the Late Permian, about the time of the second contractional episode, extensional faulting created shallow sedimentary basins in the southern Inyo Mountains. In the El Paso Mountains to the south, deformation and plutonism record the onset of subduction and arc magmatism in late Early Permian to earliest Triassic time along this part of the margin. Tectonism had ceased in most of east-central California by middle to late Early

Paleozoic and Mesozoic deformations in the central Sierra Nevada, California

USGS Publications Warehouse

Nokleberg, Warren J.; Kistler, Ronald Wayne

1980-01-01

Analysis of structural and stratigraphic data indicates that several periods of regional deformation, consisting of combined folding, faulting, cataclasis, and regional metamorphism, occurred throughout the central Sierra Nevada during Paleozoic and Mesozoic time. The oldest regional deformation occurred alono northward trends during the Devonian and Mississippian periods in most roof pendants containing lower Paleozoic metasedimentary rocks at the center and along the crest of the range. This deformation is expressed in some roof pendants by an angular unconformity separating older thrice-deformed from younger twice-deformed Paleozoic metasedimentary rocks. The first Mesozoic deformation, which consisted of uplift and erosion and was accompanied by the onset of Andean-type volcanism during the Permian and Triassic, is expressed by an angular unconformity in several roof pendants from the Saddlebag Lake to the Mount Morrison areas. This unconformity is defined by Permian and Triassic andesitic to rhyolitic metavolcanic rocks unconformably overlying more intensely deformed Pennsylvanian, Permian(?), and older metasedimentary rocks. A later regional deformation occurred during the Triassic along N. 20?_30? W. trends in Permian and Triassic metavolcanic rocks of the Saddlebag Lake and Mount Dana roof pendants, in upper Paleozoic rocks of the Pine Creek roof pendant, and in the Calaveras Formation of the western metamorphic belt; the roof pendants are crosscut by Upper Triassic granitic rocks of the Lee Vining intrusive epoch. A still later period of Early and Middle Jurassic regional deformation occurred along N. 30?-60? E. trends in upper Paleozoic rocks of the Calaveras Formation of the western metamorphic belt. A further period of deformation was the Late Jurassic Nevadan orogeny, which occurred along N. 20?_40? W. trends in Upper Jurassic rocks of the western metamorphic belt that are crosscut by Upper Jurassic granitic rocks of the Yosemite intrusive epoch

Global deglaciation and the re-appearance of microbial matground-dominated ecosystems in the late Paleozoic of Gondwana.

PubMed

Buatois, L A; Netto, R G; Gabriela Mángano, M; Carmona, N B

2013-07-01

The extensive matgrounds in Carboniferous-Permian open-marine deposits of western Argentina constitute an anachronistic facies, because with the onset of penetrative bioturbation during the early Paleozoic microbial mats essentially disappeared from these settings. Abundant microbially induced sedimentary structures in the Argentinean deposits are coincident with the disappearance of trace and body fossils in the succession and with a landward facies shift indicative of transgressive conditions. Deposits of the Late Carboniferous-Early Permian glacial event are well developed in adjacent basins in eastern Argentina, Brazil, South Africa and Antarctica, but do not occur in the western Andean basins of Argentina. However, the deglaciation phase is indirectly recorded in the studied region by a rapid rise in sea level referred to as the Stephanian-Asselian transgression. We suggest that an unusual release of meltwater during the final deglaciation episode of the Gondwana Ice Age may have dramatically freshened peri-Gondwanan seas, impacting negatively on coastal and shallow-marine benthic faunas. Suppression of bioturbation was therefore conducive to a brief re-appearance of matground-dominated ecosystems, reminiscent of those in the precambrian. Bioturbation is essential for ecosystem performance and plays a major role in ocean and sediment geochemistry. Accordingly, the decimation of the mixed layer during deglaciation in the Gondwana basins may have altered ecosystem functioning and geochemical cycling. © 2013 John Wiley & Sons Ltd.

A geochemical record of polycyclic aromatic hydrocarbons (PAHs) during the late Paleozoic Ice Age: The relationship between atmospheric pCO2, climate and fire.

NASA Astrophysics Data System (ADS)

Hren, M. T.; Harris, G.; Montanez, I. P.; DiMichele, W.; Eley, Y.; White, J. D.; Wilson, J. P.; McElwain, J.; Poulsen, C. J.

2017-12-01

The late Paleozoic Ice Age (LPIA) represents a dynamic period of widespread glacial/interglacial cycling as the earth underwent a major transition from an icehouse to greenhouse climate. During this transition period, pCO2 is shown to have varied by several hundred ppm and within the predicted range for anthropogenic change. Glacial/interglacial changes in atmospheric pCO2 during this time are associated with restructuring of tropical forests and carbon cycle dynamics. At present however, there is considerable debate over the potential hydrologic and fire-frequency feedbacks associated with this climatic variability. Polycyclic aromatic hydrocarbons (PAHs) are produced from the incomplete combustion of organic matter and are shown to be preserved over hundreds of millions of years. Thus, these organic compounds provide a potential record of the feedbacks between global biogeochemical systems and fire. We analyzed sedimentary organic matter from the Illinois Basin spanning the late Carboniferous glacial-interglacial cycles to assess the evolution of fire during this period. Our data show a decrease in the overall abundance of high molecular weight PAHs (HMW) from 312 to 304 Myr with significant variability that is coincident with the general timing of pCO2 cycling. Decreasing PAH abundance is also coincident with a proposed long-term change in pO2 and may reflect the influence of atmospheric oxygen in regulating fire occurrence and hydrologic cycling in tropical ecosystems in the late Carboniferous.

Late Leonardian plants from West Texas: The youngest Paleozoic plant megafossils in North America

USGS Publications Warehouse

Mamay, S.H.; Miller, J.M.; Rohr, D.M.

1984-01-01

Abundant Permian plant megafossils were discovered in the Del Norte Mountains of Brewster County, Trans-Pecos Texas. The flora is dominated by a new and distinctive type of gigantopteroid leaves. Marine invertebrates are closely associated, and this admixture of continental and marine fossils indicates a deltaic depositional setting, probably on the southern margin of the Permian Basin. Conodonts indicate correlation with the uppermost Leonardian Road Canyon Formation in the Glass Mountains. These are the youngest Paleozoic plant megafossils known in North America; they add an important paleontological element to the classic Permian area of this Continent.

A comparative study of diversification events: the early Paleozoic versus the Mesozoic

NASA Technical Reports Server (NTRS)

Erwin, D. H.; Valentine, J. W.; Sepkoski, J. J. Jr; Sepkoski JJ, J. r. (Principal Investigator)

1987-01-01

We compare two major long-term diversifications of marine animal families that began during periods of low diversity but produced strikingly different numbers of phyla, classes, and orders. The first is the early-Paleozoic diversification (late Vendian-Ordovician; 182 MY duration) and the other the Mesozoic phase of the post-Paleozoic diversification (183 MY duration). The earlier diversification was associated with a great burst of morphological invention producing many phyla, classes, and orders and displaying high per taxon rates of family origination. The later diversification lacked novel morphologies recognized as phyla and classes, produced fewer orders, and displayed lower per taxon rates of family appearances. The chief difference between the diversifications appears to be that the earlier one proceeded from relatively narrow portions of adaptive space, whereas the latter proceeded from species widely scattered among adaptive zones and representing a variety of body plans. This difference is believed to explain the major differences in the products of these great radiations. Our data support those models that hold that evolutionary opportunity is a major factor in the outcome of evolutionary processes.

Geochronology and geochemistry of late Paleozoic-early Mesozoic igneous rocks of the Erguna Massif, NE China: Implications for the early evolution of the Mongol-Okhotsk tectonic regime

NASA Astrophysics Data System (ADS)

Li, Yu; Xu, Wen-Liang; Wang, Feng; Tang, Jie; Zhao, Shuo; Guo, Peng

2017-08-01

We undertook geochemical and geochronological studies on late Paleozoic-early Mesozoic igneous rocks from the Erguna Massif with the aim of constraining the early evolution of the Mongol-Okhotsk tectonic regime. Zircon crystals from nine representative samples are euhedral-subhedral, display oscillatory growth zoning, and have Th/U values of 0.14-6.48, indicating a magmatic origin. U-Pb dating of zircon using SIMS and LA-ICP-MS indicates that these igneous rocks formed during the Late Devonian (∼365 Ma), late Carboniferous (∼303 Ma), late Permian (∼256 Ma), and Early-Middle Triassic (246-238 Ma). The Late Devonian rhyolites, together with coeval A-type granites, formed in an extensional environment related to the northwestwards subduction of the Heihe-Nenjiang oceanic plate. Their positive εHf(t) values (+8.4 to +14.4) and Hf two-stage model ages (TDM2 = 444-827 Ma) indicate they were derived from a newly accreted continental crustal source. The late Carboniferous granodiorites are geochemically similar to adakites, and their εHf(t) values (+10.4 to +12.3) and Hf two-stage model ages (TDM2 = 500-607 Ma) suggest they were sourced from thickened juvenile lower crustal material, this thickening may be related to the amalgamation of the Erguna-Xing'an and Songnen-Zhangguangcai Range massifs. Rocks of the late Permian to Middle Triassic suite comprise high-K calc-alkaline monzonites, quartz monzonites, granodiorites, and monzogranites. These rocks are relatively enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy rare earth elements and high field strength elements. They were emplaced, together with coeval porphyry-type ore deposits, along an active continental margin where the Mongol-Okhotsk oceanic plate was subducting beneath the Erguna Massif.

Reconstruction of an early Paleozoic continental margin based on the nature of protoliths in the Nome Complex, Seward Peninsula, Alaska

USGS Publications Warehouse

Till, Alison B.; Dumoulin, Julie A.; Ayuso, Robert A.; Aleinikoff, John N.; Amato, Jeffrey M.; Slack, John F.; Shanks, W.C. Pat

2014-01-01

The Nome Complex is a large metamorphic unit that sits along the southern boundary of the Arctic Alaska–Chukotka terrane, the largest of several micro continental fragments of uncertain origin located between the Siberian and Laurentian cratons. The Arctic Alaska–Chukotka terrane moved into its present position during the Mesozoic; its Mesozoic and older movements are central to reconstruction of Arctic tectonic history. Accurate representation of the Arctic Alaska–Chukotka terrane in reconstructions of Late Proterozoic and early Paleozoic paleogeography is hampered by the paucity of information available. Most of the Late Proterozoic to Paleozoic rocks in the Alaska–Chukotka terrane were penetratively deformed and recrystallized during the Mesozoic deformational events; primary features and relationships have been obliterated, and age control is sparse. We use a variety of geochemical, geochronologic, paleontologic, and geologic tools to read through penetrative deformation and reconstruct the protolith sequence of part of the Arctic Alaska–Chukotka terrane, the Nome Complex. We confirm that the protoliths of the Nome Complex were part of the same Late Proterozoic to Devonian continental margin as weakly deformed rocks in the southern and central part of the terrane, the Brooks Range. We show that the protoliths of the Nome Complex represent a carbonate platform (and related rocks) that underwent incipient rifting, probably during the Ordovician, and that the carbonate platform was overrun by an influx of siliciclastic detritus during the Devonian. During early phases of the transition to siliciclastic deposition, restricted basins formed that were the site of sedimentary exhalative base-metal sulfide deposition. Finally, we propose that most of the basement on which the largely Paleozoic sedimentary protolith was deposited was subducted during the Mesozoic.

Sequence and facies architecture of the upper Blackhawk Formation and the Lower Castlegate Sandstone (Upper Cretaceous), Book Cliffs, Utah, USA

NASA Astrophysics Data System (ADS)

Yoshida, S.

2000-11-01

High-frequency stratigraphic sequences that comprise the Desert Member of the Blackhawk Formation, the Lower Castlegate Sandstone, and the Buck Tongue in the Green River area of Utah display changes in sequence architecture from marine deposits to marginal marine deposits to an entirely nonmarine section. Facies and sequence architecture differ above and below the regionally extensive Castlegate sequence boundary, which separates two low-frequency (106-year cyclicity) sequences. Below this surface, high-frequency sequences are identified and interpreted as comprising the highstand systems tract of the low-frequency Blackhawk sequence. Each high-frequency sequence has a local incised valley system on top of the wave-dominated delta, and coastal plain to shallow marine deposits are preserved. Above the Castlegate sequence boundary, in contrast, a regionally extensive sheet sandstone of fluvial to estuarine origin with laterally continuous internal erosional surfaces occurs. These deposits above the Castlegate sequence boundary are interpreted as the late lowstand to early transgressive systems tracts of the low-frequency Castlegate sequence. The base-level changes that generated both the low- and high-frequency sequences are attributed to crustal response to fluctuations in compressive intraplate stress on two different time scales. The low-frequency stratigraphic sequences are attributed to changes in the long-term regional subsidence rate and regional tilting of foreland basin fill. High-frequency sequences probably reflect the response of anisotropic basement to tectonism. Sequence architecture changes rapidly across the faulted margin of the underlying Paleozoic Paradox Basin. The high-frequency sequences are deeply eroded and stack above the Paradox Basin, but display less relief and become conformable updip. These features indicate that the area above the Paradox Basin was more prone to vertical structural movements during formation of the Blackhawk

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

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

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

USGS Publications Warehouse

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

2003-01-01

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

Sandstone units of the Lee Formation and related strata in eastern Kentucky

USGS Publications Warehouse

Rice, Charles L.

1984-01-01

Most of the Cumberland Plateau region of southeastern Kentucky is underlain by thick sequences of quartzose sandstone which are assigned for the most part to the Lee Formation. Much new information has been gathered about the Lee and related strata as a result of the cooperative mapping program of the U. S. Geological Survey and the Kentucky Geological Survey between 1960 and 1978. This report summarizes the age, lithology, distribution, sedimentary structures, and stratigraphic relations of the sandstone units of the Lee within and between each of three major outcrop belts in Kentucky: Cumberland Mountain, Pine Mountain, and the Pottsville Escarpment area. The Lee Formation generally has been regarded as Early Pennsylvanian in age and separated from Mississippian strata in Kentucky by an unconformity. However, lithostratigraphic units included in the formation as presently defined are broadly time-transgressive and range in age from Late Mississippian in parts of the Cumberland Mountain outcrop belt to Middle Pennsylvanian in the Pottsville Escarpment area. Members of the Lee intertongue with and grade into the underlying Pennington Formation and overlying Breathitt Formation. Sandstone and conglomeratic sandstone members of the Lee of Mississippian age found only in parts of the Cumberland overthrust sheet are closely associated with marine rocks; Pennsylvanian members are mostly associated with continental coal-bearing strata. Sandstone members of the Lee are mostly quartz rich and range from more than 90 percent to more than 99 percent quartz. They are relatively coarse grained, commonly pebbly, and in places conglomeratic. The units are southwest-trending linear or broadly lobate bodies. The Lee Formation is as much as 1,500 ft thick in the type area in Cumberland Mountain where it has been divided into eight members. The Pinnacle Overlook, Chadwell, White Rocks Sandstone, Middlesboro, Bee Rock Sandstone, and Naese Sandstone Members are mostly quartzose

Sedimentology of the mid-Carboniferous fill of the Olta paleovalley, eastern Paganzo Basin, Argentina: Implications for glaciation and controls on diachronous deglaciation in western Gondwana during the late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

Moxness, Levi D.; Isbell, John L.; Pauls, Kathryn N.; Limarino, Carlos O.; Schencman, Jazmin

2018-07-01

Both global and regional climate drivers contributed to glaciation during the late Paleozoic Ice Age (LPIA). However, the transition from icehouse to greenhouse conditions was asynchronous across Gondwana suggesting that, in some cases, regional controls played a significant role in deglaciation. Of particular interest to understanding changing LPIA climatic conditions, is the eastern Paganzo Basin. This region was flanked by ice centers in the Precordilleran and Sierras Pampeanas regions of Argentina on the west, and major ice sheets in the Paraná, Chaco-Paraná, and Sauce Grande basins to the east, all of which resided between ∼40 and 65° S latitude. Hypotheses on the occurrence of ice in the eastern Paganzo Basin are based on interpretations of the narrow, steep-walled, Olta-Malanzán paleovalley as carved by an alpine glacier or by an outlet glacier draining an eastern ice sheet, and that glaciers deposited coarse clastics within the paleovalley. However, we found no evidence for glaciation. Rather, gravel from prograding alluvial fans/fan deltas and rock falls ponded drainage resulting in lacustrine activity in the eastern end of the valley. A transition from either subaerially or shallow subaqueously deposited sandstones to marine mudstones in the western end of the Olta paleovalley suggest a marine transgression, which, in turn, was overlain by deposits of prograding Gilbert-type deltas. Dropstones were from rock falls off valley walls and rafting by lake ice rather than from icebergs. Therefore, we conclude that the climate in western Argentina resulted from uplift induced glaciation in the Precordilleran region and along the western margin of the Paganzo Basin, and the occurrence of a precipitation shadow to the east. The disappearance of the western glaciers during the mid-Carboniferous, prior to deglaciation elsewhere at the same paleolatitude, resulted from a westward shift in the position of the active margin, collapse of the glaciated upland

Integrated interpretation of geophysical data of the Paleozoic structure in the northwestern part of the Siljan Ring impact crater, central Sweden

NASA Astrophysics Data System (ADS)

Muhamad, Harbe; Juhlin, Christopher; Malehmir, Alireza; Sopher, Daniel

2018-01-01

The Siljan Ring impact structure is the largest known impact structure in Europe and is Late Devonian in age. It contains a central uplift that is about 20-30 km in diameter and is surrounded by a ring-shaped depression. The Siljan area is one of the few areas in Sweden where the Paleozoic sequence has not been completely eroded, making it an important location for investigation of the geological and tectonic history of Baltica during the Paleozoic. The Paleozoic strata in this area also provide insight into the complex deformation processes associated with the impact. In this study we focus on the northwestern part of the Siljan Ring, close to the town of Orsa, with the main objective of characterizing the subsurface Paleozoic succession and uppermost Precambrian crystalline rocks along a series of seismic reflection profiles, some of which have not previously been published. We combine these seismic data with gravity and magnetic data and seismic traveltime tomography results to produce an integrated interpretation of the subsurface in the area. Our interpretation shows that the Paleozoic sequence in this area is of a relatively constant thickness, with a total thickness typically between 300 and 500 m. Faulting appears to be predominantly extensional, which we interpret to have occurred during the modification stage of the impact. Furthermore, based on the geophysical data in this area, we interpret that the impact related deformation to differ in magnitude and style from other parts of the Siljan Ring.

Late-Paleozoic-Mesozoic deformational and deformation related metamorphic structures of Kuznetsk-Altai region

NASA Astrophysics Data System (ADS)

Zinoviev, Sergei

2014-05-01

Kuznetsk-Altai region is a part of the Central Asian Orogenic Belt. The nature and formation mechanisms of the observed structure of Kuznetsk-Altai region are interpreted by the author as the consequence of convergence of Tuva-Mongolian and Junggar lithospheric block structures and energy of collision interaction between the blocks of crust in Late-Paleozoic-Mesozoic period. Tectonic zoning of Kuznetsk-Altai region is based on the principle of adequate description of geological medium (without methods of 'primary' state recovery). The initial indication of this convergence is the crust thickening in the zone of collision. On the surface the mechanisms of lateral compression form a regional elevation; with this elevation growth the 'mountain roots' start growing. With an approach of blocks an interblock elevation is divided into various fragments, and these fragments interact in the manner of collision. The physical expression of collision mechanisms are periodic pulses of seismic activity. The main tectonic consequence of the block convergence and collision of interblock units is formation of an ensemble of regional structures of the deformation type on the basis of previous 'pre-collision' geological substratum [Chikov et al., 2012]. This ensemble includes: 1) allochthonous and autochthonous blocks of weakly deformed substratum; 2) folded (folded-thrust) systems; 3) dynamic metamorphism zones of regional shears and main faults. Characteristic of the main structures includes: the position of sedimentary, magmatic and PT-metamorphic rocks, the degree of rock dynamometamorphism and variety rock body deformation, as well as the styles and concentrations of mechanic deformations. 1) block terranes have weakly elongated or isometric shape in plane, and they are the systems of block structures of pre-collision substratum separated by the younger zones of interblock deformations. They stand out among the main deformation systems, and the smallest are included into the

Depositional environment of the downdip Queen City (Eocene) Sandstone, Mestena Grande Field Area, Jim Hogg and Duval Counties, Texas

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

McCormack, J.

1994-09-01

The downdip Queen City sandstone interval in the Mestena Grande field area of the south Texas Gulf Coast basin comprises two sandstone depositional units, referred to in this paper as A Lobe and B Lobe. A total of 583 ft (179 m) of conventional core from 11 wells containing predominantly B Lobe deposits were examined macroscopically. The A Lobe is a thin (6-34 ft; 1.8-10.4 m) fine- to very fine-grained, mostly bioturbated, well-sorted sandstone. The B Lobe is composed of fine to very fine, well-sorted sandstone interbedded with siltstone and mudstone. The trace fossil assemblage of the B Lobe indicatesmore » that sediments were deposited in the cruziana ichnofacies. Trace fossils and authigenic minerals also suggest oxygen stratification during deposition. B Lobe contains five subunits, each up to 13.5 ft (4 m) net sand thickness. These units were deposited as part of a highstands systems tract during the early Lutetian Stage (lower middle Eocene). B Lobe is a primarily aggradational unit composed of storm-generated sandstone and heterolithic deposits of the lower shoreface to inner shelf environment. A Lobe is a coarsening upward unit and represents progradation of the shoreface during late highstand systems tract development. An interlobal mudstone, which separates the units, marks the transition from early to late highstand systems tract development.« less

The Boundary of Tectonic Units of the South China Continent in the Meso-Neoproterozoic - Early Paleozoic: Insights from Integrated Geophysical Study

NASA Astrophysics Data System (ADS)

Guo, L.; Gao, R.; Meng, X.; Zhang, J.; Wang, H.; Liu, Y.

2013-12-01

The South China continent (SCC), located in the transition zone of the Eurasia, India and Pacific plates, formed in the Meso-Neoproterozoic by collision of the Yangtze block and the Cathaysia block. However, the boundaries of the two blocks before the late Paleozoic (from Meso-Neoproterozoic to early Paleozoic) remain debated in the literature due to strong and complex tectonic and magmatic activities since then. The south of Jiangnan archicontinent is covered mostly by the thick strata since the late Paleozoic, the surface of which is widely covered by the vegetation. And the regional tectonic deformation is extremely complicated with few basal outcrops. For decades, a variety of geophysical detections have been performed in the SCC for understanding the deep structure and tectonic evolution, including deep seismic sounding (DSS) profiles, magnetotelluric sounding (MT) profiles, gravity and magnetic surveys and a small amount of deep seismic reflection profiles. However, due to the limitations of resolution and accuracy of the observed geophysical data in the past, especially short of the deep seismic reflection profiles to reveal fine lithosphere structure, different scientists presented various views on the division of tectonic units in the SCC. In quite recent years, the SinoProbe-02 project launched a long profile of geophysical detections across the two blocks in the SCC, including deep seismic reflection, DSS, MT, and broadband seismic observation, the resolution and accuracy of which had been improved greatly. These newly data will benefit better understanding the deep structure and tectonic evolution of the SCC. Here, we assembled high-resolution Bouguer gravity anomalies and aeromagnetic anomalies data in the SCC. The magnetic data were reduced to the pole by used a varying magnetic inclinations algorithm. We then performed anomaly separation and multi-scales lineation structure analysis on the gravity and RTP magnetic data, and then did 3D fusion

Late Paleozoic SEDEX deposits in South China formed in a carbonate platform at the northern margin of Gondwana

NASA Astrophysics Data System (ADS)

Qiu, Wenhong Johnson; Zhou, Mei-Fu; Liu, Zerui Ray

2018-05-01

SEDEX sulfide deposits hosted in black shale and carbonate are common in the South China Block. The Dajiangping pyrite deposit is the largest of these deposits and is made up of stratiform orebodies hosted in black shales. Sandstone interlayered with stratiform orebodies contains detrital zircon grains with the youngest ages of 429 Ma. Pyrite from the orebodies has a Re-Os isochron age of 389 ± 62 Ma, indicative of formation of the hosting strata and syngenetic pyrite ores in the mid-late Devonian. The hosting strata is a transgression sequence in a passive margin and composed of carbonaceous limestone in the lower part and black shales in the upper part. The ore-hosting black shales have high TOC (total organic carbon), Mo, As, Pb, Zn and Cd, indicating an anoxic-euxinic deep basin origin. The high redox proxies, V/(V + Ni) > 0.6 and V/Cr > 1, and the positive correlations of TOC with Mo and V in black shales are also consistent with an anoxic depositional environment. The Dajiangping deposit is located close to the NE-trending Wuchuan-Sihui fault, which was active during the Devonian. The mid-late Devonian mineralization age and the anoxic-euxinic deep basinal condition of this deposit thus imply that the formation of this deposit was causally linked to hydrothermal fluid exhalation in an anoxic fault-bounded basin that developed in a carbonate platform of the South China Block. The regional distribution of many Devonian, stratiform, carbonaceous sediment-hosted sulfide deposits along the NE-trending fault-bounded basins in South China, similar to the Dajiangping deposit, indicates that these deposits formed at a basin developed in the passive margin setting of the South China Block during the Devonian. This environment was caused by the break-up and northward migration of the South China Block from Gandwana.

Stratigraphy of Slick Rock district and vicinity, San Miguel and Dolores Counties, Colorado

USGS Publications Warehouse

Shawe, Daniel R.; Simmons, George C.; Archbold, Norbert L.

1968-01-01

The Slick Rock district covers about 570 square miles in western San Miguel and Dolores Counties, in southwestern Colorado. It is at the south edge of the salt-anticline region of southwestern Colorado and southeastern Utah and of the Uravan mineral belt.Deposition of Paleozoic sedimentary rocks in the district and vicinity was principally controlled by development of the Paradox Basin, and of Mesozoic rocks by development of a depositional basin farther west. The Paleozoic rocks generally are thickest at the northeast side of the Paradox Basin in a northwest- trending trough which seems to be a wide graben in Precambrian igneous and metamorphic basement rocks; Mesozoic rocks generally thicken westward and southwestward from the district.Sedimentary rocks rest on a Precambrian basement consisting of a variety of rocks, including granite and amphibolite. The surface of the Precambrian rocks is irregular and generally more than 2,000 feet below sea level and 7,000-11,000 feet below the ground surface. In the northern part of the district the Precambrian surface plunges abruptly northeastward into the trough occupying the northeast side of the Paradox Basin, and in the southern part it sags in a narrow northeasterly oriented trough. Deepening of both troughs, or crustal deformation in their vicinity, influenced sedimentation during much of late Paleozoic and Mesozoic time.The maximum total thickness of sedimentary rocks underlying the district is 13,000 feet, and prior to extensive erosion in the late Tertiary and the Quaternary it may have been as much as about 18,000 feet. The lower 5,000 feet or more of the sequence of sedimentary rocks consists of arenaceous strata of early Paleozoic age overlain by dominantly marine carbonate rocks and evaporite beds interbedded with lesser amounts of clastic sediments of late Paleozoic age. Overlying these rocks is about 4,500 feet of terrestrial clastic sediments, dominantly sandstone with lesser amounts of shale, mudstone

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

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

Growth habit of the late Paleozoic rhizomorphic tree-lycopsid family Diaphorodendraceae: phylogenetic, evolutionary, and paleoecological significance.

PubMed

Dimichele, William A; Elrick, Scott D; Bateman, Richard M

2013-08-01

Rhizomorphic lycopsids evolved the tree habit independently of all other land plants. Newly discovered specimens allow radical revision of our understanding of the growth architectures of the extinct Paleozoic sister-genera Synchysidendron and Diaphorodendron. Detailed descriptions of six remarkable adpression specimens from the Pennsylvanian of the USA and three casts from the late Mississippian of Scotland are used to revise and reanalyze a previously published morphological cladistic matrix and to reinterpret their remarkable growth forms. Contrary to previous assertions, Synchysidendron resembled Diaphorodendron in having a distinct and relatively complex growth habit that emphasized serially homologous, closely spaced, deciduous lateral branches at the expense of reduced monocarpic crown branches. Lateral branches originated through several strongly anisotomous dichotomies before producing during extended periods large numbers of Achlamydocarpon strobili. The comparatively large diameter of abscission scars remaining on the main trunk and the emergence of branches above the horizontal plane suggest that the lateral branch systems were robust. Lateral branches were borne in two opposite rows on the main trunk and continued upward into an isotomously branched, determinate crown; their striking distichous arrangement caused preferred orientation of fallen trunks on bedding planes. This discovery identifies the plagiotropic growth habit, dominated by serial lateral branches, as ubiquitous in the Diaphorodendraceae and also as unequivocally primitive within Isoetales s.l., a conclusion supported by both the revised morphological cladistic analysis and relative first appearances of taxa in the fossil record. Previously assumed complete homology between crown branching in Lepidodendraceae and that of all earlier-divergent genera requires reassessment. Saltational phenotypic transitions via modification of key developmental switches remains the most credible

Factors controlling reservoir quality in tertiary sandstones and their significance to geopressured geothermal production. Annual report, May 1, 1979-May 31, 1980

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

Loucks, R.G.; Richmann, D.L.; Milliken, K.L.

1980-07-01

Differing extents of diagenetic modification is the factor primarily responsible for contrasting regional reservoir quality of Tertiary sandstones from the Upper and Lower Texas Gulf Coast. Detailed comparison of Frio sandstones from the Chocolate Bayou/Danbury Dome area, Brazoria County, and Vicksburg sandstones from the McAllen Ranch Field area, Hidalgo County, reveals that extent of diagenetic modification is most strongly influenced by (1) detrital mineralogy and (2) regional geothermal gradients. Vicksburg sandstones from the McAllen Ranch Field area are less stable, chemically and mechanically, than Frio sandstones from the Chocolate Bayou/Danbury dome area. Vicksburg sandstones are mineralogically immature and contain greatermore » proportions of feldspars and rock fragments than do Frio sandstones. Thr reactive detrital assemblage of Vicksubrg sandstones is highly susceptible to diagenetic modification. Susceptibility is enhanced by higher than normal geothermal gradients in the McAllen Ranch Field area. Thus, consolidation of Vicksburg sandstones began at shallower depth of burial and precipitation of authigenic phases (especially calcite) was more pervasive than in Frio sandstones. Moreover, the late-stage episode of ferroan calcite precipitation that occluded most secondary porosity in Vicksburg sandstones did not occur significantly in Frio sandstones. Therefore, regional reservoir quality of Frio sandstones from Brazoria County is far better than that characterizing Vicksburg sandstones from Hidalgo County, especially at depths suitable for geopressured geothermal energy production.« less

Paleozoic oil/gas shale reservoirs in southern Tunisia: An overview

NASA Astrophysics Data System (ADS)

Soua, Mohamed

2014-12-01

During these last years, considerable attention has been given to unconventional oil and gas shale in northern Africa where the most productive Paleozoic basins are located (e.g. Berkine, Illizi, Kufra, Murzuk, Tindouf, Ahnet, Oued Mya, Mouydir, etc.). In most petroleum systems, which characterize these basins, the Silurian played the main role in hydrocarbon generation with two main 'hot' shale levels distributed in different locations (basins) and their deposition was restricted to the Rhuddanian (Lllandovery: early Silurian) and the Ludlow-Pridoli (late Silurian). A third major hot shale level had been identified in the Frasnian (Upper Devonian). Southern Tunisia is characterized by three main Paleozoic sedimentary basins, which are from North to South, the southern Chotts, Jeffara and Berkine Basin. They are separated by a major roughly E-W trending lower Paleozoic structural high, which encompass the Mehrez-Oued Hamous uplift to the West (Algeria) and the Nefusa uplift to the East (Libya), passing by the Touggourt-Talemzane-PGA-Bou Namcha (TTPB) structure close to southern Tunisia. The forementioned major source rocks in southern Tunisia are defined by hot shales with elevated Gamma ray values often exceeding 1400 API (in Hayatt-1 well), deposited in deep water environments during short lived (c. 2 Ma) periods of anoxia. In the course of this review, thickness, distribution and maturity maps have been established for each hot shale level using data for more than 70 wells located in both Tunisia and Algeria. Mineralogical modeling was achieved using Spectral Gamma Ray data (U, Th, K), SopectroLith logs (to acquire data for Fe, Si and Ti) and Elemental Capture Spectroscopy (ECS). The latter technique provided data for quartz, pyrite, carbonate, clay and Sulfur. In addition to this, the Gamma Ray (GR), Neutron Porosity (ΦN), deep Resistivity (Rt) and Bulk Density (ρb) logs were used to model bulk mineralogy and lithology. Biostratigraphic and complete

Floral responses to the Late Paleozoic deglaciation

NASA Astrophysics Data System (ADS)

Looy, C. V.; DiMichele, W. A.

2011-12-01

The current human-induced thawing of ice house Earth prompts the careful examination of similar earlier events and their biotic consequences. The most recent full transition from a cool earth to a warm world took place in the Early to Middle Permian. Against a background of global warming, plant communities were affected globally resulting in migrations, extinctions and changed evolutionary patterns as a response to the environmental changes. The collapse of the southern hemisphere ice-sheets resulted in significant changes, not just at higher latitudes, but also in the tropics where the rainfall regime changed from seasonally dry to seasonally wet. In the Early Permian tropics - in areas where net sedimentation facilitates fossilization, to be more specific - vegetation rich in walchian conifers began to replace the spore plants and seed ferns that previously dominated the Late Pennsylvanian wetlands. The replacing drier floras probably lived in the basinal lowlands as well, but episodically at the drier times of climate cycles. New finds within the tropics of latest Early to Middle Permian-age, in particular from north-central Texas, indicate the existence of floras which were adapted to even more extended periods of drought. These were populated by the more derived voltzian conifers and other seed plants, such as cycads. Surprisingly, the clades in these floras were until recently only known from the tens-of-millions-of-years younger Late Permian and Early Mesozoic, where they were the dominant forms. These occurrences demonstrate that even more derived groups were already in existence and well differentiated by the Early Permian, outside the window of preservation. This pattern of change in conifers and their communities from north-central Texas is unique in that it represents the best documented record in the Phanerozoic of terrestrial ecosystem response to a change from a global cool-mode to warm-mode Earth. Conifers serve as "marker plants" for the

Pacing of Paleozoic macroevolutionary rates by Milankovitch grand cycles.

PubMed

Crampton, James S; Meyers, Stephen R; Cooper, Roger A; Sadler, Peter M; Foote, Michael; Harte, David

2018-05-29

Periodic fluctuations in past biodiversity, speciation, and extinction have been proposed, with extremely long periods ranging from 26 to 62 million years, although forcing mechanisms remain speculative. In contrast, well-understood periodic Milankovitch climate forcing represents a viable driver for macroevolutionary fluctuations, although little evidence for such fluctuation exists except during the Late Cenozoic. The reality, magnitude, and drivers of periodic fluctuations in macroevolutionary rates are of interest given long-standing debate surrounding the relative roles of intrinsic biotic interactions vs. extrinsic environmental factors as drivers of biodiversity change. Here, we show that, over a time span of 60 million years, between 9 and 16% of the variance in biological turnover (i.e., speciation probability plus species extinction probability) in a major Early Paleozoic zooplankton group, the graptoloids, can be explained by long-period astronomical cycles (Milankovitch "grand cycles") associated with Earth's orbital eccentricity (2.6 million years) and obliquity (1.3 million years). These grand cycles modulate climate variability, alternating times of relative stability in the environment with times of maximum volatility. We infer that these cycles influenced graptolite speciation and extinction through climate-driven changes to oceanic circulation and structure. Our results confirm the existence of Milankovitch grand cycles in the Early Paleozoic Era and show that known processes related to the mechanics of the Solar System were shaping marine macroevolutionary rates comparatively early in the history of complex life. We present an application of hidden Markov models to macroevolutionary time series and protocols for the evaluation of statistical significance in spectral analysis.

New isotopic evidence for the origin of groundwater from the Nubian Sandstone Aquifer in the Negev, Israel

USGS Publications Warehouse

Vengosh, A.; Hening, S.; Ganor, J.; Mayer, B.; Weyhenmeyer, C.E.; Bullen, T.D.; Paytan, A.

2007-01-01

SO4-rich groundwater from the underlying Jurassic aquifer contributes significantly to the salt budget of the Nubian Sandstone aquifer. The unique chemical and isotopic composition of the Jurassic groundwater (??34SSO4 ??? +14???; ??18OSO4 ??? 14???; 87Sr/86Sr ???0.70764) is interpreted as reflecting dissolution of Late Triassic marine gypsum deposits. In the southern Arava Valley the authors postulate that SO4-rich groundwater with distinctively high Br/Cl (3 ?? 10-3) low 87Sr/86Sr (0.70734), and high ??34SSO4 values (+15???) is derived from mixing with underlying brines from the Paleozoic units. The radiocarbon measurements reveal low 14C activities (0.2-5.8 pmc) in both the northeastern Negev and southern Arava Valley. Taking into account dissolution of carbonate rocks and bacterial SO4 reduction in the unconfined area, estimated mean residence times of groundwater in the confined zone in the northeastern Negev are on the order of 21-38 ka, which suggests recharge predominantly during the last glacial period. The 14C signal in groundwater from the southern Arava Valley is equally low but due to evidence for mixing with external water sources the residence time estimates are questionable. ?? 2007 Elsevier Ltd. All rights reserved.

Blueschist metamorphism and its tectonic implication of Late Paleozoic-Early Mesozoic metabasites in the mélange zones, central Inner Mongolia, China

NASA Astrophysics Data System (ADS)

Zhang, Jinrui; Wei, Chunjing; Chu, Hang

2015-01-01

Blueschists in central Inner Mongolia are distributed as layers and blocks in mélanges including the southern zone in Ondor Sum area and the northern zone in Manghete and Naomuhunni areas. They have been attributed to the subduction of Early Paleozoic oceanic crust. Blueschists from Ondor Sum and Naomuhunni are characterized by occurrence of sodic amphibole coexisting with epidote, albite, chlorite, calcic amphibole (in Ondor Sum) and muscovite (in Naomuhunni). Blueschists in Manghete contain porphyroblastic albite with inclusions of garnet and epidote in a matrix dominated by calcic-sodic amphibole, epidote, chlorite, albite and muscovite. Phase equilibria modeling for three blueschist samples using pseudosection suggest that the AlM2 contents in sodic amphibole can be used as a good barometer in the limited assemblage involving sodic amphibole + actinolite + epidote + chlorite + albite + quartz under pressures <4-6 kbar, while this barometer is largely influenced by temperature and bulk Fe2O3 contents in the actinolite-absent assemblage sodic amphibole + epidote + chlorite + albite + quartz of higher pressure and the AlM2 contents are not pressure-controlled in the albite-absent assemblage sodic amphibole + epidote + chlorite + quartz under pressures > 7-10 kbar. In the sodic amphibole-bearing assemblages, the NaM4 contents in sodic amphibole mainly decrease as temperature rises, being a potential thermometry. The calculated pseudosections constrain the P-T conditions of blueschists to be 3.2-4.2 kbar/355-415 °C in Ondor Sum, 8.2-9.0 kbar/455 °C-495 °C in Manghete and 6.6-8.1 kbar/420-470 °C in Naomuhunni. These P-T estimates indicate a rather high geothermal gradient of 18-25 °C/km for the blueschist metamorphism, being of intermediate P/T facies series. Available zircon U-Pb age data suggests that the protoliths of blueschists were formed later than Late Paleozoic-Early Mesozoic and metamorphosed soon afterwards. An alternative interpretation for the

Origin and development of plains-type folds in the mid-continent (United States) during the late Paleozoic

USGS Publications Warehouse

Merriam, D.F.

2005-01-01

Plains-type folds are local, subtle anticlines formed in the thin sedimentary package overlying a shallow, crystalline basement on the craton. They are small in areal extent (usually less than 1-3 km 2 [0.4-1.2 mi2]), and their amplitude increases with depth (usually tens of meters), which is mainly the result of differential compaction of sediments (usually clastic units) over tilted, rigid, basement fault blocks. The development of these structural features by continuous but intermittent movement of the basement fault blocks in the late Paleozoic in the United States mid-continent is substantiated by a record of stratigraphic and sedimentological evidence. The recurrent structural movement, which reflects adjustment to external stresses, is expressed by the change in thickness of stratigraphic units over the crest of the fold compared to the flanks. By plotting the change in thickness for different stratigraphic units of anticlines on different fault blocks, it is possible to determine the timing of movement of the blocks that reflect structural adjustment. These readjustments are confirmed by sedimentological evidence, such as convolute, soft-sediment deformation features and small intraformational faults. The stratigraphic interval change in thickness for numerous structures in the Cherokee, Forest City, and Salina basins and on the Nemaha anticline of the mid-continent United States was determined and compared for location and timing of the adjustments. Most of the adjustment occurred during and after time of deposition of the Permian-Pennsylvanian clastic units, which, in turn, reflect tectonic disturbance in adjacent areas, and the largest amount of movement on the plains-type structures occurred on those nearest and semiparallel to major positive features, such as the Nemaha anticline. Depending on the time of origin and development of plains-type folds, they may control the entrapment and occurrence of oil and gas. Copyright ??2005. The American

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

USGS Publications Warehouse

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

2000-01-01

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

A unique ore-placer cluster with high-Hg gold mineralization in the Amur region (Russia)

NASA Astrophysics Data System (ADS)

Stepanov, V. A.; Moyseenko, V. G.; Melnikov, A. V.

2017-02-01

This work presents the geological structure and a description of gold-ore manifestations and gold placers in the Un'ya-Bom ore-placer cluster of the Amur gold-bearing province. The host rocks are Late Paleozoic and Mesozoic black-shale formations. Intrusive formations are rare. The sublatitudinal Un'ya thrust fault, along which Paleozoic sandstones overlap Mesozoic flyschoid deposits, is regarded as an orecontrolling structure. Gold-quartz and low-sulfide ores are confined to quartz-vein zones. Ore minerals are arsenopyrite, scheelite, ferberite, galena, and native gold. Gold-ore manifestations and placers contain high-Hg native gold. The high Hg content in native gold is explained by the occurrence of the eroded frontal part of the gold-ore pipe in the ore cluster, a source of native gold.

Assessing processes and timescales of sandstone 'peak forest' formation at Wulingyuan (Hunan, China)

NASA Astrophysics Data System (ADS)

Fink, David; May, Henne; Huang, He-quing; Fujioka, Toshiyuki; Wray, Robert

2013-04-01

Sandstone landscapes around the globe exhibit a surprising variety in terms of their landforms and formative processes. Ultimately, this reflects the wide range of geomorphic controls that dominate on regional scales, such as lithology, physical and chemical weathering, tectonics, and climate . At Wulingyuan, Hunan Province, China, a unique landscape has developed in Devonian sandstone over an area of ~400 km2, the "Wulingyuan peak forest", which is characterized by sheer vertical sandstone pillars over 3000 m in relief, overlayed with a substructure of peaks and walls of up to 350 m height. Due to these spectacular features, the area has become a major tourist attraction, and has recently been declared an UNESCO Global Geopark. Uplift, a densely spaced joint pattern, and the uniformity of sandstone beds have been suggested as major prerequisites for the formation and preservation of the unique morphology around Wulingyuan. We aim to investigate the underlying processes and controls responsible for the "peak forest" by determining a chronological framework for its age, rate of formation and rates of surface erosion. The initiation of uplift ~ 1 Ma ago and subsequent stepwise evolution of the "peak forest" has been inferred from cave sediments and surrounding alluvial terraces. No direct information, however, is available on the shorter-term evolution of the vertical sandstone walls, peaks and pillars. In this study , we (i) consider sampling strategies for applying surface exposure dating (SED) in this challenging morphological setting. (ii) present some first results, and (iii) discuss their significance in providing first estimates on rates of catchment-wide denudation, weathering, retreat of the vertical sandstone walls, and bedrock incision. In combination with a GIS-based assessment of sediment volumes stored in and eroded from the catchment, our data will help to elucidate the relative roles of fluvial, mass-wasting, and weathering processes in the longer

Paleozoic to early Cenozoic cooling and exhumation of the basement underlying the eastern Puna plateau margin prior to plateau growth

NASA Astrophysics Data System (ADS)

Insel, N.; Grove, M.; Haschke, M.; Barnes, J. B.; Schmitt, A. K.; Strecker, M. R.

2012-12-01

Constraining the pre-Neogene history of the Puna plateau is crucial for establishing the initial conditions that attended the early stage evolution of the southern extent of the Andean plateau. We apply high- to low-temperature thermochronology data from plutonic rocks in northwestern Argentina to quantify the Paleozoic, Mesozoic and early Tertiary cooling history of the Andean crust. U-Pb crystallization ages of zircons indicate that pluton intrusion occurred during the early mid-Ordovician (490-470 Ma) and the late Jurassic (160-150 Ma). Lower-temperature cooling histories from 40Ar/39Ar analyses of K-feldspar vary substantially. Basement rocks underlying the western Puna resided at temperatures below 200°C (<6 km depth) since the Devonian (˜400 Ma). In contrast, basement rocks underlying the southeastern Puna were hotter (˜200-300°C) throughout the Paleozoic and Jurassic and cooled to temperatures of <200°C by ˜120 Ma. The southeastern Puna basement records a rapid cooling phase coeval with active extension of the Cretaceous Salta rift at ˜160-100 Ma that we associate with tectonic faulting and lithospheric thinning. The northeastern Puna experienced protracted cooling until the late Cretaceous with temperatures <200°C during the Paleocene. Higher cooling rates between 78 and 55 Ma are associated with thermal subsidence during the postrift stage of the Salta rift and/or shortening-related flexural subsidence. Accelerated cooling and deformation during the Eocene was focused within a narrow zone along the eastern Puna/Eastern Cordillera transition that coincides with Paleozoic/Mesozoic structural and thermal boundaries. Our results constrain regional erosion-induced cooling throughout the Cenozoic to have been less than ˜150°C, which implies total Cenozoic denudation of <6-4 km.

Volcanic Debris Flows of the Latest Paleozoic Arbasay Formation: Geomorphological Characters and Paleoenvironment Reconstruction of Northern Tian Shan, NW China

NASA Astrophysics Data System (ADS)

Yang, W.; Liu, D.; Guo, Z.

2015-12-01

Texturally well-preserved volcanic debris flows (also called lahars) are exposed in the Latest Paleozoic Arbasay Formation, Northern Tian Shan. LA-ICP-MS zircon dating of the intercalated fallout tuff sample provided an age of 314.4±3.4 Ma (MSWD=1.6), suggesting they were deposited at Latest Carboniferous. The lahars consist primarily of two lithofacies: massive, poorly lithified diamictites and stratified, moderately lithified gravelly sandstones. The diamictites can be generally divided into two subfacies, i.e., the matrix-supported and the clast-supported diamictites. Most diamictites are structureless and nongraded. They are thick in beds and contain large clasts up to 3 m in dimension. The gravelly sandstones display much finer particle size and have wedge or lenticular geometries. Large clasts are absent within them and the sorting characters are much better than the diamictites. Despite the different size grading, the matrix and the clasts of the two lithofacies appear to be homogeneous. The matrix is generally sandy mudstone. The clasts comprise rhyolites, dacites, andesites, andesitic basalts and basalts, same to the co-existing volcanic rocks, suggesting they originate from the cognate volcanics. The disorganized diamictites are supposed to deposit from a turbulent flood or pyroclastic surge. The gravelly sandstone lithofacies are interpreted as sand-rich flood flows or hyperconcentrated flood flows during the waning stage of a mass-flow event. The overall characteristics of the deposits suggest a mass-flow dominated alluvial fan environment. It's noteable that several syn- sedimentary normal faults occurred within these lahar deposits, indicating that the Southern Junggar Basin was in an extensional regime during the lahars' deposition. Structure is dominated by normal faulting, allowing the existence of relatively small, highly compartmentalized depocenters. This is also supported by geochemistry and detrital zircon studies.

Humid to arid to subhumid vegetation shift on Pilliga Sandstone, Ulungra Springs, New South Wales

NASA Astrophysics Data System (ADS)

Dodson, J. R.; Wright, R. V. S.

1989-09-01

The Pilliga Sandstone region of the northwest slope of New South Wales has a natural vegetation cover of sclerophyllous relatively closed to open forests with a largely heathy understorey, and a warm, subhumid and continental climate. Pollen analysis of spring-fed deposits gives a vegetation history extending from at least 30,000 yr B.P. to the late Holocene. Tree pollen became scarce after about 25,000 yr B.P. and an assemblage dominated by Chenopodiaceae, Liguliflorae, Tubuliflorae, and probably Poaceae developed. No similar assemblage is known from present pollen rain studies carried out in Australia. However, it clearly represents a treeless open shrub-steppe formation and therefore an arid or semiarid environment. The site thus provides evidence of an eastward late Pleistocene extension of the arid zone in Australia, and is the first full-glacial vegetation record between 20° and 35° latitude in Australia. The present vegetation cover did not become reestablished until the beginning of the Holocene, which raises questions about the form in which Pilliga Sandstone vegetation survived full-glacial conditions.

Regional variations in provenance and abundance of ice-rafted clasts in Arctic Ocean sediments: Implications for the configuration of late Quaternary oceanic and atmospheric circulation in the Arctic

USGS Publications Warehouse

Phillips, R.L.; Grantz, A.

2001-01-01

The composition and distribution of ice-rafted glacial erratics in late Quaternary sediments define the major current systems of the Arctic Ocean and identify two distinct continental sources for the erratics. In the southern Amerasia basin up to 70% of the erratics are dolostones and limestones (the Amerasia suite) that originated in the carbonate-rich Paleozoic terranes of the Canadian Arctic Islands. These clasts reached the Arctic Ocean in glaciers and were ice-rafted to the core sites in the clockwise Beaufort Gyre. The concentration of erratics decreases northward by 98% along the trend of the gyre from southeastern Canada basin to Makarov basin. The concentration of erratics then triples across the Makarov basin flank of Lomonosov Ridge and siltstone, sandstone and siliceous clasts become dominant in cores from the ridge and the Eurasia basin (the Eurasia suite). The bedrock source for the siltstone and sandstone clasts is uncertain, but bedrock distribution and the distribution of glaciation in northern Eurasia suggest the Taymyr Peninsula-Kara Sea regions. The pattern of clast distribution in the Arctic Ocean sediments and the sharp northward decrease in concentration of clasts of Canadian Arctic Island provenance in the Amerasia basin support the conclusion that the modem circulation pattern of the Arctic Ocean, with the Beaufort Gyre dominant in the Amerasia basin and the Transpolar drift dominant in the Eurasia basin, has controlled both sea-ice and glacial iceberg drift in the Arctic Ocean during interglacial intervals since at least the late Pleistocene. The abruptness of the change in both clast composition and concentration on the Makarov basin flank of Lomonosov Ridge also suggests that the boundary between the Beaufort Gyre and the Transpolar Drift has been relatively stable during interglacials since that time. Because the Beaufort Gyre is wind-driven our data, in conjunction with the westerly directed orientation of sand dunes that formed during

Two contrasting late Paleozoic magmatic episodes in the northwestern Chinese Tianshan Belt, NW China: Implication for tectonic transition from plate convergence to intra-plate adjustment during accretionary orogenesis

NASA Astrophysics Data System (ADS)

Wang, Xiangsong; Cai, Keda; Sun, Min; Xiao, Wenjiao; Xia, Xiaoping; Wan, Bo; Bao, Zihe; Wang, Yannan

2018-03-01

Late Carboniferous to Early Permian is a critical period for the final amalgamation of the Central Asian Orogenic Belt (CAOB). However, as most of the accreted terranes of the CAOB are unclear in tectonic nature and origin, the timing and processes of their mutual amalgamation have been poorly constrained. To understand assembly of the West Junggar Terrane with the Yili Block, a suite of the late Paleozoic magmatic rocks, including ignimbrite, rhyolite and granite, in northwestern Chinese Tianshan Belt were studied for their petrogenesis and tectonic implications. Our new results of secondary ion mass spectrometry (SIMS) zircon U-Pb dating reveal two separate magmatic episodes, ca. 300 Ma volcanism (ignimbrite and rhyolite) and ca. 288 Ma plutonsim (biotite granite). Geochemically, for the ca. 300 Ma volcanism, the ignimbrites have low SiO2 (65.8-71.5 wt.%) and Mg# (6-13) values, and exhibit arc affinity with significantly enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE) such as Nb, Ta and Ti. The whole-rock εNd(t) and zircon εHf(t) values range from +6.9 to +7.0 and +9.9 to +14.1 respectively, indicating a juvenile basaltic lower crustal origin. Rhyolites have slightly high SiO2 (72.7-74.0 wt.%) and K2O (3.86-4.53 wt.%) contents, high zircon δ18O (11.67-13.23‰) values, and low whole-rock εNd(t) (+2.9 to +3.8) and zircon εHf(t) (+2.8 to +10.0) values, which may suggest sediment involvements during magma generation. In contrast, for the ca. 288 Ma plutonism, the biotite granites have obviously higher SiO2 (74.7-75.5 wt.%) contents and whole-rock εNd(t) (+7.7 to +8.8), zircon εHf(t) (+9.8 to +12.7), and lower zircon δ18O (5.99-6.84‰) values, than those of the ca. 300 Ma volcanic rocks, which are consistent with signatures of juvenile magma source. According to our estimates of zircon saturation temperatures, together with their contrasting genesis, we attribute the formation of ca. 300 Ma high

Late Proterozoic-Paleozoic evolution of the Arctic Alaska-Chukotka terrane based on U-Pb igneous and detrital zircon ages: Implications for Neoproterozoic paleogeographic reconstructions

USGS Publications Warehouse

Amato, J.M.; Toro, J.; Miller, E.L.; Gehrels, G.E.; Farmer, G.L.; Gottlieb, E.S.; Till, A.B.

2009-01-01

The Seward Peninsula of northwestern Alaska is part of the Arctic Alaska-Chukotka terrane, a crustal fragment exotic to western Laurentia with an uncertain origin and pre-Mesozoic evolution. U-Pb zircon geochronology on deformed igneous rocks reveals a previously unknown intermediate-felsic volcanic event at 870 Ma, coeval with rift-related magmatism associated with early breakup of eastern Rodinia. Orthogneiss bodies on Seward Peninsula yielded numerous 680 Ma U-Pb ages. The Arctic Alaska-Chukotka terrane has pre-Neoproterozoic basement based on Mesoproterozoic Nd model ages from both 870 Ma and 680 Ma igneous rocks, and detrital zircon ages between 2.0 and 1.0 Ga in overlying cover rocks. Small-volume magmatism occurred in Devonian time, based on U-Pb dating of granitic rocks. U-Pb dating of detrital zircons in 12 samples of metamorphosed Paleozoic siliciclastic cover rocks to this basement indicates that the dominant zircon age populations in the 934 zircons analyzed are found in the range 700-540 Ma, with prominent peaks at 720-660 Ma, 620-590 Ma, 560-510 Ma, 485 Ma, and 440-400 Ma. Devonian- and Pennsylvanian-age peaks are present in the samples with the youngest detrital zircons. These data show that the Seward Peninsula is exotic to western Laurentia because of the abundance of Neoproterozoic detrital zircons, which are rare or absent in Lower Paleozoic Cordilleran continental shelf rocks. Maximum depositional ages inferred from the youngest detrital age peaks include latest Proterozoic-Early Cambrian, Cambrian, Ordovician, Silurian, Devonian, and Pennsylvanian. These maximum depositional ages overlap with conodont ages reported from fossiliferous carbonate rocks on Seward Peninsula. The distinctive features of the Arctic Alaska-Chukotka terrane include Neoproterozoic felsic magmatic rocks intruding 2.0-1.1 Ga crust overlain by Paleozoic carbonate rocks and Paleozoic siliciclastic rocks with Neoproterozoic detrital zircons. The Neoproterozoic ages are

Sandstone dykes in siwalik sandstone-sedimentology and basin analysis-subansiri district (NEFA), Eastern Himalaya

NASA Astrophysics Data System (ADS)

Kumar, Surendar; Singh, Trilochan

1982-11-01

Sandstone dykes (including sills) of varied thickness and with tapering ends are present either transecting or (sills) parallel to bedding in the Siwalik sandstone of Arunachal Pradesh (NEFA), Eastern Himalaya. The different sedimentary and microstructural analyses show varied conditions of deposition with changing facies from fluvial channel, to alluvial fan, to coastal plain-fan delta. The non-marine and shallow marine environments are indicated by the presence of organised and disorganised gradation and the presence of sandstone dykes in the interface regions. The orientations of the longer axes of the conglomerate along with the sand bedding indicate palaeoflow.

Deposition of a saline giant in the Mississippian Windsor Group, Nova Scotia, and the nascent Late Paleozoic Ice Age

NASA Astrophysics Data System (ADS)

MacNeil, Laura A.; Pufahl, Peir K.; James, Noel P.

2018-01-01

Saline giants are vast marine evaporite deposits that currently have no modern analogues and remain one of the most enigmatic of chemical sedimentary rocks. The Mississippian Windsor Group (ca. 345 Ma), Maritimes Basin, Atlantic Canada is a saline giant that consists of two evaporite-rich sedimentary sequences that are subdivided into five subzones. Sequence 1 is composed almost entirely of thick halite belonging to Subzone A (Osagean). Sequence 2 is in unconformable contact and comprised of stacked carbonate-evaporite peritidal cycles of Subzones B through E (Meramecian). Subzone B, the focus of research herein, documents the transition from wholly evaporitic to open marine conditions and thus, preserves an exceptional window into the processes forming saline giants. Lithofacies stacking patterns in Subzone B reveal that higher-order fluctuations in relative sea level produced nine stacked parasequences interpreted to reflect high frequency glacioeustatic oscillations during the onset of the Late Paleozoic Ice Age. Each parasequence reflects progradation of intertidal and sabkha sediments over subtidal carbonate and evaporite deposits. Dissimilarities in cycle composition between sub-basins imply the development of contrasting brine chemistries from differing recharge rates with the open ocean. What the Windsor Group shows is that evaporite type is ostensibly linked to the amplitude and frequency of sea level rise and fall during deposition. True saline giants, like the basinwide evaporites of Sequence 1, apparently require low amplitude, long frequency changes in sea level to promote the development of stable brine pools that are only periodically recharged with seawater. By contrast, the high amplitude, short frequency glacioeustatic variability in sea level that controlled the accumulation of peritidal evaporites in Subzone B produce smaller, subeconomic deposits with more complex facies relationships.

A paleozoic pangaea.

PubMed

Boucot, A J; Gray, J

1983-11-11

Paleozoic paleogeographies should be consistent with all available, reliable data. However, comparison of three different Devonian paleogeographies that are based largely or wholly on the data of remanent magnetism show them to be inconsistent in many regards. When these three paleogeographies are provided with possible ocean surface current circulation patterns, and have added to them lithofacies and biogeographic data, they also are shown to be inconsistent with such data. A pangaeic reconstruction positioned in the Southern Hemisphere permits the lithofacies and biogeographical data to be reconciled in a plausible manner.

Constraints on Late Paleozoic Ocean Response to Climate Change Based on Brachiopod δ11B and 87Sr/86Sr

NASA Astrophysics Data System (ADS)

Legett, S. A.; Rasbury, T.; Grossman, E. L.; Hemming, G.

2017-12-01

In order to understand the possible effects of climate change on present day oceans, it is important to determine how marine systems responded to climate change in the past. This study uses δ11B values from well-preserved Carboniferous and Permian brachiopods as well as models to examine chemical trends in seawater and how these relate to long- and short-term climate changes. Our results show that δ11B rises rapidly going into the Carboniferous from a low of 10‰ to a high of 17‰ and remains relatively stable through the Carboniferous, despite the initiation of glaciation in the Mid Carboniferous. At the Carboniferous-Permian boundary, δ11B declines into the Early Permian before reaching a low at the Sakmarian. This decline in δ11B is coincident with the decrease in 87Sr/86Sr through this interval, which corresponds to evidence for aridity going into the Permian. We hypothesize that a reduction in silicate weathering drives an increase in atmospheric pCO2 and a subsequent lowering of ocean pH going into the Permian. This is consistent with our interpretation of the Carboniferous-Permian boundary, as a major mechanism for controlling seawater boron isotope composition is the adsorption of borate on clays, removing isotopically light boron and thus leaving seawater boron isotopically heavy. Therefore, at lower pH seawater should become isotopically lighter as this mechanism for removal is reduced. These hypotheses are supported by our initial modeling results of the B and Sr isotopic budgets of the ocean during the Late Paleozoic.

Exceptional marine sand bodies in the Paleozoic of Oklahoma

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

Fritz, R.D.; Kuykendall, M.D.; Hooker, E.O.

Of the wide variety of sandstone reservoirs in Oklahoma, the most unusual types of sand bodies are present in the Atokan Spiro Sandstone, Devonian Misener Sandstone, and Morrowan lower Morrow Sandstone. The common factors are that upon correlation and mapping these units are channel-like (fluvial-deltaic) in geometry, but from petrographic evidence are quartz-rich shallow-marine units, with the exclusion of intraclastic and diagenetic constituents. Stratigraphic mapping of the Spiro Sandstone of the Arkoma basin indicates two types of sand bodies: channel and sheet. The marine channel-like deposits, 10-150 ft thick, probably were deposited on a paleosurface produced by a pre-Atokan unconformity.more » Examination of cores and outcrop indicate that both the channel and sheet Spiro sands contain shallow-marine fossils, limestones, peloidal chamosite, burrows, and bioturbation, all indicative of a shallow-marine setting. The Misener Sandstone of north-central Oklahoma ranges from 10 to 100 ft thick with sharp boundaries. It was deposited in pre-Frisco/Woodford eroded paleochannels. Core evidence for shallow-marine deposition is glauconite, phosphatic fossils and clasts, burrows, and bioturbation. These were probably deposited in an embayed, estuary-like environment. The lower Morrow Sandstone of the Anadarko basin is similar in geometry, except that the sand bodies are multistoried and multilateral and do not appear to be associated with a regional unconformity. The lower Morrow sandstones, usually 30-60 ft thick. commonly are elongated and deposited parallel to the shoreline. Deposition is inferred to be shallow-marine from marine fossils and glauconite.« less

Paleozoic-Mesozoic boundary in the Berry Creek Quadrangle, northwestern Sierra Nevada, California

USGS Publications Warehouse

Hietanen, Anna Martta

1977-01-01

Structural and petrologic studies in the Berry Creek quadrangle at the north end of the western metamorphic belt of the Sierra Nevada have yielded new information that helps in distinguishing between the chemically similar Paleozoic and Mesozoic rocks. The distinguishing features are structural and textural and result from different degrees of deformation. Most Paleozoic rocks are strongly deformed and thoroughly recrystallized. Phenocrysts in meta volcanic rocks are granulated and drawn out into lenses that have sutured outlines. In contrast, the phenocrysts in the Mesozoic metavolcanic rocks show well-preserved straight crystal faces, are only slightly or not at all granulated, and contain fewer mineral inclusions than do those in the Paleozoic rocks. The groundmass in the Paleozoic rocks is recrystallized to a fairly coarse grained albite-epidote-amphibole-chlorite rock, whereas in the Mesozoic rocks the groundmass is a very fine grained feltlike mesh with only spotty occurrence of well-recrystallized finegrained albite-epidote-chlorite-actinolite rock. Primary minerals, such as augite, are locally preserved in the Mesozoic rocks but are altered to a mixture of amphibole, chlorite, and epidote in the Paleozoic rocks. In the contact aureoles of the plutons, and within the Big Bend fault zone, which crosses the area parallel to the structural trends, all rocks are thoroughly recrystallized and strongly deformed. Identification of the Paleozoic and Mesozoic rocks in these parts of the area was based on the continuity of the rock units in the field and on gradual changes in microscopic textures toward the plutons.

Structural styles of Paleozoic intracratonic fault reactivation: A case study of the Grays Point fault zone in southeastern Missouri, USA

USGS Publications Warehouse

Clendenin, C.W.; Diehl, S.F.

1999-01-01

A pronounced, subparallel set of northeast-striking faults occurs in southeastern Missouri, but little is known about these faults because of poor exposure. The Commerce fault system is the southernmost exposed fault system in this set and has an ancestry related to Reelfoot rift extension. Recent published work indicates that this fault system has a long history of reactivation. The northeast-striking Grays Point fault zone is a segment of the Commerce fault system and is well exposed along the southeast rim of an inactive quarry. Our mapping shows that the Grays Point fault zone also has a complex history of polyphase reactivation, involving three periods of Paleozoic reactivation that occurred in Late Ordovician, Devonian, and post-Mississippian. Each period is characterized by divergent, right-lateral oblique-slip faulting. Petrographic examination of sidwall rip-out clasts in calcite-filled faults associated with the Grays Point fault zone supports a minimum of three periods of right-lateral oblique-slip. The reported observations imply that a genetic link exists between intracratonic fault reactivation and strain produced by Paleozoic orogenies affecting the eastern margin of Laurentia (North America). Interpretation of this link indicate that right-lateral oblique-slip has occurred on all of the northeast-striking faults in southeastern Missouri as a result of strain influenced by the convergence directions of the different Paleozoic orogenies.

Geology and Ore Deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

USGS Publications Warehouse

Burbank, Wilbur Swett; Luedke, Robert G.

2008-01-01

The Uncompahgre mining district, part of the Ouray mining district, includes an area of about 15 square miles (mi2) on the northwestern flank of the San Juan Mountains in southwestern Colorado from which ores of gold, silver, copper, lead, and zinc have had a gross value of $14 to 15 million. Bedrock within the district ranges in age from Proterozoic to Cenozoic. The oldest or basement rocks, the Uncompahgre Formation of Proterozoic age, consist of metamorphic quartzite and slate and are exposed in a small erosional window in the southern part of the district. Overlying those rocks with a profound angular unconformity are Paleozoic marine sedimentary rocks consisting mostly of limestones and dolomites and some shale and sandstone that are assigned to the Elbert Formation and Ouray Limestone, both of Devonian age, and the Leadville Limestone of Mississippian age. These units are, in turn, overlain by rocks of marine transitional to continental origin that are assigned to the Molas and Hermosa Formations of Pennsylvanian age and the Cutler Formation of Permian age; these three formations are composed predominantly of conglomerates, sandstones, and shales that contain interbedded fossiliferous limestones within the lower two-thirds of the sequence. The overlying Mesozoic strata rest also on a pronounced angular unconformity upon the Paleozoic section. This thick Mesozoic section, of which much of the upper part was eroded before the region was covered by rocks of Tertiary age, consists of the Dolores Formation of Triassic age, the Entrada Sandstone, Wanakah Formation, and Morrison Formation all of Jurassic age, and the Dakota Sandstone and Mancos Shale of Cretaceous age. These strata dominantly consist of shales, mudstones, and sandstones and minor limestones, breccias, and conglomerates. In early Tertiary time the region was beveled by erosion and then covered by a thick deposit of volcanic rocks of mid-Tertiary age. These volcanic rocks, assigned to the San Juan

Provenance of upper Triassic sandstone, southwest Iberia (Alentejo and Algarve basins): tracing variability in the sources

NASA Astrophysics Data System (ADS)

Pereira, M. F.; Ribeiro, C.; Gama, C.; Drost, K.; Chichorro, M.; Vilallonga, F.; Hofmann, M.; Linnemann, U.

2017-01-01

Laser ablation ICP-MS U-Pb analyses have been conducted on detrital zircon of Upper Triassic sandstone from the Alentejo and Algarve basins in southwest Iberia. The predominance of Neoproterozoic, Devonian, Paleoproterozoic and Carboniferous detrital zircon ages confirms previous studies that indicate the locus of the sediment source of the late Triassic Alentejo Basin in the pre-Mesozoic basement of the South Portuguese and Ossa-Morena zones. Suitable sources for the Upper Triassic Algarve sandstone are the Upper Devonian-Lower Carboniferous of the South Portuguese Zone (Phyllite-Quartzite and Tercenas formations) and the Meguma Terrane (present-day in Nova Scotia). Spatial variations of the sediment sources of both Upper Triassic basins suggest a more complex history of drainage than previously documented involving other source rocks located outside present-day Iberia. The two Triassic basins were isolated from each other with the detrital transport being controlled by two independent drainage systems. This study is important for the reconstruction of the late Triassic paleogeography in a place where, later, the opening of the Central Atlantic Ocean took place separating Europe from North America.

Multidisciplinary studies on ancient sandstone quarries of Western Sardinia (Italy).

NASA Astrophysics Data System (ADS)

Grillo, Silvana Maria; Del Vais, Carla; Naitza, Stefano

2013-04-01

The ancient coastal quarries of Mediterranean are increasingly considered geosites of multidisciplinary relevance. They are sites of historical-archaeological interest that show ancient techniques of stone extraction; they are significant for cultural heritage conservation and restoration, as sources of the stones used in ancient buildings and monuments; they are sites of geological relevance, as often retain important stratigraphic sections; they are also useful markers of secular changes in the sea level. A multisciplinary study is in progress on the ancient quarries of the Sinis region (western Sardinia island), integrating archaeological, geological, minero-petrographical data. In Sardinia, coastal quarries have been established from Punic and Roman times. Many of them exploited Quaternary sediments along the southern and western coasts of the island. They consist of middle-late Pleistocene marine conglomerates and carbonate sandstones, and of coastal (aeolian) carbonate sandstones. Sandstone blocks of different sizes have been widely used in ancient cities for buildings, defensive works, harbours, etc. Three main areas of stone extraction (San Giovanni di Sinis, Punta Maimoni, Is Arutas) have been so far recognized in the Sinis. GIS-supported mapping and documentation of the sites includes their geology and stratigraphy, the extension and layout of the quarries, and an evaluation of volumes of extracted rocks. Documented archaeological evidences include ancient extraction fronts, spoil heaps, working areas, working traces in the old fronts, transport routes of blocks, and traces of loading facilities. The study is aimed at reconstructing the relationships of the quarries with the urban areas of Sinis, as the ancient Punic-Roman city of Tharros. Consequently, a minero-petrographical characterization (optical microscopy, XRD) is performed on sandstones sampled in each quarry, and in historical buildings in Tharros and other centres of the region (Cabras

Quartz cement in sandstones: a review

NASA Astrophysics Data System (ADS)

McBride, Earle F.

Quartz cement as syntaxial overgrowths is one of the two most abundant cements in sandstones. The main factors that control the amount of quartz cement in sandstones are: framework composition; residence time in the "silica mobility window"; and fluid composition, flow volume and pathways. Thus, the type of sedimentary basin in which a sand was deposited strongly controls the cementation process. Sandstones of rift basins (arkoses) and collision-margin basins (litharenites) generally have only a few percent quartz cement; quartzarenites and other quartzose sandstones of intracratonic, foreland and passive-margin basins have the most quartz cement. Clay and other mineral coatings on detrital quartz grains and entrapment of hydrocarbons in pores retard or prevent cementation by quartz, whereas extremely permeable sands that serve as major fluid conduits tend to sequester the greatest amounts of quartz cement. In rapidly subsiding basins, like the Gulf Coast and North Sea basins, most quartz cement is precipitated by cooling, ascending formation water at burial depths of several kilometers where temperatures range from 60° to 100° C. Cementation proceeds over millions of years, often under changing fluid compositions and temperatures. Sandstones with more than 10% imported quartz cement pose special problems of fluid flux and silica transport. If silica is transported entirely as H 4SiO 4, convective recycling of formation water seems to be essential to explain the volume of cement present in most sandstones. Precipitation from single-cycle, upward-migrating formation water is adequate to provide the volume of cement only if significant volumes of silica are transported in unidentified complexes. Modeling suggests that quartz cementation of sandstones in intracratonic basins is effected by advecting meteoric water, although independent petrographic, isotopic or fluid inclusion data are lacking. Silica for quartz cement comes from both shale and sandstone beds within

Three stages in the Late Paleozoic to Triassic magmatism of southwestern Gondwana, and the relationships with the volcanogenic events in coeval basins

NASA Astrophysics Data System (ADS)

Sato, Ana María; Llambías, Eduardo J.; Basei, Miguel A. S.; Castro, Carlos E.

2015-11-01

The intermediate to acid Choiyoi Magmatic Province is the most conspicuous feature along the Late Paleozic continental margin of southwestern Gondwana, and is generally regarded as the possible source for the widespread ash fall deposits interlayered with sedimentary sequences in the adjacent Gondwana basins. The Choiyoi magmatism is geologically constrained between the early Permian San Rafael orogenic phase and the Triassic extensional Huarpica phase in the region of Argentine Frontal Cordillera, Precordillera and San Rafael Block. In order to better assess the Choiyoi magmatism in Argentine Frontal Cordillera, we obtained 6 new LA-ICPMS U-Pb ages between 278.8 ± 3.4 Ma and 252.5 ± 1.9 Ma from plutonic rocks of the Colangüil Batholith and an associated volcanic rock. The global analysis of age data compiled from Chilean and Argentine Late Paleozoic to Triassic outcrops allows us to identify three stages of magmatism: (1) pre-Choiyoi orogenic magmatism, (2) Choiyoi magmatism (286-247 Ma), and (3) post-Choiyoi magmatism related to extensional tectonics. In the Choiyoi stage is there an eastward shift and expansion of the magmatism to the southeast, covering an extensive region that defines the Choiyoi magmatic province. On the basis of comparison with the ages from volcanogenic levels identified in the coeval Gondwana basins, we propose: (a) The pre-Choiyoi volcanism from the Paganzo basin (320-296 Ma) probably has a local source in addition to the Frontal Cordillera region. (b) The pre-Choiyoi and Choiyoi events identified in the Paraná basin (304-275 Ma) are likely to have their source in the Chilean Precordillera. (c) The early stage of the Choiyoi magmatism found in the Sauce Grande basin (284-281 Ma) may have come from the adjacent Las Matras to Chadileuvú blocks. (d) The pre-Choiyoi and Choiyoi events in the Karoo basins (302-253 Ma) include the longest Choiyoi interval, and as a whole bear the best resemblance to the age records along the Chilean and

Geochemistry and geochronology of the blueschist in the Heilongjiang Complex and its implications in the late Paleozoic tectonics of eastern NE China

NASA Astrophysics Data System (ADS)

Ge, Mao-hui; Zhang, Jin-jiang; Liu, Kai; Ling, Yi-yun; Wang, Meng; Wang, Jia-min

2016-09-01

The Paleozoic to early Mesozoic tectonic framework and evolution of Northeast China, especially the Jiamusi block and its related structural belts, are highly debated. In this paper, geochemical, geochronological and isotopic analyses were carried out on the blueschist in the Heilongjiang Complex to address these issues. The Heilongjiang Complex defines the suture belt between the Jiamusi block and the Songliao block in NE China, and the blueschist is a major composition for this complex, coexisting with mafic-ultramafic rocks, greenschist, quartzite and mica schist. The blueschist has a mineral association of sodic amphibole, epidote, chlorite, phengite, albite and quartz with accessory phases of apatite, titanite, zircon and ilmenite. Together with the lithological association, the major and trace element compositions present that the protoliths of the blueschist can be divided into the alkaline and tholeiitic basalts and have OIB affinities, formed in an ocean island setting, indicated by the (La/Yb) N values of 3.57 - 11.54, and the (La/Sm) N values of 0.69 - 3.64. The high and positive εNd (t) values of + 3.7 to + 9.0, and relative enrichment in Nb (vs. Th) and Ta (vs. U) show that both the alkaline and tholeiitic basalts may be derived from the asthenospheric mantle with insignificant crustal contamination. Magmatic zircons from the blueschist in Yilan area yield a 206Pb/238U age of 281 ± 3 Ma, interpreted as its protolithic age. The youngest ages of 200 Ma of the detrital zircons in the associated mica schist from Mudanjiang area place constraints on the timing of metamorphism for the blueschist. These indicate that a big ocean existed between the Jiamusi and Songliao blocks at least since the early Permian, and the blueschist formed since the late Triassic to late Jurassic by the subduction of this ocean. Such an ocean during the Permian - Jurassic is difficult to be interpreted by the tectonic evolution of the Paleo-Asian Ocean.

Inventory of Neoproterozoic and Paleozoic strata in Sonora, Mexico

USGS Publications Warehouse

Stewart, John H.; Poole, Forrest G.

2002-01-01

This compilation is an inventory of all known outcrops of Neoproterozoic and Paleozoic strata in Sonora, Mexico. We have not attempted an interpretation of the regional stratigraphic or structural setting of the strata. Brief summaries of the stratigraphic setting of the Sonora rocks are given in Poole and Hayes (1971), Rangin (1978), Stewart and others (1984, 1990), and Poole and Madrid (1986; 1988b). More specific information on the setting of strata of specific ages are given by Stewart and others (2002) for the Neoproterozoic and Cambrian; by Poole and others (1995a) for Ordovician shelf strata; by Poole and others (1995b) for Ordovician deep-water openbasin strata; by Poole and others (1997, 1998, 2000a) for Silurian strata; and by Poole and others (2000a) for Mississippian strata. Other reports that discuss regional aspects of Paleozoic stratigraphy include López-Ramos (1982), Peiffer-Rangin, (1979, 1988), Pérez-Ramos (1992), and Stewart and others (1997, 1999a). Structurally, the major Paleozoic feature of Sonora is the Sonora allochthon, consisting of deep-water (eugeoclinal) strata emplaced in the Permian over shelf (miogeoclinal) deposits (Poole and others, 1995a,b; Poole and Perry, 1997; 1998). The emplacement structure is generally considered to be a major Permian continental margin thrust fault that emplaced the deep-water rocks northward over shelf (miogeoclinal) deposits. An alternate interpretation has been presented by Stewart and others (2002). He proposed that the emplacement of the Sonora allochthon was along a major Permian transpressional structure that was primarily a strike-slip fault with only a minor thrust component . The Mojave-Sonora megashear has been proposed to disrupt Neoproterozoic and Paleozoic trends in Sonora. This feature is a hypothetical, left-lateral, northwest-striking fault extending across northern Sonora and the southwestern United States (Silver and Anderson, 1974; Anderson and Schmidt, 1983). It is proposed to have

Factors controlling localization of uranium deposits in the Dakota Sandstone, Gallup and Ambrosia Lake mining districts, McKinley County, New Mexico

USGS Publications Warehouse

Pierson, Charles Thomas; Green, Morris W.

1977-01-01

Geologic studies were made at all of the uranium mines and prospects in the Dakota Sandstone of Early(?) and Late Cretaceous age in the Gallup mining district, McKinley County, New Mexico. Dakota mines in the adjacent Ambrosia Lake mining district were visited briefly for comparative purposes. Mines in the eastern part of the Gallup district, and in the Ambrosia Lake district, are on the Chaco slope of the southern San Juan Basin in strata which dip gently northward toward the central part of the basin. Mines in the western part of the Gallup district are along the Gallup hogback (Nutria monocline) in strata which dip steeply westward into the Gallup sag. Geologic factors which controlled formation of the uranium deposits in the Dakota Sandstone are: (1) a source of uranium, believed to be uranium deposits of the underlying Morrison Formation of Late Jurassic age; (2) the accessibility to the Dakota of uranium-bearing solutions from the Morrison; (3) the presence in the Dakota of permeable sandstone beds overlain by impermeable carbonaceous shale beds; and (4) the occurrence within the permeable Dakota sandstone beds of carbonaceous reducing material as bedding-plane laminae, or as pockets of carbonaceous trash. Most of the Dakota uranium deposits are found in the lower part of the formation in marginal-marine distributary-channel sandstones which were deposited in the backshore environment. However, the Hogback no. 4 (Hyde) Mine (Gallup district) occurs in sandy paludal shale of the backshore environment, and another deposit, the Silver Spur (Ambrosia Lake district), is found in what is interpreted to be a massive beach or barrier-bar sandstone of the foreshore environment in the upper part of the Dakota. The sedimentary depositional environment most favorable for the accumulation of uranium is that of backshore areas lateral to main distributary channels, where levee, splay, and some distributary-channel sandstones intertongue with gray carbonaceous shales and

From success to persistence: Identifying an evolutionary regime shift in the diverse Paleozoic aquatic arthropod group Eurypterida, driven by the Devonian biotic crisis.

PubMed

Lamsdell, James C; Selden, Paul A

2017-01-01

Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic arthropod group, the Eurypterida. Using these data, we explore the group's transition from a successful, dynamic clade to a stagnant persistent lineage, pinpointing the Devonian as the period during which this evolutionary regime shift occurred. The late Devonian biotic crisis is potentially unique among the "Big Five" mass extinctions in exhibiting a drop in speciation rates rather than an increase in extinction. Our study reveals eurypterids show depressed speciation rates throughout the Devonian but no abnormal peaks in extinction. Loss of morphospace occupation is random across all Paleozoic extinction events; however, differential origination during the Devonian results in a migration and subsequent stagnation of occupied morphospace. This shift appears linked to an ecological transition from euryhaline taxa to freshwater species with low morphological diversity alongside a decrease in endemism. These results demonstrate the importance of the Devonian biotic crisis in reshaping Paleozoic ecosystems. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Provenance Analysis of Upper Cretaceous - Paleogene Sandstones in the Foreland Basin System of the Tansen Unit, Central Nepal

NASA Astrophysics Data System (ADS)

Neupane, B.; Ju, Y.; Allen, C.

2016-12-01

The continental deposits foreland basin of Central Nepal, Amile Formation, Bhainskati Formation and Dumri Formation (Tansen unit) are the key region for provenance analysis, preserved almost complete sedimentation history of tectonic collision of Indian and Asian plates. Samples from two field traverses are examined petrographically and through zircon U-Pb dating, one traverse through the Tansen Group, and another through its potential source rocks, the Higher and Tethys Himalaya. The Tansen Group ages are well known through fossil assemblages. We examine sandstone-bearing units of the Tansen Group, the upper 3 of 5 Formations. The optical petrography data and resulting classify Tansen sediments as "recycled orogenic" and "Quartzose recycled", indicating that Indian cratonal sediments as the likely source of sediments for the Amile Formations, and the Tethyan Himalaya as the source for the Bhainskati Formation, and both the Tethys and Higher Himalaya as the major sources for the Dumri Formation. The Cretaceous to Paleocene pre-collisional Amile Formation is dominated by a broad 1830 Ma age peak with neither Paleozoic nor Neoproterozic zircons, but hosts a significant proportion (23%) of syndepositional Cretaceous zircons (121 to 105 Ma) indicative of nearby Cretaceous volcanism at that time. Therefore, the rare volcanic fragments in detritus of Amile Formation were derived from the Rajmahal Volcanic Province defining the middle to late Cretaceous depositional age. The other Formations of the Tansen Group are more similar to Tethys units than to Higher Himalaya. Further, the 23+/-1 Ma zircons in two of the crystalline Higher Himalaya units suggest that they could not have been exposed until at or after this time.

Paleozoic shale gas resources in the Sichuan Basin, China

USGS Publications Warehouse

Potter, Christopher J.

2018-01-01

The Sichuan Basin, China, is commonly considered to contain the world’s most abundant shale gas resources. Although its Paleozoic marine shales share many basic characteristics with successful United States gas shales, numerous geologic uncertainties exist, and Sichuan Basin shale gas production is nascent. Gas retention was likely compromised by the age of the shale reservoirs, multiple uplifts and orogenies, and migration pathways along unconformities. High thermal maturities raise questions about gas storage potential in lower Paleozoic shales. Given these uncertainties, a new look at Sichuan Basin shale gas resources is advantageous. As part of a systematic effort to quantitatively assess continuous oil and gas resources in priority basins worldwide, the US Geological Survey (USGS) completed an assessment of Paleozoic shale gas in the Sichuan Basin in 2015. Three organic-rich marine Paleozoic shale intervals meet the USGS geologic criteria for quantitative assessment of shale gas resources: the lower Cambrian Qiongzhusi Formation, the uppermost Ordovician Wufeng through lowermost Silurian Longmaxi Formations (currently producing shale gas), and the upper Permian Longtan and Dalong Formations. This study defined geologically based assessment units and calculated probabilistic distributions of technically recoverable shale gas resources using the USGS well productivity–based method. For six assessment units evaluated in 2015, the USGS estimated a mean value of 23.9 tcf (677 billion cubic meters) of undiscovered, technically recoverable shale gas. This result is considerably lower than volumes calculated in previous shale gas assessments of the Sichuan Basin, highlighting a need for caution in this geologically challenging setting.

CONSTRAINTS ON EXHUMATION AND SEDIMENTS PROVENANCE DURING PALEOGENE IN THE NORTHERN PYRENEES (FRANCE) USING DETRITAL AFT, ZHe AND Z(U/Pb) THERMOCHRONOLOGY

NASA Astrophysics Data System (ADS)

Filleaudeau, P.; Mouthereau, F.; Fellin, M.; Pik, R.; Lacombe, O.

2009-12-01

The Pyrenees are a doubly vergent orogenic wedge built by the convergence between the subducting Iberian microplate and the European plate lasting from late Cretaceous to early Miocene. The backbone of the Pyrenean belt (Axial Zone) consists in a stack of thrusts units composed of Paleozoic series intruded by late-Variscan granitoids. Both pro- and retro-wedge sides of the Pyrenees are fold-and-thrust belts made of Meso-Cenozoic sediments thrusted onto the Ebro and Aquitaine foreland basins. The deep structure, highlighted by the ECORS profile, shows a strong asymmetry caused by the southward migration of deformation associated with the development of a Paleogene antiformal stack emplaced during wedge growth in the Iberian plate. The present study focuses on the synorogenic deposits of the retro-foreland basin in the northern part of the belt. To examine the source rocks and quantify the exhumation rates, we combine fission track thermochronometry on detrital apatites with Helium diffusion and U/Pb thermochronometry on zircons. Due to the very high closure temperature of the U/Pb system and the wide range of age distribution, the U/Pb method, that provides zircon crystallisation ages, is a powerful tool to distinguish the various eroded sources feeding the North Pyrenean basin. Thus, we can separate grains coming from Variscan intrusive basement with ages around 310 Ma from younger grains coming from Permian or Triassic to lower Jurassic volcanics. Zircon ages of 220 Ma found in the Paleocene sandstones point to the Triassic volcanic rocks (the so-called “ophites”) as the main source of detrital grains. We infer that Paleozoic units of the Axial Zone were not outcropping in the Paleocene catchments. Exhumation rates are estimated through apatite fission track grain-age distributions and (U-Th)/He dating for two Lutetian and Bartonian synorogenic sandstone samples of the North Pyenean foreland basin. The first results obtained with AFT dating show two main grain

Geochronological framework of the early Paleozoic Bainaimiao Cu-Mo-Au deposit, NE China, and its tectonic implications

NASA Astrophysics Data System (ADS)

Zhou, Zhen-Hua; Mao, Jing-Wen; Ma, Xing-Hua; Che, He-Wei; Ou'yang, He-Gen; Gao, Xu

2017-08-01

The Bainaimiao Cu-Mo-Au deposit of NE China is an important ore deposit in the middle section of the northern margin of the North China Craton. The early Paleozoic Bainaimiao Group is the main ore-hosting rock. The mineralization at the deposit shows features of porphyry alteration and late-stage orogenesis and transformation. Zircon LA-ICP-MS U-Pb age data indicate that the ages of the Third and Fifth formations of the Bainaimiao Group are 492.7 ± 2.9 Ma (MSWD = 0.53) and 488.9 ± 3.1 Ma (MSWD = 0.92), respectively. The age of quartz diorite that intrudes the Bainaimiao Group is 459.3 ± 6.4 Ma (MSWD = 2.20). Molybdenite samples from massive Cu-Mo-bearing ores and quartz veins in the southern ore belt yield a Re-Os isochron age of 438.2 ± 2.7 Ma (MSWD = 0.16), which is consistent with the Re-Os isochron age of molybdenite in the northern ore belt, implying that the two ore belts belong to the same mineralization system. Muscovite from a post-magmatic Cu-Mo-bearing quartz-calcite vein yields an Ar-Ar isochron age of 422.5 ± 3.9 Ma (MSWD = 0.64) with an initial 40Ar/36Ar ratio of 286 ± 21. The well-defined plateau age of the muscovite is 422.4 ± 2.6 Ma (MSWD = 0.05), which represents the time of the post-magmatic orogenic transformation event. Based on our new age data and previous findings, we propose that the Bainaimiao Cu-Mo-Au deposit formed in an active continental margin setting and experienced four stages of ore mineralization: (1) a Late Cambrian-Middle Ordovician volcanic-sedimentary stage; (2) a Late Ordovician porphyry mineralization stage; (3) a Late Silurian regional metamorphism stage; and (4) an orogenic transformation stage. Subhedral and euhedral Paleoproterozoic (2402-1810 Ma) inherited zircons indicate that the Bainaimiao Group has a tectonic affinity with the North China Craton. The Central Asian Orogenic Belt, which is closely related to the complex closure of the Paleo-Asian Ocean, is favorable for prospecting for Paleozoic porphyry Cu

Sandstone provenance and U-Pb ages of detrital zircons from Permian-Triassic forearc sediments within the Sukhothai Arc, northern Thailand: Record of volcanic-arc evolution in response to Paleo-Tethys subduction

NASA Astrophysics Data System (ADS)

Hara, Hidetoshi; Kunii, Miyuki; Miyake, Yoshihiro; Hisada, Ken-ichiro; Kamata, Yoshihito; Ueno, Katsumi; Kon, Yoshiaki; Kurihara, Toshiyuki; Ueda, Hayato; Assavapatchara, San; Treerotchananon, Anuwat; Charoentitirat, Thasinee; Charusiri, Punya

2017-09-01

Provenance analysis and U-Pb dating of detrital zircons in Permian-Triassic forearc sediments from the Sukhothai Arc in northern Thailand clarify the evolution of a missing arc system associated with Paleo-Tethys subduction. The turbidite-dominant formations within the forearc sediments include the Permian Ngao Group (Kiu Lom, Pha Huat, and Huai Thak formations), the Early to earliest Late Triassic Lampang Group (Phra That and Hong Hoi formations), and the Late Triassic Song Group (Pha Daeng and Wang Chin formations). The sandstones are quartzose in the Pha Huat, Huai Thak, and Wang Chin formations, and lithic wacke in the Kiu Lom, Phra That, Hong Hoi and Pha Daeng formations. The quartzose sandstones contain abundant quartz, felsic volcanic and plutonic fragments, whereas the lithic sandstones contain mainly basaltic to felsic volcanic fragments. The youngest single-grain (YSG) zircon U-Pb age generally approximates the depositional age in the study area, but in the case of the limestone-dominant Pha Huat Formation the YSG age is clearly older. On the other hand, the youngest cluster U-Pb age (YC1σ) represents the peak of igneous activity in the source area. Geological evidence, geochemical signatures, and the YC1σ ages of the sandstones have allowed us to reconstruct the Sukhothai arc evolution. The initial Sukhothai Arc (Late Carboniferous-Early Permian) developed as a continental island arc. Subsequently, there was general magmatic quiescence with minor I-type granitic activity during the Middle to early Late Permian. In the latest Permian to early Late Triassic, the Sukhothai Arc developed in tandem with Early to Middle Triassic I-type granitic activity, Middle to Late Triassic volcanism, evolution of an accretionary complex, and an abundant supply of sediments from the volcanic rocks to the trench through a forearc basin. Subsequently, the Sukhothai Arc became quiescent as the Paleo-Tethys closed after the Late Triassic. In addition, parts of sediments of

High-temperature quartz cement and the role of stylolites in a deep gas reservoir, Spiro Sandstone, Arkoma Basin, USA

USGS Publications Warehouse

Worden, Richard H.; Morad, Sadoon; Spötl, C.; Houseknecht, D.W.; Riciputi, L.R.

2000-01-01

The Spiro Sandstone, a natural gas play in the central Arkoma Basin and the frontal Ouachita Mountains preserves excellent porosity in chloritic channel-fill sandstones despite thermal maturity levels corresponding to incipient metamorphism. Some wells, however, show variable proportions of a late-stage, non-syntaxial quartz cement, which post-dated thermal cracking of liquid hydrocarbons to pyrobitumen plus methane. Temperatures well in excess of 150°C and possibly exceeding 200°C are also suggested by (i) fluid inclusions in associated minerals; (ii) the fact that quartz post-dated high-temperature chlorite polytype IIb; (iii) vitrinite reflectance values of the Spiro that range laterally from 1.9 to ≥ 4%; and (iii) the occurrence of late dickite in these rocks. Oxygen isotope values of quartz cement range from 17.5 to 22.4‰ VSMOW (total range of individual in situ ion microprobe measurements) which are similar to those of quartz cement formed along high-amplitude stylolites (18.4–24.9‰). We favour a model whereby quartz precipitation was controlled primarily by the availability of silica via deep-burial stylolitization within the Spiro Sandstone. Burial-history modelling showed that the basin went from a geopressured to a normally pressured regime within about 10–15 Myr after it reached maximum burial depth. While geopressure and the presence of chlorite coats stabilized the grain framework and inhibited nucleation of secondary quartz, respectively, stylolites formed during the subsequent high-temperature, normal-pressured regime and gave rise to high-temperature quartz precipitation. Authigenic quartz growing along stylolites underscores their role as a significant deep-burial silica source in this sandstone.

Geometrical characteristics of sandstone with different sample sizes

NASA Astrophysics Data System (ADS)

Cheon, D. S.; Takahashi, M., , Dr

2017-12-01

In many rock engineering projects such as CO2 underground storage, engineering geothermal system, it is important things to understand the fluid flow behavior in the deep geological conditions. This fluid flow is generally affected by the geometrical characteristics of rock, especially porous media. Furthermore, physical properties in rock may depend on the existence of voids space in rock. Total porosity and pore size distribution can be measured by Mercury Intrusion Porosimetry and the other geometrical and spatial information of pores can be obtained through micro-focus X-ray CT. Using the micro-focus X-ray CT, we obtained the extracted void space and transparent image from the original CT voxel images of with different sample sizes like 1 mm, 2 mm, 3 mm cubes. The test samples are Berea sandstone and Otway sandstone. The former is well-known sandstone and it is used for the standard sample to compared to the result from the Otway sandstone. Otway sandstone was obtained from the CO2CRC Otway pilot site for the CO2 geosequestraion project. From the X-ray scan and ExFACT software, we get the informations including effective pore radii, coordination number, tortuosity and effective throat/pore radius ratio etc. The geometrical information analysis showed that for Berea sandstone and Otway sandstone, there is rarely differences with different sample sizes and total value of coordination number show high porosity, the tortuosity of Berea sandstone is higher than the Otway sandstone. In the future, these information will be used for the permeability of the samples.

Sandstone-body and shale-body dimensions in a braided fluvial system: Salt wash sandstone member (Morrison formation), Garfield County, Utah

USGS Publications Warehouse

Robinson, J.W.; McCabea, P.J.

1997-01-01

Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, singlestory sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to

A unique ore-placer area of the Amur region with high-Hg gold

NASA Astrophysics Data System (ADS)

Melnikov, A. V.; Stepanov, V. A.; Moiseenko, V. G.

2017-10-01

This work presents the geological structure and a description of the gold-ore occurrences and gold placers of the Un'ya-Bom ore-placer cluster of the Amur gold-bearing province. The host rocks are Late Paleozoic and Mesozoic black shales. Intrusive formations occur rarely. The sublatitudinal Un'ya Thrust is the principal ore-controlling structure. Paleozoic sandstones are thrust over Mesozoic flysch deposits along the Un'ya Thrust. The gold-ore occurrences are represented by quartz-vein zones. The ores are gold-quartz, low-sulfide. Ore minerals are arsenopyrite, scheelite, ferberite, galena, and native gold. High-Hg native gold was revealed in the ore occurrences and placers. The high Hg content in native gold is explained by the presence of the frontal part of the gold-bearing column located within the cluster; the rich placers were formed due to crushing of this column.

Tectonics and hydrocarbon potential of the Barents Megatrough

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

Baturin, D.; Vinogradov, A.; Yunov, A.

1991-08-01

Interpretation of geophysical data shows that the geological structure of the Eastern Barents Shelf, named Barents Megatrough (BM), extends sublongitudinally almost from the Baltic shield to the Franz Josef Land archipelago. The earth crust within the axis part of the BM is attenuated up to 28-30 km, whereas in adjacent areas its thickness exceeds 35 km. The depression is filled with of more than 15 km of Upper Paleozoic, Mesozoic, and Cenozoic sediments overlying a folded basement of probable Caledonian age. Paleozoic sediments, with exception of the Upper Permian, are composed mainly of carbonates and evaporites. Mesozoic-Cenozoic sediments are mostlymore » terrigenous. The major force in the development of the BM was due to extensional tectonics. Three rifting phases are recognizable: Late Devonian-Early Carboniferous, Early Triassic, and Jurassic-Early Cretaceous. The principal features of the geologic structure and evolution of the BM during the late Paleozoic-Mesozoic correlate well with those of the Sverdup basin, Canadian Arctic. Significant quantity of Late Jurassic-Early Cretaceous basaltic dikes and sills were intruded within Triassic sequence during the third rifting phase. This was probably the main reason for trap disruption and hydrocarbon loss from Triassic structures. Lower Jurassic and Lower Cretaceous reservoir sandstones are most probably the main future objects for oil and gas discoveries within the BM. Upper Jurassic black shales are probably the main source rocks of the BM basin, as well as excellent structural traps for hydrocarbon fluids from the underlying sediments.« less

Shoreface to estuarine sedimentation in the late Paleocene Matanomadh Formation, Kachchh, western India

NASA Astrophysics Data System (ADS)

Srivastava, V. K.; Singh, B. P.

2017-04-01

Late Paleocene sedimentation in the pericratonic Kachchh Basin marks the initial marine transgression during the Cenozoic era. A 17 m thick sandstone-dominated succession, known as the clastic member (CM) of the Matanomadh Formation (MF), is exposed sporadically in the basin. Three facies associations are reconstructed in the succession in three different sections. Facies association-1 contains matrix-supported pebbly conglomerate facies, horizontally-laminated sandstone-mudstone alternation facies, hummocky- and swaley cross-bedded sandstone facies, wave-rippled sandstone facies and climbing ripple cross-laminated sandstone facies. This facies association developed between shoreface and foreshore zone under the influence of storms on a barrier ridge. Facies association-2 contains sigmoidal cross-bedded sandstone facies, sandstone-mudstone alternation facies, flaser-bedded sandstone facies, herringbone cross-bedded sandstone facies and tangential cross-bedded sandstone facies. This facies association possessing tidal bundles and herringbone cross-beds developed on a tidal flat with strong tidal influence. Facies association-3 comprises pebbly sandstone facies, horizontally-bedded sandstone facies, tangential cross-bedded sandstone facies exhibiting reactivation surfaces and tabular cross-bedded sandstone facies. This facies association represents sedimentation in a river-dominated estuary and reactivation surfaces and herringbone cross-beds indicating tidal influence. The bipolar paleocurrent pattern changes to unipolar up-section because of the change in the depositional currents from tidal to fluvial. The sedimentation took place in an open coast similar to the Korean coast. The presence of neap-spring tidal rhythmites further suggests that a semidiurnal system similar to the modern day Indian Ocean was responsible for the sedimentation. Here, the overall sequence developed during the transgressive phase where barrier ridge succession is succeeded by the tidal

Provenance and petrofacies, Upper Devonian sandstones, Philip Smith Mountains and Arctic quandrangles, Brooks Range, Alaska: Final report, Project No. 3

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

Anderson, A.V.; Coney, P.J.

1987-11-01

Late Devonian sandstone beds are exposed as allochthonous sequences that extend for over 1000 km along the east-west strike of the Brooks Range in northern Alaska. These horizons, at least in part, record Late Devonian tectonism and deposition along the southern margin of the Arctic Alaska block. This study identifies clastic petrofacies in the western Philip Smith Mountains and southern Arctic quadrangles and infers the composition of the source terrane. The paleogeography is not known and the original distribution of lithofacies is uncertain, owing to the extensive post-depositional tectonism. In the study area the sandstones are exposed along rugged mountainmore » tops and high ridges. Although exposures are excellent, access is often difficult. Samples were collected from exposures near the western end of the Chandalar Shelf, Atigun Pass, and the Atigun River valley in the Philip Smith Mountains quadrangle and from the Crow Nest Creek and Ottertail Creek areas in the Arctic quadrangle. 34 refs., 17 figs.« less

Improving global paleogeography since the late Paleozoic using paleobiology

NASA Astrophysics Data System (ADS)

Cao, Wenchao; Zahirovic, Sabin; Flament, Nicolas; Williams, Simon; Golonka, Jan; Dietmar Müller, R.

2017-12-01

Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, paleoclimate and ocean circulation, deep Earth resources and to constrain and interpret the dynamic topography predicted by mantle convection models. Global paleogeographic maps have been compiled and published, but they are generally presented as static maps with varying map projections, different time intervals represented by the maps and different plate motion models that underlie the paleogeographic reconstructions. This makes it difficult to convert the maps into a digital form and link them to alternative digital plate tectonic reconstructions. To address this limitation, we develop a workflow to restore global paleogeographic maps to their present-day coordinates and enable them to be linked to a different tectonic reconstruction. We use marine fossil collections from the Paleobiology Database to identify inconsistencies between their indicative paleoenvironments and published paleogeographic maps, and revise the locations of inferred paleo-coastlines that represent the estimated maximum transgression surfaces by resolving these inconsistencies. As a result, the consistency ratio between the paleogeography and the paleoenvironments indicated by the marine fossil collections is increased from an average of 75 % to nearly full consistency (100 %). The paleogeography in the main regions of North America, South America, Europe and Africa is significantly revised, especially in the Late Carboniferous, Middle Permian, Triassic, Jurassic, Late Cretaceous and most of the Cenozoic. The global flooded continental areas since the Early Devonian calculated from the revised paleogeography in this study are generally consistent with results derived from other paleoenvironment and paleo-lithofacies data and with the strontium isotope record in marine carbonates. We also estimate the terrestrial areal change over time associated with

Geochemistry and chronology of the early Paleozoic diorites and granites in the Huangtupo volcanogenic massive sulfide (VMS) deposit, Eastern Tianshan, NW China: Implications for petrogenesis and geodynamic setting

NASA Astrophysics Data System (ADS)

Zheng, Jiahao; Chai, Fengmei; Feng, Wanyi; Yang, Fuquan; Shen, Ping

2018-03-01

The Eastern Tianshan orogen contains many late Paleozoic porphyry Cu and magmatic Cu-Ni deposits. Recent studies demonstrate that several early Paleozoic volcanogenic massive sulfide (VMS) Cu-polymetallic and porphyry Cu deposits were discovered in the northern part of Eastern Tianshan. This study presents zircon U-Pb, whole-rock geochemical, and Sr-Nd isotopic data for granites and diorites from the Huangtupo VMS Cu-Zn deposit, northern part of the Eastern Tianshan. Our results can provide constraints on the genesis of intermediate and felsic intrusions as well as early Paleozoic geodynamic setting of the northern part of Eastern Tianshan. LA-ICP-MS zircon U-Pb analyses suggest that the granites and diorites were formed at 435 ± 2 Ma and 440 ± 2 Ma, respectively. Geochemical characteristics suggest that the Huangtupo granites and diorites are metaluminous rocks, exhibiting typical subduction-related features such as enrichment in LILE and LREE and depletion in HFSE. The diorites have moderate Mg#, positive εNd(t) values (+6.4 to +7.3), and young Nd model ages, indicative of a depleted mantle origin. The granites exhibit mineral assemblages and geochemical characteristics of I-type granites, and they have positive εNd(t) values (+6.7 to +10.2) and young Nd model ages, suggesting a juvenile crust origin. The early Paleozoic VMS Cu-polymetallic and porphyry Cu deposits in the northern part of Eastern Tianshan were genetically related. The formation of the early Paleozoic magmatic rocks as well as VMS and porphyry Cu deposits in the northern part of Eastern Tianshan was due to a southward subduction of the Junggar oceanic plate.

Depositional environments during the Late Palaeozoic ice age (LPIA) in northern Ethiopia, NE Africa

NASA Astrophysics Data System (ADS)

Bussert, Robert

2014-11-01

The Late Palaeozoic sediments in northern Ethiopia record a series of depositional environments during and after the Late Paleozoic ice age (LPIA). These sediments are up to 200 m thick and exceptionally heterogeneous in lithofacies composition. A differentiation of numerous types of lithofacies associations forms the basis for the interpretation of a large range of depositional processes. Major glacigenic lithofacies associations include: (1) sheets of diamictite, either overlying glacially eroded basement surfaces or intercalated into the sediment successions, and representing subglacial tillites, (2) thick massive to weakly stratified muddy clast-poor diamictites to lonestone-bearing laminated mudstones originating from a combination of suspension settling of fines and iceberg rainout, (3) lensoidal or thin-bedded diamictites deposited from debris flows, (4) wedges of traction and gravity transported coarse-grained sediments deposited in outwash fans, (5) irregular wedges or sheets of mudstones deformed primarily by extension and incorporating deformed beds or rafts of other lithofacies formed by slumping, and (6) irregular bodies of sandstone, conglomerate and diamictite deformed by glacial pushing. The dominance of laminated or massive clast-bearing mudstones in most successions indicates ice-contact water bodies as the major depositional environment. Into this environment, coarse-grained sediments were transported by various gravity driven transport processes, including dropstone activity of ice-bergs, slumping, cohesive debris flow, hyperconcentrated to concentrated flow, hyperpycnal flow, and by turbidity flow. Close to glacier termini, wedge-shaped bodies of conglomerate, sandstone, diamictite and mudstone were deposited primarily in subaqueous outwash-fans. Soft-sediment deformation of these sediments either records ice push during glacier advance or re-sedimentation by slumping. Apart from an initial glacier advance when thick ice of temperate or

Early Paleozoic tectonics for the New Siberian Islands terrane (Eastern Arctic)

NASA Astrophysics Data System (ADS)

Metelkin, D. V.; Chernova, A. I.; Vernikovsky, V. A.; Matushkin, N. Yu.

2017-11-01

The New Siberian Islands archipelago is one of the few research objects accessible for direct study on the eastern Arctic shelf. There are several models that have different interpretations of the Paleozoic tectonic history and the structural affinity of the New Siberian Islands terrane. Some infer a direct relationship with the passive continental margin of the Siberian paleocontinent. Others connect it with the marginal basins of Baltica and Laurentia, or the Chukotka-Alaska microplate. Our paleomagnetic investigation led us to create an apparent polar wander path for the early Paleozoic interval of geological history. Based on it we can conclude that the New Siberian Islands terrane could not have been a part of these continental plates. This study considers the possible tectonic scenarios of the Paleozoic history of the Earth, presents and discusses the corresponding global reconstructions describing the paleogeography and probable mutual kinematics of the terranes of the Eastern Arctic.

Geologic map of the Vail East quadrangle, Eagle County, Colorado

USGS Publications Warehouse

Kellogg, Karl S.; Bryant, Bruce; Redsteer, Margaret H.

2003-01-01

New 1:24,000-scale geologic mapping along the Interstate-70 urban corridor in western Colorado, in support of the State/USGS Cooperative Geologic Mapping Project, is contributing to a more complete understanding of the stratigraphy, structure, tectonic evolution, and hazard potential of this rapidly developing region. The 1:24,000-scale Vail East quadrangle straddles the Gore fault system, the western structural boundary of the Gore Range. The Gore fault system is a contractional structure that has been recurrently active since at least the early Paleozoic and marks the approximate eastern boundary of the Central Colorado trough, a thick late Paleozoic depocenter into which thousands of meters of clastic sediment were deposited from several uplifts, including the ancestral Front Range. The Gore fault was active during both the late Paleozoic and Upper Cretaceous-lower Tertiary (Laramide) deformations. In addition, numerous north-northwest faults that cut the crystalline rocks of the Gore Range were active during at least 5 periods, the last of which was related to Neogene uplift of the Gore Range and formation of the northern Rio Grande rift. Early Proterozoic crystalline rocks underlie the high Gore Range, north and east of the Gore fault system. These rocks consist predominantly of migmatitic biotite gneiss intruded by mostly granitic rocks of the 1.667-1.750 Ma Cross Creek batholith, part of the 1,667-1,750 Ma Routt Plutonic Suite (Tweto, 1987). Southwest of the Gore fault, a mostly gently south-dipping sequence of Pennsylvanian Mimturn Formation, as thick as 1,900 m, and the Permian and Pennsylvanian Maroon Formation (only the basal several hundred meters are exposed in the quadrangle)were shed from the ancestral Front Range and overlie a thin sequence of Devonian and Cambrian rocks. The Minturn Formation is a sequence of interlayered pink, maroon, and gray conglomerate, sandstone, shale, and marine limestone. The Maroon Formation is mostly reddish conglomerate

Publications - GMC 53C | Alaska Division of Geological & Geophysical

Science.gov Websites

Alaska's Mineral Industry Reports AKGeology.info Rare Earth Elements WebGeochem Engineering Geology Alaska Paleozoic through Tertiary sandstones, North Slope, Alaska Authors: Alaska Research Associates Publication through Tertiary sandstones, North Slope, Alaska: Alaska Division of Geological & Geophysical Surveys

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

NASA Astrophysics Data System (ADS)

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

1994-12-01

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

Provenance of Late Ordovician Sandstones along the southeastern Appalachian Mountains: Implications for the Tectonic Model of the Taconic Orogeny

NASA Astrophysics Data System (ADS)

Guerrero, J. C.; Herrmann, A. D.; Haynes, J.

2017-12-01

A provenance study of sandstones along the southeastern Appalachian Mountains has been conducted in order to test the current volcanic arc-continent collision and foreland basin formation model of the Taconic Orogeny. Samples along the southeastern Appalachians were taken from sandstone sequences deposited between 460-450 Ma. Results from these sandstones show three dominate age ranges: 465-685 Ma, 980-1300 Ma, and 1300-1500 Ma. The 980-1300 Ma and 1300-1500 Ma ages are seen throughout the study area and are compatible with previously reported ages of the Grenville Orogeny and the Rhyolite-Granite Province. The northernmost samples have a small quantity of 465-685 Ma zircons which is attributed to an accretionary wedge that formed as a result of the continent-island arc collision and acted as a physical barrier keeping sediment from depositing within the basin. The younger age signal becomes stronger to the south, as samples in Georgia and Alabama show strong concentrations of 465-685 zircons. These ages are attributed to exotic terranes (Dalhonega Terrane and Carolina Terrane) that were accreted onto Laurentia during the Taconic Orogeny and/or a possible change in subduction direction leading to a back-arc basin model for the southern Appalachian Taconic Orogeny. The results from this provenance analysis support previous studies indicating that the model for the Taconic Orogeny is a combined A-type subduction for the north and a B-type subduction model for the southern part of the orogeny.

Fast evolving conduits in clay-bonded sandstone: Characterization, erosion processes and significance for the origin of sandstone landforms

NASA Astrophysics Data System (ADS)

Bruthans, Jiri; Svetlik, Daniel; Soukup, Jan; Schweigstillova, Jana; Valek, Jan; Sedlackova, Marketa; Mayo, Alan L.

2012-12-01

In Strelec Quarry, the Czech Republic, an underground conduit network > 300 m long with a volume of ~ 104 m3 and a catchment of 7 km2 developed over 5 years by groundwater flow in Cretaceous marine quartz sandstone. Similar landforms at natural exposures (conduits, slot canyons, undercuts) are stabilized by case hardening and have stopped evolving. The quarry offers a unique opportunity to study conduit evolution in sandstone at local to regional scales, from the initial stage to maturity, and to characterize the erosion processes which may form natural landforms prior to stabilization. A new technique was developed to distinguish erodible and non-erodible sandstone surfaces. Based on measurements of relative erodibility, drilling resistance, ambient and water-saturated tensile strength (TS) at natural and quarry exposures three distinct kinds of surfaces were found. 1) Erodible sandstone exposed at ~ 60% of surfaces in quarry. This sandstone loses as much as 99% of TS when saturated. 2) Sub-vertical fracture surfaces that are non-erodible already prior to exposure at ground surface and which keep considerable TS if saturated. 3) Case hardened surfaces that start to form after exposure. In favorable conditions they became non-erodible and reach the full TS in just 6 years. An increase in the hydraulic gradient from ~ 0.005 to > 0.02 triggered conduit evolution, based on long-term monitoring of water table in 18 wells and inflows to the quarry. Rapidly evolving major conduits are characterized by a channel gradient of ~ 0.01, a flow velocity ~ 40 cm/s and sediment concentration ~ 10 g/l. Flow in openings with a discharge 1 ml/s and hydraulic gradient > 0.05 exceeds the erosion threshold and initiates piping. In the first phase of conduit evolution, fast concentrated flow mobilizes erodible sandstone between sets of parallel fractures in the shallow phreatic zone. In the second phase the conduit opening mainly expands vertically upward into the vadose zone by mass

Geologic map and upper Paleozoic stratigraphy of the Marble Canyon area, Cottonwood Canyon quadrangle, Death Valley National Park, Inyo County, California

USGS Publications Warehouse

Stone, Paul; Stevens, Calvin H.; Belasky, Paul; Montañez, Isabel P.; Martin, Lauren G.; Wardlaw, Bruce R.; Sandberg, Charles A.; Wan, Elmira; Olson, Holly A.; Priest, Susan S.

2014-01-01

This geologic map and pamphlet focus on the stratigraphy, depositional history, and paleogeographic significance of upper Paleozoic rocks exposed in the Marble Canyon area in Death Valley National Park, California. Bedrock exposed in this area is composed of Mississippian to lower Permian (Cisuralian) marine sedimentary rocks and the Jurassic Hunter Mountain Quartz Monzonite. These units are overlain by Tertiary and Quaternary nonmarine sedimentary deposits that include a previously unrecognized tuff to which we tentatively assign an age of late middle Miocene (~12 Ma) based on tephrochronologic analysis, in addition to the previously recognized Pliocene tuff of Mesquite Spring. Mississippian and Pennsylvanian rocks in the Marble Canyon area represent deposition on the western continental shelf of North America. Mississippian limestone units in the area (Tin Mountain, Stone Canyon, and Santa Rosa Hills Limestones) accumulated on the outer part of a broad carbonate platform that extended southwest across Nevada into east-central California. Carbonate sedimentation was interrupted by a major eustatic sea-level fall that has been interpreted to record the onset of late Paleozoic glaciation in southern Gondwana. Following a brief period of Late Mississippian clastic sedimentation (Indian Springs Formation), a rise in eustatic sea level led to establishment of a new carbonate platform that covered most of the area previously occupied by the Mississippian platform. The Pennsylvanian Bird Spring Formation at Marble Canyon makes up the outer platform component of ten third-order (1 to 5 m.y. duration) stratigraphic sequences recently defined for the regional platform succession. The regional paleogeography was fundamentally changed by major tectonic activity along the continental margin beginning in middle early Permian time. As a result, the Pennsylvanian carbonate shelf at Marble Canyon subsided and was disconformably overlain by lower Permian units (Osborne Canyon and

Illitization and paleothermal regimes in the Middle Ordovician St. Peter Sandstone, Central Michigan Basin: K-Ar, Oxygen Isotope, and fluid inclusion data

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

Girard, J.P.; Barnes, D.A.

1995-01-01

Hydrocarbon reservoirs occur in the Middle Ordovician St. Peter Sandstone in the central Michigan basin at depths of 1.5-3.5 km and are diagenetically altered. Latest diagenetic cements include saddle dolomite, pervasive microcrystalline illite and chlorite, and quartz. A K-Ar and {sup 18}O/{sup 16}O study of the fine-grained authigenic illite in 25 samples from 16 wells covering a large area within the basin yields K-Ar ages ranging from 367 to 322 Ma and {delta}{sup 18}O values between 12.7 and 16.9% SMOW. The {delta}{sup 18}O values of diagenetic quartz overgrowths range from 15.2 to 18.9%. Fluid inclusion temperatures in the quartz cementmore » range from 70 to 170{degrees}C, reflecting multiple generations of diagenetic quartz and/or precipitation over most of the diagenetic history. Reequilibrated fluid inclusions in the saddle dolomite cement yield temperatures ranging from 90 to 150{degrees}C. A regionally significant episode of illitization occurred during the Late Devonian-Mississipian. Temperatures of illite formation are indirectly estimated to be in the range of 125-170{degrees}C and most paleodepths of illitization are between 2.8 and 3.2 km. These results imply that (1) illite formed from {sup 18}O-rich fluids, and (2) elevated geothermal gradients, i.e., greater than 34% C/km, existed in the Michigan basin in the late Paleozoic. The K-Ar ages and the {delta}{sup 18}O values are not correlated to present depths of the samples or paleodepths of illitization. Illites with young ages and low {delta}{sup 18}O values tend to be geographically distributed along the north-south branch of the buried Precambrian rift. The {delta}{sup 18}O values of the diagenetic quartz follow a similar trend. The spread of illite K-Ar ages and {delta}{sup 19}O values, and their geographic distribution, are best explained as reflecting abnormally high thermal regimes in the part of the basin located above the presumably highly fractured basement along the rift.« less

Petrophysics and hydrocarbon potential of Paleozoic rocks in Kuwait

NASA Astrophysics Data System (ADS)

Abdullah, Fowzia; Shaaban, Fouad; Khalaf, Fikry; Bahaman, Fatma; Akbar, Bibi; Al-Khamiss, Awatif

2017-10-01

Well logs from nine deep exploratory and development wells in Kuwaiti oil fields have been used to study petrophysical characteristics and their effect on the reservoir quality of the subsurface Paleozoic Khuff and Unayzah formations. Petrophysical log data have been calibrated with core analysis available at some intervals. The study indicates a complex lithological facies of the Khuff Formation that is composed mainly of dolomite and anhydrite interbeds with dispersed argillaceous materials and few limestone intercalations. This facies greatly lowered the formation matrix porosity and permeability index. The porosity is fully saturated with water, which is reflected by the low resistivity logs responses, except at some intervals where few hydrocarbon shows are recorded. The impermeable anhydrites, massive (low-permeability) carbonate rock and shale at the lower part of the formation combine to form intraformational seals for the clastic reservoirs of the underlying Unayzah Formation. By contrast, the log interpretation revealed clastic lithological nature of the Unayzah Formation with cycles of conglomerate, sandstone, siltstone, mudstone and shales. The recorded argillaceous materials are mainly of disseminated habit, which control, for some extent, the matrix porosity, that ranges from 2% to 15% with water saturation ranges from 65% to 100%. Cementation, dissolution, compaction and clay mineral authigenesis are the most significant diagenetic processes affecting the reservoir quality. Calibration with the available core analysis at some intervals of the formation indicates that the siliciclastic sequence is a fluvial with more than one climatic cycle changes from humid, semi-arid to arid condition and displays the impact of both physical and chemical diagenesis. In general, the study revealed that the Unyazah Formation has a better reservoir quality than the Khuff Formation and possible gas bearing zones.

Incised valley fill interpretation for Mississippian Black Hand Sandstone, Appalachian Basin, USA: Implications for glacial eustasy at Kinderhookian-Osagean (Tn2-Tn3) boundary

USGS Publications Warehouse

Matchen, D.L.; Kammer, T.W.

2006-01-01

Lower Mississippian strata of east-central Ohio are predominantly fine-grained marine deposits of the Cuyahoga and Logan formations. Within these sediments is the Black Hand Sandstone of the Cuyahoga Formation. The Black Hand Sandstone is a multistory, crossbedded, coarse-grained conglomeratic sandstone. The contact between the Black Hand Sandstone and the subjacent Cuyahoga Formation is sharp and scoured, with intraclasts of the Cuyahoga Formation incorporated into the basal Black Hand Sandstone. The Black Hand Sandstone was previously thought to represent a distributary channel deposit; however, the combination of lithofacies and architectural elements indicates deposition in a braided stream setting. The Cuyahoga Formation was deposited in a shallow marine setting. The erosional basal contact of the Black Hand Sandstone and the juxtaposition of fluvial and marine sediments suggests a sequence boundary. The geographic distribution of the Black Hand Sandstone combined with the evidence for a sequence boundary suggests deposition in an incised valley. The age of the Black Hand Sandstone is key to inferring the causes of valley incision. The Black Hand Sandstone is nearly devoid of body fossils, necessitating a biostratigraphic analysis of the surrounding Cuyahoga and Logan formations. Analysis indicates the Logan Formation is early Osagean age. Data from the Cuyahoga Formation suggest a Kinderhookian age with a possible transition to the Osagean in the uppermost Cuyahoga Formation. This constrains the age of the Black Hand Sandstone to the transition at the Kinderhookian-Osagean boundary. Recent reports indicate late Kinderhookian (Tournaisian, Tn2) Gondwanan glaciation based upon tillites and sharp excursions in stable-isotope curves. A glacio-eustatic fall in sea level is inferred to have caused incision of the Cuyahoga Formation, followed by deposition of the Black Hand Sandstone and Logan Formation during the subsequent sea level rise. The associated

Dakota sandstone facies, western Oklahoma panhandle

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

Atalik, E.; Mansfield, C.F.

The Cretaceous Dakota Sandstone in Cimarron County comprised three sandstone units and intervening mudrocks; it overlies the Kiowa Shale Member of the Purgatoire Formation. Deposits include shoreface, beach (foreshore) and dune, estuarine and tidal channel, marine marginal bay and swamp/marsh in a generally progradational sequences associated with marine regression in the Western Interior. The shoreface sand, characterized by ripple lamination, bioturbation and the trace fossils Teichichnus and Thalassinoides, is fine-grained, 5-10 m (15-30 ft) thick and grades into the underlying Kiowa Shale. Beach and associated dune deposits are 2-5 m (6-16 ft) thick, medium to fine-grained, medium to thick-bedded, tabular-planarmore » cross-bedded, and lenticular; cross-bed paleocurrent headings are northeasterly and northwesterly. Estuarine channel deposits are 3-5 m (10 to 16 ft) thick, trough to tabular-planar cross-bedded, and medium to coarse-grained with local conglomerate overlying the scoured base which commonly cuts into the Kiowa Shale or overlying shoreface sandstone; rip-up clasts and wood pieces are common but trace fossils are rare; southeasterly and southwesterly paleocurrents predominate. Tidal channel deposits are thinner (up to 2 m of 6 ft) and finer grained (medium to fine-grained) that the estuarine channel deposits; they occur within fine-grained sandstone and mudrock sequences, are trough cross-bedded, and commonly contain trace fossils (e.g., Skolithos) and wood fragments. Marine marginal (tidal flat or bay.) deposits comprise fine-grained sandstone, siltstone and interbedded shale, that are 1-3m (3-10 ft) thick with abundant burrows, small ripple marks, and parallel lamination. These grade into the fine to very fine-grained sandstones, siltstones, shales, and coals of the swamp/marsh deposits that are 1-5m (3-16 ft) thick and contain ripple marks, burrows, other trace fossils, and parallel lamination.« less

Pore water evolution in sandstones of the Groundhog Coalfield, northern Bowser Basin, British Columbia

NASA Astrophysics Data System (ADS)

Cookenboo, H. O.; Bustin, R. M.

1999-01-01

The succession of sandstone cements in chert and volcanic lithic arenites and wackes from the northern Bowser Basin of British Columbia comprises a record of diagenesis in shallow marine, deltaic, and coastal plain siliciclastic sediments that pass through the oil window and reach temperatures near the onset of metamorphism. The succession of cements is consistent with seawater in the sandstones mixing with acid waters derived from dewatering of interbedded organic rich muds. Sandstone cement paragenesis includes seven discrete cement stages. From earliest to latest the cement stages are: (1) pore-lining chlorite; (2) pore-lining to pore-filling illite; (3) pore-filling kaolinite; (4) oil migration through some of the remaining connected pores; (5) chlorite dissolution; (6) quartz cement; and (7) calcite cement. These seven cement stages are interpreted as a record of the evolution of pore waters circulating through the sandstones after burial. The earliest cement stages, as well as the depositional environments, are compatible with seawater as the initial pore fluid. Seawater composition changed during transport through the sandstones, first by loss of Mg 2+ and Fe 2+ during chlorite precipitation (stage 1). Dewatering of interbedded organic-rich mudstones probably added Mg 2+ and Fe 2+ to partially buffer the loss of these cations to chlorite. Acids produced during breakdown of organic matter are presumed to have mixed into sandstone pore fluids due to further compaction of the muds, leading to reduction of initial alkalinity. Reduction in alkalinity, in turn, favours change from chlorite to illite precipitation (stage 2), and finally to kaolinite (stage 3). Pore waters likely reached their peak acidity at the time of oil migration (stage 4). Chlorite dissolution (stage 5) and quartz precipitation (stage 6) occurred when pores were filled by these hydrocarbon-bearing and presumably acidic fluids. Fluid inclusions in fracture-filling quartz cements contain

Paleozoic and Lower Mesozoic magmas from the eastern Klamath Mountains (North California) and the geodynamic evolution of northwestern America

NASA Astrophysics Data System (ADS)

Lapierre, H.; Brouxel, M.; Albarede, F.; Coulin, C.; Lecuyer, C.; Martin, P.; Mascle, G.; Rouer, O.

1987-09-01

The Paleozoic to Early Mesozoic geology of the eastern Klamath Mountains (N California) is characterized by three major magmatic events of Ordovician, Late Ordovician to Early Devonian, and Permo-Triassic ages. The Ordovician event is represented by a calc-alkalic island-arc sequence (Lovers Leap Butte sequence) developed in the vicinity of a continental margin. The Late Ordovician to Early Devonian event consists of the 430-480 Ma old Trinity ophiolite formed during the early development of a marginal basin, and a series of low-K tholeiitic volcanic suites (Lovers Leap Basalt—Keratophyre unit, Copley and Balaklala Formations) belonging to intraoceanic island-arcs. Finally, the Permo-Triassic event gave rise to three successives phases of volcanic activity (Nosoni, Dekkas and Bully Hill) represented by the highly differentiated basalt-to-rhyolite low-K tholeiitic series of mature island-arcs. The Permo-Triassic sediments are indicative of shallow to moderate depth in an open, warm sea. The geodynamic evolution of the eastern Klamath Mountains during Paleozoic to Early Mesozoic times is therefore constrained by the geological, petrological and geochemical features of its island-arcs and related marginal basin. A consistent plate-tectonic model is proposed for the area, consisting of six main stages: (1) development during Ordovician times of a calc-alkalic island-arc in the vicinity of a continental margin; (2) extrusion during Late Ordovician to Silurian times of a primitive basalt-andesite intraoceanic island-arc suite, which terminated with boninites, the latter suggest rifting in the fore-arc, followed by the breakup of the arc; (3) opening and development of the Trinity back-arc basin around 430-480 Ma ago; (4) eruption of the Balaklala Rhyolite either in the arc or in the fore-arc, ending in Early Devonian time with intrusion of the 400 Ma Mule Mountain stock; (5) break in volcanic activity from the Early Devonian to the Early Permian; and (6) development of

Origin and tectonic evolution of early Paleozoic arc terranes abutting the northern margin of North China Craton

NASA Astrophysics Data System (ADS)

Zhou, Hao; Pei, Fu-Ping; Zhang, Ying; Zhou, Zhong-Biao; Xu, Wen-Liang; Wang, Zhi-Wei; Cao, Hua-Hua; Yang, Chuan

2017-12-01

The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic.

Sedimentological characterization of flood-tidal delta deposits in the Sego Sandstone, subsidence analysis in the Piceance Creek Basin, and uranium-lead geochronology (NW Colorado, USA)

NASA Astrophysics Data System (ADS)

York, Carly C.

The Sego Sandstone located in western Colorado is a member of the Upper Cretaceous Mesaverde Group and is considered an analogue of the Canadian heavy oil sands. Deposition of the Sego Sandstone occurred during the Upper Campanian (~78 Ma) at the end of the Sevier Orogeny and the beginning of the Laramide Orogeny on the western edge of the Cretaceous Interior Seaway. Although regional studies have detailed time equivalent deposits in the Book Cliffs, UT, the tidally influenced and marginal marine lithofacies observed north of Rangely, CO are distinctly different from the dominately fluvial and tidally-influenced delta facies of Book Cliff outcrops to the southwest. This study characterized flood-tidal delta deposits within the Sego Sandstone, the subsidence history of the Upper Cretaceous sedimentary rocks within the present day Piceance Creek Basin in NW Colorado, and the detrital zircon signal and oldest depositional age of the Sego Sandstone. The goals of this study are to (i) identify relative controls on reservoir characteristics of marginal marine deposits, specifically in flood-tidal delta deposits; (ii) identify the possible mechanisms responsible for subsidence within the present day Piceance Creek Basin during the Late Cretaceous; and (iii) better constrain the provenance and maximum depositional age of the Sego Sandstone. In this study I compared grain size diameter, grain and cement composition, and the ratio of pore space/cement from thin sections collected in tidal, shoreface, and flood-tidal delta facies recognized along detailed measured stratigraphic sections. This analysis provides a detailed comparison between different depositional environments and resultant data showed that grain size diameter is different between tidal, shoreface, and flood-tidal delta facies. Identifying the subsidence mechanisms affecting the Piceance Creek Basin and sediment source of the Late Cretaceous sediments, on the other hand, is important for evaluation of controls

Shifting locus of carbonate sedimentation and the trajectory of Paleozoic pCO2

NASA Astrophysics Data System (ADS)

Husson, J. M.; Peters, S. E.

2016-12-01

The burial of calcium carbonate is a determinant of planetary habitability, dictated by CO2 input to the surface environment and rates of chemical weathering. An important source of CO2 is the metamorphism of carbon-bearing sediments, which is responsive to the locus of sedimentation. For example, deep sea sediments are prone to recycling as sea floor is consumed at convergent margins; by contrast, sediments deposited on continental crust can be stable for billions of years.The predominant feature in the empirical sedimentary rock record, as measured by Macrostrat (https://macrostrat.org) and global geological syntheses, is a step-wise increase in continental sedimentation at the Neoproterozoic-Paleozoic transition. Although early Paleozoic carbonate volumes are sufficient to account for a CO2 flux 5x greater than present, Proterozoic continental burial fluxes were likely below the modern estimate. This observation implies that most carbonate sedimentation in the Proterozoic took place on the deep sea floor. The establishment of persistent, widespread continental flooding during the Paleozoic shifted the locus of carbonate sedimentation to continental interiors. A major implication of this shift is that CO2 flux declined during the Paleozoic as carbonate-laden Precambrian seafloor was metamorphosed and recycled. This prediction is consistent with independent proxy records and our model for Phanerozoic carbonate burial. An important corollary is that as carbonate-rich Precambrian seafloor was progressively destroyed, the carbonate content of deep sea sediments decreased concordantly because Paleozoic continents effectively captured global alkalinity fluxes. This process culminated near the Permian/Triassic, with metamorphic CO2 flux at a Phanerozoic minimum and the global ocean uniquely unbuffered against acidification. Such a condition could enhance the environmental effects of transient CO2 injections. Because the mid-Mesozoic appearance of pelagic calcifiers and

Failure warning of hydrous sandstone based on electroencephalogram technique

NASA Astrophysics Data System (ADS)

Tao, Kai; Zheng, Wei

2018-06-01

Sandstone is a type of rock mass that widely exists in nature. Moisture is an important factor that leads to sandstone structural failure. The major failure assessment methods of hydrous sandstone at present cannot satisfy real-time and portability requirements, especially lacks of warning function. In this study, acoustic emission (AE) and computed tomography (CT) techniques are combined for real-time failure assessment of hydrous sandstone. Eight visual colors for warning are screened according to different failure states, and an electroencephalogram (EEG) experiment is conducted to demonstrate their diverse excitations of the human brain's concentration.

Stress-dependent permeability evolution in sandstones with anisotropic physical properties

NASA Astrophysics Data System (ADS)

Metz, V.; David, C.; Louis, L.; Rodriguez Rey, A.; Ruiz de Argandona, V. G.

2003-04-01

Fluid flow in reservoir rocks is strongly dependent on stress path and rock microstructure which may present a significant anisotropy. We present recent experimental data on the evolution of permeability with applied stress for three sandstones tested under triaxial conditions in the low confining pressure range (<10 MPa). Samples with diameter 40 mm and length 80 mm were cored in three orthogonal directions in blocks retrieved from quarries. One coring direction was perpendicular to the bedding plane whereas the other directions were arbitrarily chosen within the bedding plane. The selected rocks are the Bentheim sandstone (BNT), a quartz-rich cretaceous sandstone from Germany with 24% porosity, and two different varieties of a same jurassic formation in Northern Spain, the La Marina sandstone. The Yellow La Marina sandstone (YLM) with porosity 28% has a low cohesion and is the weathered form of the well-consolidated Grey La Marina sandstone (GLM) with porosity 17%. When loaded up to the failure stress, the more porous sandstones (BNT, YLM) exhibited a monotonic decrease of permeability even when the rock was dilating at deviatoric stresses close to the failure stress. On the other hand the permeability of the less porous sandstone (GLM) increased during the dilating phase. These results are in agreement with previous studies. In addition we observed that all three sandstones are anisotropic with respect to several physical properties including permeability. We systematically found a lower permeability in the direction perpendicular to the bedding plane, but the ratio of "vertical" to "horizontal" permeability varies from one sandstone to the other. The permeability anisotropy is compared to the anisotropy of electrical conductivity, acoustic velocity, capillary imbibition and elastic moduli: in general good correlations are found for all the properties. For the Bentheim sandstone, a microstructural study on thin sections revealed that the rock anisotropy is due

Paleozoic strata of the Dyckman Mountain area, northeastern Medfra quadrangle, Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1998

USGS Publications Warehouse

Dumoulin, Julie A.; Bradley, Dwight C.; Harris, Anita G.

2000-01-01

Paleozoic rocks in the Dyckman Mountain area (northeastern Medfra quadrangle; Farewell terrane) include both shallowand deep-water lithologies deposited on and adjacent to a carbonate platform. Shallow-water strata, which were recognized by earlier workers but not previously studied in detail, consist of algal-laminated micrite and skeletal-peloidal wackestone, packstone, and lesser grainstone. These rocks are, at least in part, of Early and (or) Middle Devonian age but locally could be as old as Silurian; they accumulated in shallow subtidal to intertidal settings with periodically restricted water circulation. Deepwater facies, reported here for the first time, are thin, locally graded beds of micrite and calcisiltite and subordinate thick to massive beds of lime grainstone and conglomerate. Conodonts indicate an age of Silurian to Middle Devonian; the most tightly dated intervals are early Late Silurian (early to middle Ludlow). These strata formed as hemipelagic deposits, turbidites, and debris flows derived from shallow-water lithologies of the Nixon Fork subterrane. Rocks in the Dyckman Mountain area are part of a broader facies belt that is transitional between the Nixon Fork carbonate platform to the west and deeper water, basinal lithologies (Minchumina “terrane”) to the east. Transitional facies patterns are complex because of Paleozoic shifts in the position of the platform margin, Mesozoic shortening, and Late Cretaceous-Tertiary disruption by strike-slip faulting.

Geology of the Gateway quadrangle, Mesa county Colorado

USGS Publications Warehouse

Cater, Fred W.

1953-01-01

The Gateway quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as "Uruvan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Anderson Mesa quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.; Withington, C.F.

1953-01-01

The Anderson Mesa quadrangle is one of the eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of the southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteenth quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quarternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-tending folds. Conspicuous among the folds are large anticlines having cores of intrusive slat and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing many thousands of tons. The ore consists of largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Egnar quadrangle, Dolores and San Miguel counties, Colorado

USGS Publications Warehouse

Cater, Fred W.; Bush, A.L.; Bell, Henry

1954-01-01

The Egnar quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as "Uruvan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Hamm Canyon quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.

1953-01-01

The Hamm Canyon quadrangle is on eof eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Davis Mesa quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.; Bryner, Leonid

1953-01-01

The Davis Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as "Uruvan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Joe Davis Hill quadrangle, Dolores and San Miguel counties, Colorado

USGS Publications Warehouse

Cater, Fred W.; Bell, Henry

1953-01-01

The Joe Davis Hill quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Gypsum Gap quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.

1953-01-01

The Gypsum Gap quadrangle is one eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comparative study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through a arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The core consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Calamity Mesa quadrangle, Mesa county, Colorado

USGS Publications Warehouse

Cater, Fred W.; Stager, Harold K.

1953-01-01

The Calamity Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks the range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Horse Range Mesa quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.; Bush, A.L.; Bell, Henry; Withington, C.F.

1953-01-01

The Horse Range Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of the quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary strictures in sandstones of favorable composition.

Geology of Bull Canyon quadrangle, Montrose and San Miguel counties, Colorado

USGS Publications Warehouse

Cater, Fred W.

1953-01-01

The Bull Canyon quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite depots. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tones. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Geology of the Uravan quadrangle, Montrose county, Colorado

USGS Publications Warehouse

Cater, Fred W.; Butler, A.P.; McKay, E.J.; Boardman, Robert L.

1954-01-01

The Uravan quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of the southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to the related to certain sedimentary structures in sandstones of favorable composition.

Depositional environment of downdip Yegua (Eocene) sandstones, Jackson County, Texas

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

Whitten, C.J.; Berg, R.R.

Yegua sandstones at a depth of 8300-8580 ft (2530-2615 m) were partly cored in the Arco Jansky 1 dry hole. Total thickness of the sandstone section is approximately 240 ft (73 m). The sandstones are enclosed in thick marine shales and are about 20 mi (32 km) downdip from thicker and more abundant sandstones in the Yegua Formation. The section is similar to reservoirs recently discovered in the area at the Toro Grande (1984), Lost Bridge (1984), and El Torito (1985) fields. The sandstones are fine to very fine grained and occur in thin beds that are 0.5-9 ft (0.15-2.7more » m) thick. Sedimentary structures within the beds range from a lower massive division to a laminated or rippled upper division. Grain size within beds fines upward from 0.18 mm at the base to 0.05 mm at the top. The sandstones are interpreted to be turbidites of the AB type that were deposited within channels. The sandstones contain an average of 50% quartz and are classified as volcanic-arenites to feldspathic litharenites. Carbonate cement ranges from 0 to 27%. Average porosity is 29% and permeabilities are in the range of 60-1600 md in the clean sandstones. Much of the porosity is secondary and is the result of the dissolution of cements, volcanic rock fragments, and feldspar grains. Yegua sandstones produce gas and condensate at nearby Toro Grande field on a gentle, faulted anticline. The local trend of reservoir sandstones may be controlled in part by faulting that was contemporaneous with deposition.« less

Soft-sediment deformation structures from an ice-marginal storm-tide interactive system, Permo-Carboniferous Talchir Formation, Talchir Coalbasin, India

NASA Astrophysics Data System (ADS)

Bhattacharya, H. N.; Bhattacharya, Biplab

2010-01-01

Permo-Carboniferous Talchir Formation, Talchir Coalbasin, India, records sedimentation during a phase of climatic amelioration in an ice-marginal storm-affected shelf. Evidences of subtidal processes are preserved only under thick mud drapes deposited during waning storm phases. Various soft-sediment deformation structures in some sandstone/siltstone-mudstone interbeds, like syn-sedimentary faults, deformed laminations, sand-silt flows, convolute laminations and various flame structures, suggest liquefaction and fluidization of the beds due to passage of syn-depositional seismic shocks. In the Late Paleozoic ice-marginal shelf, such earthquake tremors could be generated by crustal movements in response to glacioisostatic adjustments of the basin floor.

Quantitative petrographic analysis of Desmoinesian sandstones from Oklahoma

USGS Publications Warehouse

Dyman, Thaddeus S.

1989-01-01

Desmoinesian sandstones from the northern Oklahoma platform and the Anadarko, Arkoma, and Ardmore basins record a complex interaction between mid-Pennsylvanian source-area tectonism and cyclic sedimentation patterns associated with numerous transgressions and regressions. Framework-grain summaries for 50 thin sections from sandstones of the Krebs, Cabaniss, and Marmaton Groups and their surface and subsurface equivalents were subjected to multivariate statistical analyses to establish regional compositional trends for provenance analysis. R-mode cluster and correspondence analyses were used to determine the contributing effect (total variance) of key framework grains. Fragments of monocrystalline and polycrystalline quartz; potassium and plagioclase feldspar; chert; and metamorphic, limestone, and mudstone-sandstone rock fragments contribute most to the variation in the grain population. Q-mode cluster and correspondence analyses were used to identify four petrofacies and establish the range of compositional variation in Desmoinesian sandstones. Petrofacies I is rich in monocrystalline quartz (78-98%); mica and rock fragments are rare. Petrofacies II is also rich in monocrystalline quartz (60-84%) and averages 12% total rock fragments. Petrofacies III and IV are compositionally heterogeneous and contain variable percentages of monocrystalline and polycrystalline quartz, potassium feldspar, mica, chert, and metamorphic and sedimentary rock fragments. Quantitative analyses indicate that Desmoinesian sandstones were derived from sedimentary, igneous, and metamorphic source areas. Sandstones of petrofacies I and II occur mostly in the lower Desmoinesian and are widely distributed, although they are most abundant in eastern and central Oklahoma; sandstones of petrofacies III and IV are widely distributed and occur primarily in the middle and upper Desmoinesian. The range of compositional variation and the distribution of petrofacies are related to paleotectonics and

Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

NASA Astrophysics Data System (ADS)

Hyppolito, T.; García-Casco, A.; Juliani, C.; Meira, V. T.; Hall, C.

2014-10-01

by the non-coaxial exhumation-related foliation S2. During exhumation and retrograde D2 deformation, the garnet-mica schist and amphibolite were tectonically mingled at a depth of ca. 30 km at ca. 315 Ma. We propose that the Punta Sirena unit comprises a “pseudo”-coherent sequence formed by heterogeneous lithologies that followed non-chaotic exhumation mingling, now representing the remnants of the fossil subduction channel developed at the onset of the Late Paleozoic subduction at central Chile.

Age and provenance constraints on seismically-determined crustal layers beneath the Paleozoic southern Central Asian Orogen, Inner Mongolia, China

NASA Astrophysics Data System (ADS)

Jian, Ping; Kröner, Alfred; Shi, Yuruo; Zhang, Wei; Liu, Yaran; Windley, Brian F.; Jahn, Bor-ming; Zhang, Liqao; Liu, Dunyi

2016-06-01

We present 110 ages and 51 in-situ δ18O values for zircon xenocrysts from a post-99 Ma intraplate basaltic rock suite hosted in a subduction-accretion complex of the southern Central Asian Orogenic Belt in order to constrain a seismic profile across the Paleozoic Southern Orogen of Inner Mongolia and the northern margin of the North China Craton. Two zircon populations are recognized, namely a Phanerozoic group of 70 zircons comprising granitoid-derived (ca. 431-99 Ma; n = 31; peak at 256 Ma), meta-granitoid-derived (ca. 449-113 Ma; n = 24; peak at 251 Ma) and gabbro-derived (436-242 Ma; n = 15; peaks at 264 and 244 Ma) grains. Each textural type is characterized by a distinct zircon oxygen isotope composition and is thus endowed with a genetic connotation. The Precambrian population (2605-741 Ma; n = 40) exhibits a prominent age peak at 2520 Ma (granulite-facies metamorphism) and four small peaks at ca. 1900, 1600, and 800 Ma. Our new data, together with literature zircon ages, significantly constrain models of three seismically-determined deep crustal layers beneath the fossil subduction zone-forearc along the active northern margin of the North China Craton, namely: (1) an upper arc crust of early to mid-Paleozoic age, intruded by a major Permian-Triassic composite granitoid-gabbroic pluton (8-20 km depth); (2) a middle crust, predominantly consisting of mid-Meso- to Neoproterozoic felsic and mafic gneisses; and (3) a lower crust composed predominantly of late Archean granulite-facies rocks. We conclude that the Paleozoic orogenic crust is limited to the upper crustal level, and the middle to lower crust has a North China Craton affinity. Furthermore, integrating our data with surface geological, petrological and geochronological constraints, we present a new conceptual model of orogenic uplift, lithospheric delamination and crustal underthrusting for this key ocean-continent convergent margin.

Experimental study on the CO2-flow mechanism in the two different sandstones

NASA Astrophysics Data System (ADS)

Imasato, M.; Honda, H.; Kitamura, K.

2016-12-01

It is important to discuss the flow properties of CO2 in the reservoir for estimations of storage potential and safety of CCS operation. In this study, we conducted the CO2-injection tests into two different types of porous sandstones with extremely low CO2 flow rate (10µl/min) under supercritical CO2 conditions. It was measured CO2 saturation (SCO2) and differential pressure (ΔP) between upstream and downstream of specimen. It was also monitored P-wave velocity (Vp) and electrical impedance (Z) for the monitoring of CO2 behavior in the specimen. We set three Vp measurement lines in different height for monitoring the movement of CO2 front. The results of ΔP measurement indicated that the Berea sandstone showed no obvious change, but the Ainoura sandstone was increasing gradually and peaked in 73 hours. After that, ΔP of the Ainoura sandstone started reducing. Both sandstones showed stepwise Vp-reduction from the bottom Vp-measurement line, which is near CO2 injection end. There are large differences of CO2 arrival time at the bottom line between Berea and Ainoura sandstone. In case of Ainoura sandstone, it took 29 hours to reduce Vp which is the nearest to CO2 injection end, but in case of Berea sandstone, it took 3.3 hours. This is also confirmed the arrival time at the top channel, 2.5 hours in the Berea sandstone and 11 hours in the Ainoura sandstone. The impedances of both sandstones indicted the gradual increment. It took 25 hours to become constant in the Berea sandstone and 148 hours in the Ainoura sandstone. SCO2 of the Berea sandstone was about 6% and Ainoura sandstone reached over 20%. These results suggest that it is due to the difference of the pore structure of Berea sandstone and Ainoura sandstone.

Paleozoic Orogens of Mexico and the Laurentia-Gondwana Connections: an Update

NASA Astrophysics Data System (ADS)

Ortega-Gutierrez, F.

2009-05-01

The present position of Mexico in North America and the fixist tectonic models that prevailed prior to the seventies of the past century, have considered the main Paleozoic tectonic systems of Mexico as natural extensions of the orogens that fringed the eastern and southern sides of the Laurentian craton. Well known examples of pre-Mesozoic orogens in Mexico are the Oaxacan, Acatlan, and Chiapas polymetamorphic terranes, which have been correlated respectively with the Grenville and Appalachian-Ouachitan orogens of eastern North America. Nonetheless, several studies conducted during the last decade in these Mexican orogenic belts, have questioned their Laurentian connections, regarding northwestern Gondwana instead as the most plausible place for their birth and further tectonic evolution. This work pretends to approach the problem by briefly integrating the massive amount of new geological information, commonly generated through powerful dating methods such as LA-ICPM-MS on detrital zircon of sedimentary and metasedimentary units in the Paleozoic crustal blocks, which are widely exposed in southern and southeastern Mexico. The Acatlan Complex bears the closest relationships to the Appalachian orogenic system because it shows thermotectonic evidence for opening and closure of the two main oceans involved in building the Appalachian mountains in eastern Laurentia, whereas two other Paleozoic terranes in NW and SE Mexico, until recently rather geologically unknown, may constitute fundamental links between the Americas for the last-stage suturing and consolidation of western Pangea. The buried basement of the Yucatan platform (400,000 squared km) on the other hand, remains as one of the most relevant problems of tectonostratigraphic correlations across the Americas, because basement clasts from the Chicxulub impact ejecta reveal absolute and Nd-model ages that suggest close Gondwanan affinities. Major changes in the comprehension of the Paleozoic orogens in Mexico

Contrasting sources of Late Paleozoic rhyolite magma in the Polish Lowlands: evidence from U-Pb ages and Hf and O isotope composition in zircon

NASA Astrophysics Data System (ADS)

Słodczyk, Elżbieta; Pietranik, Anna; Glynn, Sarah; Wiedenbeck, Michael; Breitkreuz, Christoph; Dhuime, Bruno

2018-02-01

The Polish Lowlands, located southwest of the Teisseyre-Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly rhyolitic, magmatism during the Late Paleozoic. Thanks to the inherited zircon they contain, these rhyolitic rocks provide a direct source of information about the pre-Permian rocks underlying the Polish Lowland. This paper presents zircon U-Pb geochronology and Hf and O isotopic results from five drill core samples representing four rhyolites and one granite. Based on the ratio of inherited vs. autocrystic zircon, the rhyolites can be divided into two groups: northern rhyolites, where autocrystic zircon is more abundant and southern rhyolites, where inherited zircon dominates. We suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites. Isotopically distinct sources were available during formation of northern rhyolites, as the Hf and O isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites. A mixing between magmas formed from Baltica-derived mudstone-siltstone sediments and Avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities Daszewo and Wysoka Kamieńska. Conversely, the southern rhyolites from our two localities contain zircon with similar compositions, and these units can be further correlated with results from the North East German Basin, suggesting uniform source rocks over this larger region. Based on the ages of inherited zircon and the isotopic composition of magmatic ones, we suggest that the dominant source of the southern rhyolites is Variscan foreland sediments mixed with Baltica/Avalonia-derived sediments.

Geologic map of the Nelson quadrangle, Lewis and Clark County, Montana

USGS Publications Warehouse

Reynolds, Mitchell W.; Hays, William H.

2003-01-01

The geologic map of the Nelson quadrangle, scale 1:24,000, was prepared as part of the Montana Investigations Project to provide new information on the stratigraphy, structure, and geologic history of an area in the geologically complex southern part of the Montana disturbed belt. In the Nelson area, rocks ranging in age from Middle Proterozoic through Cretaceous are exposed on three major thrust plates in which rocks have been telescoped eastward. Rocks within the thrust plates are folded and broken by thrust faults of smaller displacement than the major bounding thrust faults. Middle and Late Tertiary sedimentary and volcaniclastic rocks unconformably overlie the pre-Tertiary rocks. A major normal fault displaces rocks of the western half of the quadrangle down on the west with respect to strata of the eastern part. Alluvial and terrace gravels and local landslide deposits are present in valley bottoms and on canyon walls in the deeply dissected terrain. Different stratigraphic successions are exposed at different structural levels across the quadrangle. In the northeastern part, strata of the Middle Cambrian Flathead Sandstone, Wolsey Shale, and Meagher Limestone, the Middle and Upper Cambrian Pilgrim Formation and Park Shale undivided, the Devonian Maywood, Jefferson, and lower part of the Three Forks Formation, and Lower and Upper Mississippian rocks assigned to the upper part of the Three Forks Formation and the overlying Lodgepole and Mission Canyon Limestones are complexly folded and faulted. These deformed strata are overlain structurally in the east-central part of the quadrangle by a succession of strata including the Middle Proterozoic Greyson Formation and the Paleozoic succession from the Flathead Sandstone upward through the Lodgepole Limestone. In the east-central area, the Flathead Sandstone rests unconformably on the middle part of the Greyson Formation. The north edge, northwest quarter, and south half of the quadrangle are underlain by a

Birth, life, and demise of the Andean-syn-collisional Gissar arc: Late Paleozoic tectono-magmatic-metamorphic evolution of the southwestern Tian Shan, Tajikistan

NASA Astrophysics Data System (ADS)

Worthington, James R.; Kapp, Paul; Minaev, Vladislav; Chapman, James B.; Mazdab, Frank K.; Ducea, Mihai N.; Oimahmadov, Ilhomjon; Gadoev, Mustafo

2017-10-01

The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum-Tarim and Kazakh-Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modeling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith ( 21-7 km) to arc-root ( 36-19 km) levels of the Andean-syn-collisional Gissar arc, which developed from 323-288 Ma in two stages: (i) Andean, I-type granitoid magmatism from 323-306 Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by (ii) syn-collisional, I-S-type granitoid magmatism in the Gissar batholith and the Garm massif from 304-288 Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from 288-286 Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by 280 Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M-HT/LP prograde metamorphism in the Garm massif (650-750°C/6-7 kbar) from 310-288 Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures ( 800-820°C/6-4 kbar) at 288 ± 6 Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.

Timing of the Late Paleozoic Ice Age: A Review of the Status Quo and New U-Pb Zircon Ages From Southern Gondwana

NASA Astrophysics Data System (ADS)

Mundil, R.; Griffis, N. P.; Keller, C. B.; Fedorchuk, N.; Montanez, I. P.; Isbell, J.; Vesely, F.; Iannuzzi, R.

2017-12-01

Throughout the Carboniferous and Permian Late Paleozoic Ice Age (LPIA), glaciations in southern Gondwana exerted a profound influence on global climate and environment, ocean chemistry, and the nature of sedimentary processes. The LPIA is widely regarded as an analogue for Pleistocene glaciations. Our understanding of the latter, as well as the validity of predictions for the future global climate and environment, depends therefore on our ability to reconstruct the LPIA. A robust chronostratigraphic framework built on high precision/high accuracy geochronology is crucial for the reconstruction of events and processes that occurred during the LPIA, particularly in the absence of high-resolution terrestrial biostratigraphic constraints that apply to both near- and far-field proxy records. The occurrence of volcaniclastic layers containing primary volcanic zircon at many levels throughout southern Gondwana makes such a reconstruction feasible, but complications inevitably arise due to the mixing of older age components with primary volcanic crystals, as well as the potential of unrecognized open system behavior to produce spurious younger ages. These pitfalls cause age dispersion that may be difficult to interpret, or is unrecognized if low precision geochronological techniques are used, resulting in inaccurate radioisotopic ages. Our current efforts in the Parana Basin (Southern Brazil) and the Karoo Basin (South Africa/Namibia) concentrate on building a robust and exportable chronostratigraphic framework based on U-Pb zircon CA-TIMS ages with sub-permil level precision combined with Bayesian approaches for resolving the eruption age of dispersed age spectra to facilitate the reconstruction of glaciogenic processes through the Carboniferous-Permian transition, as well as their implications for global sea level, atmospheric pCO2 and ocean chemistry. We will also review currently available geochronological data from contemporaneous Australian successions and their

Sensing, Measuring and Modelling the Mechanical Properties of Sandstone

NASA Astrophysics Data System (ADS)

Antony, S. J.; Olugbenga, A.; Ozerkan, N. G.

2018-02-01

We present a hybrid framework for simulating the strength and dilation characteristics of sandstone. Where possible, the grain-scale properties of sandstone are evaluated experimentally in detail. Also, using photo-stress analysis, we sense the deviator stress (/strain) distribution at the micro-scale and its components along the orthogonal directions on the surface of a V-notch sandstone sample under mechanical loading. Based on this measurement and applying a grain-scale model, the optical anisotropy index K 0 is inferred at the grain scale. This correlated well with the grain contact stiffness ratio K evaluated using ultrasound sensors independently. Thereafter, in addition to other experimentally characterised structural and grain-scale properties of sandstone, K is fed as an input into the discrete element modelling of fracture strength and dilation of the sandstone samples. Physical bulk-scale experiments are also conducted to evaluate the load-displacement relation, dilation and bulk fracture strength characteristics of sandstone samples under compression and shear. A good level of agreement is obtained between the results of the simulations and experiments. The current generic framework could be applied to understand the internal and bulk mechanical properties of such complex opaque and heterogeneous materials more realistically in future.

Elevated Uranium in Aquifers of the Jacobsville Sandstone

NASA Astrophysics Data System (ADS)

Sherman, H.; Gierke, J.

2003-12-01

The EPA has announced a new standard for uranium in drinking water of 30 parts per billion (ppb). This maximum contaminant level (MCL) takes effect for community water supplies December 2003. The EPA's ruling has heightened awareness among residential well owners that uranium in drinking water may increase the risk of kidney disease and cancer and has created a need for a quantified, scientific understanding of the occurrence and distribution of uranium isotopes in aquifers. The authors are investigating the occurrence of elevated uranium in northern Michigan aquifers of the Middle Proterozoic Jacobsville sandstone, a red to mottled sequence of sandstones, conglomerates, siltstones and shales deposited as basin fill in the 1.1 Ga Midcontinent rift. Approximately 25% of 300 well water samples tested for isotopic uranium have concentrations above the MCL. Elevated uranium occurrences are distributed throughout the Jacobsville sandstone aquifers stretching across Michigan's Upper Peninsula. However, there is significant variation in well water uranium concentrations (from 0.01 to 190 ppb) and neighboring wells do not necessarily have similar concentrations. The authors are investigating hydrogeologic controls on ground water uranium concentrations in the Jacobsville sandstone, e.g. variations in lithology, mineralogy, groundwater residence time and geochemistry. Approximately 2000' of Jacobsville core from the Amoco St. Amour well was examined in conjunction with the spectral gamma ray log run in the borehole. Spikes in equivalent uranium (eU) concentration from the log are frequently associated with clay and heavy mineral layers in the sandstone core. The lithology and mineralogy of these layers will be determined by analysis of thin sections and x-ray diffraction. A portable spectrometer, model GRS-2000/BL, will be used on the sandstone cliffs along Lake Superior to characterize depositional and lithologic facies of the Jacobsville sandstone in terms of

Sandstone provenance and tectonic evolution of the Xiukang Mélange from Neotethyan subduction to India-Asia collision (Yarlung-Zangbo suture, south Tibet)

NASA Astrophysics Data System (ADS)

An, Wei; Hu, Xiumian; Garzanti, Eduardo

2016-04-01

blocks were derived from the central Lhasa block and Gangdese magmatic arc. One group was deposited in the trench and/or on the trench slope of the Asian margin during the early Late Cretaceous, and the other group in a syn-collisional basin just after the onset of the India-Asia collision in the Early Eocene. The largely erosional character of the Asian active margin in the Late Cretaceous is indicated by the scarcity of off-scraped trench-fill deposits and the relatively small subduction complex developed during limited episodes of accretion. The Xiukang Mélange was finally structured in the Late Paleocene/Eocene, when sandstone of both Indian and Asian origin were progressively incorporated tectonically in the suture zone of the nascent Himalayan Orogen.

Transport of silver nanoparticles in single fractured sandstone

NASA Astrophysics Data System (ADS)

Neukum, Christoph

2018-02-01

Silver nanoparticles (Ag-NP) are used in various consumer products and are one of the most prevalent metallic nanoparticle in commodities and are released into the environment. Transport behavior of Ag-NP in groundwater is one important aspect for the assessment of environmental impact and protection of drinking water resources in particular. Ag-NP transport processes in saturated single-fractured sandstones using triaxial flow cell experiments with different kind of sandstones is investigated. Ag-NP concentration and size are analyzed using flow field-flow fractionation and coupled SEM-EDX analysis. Results indicate that Ag-NP are more mobile and show generally lower attachment on rock surface compared to experiments in undisturbed sandstone matrix and partially fractured sandstones. Ag-NP transport is controlled by the characteristics of matrix porosity, time depending blocking of attachment sites and solute chemistry. Where Ag-NP attachment occur, it is heterogeneously distributed on the fracture surface.

Stratigraphic comparison of six oil fields (WV) producing from Big Injun sandstones

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

Zou, X.; Donaldson, A.C.

1993-08-01

Clustered within western West Virginia, six oil fields produce from the lower Mississippian Big Injun sandstones, and three more oil fields also supplement this production either from underlying Squaw or Weir sandstones. Shales separate these sandstones that occur stratigraphically between the Sunbury Shale (maximum flooding surface) and pre-Greenbrier unconformity (maximum regressive erosional surface), and represent highstand regressive deposits associated with the postorogenic phase of foreland basin accumulation. Stratigraphic studies show two Big Injun sandstones. The upper sandstone, called the Maccrady Big Injun, is separated from the lower Price/Pocono Big Injun sandstone by red shales. Both Big Injun sandstones consist ofmore » fine-grained river-mouth bars capped by coarse-grained river-channel deposits. Although the six fields are within three adjacent counties, Maccrady Big Injun sandstones of Blue Creek (Kanawha) and Rock Creek (Roane) fields are younger and were deposited by a different fluvial-deltaic system than the Price/Pocono Big Injun sandstones of Granny Creek (Clay), Tariff (Roane) Clendenin (Clay), and Pond Fork (Kanawha) fields. Upper Weir sandstones are thick, narrow north-trending belts underlying Pond Fork and Blue Creek fields, with properties suggesting wave-dominated shoreline deposits. Allocycles spanning separate drainage systems indicate eustasy. Postorogenic flexural adjustments probably explain stacked sandstone belts with superposed paleovalleys of overlying unconformities (pre-Greenbrier, Pottsville), particularly where aligned along or parallel basement structures of Rome trough or West Virginia dome. Initially, differential subsidence or uplift during sedimentation influenced the position, geometry, trend, and distribution patterns of these reservoir sandstone, then influenced their preserved condition during erosion of pre-Greenbrier unconformity.« less

Timing of crust formation and recycling in accretionary orogens: Insights learned from the western margin of South America

NASA Astrophysics Data System (ADS)

Bahlburg, Heinrich; Vervoort, Jeffrey D.; Du Frane, S. Andrew; Bock, Barbara; Augustsson, Carita; Reimann, Cornelia

2009-12-01

Accretionary orogens are considered major sites of formation of juvenile continental crust. In the central and southern Andes this is contradicted by two observations: siliciclastic fills of Paleozoic basins in the central Andean segment of the accretionary Terra Australis Orogen consist almost exclusively of shales and mature sandstones; and magmatic rocks connected to the Famatinian (Ordovician) and Late Paleozoic magmatic arcs are predominantly felsic and characterized by significant crustal contamination and strongly unradiogenic Nd isotope compositions. Evidence of juvenile crustal additions is scarce. We present laser ablation (LA)-ICPMS U-Pb ages and LA-MC-ICPMS Hf isotope data of detrital zircons from seven Devonian to Permian turbidite sandstones incorporated into a Late Paleozoic accretionary wedge at the western margin of Gondwana in northern Chile. The combination with Nd whole-rock isotope data permits us to trace the evolution of the South American continental crust through several Proterozoic and Paleozoic orogenic cycles. The analyzed detrital zircon spectra reflect all Proterozoic orogenic cycles representing the step-wise evolution of the accretionary SW Amazonia Orogenic System between 2.0 and 0.9 Ga, followed by the Terra Australis Orogen between 0.9 and 0.25 Ga. The zircon populations are characterized by two prominent maxima reflecting input from Sunsas (Grenville) age magmatic rocks (1.2-0.9 Ga) and from the Ordovician to Silurian Famatinian magmatic arc (0.52-0.42 Ga). Grains of Devonian age are scarce or absent from the analyzed zircon populations. The Hf isotopic compositions of selected dated zircons at the time of their crystallization ( ɛHf ( T) ; T = 3.3-0.25 Ga) vary between - 18 and + 11. All sandstones have a significant juvenile component; between 20 and 50% of the zircons from each sedimentary rock have positive ɛHf ( T) and can be considered juvenile. The majority of the juvenile grains have Hf-depleted mantle model ages (Hf

Fluvial sandstone reservoirs of Travis Peak (Hosston) Formation, east Texas basin

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

Tye, R.S.

1989-03-01

Gas production (7.2 billion ft/sup 3/) from low-permeability sandstones in the Travis Peak Formation, North Appleby field, Nacogdoches County, Texas, is enhanced through massive hydraulic fracturing of stacked sandstones that occur at depths between 8000 and 10,000 ft. stratigraphic reservoirs were formed in multilateral tabular sandstones owing to impermeable mudstone interbeds that encase blocky to upward-fining sandstones. Pervasive quartz cement in the sandstones decreases porosity and permeability and augments the reservoir seal. Subsurface data indicate that much of this 2000-ft thick section represents aggradation of alluvial-valley deposits. Multiple channel belts form a network of overlapping, broad, tabular sandstones having thickness-to-widthmore » ratios of 1:850 (8-44 ft thick; widths exceed 4-5 mi). Six to eight channel belts, each containing 80-90% medium to fine-grained sandstone, can occupy a 200-ft thick interval. In a vertical sequence through one channel belt sandstone, basal planar cross-bedding grades upward into thinly interbedded sets of planar cross-beds and ripple cross-lamination. Clay-clast conglomerates line scoured channel bases. Adjacent to the channels, interbedded mudstones accumulated in well-drained swamps and lakes. Poorly sorted sandstones represent overbank deposition (crevasse splays and lacustrine deltas). During Travis Peak deposition, fluvial styles evolved from dominantly braided systems near the base of the formation to more mud-rich, meandering systems at the top.« less

Extensional Late Paleozoic deformation on the western margin of Pangea, Patlanoaya area, Acatlán Complex, southern Mexico

NASA Astrophysics Data System (ADS)

Ramos-Arias, M. A.; Keppie, J. D.; Ortega-Rivera, A.; Lee, J. W. K.

2008-02-01

New mapping in the northern part of the Paleozoic Acatlán Complex (Patlanoaya area) records several ductile shear zones and brittle faults with normal kinematics (previously thought to be thrusts). These movement zones separate a variety of units that pass structurally upwards from: (i) blueschist-eclogitic metamorphic rocks (Piaxtla Suite) and mylonitic megacrystic granites (Columpio del Diablo granite ≡ Ordovician granites elsewhere in the complex); (ii) a gently E-dipping, listric, normal shear zone with top to the east kinematic indicators that formed under upper greenschist to lower amphibolite conditions; (iii) the Middle-Late Ordovician Las Minas quartzite (upper greenschist facies psammites with minor interbedded pelites intruded by mafic dikes and a leucogranite dike from the Columpio del Diablo granite) unconformably overlain by the Otate meta-arenite (lower greenschist facies psammites and pelites): roughly temporal equivalents are the Middle-Late Ordovician Mal Paso and Ojo de Agua units (interbedded metasandstone and slate, and metapelite and mafic minor intrusions, respectively) — some of these units are intruded by the massive, 461 ± 2 Ma, Palo Liso megacrystic granite: decussate, contact metamorphic muscovite yielded a 40Ar/ 39Ar plateau age of 440 ± 4 Ma; (iv) a steeply-moderately, E-dipping normal fault; (v) latest Devonian-Middle Permian sedimentary rocks (Patlanoaya Group: here elevated from formation status). The upward decrease in metamorphic grade is paralleled by a decrease in the number of penetrative fabrics, which varies from (i) three in the Piaxtla Suite, through (ii) two in the Las Minas unit (E-trending sheath folds deformed by NE-trending, subhorizontal folds with top to the southeast asymmetry, both associated with a solution cleavage), (iii) one in the Otate, Mal Paso, and Ojo de Agua units (steeply SE-dipping, NE-SW plunging, open-close folds), to (iv) none in the Patlanoaya Group. 40Ar/ 39Ar analyses of muscovite from the

Early Paleozoic subduction initiation volcanism of the Iwatsubodani Formation, Hida Gaien belt, Southwest Japan

NASA Astrophysics Data System (ADS)

Tsukada, Kazuhiro; Yamamoto, Koshi; Gantumur, Onon; Nuramkhaan, Manchuk

2017-06-01

In placing Japanese tectonics in an Asian context, variation in the Paleozoic geological environment is a significant issue. This paper investigates the geochemistry of the lower Paleozoic basalt formation (Iwatsubodani Formation) in the Hida Gaien belt, Japan, to consider its tectonic setting. This formation includes the following two types of rock in ascending order: basalt A with sub-ophitic texture and basalt B with porphyritic texture. Basalt A has a high and uniform FeO*/MgO ratio, moderate TiO2, high V, and low Ti/V. The HFSE and REE are nearly the same as those in MORB, and all the data points to basalt A being the "MORB-like fore-arc tholeiitic basalt (FAB)" reported, for example, from the Izu-Bonin-Mariana arc. By contrast, basalt B has a low FeO*/MgO ratio, low TiO2, and low V and Ti/V. It has an LREE-enriched trend and a distinct negative Nb anomaly in the MORB-normalized multi-element pattern and a moderately high LREE/HREE. All these factors suggest that basalt B is calc-alkaline basalt. It is known that FAB is erupted at the earliest stage of arc formation—namely, subduction initiation—and that boninitic/tholeiitic/calc-alkaline volcanism follows at the supra-subduction zone (SSZ). Thus, the occurrence of basalts A (FAB) and B (calc-alkaline rock) is strong evidence of early Paleozoic arc-formation initiation at an SSZ. Evidence for an early Paleozoic SSZ arc is also recognized from the Oeyama, Hayachine-Miyamori, and Sergeevka ophiolites. Hence, both these ophiolites and the Iwatsubodani Formation probably coexisted in a primitive SSZ system in the early Paleozoic.

Trace fossils and sedimentary facies from a Late Cambrian‐Early Ordovician tide‐dominated shelf (Santa Rosita Formation, northwest Argentina): Implications for ichnofacies models of shallow marine successions

USGS Publications Warehouse

Mángano, M. Gabriela; Buatois, Luis A.; Aceñolaza, Guillermo F.

1996-01-01

The Santa Rosita Formation is one the most widely distributed lower Paleozoic units of northwest Argentina. At the Quebrada del Salto Alto section, east of Purmamarca, Jujuy Province, it is represented by four sedimentary facies: thick‐bedded planar cross‐stratified quartzose sandstones (A), thin‐bedded planar cross‐stratified quartzose sandstones and mudstones (B), wave‐rippled sandstones and bioturbated mudstones (C), and black and greenish gray shales (D). Paleocurrent data, sandstone architecture, and sedimentary structures from faciès A and B indicate bipolar/bimodal paleoflows, suggesting the action of tidal currents. The succession is interpreted as that of a tide‐dominated shelf, with only secondary influence of wave processes. Trace fossils are restricted to facies B and C.The Cruziana ichnocoenosis is preserved on the soles of thin‐bedded planar cross‐stratified quartzose sandstones (faciès B). This ichnocoenosis consists of Conostichus isp., Cruziana omanica, C. semiplicata, C. cf. tortworthi, Cruziana isp. Helminthopsis abeli, Monomorphichnus bilinearis, M. multilineatus, Palaeophycus tubularis, Rusophycus carbonarias, R. latus, and R. isp. The occurrence of Cruziana semiplicata, C. omanica, C. cf. tortworthi, and Rusophycus latus supports a Late Cambrian‐Tremadoc age. Slabbing of Cruziana shows complex interactions between biologic and sedimentologic processes, and suggests a predominance of exhumed traces, washed out and recast by tractive sand deposition. Sandstone soles are densely packed with biogenic structures and exhibit distinctive clusters of Rusophycus isp. that most likely represent trilobite nesting burrows. The Cruziana ichnocoenosis records the resident fauna of a protected, lower intertidal to subtidal interbar setting.The Skolithos ichnocoenosis is represented by high to low density vertical burrows of Skolithos linearis, which extend downwards to the quartzose sandstone soles of faciès B and

Mid and Late Devonian arenites deposited by sheet-flood, braided streams and rivers in the northern Barrier Ranges, far western New South Wales, Australia

NASA Astrophysics Data System (ADS)

Neef, G.; Bottrill, R. S.; Cohen, D. R.

1996-05-01

Extensive and well exposed, fine-grained fluvial sandstone and less common pebbly coarse-grained fluvial sandstone of Devonian age, crop out in the northern Barrier Ranges of far west New South Wales, Australia. These strata were deposited largely on low-gradient alluvial fans in a basin and range landscape and contain common sedimentary structures (especially streaming lineations and tabular cross-beds). Around 400 of these sedimentary structures were measured to determine the palaeoflow trends of the sheet floods, streams or rivers which deposited the sandstone. The strata are mapped as the Mid Devonian Coco Range Sandstone and the Late Devonian Nundooka Sandstone, which together are around 2.7 km thick. They were deposited at the western margin of the large Emsian to Early Carboniferous Darling Basin. The Coco Range Sandstone is Emsian to Eifelian in age (based on fragments) of fossil fish) and it is separated from the Frasnian-Famennian (Late Devonian) Nundooka Sandstone by the north-trending Nundooka Creek Fault. The eastern boundary of the Nundooka Sandstone is formed by the Western Boundary Fault. Eastward of this fault is the north-trending and 40 km wide Bancannia Trough, which contains gently folded Late Silurian to Early Carboniferous strata up to 7.5 km thick. Most of the Coco Range Sandstone and all of the Nundooka Sandstone are non-graded, fine and very fine-grained, light brown sub-litharenites which are considered to have been deposited mainly on low-gradient alluvial fans. Sedimentary successions of 1.75 to 5.25 m thickness in the fine-grained arenite usually commence with Sm (massive or slumped) → Sh (laminated arenite) or St (trough cross-beds) → Sp (tabular cross-bedded sandstone). An erosional surface commonly underlies the sedimentary successions and they are interpreted to be the result of deposition from decelerating sheet floods. Units composed of tabular cross-bedded strata several metres thick are rarely channelised and are

Lithology, hydraulic properties, and water quality of the Sandstone Aquifer in the northwestern part of the Bad River Indian Reservation, Wisconsin, 1998-1999

USGS Publications Warehouse

Dunning, Charles P.

2005-01-01

The Precambrian sandstone aquifer in the northwestern part of the Bad River Band of Lake Superior Tribe of Chippewa Indians Reservation, Ashland County, Wisconsin, provides much of the drinking water to area residents. A study was undertaken in cooperation with the Bad River Tribe to provide specific information about the lithology, hydraulic properties, and water quality of the sandstone aquifer. During 1998 and 1999, the U.S. Geological Survey installed three monitoring wells, collected and analyzed lithologic and water samples, and conducted geophysical logging and aquifer tests to characterize the sandstone aquifer. The two monitoring wells in the southeastern part of the study area, the Diaperville Monitoring Well #1 (Diaperville MW #1) and the Tolman Monitoring Well #1 (Tolman MW #1) , are believed to have encountered older Middle Proterozoic Oronto Group sandstones. The sandstone encountered in the Ackley Monitoring Well #1 (Ackley MW #1) is believed to be Chequamegon Sandstone of the Late Proterozoic Bayfield Group. This interpretation is based on previous studies, as well as thin- section analysis of sandstone core recovered from the Ackley Monitoring Well #1. Results of aquifer tests conducted in the Diaperville Monitoring Well #1 and the Tolman Monitoring Well #1 provide ranges for hydraulic param - eter values in the sandstone aquifer: transmissivity ranges from 83 to 509 square feet per day; hydraulic conductivity ranges from 1.6 to 4.5 feet per day; storativity ranges from 0.00019 to 0.00046; and specific capacity ranges from 0.22 to 0.67 gallons per minute per foot. Though high- and low-angle fractures are present in Ackley Monitoring Well #1 core, the hydraulic properties of the bedrock appear to be due largely to the matrix porosity measured in thin section (16–21 percent) and permeability of the sandstone. The aquifer test for the Diaperville Monitoring Well #1 resulted in observed drawdown in nearby glacial wells, evidence of a hydraulic

Paleozoic Assemblage of the Northern Sierra Terrane: New Geochronology And Geochemical Data From the Stitching Late Devonian - Early Carboniferous Bowman Lake Batholith, and Associated Rocks

NASA Astrophysics Data System (ADS)

Powerman, V.; Hanson, R. E.; Girty, G.; Tretiakov, A.

2016-12-01

Previous study (Grove et al., 2008) of detrital zircon ages and the timing of magmatism within the Northern Sierra terrane (NST) suggest that it is exotic relative to western Laurentia, and link it to the Paleozoic Arctic Realm, Baltica and Caledonides. NST is a composite terrane in the North America Cordillera, consisting of four distinct allochthons, thrusted upon each other. As a first step towards the understanding of the origin and tectonic development of the NST we have undertaken the SHRIMP-RG U-Pb zircon dating of the rocks from granites, granodiorites, trondhjemites, tonalites and hypabyssal intrusions, composing the Bowman Lake batholith. The batholith stitches the allochthons of the NST and its crystallization age signifies the timing of juxtaposition SHRIMP-RG analyses from 14 samples yielded an age range of ca. 352-369 Ma, which overlaps the Devonian-Mississipian boundary and constrains the minimum age for amalgamation. Additionally, we have acquired multiple XRF data, favoring the island arc provenance of the Bowman Lake batholith Batholith. Previously proposed ties between NST and Robert Mountains allochthon seem unlikely because the latter was accreted onto the western miogeocline of Laurentia during the Late Dev.-Early Miss. while the NST was most probably still situated within the Arctic Realm. This work has been supported by the grant #14.Z50.31.0017 of the Government of the Russian Federation and by the Russian Foundation for Basic Research grant #15-55-10055. We are grateful to Stanford-USGS SHRIMP-RG center, and personally to Marty Grove and Elizabeth Miller.

Cathodoluminescence investigations on quartz cement in the sandstones of Khabour Formation from Iraqi Kurdistan Region, Northern Iraq

NASA Astrophysics Data System (ADS)

Omer, Muhamed F.; Friis, Henrik

2014-03-01

The Ordovician deltaic to shallow marine Khabour Formation in Northern Iraq consists mainly of sandstone with minor siltstone and interbedded shale. The sandstones are pervasively cemented by quartz that resulted in very little preserved primary porosity. Cathodoluminescence and petrographic studies showed that the silica cementation occurred in five successive phases which can be distinguished by their luminescence pattern. The precipitations of two phases have predated the major compaction process while the other phases are younger. The successive phases represent a sequence of changes in silica supply which were classified as very early and early, derived from dissolved biogenic silica that precipitated as opal/microquartz, possibly pre-compactional and of non-luminescent quartz overgrowth type. This was followed by phases whose silica supply derived from pressure solution of quartz, dissolution of feldspar, and hydrothermal fluids related to major thrust fault event. These successive quartz cement phases showed an increase in luminescence and the development of complicated zonation pattern in late-stage quartz cementation.

Petroleum geology of Amu-Dar'ya province of Soviet Central Asia

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

Clarke J.W.

1986-05-01

The Amu-Dar'ya oil and gas province extends over an area of 360,000 km/sup 2/ in central and eastern Turkmenia and western Uzbekistan in southern Soviet Central Asia. The province coincides with the eastern half of the Turan platform. A Mesozoic-Cenozoic sedimentary cover, 2-7 km thick, rests on a folded paleozoic basement. An Upper Jurassic salt unit divides the sedimentary section into subsalt and suprasalt parts. The structure of the sedimentary cover developed by vertical movements during the Mesozoic and Cenozoic, most of it during the late Tertiary in response to Alpine tectonism. Consequently, much of the trap formation and fillingmore » is late in geologic time and is apparently in progress at present. The province is gas prone; only in the Bukhara area on the east is there significant oil. Five plays are recognized. The Lower to Middle Jurassic play consists of alternating clays, sandstone, and siltstone. Thickness is 100-400 m. The Upper Jurassic play consists of Callovian-Oxfordian carbonate deposits, which are up to 500 m thick. The seal is Kimmeridgian-Tithonian salt. The carbonate deposits of this play are commonly a reef facies. The Lower Cretaceous play consists largely of alternating sandstone, clays, and siltstones. The seal is a clay unit of late Aptian and Albian age, which also separates this play from the overlying Albian-Cenomanian play. The Albian-Cenomanian play has sandstone and siltstone reservoirs, and the seal is a Turonian clay unit. The Paleogene play is prospective in the northeast part of the study area in the so-called Bukhara clastic beds.« less

Assessment of Paleozoic terrane accretion along the southern central Andes using detrital zircon geochronology

NASA Astrophysics Data System (ADS)

McKenzie, R.; Horton, B. K.; Fuentes, F.; Fosdick, J. C.; Capaldi, T.; Stockli, D. F.; Alvarado, P. M.

2015-12-01

Two distinct Paleozoic terranes known as Cuyania and Chilenia occupy the southern central Andes of Argentina and Chile. Because the proposed terrane boundaries coincide with major structural elements of the modern Andean system at 30-36°S, it is important to understand their origins and potential role in guiding later Andean deformation. The Cuyania terrane of western Argentina encompasses the Precordillera (PC) and a thick-skinned thrust block of the western Sierras Pampeanas, persisting southward to the San Rafael Basin (SRB). Although recently challenged, Cuyania has been long considered a piece of southern Laurentia that rifted away during the early Cambrian and collided with the Argentine margin during the Ordovician. Chilenia is situated west of Cuyania and includes the Frontal Cordillera (FC) and Andean magmatic arc. This less-studied terrane was potentially accreted during an enigmatic Devonian orogenic event. We present new detrital zircon U-Pb age data from siliciclastic sedimentary rocks that span the entire Paleozoic to Triassic from the FC, PC, and SRB. Cambrian rocks of the PC exhibit similar zircon age distributions with prominent ~1.4 and subordinate ~1.1 Ga populations, which are distinct from other Paleozoic strata. Plutonic rocks with these ages are common in southern Laurentia, whereas ~1.4 Ga zircons are uncommon in South American age distributions. This supports a Laurentian origin for Cuyania in isolation from Argentina during the Cambrian. Upper Paleozoic strata from the PC, FC, and SRB all yield similar age data suggesting shared provenance across the proposed Cuyania-Chilenia suture. Age distributions also notably lack Devonian-age grains. The regional paucity of Devonian plutonic rocks and detrital zircon casts doubt on a possible arc system between these terranes at this time, a key requisite for the mid-Paleozoic transfer and accretion of Chilenia to the Argentine margin. Collectively, these data question the precise boundaries of the

Polygonal deformation bands in sandstone

NASA Astrophysics Data System (ADS)

Antonellini, Marco; Nella Mollema, Pauline

2017-04-01

We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are dm-wide zones of shear deformation bands that developed under shallow burial conditions in the lower portion of the Jurassic Entrada Fm (Utah, USA). The edges of the polygons are 1 to 5 meters long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain < 0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. Density inversion, that takes place where under-compacted and over-pressurized layers (Carmel Fm) lay below normally compacted sediments (Entrada Sandstone), may be an important process for polygonal deformation bands formation. The gravitational sliding and soft sediment structures typically observed within the Carmel Fm support this hypothesis. Soft sediment deformation may induce polygonal faulting in the section of the Entrada Sandstone just above the Carmel Fm. The permeability of the polygonal deformation bands is approximately 10-14 to 10-13 m2, which is less than the permeability of the host, Entrada Sandstone (range 10-12 to 10-11 m2). The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes.

Preliminary evaluation of the basal sandstone in Tennessee for receiving injected wastes

USGS Publications Warehouse

Mulderink, Dolores; Bradley, M.W.

1986-01-01

The EPA is authorized, under the Safe Drinking Water Act, to administer the Underground Injection Control program. This program allows for the regulation of deep-well disposal of wastes and establishes criteria to protect underground sources of drinking water from contamination. The basal sandstone in Tennessee occurs west of the Valley and Ridge province at depths of 5,000 to 9,000 ft below land surface. The basal sandstone consists of about 30 to 750 ft of Cambrian sandstone overlying the crystalline basement complex. The basal sandstone is overlain and confined by shale and carbonate rocks of the Middle and Upper Cambrian Conasauga Group. Hydrologic data for the basal sandstone, available from only three sites (four wells) in Tennessee, indicate that the basal sandstone generally has low porosity and permeability with a few zones having enough permeability to accept injected fluids. Limited water quality data indicate the basal sandstone contains water with dissolved solids concentrations exceeding 10,000 mg/L. Since the dissolved-solids concentrations exceed 10,000 mg/L, the basal sandstone is not classified as an underground source of drinking water according to EPA regulations. (Author 's abstract)

New geochronologic and stratigraphic evidence confirms the paleocene age of the dinosaur-bearing ojo alamo sandstone and animas formation in the San Juan Basin, New Mexico and Colorado

USGS Publications Warehouse

Fassett, J.E.

2009-01-01

Dinosaur fossils are present in the Paleocene Ojo Alamo Sandstone and Animas Formation in the San Juan Basin, New Mexico, and Colorado. Evidence for the Paleo-cene age of the Ojo Alamo Sandstone includes palynologic and paleomagnetic data. Palynologic data indicate that the entire Ojo Alamo Sandstone, including the lower dinosaur-bearing part, is Paleocene in age. All of the palynomorph-productive rock samples collected from the Ojo Alamo Sandstone at multiple localities lacked Creta-ceous index palynomorphs (except for rare, reworked specimens) and produced Paleocene index palynomorphs. Paleocene palynomorphs have been identified strati-graphically below dinosaur fossils at two separate localities in the Ojo Alamo Sand-stone in the central and southern parts of the basin. The Animas Formation in the Colorado part of the basin also contains dinosaur fossils, and its Paleocene age has been established based on fossil leaves and palynology. Magnetostratigraphy provides independent evidence for the Paleocene age of the Ojo Alamo Sandstone and its dinosaur-bearing beds. Normal-polarity magnetochron C29n (early Paleocene) has been identified in the Ojo Alamo Sandstone at six localities in the southern part of the San Juan Basin. An assemblage of 34 skeletal elements from a single hadrosaur, found in the Ojo Alamo Sandstone in the southern San Juan Basin, provided conclusive evidence that this assemblage could not have been reworked from underlying Cretaceous strata. In addition, geochemical studies of 15 vertebrate bones from the Paleocene Ojo Alamo Sandstone and 15 bone samples from the underlying Kirtland Formation of Late Creta-ceous (Campanian) age show that each sample suite contained distinctly different abundances of uranium and rare-earth elements, indicating that the bones were miner-alized in place soon after burial, and that none of the Paleocene dinosaur bones ana-lyzed had been reworked. ?? U.S. Geological Survey, Public Domain April 2009.

Mobilization of aluminum by the acid percolates within unsaturated zone of sandstones.

PubMed

Navrátil, Tomáš; Vařilová, Zuzana; Rohovec, Jan

2013-09-01

The area of the Black Triangle has been exposed to extreme levels of acid deposition in the twentieth century. The chemical weathering of sandstones found within the Black Triangle became well-known phenomenon. Infiltration of acid rain solutions into the sandstone represents the main input of salt components into the sandstone. The infiltrated solutions--sandstone percolates--react with sandstone matrix and previously deposited materials such as salt efflorescence. Acidic sandstone percolates pH 3.2-4.8 found at ten sites within the National Park Bohemian Switzerland contained high Al-tot (0.8-10 mg L(-1)) concentrations and high concentrations of anions SO4 (5-66 mg L(-1)) and NO3 (2-42 mg L(-1)). A high proportion (50-98 %) of Al-tot concentration in acid percolates was represented by toxic reactive Al(n+). Chemical equilibrium modeling indicated as the most abundant Al species Al(3+), AlSO4 (+), and AlF(2+). The remaining 2-50 % of Al-tot concentration was present in the form of complexes with dissolved organic matter Al-org. Mobilization and transport of Al from the upper zones of sandstone causes chemical weathering and sandstone structure deterioration. The most acidic percolates contained the highest concentrations of dissolved organic material (estimated up to 42 mg L(-1)) suggesting the contribution of vegetation on sandstone weathering processes. Very low concentrations of Al-tot in springs at BSNP suggest that Al mobilized in unsaturated zone is transported deeper into the sandstone. This process of mobilization could represent a threat for the water quality small-perched aquifers.

Contractional deformation of porous sandstone: Insights from the Aztec Sandstone, SE Nevada, USA

NASA Astrophysics Data System (ADS)

Fossen, Haakon; Zuluaga, Luisa F.; Ballas, Gregory; Soliva, Roger; Rotevatn, Atle

2015-05-01

Contractional deformation of highly porous sandstones is poorly explored, as compared to extensional deformation of such sedimentary rocks. In this work we explore the highly porous Aztec Sandstone in the footwall to the Muddy Mountain thrust in SE Nevada, which contains several types of deformation bands in the Buffington tectonic window: 1) Distributed centimeter-thick shear-enhanced compaction bands (SECBs) and 2) rare pure compaction bands (PCBs) in the most porous parts of the sandstone, cut by 3) thin cataclastic shear-dominated bands (CSBs) with local slip surfaces. Geometric and kinematic analysis of the SECBs, the PCBs and most of the CSBs shows that they formed during ∼E-W (∼100) shortening, consistent with thrusting related to the Cretaceous to early Paleogene Sevier orogeny of the North American Cordilleran thrust system. Based on stress path modeling, we suggest that the compactional bands (PCBs and SECBs) formed during contraction at relatively shallow burial depths, before or at early stages of emplacement of the Muddy Mountains thrust sheet. The younger cataclastic shear bands (CSBs, category 3), also related to E-W Sevier thrusting, are thinner and show larger shear offsets and thus more intense cataclasis, consistent with the initiation of cataclastic shear bands in somewhat less porous materials. Observations made in this work support earlier suggestions that contraction lead to more distributed band populations than what is commonly found in the extensional regime, and that shear-enhanced compaction bands are widespread only where porosity (and permeability) is high.

The Middle Jurassic Entrada Sandstone near Gallup, New Mexico

USGS Publications Warehouse

Robertson, J.F.; O'Sullivan, R. B.

2001-01-01

Near Gallup, New Mexico, the Middle Jurassic Entrada Sandstone consists of, in ascending order, the Iyanbito Member, the Rehoboth Member, and an upper sandstone member. The Rehoboth Member is named herein to replace the middle siltstone member, with a type section located 26 km east of Gallup. The Iyanbito Member has been erroneously equated with the Wingate Sandstone of northeast Arizona, and the Rehoboth Member has been miscorrelated with the Dewey Bridge Member of the Entrada in Utah. The Dewey Bridge is an older unit that does not extend into New Mexico. The Iyanbito Member, east of Gallup, overlies the J-2 unconformity and the eroded tops of the Owl Rock and Petrified Forest Members of the Chinle Formation. The Wingate Sandstone of the Lower Jurassic Glen Canyon Group overlies the J-0 unconformity and the underlying Rock Point Member (topmost unit) of the Chinle Formation in northeast Arizona. Both the Wingate Sandstone and the Rock Point Member are missing east of Gallup below the J-2 unconformity. Similarly, the Wingate is missing southwest of Gallup, near Lupton, Arizona, but the Rock Point Member is present and underlies the Iyanbito from Zuni northward to Toadlena, New Mexico. The Wingate and other formations of the Glen Canyon Group thin and wedge out southward and eastward in northeast Arizona. The J-2 unconformity truncates the Wingate Sandstone and the underlying J-0 unconformity, 5 km north of Toadlena.

Geology of the Naturita NW quadrangle, Colorado

USGS Publications Warehouse

Cater, Fred W.; Vogel, J.D.

1953-01-01

The Naturita NW quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles were mapped by the U.S. Geological Survey on behalf of the U.S. Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear ro be related to certain sedimentary structures in sandstones of favorable composition.

Middle Micoene sandstone reservoirs of the Penal/Barrackpore field

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

Dyer, B.L.

1991-03-01

The Penal/Barrackpore field was discovered in 1938 and is located in the southern subbasin of onshore Trinidad. The accumulation is one of a series of northeast-southwest trending en echelon middle Miocene anticlinal structures that was later accentuated by late Pliocene transpressional folding. Relative movement of the South American and Caribbean plates climaxed in the middle Miocene compressive tectonic event and produced an imbricate pattern of southward-facing basement-involved thrusts. Further compressive interaction between the plates in the late Pliocene produced a transpressive tectonic episode forming northwest-southeast oriented transcurrent faults, tear faults, basement thrust faults, lystric normal faults, and detached simple foldsmore » with infrequent diapiric cores. The middle Miocene Herrera and Karamat turbiditic sandstones are the primary reservoir rock in the subsurface anticline of the Penal/Barrackpore field. These turbidites were sourced from the north and deposited within the marls and clays of the Cipero Formation. Miocene and Pliocene deltaics and turbidites succeed the Cipero Formation vertically, lapping into preexisting Miocene highs. The late Pliocene transpression also coincides with the onset of oil migration along faults, diapirs, and unconformities from the Cretaceous Naparima Hill source. The Lengua Formation and the upper Forest clays are considered effective seals. Hydrocarbon trapping is structurally and stratigraphically controlled, with structure being the dominant trapping mechanism. Ultimate recoverable reserves for the field are estimated at 127.9 MMBo and 628.8 bcf. The field is presently owned and operated by the Trinidad and Tobago Oil Company Limited (TRINTOC).« less

Valley-fill sequences and onlap geometries, Lower Cretaceous Muddy Sandstone, Kitty Field, Powder River basin, Wyoming

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

Gardner, M.H.; Gustason, E.R.

1987-05-01

The Muddy Sandstone at Kitty field is a valley-fill sequence that records a late Albian sea level rise and accompanying transgression. The valley was cut during a preceding sea level lowstand. Stratal geometries and facies successions within the valley fill demonstrate the history of transgression was not gradual and progressive. Rather, the valley fill comprises a series of discrete, time-bounded, depositional units which onlap the erosional surface. Five time-bounded depositional units were defined by facies successions and were used to define onlap geometries. Facies successions within individual units record progressive shoaling. Capping each succession, there may be a planar disconformity,more » a thin bioturbated interval, or the deepest water facies of the next depositional event. Thus, the termination of each depositional event is marked by an episode of rapid deepening. At a single geographic location, stratal successions within older depositional units represent more landward facies than those within younger units. Therefore, the onlap geometry of the valley-fill sequence consists of a landward-stepping arrangement of depositional units. The primary reservoirs within the valley-fill sequence, at Kitty field, are laterally coalesced, channel-belt sandstones at the base and barrier island sandstones at the top. Reservoir sandstones of lesser quality occur within the intermediate estuarine facies. The stacking pattern, developed by onlap of the units, results in multiple pay zones within mid-valley reaches. The boundaries of each depositional unit define a high-resolution, chronostratigraphic correlation of valley-fill strata, a correlation corroborated by bentonites. This correlation method gives an accurate description of the internal geometry of valley-fill strata and, therefore, provides a basis for understanding the process of transgressive onlap.« less

Neoproterozoic, Paleozoic, and Mesozoic granitoid magmatism in the Qinling Orogen, China: Constraints on orogenic process

NASA Astrophysics Data System (ADS)

Wang, Xiaoxia; Wang, Tao; Zhang, Chengli

2013-08-01

The Qinling Orogen is one of the main orogenic belts in Asia and is characterized by multi-stage orogenic processes and the development of voluminous magmatic intrusions. The results of zircon U-Pb dating indicate that granitoid magmatism in the Qinling Orogen mainly occurred in four distinct periods: the Neoproterozoic (979-711 Ma), Paleozoic (507-400 Ma), and Early (252-185 Ma) and Late (158-100 Ma) Mesozoic. The Neoproterozoic granitic magmatism in the Qinling Orogen is represented by strongly deformed S-type granites emplaced at 979-911 Ma, weakly deformed I-type granites at 894-815 Ma, and A-type granites at 759-711 Ma. They can be interpreted as the products of respectively syn-collisional, post-collisional and extensional setting, in response to the assembly and breakup of the Rodinia supercontinent. The Paleozoic magmatism can be temporally classified into three stages of 507-470 Ma, 460-422 Ma and ˜415-400 Ma. They were genetically related to the subduction of the Shangdan Ocean and subsequent collision of the southern North China Block and the South Qinling Belt. The 507-470 Ma magmatism is spatially and temporally related to ultrahigh-pressure metamorphism in the studied area. The 460-422 Ma magmatism with an extensive development in the North Qinling Belt is characterized by I-type granitoids and originated from the lower crust with the involvement of mantle-derived magma in a collisional setting. The magmatism with the formation age of ˜415-400 Ma only occurred in the middle part of the North Qinling Belt and is dominated by I-type granitoid intrusions, and probably formed in the late-stage of a collisional setting. Early Mesozoic magmatism in the study area occurred between 252 and 185 Ma, with the cluster in 225-200 Ma. It took place predominantly in the western part of the South Qinling Belt. The 250-240 Ma I-type granitoids are of small volume and show high Sr/Y ratios, and may have been formed in a continental arc setting related to subduction

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE PAGES

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.; ...

2016-09-04

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

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

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Development of diagenetic seals in carbonates and sandstones

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

Schmidt, V.; Almon, W.

1983-03-01

Diagenetic seals effectively block the movement of reservoir hydrocarbons in many sandstone and carbonate rock units. Diagenetic seals in sandstones and carbonate rocks encase reservoir rocks with either depositional or diagenetic porosity. Diagenetic reservoir porosity may originate before or after the establishment of an effective diagenetic seal. Hydrocarbon traps with diagenetic seals may conform in their geometry as well to structure or stratigraphy as to diagenetic facies. Therefore, some structural and stratigraphic traps may, in part or entirely, depend on diagenetic seals. Detailed analysis of diagenetic seals in sandstones and carbonate rocks can considerably improve our ability to predict theirmore » occurrence and to recognize their spatial and temporal relationship to reservoir rocks and hydrocarbon migration.« less

Hydrologic properties and ground-water flow systems of the Paleozoic rocks in the upper Colorado River basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

USGS Publications Warehouse

Geldon, Arthur L.

2003-01-01

system and the overlying Canyonlands aquifer. Composed of the uppermost Paleozoic rocks, the Canyonlands aquifer consists, in ascending order, of the Cutler-Maroon, Weber-De Chelly, and Park City-State Bridge zones. The Paleozoic rocks are underlain by a basal confining unit consisting of Precambrian sedimentary, igneous, and metamorphic rocks and overlain throughout most of the Upper Colorado River Basin by the Chinle-Moenkopi confining unit, which consists of Triassic formations composed mostly of shale. The largest values of porosity, permeability, hydraulic conductivity, transmissivity, and artesian yield are exhibited by the Redwall-Leadville zone of the Madison aquifer and the Weber-De Chelly zone of the Canyonlands aquifer. The former consists almost entirely of Devonian and Mississippian carbonate rocks: the latter consists mostly of Pennsylvanian and Permian quartz sandstone. Unit-averaged porosity in hydrogeologic units composed of Paleozoic rocks ranges from less than 1 to 28 percent. Permeability ranges from less than 0.0001 to 3,460 millidarcies. Unit-averaged hydraulic conductivity ranges from 0.000005 to 200 feet per day. The composite transmissivity of Paleozoic rocks ranges from 0.0005 to 47,000 feet squared per day. Artesian yields to wells and springs (excluding atypical springflows) from these hydrogeologic units range from less than 1 to 10,000 gallons per minute. The permeability and watersupply capabilities of all hydrogeologic units progressively decrease from uplifted areas to structural basins. Recharge to the Paleozoic rocks is provided by direct infiltration of precipitation, leakage from streams, and ground-water inflows from structurally continuous areas west and north of the Upper Colorado River Basin. The total recharge available flom ground-water systems in the basin from direct precipitation and stream leakage is estimated to be 6,600,000 acre-feet per year. However, little of this recharge directly enters the Paleozoic rocks

Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Yen, A. S.; Rampe, E. B.; Grotzinger, J. P.; Blake, D. F.; Bristow, T. F.; Chipera, S. J.; Downs, R.; Morris, R. V.; Morrison, S. M.;

The Paleozoic ichthyofauna of the Amazonas and Parnaíba basins, Brazil

NASA Astrophysics Data System (ADS)

Figueroa, Rodrigo Tinoco; Machado, Deusana Maria da Costa

2018-03-01

The Brazilian Paleozoic ichthyofauna from the Parnaíba and Amazonas basins regard a sparsely known diversity, including chondrichthyans and acanthodians, besides some osteichthyan remains. This work proposes a revision of the fossil material from these two sedimentary basins and synthesizes the morphological aspect of such material trying to understand the influences of those fossils to the paleontology of the region, comparing the Brazilian fossils with other gondwanan faunas. The Brazilian Paleozoic fish fauna shows great resemblance to those of Bolivia, especially during the Devonian. Many of the Acanthodian spines from the Manacapuru Formation (Amazonas Basin), and the Pimenteira Formation (Parnaíba Basin), are comparable to the taxa found in Bolivia. The lack of more Placoderm remains in the Brazilian outcrops is similar to the low diversity of this group in Bolivia, when compared to other South American and Euramerican localities. The most diverse Brazilian ichthyofauna is encountered in the Permian Pedra de Fogo Formation where numerous chondrichthyans and 'paleopterygians' remains are found, together with dipnoans and actinistians. Despite the apparent lack of more representative Paleozoic ichthyofaunas in Brazil, the available material that ranges from Lower Devonian to early Permian from Brazil bears important taxa that could address valuable taxonomic and biogeographic informations.

Petroleum geology of Carter sandstone (upper Mississippian), Black Warrior Basin, Alabama

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

Bearden, B.L.; Mancini, E.A.

1985-03-01

The presence of combination petroleum traps makes the Black Warrior basin of northwestern Alabama an attractive area for continued hydrocarbon exploration. More than 1,500 wells have been drilled, and more than 90 separate petroleum pools have been discovered. The primary hydrocarbon reservoirs are Upper Mississippian sandstones. The Carter sandstone is the most productive petroleum reservoir in the basin. Productivity of the Carter sandstone is directly related to its environment of deposition. The Carter accumulated within a high constructive elongate to lobate delta, which prograded into the basin from the northwest to the southeast. Carter bar-finger and distal-bar lithofacies constitute themore » primary hydrocarbon reservoirs. Primary porosity in the Carter sandstone has been reduced by quartz overgrowths and calcite cementation. Petroleum traps in the Carter sandstone in central Fayette and Lamar Counties, Alabama, are primarily stratigraphic and combination (structural-stratigraphic) traps. The potential is excellent for future development of hydrocarbon reservoirs in the Upper Mississippian Carter sandstone. Frontier regions south and east of the known productive limits of the Black Warrior basin are ideal areas for continued exploration.« less

Drilling history and stratigraphic correlation of Rose Run sandstone of northeastern Ohio

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

Moyer, C.C.

1988-08-01

To date, 40 known tests have penetrated the Knox unconformity in Ashtabula, Lake, Trumbull, Geauga, and Portage Counties, Ohio. Prior to 1980, there were only 22 tests. Of these, only 10 penetrated and logged rocks older than the Rose Run sandstone. In the period 1980-1986, two Rose Run discoveries were drilled, one in New Lyme Township of Ashtabula County and one in Burton Township of Geauga County. Both discovery wells have been offset. Attempts have been made to correlate these two areas with older tests in northeastern Ohio and with the Rose Run sandstones of Coshocton County. In northeastern Ohio,more » preliminary studies indicate a Rose Run sandstone and/or dolomite interval approximately 100 ft thick. The upper 50 ft is predominantly sandstone and the lower 50 ft changes locally from sandstone to dolomite. The upper sandy member can be correlated to the A, B, and C sandstone units of Coshocton County.« less

Late Paleozoic fusulinids from Sonora, Mexcio: importance for interpretation of depositional settings, biogeography, and paleotectonics

USGS Publications Warehouse

Stevens, Calvin H.; Poole, Forrest G.; Amaya-Martínez, Ricardo

2014-01-01

Three sets of fusulinid faunas in Sonora, Mexico, discussed herein, record different depositional and paleotectonic settings along the southwestern margin of Laurentia (North America) during Pennsylvanian and Permian time. The settings include: offshelf continental rise and ocean basin (Rancho Nuevo Formation in the Sonora allochthon), shallow continental shelf (La Cueva Limestone), and foredeep basin on the continental shelf (Mina México Formation). Our data represent 41 fusulinid collections from 23 localities with each locality providing one to eight collections.Reworked fusulinids in the Middle and Upper Pennsylvanian part of the Rancho Nuevo Formation range in age from Desmoinesian into Virgilian (Moscovian-Gzhelian). Indigenous Permian fusulinids in the La Cueva Limestone range in age from middle or late Wolfcampian to middle Leonardian (late Sakmarian-late Artinskian), and reworked Permian fusulinids in the Mina México Formation range in age from early to middle Leonardian (middle-late Artinskian). Conodonts of Guadalupian age occur in some turbidites in the Mina México Formation, indicating the youngest foredeep deposit is at least Middle Permian in age. Our fusulinid collections indicate a hiatus of at least 10 m.y. between the youngest Pennsylvanian (Virgilian) rocks in the Sonora allochthon and the oldest Permian (middle Wolfcampian) rocks in the region.Most fusulinid faunas in Sonora show affinities to those of West Texas, New Mexico, and Arizona; however, some genera and species are similar to those in southeastern California. As most species are similar to those east of the southwest-trending Transcontinental arch in New Mexico and Arizona, this arch may have formed a barrier preventing large-scale migration and mixing of faunas between the southern shelf of Laurentia in northwestern Mexico and the western shelf in the southwestern United States.The Sonora allochthon, consisting of pre-Permian (Lower Ordovician to Upper Pennsylvanian) deep

Sedimentary rocks of the coast of Liberia

USGS Publications Warehouse

White, Richard William

1969-01-01

Two basins containing sedimentary rocks o# probable Cretaceous age have been recognized near the coast of Liberia in the area between Monrovia and Buchanan; geophysical evidence suggests that similar though larger basins exist on the adjacent continental shelf. The oldest sedimentary unit recognized, the Paynesville Sandstone of possible early to middle Paleozoic age, is intruded by dikes and sills of diabase of early Jurassic age and lies unconformably on crystalline rocks of late Precambrian age. Dips in the Paynesville Sandstone define a structural basin centered south of Roberts International Airport (formerly called Roberts Field) about 25 miles east of Monrovla. Wackes and conglomerates of Cretaceous age, herein named the Farmington River Formation, unconformably overlie the Paynesville Sandstone and constitute the sedimentary fill in the Roberts basin. The Bassa basin lies to the southeast of the Roberts basin and is separated from it by an upwarp of crystalline rocks. The basin is occupied by wackes and conglomerates of the Farmington River Formation, which apparently lie directly on the crystalline basement. Both basins are bounded on the northeast by northwest-trending dip-slip faults. The best potential for petroleum deposits that exists in Liberia is beneath the adjacent continental shelf and slope. Geophysical exploration and drilling will be required to evaluate this potential.

Formation of modern and Paleozoic stratiform barite at cold methane seeps on continental margins

USGS Publications Warehouse

Torres, M.E.; Bohrmann, G.; Dube, T.E.; Poole, F.G.

2003-01-01

Stratiform (bedded) Paleozoic barite occurs as large conformable beds within organic- and chert-rich sediments; the beds lack major sulfide minerals and are the largest and most economically significant barite deposits in the geologic record. Existing models for the origin of bedded barite fail to explain all their characteristics: the deposits display properties consistent with an exhalative origin involving fluid ascent to the seafloor, but they lack appreciable polymetallic sulfide minerals and the corresponding strontium isotopic composition to support a hydrothermal vent source. A new mechanism of barite formation, along structurally controlled sites of cold fluid seepage in continental margins, involves barite remobilization in organic-rich, highly reducing sediments, transport of barium-rich fluids, and barite precipitation at cold methane seeps. The lithologic and depositional framework of Paleozoic and cold seep barite, as well as morphological, textural, and chemical characteristics of the deposits, and associations with chemosymbiotic fauna, all support a cold seep origin for stratiform Paleozoic barite. This understanding is highly relevant to paleoceanographic and paleotectonic studies, as well as to economic geology.

Quantification of the effects of secondary matrix on the analysis of sandstone composition, and a petrographic-chemical technique for retrieving original framework grain modes of altered sandstones.

PubMed

Cox, R; Lowe, D R

1996-05-01

Most studies of sandstone provenance involve modal analysis of framework grains using techniques that exclude the fine-grained breakdown products of labile mineral grains and rock fragments, usually termed secondary matrix or pseudomatrix. However, the data presented here demonstrate that, when the proportion of pseudomatrix in a sandstone exceeds 10%, standard petrographic analysis can lead to incorrect provenance interpretation. Petrographic schemes for provenance analysis such as QFL and QFR should not therefore be applied to sandstones containing more than 10% secondary matrix. Pseudomatrix is commonly abundant in sandstones, and this is therefore a problem for provenance analysis. The difficulty can be alleviated by the use of whole-rock chemistry in addition to petrographic analysis. Combination of chemical and point-count data permits the construction of normative compositions that approximate original framework grain compositions. Provenance analysis is also complicated in many cases by fundamental compositional alteration during weathering and transport. Many sandstones, particularly shallow marine deposits, have undergone vigorous reworking, which may destroy unstable mineral grains and rock fragments. In such cases it may not be possible to retrieve provenance information by either petrographic or chemical means. Because of this, pseudomatrix-rich sandstones should be routinely included in chemical-petrological provenance analysis. Because of the many factors, both pre- and post-depositional, that operate to increase the compositional maturity of sandstones, petrologic studies must include a complete inventory of matrix proportions, grain size and sorting parameters, and an assessment of depositional setting.

Sandstone-filled normal faults: A case study from central California

NASA Astrophysics Data System (ADS)

Palladino, Giuseppe; Alsop, G. Ian; Grippa, Antonio; Zvirtes, Gustavo; Phillip, Ruy Paulo; Hurst, Andrew

2018-05-01

Despite the potential of sandstone-filled normal faults to significantly influence fluid transmissivity within reservoirs and the shallow crust, they have to date been largely overlooked. Fluidized sand, forcefully intruded along normal fault zones, markedly enhances the transmissivity of faults and, in general, the connectivity between otherwise unconnected reservoirs. Here, we provide a detailed outcrop description and interpretation of sandstone-filled normal faults from different stratigraphic units in central California. Such faults commonly show limited fault throw, cm to dm wide apertures, poorly-developed fault zones and full or partial sand infill. Based on these features and inferences regarding their origin, we propose a general classification that defines two main types of sandstone-filled normal faults. Type 1 form as a consequence of the hydraulic failure of the host strata above a poorly-consolidated sandstone following a significant, rapid increase of pore fluid over-pressure. Type 2 sandstone-filled normal faults form as a result of regional tectonic deformation. These structures may play a significant role in the connectivity of siliciclastic reservoirs, and may therefore be crucial not just for investigation of basin evolution but also in hydrocarbon exploration.

The main features of the Uralian Paleozoic magmatism and the epioceanic nature of the orogen

NASA Astrophysics Data System (ADS)

Fershtater, G. B.

2013-02-01

The 2000 km Uralian Paleozoic orogen is situated on the western flank of the Uralo-Mongolian folded belt. It is characterized by an abundant variety of magmatic rocks and related ore deposits. Uralian Paleozoic magmatism is entirely subduction-related. It is proposed that the Uralian orogen represents a cold mobile belt in which the mantle temperature was 200 to 500 °C cooler than in the adjacent areas; a situation which is similar to the modern West Pacific Triangle Zone including Indonesia, the Philippine Islands, and southern Asia. During the course of the geological evolution of the Uralian orogen, the nature of the magmatism has changed from basic rocks of indisputable mantle origin (460-390 Ma) to mantle-crust gabbro-granitic complexes (370-315 Ma) followed by pure crustal granite magmatism (290-250 Ma). This order in rock type and age reflects the evolution of Paleozoic magmatic complexes from the beginning of subduction to the final stages of the orogen development.

Paleomagnetic tests for tectonic reconstructions of the Late Jurassic-Early Cretaceous Woyla Group, Sumatra

NASA Astrophysics Data System (ADS)

Advokaat, Eldert; Bongers, Mayke; van Hinsbergen, Douwe; Rudyawan, Alfend; Marshal, Edo

2017-04-01

SE Asia consists of multiple continental blocks, volcanic arcs and suture zones representing remnants of closing ocean basins. The core of this mainland is called Sundaland, and was formed by accretion of continental and arc fragments during the Paleozoic and Mesozoic. The former positions of these blocks are still uncertain but reconstructions based on tectonostratigraphic, palaeobiogeographic, geological and palaeomagnetic studies indicate the continental terranes separated from the eastern margin of Gondwana. During the mid-Cretaceous, more continental and arc fragments accreted to Sundaland, including the intra-oceanic Woyla Arc now exposed on Sumatra. These continental fragments were derived from Australia, but the former position of the Woyla Arc is unconstrained. Interpretations on the former position of the Woyla Arc fall in two end-member groups. The first group interprets the Woyla Arc to be separated from West Sumatra by a small back-arc basin. This back arc basin opened in the Late Jurassic, and closed mid-Cretaceous, when the Woyla Arc collided with West Sumatra. The other group interprets the Woyla Arc to be derived from Gondwana, at a position close to the northern margin of Greater India in the Late Jurassic. Subsequently the Woyla Arc moved northwards and collided with West Sumatra in the mid-Cretaceous. Since these scenarios predict very different plate kinematic evolutions for the Neotethyan realm, we here aim to place paleomagnetic constraints on paleolatitudinal evolution of the Woyla Arc. The Woyla Arc consists mainly of basaltic to andesitic volcanics and dykes, and volcaniclastic shales and sandstones. Associated limestones with volcanic debris are interpreted as fringing reefs. This assemblage is interpreted as remnants of an Early Cretaceous intra-oceanic arc. West Sumatra exposes granites, surrounded by quartz sandstones, shales and volcanic tuffs. These sediments are in part metamorphosed. This assemblage is interpreted as a Jurassic

Late cretaceous extensional tectonics and associated igneous activity on the northern margin of the Gulf of Mexico Basin

NASA Technical Reports Server (NTRS)

Bowen, R. L.; Sundeen, D. A.

1985-01-01

Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic activity involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern margin of the cratonic platform from Arkansas to Georgia.

Underpressure in Mesozoic and Paleozoic rock units in the Midcontinent of the United States

USGS Publications Warehouse

Nelson, Philip H.; Gianoutsos, Nicholas J.; Drake, Ronald

2015-01-01

Potentiometric surfaces for Paleozoic strata, based on water well levels and selected drill-stem tests, reveal the control on hydraulic head exerted by outcrops in eastern Kansas and Oklahoma. From outcrop in the east, the westward climb of hydraulic head is much less than that of the land surface, with heads falling so far below land surface that the pressure:depth ratio in eastern Colorado is less than 5.7 kPa/m (0.25 psi/ft). Permian evaporites separate the Paleozoic hydrogeologic units from a Lower Cretaceous (Dakota Group) aquifer, and a highly saline brine plume pervading Paleozoic units in central Kansas and Oklahoma is attributed to dissolution of Permian halite. Underpressure also exists in the Lower Cretaceous hydrogeologic unit in the Denver Basin, which is hydrologically separate from the Paleozoic units. The data used to construct the seven potentiometric surfaces were also used to construct seven maps of pressure:depth ratio. These latter maps are a function of the differences among hydraulic head, land-surface elevation, and formation elevation. As a consequence, maps of pressure:depth ratio reflect the interplay of three topologies that evolved independently with time. As underpressure developed, gas migrated in response to the changing pressure regime, most notably filling the Hugoton gas field in southwestern Kansas. The timing of underpressure development was determined by the timing of outcrop exposure and tilting of the Great Plains. Explorationists in western Kansas and eastern Colorado should not be surprised if a reservoir is underpressured; rather, they should be surprised if it is not.

Hydropressure tongues within regionally geopressured lower Tuscaloosa sandstone, Tuscaloosa trend, Louisiana

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

McCulloh, R.P.; Purcell, M.D.

1983-09-01

A regional study of the Tuscaloosa Formation in Louisiana, undertaken to assess geopressured-geothermal potential, revealed lobate, downdip extensions of the hydropressured zone in lower Tuscaloosa massive sandstone facies below the regional top of geopressure. Normal pressure zones within geopressured section were identified by drilling-mud weights less than 13 lb/gal on electric logs of massive lower Tuscaloosa sandstone; cross section demonstrated updip continuity of these zones with the regional hydropressured zone. These hydropressure tongues are permitted by the anomalously high permeabilities reported from the deep Tuscaloosa trend, and they are attributed to both primary and secondary porosity by investigators of Tuscaloosamore » sandstone petrography. The hydropressure tongues correspond with lobes of thick net sandstone, principally in Pointe Coupee, East Felinicana, East Baton Rouge, and Livingston Parishes in the central Tuscaloosa trend. Limited control suggests at least one hydropressure tongue in the Chandeleur Sound area to the east. Dimensions of hydropressure tongues range up to 27 km (17 mi) parallel to srike and 17 km (11 mi) oblique to strike. In many places, tongues are terminated downdip by faults, which, by acting as pressure seals, prevent the tongues from extending to the downdip edge of the massive sandstone in the expanded sections of the downthrown blocks. The areal extent of geopressured Tuscaloosa sandstone is controlled updip by these fault zones, and downdip by pinch-out of the sandstone units basinward. Local hydropressure tongues diminish the geopressured-geothermal potential of the Tuscaloosa trend, but show no discernible relation to gas-productive areas.« less

Analyzing the Sand-fixing Effect of Feldspathic Sandstone from the Texture Characteristics

NASA Astrophysics Data System (ADS)

Zhang, lu; Ban, Jichang

2018-01-01

The purpose of this research was aimed to study the sand fixing effect of feldspathic sandstone in Mu Us Sandy Land, to provide a scienticic basis for desertification control, soil and water conservation and development of farming there. Methods of mixing feldspathic sandstone and aeolian sandy soil according to 1: 0, 1: 1, 1: 2, 1: 5, and 0: 1 mass ratioes, the graded composition and characteristics were studied with laser particle size analyzer. The result showed that these features of sand-based, loosely structured, easy to wind erosion of aeolian sandy soil were changed before feldspathic sandstone and aeolian sandy soil compounding. The <0.05 mm particle mass increased with feldspathic sandstone mass increasing. The texture presented this kind of change from sand to sandy loam to loam to silt loam. The small particle size distribution, good homogeneity and other features of aeolian sandy soil were improved to a certain degree, and the particle size distribution became broad before feldspathic sandstone and aeolian sandy soil compounding. The particle grading was continuous, and the grading characteristic was good when m(F): m(S) was 1: 5(Cu was 54.71 and Cc was 2.54) or when m(F): m(S) was 1: 2(Cu was 76.21, Cc was 1.12). The conclusion is that feldspathic sandstone has sand-fixing effect in texture characteristics, which heightens with feldspathic sandstone mass increasing, and when the mass ratio of feldspathic sandstone: aeolian sandy soil is 1: 2 or 1: 5 which compound better.

An Upper Paleozoic bio-chronostratigraphic scheme for the western margin of Gondwana

NASA Astrophysics Data System (ADS)

Césari, Silvia N.; Limarino, Carlos O.; Gulbranson, Erik L.

2011-05-01

The Carboniferous and Permian fossiliferous sequences of the central-western Argentina contain abundant plant remains, palynomorphs and invertebrates. They include a continuous record of large distribution in the Paganzo, Rio Blanco, Calingasta-Uspallata and San Rafael Basins. The most recent biostratigraphic schemes recognize a floristic succession represented by the biozones: Archaeosigillaria-Frenguellia (AF Biozone), Frenguellia eximia-Nothorhacopteris kellaybelenensis-Cordaicarpus cesarii (FNC Biozone), Nothorhacopteris-Botrychiopsis- Ginkgophyllum (NBG Biozone), Interval Biozone and Gangamopteris Biozone. The associated palynological record is represented by the biozones: Reticulatisporites magnidictyus-Verrucosisporites quasigobbetti (MQ Biozone), Raistrickia densa-Convolutispora muriornata (DM Biozone), Pakhapites fusus-Vittatina subsaccata (FS Biozone), and Lueckisporites-Weylandites (LW Biozone). The precise age of the Upper Paleozoic western Gondwanan biozones has been under discussion and remains controversial to date in some regions. The main issue hampering an integrated comparison of the Gondwanan biozones was its imprecise chronostratigraphic framework. However, new studies in some Argentinian stratigraphic sections bearing floras and faunas have yielded several radiometric ages. From these 206Pb/ 238U zircon datings it is possible to determine the chronostratigraphic range of many fossiliferous assemblages in this sector of Gondwana. In this way, the AF and MQ Biozones are restricted to the Late Mississippian and they would be not younger than 335 Ma according to radiometric ages. 206Pb/ 238U ages suggest that the NBG, DMa and DMb Biozones characterize the Late Serpukhovian glacial deposits and persisted up to the Late Bashkirian. Beds containing the Interval and DMc Biozones have yielded 206Pb/ 238U ages of 312.82 ± 0.11 Ma and 310.71 ± 0.1 Ma which would indicate that both zones characterize the Moscovian. The remains of Gangamopteris Biozone

Environmental control on concretion-forming processes: Examples from Paleozoic terrigenous sediments of the North Gondwana margin, Armorican Massif (Middle Ordovician and Middle Devonian) and SW Sardinia (Late Ordovician)

NASA Astrophysics Data System (ADS)

Dabard, Marie-Pierre; Loi, Alfredo

2012-08-01

Concretions of various compositions are common in the Paleozoic terrigenous successions of the north Gondwana margin. This study focuses on phosphatic (P) and siliceous (Si) concretions present in some successions of the Armorican Massif (NW France) and SW Sardinia (W Italy). It shows that they consist of mudstones, fine- to very fine-grained sandstones or shellbeds with a more or less abundant P-cement and form a continuum between a phosphatic end-member and a siliceous biogenic end-member. The P2O5 contents are ranging from 0.26% to 21.5% and are related to apatite. The SiO2 contents vary from 25% to 82% and are linked both to a terrigenous phase and to a biogenic silica phase. Concretions showing the lower P-contents (P2O5 < 1.5%) are often enriched in biogenic silica (SiO2/Al2O3 > 5). Comparison with the surrounding sediments shows that all the concretions are enriched in chlorite and in Middle Rare Earth Elements (Las/Gds: 0.12-0.72) and some of them in Y (up to 974 ppm), Rare Earth Elements (more than 300 ppm) and Sr (260-880 ppm). The concretions with highest biogenic silica concentrations are contained in the outer shelf sediments whereas the other concretions are present from the proximal part of the inner shelf to the outer shelf. A genetic model in two stages is proposed. During early diagenesis, the dissolution of shells and degradation of organic matter progressively enrich the pore water in dissolved Si, Ca and P. When the suboxic zone is reached, P-precipitation begins, leading to the formation of protoconcretions. In shallow environments, the relative permeability of sediments and the winnowing or reworking of the upper few centimetres by bottom currents allow for suboxic conditions to be maintained, leading to P-rich concretion formation. In deeper environments, the anoxic zone is reached more rapidly, thereby preventing extensive phosphogenesis. Nevertheless in the protoconcretions the early P-cement preserves pore spaces from compaction. In the

Comparative petrology of arkosic sandstone lithofacies of Cowlitz, Spencer, and Yamhill Formations, northwest Oregon

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

Van Atta, R.O.

Recent discovery (1979) and commercial production of natural gas in arkosic sandstone (Clark and Wilson sand, informal) of the Cowlitz Formation near Mist, Oregon, has stimulated interest in the sedimentology and stratigraphy of Narizian sandstones of northwestern Oregon and the Willamette lowlands. Petrographic study of arkosic sandstone in the lower part of the Cowlitz Formation in surface outcrops in Clatsop, Tillamook, and Columbia Counties, Oregon, and in the Texaco 1 Clatskanie well reveals that the composition is more lithic than that of arkosic sandstone (Clark and Wilson sand) in the upper part of the Cowlitz Formation. The petrography of highlymore » permeable, arkosic sandstone in the Spencer Formation in the western Tualatin Valley south of the Mist gas field is identical in framework grain composition, texture, matrix composition, and heavy mineral content to that of the gas producing Clark and Wilson sand. The petrography of sandstone in the Yamhill Formation in the western Tualatin Valley is very like that of sandstone in the lower part of the Cowlitz Formation of northern northwest Oregon. Diagenetic alteration is more pronounced in arkosic sandstone in the lower part of the Cowlitz Formation and in the Yamhill Formation compared to diagenesis, which is almost nil in arkosic sandstone in the upper part of the cowlitz and in the Spencer Formations. Natural gas exploration will be aided by a clearer and more certain understanding of these petrologic differences between Eocene sandstones in northwestern Oregon.« less

MX Siting Investigation. Geotechnical Evaluation. Detailed Aggregate Resources Study. Pahroc Study Area, Nevada.

DTIC Science & Technology

1981-06-05

source is a fairly limited outcrop of calcareous sandstone classified as dolomite rock (Do). Class RBIb Sources: Pour basin-fill sources within the study...Paleozoic rocks consist of limestone, dolomite , and quartzite with interbedded sandstone and shale. These units are generally exposed along the northern...categories simplify discussion and presentation without altering the conclusions of the study. 2.2.1 Rock Units Dolomite rocks (Do) and carbonate rocks

Characterization of the Highway 95 Fault in lower Fortymile Wash using electrical and electromagnetic methods, Nye County, Nevada

USGS Publications Warehouse

Macy, Jamie P.; Kryder, Levi; Walker, Jamieson

2012-01-01

Coordinated application of electrical and electromagnetic geophysical methods provided better characterization of the Highway 95 Fault. The comparison of dipole-dipole resistivity, TEM, and CSAMT data confirm faulting of an uplifted block of resistive Paleozoic Carbonate that lies beneath a more conductive sandstone unit. A more resistive alluvial basin-fill unit is found above the sandstone unit, and it constitutes only about 150 m of the uppermost subsurface.

Reported middle Paleozoic fossils and new geochronological data from the southern and central Appalachians: Disposable outrageous hypothesis or justification for major revision of tectonic history

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

Hatcher, R.D. Jr.

Recently published interpretations of fossil fragments from the Walden Creek Group (Ocoee Supergroup) suggesting that these rocks are middle Paleozoic (Devonian to Early Carboniferous), and new geochronological data that yield late Paleozoic age dates on rocks and major faults in the Blue Ridge and piedmont, if taken alone, would permit speculation that most of the deformation and metamorphism affecting this part of the orogen is Alleghanian. The two Ordovician clastic wedges (Sevier, Llanvirn, and Martinsburg, Caradoc-Ashgill) and the Carboniferous-Permian wedge(s), along with many radiometric ages on plutons, indicate uplift and sediment dispersal from the interior of the southern and centralmore » Appalachians (SCA) that may have resulted from Taconian and Alleghanian deformation. Combining the reproducible fossil evidence, including that from Alabama and a recently discovered crinoid fragment from the upper part of the Murphy belt sequence, with the most current geochronological data requires that peak metamorphism and penetrative deformation be at least Devonian or younger at the southwestern end of the orogen, and Late Ordovician or younger in the Carolinas and northern Georgia. Zircon ages reported from large thrust and dextral strike-slip faults bounding the Pine Mountain window indicate all of the faults there may be Alleghanian, except the younger sinistral Mesozoic faults, and requires that both metamorphism and penetrative deformation there also be Alleghanian. As in New England, the southern Appalachian Alleghanian metamorphic core is now known to be much more extensive. The older data require that the Taconian and perhaps the Acadian orogenies were significant events in the SCA, but these new data reconfirm the dominance of Alleghanian continent-continent collision processes here.« less

Environmental trends in extinction during the Paleozoic

NASA Technical Reports Server (NTRS)

Sepkoski, J. John, Jr.

1987-01-01

Extinction intensities calculated from 505 Paleozoic marine assemblages divided among six environmental zones and 40 stratigraphic intervals indicate that whole communities exhibit increasing extinction offshore but that genera within individual taxonomic classes tend to have their highest extinction onshore. The offshore trend at the community level results from a concentration of genera in classes with low characteristic extinction rates in nearshore environments. This finding is consistent with the ecologic expectation that organisms inhabiting unpredictably fluctuating environments should suffer more extinction than counterparts living under more predictably equitable conditions.

Hydrogeology of the Potsdam Sandstone in northern New York

USGS Publications Warehouse

Williams, John H.; Reynolds, Richard J.; Franzi, David A.; Romanowicz, Edwin A.; Paillet, Frederick L.

2010-01-01

The Potsdam Sandstone of Cambrian age forms a transboundary aquifer that extends across northern New York and into southern Quebec. The Potsdam Sandstone is a gently dipping sequence of arkose, subarkose, and orthoquartzite that unconformably overlies Precambrian metamorphic bedrock. The Potsdam irregularly grades upward over a thickness of 450 m from a heterogeneous feldspathic and argillaceous rock to a homogeneous, quartz-rich and matrix-poor rock. The hydrogeological framework of the Potsdam Sandstone was investigated through an analysis of records from 1,500 wells and geophysical logs from 40 wells, and through compilation of GIS coverages of bedrock and surficial geology, examination of bedrock cores, and construction of hydrogeological sections. The upper several metres of the sandstone typically is weathered and fractured and, where saturated, readily transmits groundwater. Bedding-related fractures in the sandstone commonly form sub-horizontal flow zones of relatively high transmissivity. The vertical distribution of sub-horizontal flow zones is variable; spacings of less than 10 m are common. Transmissivity of individual flow zones may be more than 100 m2/d but typically is less than 10 m2/d. High angle fractures, including joints and faults, locally provide vertical hydraulic connection between flow zones. Hydraulic head gradients in the aquifer commonly are downward; a laterally extensive series of sub-horizontal flow zones serve as drains for the groundwater flow system. Vertical hydraulic head differences between shallow and deep flow zones range from 1 m to more than 20 m. The maximum head differences are in recharge areas upgradient from the area where the Chateauguay and Chazy Rivers, and their tributaries, have cut into till and bedrock. Till overlies the sandstone in much of the study area; its thickness is generally greatest in the western part, where it may exceed 50 m. A discontinuous belt of bedrock pavements stripped of glacial drift extends

Cense Explosion Test Program. Report 1. Cense 1. Explosions in Sandstone

DTIC Science & Technology

1977-09-01

series, "Analysis and Summary of CENSE Data." 10 * _ CHAPTER 2 APPROACH 2.1 DESCRIPTION OF TEST SITE An exposed outcrop of Kayenta sandstone with 180...ft/s seismic velocity previously determined (References 12-14) for the unweathered upper zone of the Kayenta sandstone. 16 I The P-wave propagation...Propagation along the horizontal radial was 8400 ft/s. The seismic velocity pre- viously determined for Kayenta sandstone in this area was 7500 ft/s

Degradation processes and consolidation of Late Jurassic sandstone dinosaur tracks in museum environment (Museum of Lourinhã, Portugal)

NASA Astrophysics Data System (ADS)

Leal, Sofia; mateus, Octavio; Tomas, Carla; Dionisio, Amelia

2014-05-01

The current study aims to conciliate conservation and restoration museology diagnosis with paleontological and geological curational needs and has, as subject of study, dinosaur footprints (vertebrates fossils). The footprints have been being exposed since 2004 in the paleontology hall of the Museum of Lourinhã, Portugal, and are part of a important paleontological collection of Late Jurassic vertebrate fossils from Lourinhã Formation. Presently, it is considered a unique heritage in danger of disappearing due to high decay level of disaggregation of its geological structure. The dinosaur footprints, (ML557) found, more precisely, on a coastline cliff in Lourinhã, Porto das Barcas, Lagido do Forno (coordinate 39° 14. 178'N, 9° 20. 397'W), Jurassic period, on the 5th of June 2001, by Jesper Milàn. This cliff of high slope presents sedimentary stratigraphic characteristics of a sandstone/siltstone of gray and red colors, by the '' Munsell scale and Color Chart''. Geological the tracks are Late Jurassic in age, and colected in the Lourinhã Formation, Praia Azul Member, of the Lusitanian Basin. There are three natural infills tridactyl tracks, possibly ascribed to ornithopod, a bipedal herbivore, resultant of a left foot movement, right and left. Footprints have 300-400mm of wide and 330-360mm of height with round fingers, which are elongated due to some degradation/erosion. In 2001, the footprints were collected from the field, cleaned, consolidated and glued in the laboratory of the Museum of Lourinhã before being exhibited in a museum display. Stone matrix was removed and a consolidation product applied, probably a polyvinyl acetate, of the brand Plexigum. The footprint with broken central digit was glued with an epoxy resin, Araldite. Both applied products were confirmed by analysis of µ-FTIR (Fourier Transform Infrared Spectroscopy) and both presented colour change and detachment surface problems. After collecting and storing, in 2004, footprints were

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

USGS Publications Warehouse

Reynolds, R.L.; Reheis, M.C.; Neff, J.C.; Goldstein, H.; Yount, J.

2006-01-01

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3-4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution

Geology of deep-water sandstones in the Mississippi Stanley Shale at Cossatot Falls, Arkansas

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

Coleman, J.L. Jr.

1993-09-01

The Mississippian Stanley Shale crops out along the Cossatot River in the Ouachita Mountains of western Arkansas. Here, exposures of deep-water sandstones and shales, on recently established public lands, present a rare, three-dimensional look at sandstones of the usually obscured Stanley. Cossatot Falls, within the Cossatot River State Park Natural Area, is a series of class IV and V rapids developed on massive- to medium-bedded quartz sandstones on the northern flank of an asymmetric, thrust-faulted anticline. In western Arkansas, the Stanley Shale is a 10,000-ft (3200-m) succession of deep-water sandstone and shale. At Cossatot Falls, approximately 50 ft (155 m)more » of submarine-fan-channel sedimentary rocks are exposed during low-river stages. This section is composed primarily of sets of thinning-upward sandstone beds. With rare exceptions, the sandstones are turbidites, grading from massive, homogeneous, basal beds upward through festoon-cross-bedded thick beds, into rippled medium and thin beds. Sandstone sets are capped by thin shales and siltstones. Regional, north-northwestward paleocurrent indicators are substantiated by abundant, generally east-west ripple crests asymmetric to the north-northwest. Flute casts at the top of the sandstone sequence indicate an additional east-ward flow component. Based on regional, lithologic characteristics, the sandstones at Cossatot Falls appear to be within the Moyers Formation. The Moyers is the upper sandstone unit of the Stanley and is an oil and gas reservoir in the eastern Oklahoma Ouachita Mountains.« less

Effects of Pisha sandstone content on solute transport in a sandy soil.

PubMed

Zhen, Qing; Zheng, Jiyong; He, Honghua; Han, Fengpeng; Zhang, Xingchang

2016-02-01

In sandy soil, water, nutrients and even pollutants are easily leaching to deeper layers. The objective of this study was to assess the effects of Pisha sandstone on soil solute transport in a sandy soil. The miscible displacement technique was used to obtain breakthrough curves (BTCs) of Br(-) as an inert non-adsorbed tracer and Na(+) as an adsorbed tracer. The incorporation of Pisha sandstone into sandy soil was able to prevent the early breakthrough of both tracers by decreasing the saturated hydraulic conductivity compared to the controlled sandy soil column, and the impeding effects increased with Pisha sandstone content. The BTCs of Br(-) were accurately described by both the convection-dispersion equation (CDE) and the two-region model (T-R), and the T-R model fitted the experimental data slightly better than the CDE. The two-site nonequilibrium model (T-S) accurately fit the Na(+) transport data. Pisha sandstone impeded the breakthrough of Na(+) not only by decreasing the saturated hydraulic conductivity but also by increasing the adsorption capacity of the soil. The measured CEC values of Pisha sandstone were up to 11 times larger than those of the sandy soil. The retardation factors (R) determined by the T-S model increased with increasing Pisha sandstone content, and the partition coefficient (K(d)) showed a similar trend to R. According to the results of this study, Pisha sandstone can successfully impede solute transport in a sandy soil column. Copyright © 2015 Elsevier Ltd. All rights reserved.

Provenance and detrital zircon geochronologic evolution of lower Brookian foreland basin deposits of the western Brooks Range, Alaska, and implications for early Brookian tectonism

USGS Publications Warehouse

Moore, Thomas; O'Sullivan, Paul B.; Potter, Christopher J.; Donelick, Raymond A.

2015-01-01

The Upper Jurassic and Lower Cretaceous part of the Brookian sequence of northern Alaska consists of syntectonic deposits shed from the north-directed, early Brookian orogenic belt. We employ sandstone petrography, detrital zircon U-Pb age analysis, and zircon fission-track double-dating methods to investigate these deposits in a succession of thin regional thrust sheets in the western Brooks Range and in the adjacent Colville foreland basin to determine sediment provenance, sedimentary dispersal patterns, and to reconstruct the evolution of the Brookian orogen. The oldest and structurally highest deposits are allochthonous Upper Jurassic volcanic arc–derived sandstones that rest on accreted ophiolitic and/or subduction assemblage mafic igneous rocks. These strata contain a nearly unimodal Late Jurassic zircon population and are interpreted to be a fragment of a forearc basin that was emplaced onto the Brooks Range during arc-continent collision. Synorogenic deposits found at structurally lower levels contain decreasing amounts of ophiolite and arc debris, Jurassic zircons, and increasing amounts of continentally derived sedimentary detritus accompanied by broadly distributed late Paleozoic and Triassic (359–200 Ma), early Paleozoic (542–359 Ma), and Paleoproterozoic (2000–1750 Ma) zircon populations. The zircon populations display fission-track evidence of cooling during the Brookian event and evidence of an earlier episode of cooling in the late Paleozoic and Triassic. Surprisingly, there is little evidence for erosion of the continental basement of Arctic Alaska, its Paleozoic sedimentary cover, or its hinterland metamorphic rocks in early foreland basin strata at any structural and/or stratigraphic level in the western Brooks Range. Detritus from exhumation of these sources did not arrive in the foreland basin until the middle or late Albian in the central part of the Colville Basin.These observations indicate that two primary provenance areas provided

Shahejie-Shahejie/Guantao/Wumishan and Carboniferous/Permian Coal-Paleozoic Total Petroleum Systems in the Bohaiwan Basin, China (based on geologic studies for the 2000 World Energy Assessment Project of the U.S. Geological Survey)

USGS Publications Warehouse

Ryder, Robert T.; Qiang, Jin; McCabe, Peter J.; Nuccio, Vito F.; Persits, Felix

2012-01-01

This report discusses the geologic framework and petroleum geology used to assess undiscovered petroleum resources in the Bohaiwan basin province for the 2000 World Energy Assessment Project of the U.S. Geological Survey. The Bohaiwan basin in northeastern China is the largest petroleum-producing region in China. Two total petroleum systems have been identified in the basin. The first, the Shahejie&ndashShahejie/Guantao/Wumishan Total Petroleum System, involves oil and gas generated from mature pods of lacustrine source rock that are associated with six major rift-controlled subbasins. Two assessment units are defined in this total petroleum system: (1) a Tertiary lacustrine assessment unit consisting of sandstone reservoirs interbedded with lacustrine shale source rocks, and (2) a pre-Tertiary buried hills assessment unit consisting of carbonate reservoirs that are overlain unconformably by Tertiary lacustrine shale source rocks. The second total petroleum system identified in the Bohaiwan basin is the Carboniferous/Permian Coal–Paleozoic Total Petroleum System, a hypothetical total petroleum system involving natural gas generated from multiple pods of thermally mature coal beds. Low-permeability Permian sandstones and possibly Carboniferous coal beds are the reservoir rocks. Most of the natural gas is inferred to be trapped in continuous accumulations near the center of the subbasins. This total petroleum system is largely unexplored and has good potential for undiscovered gas accumulations. One assessment unit, coal-sourced gas, is defined in this total petroleum system.

Rock Slope Design Criteria

DOT National Transportation Integrated Search

2010-06-01

Based on the stratigraphy and the type of slope stability problems, the flat lying, Paleozoic age, sedimentary : rocks of Ohio were divided into three design units: 1) competent rock design unit consisting of sandstones, limestones, : and siltstones ...

Petroleum produced water disposal: Mobility and transport of barium in sandstone and dolomite rocks.

PubMed

Ebrahimi, Pouyan; Vilcáez, Javier

2018-09-01

To assess the risk of underground sources of drinking water contamination by barium (Ba) present in petroleum produced water disposed into deep saline aquifers, we examined the effect of salinity (NaCl), competition of cations (Ca, Mg), temperature (22 and 60°C), and organic fracturing additives (guar gum) on the sorption and transport of Ba in dolomites and sandstones. We found that at typical concentration levels of NaCl, Ca, and Mg in petroleum produced water, Ba sorption in both dolomites and sandstones is inhibited by the formation of Ba(Cl) + complexes in solution and/or the competition of cations for binding sites of minerals. The inhibition of Ba sorption by both mechanisms is greater in dolomites than in sandstones. This is reflected by a larger decrease in the breakthrough times of Ba through dolomites than through sandstones. We found that the presence of guar gum has little influence on the sorption and thus the transport of Ba in both dolomites and sandstones. Contrary to most heavy metals, Ba sorption in both dolomites and sandstones decreases with increasing temperature, however the reducing effect of temperature on Ba sorption is relevant only at low salinity conditions. Higher inhibition of Ba sorption in dolomites than in sandstones is due to the greater reactivity of dolomite over sandstone. The results of this study which includes the formulation of a reactive transport model and estimation of partition coefficients of Ba in dolomites and sandstones have significant implications in understanding and predicting the mobility and transport of Ba in deep dolomite and sandstone saline aquifers. Copyright © 2018 Elsevier B.V. All rights reserved.

ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

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

Jennie Ridgley

2000-01-21

An additional 450 wells were added to the structural database; there are now 2550 wells in the database with corrected tops on the Juana Lopez, base of the Bridge Creek Limestone, and datum. This completes the structural data base compilation. Fifteen oil and five gas fields from the Mancos-ElVado interval were evaluated with respect to the newly defined sequence stratigraphic model for this interval. The five gas fields are located away from the structural margins of the deep part of the San Juan Basin. All the fields have characteristics of basin-centered gas and can be considered as continuous gas accumulationsmore » as recently defined by the U.S. Geological Survey. Oil production occurs in thinly interbedded sandstone and shale or in discrete sandstone bodies. Production is both from transgressive and regressive strata as redefined in this study. Oil production is both stratigraphically and structurally controlled with production occurring along the Chaco slope or in steeply west-dipping rocks along the east margin of the basin. The ElVado Sandstone of subsurface usage is redefined to encompass a narrower interval; it appears to be more time correlative with the Dalton Sandstone. Thus, it was deposited as part of a regressive sequence, in contrast to the underlying rock units which were deposited during transgression.« less

Statistical analyses on sandstones: Systematic approach for predicting petrographical and petrophysical properties

NASA Astrophysics Data System (ADS)

Stück, H. L.; Siegesmund, S.

2012-04-01

Sandstones are a popular natural stone due to their wide occurrence and availability. The different applications for these stones have led to an increase in demand. From the viewpoint of conservation and the natural stone industry, an understanding of the material behaviour of this construction material is very important. Sandstones are a highly heterogeneous material. Based on statistical analyses with a sufficiently large dataset, a systematic approach to predicting the material behaviour should be possible. Since the literature already contains a large volume of data concerning the petrographical and petrophysical properties of sandstones, a large dataset could be compiled for the statistical analyses. The aim of this study is to develop constraints on the material behaviour and especially on the weathering behaviour of sandstones. Approximately 300 samples from historical and presently mined natural sandstones in Germany and ones described worldwide were included in the statistical approach. The mineralogical composition and fabric characteristics were determined from detailed thin section analyses and descriptions in the literature. Particular attention was paid to evaluating the compositional and textural maturity, grain contact respectively contact thickness, type of cement, degree of alteration and the intergranular volume. Statistical methods were used to test for normal distributions and calculating the linear regression of the basic petrophysical properties of density, porosity, water uptake as well as the strength. The sandstones were classified into three different pore size distributions and evaluated with the other petrophysical properties. Weathering behavior like hygric swelling and salt loading tests were also included. To identify similarities between individual sandstones or to define groups of specific sandstone types, principle component analysis, cluster analysis and factor analysis were applied. Our results show that composition and porosity

Upper Paleozoic Marine Shale Characteristics and Exploration Prospects in the Northwestern Guizhong Depression, South China

NASA Astrophysics Data System (ADS)

Zhu, Zhenhong; Yao, Genshun; Lou, Zhanghua; Jin, Aimin; Zhu, Rong; Jin, Chong; Chen, Chao

2018-05-01

Multiple sets of organic-rich shales developed in the Upper Paleozoic of the northwestern Guizhong Depression in South China. However, the exploration of these shales is presently at a relatively immature stage. The Upper Paleozoic shales in the northwestern Guizhong Depression, including the Middle Devonian Luofu shale, the Nabiao shale, and the Lower Carboniferous Yanguan shale, were investigated in this study. Mineral composition analysis, organic matter analysis (including total organic carbon (TOC) content, maceral of kerogen and the vitrinite reflection (Ro)), pore characteristic analysis (including porosity and permeability, pore type identification by SEM, and pore size distribution by nitrogen sorption), methane isothermal sorption test were conducted, and the distribution and thickness of the shales were determined, Then the characteristics of the two target shales were illustrated and compared. The results show that the Upper Paleozoic shales have favorable organic matter conditions (mainly moderate to high TOC content, type I and II1 kerogen and high to over maturity), good fracability potential (brittleness index (BI) > 40%), multiple pore types, stable distribution and effective thickness, and good methane sorption capacity. Therefore, the Upper Paleozoic shales in the northern Guizhong Depression have good shale gas potential and exploration prospects. Moreover, the average TOC content, average BI, thickness of the organic-rich shale (TOC > 2.0 wt%) and the shale gas resources of the Middle Devonian shales are better than those of the Lower Carboniferous shale. The Middle Devonian shales have better shale gas potential and exploration prospects than the Lower Carboniferous shales.

Rock Slope Design Criteria : Executive Summary Report

DOT National Transportation Integrated Search

2010-06-01

Based on the stratigraphy and the type of slope stability problems, the flat lying, Paleozoic age, sedimentary rocks of Ohio were divided into three design units: 1) competent rock design unit consisting of sandstones, limestones, and siltstones that...

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

McCollum, L.B.; Buchanan, J.P.; McCollum, M.B.

The Antler orogeny is a textbook example of a Paleozoic mountain building and crustal shortening event in western North America. A relatively complex geologic history of the type Antler at Battle Mountain, Nevada, is interpreted as distinct thrust plates of Lower Cambrian Scott Canyon Formation, Upper Cambrian Harmony Sandstone, and Ordovician Valmy Formation, overlain unconformably by the Middle Pennsylvanian Battle Formation. Mississippian crustal deformation and emplacement of the Roberts Mountain thrust have previously been thought to characterize the Antler orogen. Detailed sedimentology studies of the Scott Canyon and Harmony, and the relationship with the overlying Battle Formation at the typemore » section of the Antler orogeny, cast doubt on the previously accepted geologic history. The Scott Canyon is an interbedded sequence of pillow basalts, Late Devonian radiolarian cherts, and mudstone debris flows with numerous limestone olistoliths, many containing undescribed archaeocyathid fauna. The contact of the Harmony with the Battle Formation appears channeled, but otherwise conformable, and the Battle has been interpreted as an alluvial fan facies. The paleoenvironmental interpretation of these sediments is that the Scott Canyon was deposited upon a Late Devonian active continental margin setting, with prograding fan deposits of the Harmony Sandstone, overlain by Middle Pennsylvanian fanglomerates of the Battle Formation. This conformable sequence appears to preclude any major uplift within the type Antler orogen.« less

Evidence for preferential flow through sandstone aquifers in Southern Wisconsin

USGS Publications Warehouse

Swanson, S.K.; Bahr, J.M.; Bradbury, K.R.; Anderson, K.M.

2006-01-01

Sandstones often escape extensive hydrogeologic characterization due to their high primary porosity and perceived homogeneity of permeability. This study provides evidence for laterally extensive, high permeability zones in the Tunnel City Group, an undeformed, Cambrian-aged sandstone unit that exists in the subsurface throughout much of central and southern Wisconsin, USA. Several discrete high-permeability zones were identified in boreholes using flow logging and slug tests, and the interconnectedness of the features was tested using a site-specific numerical model for springs in the region. Explicit incorporation of a high-permeability layer leads to improvements in the flux calibration over simulations that lack the features, thus supporting the hydraulic continuity of high-permeability zones in the sandstone aquifer over tens of kilometers. The results suggest that stratigraphically controlled heterogeneities like contrasts in lithology or bedding-plane fractures, which have been shown to strongly influence the flow of groundwater in more heterogeneous sedimentary rocks, may also deserve close examination in sandstone aquifers. ?? 2005 Elsevier B.V. All rights reserved.

Integrated geomechanical, petrographical and petrophysical study of the sandstones of the Wajid Group, SW Saudi Arabia

NASA Astrophysics Data System (ADS)

Benaafi, Mohammed; Hariri, Mustafa; Al-Shaibani, Abdulaziz; Abdullatif, Osman; Makkawi, Mohammed

2018-07-01

The Cambro-Permian siliciclastic succession in southwestern Saudi Arabia is represented by the Wajid Group, which consists mainly of fluvial, shallow marine, aeolian, and glacial sandstones. The Wajid Group comprises the Dibsiyah, Sanamah, Qalibah, Khusayyayn, and Juwayl Formations. It is exposed in the Wadi Al-Dawasir area and extends to Najran City. The sandstones of the Wajid Group serve as groundwater aquifers in the Wadi Al-Dawasir and Najran areas and host hydrocarbon (mainly gas) reservoirs in the Rub' Al-Khali Basin. This study aims to characterize the geomechanical properties (rock strength and Young's modulus) of the sandstones of the Wajid Group using field and experimental techniques. A further objective is to investigate the relationships between the geomechanical properties and the petrographical and petrophysical properties of the studied sandstones. The geomechanical properties of the studied sandstones vary from glacial to non-glacial sandstones, as the glacial sandstones display high values of the geomechanical properties with high variability indices. Four geological factors including grain size, cement content, porosity and permeability were observed as the main controls on the geomechanical behaviour of the studied sandstones except for the Khusayyayn sandstone, where the mineral composition was also important. Significant correlations were observed between the petrographical and petrophysical properties and the geomechanical properties of the glacial sandstones. Predictive models of the geomechanical properties (RN, UCS, and E) were generated using regression analysis to account for the glacial sandstones.

CO2 Storage Potential of the Eocene Tay Sandstone, Central North Sea, UK

NASA Astrophysics Data System (ADS)

Gent, Christopher; Williams, John

2017-04-01

Carbon Capture and Storage (CCS) is crucial for low-carbon industry, climate mitigation and a sustainable energy future. The offshore capacity of the UK is substantial and has been estimated at 78 Gt of CO2 in saline aquifers and hydrocarbon fields. The early-mid Eocene Tay Sandstone Member of the Central North Sea (CNS) is a submarine-fan system and potential storage reservoir with a theoretical capacity of 123 Mt of CO2. The Tay Sandstone comprises of 4 sequences, amalgamating into a fan complex 125km long and 40 km at a minimum of 1500 m depth striking NW-SE, hosting several hydrocarbon fields including Gannett A, B, D and Pict. In order to better understand the storage potential and characteristics, the Tay Sandstone over Quadrant 21 has been interpreted using log correlation and 3D seismic. Understanding the internal and external geometry of the sandstone as well as the lateral extent of the unit is essential when considering CO2 vertical and horizontal fluid flow pathways and storage security. 3D seismic mapping of a clear mounded feature has revealed the youngest sequence of the Tay complex; a homogenous sand-rich channel 12 km long, 1.5 km wide and on average 100 m thick. The sandstone has porosity >35%, permeability >5 D and a net to gross of 0.8, giving a total pore volume of 927x106 m3. The remaining three sequences are a series of stacked channels and interbedded mudstones which are more quiescent on the seismic, however, well logs indicate each subsequent sequence reduce in net to gross with age as mud has a greater influence in the early fan system. Nevertheless, the sandstone properties remain relatively consistent and are far more laterally extensive than the youngest sequence. The Tay Sandstone spatially overlaps several other potential storage sites including the older Tertiary sandstones of the Cromarty, Forties and Mey Members and deeper Jurassic reservoirs. This favours the Tay Sandstone to be considered in a secondary or multiple stacked

Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

NASA Astrophysics Data System (ADS)

Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

2017-08-01

There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

NASA Astrophysics Data System (ADS)

Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

2018-06-01

There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

Sedimentological controls on gold in a late Pleistocene glacial placer deposit, Cariboo Mining District, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Eyles, Nicholas; Kocsis, Stephen P.

1989-11-01

It is a widely perceived notion that glaciation results in dispersal of mineralized bedrock and that sedimentary concentrates of economic minerals (placers) rarely occur in glaciated basins. This paper describes economic gold placers within late Pleistocene glacial and related fluvial sediments of the Cariboo Mining District in central British Columbia, Canada. The area has been defined as a "giant" gold placer; total production since 1858 is over 93,000 kg. The oldest and volumetrically largest placers occur in fluvial gravels and valley-side fan deposits deposited during a long non-glacial interval from as early as 125,000 to 30,000years B.P. The richest placers are found along bedrock "gutters" in the deepest parts of valleys, indicating repeated fluvial reworking of the valley infills. Braided and "wandering gravel bed" fluvial facies can be identified. Glacial placers, that overlie the fluvial placers, occur within lodgement till complexes deposited below the late Wisconsin Cordilleran ice sheet after 30,000 years B.P. The basal portions of lodgement tills are commonly enriched in gold as a result of incorporation from older gravels. Subglacial meltwaters created a highly effective sluicing system and left lucrative pay zones along meltwater-cut channels on bedrock benches, within intraformational gravels in lodgement till and within "lee-side" deposits down-ice of bedrock highs. "Lee-side" deposits are essentially water-worked talus slopes that accumulated in subglacial cavities. Finally, postglacial "wandering gravel-bed rivers" have repeatedly reworked older placers resulting in rich pay zones at the base of extensive bar platform deposits. Similar sedimentological controls on gold distribution can be identified in other glacial placers of late Cenozoic and Paleozoic age in North America, southern Africa and Australia. A distinction is drawn between these placers, all characterized by coarse-grained, nuggety gold, and the more well-known Precambrian and

Factors controlling reservoir quality in tertiary sandstones and their significance to geopressured geothermal production

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

Loucks, R.G.; Richmann, D.L.; Milliken, K.L.

1981-01-01

Variable intensity of diagenesis is the factor primarily responsible for contrasting regional reservoir quality of Tertiary sandstones from the upper and lower Texas coast. Detailed comparison of Frio sandstone from the Chocolate Bayou/Danbury Dome area, Brazoria County, and Vicksburg sandstones from the McAllen Ranch Field area, Hidalgo County, reveals that extent of diagenetic modification is most strongly influenced by (1) detrital mineralogy and (2) regional geothermal gradients. The regional reservoir quality of Frio sandstones from Brazoria County is far better than that characterizing Vicksburg sandstones from Hidalgo County, especially at depths suitable for geopressured geothermal energy production. However, in predictingmore » reservoir quality on a site-specific basis, locally variable factors such as relative proportions for porosity types, pore geometry as related to permeability, and local depositional environment must also be considered. Even in an area of regionally favorable reservoir quality, such local factors can significantly affect reservoir quality and, hence, the geothermal production potential of a specific sandstone unit.« less

A New Basal Sauropodomorph Dinosaur from the Lower Jurassic Navajo Sandstone of Southern Utah

PubMed Central

Sertich, Joseph J. W.; Loewen, Mark A.

2010-01-01

Background Basal sauropodomorphs, or ‘prosauropods,’ are a globally widespread paraphyletic assemblage of terrestrial herbivorous dinosaurs from the Late Triassic and Early Jurassic. In contrast to several other landmasses, the North American record of sauropodomorphs during this time interval remains sparse, limited to Early Jurassic occurrences of a single well-known taxon from eastern North America and several fragmentary specimens from western North America. Methodology/Principal Findings On the basis of a partial skeleton, we describe here a new basal sauropodomorph dinosaur from the Lower Jurassic Navajo Sandstone of southern Utah, Seitaad ruessi gen. et sp. nov. The partially articulated skeleton of Seitaad was likely buried post-mortem in the base of a collapsed dune foreset. The new taxon is characterized by a plate-like medial process of the scapula, a prominent proximal expansion of the deltopectoral crest of the humerus, a strongly inclined distal articular surface of the radius, and a proximally and laterally hypertrophied proximal metacarpal I. Conclusions/Significance Phylogenetic analysis recovers Seitaad as a derived basal sauropodomorph closely related to plateosaurid or massospondylid ‘prosauropods’ and its presence in western North America is not unexpected for a member of this highly cosmopolitan clade. This occurrence represents one of the most complete vertebrate body fossil specimens yet recovered from the Navajo Sandstone and one of the few basal sauropodomorph taxa currently known from North America. PMID:20352090

Assessment of Paleozoic shale gas resources in the Sichuan Basin of China, 2015

USGS Publications Warehouse

Potter, Christopher J.; Schenk, Christopher J.; Charpentier, Ronald R.; Gaswirth, Stephanie B.; Klett, Timothy R.; Leathers, Heidi M.; Brownfield, Michael E.; Mercier, Tracey J.; Tennyson, Marilyn E.; Pitman, Janet K.

2015-10-14

Using a geology-based assessment methodology, the U.S. Geological Survey estimated a mean of 23.9 trillion cubic feet of technically recoverable shale gas resources in Paleozoic formations in the Sichuan Basin of China.

Energy evolution mechanism in process of Sandstone failure and energy strength criterion

NASA Astrophysics Data System (ADS)

Wang, Yunfei; Cui, Fang

2018-07-01

To reveal the inherent relation between energy change and confining pressure during the process of sandstone damage, and its characteristics of energy storage and energy dissipation in different deformation stage. Obtaining the mechanical parameters by testing the Sandstone of two1 coal seam roof under uniaxial compression in Zhaogu coalmine, using Particle Flow Code (PFC) and fish program to get the meso-mechanical parameters, studying Sandstone energy evolution mechanism under different confining pressures, and deducing energy strength criterion based on energy principle of rock failure, some main researching results are reached as follows: with the increasing of confining pressure, the Sandstone yield stage and ductility increases, but brittleness decreases; Under higher confining pressure, the elastic strain energy of Sandstone before peak approximately keeps constant in a certain strain range, and rock absorbs all the energy which converts into surface energy required for internal damage development; Under lower confining pressure, Sandstone no longer absorbs energy with increasing strain after peak under lower confining pressure, while it sequentially absorbs energy under higher confining pressure; Under lower confining pressure, the energy Sandstone before peak absorbed mainly converts into elastic strain energy, while under higher confining pressure, dissipation energy significantly increases before peak, which indicates that the degree rock strength loss is higher under higher confining pressure; with the increasing of confining pressure, the limit of elastic strain energy increases and there exists a favourable linear variation relationship; At the peak point, the ratio of elastic strain energy to total energy of Sandstone nonlinearly decreases, while the ratio of dissipation energy to total energy nonlinearly increases with the increasing of confining pressure; According to energy evolution mechanism of rock failure, an energy strength criterion is

The Point Lookout Sandstone: a tale of two cores, or petrology, diagenesis, and reservoir properties of Point Lookout Sandstone, Southern Ute Indian Reservation, San Juan Basin, Colorado

USGS Publications Warehouse

Keighin, C.W.; Zech, R.S.; Dunbar, R.W.

1993-01-01

The Point Lookout sandstones are quartz-rich, fine to very-fine grained, and contain moderately variable quantities of potassium feldspar (2 to 20 modal percent) and lithic fragments (9 to 20 modal percent). Locally, sandstone is tightly cemented by carbonate cement; clays are not important as cementing agents, although they significantly reduce permeability of some samples. Pores are small; many are intergranular micropores between crystals of authigenic clay. Depositional environments are highly variable and range from lower shoreface to coastal plain and include minor deltaic environments. The best reservoir characteristics are generally in the upper shoreface sandstones. -from Authors

Traces of the heritage arising from the Macelj sandstone

NASA Astrophysics Data System (ADS)

Golež, Mateja

2014-05-01

The landscape of Southeast Slovenia and its stone heritage principally reveal itself through various Miocene sandstones. The most frequently found type on the borderline between Slovenia and Croatia, i.e. east of Rogatec, is the micaceous-quartz Macelj sandstone. This rock ranges in colour from greenish grey to bluish grey and yellowish, depending on the content of glauconite, which colours it green. In its composition, the rock is a heterogeneous mixture of grains of quartz, dolomite, muscovite, microcline, anorthite and glauconite. The average size of grains is 300μm. In cross-section, they are oblong, semi-rounded or round. The mechanical-physical and durability properties of the Macelj sandstone, which have been characterised pursuant to the applicable standards for natural stone, reveal that the rock exhibits poor resistance to active substances from the atmosphere, particularly in the presence of salt. In the surroundings of Rogatec, there are around 45 abandoned quarries of the Macelj sandstone, which are the result of the exploitation of this mineral resource from the 17th century on. The local quarrymen earned their bread until 1957, when the Kambrus quarry industry closed down. From the original use of this mineral resource as construction and decorative material, the useful value of the Macelj sandstone expanded during the development of the metals industry to the manufacture of large and small grindstones for the needs of the domestic and international market. Therefore, traces of quarrying can not only be seen in the disused quarries, but also in the rich architectural heritage of Rogatec and its surroundings, the stone furniture - from portals, window frames, wells, various troughs, pavements to stone walls - and other. The living quarrying heritage slowly passed into oblivion after World War II, although the analysis of the social image of the people residing in Rogatec and its surroundings revealed that there was an average of one stonemason in

Revised version of the Cenozoic Collision along the Zagros Orogen, Insights from Cr-spinel and Sandstone Modal Analyses.

PubMed

Gholami Zadeh, Parisa; Adabi, Mohammad Hossein; Hisada, Ken-Ichiro; Hosseini-Barzi, Mahboubeh; Sadeghi, Abbas; Ghassemi, Mohammad Reza

2017-09-07

Geoscientists have always considered the Neyriz region, located along the Zagros Suture Zone, an important area of interest because of the outcrops of Neotethys ophiolitic rocks. We carried out a modal analysis of the Cenozoic sandstones and geochemistry of the detrital Cr-spinels at Neyriz region in order to determine their provenance and tectonic evolution in the proximal part of Zagros Basin. Our data shows a clear change in provenance from the Late Cretaceous onwards. As from the Late Cretaceous to Eocene, lithic grains are mostly chert and serpentinite; and higher Cr# values of the detrital Cr-spinel compositions indicate that they originate from the fore-arc peridotites and deposited in an accretionary prism setting during this period. From the Late Oligocene to the Miocene periods, volcaniclastic and carbonate lithic grains show an increasing trend, and in the Miocene, metasedimentary lithic grains appear in the sediments. Ophiolite obduction caused a narrow trough sub-basin to be formed parallel to the general trend of the Zagros Orogeny between the Arabian and Iranian plates in Oligocene. From the Miocene onwards, the axial metamorphic complex belt was uplifted in the upper plate. Therefore, the collision along the Zagros Suture Zone must have occurred in the Late Oligocene.

Influence of Water Saturation on Thermal Conductivity in Sandstones

NASA Astrophysics Data System (ADS)

Fehr, A.; Jorand, R.; Koch, A.; Clauser, C.

2009-04-01

Information on thermal conductivity of rocks and soils is essential in applied geothermal and hydrocarbon maturation research. In this study, we investigate the dependence of thermal conductivity on the degree of water saturation. Measurements were made on five sandstones from different outcrops in Germany. In a first step, we characterized the samples with respect to mineralogical composition, porosity, and microstructure by nuclear magnetic resonance (NMR) and mercury injection. We measured thermal conductivity with an optical scanner at different levels of water saturation. Finally we present a simple and easy model for the correlation of thermal conductivity and water saturation. Thermal conductivity decreases in the course of the drying of the rock. This behaviour is not linear and depends on the microstructure of the studied rock. We studied different mixing models for three phases: mineral skeleton, water and air. For argillaceous sandstones a modified arithmetic model works best which considers the irreducible water volume and different pore sizes. For pure quartz sandstones without clay minerals, we use the same model for low water saturations, but for high water saturations a modified geometric model. A clayey sandstone rich in feldspath shows a different behaviour which cannot be explained by simple models. A better understanding will require measurements on additional samples which will help to improve the derived correlations and substantiate our findings.

Dependence of Thermal Conductivity on Water Saturation of Sandstones

NASA Astrophysics Data System (ADS)

Fehr, A.; Jorand, R.; Koch, A.; Clauser, C.

2008-12-01

Information on thermal conductivity of rocks and soils is essential in applied geothermal and hydrocarbon maturation research. In this study, we investigate the dependence of thermal conductivity on the degree of water saturation. Measurements were made on five sandstones from different outcrops in Germany. In a first step, we characterized the samples with respect to mineralogical composition, porosity, and microstructure by nuclear magnetic resonance (NMR) and mercury injection. We measured thermal conductivity with an optical scanner at different levels of water saturation. Finally we present a simple and easy model for the correlation of thermal conductivity and water saturation. Thermal conductivity decreases in the course of the drying of the rock. This behaviour is not linear and depends on the microstructure of the studied rock. We studied different mixing models for three phases: mineral skeleton, water and air. For argillaceous sandstones a modified arithmetic model works best which considers the irreducible water volume and different pore sizes. For pure quartz sandstones without clay minerals, we use the same model for low water saturations, but for high water saturations a modified geometric model. A clayey sandstone rich in feldspath shows a different behaviour which cannot be explained by simple models. A better understanding will require measurements on additional samples which will help to improve the derived correlations and substantiate our findings.

Basal Adare volcanics, Robertson Bay, North Victoria Land, Antarctica: Late Miocene intraplate basalts of subaqueous origin

USGS Publications Warehouse

Mortimer, N.; Dunlap, W.J.; Isaac, M.J.; Sutherland, R.P.; Faure, K.

2007-01-01

Late Cenozoic lavas and associated hyaloclastite breccias of the Adare volcanics (Hallett volcanic province) in Robertson Bay, North Victoria Land rest unconformably on Paleozoic greywackes. Abundant hyaloclastite breccias are confined to a paleovalley; their primary geological features, and the stable isotope ratios of secondary minerals, are consistent with eruption in a subaqueous environment with calcite formation probably involving seawater. In contrast, the lavas which stratigraphically overlie the hyaloclastites on Mayr Spur probably were erupted subaerially. K-Ar dating of eight samples from this basal sequence confirms the known older age limit (Late Miocene) of the Hallett volcanic province. Geochemical data reveal an ocean island basalt-like affinity, similar to other Cenozoic igneous rocks of the Hallett volcanic province. If a submarine eruptive paleoenvironment is accepted then there has been net tectonic or isostatic post-Late Miocene uplift of a few hundred metres in the Robertson Bay-Adare Peninsula area

Publications - SR 53 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

Group; Lead; Limestone; Lode; Marble; Mercury; Mesozoic; Metallurgy; Metamorphic Rocks; Mineral Pluton; Nickel; Nikolai Greenstone; Noatak Sandstone; Nome Group; Nuggets; Orca Group; Ordovician; Ores ; Paleozoic; Palladium; Pennsylvanian; Placer; Platinum; Platinum Group Elements; Plutonic; Plutonic Hosted

Sedimentological reservoir characteristics of the Paleocene fluvial/lacustrine Yabus Sandstone, Melut Basin, Sudan

NASA Astrophysics Data System (ADS)

Mahgoub, M. I.; Padmanabhan, E.; Abdullatif, O. M.

2016-11-01

Melut Basin in Sudan is regionally linked to the Mesozoic-Cenozoic Central and Western African Rift System (CWARS). The Paleocene Yabus Formation is the main oil producing reservoir in the basin. It is dominated by channel sandstone and shales deposited in fluvial/lacustrine environment during the third phase of rifting in the basin. Different scales of sedimentological heterogeneities influenced reservoir quality and architecture. The cores and well logs analyses revealed seven lithofacies representing fluvial, deltaic and lacustrine depositional environments. The sandstone is medium to coarse-grained, poorly to moderately-sorted and sub-angular to sub-rounded, arkosic-subarkosic to sublitharenite. On the basin scale, the Yabus Formation showed variation in sandstone bodies, thickness, geometry and architecture. On macro-scale, reservoir quality varies vertically and laterally within Yabus Sandstone where it shows progressive fining upward tendencies with different degrees of connectivity. The lower part of the reservoir showed well-connected and amalgamated sandstone bodies, the middle to the upper parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenetic changes such as compaction, cementation, alteration, dissolution and kaolinite clays pore fill and coat all have significantly reduced the reservoir porosity and permeability. The estimated porosity in Yabus Formation ranges from 2 to 20% with an average of 12%; while permeability varies from 200 to 500 mD and up to 1 Darcy. The understanding of different scales of sedimentological reservoir heterogeneities might contribute to better reservoir quality prediction, architecture, consequently enhancing development and productivity.

A reexamination of the Pennsylvanian trace fossil Olivellites

USGS Publications Warehouse

Yochelson, Ellis L.; Schindel, David E.

1978-01-01

The original interpretation of Olivellites plummeri Fenton and Fenton as the trace of an infaunal gastropod, is reconsidered and rejected. The original slab bearing several examples of O. plummeri has been reexamined and reillustrated. The slab came from the type-locality of O. plummeri in Eastland County, Tex., and is a shallow sub tidal sandstone of the Graham Formation; the sandstone, which has yielded additional specimens, is presumably a reworked delta-front deposit. Olivellites was also observed in the Caddo Creek Formation in Stephens County, Tex., but, to date, it has not been found elsewhere in north-central Texas. Interpretation of Paleozoic ichnofossils by analogy with modern traces is limited; behavioral characteristics may be the products of post-Paleozoic innovation. The internal morphology and path of Olivellites are unlike those of any modern gastropod trail, and the genus is removed from the Mollusca.

Origin and diagenesis of clay minerals in relation to sandstone paragenesis: An example in eolian dune reservoirs and associated rocks, Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming

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

Pollastro, R.M.; Schenk, C.J.

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in the diagenetic evolution of these sandstones. Allogenic clay minerals are present in shaly rock fragments and laminae. Early infiltration of clays into porous sabkha sands commonly form characteristic menisei or bridges between framework grains or, when more extensive, form coatingsmore » or rims on grain surfaces. Authigenic clays include nearly pure smectite, mixed-layer illite/smectite (I/S), and late diagenetic illite and corrensite; these clay minerals are present as pore-lining cements. In addition to the deposition and neoformation of clay minerals throughout sandstone paragenesis, the conversion of smectite to illite occurred as temperatures increased with progressive burial. A temperature of 103C is calculated at a present depth of 3,200 m using a geothermal gradient of 30C/km and a mean annual surface temperature of 7C. After correction for uplift and erosion (250 m), the maximum calculated temperature for the conversion of all random I/S to ordered I/S is 100C. This calculated temperature is in excellent agreement with temperatures of 100-110C implied from I/S geothermometry.« less

Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt, NW China: Constraints on the initiation of a magmatic arc in the southern Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Du, Long; Long, Xiaoping; Yuan, Chao; Zhang, Yunying; Huang, Zongying; Sun, Min; Zhao, Guochun; Xiao, Wenjiao

2018-03-01

Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt (ETOB) have been studied in order to constraint the initiation of a magmatic arc formed in this region. Zircon U-Pb dating indicates that two dioritic plutons in the northern ETOB were generated in the Late Ordovician (452 ± 4 Ma) and the Early Silurian (442 ± 3 Ma), respectively. Diorites from the two plutons are characterized by enrichments in large ion lithophile elements (LILE) and highly incompatible elements, with depletions in high field strength elements (HSFE) displaying typical geochemical features of a subduction-related origin. They have positive εNd(t) values (+5.08-+6.58), relatively young Nd model ages (TDM = 0.71-1.08 Ga), with Ta/Yb (0.05-0.09) and Nb/Ta ratios (12.06-15.19) similar to those of depleted mantle, suggesting a juvenile mantle origin. Their high Ba/La (13.3-35.9), low Th/Yb (0.72-2.02), and relatively low Ce/Th (4.57-14.7) and Ba/Th (47.8-235) ratios indicate that these diorites were probably produced by partial melting of a depleted mantle wedge metasomatized by both subducted sediment-derived melts and slab-derived aqueous fluids. Zircon U-Pb dating of a granitic pluton in the northern ETOB yielded a Late Ordovician intrusion age of 447 ± 5 Ma. Granites from this pluton show calc-alkaline compositions with geochemical characteristics of I-type granites. They also show positive εNd(t) values (+6.49-+6.95) and young Nd model ages (TDM = 0.69-0.87 Ga), indicating that the granites were most likely derived from juvenile lower crust. Our new dating results on the dioritic and granitic plutons suggest that arc-type magmatism in the northern ETOB began prior to or at the Late Ordovician (452-442 Ma). In addition, north-dipping subduction of the Kangguertage oceanic lithosphere may account for the arc-type magmatism and the geodynamic process of the ETOB in the Early Paleozoic.

Eolian Signal of the Onset of the Late Paleozoic Ice Age in North America Re-Deposited and Preserved As Paleo-Cave Sediments, Southwestern Colorado, U.S.a.

NASA Astrophysics Data System (ADS)

Evans, J. E.; Soreghan, M. J.

2014-12-01

The Molas Formation is a loessite consisting of reddish silt of Early Pennsylvanian (Bashkirian) age. U-Pb age spectra of accessory zircons indicate long-distance (>2000 km) transport from the Grenville province in northeastern North America plus sources from the peri-Gondwanan terranes in southeastern North America and local sources in the Ancestral Rocky Mountains uplift. These eolian sediments formed a blanket deposit <30 m thick above a paleokarst landscape in southwestern Colorado, infilling solution valleys and burying karst towers developed on the underlying Mississippian (Tournaisian-Visean) Leadville Limestone. The loessite is an eolian signal for the probable onset of glaciation at multiple locations in tectonically uplifted mountainous areas in North America. However, the loessite is easily eroded and has low preservation potential. Prior to lithification, significant amounts of the loess were remobilized and transported into the underlying karst system. As paleo-cave deposits, encased in limestone and dolostone, the silt-rich deposits have a higher preservation potential, and the eolian signal of the onset of the Late Paleozoic Ice Age in North America is still recognizable. However, the following signal modification processes need to be understood: (1) source area weathering and pedogenesis; (2) land-atmosphere transfer processes; (3) deposition effects of paleotopography, vegetation and moisture conditions, and infiltration into open fractures and/or the matrix of colluvium; (4) remobilization by surface runoff into open fractures and/or groundwater piping/sapping processes in loess soils; (5) transport into vadose and phreatic karst passageways by episodic ("streamflood") hydrologic events, forming event deposits (debrites, inundites, and jointites); (6) breakout dome collapse (forming interbedded cave sediments, karst breccias, and speleothems); (7) lithification and diagenesis; (8) post-lithification modification including pervasive hydrothermal

Ancient Laurentian detrital zircon in the closing Iapetus Ocean, Southern Uplands terrane, Scotland

NASA Astrophysics Data System (ADS)

Waldron, John W. F.; Floyd, James D.; Simonetti, Antonio; Heaman, Larry M.

2008-07-01

Early Paleozoic sandstones in the Southern Uplands terrane ofScotland were deposited during closure of the Iapetus Oceanbetween Laurentia and Avalonia. Their tectonic setting and sourcesare controversial, and different authors have supported subduction-accretion,extensional continental-margin development, or back-arc basinsettings. We report new U-Pb detrital zircon ages from fiveLate Ordovician sandstones from the Northern Belt of the SouthernUplands and test models of their tectonic setting. The U-Pbzircon age distributions are dominated by peaks characteristicof sources in Laurentia and include grains as old as 3.6 Ga,older than any previously recorded in the British CaledonidesSE of the Laurentian foreland. Discordant grains in one samplesuggest derivation via erosion of metasedimentary rocks incorporatedin the Grampian-Taconian orogen. Rare Neoproterozoic grains,previously interpreted as originating from a peri-Gondwananterrane, may be derived from igneous rocks associated with Iapetanrifting. Only rare zircons are contemporary with the depositionalages. The results are difficult to reconcile with extensionalcontinental-margin and back-arc models, but they support anactive continental-margin subduction-accretion model. Closesimilarities with distributions from the Newfoundland Appalachiansare consistent with sinistral transpression during closing ofthe Iapetus Ocean.

Reservoir sedimentology of the Big Injun sandstone in Granny Creek field, West Virginia

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

Zou, Xiangdong; Donaldson, K.; Donaldson, A.C.

1992-01-01

Big Injun sandstones of Granny Creek oil field (WV) are interpreted as fluvial-deltaic deposits from core and geophysical log data. The reservoir consists of two distinctive lithologies throughout the field; fine-grained sandstones overlain by pebbly and coarse-grained sandstones. Lower fine-grained sandstones were deposited in westward prograding river-mouth bars, where distal, marine-dominant proximal, and fluvial-dominant proximal bar subfacies are recognized. Principal pay is marine-influenced proximal bar, where porosity ranges from 13 to 23% and permeability, up to 24 md. Thin marine transgressive shales and their laterally equivalent low-permeability sandstones bound time-rock sequences generally less than 10 meters thick. Where field mapped,more » width of prograding bar sequence is approximately 2.7 km (dip trend), measured from truncated eastern edge (pre-coarse-grained member erosional surface) to distal western margin. Dip-trending elongate lobes occur within marine-influenced proximal mouth-bar area, representing thickest part of tidally influenced preserved bar. Upper coarse-grained part of reservoir consists of pebbly sandstones of channel fill from bedload streams. Laterally persistent low permeability cemented interval in lower part commonly caps underlying pay zone and probably serves as seal to vertical oil migration. Southwest paleoflow trends based on thickness maps of unit portent emergence of West Virginia dome, which influences erosion patterns of pre-Greenbrier unconformity for this combination oil trap.« less

Palaeogeography of Late Triassic red-beds in Singapore and the Indosinian Orogeny

NASA Astrophysics Data System (ADS)

Oliver, Grahame; Prave, Anthony

2013-10-01

A red-bed facies of the Upper Triassic Jurong Formation has been logged on Sentosa Island, Singapore. An overall coarsening and thickening-upward pattern is well developed. The lower part of the section is dominated by purple-red, massive to finely laminated illite-smectite-kaolin-rich mudstones containing thin, discontinuous lenses of fine sandstone marked by low-angle lamination and small ripples. One dinosaur-like foot print has been discovered in a loose block of red mudstone. It is concluded that this is a lacustrine sequence and it is proposed to name the lake, Lake Sentosa. The upper part of the sequence consists of flat-laminated to trough cross-bedded medium-grained sandstone and granule to cobble conglomerates alternating with purple-red mudstone. The mudstone-sandstone packages are arranged in decametre-scale coarsening-upward cycles. The channelling and decimetre-scale cross-bedding characterising the sandstone and conglomeratic beds is evidence for deposition by flashy fluvial flood processes, possibly feeding into the lake as a fresh water delta. One possible dinosaur trackway in granule size conglomerate has been located. Detrital zircon U-Pb ages vary from 2.7 Ba to 209 Ma with significant populations at ˜245 Ma and 220 Ma. These ages throw light on the timing of the Indosinian Orogeny. The molasse red-beds of the Jurong Formation were deposited in a half graben formed in the hangingwall of the Bukit Timah Fault when central Peninsular Malaysia went into extension following the climax of the Indosinian Orogeny in the Late Triassic.

Publications - SR 56 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

Minerals; Iron; Jade; Jurassic; Kanayut Conglomerate; Kayak Shale; Kuskokwim Group; Lead; Limestone; Lode ; Nickel; Nikolai Greenstone; Noatak Sandstone; Nome Group; Nuggets; Orca Group; Ordovician; Ores ; Paleozoic; Palladium; Pennsylvanian; Placer; Platinum; Platinum Group Elements; Plutonic; Plutonic Hosted

Publications - SR 54 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

Minerals; Iron; Jade; Jurassic; Kanayut Conglomerate; Kayak Shale; Kuskokwim Group; Lead; Limestone; Lode ; Nickel; Nikolai Greenstone; Noatak Sandstone; Nome Group; Nuggets; Orca Group; Ordovician; Ores ; Paleozoic; Palladium; Pennsylvanian; Placer; Platinum; Platinum Group Elements; Plutonic; Plutonic Hosted

Publications - SR 57 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

; Kanayut Conglomerate; Kayak Shale; Kuskokwim Group; Lead; Limestone; Lode; Marble; Massive Sulfides ; Noatak Sandstone; Nome Group; Nuggets; Orca Group; Ordovician; Ores; Paleozoic; Palladium; Pennsylvanian ; Placer; Platinum; Platinum Group Elements; Plutonic; Plutonic Hosted; Plutonic Rocks; Polymetallic Vein

Publications - SR 55 | Alaska Division of Geological & Geophysical Surveys

Science.gov Websites

Minerals; Iron; Jade; Jurassic; Kanayut Conglomerate; Kayak Shale; Kuskokwim Group; Lead; Limestone; Lode ; Nickel; Nikolai Greenstone; Noatak Sandstone; Nome Group; Nuggets; Orca Group; Ordovician; Ores ; Paleozoic; Palladium; Pennsylvanian; Placer; Platinum; Platinum Group Elements; Plutonic; Plutonic Hosted

Sedimentary Provenance Constraints on the Middle Jurassic to Late Cretaceous Paleogeography of the Sichuan Basin, SW China

NASA Astrophysics Data System (ADS)

Li, Y.; He, D.; Li, D.; Lu, R.

2017-12-01

Sedimentary provenance of the Middle Jurassic to Late Cretaceous sediments in the Sichuan Basin is constrained by sandstone petrology and detrital zircon U-Pb geochronology, which provides critical insights into mid-late Mesozoic paleogeographic evolution of the Sichuan Basin. Petrographic analyses of 22 sandstone samples indicate moderate to high mature sediments and are primarily derived from cratonic or recycled sources. U-Pb age data for the Middle Jurassic to Late Cretaceous detrital zircons generally show populations at 130-200, 200-330, 400-490, 680-890, 1730-1960, and 2360-2600 Ma, with up-section variations. The Middle Jurassic sediments contain a relatively high density of 1.85 and 2.5 Ga zircons and a low density of the 800 Ma zircons, which are consistent with derivation mainly from the Songpan-Ganzi terrane and the South Qinling belt, and secondarily from the Western Jiangnan Orogen. The Late Jurassic and Early Cretaceous sedimentation with a scattered age distribution shared common multiple-source to sink systems that were predominantly draining towards the south and southeast, but increasingly drained southward, and were later disrupted by a synchronous northeastward drainage capture. Late Cretaceous sediments have a distinct reduction in <213 Ma zircons, suggesting that sedimentation involved southeastward and southwestward transport of sediments likely derived from the Songpan-Ganzi terrane, the south segment of the Longmenshan fault belt and western Yangtze Craton, and the uplifting areas of the N- and NE-Sichuan Basin. Changes in provenances during the mid-late Mesozoic period are coincident with temporal-spatial variations in depocenter migration and paleogeographic evolution of the Sichuan Basin, which are closely related to the multi-stage intracontinental subduction associated with clockwise rotation of the South China Block.

Large volume submarine ignimbrites in the Shikoku Basin: An example for explosive volcanism in the Western Pacific during the Late Miocene

NASA Astrophysics Data System (ADS)

Kutterolf, Steffen; Schindlbeck, Julie C.; Scudder, Rachel P.; Murray, Richard W.; Pickering, Kevin T.; Freundt, Armin; Labanieh, Shasa; Heydolph, Ken; Saito, Sanny; Naruse, Hajime; Underwood, Michael B.; Wu, Huaichun

2014-05-01

IODP Expedition 322, an interval of Late Miocene (7.6 to ˜9.1 Ma) tuffaceous and volcaniclastic sandstones was discovered in the Shikoku Basin (Site C0011B), Nankai region. This interval consists of bioturbated silty claystone including four 1-7 m thick interbeds of tuffaceous sandstones (TST) containing 57-82% (by volume) pyroclasts. We use major and trace element glass compositions, as well as radiogenic isotope compositions, to show that the tuffaceous sandstones beds derived from single eruptive events, and that the majority (TST 1, 2, 3a) came from different eruptions from a similar source region, which we have identified to be the Japanese mainland, 350 km away. In particular, diagnostic trace element ratios (e.g., Th/La, Sm/La, Rb/Hf, Th/Nb, and U/Th) and isotopic data indicate a marked contribution from a mantle source beneath continental crust, which is most consistent with a Japanese mainland source and likely excludes the Izu-Bonin island arc and back arc as a source region for the younger TST beds. Nevertheless, some of the chemical data measured on the oldest sandstone bed (TST 3b, Unit IIb) show affinity to or can clearly be attributed to an Izu-Bonin composition. While we cannot completely exclude the possibility that all TST beds derived from unknown and exotic Izu-Bonin source(s), the collected lines of evidence are most consistent with an origin from the paleo-Honshu arc for TST 1 through 3a. We therefore suggest the former collision zone between the Izu-Bonin arc and Honshu paleo-arc as the most likely region where the eruptive products entered the ocean, also concurrent with nearby (˜200 km) possible Miocene source areas for the tuffaceous sandstones at the paleo-NE-Honshu arc. Estimating the distribution area of the tuffaceous sandstones in the Miocene between this source region and the ˜350 km distant Expedition 322, using bathymetric constraints, we calculate that the sandstone beds represent minimum erupted magma volumes between ˜1 and

Fractures and stresses in Bone Spring sandstones

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

Warpinski, N.R.; Sattler, A.R.; Lorenz, J.C.

This project was a collaboration between Sandia National Laboratories and the Harvey E. Yates Company (Heyco), Roswell, NM, conducted under the auspices of Department of Energy's Oil Recovery Technology Partnership. The project applied Sandia perspectives on the effects of natural fractures, stress, and sedimentology for the stimulation and production of low permeability gas reservoirs to low permeability oil reservoirs, such as those typified by the Bone Spring sandstones of the Delaware Basin, southeast New Mexico. This report details the results and analyses obtained in 1990 from core, logs, stress, and other data taken from three additional development wells. An overallmore » summary gives results from all five wells studied in this project in 1989--1990. Most of the results presented are believed to be new information for the Bone Spring sandstones.« less

Development of Discrete Compaction Bands in Two Porous Sandstones

NASA Astrophysics Data System (ADS)

Tembe, S.; Baud, P.; Wong, T.

2003-12-01

Compaction band formation has been documented by recent field and laboratory studies as a localized failure mode occurring in porous sandstones. The coupling of compaction and localization may significantly alter the stress field and strain partitioning, and act as barriers within reservoirs. Two end-members of this failure mode that develop subperpendicular to the maximum principal stress have been identified: numerous discrete compaction bands with a thickness of only several grains, or a few diffuse bands that are significantly thicker. Much of what is known about discrete compaction bands derives from laboratory experiments performed on the relatively homogeneous Bentheim sandstone with 23% porosity. In this study we observe similar compaction localization behavior in the Diemelstadt sandstone, that has an initial porosity of 24.4% and a modal composition of 68% quartz, 26% feldspar, 4% oxides, and 2% micas. CT scans of the Diemelstadt sandstone indicate bedding corresponding to low porosity laminae. Saturated samples cored perpendicular to bedding were deformed at room temperature under drained conditions at a constant pore pressure of 10 MPa and a confining pressure range of 20-175 MPa. Acoustic emission activity and pore volume change were recorded continuously. Samples were deformed to axial strains of 1-4% and recovered from the triaxial cell for microstructural analysis. The mechanical data map the transition in failure mode from brittle faulting to compactive cataclastic flow. The brittle regime occurred at effective pressures up to 40 MPa, associated with failure by conjugate shear bands. At an effective pressure range of 60-175 MPa strain hardening and shear-enhanced compaction were accompanied by the development of discrete compaction bands, that was manifested by episodic surges of acoustic emission. Preliminary microstructural observations of the failed samples suggest that bedding influenced the band orientations which varies between 75-90\\deg

Degradation of Glaukonite Sandstone as a Result of Alkali-Silica Reactions in Cement Mortar.

PubMed

Czapik, Przemysław

2018-05-30

The mechanism of concrete degradation as a result of an alkali-silica reaction (ASR) largely depends on the mineral composition and microstructure of the reactive aggregate. This paper shows the reactivity results of quartz-glaukonitic sandstone, which is mainly responsible for the reactivity of some post-glacial gravels, available in Poland. After initial petrographic observations under a light microscope, the mode of sandstone degradation triggered by the reaction with sodium and potassium hydroxides was identified using scanning electron microscopy (SEM). It has been found that chalcedony agglomerates present in sandstone are separated from the rock matrix and subsequently cause the cracks formation in this matrix. Additionally, microcrystalline and potentially reactive silica is also dispersed in sandstone cement.

Elastic Dispersion and Attenuation in Fully Saturated Sandstones: Role of Mineral Content, Porosity, and Pressures

NASA Astrophysics Data System (ADS)

Pimienta, Lucas; Borgomano, Jan V. M.; Fortin, Jérôme; Guéguen, Yves

2017-12-01

Because measuring the frequency dependence of elastic properties in the laboratory is a technical challenge, not enough experimental data exist to test the existing theories. We report measurements of three fluid-saturated sandstones over a broad frequency band: Wilkenson, Berea, and Bentheim sandstones. Those sandstones samples, chosen for their variable porosities and mineral content, are saturated by fluids of varying viscosities. The samples elastic response (Young's modulus and Poisson's ratio) and hydraulic response (fluid flow out of the sample) are measured as a function of frequency. Large dispersion and attenuation phenomena are observed over the investigated frequency range. For all samples, the variation at lowest frequency relates to a large fluid flow directly measured out of the rock samples. These are the cause (i.e., fluid flow) and consequence (i.e., dispersion/attenuation) of the transition between drained and undrained regimes. Consistently, the characteristic frequency correlates with permeability for each sandstone. Beyond this frequency, a second variation is observed for all samples, but the rocks behave differently. For Berea sandstone, an onset of dispersion/attenuation is expected from both Young's modulus and Poisson's ratio at highest frequency. For Bentheim and Wilkenson sandstones, however, only Young's modulus shows dispersion/attenuation phenomena. For Wilkenson sandstone, the viscoelastic-like dispersion/attenuation response is interpreted as squirt flow. For Bentheim sandstone, the second effect does not fully follow such response, which could be due to a lower accuracy in the measured attenuation or to the occurence of another physical effect in this rock sample.

Micro-mechanics of hydro-mechanical coupled processes during hydraulic fracturing in sandstone

NASA Astrophysics Data System (ADS)

Caulk, R.; Tomac, I.

2017-12-01

This contribution presents micro-mechanical study of hydraulic fracture initiation and propagation in sandstone. The Discrete Element Method (DEM) Yade software is used as a tool to model fully coupled hydro-mechanical behavior of the saturated sandstone under pressures typical for deep geo-reservoirs. Heterogeneity of sandstone strength tensile and shear parameters are introduced using statistical representation of cathodoluminiscence (CL) sandstone rock images. Weibull distribution of statistical parameter values was determined as a best match of the CL scans of sandstone grains and cement between grains. Results of hydraulic fracturing stimulation from the well bore indicate significant difference between models with the bond strengths informed from CL scans and uniform homogeneous representation of sandstone parameters. Micro-mechanical insight reveals formed hydraulic fracture typical for mode I or tensile cracking in both cases. However, the shear micro-cracks are abundant in the CL informed model while they are absent in the standard model with uniform strength distribution. Most of the mode II cracks, or shear micro-cracks, are not part of the main hydraulic fracture and occur in the near-tip and near-fracture areas. The position and occurrence of the shear micro-cracks is characterized as secondary effect which dissipates the hydraulic fracturing energy. Additionally, the shear micro-crack locations qualitatively resemble acoustic emission cloud of shear cracks frequently observed in hydraulic fracturing, and sometimes interpreted as re-activation of existing fractures. Clearly, our model does not contain pre-existing cracks and has continuous nature prior to fracturing. This observation is novel and interesting and is quantified in the paper. The shear particle contact forces field reveals significant relaxation compared to the model with uniform strength distribution.

Unraveling multiple provenance areas using sandstone petrofacies and geochemistry: An example in the southern flank of the Golfo San Jorge Basin (Patagonia, Argentina)

NASA Astrophysics Data System (ADS)

Limarino, Carlos Oscar; Giordano, Sergio Roberto

2016-03-01

The aim of this paper is to study the provenance of Late Cretaceous sandstones deposited along the south flank of the Golfo San Jorge Basin. For this purpose, detrital modes of three hundred thirty-seven sandstone samples collected in the Mina del Carmen, Bajo Barreal, and Cañadón Seco Formations were studied in ten oil fields. According to the modal composition of the sandstones, six petrofacies were defined allowing the identification of not only principal, but also secondary provenance areas. The QVM and VQM petrofacies are more than 20% metamorphic, sedimentary, and polycrystalline quartz clasts (Lm + Ls + Qpg > 20%), evidencing a secondary signal of basement supply masked by a predominant volcanic provenance. The petrofacies VP and VF are characterized by Lm + Ls + Qpg <20% and more than 20% total feldspar (Pm + Om >20%.), which indicate a supply of sediment from volcanic terrains and scarce derivation of materials from basement rocks. Based on the plagioclase/k-feldspar ratio, the VF petrofacies is interpreted to be dominated by the supply of sand grains from the Andean volcanic-arc, while VP is supposed have originated through the erosion of intermediate volcanic rock outcroppings in the Macizo del Deseado. Finally, both the VQ and QV petrofacies show Lm + Ls + Qpg <20% and Pm + Om<20%, indicating a provenance of volcanic areas coupled with minor contributions from basement rocks. During the Late Cretaceous, the Golfo San Jorge Basin underwent a sag phase that was characterized by very scarce volcanism and tectonic activity. Although these conditions did not favor defined patterns in the vertical stacking of petrofacies, the sandstones exhibit remarkable changes in their regional distribution, which were determined by the paleogeography of the basin and differences in basement composition within the source areas. Finally, a paleogeographic model for sediment circulation in the basin is proposed. This model recognizes the main fluvial dispersal trends that

Late Jurassic - Early Cretaceous convergent margins of Northeastern Asia with Northwestern Pacific and Proto-Arctic oceans

NASA Astrophysics Data System (ADS)

Sokolov, Sergey; Luchitskaya, Marina; Tuchkova, Marianna; Moiseev, Artem; Ledneva, Galina

2013-04-01

Continental margin of Northeastern Asia includes many island arc terranes that differ in age and tectonic position. Two convergent margins are reconstructed for Late Jurassic - Early Cretaceous time: Uda-Murgal and Alazeya - Oloy island arc systems. A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk thrust-fold belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeastern Asia and Northwestern Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal island arc system were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos late Paleozoic to early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in backarc basin. Alazeya-Oloy island arc systems consists of Paleozoic and Mesozoic complexes that belong to the convergent margin between Northeastern Asia and Proto-Artic Ocean. It separated structures of the North American and Siberian continents. The Siberian margin was active whereas the North American margin was passive. The Late Jurassic was characterized by termination of a spreading in the Proto-Arctic Ocean and transformation of the latter into the closing South Anyui turbidite basin. In the beginning the oceanic lithosphere and then the Chukotka microcontinent had been subducted beneath the Alazeya-Oloy volcanic belt

Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)

NASA Astrophysics Data System (ADS)

Wolela, A.

2014-11-01

Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

Analysis of some seismic expressions of Big Injun sandstone and its adjacent interval

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

Xiangdong, Zou; Wilson, T.A.; Donaldson, A.C.

1991-08-01

The Big Injun sandstone is an important oil and gas reservoir in western West Virginia. The pre-Greenbrier unconformity has complicated correlations, and hydrocarbon explorationists commonly have misidentified the Big Injun in the absence of a regional stratigraphic study. Paleogeologic maps on this unconformity show the West Virginia dome, with the Price/Pocono units truncated resulting in pinch-outs of different sandstones against the overlying Big Lime (Greenbrier Limestone). Drillers have named the first sandstone below the Big Lime as Big Injun, and miscorrelated the real Big Injun with Squaw, upper Weir, and even the Berea sandstone. In this report, an 8-mi (13-km)more » seismic section extending from Kanawha to Clay counties was interpreted. The study area is near the pinch-out of the Big Injun sandstone. A stratigraphic cross section was constructed from gamma-ray logs for comparison with the seismic interpretation. The modeling and interpretation of the seismic section recognized the relief on the unconformity and the ability to determine facies changes, too. Both geophysical wireline and seismic data can be used for detailed stratigraphic analysis within the Granny Creek oil field of Clay and Roane countries.« less

Mechanistic study of wettability alteration of oil-wet sandstone surface using different surfactants

NASA Astrophysics Data System (ADS)

Hou, Bao-feng; Wang, Ye-fei; Huang, Yong

2015-03-01

Different analytical methods including Fourier transform infrared (FTIR), atomic force microscopy (AFM), zeta potential measurements, contact angle measurements and spontaneous imbibition tests were utilized to make clear the mechanism for wettability alteration of oil-wet sandstone surface using different surfactants. Results show that among three types of surfactants including cationic surfactants, anionic surfactants and nonionic surfactants, the cationic surfactant CTAB demonstrates the best effect on the wettability alteration of oil-wet sandstone surface. The positively charged head groups of CTAB molecules and carboxylic acid groups from crude oil could interact to form ion pairs, which could be desorbed from the solid surface and solubilized into the micelle formed by CTAB. Thus, the water-wetness of the solid surface is improved. Nonionic surfactant TX-100 could be adsorbed on oil-wet sandstone surface through hydrogen bonds and hydrophobic interaction to alter the wettability of oil-wet solid surface. The wettability alteration of oil-wet sandstone surface using the anionic surfactant POE(1) is caused by hydrophobic interaction. Due to the electrostatic repulsion between the anionic surfactant and the negatively charged surface, POE(1) shows less effect on the wettability alteration of oil-wet sandstone surface.

Using AMS to Help Interpret Glaciogenic Deposits of the Late Paleozoic Ice Age in the Parana Basin, Brazil

NASA Astrophysics Data System (ADS)

Amato, James Anthony

The term 'diamictite' is used as a lithologic descriptive term without assigning a particular origin to a rock unit as either glacial deposits (till), proglacial, glacially influenced deposits (resulting from meltwater plumes and ice rafted debris), or mass transport deposits (glacial or non-glacial related). While in some cases, it is possible to delineate between the origins of diamictites, in other instances, weathering and lack of exposures make it difficult to determine. In general, the occurrence of diamictites within the Gondwana succession has been traditionally used to indicate the occurrence of subglacial deposition despite the potential occurrence of other depositional modes. Thus, the extent of glaciation during the Late Paleozoic Ice Age is interpreted to be much greater than it actually was. . One area of interest in Gondwana where interpretation of these deposits is problematic, and hence has resulted in problems determining ice extent, is the Parana Basin in Brazil. The ability to better differentiate subglacial processes from proglacial, subaqueous mass transport, glaciomarine/glaciolacustrine rainout, and/or ice rafting, in addition to determining glacier flow or mass transport directions, will allow researchers studying these deposits to more accurately reconstruct the environments timing and extent of glaciation during the LPIA. In sedimentary fabrics, anisotropy of magnetic susceptibility (AMS) is a geophysical method, which depicts the preferred orientation of magnetic particles during the final stages of transport and/or synsedimentary deformation. The technique is used to determine the preferred orientation of the constituent grains, therefore a useful indicator to help determine the mode of deposition, direction of sediment transport, and the nature of stress and strain during deformation. In August of 2016, samples were collected from deposits assigned to the Itarare Group, which outcrop along the southern and eastern margins of the Parana

A bibliography of Paleozoic Crustacea from 1698 to 1889, including a list of North American species and a systematic arrangement of genera

USGS Publications Warehouse

Vogdes, Anthony Wayne

1890-01-01

The sole object of this bulletin is to give a general view of the literature on the Paleozoic Crustacea and to aid students and paleontologists in their researches. It is the result of more or less constant work during the past ten years.In its compilation I have examined almost every reference before recording it; those not so examined are indicated by a star (*) following the title.For convenience, the subject-matter has been arranged as follows:Part I. List of authors, including a brief index of the genera described in each work. Part II. A catalogue of the North American Paleozoic trilobites. Part III. The non-trilobitic Paleozoic Crustacea, with a list of the species.

Paleobiogeography, high-resolution stratigraphy, and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri

USGS Publications Warehouse

Cramer, Bradley D.; Kleffner, Mark A.; Brett, Carlton E.; McLaughlin, P.I.; Jeppsson, Lennart; Munnecke, Axel; Samtleben, Christian

2010-01-01

The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and ??13Ccarb chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than ??100kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (??13Ccarb) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. ?? 2010

A new bee species that excavates sandstone nests.

PubMed

Orr, Michael C; Griswold, Terry; Pitts, James P; Parker, Frank D

2016-09-12

Humanity has long been fascinated by animals with apparently unfavorable lifestyles [1]. Nesting habits are especially important because they can limit where organisms live, thereby driving population, community, and even ecosystem dynamics [2]. The question arises, then, why bees nest in active termite mounds [3] or on the rim of degassing volcanoes, seemingly preferring such hardship [4]. Here, we present a new bee species that excavates sandstone nests, Anthophora (Anthophoroides) pueblo Orr (described in Supplemental Information, published with this article online), despite the challenges already inherent to desert life. Ultimately, the benefits of nesting in sandstone appear to outweigh the associated costs in this system. Copyright © 2016 Elsevier Ltd. All rights reserved.

The petrogenesis of sodic granites in the Niujuanzi area and constraints on the Paleozoic tectonic evolution of the Beishan region, NW China

NASA Astrophysics Data System (ADS)

Yu, Jiyuan; Guo, Lin; Li, Jianxing; Li, Yanguang; Smithies, Robert H.; Wingate, Michael T. D.; Meng, Yong; Chen, Shefa

2016-07-01

Ordovician to Devonian sodic granites dominate the newly recognized Luotuojuan composite granite in the Lebaquan-Luotuojuan-Niujuanzi region of Beishan, along the southern margin of the Central Asian Orogenic Belt in NW China. The granites include sodic (K2O/Na2O > 0.5) tonalites with low Y (< 7 ppm), Yb (< 0.7 ppm), high Sr/Y (> 68) that formed during at least two events at c. 435 and c. 370-360 Ma. Their compositions are consistent with high-pressure melting of basaltic crust, although relatively non-radiogenic Nd isotope compositions (εNd(t) + 0.9) require some crustal assimilation. The interpretation that these granites reflect melts of a subducted slab (i.e. adakite) is supported by independent local and regional geological evidence for an oceanic subduction-accretion setting, including a long history of calc-alkaline magmatism and the identification of a series of early Paleozoic ophiolite belts. Other sodic granites forming the Luotuojuan composite granite are mainly quartz-diorite and granodiorite formed between c. 391 and c. 360 Ma. These rocks are not adakites, having Sr concentrations and Sr/Y ratios too low and Y and Yb concentrations too high. They are low- to medium-K calc-alkaline rocks more typical of magmas derived through melting in a subduction modified mantle wedge. Compositional changes from sodic to potassic granites, over time frames consistent with subduction processes, suggest at least two separate cycles, or pulses, of hot subduction in the Lebaquan-Luotuojuan-Niujuanzi region. Although early Paleozoic adakites have been inferred to exist elsewhere in the Beishan region, many of the reported adakitic rocks have compositions inconsistent with melting of subducted oceanic lithosphere and so tectonic interpretation of hot subduction might not be valid in these cases. A study of regional granite data also shows not only that adakite magmatism does not extend into the Permian but that if subduction-accretion processes extended into the late

Influence of depositional environment on diagenesis in St. Peter sandstone, Michigan basin

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

Lundgren, C.E. Jr.; Barnes, D.A.

1989-03-01

The Middle Ordovician St. Peter Sandstone in the Michigan basin was deposited in marine peritidal to storm-dominated, outer shelf depositional environments that evolved in a regionally significant transgressive pattern. The formation is bounded by carbonate and shaly clastic strata of the Prairie du Chien Group below and is transitional to condensed sequence clastics and carbonates of the Glenwood Formation above. Sedimentologic and petrographic analysis of conventional core from 25 wells suggests that reservoir quality in the formation is strongly dependent on a complex diagenetic history, especially the nature and subsequent dissolution of intergranular carbonate in the sandstone. Petrographic evidence indicatesmore » that porosity in the formation formed by dissolution of precursor dolomite of various origins and, locally, the formation of pore-filling authigenic clay (chlorite-illite). Authigenic clay is the incongruent dissolution product of dolomite, detrital K-feldspar, and, possibly, muscovite and results in diminished reservoir quality where abundant in the St. Peter Sandstone. Authigenic clay is volumetrically more significant in the upper portions of the formation and is associated with higher concentrations of detrital K-feldspar. Depositional facies controlled the distribution and types of intergranular carbonate (now dolomite) and detrital K-feldspar in the St. Peter Sandstone and hence reservoir quality; both components were more significant in storm-shelf sandstone facies.« less

Inelastic compaction, dilation and hysteresis of sandstones under hydrostatic conditions

NASA Astrophysics Data System (ADS)

Shalev, Eyal; Lyakhovsky, Vladimir; Ougier-Simonin, Audrey; Hamiel, Yariv; Zhu, Wenlu

2014-05-01

Sandstones display non-linear and inelastic behaviour such as hysteresis when subjected to cyclic loading. We present three hydrostatic compaction experiments with multiple loading-unloading cycles on Berea and Darley Dale sandstones and explain their hysteretic behaviour using non-linear inelastic compaction and dilation. Each experiment included eight to nine loading-unloading cycles with increasing maximum pressure in each subsequent cycle. Different pressure-volumetric strain relations during loading and unloading were observed. During the first cycles, under relatively low pressures, not all of the volumetric strain is recovered at the end of each cycle whereas at the last cycles, under relatively high pressures, the strain is recovered and the pressure-volumetric strain hysteresis loops are closed. The observed pressure-volumetric strain relations are non-linear and the effective bulk modulus of the sandstones changes between cycles. Observations are modelled with two inelastic deformation processes: irreversible compaction caused by changes in grain packing and recoverable compaction associated with grain contact adhesion, frictional sliding on grains or frictional sliding on cracks. The irreversible compaction is suggested to reflect rearrangement of grains into a more compact mode as the maximum pressure increases. Our model describes the `inelastic compaction envelope' in which sandstone sample will follow during hydrostatic loading. Irreversible compaction occurs when pressure is greater than a threshold value defined by the `inelastic compaction envelope'.

Possible continuous-type (unconventional) gas accumulation in the Lower Silurian "Clinton" sands, Medina Group and Tuscarora Sandstone in the Appalachian Basin; a progress report of the 1995 project activities

USGS Publications Warehouse

Ryder, Robert T.; Aggen, Kerry L.; Hettinger, Robert D.; Law, Ben E.; Miller, John J.; Nuccio, Vito F.; Perry, William J.; Prensky, Stephen E.; Filipo, John J.; Wandrey, Craig J.

1996-01-01

INTRODUCTION: In the U.S. Geological Survey's (USGS) 1995 National Assessment of United States oil and gas resources (Gautier and others, 1995), the Appalachian basin was estimated to have, at a mean value, about 61 trillion cubic feet (TCF) of recoverable gas in sandstone and shale reservoirs of Paleozoic age. Approximately one-half of this gas resource is estimated to reside in a regionally extensive, continuous-type gas accumulation whose reservoirs consist of low-permeability sandstone of the Lower Silurian 'Clinton' sands and Medina Group (Gautier and others, 1995; Ryder, 1995). Recognizing the importance of this large regional gas accumulation for future energy considerations, the USGS initiated in January 1995 a multi-year study to evaluate the nature, distribution, and origin of natural gas in the 'Clinton' sands, Medina Group sandstones, and equivalent Tuscarora Sandstone. The project is part of a larger natural gas project, Continuous Gas Accumulations in Sandstones and Carbonates, coordinated in FY1995 by Ben E. Law and Jennie L. Ridgley, USGS, Denver. Approximately 2.6 man years were devoted to the Clinton/Medina project in FY1995. A continuous-type gas accumulation, referred to in the project, is a new term introduced by Schmoker (1995a) to identify those natural gas accumulations whose reservoirs are charged throughout with gas over a large area and whose entrapment does not involve a downdip gas-water contact. Gas in these accumulations is located downdip of the water column and, thus, is the reverse of conventional-type hydrocarbon accumulations. Commonly used industry terms that are more or less synonymous with continuous-type gas accumulations include basin- centered gas accumulation (Rose and others, 1984; Law and Spencer, 1993), tight (low-permeability) gas reservoir (Spencer, 1989; Law and others, 1989; Perry, 1994), and deep basin gas (Masters, 1979, 1984). The realization that undiscovered gas in Lower Silurian sandstone reservoirs of the

Diverse Grains in Mars Sandstone Target Big Arm

NASA Image and Video Library

2015-07-01

This view of a sandstone target called "Big Arm" covers an area about 1.3 inches (33 millimeters) wide in detail that shows differing shapes and colors of sand grains in the stone. Three separate images taken by the Mars Hand Lens Imager (MAHLI) camera on NASA's Curiosity Mars rover, at different focus settings, were combined into this focus-merge view. The Big Arm target on lower Mount Sharp is at a location near "Marias Pass" where a mudstone bedrock is in contact with overlying sandstone bedrock. MAHLI recorded the component images on May 29, 2015, during the 999th Martian day, or sol, of Curiosity's work on Mars. The rounded shape of some grains visible here suggests they traveled long distances before becoming part of the sediment that later hardened into sandstone. Other grains are more angular and may have originated closer to the rock's current location. Lighter and darker grains may have different compositions. MAHLI was built by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington. http://photojournal.jpl.nasa.gov/catalog/PIA19677

Persistent and widespread occurrence of bioactive quinone pigments during post-Paleozoic crinoid diversification

PubMed Central

Wolkenstein, Klaus

2015-01-01

Secondary metabolites often play an important role in the adaptation of organisms to their environment. However, little is known about the secondary metabolites of ancient organisms and their evolutionary history. Chemical analysis of exceptionally well-preserved colored fossil crinoids and modern crinoids from the deep sea suggests that bioactive polycyclic quinones related to hypericin were, and still are, globally widespread in post-Paleozoic crinoids. The discovery of hypericinoid pigments both in fossil and in present-day representatives of the order Isocrinida indicates that the pigments remained almost unchanged since the Mesozoic, also suggesting that the original color of hypericinoid-containing ancient crinoids may have been analogous to that of their modern relatives. The persistent and widespread occurrence, spatially as well as taxonomically, of hypericinoid pigments in various orders during the adaptive radiation of post-Paleozoic crinoids suggests a general functional importance of the pigments, contributing to the evolutionary success of the Crinoidea. PMID:25730856

Significance of nearshore trace-fossil assemblages of the cambro-ordovician deadwood formation and Aladdin Sandstone, South Dakota

USGS Publications Warehouse

Stanley, T.M.; Feldmann, R.M.

1998-01-01

The Cambro-Ordovician Deadwood Formation and Aladdin Sandstone represent intertidal and subtidal, nearshore deposystems that contain few well-preserved body fossils, but contain abundant trace fossils. The present study uses the much neglected trace-fossil fauna to describe the diverse paleoenvironments represented in the Deadwood-Aladdin deposystems, and to better understand the environmental conditions that controlled benthic life in the Early Paleozoic. The Deadwood-Aladdin ichnotaxa can be separated into three distinct assemblages based on the changing sedimentologic and hydrodynamic conditions that existed across the Cambro-Ordovician shelf. Trace-fossil assemblages and corresponding lithofacies characteristics indicate that the Deadwood-Aladdin deposystems formed within an intertidal-flat and subtidal-shelf environment. Based on the distribution and numbers of preserved ichnotaxa, the intertidal flat can be subdivided further into an ecologically stressful inner sand-flat environment, and a more normal marine outer sand-flat environment, both of which belong to a mixed, Skolithos-Cruziana softground ichnofacies. The inner sand flat is characterized by low diversity, low numbers, and a general lack of complexly constructed ichnotaxa. Trace fossils common to both assemblages tend to be smaller in the inner flat compared to the outer sand flat. Taphonomic effects, such as substrate type and sediment heterogeneity, also aid in differentiating between the inner and outer sand-flat assemblages. The subtidal shelf environment is categorized in the Cruziana Ichnofacies. Ichnological evidence of periodic tempestite deposition and hardground development within this subtidal regime is manifested by high diversity and low abundance of ichnogenera.

Devonian post-orogenic extension-related volcano-sedimentary rocks in the northern margin of the Tibetan Plateau, NW China: Implications for the Paleozoic tectonic transition in the North Qaidam Orogen

NASA Astrophysics Data System (ADS)

Qin, Yu; Feng, Qiao; Chen, Gang; Chen, Yan; Zou, Kaizhen; Liu, Qian; Jiao, Qianqian; Zhou, Dingwu; Pan, Lihui; Gao, Jindong

2018-05-01

The Maoniushan Formation in the northern part of the North Qaidam Orogen (NQO), NW China, contains key information on a Paleozoic change in tectonic setting of the NQO from compression to extension. Here, new zircon U-Pb, petrological, and sedimentological data for the lower molasse sequence of the Maoniushan Formation are used to constrain the timing of this tectonic transition. Detrital zircons yield U-Pb ages of 3.3-0.4 Ga with major populations at 0.53-0.4, 1.0-0.56, 2.5-1.0, and 3.3-2.5 Ga. The maximum depositional age of the Maoniushan Formation is well constrained by a youngest detrital zircon age of ∼409 Ma. Comparing these dates with geochronological data for the region indicates that Proterozoic-Paleozoic zircons were derived mainly from the NQO as well as the Oulongbuluk and Qaidam blocks, whereas Archean zircons were probably derived from the Oulongbuluk Block and the Tarim Craton. The ∼924, ∼463, and ∼439 Ma tectonothermal events recorded in this region indicate that the NQO was involved in the early Neoproterozoic assembly of Rodinia and early Paleozoic microcontinental convergence. A regional angular unconformity between Devonian and pre-Devonian strata within the NQO suggests a period of strong mountain building between the Oulongbuluk and Qaidam blocks during the Silurian, whereas an Early Devonian post-orogenic molasse, evidence of extensional collapse, and Middle to Late Devonian bimodal volcanic rocks and Carboniferous marine carbonate rocks clearly reflect long-lived tectonic extension. Based on these results and the regional geology, we suggest that the Devonian volcano-sedimentary rocks within the NQO were formed in a post-orogenic extensional setting similar to that of the East Kunlun Orogen, indicating that a major tectonic transition from compression to extension in these two orogens probably commenced in the Early Devonian.

Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

USGS Publications Warehouse

Anderson, P.B.; Chidsey, T.C.; Ryer, T.A.

1997-01-01

East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

Research progress and harnessing method of soil and water loss in Pisha Sandstone region

NASA Astrophysics Data System (ADS)

Xiao, P. Q.; Yang, C. X.; Jing, C. R.

2018-05-01

Pisha Sandstone region is the most vulnerable and the most dramatic area of soil erosion, severe soil erosion on the ecological bases of China’s energy security constitutes a serious challenge. Research progress of soil erosion in pisha Sandstone region was reviewed based on the need of soil and water ecological construction in Pisha Sandstone region and harnessing the yellow river including soil erosion mechanism, soil erosion dynamic monitoring and soil erosion simulation assessments. Meanwhile, the latest progress of soil and water conservation measures was analyzed, and the existing problems and future harnessing measures of soil and water loss were discussed. This study is to explore the comprehensive management method and provide scientific theory for constructing soil and water conservation project in Pisha Sandstone region.

Depositional facies, environments and sequence stratigraphic interpretation of the Middle Triassic-Lower Cretaceous (pre-Late Albian) succession in Arif El-Naga anticline, northeast Sinai, Egypt

NASA Astrophysics Data System (ADS)

El-Azabi, M. H.; El-Araby, A.

2005-01-01

The Middle Triassic-Lower Cretaceous (pre-Late Albian) succession of Arif El-Naga anticline comprises various distinctive facies and environments that are connected with eustatic relative sea-level changes, local/regional tectonism, variable sediment influx and base-level changes. It displays six unconformity-bounded depositional sequences. The Triassic deposits are divided into a lower clastic facies (early Middle Triassic sequence) and an upper carbonate unit (late Middle- and latest Middle/early Late Triassic sequences). The early Middle Triassic sequence consists of sandstone with shale/mudstone interbeds that formed under variable regimes, ranging from braided fluvial, lower shoreface to beach foreshore. The marine part of this sequence marks retrogradational and progradational parasequences of transgressive- and highstand systems tract deposits respectively. Deposition has taken place under warm semi-arid climate and a steady supply of clastics. The late Middle- and latest Middle/early Late Triassic sequences are carbonate facies developed on an extensive shallow marine shelf under dry-warm climate. The late Middle Triassic sequence includes retrogradational shallow subtidal oyster rudstone and progradational lower intertidal lime-mudstone parasequences that define the transgressive- and highstand systems tracts respectively. It terminates with upper intertidal oncolitic packstone with bored upper surface. The next latest Middle/early Late Triassic sequence is marked by lime-mudstone, packstone/grainstone and algal stromatolitic bindstone with minor shale/mudstone. These lower intertidal/shallow subtidal deposits of a transgressive-systems tract are followed upward by progradational highstand lower intertidal lime-mudstone deposits. The overlying Jurassic deposits encompass two different sequences. The Lower Jurassic sequence is made up of intercalating lower intertidal lime-mudstone and wave-dominated beach foreshore sandstone which formed during a short

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

NASA Astrophysics Data System (ADS)

Gorter, John D.

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

The provenance and chemical variation of sandstones associated with the Mid-continent Rift System, U.S.A.

USGS Publications Warehouse

Cullers, R.L.; Berendsen, P.

1998-01-01

Sandstones along the northern portion of the Precambrian Mid-continent Rift System (MRS) have been petrographically and chemically analyzed for major elements and a variety of trace elements, including the REE. After the initial extrusion of the abundant basalts along the MRS, dominantly volcaniclastic sandstones of the Oronto Group were deposited. These volcaniclastic sandstones are covered by quartzose and subarkosic sandstones of the Bayfield Group. Thus the sandstones of the Oronto Group were derived from previously extruded basalts, whereas, the sandstones of the Bayfield Group were derived from Precambrian granitic gneisses located on the rift flanks. The chemical variation of these sandstones closely reflects the changing detrital modes with time. The elemental composition of the sandstones confirms the source lithologies suggested by the mineralogy and clasts. The Oronto Group sandstones contain lower ratios of elements concentrated in silicic source rocks (La or Th) relative to elements concentrated in basic source rocks (Co, Cr, or Sc) than the Bayfield Group. Also, the average size of the negative Eu anomaly of the sandstones of the Oronto Group is significantly less (Eu/Eu* mean ?? standard deviation = 0.79 ?? 0.13) than that of the Bayfield Group (mean + standard deviation = 0.57 ?? 0.09), also suggesting a more basic source for the former than the latter. Mixing models of elemental ratios give added insight as to the evolution of the rift. These models suggest that the volcanistic sandstones of the lower portion of the Oronto Group are derived from about 80 to 90 percent basalt and 10 to 20 percent granitoids. The rest of the Oronto Group and the lower to middle portion of the Bayfield Group could have formed by mixing of about 30 to 60 percent basalt and 40 to 70 percent granitoids. The upper portion of the Bayfield Group is likely derived from 80 to 100 percent granitoids and zero to 20 percent basalt.

Reservoir characterization of Mesaverde (Campanian) bedload fluvial meanderbelt sandstones, northwestern Colorado

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

Jones, J.R. Jr.

1984-04-01

Reservoir characterization of Mesaverde meanderbelt sandstones is used to determined directional continuity of permeable zones. A 500-m (1600 ft) wide fluvial meanderbelt in the Mesaverde Group is exposed as laterally continuous 3-10-m (10-33-ft) high sandstone cliffs north of Rangely, Colorado. Forty-eight detailed measured sections through 3 point bar complexes oriented at right angles to the long axis of deposition and 1 complex oriented parallel to deposition were prepared. Sections were tied together by detailed sketches delineating and tracing major bounding surfaces such as scours and clay drapes. These complexes contain 3 to 8 multilateral sandstone packages separated by 5-20 cmmore » (2-8 in.) interbedded siltstone and shale beds. Component facies are point bars, crevasse splays, chute bars, and floodplain/overbank deposits. Two types of lateral accretion surfaces are recognized in the point bar facies. Gently dipping lateral accretions containing fining-upward sandstone packages. Large scale trough cross-bedding at the base grades upward into ripples and plane beds. Steeply dipping lateral accretion surfaces enclose beds characterized by climbing ripple cross laminations. Bounding surfaces draped by shale lags can seal vertically stacked point bars from reservoir communication. Scoured boundaries allow communication in some stacked point bars. Crevasse splays showing climbing ripples form tongues of very fine-grained sandstone which flank point bars. Chute channels commonly cut upper point bar surfaces at their downstream end. Chute facies are upward-fining with small scale troughs and common dewatering structures. Siltstones and shales underlie the point bar complexes and completely encase the meanderbelt system. Bounding surfaces at the base of the complexes are erosional and contain large shale rip-up clasts.« less

Detrital zircon U-Pb geochronology, Lu-Hf isotopes and REE geochemistry constrains on the provenance and tectonic setting of Indochina Block in the Paleozoic

NASA Astrophysics Data System (ADS)

Wang, Ce; Liang, Xinquan; Foster, David A.; Fu, Jiangang; Jiang, Ying; Dong, Chaoge; Zhou, Yun; Wen, Shunv; Van Quynh, Phan

2016-05-01

In situ U-Pb geochronology, Lu-Hf isotopes and REE geochemical analyses of detrital zircons from Cambrian-Devonian sandstones in the Truong Son Belt, central Vietnam, are used to provide the information of provenance and tectonic evolution of the Indochina Block. The combined detrital zircon age spectra of all of the samples ranges from 3699 Ma to 443 Ma and shows with dominant age peaks at ca. 445 Ma and 964 Ma, along with a number of age populations at 618-532 Ma, 1160-1076 Ma, 1454 Ma, 1728 Ma and 2516 Ma. The zircon age populations are similar to those from time equivalent sedimentary sequences in continental blocks disintegrated from the East Gondwana during the Phanerozoic. The younger zircon grains with age peaks at ca. 445 Ma were apparently derived from middle Ordovician-Silurian igneous and metamorphic rocks in Indochina. Zircons with ages older than about 600 Ma were derived from other Gondwana terrains or recycled from the Precambrian basement of the Indochina Block. Similarities in the detrital zircon U-Pb ages suggest that Paleozoic strata in the Indochina, Yangtze, Cathaysia and Tethyan Himalayas has similar provenance. This is consistent with other geological constrains indicating that the Indochina Block was located close to Tethyan Himalaya, northern margin of the India, and northwestern Australia in Gondwana.

Initiation and propagation of mixed mode fractures in granite and sandstone

NASA Astrophysics Data System (ADS)

Rück, Marc; Rahner, Roman; Sone, Hiroki; Dresen, Georg

2017-10-01

We investigate mixed mode fracture initiation and propagation in experimentally deformed granite and sandstone. We performed a series of asymmetric loading tests to induce fractures in cylindrical specimens at confining pressures up to 20 MPa. Loading was controlled using acoustic emission (AE) feedback control, which allows studying quasi-static fracture propagation for several hours. Location of acoustic emissions reveals distinct differences in spatial-temporal fracture evolution between granite and sandstone samples. Before reaching peak stress in experiments performed on granite, axial fractures initiate first at the edge of the indenter and then propagate through the entire sample. Secondary inclined fractures develop during softening of the sample. In sandstone, inclined shear fractures nucleate at peak stress and propagate through the specimen. AE source type analysis shows complex fracturing in both materials with pore collapse contributing significantly to fracture growth in sandstone samples. We compare the experimental results with numerical models to analyze stress distribution and energy release rate per unit crack surface area in the samples at different stages during fracture growth. We thereby show that for both rock types the energy release rate increases approximately linearly during fracture propagation. The study illuminates how different material properties modify fracture initiation direction under similar loading conditions.

Sedimentary and petrofacies analyses of the Amasiri Sandstone, southern Benue Trough, Nigeria: Implications for depositional environment and tectonic provenance

NASA Astrophysics Data System (ADS)

Okoro, A. U.; Igwe, E. O.; Nwajide, C. S.

2016-11-01

This study was undertaken to determine the depositional environment, provenance and tectonic setting for the Turonian Amasiri Sandstone, southern Benue Trough, Nigeria, using lithofacies analysis and re-appraisal of petrography of the sandstones. Local stratigraphy and field relationships show a thick succession of shales alternating with elongate/parallel sandstone ridges extending eastwards from Akpoha to Amasiri through Itigidi and Ugep to Apiapum areas. Lithofacies analysis reveals 9 lithofacies suggestive of storm (mass flow) and tidal shelf processes. These include dark grey to black laminated shale/silty mudstones, bioturbated mudstones, coquinoid limestones, very fine-grained bioturbated sandstones with shell hash/debris in places and limestone rip-up clasts, massive and chaotic sandy conglomerate with rip - up clasts, fine to medium-grained, parallel laminated sandstone, hummocky cross-stratified, massive, medium to coarse-grained sandstones, medium to very coarse-grained, planar cross-bedded sandstone, with clay-draped foresets and Ophiomorpha burrows, and coarse-grained trough cross-bedded sandstone. Petrofacies analysis identifies the sandstones as feldspathic and arkosic arenites. Ternary plot of framework mineralogy indicates derivation from an uplifted continental block related to the nearby Oban Massif and Cameroon Basement Complex.

Testing the limits of Paleozoic chronostratigraphic correlation via high-resolution (13Ccarb) biochemostratigraphy across the Llandovery–Wenlock (Silurian) boundary: Is a unified Phanerozoic time scale achievable?

USGS Publications Warehouse

Cramer, Bradley D.; Loydell, David K.; Samtleben, Christian; Munnecke, Axel; Kaljo, Dimitri; Mannik, Peep; Martma, Tonu; Jeppsson, Lennart; Kleffner, Mark A.; Barrick, James E.; Johnson, Craig A.; Emsbo, Poul; Joachimski, Michael M.; Bickert, Torsten; Saltzman, Matthew R.

2010-01-01

The resolution and fidelity of global chronostratigraphic correlation are direct functions of the time period under consideration. By virtue of deep-ocean cores and astrochronology, the Cenozoic and Mesozoic time scales carry error bars of a few thousand years (k.y.) to a few hundred k.y. In contrast, most of the Paleozoic time scale carries error bars of plus or minus a few million years (m.y.), and chronostratigraphic control better than ??1 m.y. is considered "high resolution." The general lack of Paleozoic abyssal sediments and paucity of orbitally tuned Paleozoic data series combined with the relative incompleteness of the Paleozoic stratigraphic record have proven historically to be such an obstacle to intercontinental chronostratigraphic correlation that resolving the Paleozoic time scale to the level achieved during the Mesozoic and Cenozoic was viewed as impractical, impossible, or both. Here, we utilize integrated graptolite, conodont, and carbonate carbon isotope (??13Ccarb) data from three paleocontinents (Baltica, Avalonia, and Laurentia) to demonstrate chronostratigraphic control for upper Llando very through middle Wenlock (Telychian-Sheinwoodian, ~436-426 Ma) strata with a resolution of a few hundred k.y. The interval surrounding the base of the Wenlock Series can now be correlated globally with precision approaching 100 k.y., but some intervals (e.g., uppermost Telychian and upper Shein-woodian) are either yet to be studied in sufficient detail or do not show sufficient biologic speciation and/or extinction or carbon isotopic features to delineate such small time slices. Although producing such resolution during the Paleozoic presents an array of challenges unique to the era, we have begun to demonstrate that erecting a Paleozoic time scale comparable to that of younger eras is achievable. ?? 2010 Geological Society of America.

Late proterozoic and paleozoic tides, retreat of the moon, and rotation of the earth

USGS Publications Warehouse

Sonett, C.P.; Kvale, E.P.; Zakharian, A.; Chan, M.A.; Demko, T.M.

1996-01-01

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is d??/dt k2 sin(2??) (where ?? is the Earth-moon radius vector, k2 is the tidal Love number, and ?? is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was -18 hours.

Shell microstructure of the late Carboniferous rostroconch mollusc Apotocardium lanterna (Branson, 1965)

USGS Publications Warehouse

Rogalla, N.S.; Carter, J.G.; Pojeta, J.

2003-01-01

The Late Carboniferous bransoniid conocardioidean Apotocardium lanterna (Branson, 1965) had an entirely aragonitic shell with a finely prismatic outer shell layer, a predominantly crossed lamellar to complex crossed lamellar middle shell layer, and an "inner" shell layer of finely textured porcelaneous and/or matted structure. This "inner" layer is probably homologous with the inner part of the middle shell layer and the inner layer sensu stricto of bivalved molluscs. Shell morphological and microstructural convergences between conocardioids and living heart cockles suggest that at least some conocardioids may have farmed algal endosymbionts in their posterior mantle margins. This symbiosis may have helped conocardioids compete with the biomechanically more efficient bivalves during the latter part of the Paleozoic.

Depositional Environments of Late Danian Plant Localities: Chubut Provice, Patagonia, Argentina

NASA Astrophysics Data System (ADS)

Comer, E.; Slingerland, R. L.; Wilf, P.

2010-12-01

Diverse, well-preserved macroflora are observed within Cretaceous and Paleocene sediments of Chubut Province, Patagonia, Argentina. These macroflora are the most well preserved early Paleocene flora from Gondwana and add new insight into the diversity and environments of that epoch. Two major sites of fossil preservation, Palacio de los Loros and Parque Provincial Ormachea, sit near the top of the Late Danian (65.5-61.7 Ma) Salamanca Formation. Understanding the depositional history of the Salamanca is important in characterizing paleoenvironments in which these flora lived and relating these Patagonian macroflora to concurrent Paleocene flora within the Gondwanan supercontinent. During a two week field season, twenty stratigraphic sections were measured along the outcrop belt at Palacio de los Loros and Ormachea Park as well as two minor sites; Las Flores, and Rancho Grande. Photo mosaics, laser ranger data, and stratigraphic columns were merged with elevated geologic maps and imported into Fledermaus to generate a 3-D visualization of facies relationships. Rock samples were also collected and will be thin sectioned and analyzed for petrography and grain size. The Salamanca Fm. consists of 7 facies, listed here in stratigraphically ascending order: 1)Transgressive sands, 2)Wispy-bedded claystone, 3)Banco Verde, 4)White Cross bedded sandstone, 5)Accretion set siltstone, 6)Transitional silty claystone and 7)Banco Negro. Based on these facies, the Salamanca Fm. is interpreted as a marine-shelf to brackish, tide-dominated, estuarine deposit. The base of the Salamanca Fm. rests on an unconformity representing a marine flooding surface and lower sections of the Salamanca, facies 1 and 2, contain abundant glauconite and fossils indicative of a marine shelf environment. These facies give way upwards to bi-directional trough cross bedded sandstones interspersed with flaser bedded sandy siltstones (facies 3 and 4) indicating a less marine estuary with strong flow regimes

The Myszkow porphyry copper-molybdenum deposit, Poland

USGS Publications Warehouse

Chaffee, M.A.; Eppinger, R.G.; Lason, K.; Slosarz, J.; Podemski, M.

1994-01-01

The porphyry copper-molybdenum deposit at Myszkow, south-central Poland, lies in the Cracow-Silesian orogenic belt, in the vicinity of a Paleozoic boundary between two tectonic plates. The deposit is hosted in a complex that includes early Paleozoic metasedimentary rocks intruded in the late Paleozoic by a predominantly granodioritic pluton. This deposit exhibits many features that are typical of porphyry copper deposits associated with calc-alkaline intrusive rocks, including ore- and alteration-mineral suites, zoning of ore and alteration minerals, fluid-inclusion chemistry, tectonic setting, and structural style of veining. Unusual features of the Myszkow deposit include high concentrations of tungsten and the late Paleozoic (Variscan) age. -Authors

Red Fork and lower Skinner sandstones in northwest Tecumseh field, Pottawatomie County, Oklahoma

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

Dale, T.B.

1987-08-01

The Northwest Tecumseh field, discovered in 1978, produces from the Pennsylvanian Skinner and Red Fork sandstones at 4800 ft. The 50 wells had produced 6.4 million bbl of oil and 20.8 bcf of gas through 1986. The field is 4.5 mi long, 3/4 mi wide, and the vertical section contains up to 132 ft of sandstone with greater than 10% porosity. These stacked, interconnected north-northeast-trending, channel-fill sandstones are part of a much larger fluvial/distributary system. These channels flowed to the north and cut down into underlying, fossiliferous, carbonate-bearing marine shale. A pre-Pennsylvanian structural low, trending north-northeast, existed in the southernmore » half of the field and created a predisposition for the channel trend which continued through Red Fork and Skinner deposition. The north-northeast-trending sandstone complex, parallel with present-day regional structural strike, provides the excellent configuration for this efficient stratigraphic trap. The northern end of the field is marked by bifurcation of the channel complex and by the crosscutting of a younger clay-filled channel. Despite the lenticularity of the sandstone sequence, there appears to be a uniform gas-oil contact and minor southwestward tilt of the oil-water contact in the south part of the pool. The primary reservoir energy is provided by a dissolved gas drive, with some assistance from the 60-ft gas cap. The vertical oil column is 80 ft. These reservoir sandstones are fine-grained quartzarenites, and the dissolution of ferrodolomite has increased porosities up to 21%. Kaolinite is the predominant clay mineral and has a tendency to migrate and reduce permeability during production.« less

Depositional systems and diagenesis of Travis Peak tight gas sandstone reservoirs, Sabine Uplift Area, Texas

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

Fracasso, M.A.; Dutton, S.P.; Finley, R.J.

The Travis Peak formation (lower Cretaceous) in the eastern East Texas basin is a fluvio-deltaic depositional system divided into large-scale facies packages: a middle sandstone-rich fluvial and delta-plain sequence that is gradationally overlain and underlain by a marine-influenced delta-fringe zone with a higher mudstone content. Domes and structural terraces on the west flank of the Sabine Uplift influenced deposition of Travis Peak sediments, and most Travis Peak gas production in this area is from thin sandstones (<25 ft(<7.6 m) thick) in the upper delta-fringe facies. The trapping mechanism is stratigraphic pinch-out of sandstones or porosity zones within sandstone, or both,more » on the flanks of structures. Detailed mapping of producing sandstone sequences in the uppermost upper delta-fringe on the western flank of the Bethany structure has delineated fluvial channelways, distributary or tidal channels, and barrier of distributary-mouth bars. Most Travis Peak gas production in the Bethany West area is from the bases of channel sandstones in a marine-influenced facies belt. Travis Peak sandstones in the eastern East Texas basin have undergone a complex series of diagenetic modifications. Precipitation of authigenic quartz, ankerite, dolomite, illite, and chlorite and the introduction of reservoir bitumen were the most important causes of occlusion of primary porosity and reduction of permeability. Permeability decreases with depth in the Travis Peak, which suggests that the diagenetic processes that caused extensive cementation and resultant low permeability throughout most of the formation operated less completely on sediments deposited near the top of the succession.« less

Characterization of Navajo Sandstone concretions: Mars comparison and criteria for distinguishing diagenetic origins

NASA Astrophysics Data System (ADS)

Potter, Sally L.; Chan, Marjorie A.; Petersen, Erich U.; Dyar, M. Darby; Sklute, Elizabeth

2011-01-01

The eolian Jurassic Navajo Sandstone spheroidal hydrous ferric oxide (HFO) concretions are divided into two size classes: macro-concretions of > 5 mm diameter and micro-concretions of < 5 mm diameter. Three internal structural end-members of macro-concretions are described as rind, layered, and solid. Two end-members of micro-concretions are rind and solid. Chemical and mineralogical gradients (μm- to mm-scale) are identified with QEMSCAN (Quantitative Elemental Mineralogy using a SCANning electron microscope) and visible to near infrared (VNIR) reflectance spectroscopy. Three HFO phases are identified using VNIR reflectance spectroscopy. An amorphous HFO phase is typically located in the rinds. Goethite is present along interior edges of rinds and throughout the interiors of layered and solid concretions. Hematite is present in the centers of rind concretions. A synthesis of petrographic, mineralogical and chemical analyses suggests that concretions grow pervasively (as opposed to radially expanding). Our model proposes that concretions precipitate initially as an amorphous HFO that sets the radius and retains some original porosity. Subsequent precipitation fills remaining pore space with younger mineral phases. Inward digitate cement crystal growth corroborates concretion growth from a set radius toward the centers. Internal structure is modified during late stage precipitation that diffuses reactants through semi-permeable rinds and overprints the interiors with younger cements. Physical characterization of textures and minerals provides diagnostic criteria for understanding how similar concretions ("blueberries") form in Meridiani Planum, Mars. The analogous Navajo Sandstone concretions show similar characteristics of in situ self-organized spacing, spheroidal geometries, internal structures, conjoined forms, and precursor HFO phases that dehydrate to goethite or hematite. These characteristics indicate a common origin via groundwater diagenesis.

Tectonic isolation from regional sediment sourcing of the Paradox Basin

NASA Astrophysics Data System (ADS)

Smith, T. M.; Saylor, J.; Sundell, K. E.; Lapen, T. J.

2017-12-01

The Appalachian and Ouachita-Marathon mountain ranges were created by a series of tectonic collisions that occurred through the middle and late Paleozoic along North America's eastern and southern margins, respectively. Previous work employing detrital zircon U-Pb geochronology has demonstrated that fluvial and eolian systems transported Appalachian-derived sediment across the continent to North America's Paleozoic western margin. However, contemporaneous intraplate deformation of the Ancestral Rocky Mountains (ARM) compartmentalized much of the North American western interior and mid-continent. We employ lithofacies characterization, stratigraphic thickness, paleocurrent data, sandstone petrography, and detrital zircon U-Pb geochronology to evaluate source-sink relationships of the Paradox Basin, which is one of the most prominent ARM basins. Evaluation of provenance is conducted through quantitative comparison of detrital zircon U-Pb distributions from basin samples and potential sources via detrital zircon mixture modeling, and is augmented with sandstone petrography. Mixing model results provide a measure of individual source contributions to basin stratigraphy, and are combined with outcrop and subsurface data (e.g., stratigraphic thickness and facies distributions) to create tectonic isolation maps. These maps elucidate drainage networks and the degree to which local versus regional sources influence sediment character within a single basin, or multiple depocenters. Results show that despite the cross-continental ubiquity of Appalachian-derived sediment, fluvial and deltaic systems throughout much of the Paradox Basin do not record their influence. Instead, sediment sourcing from the Uncompahgre Uplift, which has been interpreted to drive tectonic subsidence and formation of the Paradox Basin, completely dominated its sedimentary record. Further, the strong degree of tectonic isolation experienced by the Paradox Basin appears to be an emerging, yet common

The interplay of fractures and sedimentary architecture: Natural gas from reservoirs in the Molina sandstones, Piceance Basin, Colorado

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

Lorenz, J.C.

1997-03-01

The Molina Member of the Wasatch Formation produces natural gas from several fields along the Colorado River in the Piceance Basin, northwestern Colorado. The Molina Member is a distinctive sandstone that was deposited in a unique fluvial environment of shallow-water floods. This is recorded by the dominance of plane-parallel bedding in many of the sandstones. The Molina sandstones crop out on the western edge of the basin, and have been projected into the subsurface and across the basin to correlate with thinner sandy units of the Wasatch Formation at the eastern side of the basin. Detailed study, however, has shownmore » that the sedimentary characteristics of the type-section Molina sandstones are incompatible with a model in which the eastern sandstones are its distal facies equivalent. Rather, the eastern sandstones represent separate and unrelated sedimentary systems that prograded into the basin from nearby source-area highlands. Therefore, only the subsurface {open_quotes}Molina{close_quotes} reservoirs that are in close proximity to the western edge of the basin are continuous with the type-section sandstones. Reservoirs in the Grand Valley and Rulison gas fields were deposited in separate fluvial systems. These sandstones contain more typical fluvial sedimentary structures such as crossbeds and lateral accretion surfaces. Natural fractures play an important role in enhancing the conductivity and permeability of the Molina and related sandstones of the Wasatch Formation.« less

Experimental deformation in sandstone, carbonates and quartz aggregate

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

Cheung, Cecilia See Nga

2015-05-01

The first part of my thesis is mainly focused on the effect of grain size distribution on compaction localization in porous sandstone. To identify the microstructural parameters that influence compaction band formation, I conducted a systematic study of mechanical deformation, failure mode and microstructural evolution in Bleurswiller and Boise sandstones, of similar porosity (~25%) and mineralogy but different sorting. Discrete compaction bands were observed to develop over a wide range of pressure in the Bleurswiller sandstone that has a relatively uniform grain size distribution. In contrast, compaction localization was not observed in the poorly sorted Boise sandstone. My results demonstratemore » that grain size distribution exerts important influence on compaction band development, in agreement with recently published data from Valley of Fire and Buckskin Gulch, as well as numerical studies. The second part aimed to improve current knowledge on inelastic behavior, failure mode and brittle-ductile transition in another sedimentary rock, porous carbonates. A micritic Tavel (porosity of ~13%) and an allochemical Indiana (~18%) limestones were deformed under compaction in wet and dry conditions. At lower confining pressures, shear localization occurred in brittle faulting regime. Through transitional regime, the deformation switched to cataclastic flow regime at higher confining pressure. Specifically in the cataclastic regime, the (dry and wet) Tavel and dry Indiana failed by distributed cataclastic flow, while in contrast, wet Indiana failed as compaction localization. My results demonstrate that different failure modes and mechanical behaviors under different deformation regimes and water saturation are fundamental prior to any geophysical application in porous carbonates. The third part aimed to focus on investigating compaction on quartz aggregate starting at low (MPa) using X-ray diffraction. We report the diffraction peak evolution of quartz with

Hydropressure tongues within regionally geopressured lower Tuscaloosa sandstone, Tuscaloosa trend, Louisiana

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

McCulloh, R.P.; Purcell, M.D.

1983-01-01

A regional study of the Tuscaloosa Formation in Louisiana, undertaken to assess geopressured-geothermal potential, revealed lobate, downdip extensions of the hydropressured zone in lower Tuscaloosa massive sandstone facies below the regional top of geopressure. Normal pressure zones within geopressured section were identified by drilling mud weights less than 13 pounds per gallon on electric logs of massive lower Tuscaloosa sandstone, and cross sections demonstrated updip continuity of these zones with the regional hydropressured zone. These hydropressure tongues are permitted by the anomalously high permeabilities reportd from the deep Tuscaloosa trend which have been attributed to both primary and secondary porosity.more » The hydropressure tongues correspond with lobes of thick net sandstone, principally in Pointe Coupee, East Feliciana, East Baton Rouge, and Livingston Parishes in the central Tuscaloosa trend. Limited control suggests at least one hydropressure tongue in the Chandeleur Sound area to the east.« less

Desert and groundwater dynamics of the Jurassic Navajo Sandstone, southeast Utah

NASA Astrophysics Data System (ADS)

Chan, M. A.; Hasiotis, S. T.; Parrish, J. T.

2017-12-01

The Jurassic Navajo Sandstone of southeastern Utah is a rich archive of a desert complex with an active groundwater system, influenced by climate changes and recharge from the Uncompahgre Uplift of the Ancestral Rocky Mountains. This eastern erg margin was dominated by dune deposits of large (>10 m thick) and small (m-scale) crossbedded sandstone sets. Within these porous deposits, common soft sediment deformation is expressed as contorted and upturned bedding, fluid escape structures, concentrations of clastic pipes with ring faults, and thick intervals of massive sandstone embedded in crossbedded sandstone. Collectively, these deformation features reflect changes and/or overpressure in the groundwater system. Interdune deposits record laterally variable bounding surfaces, resulting from the change in position of and proximity to the water table. Interdune modification by pedogenesis from burrows, roots, and trees suggest stable periods of moisture and water supply, as well as periodic drying expressed as polygonal cracked mud- to sand-cracked layers. Freshwater bedded and platy limestone beds represent lakes of decameter to kilometer extent, common in the upper part of the formation. Some carbonate springs that fed the lakes are preserved as limestone buildups (tufa mounds) with microbial structures. Extradunal deposits of rivers to small ephemeral streams show channelized and lenticular, subhorizontal, cm- to m-scale sandstone bodies with basal scours and rip-up clasts. Proxy records of the active hydrology imply a changing landscape at the Navajo desert's edge, punctuated by periods of significant rainfall, runoff, rivers, lakes, and springs, fed by high water table conditions to sustain periods of flourishing communities of plants, arthropods, reptiles, mammals, and dinosaurs. Strong ground motion perturbations periodically disrupted porous, water-saturated sands with possible surface eruptions, adding to the dynamic activity of the desert regime.

Reworked crustal of early Paleozoic WuYi Orogen revealed by receiver function data

NASA Astrophysics Data System (ADS)

Wei, Y.; Duan, Y.; Tian, X.; Zhao, Y.

2017-12-01

Intraplate orogenic belt, which occurs at the rigid and undeformable plate interiors, is a distinct new type of orogen rather than an interplate or plate marginal orogenic belt, whose deformation occurs exclusively at plate margins. Therefore, intraplate orogenic belts are the most obvious exception to the plate-tectonic paradigm, they are uncommon in Earth's history. The early Paleozoic Wuyi orogen in South China is one of the few examples of intraplate orogen, and is a key to understanding the process of intraplate orogenesis and global early Paleozoic geodynamics. In this study, we select teleseismic records from 45 mobile linear seismic stations deployed in Wuyi Mountain and 58 permanent stations setting in Jiangxi and Fujian provinces, from January 2011 to December 2012, and calculate the crustal thickness and average crustal Vp/Vs ratio using the H-κ stacking method. The main results include the following: 1) the crustal average Poission's ratio shows an increase tendency from land to sea, the interior of Wuyi orogen belt with an low ration less than 0.23, and the coastline with high ration which is up to 0.28, which indicate a very heterogeneous crustal structure and composition in Wuyi orogen and coast belt. 2) the crustal thickness ranges 28-34 km and shows a tendency of thinning from inland to coast in the region of SE China margin, which maight mean the eastern Eurasia lithospheric is extension and thinning induced by the subducted paleo-Pacific slab. To conclusion, we assume that Wuyi orogen experienced upper crustal thickening, lower crust and lithosphere delamination during the early Paleozoic orogeny, and lithosphere extension in Mesozoic. This research is founded by the Natural Science Foundation of China (41174052 and 41604048).

Ordovician conodonts and stratigraphy of the ST. Peter sandstone and glen wood shale, central United States

USGS Publications Warehouse

Witzke, B.J.; Metzger, R.A.

2005-01-01

The age of the St. Peter Sandstone in the central and northern Midcontinent has long been considered equivocal because of the general absence of biostratigraphically useful fossils. Conodonts recovered from the St. Peter Sandstone in Iowa, Minnesota, Nebraska, and Kansas for this study help place some age constraints on this renowned formation in its northern and western extent. Faunas from the lower St. Peter include Phragmodus flexuosus, Cahabagnathus sp., and Leptochirognathus sp., and a late Whiterockian (Chazyan) correlation is indicated. Juvenile or immature elements of P. flexuosus from these collections show morphologies trending toward P. cognitus and P. inflexus, and paedomorphic derivation of these latter species is proposed. Diverse assemblages of hyaline forms also occur in the St. Peter strata (Erismodus spp., Erraticodon sp., Curtognathus sp., Coleodus sp., Archeognathus sp., Stereoconus sp., others) along with various albid elements (Plectodina sp., Eoplacognathus sp., others). The overlying Glenwood Shale contains abundant conodonts dominated by Phragmodus cognitus, Erismodus sp., and Chirognathus duodactylus, and the fauna is interpreted as an early Mohawkian (Blackriveran) association. Certain thin shale units in the St. Peter-Glenwood succession represent condensed intervals, in part reflected by their exceptionally high conodont abundances. Some organic-rich phosphatic shale units in the lower St. Peter of western Iowa have produced equivalent yields of tens of thousands of conodonts per kilogram, and many Glenwood Shale samples yield thousands of conodonts per kilogram. Previous depositional models have proposed that the St. Peter is primarily a succession of littoral and nearshore facies forming a broadly diachronous transgressive sheet sand. However, broad-scale diachroneity cannot be demonstrated with available biostratigraphic control. The recognition of condensed marine shale units, phosphorites, ironstones, and pyritic hardgrounds in the

Nodules of Cemented Sand Grains Within Martian Sandstone

NASA Image and Video Library

2016-03-11

This view from NASA Curiosity shows nodules exposed in sandstone that is part of the Stimson geological unit on Mount Sharp, Mars. The nodules can be seen to consist of grains of sand cemented together.

Involvement of old crustal materials during formation of the Sakhalin Island (Russian Far East) and its paleogeographic implication: Constraints from detrital zircon ages of modern river sand and Miocene sandstone

NASA Astrophysics Data System (ADS)

Zhao, Pan; Li, Jia-jin; Alexandrov, Igor; Ivin, Vitaly; Jahn, Bor-ming

2017-09-01

In order to decipher crustal nature of the Sakhalin Island in Russian Far East, we carried out detrital zircon U-Pb age analyses on Miocene sandstone and river sand from the longest river (Poronay River) of the Sakhalin Island. The detrital zircon data from two river sand samples display similar age distribution patterns with a dominant Mesozoic age group, subordinate age peaks at 1.8 Ga and 2.5 Ga, and a few Paleozoic and Neoproterozoic grains. The Miocene sandstone shows age peaks at 22, 84, 260 and 497 Ma, respectively, and a few Paleo-proterozoic grains. These age groups indicate that abundant old crustal materials have been involved in the crustal formation of the Sakhalin Island. Detrital zircon result reveals two episodes of post-accretion magmatism from the Sakhalin Island in ages of 37 Ma and 22-21 Ma. They can be correlated with coeval post-accretion magmatic events in the Hokkaido Island, supporting the geological correlation between the Sakhalin Island and the Hokkaido Island. Comparison of detrital zircon dating result from the Sakhalin Island with those from surrounding blocks and cratons in eastern Asia allows us to propose two possible sources in eastern Asia: the Bureya-Jiamusi-Khanka block with the Sikhote-Alin orogenic belt to its west and the South China Craton. The detrital zircon result indicates that the formation of the Sakhalin Island should be close to the East Asia continent, rather than as an independent intro-oceanic island arc within the Pacific Ocean. Similar to formation of the Japanese islands, the South China Craton may have played an important role during formation of the Sakhalin Island.

The fauna of the Batesville sandstone of northern Arkansas

USGS Publications Warehouse

Girty, George H.

1915-01-01

The beds in northern Arkansas that lie between the Boone limestone (commonly regarded as representing the Burlington and Keokuk epochs) and the Pennsylvanian have been divided into several formations, named, in ascending order, Moorefield shale, Batesville sandstone, Fayetteville shale, and Pitkin limestone. These formations presumably are equivalent to those that hold a corresponding position in the typical Mississippian section of Iowa, Missouri, and Illinois, but the faunas which they have furnished show noteworthy differences from the typical faunas. It has therefore seemed desirable to investigate these faunas, especially as the facies which they present is found also in the faunas of several of the Southern States, such as Oklahoma, Mississippi, and Alabama. With this object in view, I published in 1911 a report on the fossils of the Moorefield shale. The fauna next to be considered in a systematic pursuance of such a plan as I have mentioned is that of the Batesville sandstone, but the fauna of the Batesville sandstone, as is well known, has already been described in a treatise by Prof. Stuart Weller. At first I considered the possibility of pretermitting the Batesville fauna and of substituting Prof. Weller's report for my own in a series of little monographs that are under contemplation. It soon became evident, however, that this would not be satisfactory because, whether by reason of having collections from a number of new localities or by reason of having more extensive collections from old ones, I found that the material at my command considerably increased the number of types known from the Batesville sandstone, among them being a few which were undescribed. In fact, while Prof. Weller's paper discusses only 30 species (aside from a few Bryozoan types not even generically distinguished) the present paper discusses 128 species. On this account it seemed to me essential to redescribe the fauna.

Biologically-initiated rock crust on sandstone: Mechanical and hydraulic properties and resistance to erosion

NASA Astrophysics Data System (ADS)

Slavík, Martin; Bruthans, Jiří; Filippi, Michal; Schweigstillová, Jana; Falteisek, Lukáš; Řihošek, Jaroslav

2017-02-01

Biocolonization on sandstone surfaces is known to play an important role in rock disintegration, yet it sometimes also aids in the protection of the underlying materials from rapid erosion. There have been few studies comparing the mechanical and/or hydraulic properties of the BIRC (Biologically-Initiated Rock Crust) with its subsurface. As a result, the overall effects of the BIRC are not yet well understood. The objective of the present study was to briefly characterize the BIRC from both the mineralogical and biological points of view, and especially to quantify the effect of the BIRC upon the mechanical and hydraulic properties of friable sandstone. The mineralogical investigation of a well-developed BIRC showed that its surface is enriched in kaolinite and clay- to silt-sized quartz particles. Total organic carbon increases with the age of the BIRC. Based on DNA sequencing and microscopy, the BIRC is formed by various fungi, including components of lichens and green algae. Using the method of drilling resistance, by measuring tensile strength, and based on water jet testing, it was determined that a BIRC is up to 12 times less erodible and has 3-35 times higher tensile strength than the subsurface friable sandstone. Saturated hydraulic conductivity of the studied BIRC is 15-300 times lower than the subsurface, and was measured to also decrease in capillary water absorption (2-33 times). Water-vapor diffusion is not significantly influenced by the presence of the BIRC. The BIRC thus forms a hardened surface which protects the underlying material from rain and flowing water erosion, and considerably modifies the sandstone's hydraulic properties. Exposing the material to calcination (550 °C), and experiments with the enzyme zymolyase indicated that a major contribution to the surface hardening is provided by organic matter. In firmer sandstones, the BIRC may still considerably decrease the rate of weathering, as it is capable of providing cohesion to strongly

Early Mesozoic paleogeography and tectonic evolution of the western United States: Insights from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern Oregon

USGS Publications Warehouse

LaMaskin, Todd A.; Vervoort, J.D.; Dorsey, R.J.; Wright, J.E.

2011-01-01

This study assesses early Mesozoic provenance linkages and paleogeographic-tectonic models for the western United States based on new petrographic and detrital zircon data from Triassic and Jurassic sandstones of the "Izee" and Olds Ferry terranes of the Blue Mountains Province, northeastern Oregon. Triassic sediments were likely derived from the Baker terrane offshore accretionary subduction complex and are dominated by Late Archean (ca. 2.7-2.5 Ga), Late Paleoproterozoic (ca. 2.2-1.6 Ga), and Paleozoic (ca. 380-255 Ma) detrital zircon grains. These detrital ages suggest that portions of the Baker terrane have a genetic affinity with other Cordilleran accretionary subduction complexes of the western United States, including those in the Northern Sierra and Eastern Klamath terranes. The abundance of Precambrian grains in detritus derived from an offshore complex highlights the importance of sediment reworking. Jurassic sediments are dominated by Mesozoic detrital ages (ca. 230-160 Ma), contain significant amounts of Paleozoic (ca. 290, 380-350, 480-415 Ma), Neoproterozoic (ca. 675-575 Ma), and Mesoproterozoic grains (ca. 1.4-1.0 Ga), and have lesser quantities of Late Paleoproterozoic grains (ca. 2.1-1.7 Ga). Detrital zircon ages in Jurassic sediments closely resemble well-documented age distributions in transcontinental sands of Ouachita-Appalachian provenance that were transported across the southwestern United States and modified by input from cratonal, miogeoclinal, and Cordilleran-arc sources during Triassic and Jurassic time. Jurassic sediments likely were derived from the Cordilleran arc and an orogenic highland in Nevada that yielded recycled sand from uplifted Triassic backarc basin deposits. Our data suggest that numerous Jurassic Cordilleran basins formed close to the Cordilleran margin and support a model for moderate post-Jurassic translation (~400 km) of the Blue Mountains Province. ?? 2011 Geological Society of America.

Sandstone: secular trends in lithology in southwestern montana.

PubMed

McLane, M

1972-11-03

Long-term secular trends in the composition and texture of sandstones in southwestern Montana reflect changing provenance and depositional environment, which in turn reflect changing tectonic patterns in the Cordilleran mobile belt just to the west.

Geohydrology of the Navajo sandstone in western Kane, southwestern Garfield, and southeastern Iron counties, Utah

USGS Publications Warehouse

Freethey, G.W.

1988-01-01

The upper Navajo and Lamb Point aquifers in the Navajo Sandstone are the principal source of water for the city of Kanab, irrigation, stock, and for rural homes in the study area. Well logs and outcrop descriptions indicate the Navajo Sandstone consists of the Lamb Point Tongue and an unnamed upper member that are separated by the Tenney Canyon Tongue of the Kayenta Formation. The main Kayenta Formation underlies the Lamb Point Tongue. The Lamb Point Tongue and the upper member of the Navajo Sandstone are saturated and hydraulically connected through the Tenney Canyon Tongue. Available data indicate that precipitation percolates to the groundwater reservoir where the Navajo Sandstone crops out. Estimates of the rate of recharge at the outcrop range from 0.1 to as much as 2.8 in/yr. Water level data indicate that water moves from the upper member of the Navajo Sandstone, through the Tenney Canyon Tongue, and into the Lamb Point Tongue. Lateral flow is generally from the outcrop areas toward the incised canyons formed by tributaries of Kanab Creek and Johnson Wash. Direction and rate of groundwater movement and the location and character of the natural hydrologic boundaries in the northern part of the area where the Navajo Sandstone is buried cannot be determined conclusively without additional water level data. (Author 's abstract)

Deformation of Reservoir Sandstones by Elastic versus Inelastic Deformation Mechanisms

NASA Astrophysics Data System (ADS)

Pijnenburg, R.; Verberne, B. A.; Hangx, S.; Spiers, C. J.

2016-12-01

Hydrocarbon or groundwater production from sandstone reservoirs can result in surface subsidence and induced seismicity. Subsidence results from combined elastic and inelastic compaction of the reservoir due to a change in the effective stress state upon fluid extraction. The magnitude of elastic compaction can be accurately described using poroelasticity theory. However inelastic or time-dependent compaction is poorly constrained. Specifically, the underlying microphysical processes controlling sandstone compaction remain poorly understood. We use sandstones recovered by the field operator (NAM) from the Slochteren gas reservoir (Groningen, NE Netherlands) to study the importance of elastic versus inelastic deformation processes upon simulated pore pressure depletion. We conducted conventional triaxial tests under true in-situ conditions of pressure and temperature. To investigate the effect of applied differential stress (σ1 - σ3 = 0 - 50 MPa) and initial sample porosity (φi = 12 - 24%) on instantaneous and time-dependent inelastic deformation, we imposed multiple stages of axial loading and relaxation. The results show that inelastic strain develops at all stages of loading, and that its magnitude increases with increasing value of differential stress and initial porosity. The stress sensitivity of the axial creep strain rate and microstructural evidence suggest that inelastic compaction is controlled by a combination of intergranular slip and intragranular cracking. Intragranular cracking is shown to be more pervasive with increasing values of initial porosity. The results are consistent with a conceptual microphysical model, involving deformation by poro-elasticity combined with intergranular sliding and grain contact failure. This model aims to predict sandstone deformation behavior for a wide range of stress conditions.

Petrology and reservoir quality of the Gaikema Sandstone: Initial impressions

USGS Publications Warehouse

Helmold, Kenneth P.; Stanley, Richard G.

2015-01-01

The Division of Geological & Geophysical Surveys (DGGS) and Division of Oil & Gas (DOG) are currently conducting a study of the hydrocarbon potential of Cook Inlet basin (LePain and others, 2011). The Tertiary stratigraphic section of the basin includes coal-bearing units that are prolific gas reservoirs, particularly the Neogene sandstones. The Paleogene sandstones are locally prolific oil reservoirs that are sourced largely from the underlying Middle Jurassic Tuxedni Group. Several large structures act as hydrocarbon traps and the possibility exists for stratigraphic traps although this potential has not been fully exploited. As part of this study a significant number of Tertiary sandstones from the basin have been already collected and analyzed (Helmold and others, 2013). Recent field programs have shifted attention to the Mesozoic stratigraphic section to ascertain whether it contains potential hydrocarbon reservoirs. During the 2013 Cook Inlet field season, two days were spent on the Iniskin Peninsula examining outcrops of the Middle Jurassic Gaikema Sandstone along the south shore of Chinitna Bay (fig. 7-1). A stratigraphic section approximately 34 m in thickness was measured and a detailed description was initiated (Stanley and others, 2015), but due to deteriorating weather it was not possible to complete the description. During the 2014 field season two additional days were spent completing work on the Gaikema section. Analyses of thin sections from six of the samples collected in 2013 are available for incorporation in this report (table 7-1). Data from samples collected during the 2014 field season will be included in future reports.

Search for a meteoritic component at the Beaverhead impact structure, Montana

NASA Technical Reports Server (NTRS)

Lee, Pascal; Kay, Robert W.

1992-01-01

The Beaverhead impact structure, in southwestern Montana, was identified recently by the presence of shatter cones and impactites in outcrops of Proterozoic sandstones of the Belt Supergroup. The cones occur over an area greater than 100 sq km. Because the geologic and tectonic history of this region is long and complex, the outline of the original impact crater is no longer identifiable. The extent of the area over which shatter cones occur suggests, however, that the feature may have been at least 60 km in diameter. The absence of shatter cones in younger sedimentary units suggests that the impact event occurred in late Precambrian or early Paleozoic time. We have collected samples of shocked sandstone from the so-called 'Main Site' of dark-matrix breccias, and of impact breccias and melts from the south end of Island Butte. The melts, occurring often as veins through brecciated sandstone, exhibit a distinctive fluidal texture, a greenish color, and a cryptocrystalline matrix, with small inclusions of deformed sandstone. Samples of the same type, along with country rock, were analyzed previously for major- and trace-element abundances. It was found that, although the major-element composition as relatively uniform, trace-element composition showed variations between the melt material and the adjacent sandstone. These variations were attributed to extensive weathering and hydrothermal alteration. In a more specific search for a possible meteoritic signature in the breccia and the melt material we have conducted a new series of trace-element analyses on powders of our own samples by thermal neutron activation analysis. Our results indicate that Ir abundances in the breccia, the melts, and the adjacent sandstone clasts are no greater than about 0.1 ppb, suggesting no Ir enrichment of the breccia or the melts relative to the country rock. However, both the breccia and the melt material exhibit notable enrichments in Cr (8- and 10-fold), in U (9- and 5-fold), and in

Two possibilities for New Siberian Islands terrane tectonic history during the Early Paleozoic based on paleomagnetic data

NASA Astrophysics Data System (ADS)

Metelkin, Dmitry V.; Chernova, Anna I.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.

2017-04-01

The New Siberian Islands (NSI), located in the East Siberian Sea in the junction region of various structural elements, are a key target for deciphering the tectonic evolution of the Eastern Arctic. In recent years, we went on several expeditions and gathered an extensive geological material for this territory. Among other things, we could prove that the basement of the De Long and Anjou archipelagos structures is Precambrian and the overlying Paleozoic sections formed within the same terrane. The form of the boundaries of the NSI terrane are actively debated and are probably continued from the Lyakhovsky islands in the south-west to the southern parts of the submerged Mendeleev Ridge, for which there is increasing evidence of continental crust. Today there are several models that interpret the Paleozoic-Mesozoic tectonic history and structural affiliation of the NSI terrane. Some propose that the Paleozoic sedimentary section formed in a passive margin setting of the Siberian paleocontinent. Others compare its history with marginal basins of the Baltica and Laurentia continents or consider the NSI terrane as an element of the Chukotka-Alaska microplate. These models are mainly based on results of paleobiogeographical and lithological-facies analyses, including explanations of probable sources for detrital zircons. Our paleomagnetic research on sedimentary, volcanogenic-sedimentary and igneous rocks of the Anjou (Kotelny and Bel'kovsky islands) and De Long (Bennett, Jeannette and Henrietta islands) archipelagos let us calculate an apparent polar wander path for the early Paleozoic interval of geological history, which allows us to conclude that the NSI terrane could not have been a part of the continental plates listed above, but rather had active tectonic boundaries with them. Our paleomagnetic data indicate that the NSI terrane drifted slowly and steadily in the tropical and subtropical regions no higher than 40 degrees. However, the main uncertainty for the

The Inskip Formation, the Harmony Formation, and the Havallah Sequence of Northwestern Nevada - An Interrelated Paleozoic Assemblage in the Home of the Sonoma Orogeny

USGS Publications Warehouse

Ketner, Keith B.

2008-01-01

An area between the towns of Winnemucca and Battle Mountain in northwestern Nevada, termed the arkosic triangle, includes the type areas of the middle to upper Paleozoic Inskip Formation and Havallah sequence, the Upper Devonian to Mississippian Harmony Formation, the Sonoma orogeny, and the Golconda thrust. According to an extensive body of scientific literature, the Havallah sequence, a diverse assemblage of oceanic rocks, was obducted onto the continent during the latest Permian or earliest Triassic Sonoma orogeny by way of the Golconda thrust. This has been the most commonly accepted theory for half a century, often cited but rarely challenged. The tectonic roles of the Inskip and Harmony Formations have remained uncertain, and they have never been fully integrated into the accepted theory. New, and newly interpreted, data are incompatible with the accepted theory and force comprehensive stratigraphic and tectonic concepts that include the Inskip and Harmony Formations as follows: middle to upper Paleozoic strata, including the Inskip, Harmony, and Havallah, form an interrelated assemblage that was deposited in a single basin on an autochthonous sequence of Cambrian, Ordovician, and lowest Silurian strata of the outer miogeocline. Sediments composing the Upper Devonian to Permian sequence entered the basin from both sides, arkosic sands, gravel, limestone olistoliths, and other detrital components entered from the west, and quartz, quartzite, chert, and other clasts from the east. Tectonic activity was expressed as: (1) Devonian uplift and erosion of part of the outer miogeocline; (2) Late Devonian depression of the same area, forming a trough, probably fault-bounded, in which the Inskip, Harmony, and Havallah were deposited; (3) production of intraformational and extrabasinal conglomerates derived from the basinal rocks; and (4) folding or tilting of the east side of the depositional basin in the Pennsylvanian. These middle to upper Paleozoic deposits were

Hydrogeology of the Pictured Cliffs Sandstone in the San Juan structural basin, New Mexico, Colorado, Arizona, and Utah

USGS Publications Warehouse

Dam, William L.; Kernodle, J.M.; Thorn, C.R.; Levings, G.W.; Craigg, S.D.

1990-01-01

This report is one in a series resulting from the U.S. Geological Survey's Regional Aquifer System Analysis (RASA) study of the San Juan structural basin that began in October 1984. The purposes of the study (Welder, 1986) are to: (1) Define and evaluate the aquifer system; (2) assess the effects of past, present, and potential ground-water use on aquifers and streams, and (3) determine the availability and quality of ground water. Previous reports in this series describe the hydrogeology of the Dakota Sandstone (Craigg and others, 1989), Gallup Sandstone (Kernodle and others, 1989), Morrison Formation (Dam and others, 1990), Point Lookout Sandstone (Craigg and others, 1990), Kirtland Shale and Fruitland Formation (Kernodle and others, 1990), Menefee Formation (Levings and others, 1990), Cliff House Sandstone (Thorn and others, 1990), and Ojo Alamo Sandstone (Thorn and others, 1990) in the San Juan structural basin. This report summarizes information on the geology and the occurrence and quality of water in the Pictured Cliffs Sandstone, one of the primary water-bearing units in the regional aquifer system. Data used in this report were collected during the RASA study or derived from existing records in the U.S. Geological Survey's computerized National Water Information System (NWIS) data base, the Petroleum Information Corporation's data base, and the Dwight's ENERGYDATA Inc. BRIN database. Although all data available for the Pictured Cliffs Sandstone were considered in formulating the discussions in the text, not all those data could be plotted on the illustrations. The San Juan structural basin in New Mexico, Colorado, Arizona, and Utah has an area of about 21,600 square miles (fig. 1). The structural basin is about 140 miles wide and about 200 miles long. The study area is that part of the structural basin that contains rocks of Triassic and younger age; therefore, the study area is less extensive than the structural basin. Triassic through Tertiary

The structural evolution of the Ghadames and Illizi basins during the Paleozoic, Mesozoic and Cenozoic: Petroleum implications

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

Gauthier, F.J.; Boudjema, A.; Lounis, R.

1995-08-01

The Ghadames and Illizi basins cover the majority of the eastern Sahara of Algeria. Geologicaly, this part of the Central Saharan platform has been influenced by a series of structural arches and {open_quotes}moles{close_quotes} (continental highs) which controlled sedimentation and structure through geologic time. These features, resulting from and having been affected by nine major tectonic phases ranging from pre-Cambrian to Tertiary, completely bound the Ghadames and Illizi Basins. During the Paleozoic both basins formed one continuous depositional entity with the Ghadames basin being the distal portion of the continental sag basin where facies and thickness variations are observed over largemore » distances. It is during the Mesozoic-Cenozoic that the Ghadames basin starts to evolve differently from the Illizi Basin. Eustatic low-stand periods resulted in continental deposition yielding the major petroleum-bearing reservoir horizons (Cambrian, Ordovician, Siluro-Devonian and Carboniferous). High-stand periods corresponds to the major marine transgressions covering the majority of the Saharan platform. These transgressions deposited the principal source rock intervals of the Silurian and Middle to Upper Devonian. The main reservoirs of the Mesozoic and Cenozoic are Triassic sandstone sequences which are covered by a thick evaporite succession forming a super-seal. Structurally, the principal phases affecting this sequence are the extensional events related to the breakup of Pangea and the Alpine compressional events. The Ghadames and Illizi basins, therefore, have been controlled by a polphase tectonic history influenced by Pan African brittle basement fracturing which resulted in complex structures localized along the major basin bounding trends as well as several subsidiary trends within the basin. These trends, as demonstrated with key seismic data, have been found to contain the majority of hydrocarbons trapped.« less

Late Permian Forest Composition And Climate Revealed From High-Resolution Carbon Isotopes In Fossil Tree Rings

NASA Astrophysics Data System (ADS)

Gulbranson, E.; Isbell, J. L.; Taylor, E. L.; Ryberg, P. E.; Taylor, T. N.

2012-12-01

Late Permian forests from Antarctica are one of a few examples of polar forest biomes in Earth history. We present a paleoforestry and geochemical study of three contemporaneous Late Permian fossil forests and geochemical analysis of fossil wood specimens from the Permian-Triassic contact in Antarctica. Late Permian paleoforestry analysis suggests that these forests responded to disturbance in exactly the opposite manner as compared to modern boreal forests, with forest thinning and loss of understory vegetation occurring towards areas of disturbance. New high-resolution carbon isotope data from 6 permineralized stumps, 32 tree rings studied in total, indicate that these forests were mixed evergreen and deciduous, but dominated by deciduous trees. Moreover, intra-tree ring and ring-to-ring variation of δ13C values suggest that the Late Permian polar climate maintained wet winters, with precipitation in the austral winter being a factor of three greater than the austral summer. Such seasonality in precipitation implies the development of a temperate-like climate at polar latitudes following the demise of the late Paleozoic ice age. High-resolution carbon isotopes in tree rings in a stratigraphic succession of Late Permian fossil wood to fossil wood at the Permian-Triassic contact indicates that Antarctica experienced a change in precipitation patterns around the time of the Permian-Triassic boundary, marked by intervals of pronounced drying juxtaposed against wetter conditions.

Use of micro-resistivity imaging tools in developing lower Pennsylvanian Morrow channel sandstone reservoirs, Cheyenne, Kiowa and Lincoln Counties, Colorado

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

Germinario, M.P.

1996-01-01

In southeastern Colorado, Lower Pennsylvanian Morrow channel sandstones are part of complex valley-fill sequences incised into Morrow marine deposits. Morrow valleys are approximately [1/2] to 1 mile wide. Valley-fill consists of floodplain and channel filling shales, very fine-grained estuarine sandstones and fine- to coarse-grained channel sandstones that are up to 50' thick. Channel sandstones represent a sequence of stacked fluvial bars deposited in braided, anastomosing and meandering fluvial environments. Cross-stratification in channel sandstones can be imaged by micro-resistivity wireline logging tools and interpreted interactively on various workstation software packages. Recognition, interpretation and measurement of current, stoss face, and lateral accretionmore » beds in these sandstones can result in an estimated direction of paleocurrent flow of the channel. Determination of the channel's local paleoflow direction can provide significant sand risk reduction in developmental drilling, especially in 80 acre or less spacing patterns. As the distance between offset drilling locations increases, the reliability of paleoflow prediction decreases, and the corresponding sand risk rises. Lateral accretion bedding in Morrow channel sandstones has proven to be a poor indicator of sand thickening direction, due to the complex stacking of multiple channel sandstones within any given valley-fill sequence. Micro-resistivity imaging reduces risk in Morrow channel sandstone development drilling programs. Furthermore, these interpretation techniques could be applicable in other fluvial channel sandstone plays.« less

Use of micro-resistivity imaging tools in developing lower Pennsylvanian Morrow channel sandstone reservoirs, Cheyenne, Kiowa and Lincoln Counties, Colorado

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

Germinario, M.P.

1996-12-31

In southeastern Colorado, Lower Pennsylvanian Morrow channel sandstones are part of complex valley-fill sequences incised into Morrow marine deposits. Morrow valleys are approximately {1/2} to 1 mile wide. Valley-fill consists of floodplain and channel filling shales, very fine-grained estuarine sandstones and fine- to coarse-grained channel sandstones that are up to 50` thick. Channel sandstones represent a sequence of stacked fluvial bars deposited in braided, anastomosing and meandering fluvial environments. Cross-stratification in channel sandstones can be imaged by micro-resistivity wireline logging tools and interpreted interactively on various workstation software packages. Recognition, interpretation and measurement of current, stoss face, and lateral accretionmore » beds in these sandstones can result in an estimated direction of paleocurrent flow of the channel. Determination of the channel`s local paleoflow direction can provide significant sand risk reduction in developmental drilling, especially in 80 acre or less spacing patterns. As the distance between offset drilling locations increases, the reliability of paleoflow prediction decreases, and the corresponding sand risk rises. Lateral accretion bedding in Morrow channel sandstones has proven to be a poor indicator of sand thickening direction, due to the complex stacking of multiple channel sandstones within any given valley-fill sequence. Micro-resistivity imaging reduces risk in Morrow channel sandstone development drilling programs. Furthermore, these interpretation techniques could be applicable in other fluvial channel sandstone plays.« less

Late Proterozoic glacially controlled shelf sequences in western Mali (west Africa)

NASA Astrophysics Data System (ADS)

Deynoux, M.; Prousti, J. N.; Simon, B.

The Late Proterozoic deposits of the Bakoye Group (500 m) in western Mali constitute a remarkable example of a glacially influenced sedimentary record on an epicratonic platform. They are composed of alternating marine and continental formations which represent accumulation in a basin located in the vicinity of upland areas covered by ice sheets. One of these formations (the Ba4 Formation), which is the focus of this study, is composed of three major units. The basal Unit 1 is made up of carbonaceous coarse to fine grained sandstones which are organized in fining upward sequences and which comprise lenticular diamictite intercalations. This Unit is considered to represent the fore slope gravity flows of a subaqueous ice-cootact fan fed by meltwater streams (≪glacioturbidites≫). Unit 2 is made up of coarse to fine grained sandstones in a highly variable association of facies. This Unit is characterized by the abundance of wave ripples associated with convolute beddings. planar or wavy beddings and tabular or hummocky crossbeddings in a general shallowing upward trend. It also comprises evidence of gravity processes including debris flows and large slumped sandstone bodies. Unit 2 represents the progressive filling of the Ba4 basin and reflects the combined effect of glacially induced eustatism and isostacy during a phase of glacial retreat. The basal part of Unit 3 is made up of a succession (a few meters thick) of conglomerates, diamictites, sandstones, siltstones or carbonates lying on an erosional unconformity marked by periglacial frost wedges. The upper part of Unit 3 is thicker (100-150 m) and onlaps on these basal facies with a succession of sandstone bars exhibiting swaley and hummocky crossbeddings, large cut and fill structures, and planar laminations. Unit 3 is strongly transgressive, the lower shoreface and backshore deposits include algal mats and are onlapped by sand ridges emplaced in a high energy upper to middle shoreface environment. Overall

Diagenetic controls on reservoir heterogeneity in St. Peter Sandstone, deep Michigan basin

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

Barnes, D.A.; Turmelle, T.M.; Adam, R.

1989-03-01

The St. Peter Sandstone is a highly productive gas and condensate reservoir throughout the central part of the Michigan basin. Production occurs in several intervals: a laterally continuous zone at the top of the formation typified in the Woodville, Falmouth, and Rose City fields and less continuous intervals lower in the formation typified in the Ruwe Gulf zone of the Reed City field. Porosity is not limited to hydrocarbon productive zones, however. Diagenesis has dramatically modified primary mineralogy and textures in the formation. Dominant diagenetic components are quartz, dolomite, and clay authigenic cements, extensive chemical compaction, and pervasive mineral leaching.more » Their model for sandstone diagenesis is consistent throughout the basin. Variation in the significance of these diagenetic components is strongly templated by stratigraphically predictable facies variations within the St. Peter Sandstone.« less

Experimental and Numerical Investigations on Strength and Deformation Behavior of Cataclastic Sandstone

NASA Astrophysics Data System (ADS)

Zhang, Y.; Shao, J. F.; Xu, W. Y.; Zhao, H. B.; Wang, W.

2015-05-01

This work is devoted to characterization of the deformation and strength properties of cataclastic sandstones. Before conducting mechanical tests, the physical properties were first examined. These sandstones are characterized by a loose damaged microstructure and poorly cemented contacts. Then, a series of mechanical tests including hydrostatic, uniaxial, and triaxial compression tests were performed to study the mechanical strength and deformation of the sandstones. The results obtained show nonlinear stress-strain responses. The initial microcracks are closed at hydrostatic stress of 2.6 MPa, and the uniaxial compressive strength is about 0.98 MPa. Under triaxial compression, there is a clear transition from volumetric compressibility to dilatancy and a strong dependency on confining pressure. Based on the experimental evidence, an elastoplastic model is proposed using a linear yield function and a nonassociated plastic potential. There is good agreement between numerical results and experimental data.

Geologic map of the Vail West quadrangle, Eagle County, Colorado

USGS Publications Warehouse

Scott, Robert B.; Lidke, David J.; Grunwald, Daniel J.

2002-01-01

This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range. Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit. Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the

Mass extinction of ocean organisms at the Paleozoic-Mesozoic boundary: Effects and causes

NASA Astrophysics Data System (ADS)

Barash, M. S.

2012-04-01

At the end of the Permian, at the boundary between the Paleozoic and Mesozoic (251.0 ± 0.4 Ma), the largest mass extinction of organisms on the Earth occurred. Up to 96% of the species of marine invertebrates and ˜70% of the terrestrial vertebrates died off. A lot of factors were suggested and substantiated to explain this mass mortality, such as the disappearance of environmental niches in the course of the amalgamation of the continental plates into Pangea, sea level fluctuations, anoxia, an elevated CO2 content, H2S intoxication, volcanism, methane discharge from gas-hydrates, climate changes, impact events (collisions with large asteroids), or combinations of many of these reasons. Some of these factors are in subordination to others, while others are independent. Almost all of these factors developed relatively slowly and could not cause the sudden mass mortality of organisms globally. It could have happened when large asteroids, whose craters have been discovered lately, fell to the Earth. It is suggested that the impact events "finished off" the already suppressed biota. A simultaneous change in many of the factors responsible for the biodiversity, including those not connected in a cause-and-effect relationship, proves the existence of a common extrater-restrial cause that affected both the changes in the internal and external geospheres and the activation of asteroid attacks (the Sun's transit of spiral arms of our galaxy, the Sun's oscillations perpendicularly to the galactic plane, etc).

A new model for the provenance of the Upper Devonian Old Red Sandstone (UORS) of southern Ireland

NASA Astrophysics Data System (ADS)

Ennis, Meg; Meere, Pat; Timmerman, Martin

2010-05-01

The geology of Southern Ireland is dominated by the influence of both the Caledonian and Variscan orogenies which have shaped the landscape of today. The Old Red Sandstone (ORS) sequences of the Middle - Upper Devonian Munster Basin have traditionally been viewed as a post-orogenic molasse deposit sourced from the Caledonides (Friend et al. 2000 & references therein), which were subsequently deformed by the Late Carboniferous Variscan Orogeny. This model does not take into account the potential impact of the Acadian Orogeny, an Early to Mid Devonian transpressional tectonic event which culminated in Mid Emsian times and resulted in the deformation and inversion of Lower ORS (LORS) basins across Britain and Ireland (Soper & Woodcock 2003; Meere & Mulchrone 2006). Evidence of Acadian deformation in Southern Ireland is recorded in the LORS sequence of the Lower-Middle Devonian basin, the Dingle Basin. Meere & Mulchrone (2006) show that penetrative deformation visible in the LORS of the Dingle Basin has an Acadian signature and is not associated with Late Carboniferous Variscan compression (Parkin 1976; Todd 2000). The role of the Acadian Orogeny in the tectono-sedimentary evolution of Southern Ireland has been analyzed in this study using a multidisciplinary approach. Petrographic analysis of both the LORS and Upper ORS (UORS) of southern Ireland suggests an alternative provenance model in which there is a direct genetic link between the two Devonian deposits. There is a fining-up relationship between the two basins and the volcanic lithic fragments - while extremely limited in occurrence in the Munster Basin - are strikingly similar in both units. The absence of conglomeratic units at the base of the Munster Basin provide further evidence that the UORS does not represent a classic molasse deposit. This is supported by EMPA data from both basins which indicates identical mica chemistries in both the LORS and UORS. A comparison with the white mica chemistries from a

Nugget-Navaho-Aztec sandstone: interaction of eolian sand sea with Andean-type volcanic arc

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

Marzolf, J.E.

1986-05-01

The Nugget-Navaho-Aztec sand sea was deposited east of an Andean-type volcanic arc. During the early stage of eolian deposition, fluvially transported sand was concentrated in the marine littoral zone and returned inland by onshore winds from the northwest. With progressive development of the arc, the sea withdrew. Wind direction changed from northwest to northeast. Previously deposited eolian sand was transported southwestward into the volcanic arc. Proximity of the arc can be detected with great difficulty by examining eolian and underlying red-bed facies. In southern Nevada, the volcanic arc is undetectable in eolian facies, but thin sandstone beds containing volcanic clastsmore » or weathered feldspar in the finer grained red-bed facies indicate arc volcanism; volcanic clasts are distinct in a basal conglomerate. Westward into California, the sub-Aztec Sandstone contains volcanic pebbles. The upper part of the Aztec Sandstone contains a 1 to 2-m thick volcaniclastic siltstone. Farther west, the Aztec Sandstone is interbedded with volcanic flows, ash flows, and flow breccias. These rocks might easily be mistaken for red beds in well cores or cuttings. Sand in sets of large-scale cross-beds remain virtually identical in composition and texture to sand in eolian facies of the Colorado Plateau. Where sets of eolian cross-beds lie on volcanics, the quartzose sandstone contains pebble to cobble-size volcanic clasts. Locally, cross-bed sets of yellowish-white, quartzose sandstone alternate with purplish-gray cross-bed sets containing numerous pebble to cobble-size volcanic clasts. The ability to recognize volcanic indicators within Nugget-Navaho-Aztec eolian facies is important in delineating the western margin of the back-arc eolian basin.« less

Numerical simulation of multi-dimensional NMR response in tight sandstone

NASA Astrophysics Data System (ADS)

Guo, Jiangfeng; Xie, Ranhong; Zou, Youlong; Ding, Yejiao

2016-06-01

Conventional logging methods have limitations in the evaluation of tight sandstone reservoirs. The multi-dimensional nuclear magnetic resonance (NMR) logging method has the advantage that it can simultaneously measure transverse relaxation time (T 2), longitudinal relaxation time (T 1) and diffusion coefficient (D). In this paper, we simulate NMR measurements of tight sandstone with different wettability and saturations by the random walk method and obtain the magnetization decays of Carr-Purcell-Meiboom-Gill pulse sequences with different wait times (TW) and echo spacings (TE) under a magnetic field gradient, resulting in D-T 2-T 1 maps by the multiple echo trains joint inversion method. We also study the effects of wettability, saturation, signal-to-noise ratio (SNR) of data and restricted diffusion on the D-T 2-T 1 maps in tight sandstone. The results show that with decreasing wetting fluid saturation, the surface relaxation rate of the wetting fluid gradually increases and the restricted diffusion phenomenon becomes more and more obvious, which leads to the wetting fluid signal moving along the direction of short relaxation and the direction of the diffusion coefficient decreasing in D-T 2-T 1 maps. Meanwhile, the non-wetting fluid position in D-T 2-T 1 maps does not change with saturation variation. With decreasing SNR, the ability to identify water and oil signals based on NMR maps gradually decreases. The wetting fluid D-T 1 and D-T 2 correlations in NMR diffusion-relaxation maps of tight sandstone are obtained through expanding the wetting fluid restricted diffusion models, and are further applied to recognize the wetting fluid in simulated D-T 2 maps and D-T 1 maps.

Multielement statistical evidence for uraniferous hydrothermal activity in sandstones overlying the Phoenix uranium deposit, Athabasca Basin, Canada

NASA Astrophysics Data System (ADS)

Chen, Shishi; Hattori, Keiko; Grunsky, Eric C.

2018-04-01

The Phoenix U deposit, with indicated resources of 70.2 M lb U3O8, occurs along the unconformity between the Proterozoic Athabasca Group sandstones and the crystalline basement rocks. Principal component analysis (PCA) is applied to the compositions of sandstones overlying the deposit. Among PCs, PC1 accounts for the largest variability of U and shows a positive association of U with rare earth elements (REEs) + Y + Cu + B + Na + Mg + Ni + Be. The evidence suggests that U was dispersed into sandstones together with these elements during the uraniferous hydrothermal activity. Uranium shows an inverse association with Zr, Hf, Th, Fe, and Ti. Since they are common in detrital heavy minerals, such heavy minerals are not the major host of U. The elements positively associated with U are high in concentrations above the deposit, forming a "chimney-like" or "hump-like" distribution in a vertical section. Their enrichment patterns are explained by the ascent of basement fluids through faults to sandstones and the circulation of basinal fluids around the deposit. The Pb isotope compositions of whole rocks are similar to expected values calculated from the concentrations of U, Th, and Pb except for sandstones close to the deposit. The data suggest that in situ decay of U and Th is responsible for the Pb isotope compositions of most sandstones and that highly radiogenic Pb dispersed from the deposit to the proximal sandstones long after the mineralization. This secondary dispersion is captured in PC8, which has low eigenvalue. The data suggests that the secondary dispersion has minor effect on the overall lithogeochemistry of sandstones.

Controls on the variability of net infiltration to desert sandstone

USGS Publications Warehouse

Heilweil, Victor M.; McKinney, Tim S.; Zhdanov, Michael S.; Watt, Dennis E.

2007-01-01

As populations grow in arid climates and desert bedrock aquifers are increasingly targeted for future development, understanding and quantifying the spatial variability of net infiltration becomes critically important for accurately inventorying water resources and mapping contamination vulnerability. This paper presents a conceptual model of net infiltration to desert sandstone and then develops an empirical equation for its spatial quantification at the watershed scale using linear least squares inversion methods for evaluating controlling parameters (independent variables) based on estimated net infiltration rates (dependent variables). Net infiltration rates used for this regression analysis were calculated from environmental tracers in boreholes and more than 3000 linear meters of vadose zone excavations in an upland basin in southwestern Utah underlain by Navajo sandstone. Soil coarseness, distance to upgradient outcrop, and topographic slope were shown to be the primary physical parameters controlling the spatial variability of net infiltration. Although the method should be transferable to other desert sandstone settings for determining the relative spatial distribution of net infiltration, further study is needed to evaluate the effects of other potential parameters such as slope aspect, outcrop parameters, and climate on absolute net infiltration rates.

Revisions to the original extent of the Devonian Shale-Middle and Upper Paleozoic Total Petroleum System

USGS Publications Warehouse

Enomoto, Catherine B.; Rouse, William A.; Trippi, Michael H.; Higley, Debra K.

2016-04-11

Technically recoverable undiscovered hydrocarbon resources in continuous accumulations are present in Upper Devonian and Lower Mississippian strata in the Appalachian Basin Petroleum Province. The province includes parts of New York, Pennsylvania, Ohio, Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia, and Alabama. The Upper Devonian and Lower Mississippian strata are part of the previously defined Devonian Shale-Middle and Upper Paleozoic Total Petroleum System (TPS) that extends from New York to Tennessee. This publication presents a revision to the extent of the Devonian Shale-Middle and Upper Paleozoic TPS. The most significant modification to the maximum extent of the Devonian Shale-Middle and Upper Paleozoic TPS is to the south and southwest, adding areas in Tennessee, Georgia, Alabama, and Mississippi where Devonian strata, including potential petroleum source rocks, are present in the subsurface up to the outcrop. The Middle to Upper Devonian Chattanooga Shale extends from southeastern Kentucky to Alabama and eastern Mississippi. Production from Devonian shale has been established in the Appalachian fold and thrust belt of northeastern Alabama. Exploratory drilling has encountered Middle to Upper Devonian strata containing organic-rich shale in west-central Alabama. The areas added to the TPS are located in the Valley and Ridge, Interior Low Plateaus, and Appalachian Plateaus physiographic provinces, including the portion of the Appalachian fold and thrust belt buried beneath Cretaceous and younger sediments that were deposited on the U.S. Gulf Coastal Plain.

Late orogenic, large-scale rotations in the Tien Shan and adjacent mobile belts in Kyrgyzstan and Kazakhstan

NASA Astrophysics Data System (ADS)

Van der Voo, Rob; Levashova, Natalia M.; Skrinnik, Ludmila I.; Kara, Taras V.; Bazhenov, Mikhail L.

2006-11-01

Most of Kazakhstan belongs to the central part of the Eurasian Paleozoic mobile belts for which previously proposed tectonic scenarios have been rather disparate. Of particular interest is the origin of strongly curved Middle and Late Paleozoic volcanic belts of island-arc and Andean-arc affinities that dominate the structure of Kazakhstan. We undertook a paleomagnetic study of Carboniferous to Upper Permian volcanics and sediments from several localities in the Ili River basin between the Tien Shan and the Junggar-Alatau ranges in southeast Kazakhstan. Our main goal was to investigate the Permian kinematic evolution of these belts, particularly in terms of rotations about vertical axes, in the hope of deciphering the dynamics that played a role during the latest Paleozoic deformation in this area. This deformation, in turn, can then be related to the amalgamation of this area with Baltica, Siberia, and Tarim in the expanding Eurasian supercontinent. Thermal demagnetization revealed that most Permian rocks retained a pretilting and likely primary component, which is of reversed polarity at three localities and normal at the fourth. In contrast, most Carboniferous rocks are dominated by postfolding reversed overprints of probably "mid-Permian" age, whereas presumably primary components are isolated from a few sites at two localities. Mean inclinations of primary components generally agree with coeval reference values extrapolated from Baltica, whereas declinations from primary as well as secondary components are deflected counterclockwise (ccw) by up to ˜ 90°. Such ccw rotated directions have previously also been observed in other Tien Shan sampling areas and in the adjacent Tarim Block to the south. However, two other areas in Kazakhstan show clockwise (cw) rotations of Permian magnetization directions. One area is located in the Kendyktas block about 300 km to the west of the Ili River valley, and the other is found in the Chingiz Range, to the north of Lake

Sandstone type uranium deposits in the Ordos Basin, Northwest China: A case study and an overview

NASA Astrophysics Data System (ADS)

Akhtar, Shamim; Yang, Xiaoyong; Pirajno, Franco

2017-09-01

This paper provides a comprehensive review on studies of sandstone type uranium deposits in the Ordos Basin, Northwest China. As the second largest sedimentary basin, the Ordos Basin has great potential for targeting sandstone type U mineralization. The newly found and explored Dongsheng and Diantou sandstone type uranium deposits are hosted in the Middle Jurassic Zhilou Formation. A large number of investigations have been conducted to trace the source rock compositions and relationship between lithic subarkose sandstone host rock and uranium mineralization. An optical microscopy study reveals two types of alteration associated with the U mineralization: chloritization and sericitization. Some unusual mineral structures, with compositional similarity to coffinite, have been identified in a secondary pyrite by SEM These mineral phases are proposed to be of bacterial origin, following high resolution mapping of uranium minerals and trace element determinations in situ. Moreover, geochemical studies of REE and trace elements constrained the mechanism of uranium enrichment, displaying LREE enrichment relative to HREE. Trace elements such as Pb, Mo and Ba have a direct relationship with uranium enrichment and can be used as index for mineralization. The source of uranium ore forming fluids and related geological processes have been studied using H, O and C isotope systematics of fluid inclusions in quartz veins and the calcite cement of sandstone rocks hosting U mineralization. Both H and O isotopic compositions of fluid inclusions reveal that ore forming fluids are a mixture of meteoric water and magmatic water. The C and S isotopes of the cementing material of sandstone suggest organic origin and bacterial sulfate reduction (BSR), providing an important clue for U mineralization. Discussion of the ore genesis shows that the greenish gray sandstone plays a crucial role during processes leading to uranium mineralization. Consequently, an oxidation-reduction model for

The significance of stylolitization and intergranular pressure solution in the formation of pressure compartment seals in the St. Peter Sandstone, Ordovician, Michigan basin

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

Drzewiecki, P.A.; Simo, T.; Moline, G.

1991-03-01

The Middle to Late Ordovician St. Peter Sandstone of the Michigan basin is a fine- to medium-grained quartz sandstone. Extensive stylolitization and intergranular pressure solution have been major factors in reducing the porosity of certain horizons within the St. Peter, resulting in pressure compartmentation of the reservoir. Pressure versus depth data for various Michigan basin wells indicate that the basin contains compartments that are overpressured by as much as 500 psi. Horizons bounding these compartments are often affected by intense stylolitization (or intergranular pressure solution) and quartz cementation and have been correlated with zones of low porosity and permeability ({phi}more » = 0-3%, k = <50 {mu}d). These tight zones can be correlated within single gas fields, and some may extend across the Michigan basin. The St. Peter Sandstone has been buried to depths of about 3,500 m in the central part of the basin and 1,500 m at the margins. Intensely stylolitized zones are found at all depths throughout the basin and do not appear to change in abundance or style with depths. Factors that influence the formation, morphology, and abundance of stylolites in the St. Peter include (1) clay intraclasts, (2) intergranular clay, and (3) fine-grained, feldspar-rich sand. Stylolites also occur at contacts between quartz-cemented and carbonate-cemented zones and within well-cemented sands. Intergranular pressure solution and stylolites may be responsible for the formation of a compartment seal. Understanding their genesis can allow prediction of variations in porosity in Michigan basin well cores.« less

A new bee species that excavates sandstone nests

USDA-ARS?s Scientific Manuscript database

Many wonder why animals act in seemingly injurious ways. Understanding the behavior of pollinators such as bees is especially important because of the necessary ecosystem service they provide. The new species Anthophora pueblo, discovered excavating sandstone nests, provides a model system for addre...

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

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

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

1985-04-01

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 inmore » 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.« less

Coastal dune facies, Permian Cutler Formation (White Rim Sandstone), Capitol Reef National Park area, southern Utah

NASA Astrophysics Data System (ADS)

Kamola, Diane L.; Chan, Marjorie A.

1988-04-01

The Permian Cutler Formation (White Rim Sandstone) in the Capitol Reef National Park area in southern Utah is an excellent example of a coastal dune complex subjected to periodic flooding by marine waters. Wind-ripple, grainfall and grainflow laminae compose the cross-sets deposited by eolian dunes. However, wave-reworked structures such as oscillation ripples, the occurrence of the characteristically marine trace fossils Thalassinoides and Chondrites, and interfingering marine carbonate beds of the Kaibab Formation collectively indicate marine interaction with the eolian environment. Four facies are distinguished: cross-stratified sandstone, burrowed to bioturbated sandstone, brecciated and deformed sandstone, and ripple-laminated sandstone and thin carbonate beds. One unusual aspect of the cross-stratified sandstone facies is the abundance of coarse-grained sand. Coarse-grained sand is atypical in many ancient eolian slipface deposits, but occurs here in large slipface foresets as both grainflow and wind-ripple deposits. No water-laid structures are found in these slipface deposits. Coarse-grained sand was probably transported to the Cutler shoreline by fluvial systems draining the Uncompahgre Uplift to the east, and then concentrated as coarse-grained ripples in interdune areas. Some of these coarse-grained ripples migrated up the stoss side of the dunes and accumulations of coarse-grained sand avalanched down the crest to form grainflow deposits. An extensive amount of soft-sediment deformation is indicated by the presence of convolute bedding and brecciation. These features occur near the zone of interfingering with marine carbonate beds of the Kaibab Formation. The water-saturated and moist conditions required for extensive deformation may have been controlled by the proximity of these sandstones to the shoreline, and fluctuations in the associated groundwater table.

Characterizing flow pathways in a sandstone aquifer at multiple depths

NASA Astrophysics Data System (ADS)

Medici, Giacomo; West, Jared; Mountney, Nigel

2017-04-01

Sandstone aquifers are commonly assumed to represent porous media characterized by a permeable matrix. However, such aquifers may be heavily fractured where rock properties and timing of deformation favour brittle failure and crack opening. In many aquifer types, fractures associated with faults, bedding planes and stratabound joints represent preferential pathways for fluids and contaminants. This presentation reports well-test results and outcrop-scale studies that reveal how strongly lithified siliciclastic rocks may be entirely dominated by fracture flow at shallow depths (≤ 150 m), similar to limestone and crystalline aquifers. The Triassic St Bees Sandstone Formation of the UK East Irish Sea Basin represents an optimum succession for study of the influence of both sedimentary and tectonic aquifer heterogeneities in a strongly lithified sandstone aquifer-type. This sedimentary succession of fluvial origin accumulated in rapidly subsiding basins, which typically favour preservation of complete depositional cycles, including fine-grained mudstone and silty sandstone layers of floodplain origin interbedded with sandstone-dominated fluvial channel deposits. Vertical joints in the St Bees Sandstone Formation form a pervasive stratabound system whereby joints terminate at bedding-parallel discontinuities. Additionally, normal faults are present through the succession and record development of open-fractures in their damage zones. Here, the shallow aquifer (depth ≤150 m BGL) was characterized in outcrop and well tests. Fluid temperature, conductivity and flow-velocity logs record inflows and outflows from normal faults, as well as from pervasive bed-parallel fractures. Quantitative flow logging analyses in boreholes that cut fault planes indicate that zones of fault-related open fractures typically represent ˜ 50% of well transmissivity. The remaining flow component is dominated by bed-parallel fractures. However, such sub-horizontal fractures become the

Cenozoic Tectonic Activity of the "Passive" North America Margin: Evidence for Cenozoic Activity on Mesozoic or Paleozoic Faults

NASA Astrophysics Data System (ADS)

Nedorub, O. I.; Knapp, C. C.

2012-12-01

The tectonic history of the Eastern North American Margin (ENAM) incorporates two cycles of continental assembly, multiple pulses of orogeny, rifting, and post-rift geodynamic evolution. This is reflected in the heterogeneous lithosphere of the ENAM which contains fault structures originated in Paleozoic to Mesozoic eras. The South Georgia Rift basin is probably the largest Mesozoic graben within its boundaries that is associated with the breakup of Pangea. It is composed of smaller sub-basins which appear to be bounded by high-angle normal faults, some of which may have been inverted in late Cretaceous and Cenozoic eras. Paleozoic structures may have been reactivated in Cenozoic time as well. The ENAM is characterized by N-NE maximum horizontal compressive stress direction. This maximum compressional stress field is sub-parallel to the strike of the Atlantic Coast province fault systems. Camden, Augusta, Allendale, and Pen Branch faults are four of the many such reactivated faults along the southern part of ENAM. These faults are now buried under the 0-400 m of loosely consolidated Cretaceous and Cenozoic age sediments and thus are either only partially mapped or currently not recognized. Some of the objectives of this study are to map the subsurface expression and geometry of these faults and to investigate the post Cretaceous deformation and possible causes of fault reactivation on a passive margin. This study employs an integrated geophysical approach to investigate the upper 200 m of identified locations of the above mentioned faults. 2-D high-resolution shallow seismic reflection and refraction methods, gravity surveys, GPR, 2-D electrical resistivity and well data are used for analyses and interpretation. Preliminary results suggest that Camden fault shows signs of Cenozoic reactivation through an approximately 30 m offset NW side up mainly along a steeply dipping fault zone in the basal contact of Coastal Plain sediments with the Carolina Piedmont. Drill

Effects of pore pressure and mud filtration on drilling rates in a permeable sandstone

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

Black, A.D.; DiBona, B.; Sandstrom, J.

1983-10-01

During laboratory drilling tests in a permeable sandstone, the effects of pore pressure and mud filtration on penetration rates were measured. Four water-base muds were used to drill four saturated sandstone samples. The drilling tests were conducted at constant borehole pressure with different back pressures maintained on the filtrate flowing from the bottom of the sandstone samples. Bit weight was also varied. Filtration rates were measured while drilling and with the bit off bottom and mud circulating. Penetration rates were found to be related to the difference between the filtration rates measured while drilling and circulating. There was no observedmore » correlation between standard API filtration measurements and penetration rate.« less

Effects of pore pressure and mud filtration on drilling rates in a permeable sandstone

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

Black, A.D.; Dearing, H.L.; DiBona, B.G.

1985-09-01

During laboratory drilling tests in a permeable sandstone, the effects of pore pressure and mud filtration on penetration rates were measured. Four water-based muds were used to drill four saturated sandstone samples. The drilling tests were conducted at constant borehole pressure while different backpressures were maintained on the filtrate flowing from the bottom of the sandstone samples. Bit weight was varied also. Filtration rates were measured while circulating mud during drilling and with the bit off bottom. Penetration rates were found to be related qualitatively to the difference between the filtration rates measured while drilling and circulating. There was nomore » observed correlation between standard API filtration measurements and penetration rate.« less

Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)

NASA Astrophysics Data System (ADS)

Brookfield, Michael E.

2008-10-01

The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature

Age and origin of the Merrimack terrane, southeastern New England: A detrital zircon U-Pb geochronology study

NASA Astrophysics Data System (ADS)

Sorota, Kristin

Metasedimentary rocks of the Merrimack terrane (MT) originated as a thick cover sequence on Ganderia consisting of sandstones, calcareous sandstones, pelitic rocks and turbidites. In order to investigate the age, provenance and stratigraphic order of these rocks and correlations with adjoining terranes, detrital zircon suites from 7 formations across the MT along a NNE-trending transect from east-central Massachusetts to SE New Hampshire were analyzed by U-Pb LA-ICP-MS methods on 90-140 grains per sample. The youngest detrital zircons in the western units, the Worcester, Oakdale and Paxton Formations, are ca. 438 Ma while those in the Kittery, Eliot and Berwick Formations in the northeast are ca. 426 Ma. The Tower Hill Formation previously interpreted to form the easternmost unit of the MT in MA, has a distinctly different zircon distribution with its youngest zircon population in the Cambrian. All samples except for the Tower Hill Formation have detrital zircon age distributions with significant peaks in the mid-to late Ordovician, similar abundances of early Paleozoic and late Neoproterozoic zircons, significant input from ˜1.0 to ˜1.8 Ga sources and limited Archean grains. The similarities in zircon provenance suggest that all units across the terrane, except for the Tower Hill Formation, belong to a single sequence of rocks, with similar sources and with the units in the NE possibly being somewhat younger than those in east-central Massachusetts. The continuous zircon age distributions observed throughout the Mesoproterozoic and late Paleoproterozoic are consistent with an Amazonian source. All samples, except the Tower Hill Formation, show sedimentary input from both Ganderian and Laurentian sources and suggest that Laurentian input increases as the maximum depositional age decreases.

Cordilleran hingeline: Late Precambrian rifted margin of the North American craton and its impact on the depositional and structural history, Utah and Nevada

NASA Astrophysics Data System (ADS)

Picha, Frank; Gibson, Richard I.

1985-07-01

The structural pattern set by late Precambrian rifting and fragmentation of the North American continent is apparent in both sedimentary and tectonic trends in western Utah and eastern Nevada. The late Precambrian cratonic margin (Cordilleran hingeline) displays several prominent structural features, such as the Wasatch and Ancient Ephraim faults, Fillmore arch and northeast-trending lineaments, which were repeatedly reactivated as structural uplifts, ramps, strike-slip faults, and extensional detachments. The renewed activity affected, among others, the geometry of the late Paleozoic Ancestral Rocky Mountain uplifts and basins, the extent of the Jurassic Arapien basin, the sedimentary pattern of the Cretaceous foreland basin, the geometry of the Sevier orogenic belt, and the extent and type of Basin-and-Range extensional tectonics. The rifted cratonic margin has thus remained a major influence on regional structures long after rifting has ceased. *Present address: Everest Geotech, 10101 Southwest Freeway, Houston, Texas 77074

Depositional systems and stratigraphy of Paleozoic and Lower Mesozoic rocks in outcrop, Tassili region, southwest Algeria

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

Hertig, S.P.; Tye, R.S.; Coffield, D.Q.

1991-08-01

Paleozoic to Lower Mesozoic strata of the southeastern Algerian Tassili are traditionally subdivided by regionally extensive unconformities such as the Pan African, Taconic, Caledonian, and Hercynian. Using outcrop data from southeastern Algeria, this classic approach is modified by reinterpreting the genesis of these unconformities and rock sequences. Five prominent sequences, defined within the Paleozoic and lower Mesozoic section, usually consist of a succession of lowstand, transgressive, and highstand system tracts separated by sequence boundaries or transgressive surfaces. The Pan-African, Taconic, Caledonian, and Hercynian unconformities are sequence boundaries. Important sequence boundaries also occur within the Ordovician and Silurian sections. These sequencesmore » correlate with subsurface data in the Illizi basin and provide a framework for renewed exploration in the subsurface of the Algerian Sahara, where more than 30 billion bbl of recoverable oil and oil equivalent have been generated and trapped.« less

Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

USGS Publications Warehouse

Castle, J.W.; Byrnes, A.P.

2005-01-01

Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 1-6 m (3-20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low S iw (<20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4-12%), lower permeability (0.0007-4 md), thicker transition zones (6-180 m [20-600 ft]), and higher S iw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average < 6%), low permeability (average < 0.02 md), and small pore throats result in large transition zones (30-200 m; 100-650 ft) and high water saturations. The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

The tectonic evolution of western Central Iran seen through detrital white mica

NASA Astrophysics Data System (ADS)

Kargaranbafghi, Fariba; Neubauer, Franz; Genser, Johann

2015-05-01

A first order survey of 40Ar/39Ar dating of detrital white mica from Jurassic to Pliocene sandstones has been carried out in order to reveal the tectonic evolution of blocks in Central Iran. The Central Iran block was believed to represent a stable Precambrian block. Our results indicate that: (1) Only a very small proportion of Precambrian but abundant Paleozoic and Mesozoic detrital white mica indicate the Phanerozoic, mostly Mesozoic age of metamorphic crust exposed in Central Iran. The oldest but scarce detrital white mica grains have ages ranging from 524 to 826 Ma heralding a Late Precambrian and Cambrian crystalline basement or cannibalism from older clastic successions. (2) Jurassic and Cretaceous sandstones from the west and east of the Chapedony fault yield different age spectra, with a dominance of Variscan ages (ca. 308-385 Ma) in the Biabanak unit west of the Chapedony fault compared to coeval sandstones from the block east of the Chapedony fault, where Variscan ages are subordinate and Cimmerian ages predominate. The micas from the Biabanak unit are most likely derived from the Variscan accretionary complex exposed in the Anarak-Jandaq areas further northwest. This result underlines the importance of a major block boundary identified as the Chapedony fault, which is in extension of a fault previously proposed. (3) Two stages of Cimmerian events are visible in our data set from Cretaceous and Paleogene sandstones, a cluster around 170 Ma and at ca. 205 Ma. These clusters suggest a two-stage Cimmerian evolution of the largely amphibolite-grade metamorphic Posht-e-Badam and Boneh Shurow complexes. (4) The youngest micas in Paleogene conglomerates have an age of ca. 100 Ma and are most likely derived from the base of the Posht-e-Badam complex. No record of the uplifted Eocene Chapedony metamorphic core complex has been found in Eocene and Pliocene clastic rocks.

Sedimentary and tectonic evolution of the southern Qiangtang basin: Implications for the Lhasa-Qiangtang collision timing

NASA Astrophysics Data System (ADS)

Ma, Anlin; Hu, Xiumian; Garzanti, Eduardo; Han, Zhong; Lai, Wen

2017-07-01

The Mesozoic stratigraphic record of the southern Qiangtang basin in central Tibet records the evolution and closure of the Bangong-Nujiang ocean to the south. The Jurassic succession includes Toarcian-Aalenian shallow-marine limestones (Quse Formation), Aalenian-Bajocian feldspatho-litho-quartzose to feldspatho-quartzo-lithic sandstones (shallow-marine Sewa Formation and deep-sea Gaaco Formation), and Bathonian outer platform to shoal limestones (Buqu Formation). This succession is truncated by an angular unconformity, overlain by upper Bathonian to lower Callovian fan-delta conglomerates and litho-quartzose to quartzo-lithic sandstones (Biluoco Formation) and Callovian shoal to outer platform limestones (Suowa Formation). Sandstone petrography coupled with detrital-zircon U-Pb and Hf isotope analysis indicate that the Sewa and Gaaco formations contain intermediate to felsic volcanic detritus and youngest detrital zircons (183-170 Ma) with ɛHf(t) ranging widely from +13 to -25, pointing to continental-arc provenance from igneous rocks with mixed mantle and continental-crust contributions. An arc-trench system thus developed toward the end of the Early Jurassic, with the southern Qiangtang basin representing the fore-arc basin. Above the angular unconformity, the Biluoco Formation documents a change to dominant sedimentary detritus including old detrital zircons (mainly >500 Ma ages in the lower part of the unit) with age spectra similar to those from Paleozoic strata in the central Qiangtang area. A major tectonic event with intense folding and thrusting thus took place in late Bathonian time (166 ± 1 Ma), when the Qiangtang block collided with another microcontinental block possibly the Lhasa block.

Sequence-stratigraphic controls on sandstone diagenesis: An example from the Williams Fork formation, Piceance Basin, Colorado

NASA Astrophysics Data System (ADS)

Aboktef, Adel

This study documents the distribution of diagenetic alterations in Williams Fork fluvial sandstones, assess sequence stratigraphic controls on diagenetic features, and addresses diagenetic impacts on porosity. Petrographic point counts of 220 thin sections from six wells forms the database. The near absence of potassium feldspar and volcanic rock fragments in the lower Williams Fork interval and increasing plagioclase content upward represent changes in sediment provenance rather than stratigraphic variability in diagenesis. The lower Williams Fork sands are from sedimentary sources whereas middle and upper Williams Fork sands include input from magmatic arcs and basement uplifts. Compaction, early and late cementation, dissolution, and replacement by calcite or clay minerals combined to alter Williams Fork sandstones. Infiltration of clays occurred prior to any burial. Chlorite, quartz, non-ferroan calcite, compaction and dissolution features, and kaolinite formed during eo-diagenesis at <70°C. More quartz, compaction and dissolution features, plus albite, illite, mixed-layer illite/smectite, ferroan calcite, and dolomite formed in the meso-diagenetic realm (>70°C). Four of these features show spatial variability with respect to systems tracts. Infiltrated clays are concentrated in lowstand systems tracts (LST) and highstand systems tracts (HST) because accommodation space rose slow or fell during deposition of those sands, which led to prolonged sand body exposure on floodplain and ample opportunities for downward percolation of mud during flood events. Concentration of pseudomatrix (mud intraclasts) in HST and LST deposits resulted from floodplain erosion when base-level fell with decreasing accommodation space. Authigenic chlorite formed in the HST and transgressive systems tracts (TST) of the upper half of the Williams Fork Formation because volcanic clasts are abundant in that interval. Quartz overgrowths are more likely to exceed 7% in TST deposits for

The geometry and lithology of the Cima Sandstone Lentil: a paleoseep-bearing interbed in the Moreno Formation, central California

NASA Astrophysics Data System (ADS)

Wheatley, P. V.; Schwartz, H.

2007-12-01

The Cima Sandstone Lentil outcrops over a relatively small area on the western side of the San Joaquin Valley in central California. Here this unit can be found in the Panoche Hills in the northern portion of the field area and the Tumey Hills in the southern portion of the field area. The Cima Sandstone resides within the 800m Moreno Formation that spans the Maastrichtian to the Danian. The Moreno Formation comprises four members, which are the Dosados Member, the Tierra Loma Member, the Marca Shale Member, and the Dos Palos Shale Member (of which the Cima Sandstone is an interbed). The Cima Sandstone contains numerous large carbonate mounds, concretions, and pavements, indicating paleoseep activity. The Cima Sandstone has never been studied in detail, but recent interest in sandstone injectites as well as interest in paleoseeps has prompted us to examine this interbed more carefully. The Cima is an immature sandstone composed primarily of quartz along with small amounts of micas and feldspars as well as varying amounts of glauconite. These minerals are generally cemented by carbonate but, occasionally, iron oxide cement is present locally. Much variation exists within the Cima Sandstone Lentil and we seek to characterize and understand this variation. One of the most obvious sources of variability is the thickness of the unit itself. The thickness ranges from near 60m in the northern Panoche Hills to only 9m in the Tumey Hills. Induration also varies noticeably, from well cemented in the north, to unconsolidated in the south. Similarly, the sandstone is grain-supported and houses some depositional structures in the northern outcrops but becomes largely matrix-supported and lacking bedding in the southern outcrops. Preliminary data suggests that proximity to carbonate concretions, fluid conduits, and underlying injectites may have some influence over grain size and sorting.

The Chara-Sina dyke swarm in the structure of the Middle Paleozoic Vilyui rift system (Siberian Craton)

NASA Astrophysics Data System (ADS)

Kiselev, A. I.; Konstantinov, K. M.; Yarmolyuk, V. V.; Ivanov, A. V.

2016-11-01

The formation of the Vilyui rift system in the eastern Siberian Craton was finished with breakdown of the continent and formation of its eastern margin. A characteristic feature of this rift system is the radial distribution of dyke swarms of basic rocks. This peculiarity allows us to relate it to the breaking processes above the mantle plume, the center of which was located in the region overlain in the modern structure by the foreland of the Verkhoyan folded-thrust belt. The Chara-Sina dyke swarm is the southern part of a large area of Middle Paleozoic basaltic magmatism in the eastern Siberian Craton. The OIB-like geochemical characteristics of dolerite allow us to suggest that the melting substrate for Middle Paleozoic basaltic magmatism was represented by a relatively homogeneous, mid-depleted mantle of the plume with geochemical parameters similar to those of OIB.

Productivity Contribution of Paleozoic Woodlands to the Formation of Shale-Hosted Massive Sulfide Deposits in the Iberian Pyrite Belt (Tharsis, Spain)

NASA Astrophysics Data System (ADS)

Fernández-Remolar, David C.; Harir, Mourad; Carrizo, Daniel; Schmitt-Kopplin, Philippe; Amils, Ricardo

2018-03-01

The geological materials produced during catastrophic and destructive events are an essential source of paleobiological knowledge. The paleobiological information recorded by such events can be rich in information on the size, diversity, and structure of paleocommunities. In this regard, the geobiological study of late Devonian organic matter sampled in Tharsis (Iberian Pyrite Belt) provided some new insights into a Paleozoic woodland community, which was recorded as massive sulfides and black shale deposits affected by a catastrophic event. Sample analysis using TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometer), and complemented by GC/MS (Gas Chromatrograph/Mass Spectrometer) identified organic compounds showing a very distinct distribution in the rock. While phytochemical compounds occur homogeneously in the sample matrix that is composed of black shale, the microbial-derived organics are more abundant in the sulfide nodules. The cooccurrence of sulfur bacteria compounds and the overwhelming presence of phytochemicals provide support for the hypothesis that the formation of the massive sulfides resulted from a high rate of vegetal debris production and its oxidation through sulfate reduction under suboxic to anoxic conditions. A continuous supply of iron from hydrothermal activity coupled with microbial activity was strictly necessary to produce this massive orebody. A rough estimate of the woodland biomass was made possible by accounting for the microbial sulfur production activity recorded in the metallic sulfide. As a result, the biomass size of the late Devonian woodland community was comparable to modern woodlands like the Amazon or Congo rainforests.

Petrography and geochemistry of the Middle Miocene Gebel El Rusas sandstones, Eastern Desert, Egypt: Implications for provenance and tectonic setting

NASA Astrophysics Data System (ADS)

Zaid, Samir M.

2017-10-01

Petrography and bulk rock geochemistry of the Middle Miocene sandstones of the lower and upper members of Gebel El Rusas Formation along the Egyptian Red Sea Coastal plain, have been investigated to determine the provenance, tectonic setting, and weathering condition of this formation. The Lower Member is formed mainly of sandstones and conglomerates with clay interbeds. The Upper Member is more calcareous and formed mainly of sandstones and limestones with marls and clays intercalations. Petrographically, the Lower Member sandstones are mostly immature and classified as arkoses with an average framework composition of Q_{66}F_{29}R5, and the Upper Member sandstones are partly submature (more quartzose, less feldspathic) and classified as subarkoses with an average framework composition of Q_{80}F_{17}R3. The Gebel El Rusas sandstones are enriched in Sr, Ba, Zr and Rb and depleted in Co and U, as compared to UCC. The chemical index of alteration (CIA) values suggest moderate weathering conditions. The geochemistry results revealed that the Gebel El Rusas sandstones were derived from felsic-granitic source rocks and deposited in a passive margin of a synrift basin. The inferred tectonic setting for Middle Miocene Gebel El Rusas sandstones in the study area is consistent with the regional geology of the Eastern Desert of Egypt during Middle Miocene.

Fractures and stresses in Bone Spring sandstones. Final report

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

Warpinski, N.R.; Sattler, A.R.; Lorenz, J.C.

This project was a collaboration between Sandia National Laboratories and the Harvey E. Yates Company (Heyco), Roswell, NM, conducted under the auspices of Department of Energy`s Oil Recovery Technology Partnership. The project applied Sandia perspectives on the effects of natural fractures, stress, and sedimentology for the stimulation and production of low permeability gas reservoirs to low permeability oil reservoirs, such as those typified by the Bone Spring sandstones of the Delaware Basin, southeast New Mexico. This report details the results and analyses obtained in 1990 from core, logs, stress, and other data taken from three additional development wells. An overallmore » summary gives results from all five wells studied in this project in 1989--1990. Most of the results presented are believed to be new information for the Bone Spring sandstones.« less

Pore-throat sizes in sandstones, siltstones, and shales: Reply

USGS Publications Warehouse

Nelson, Philip H.

2011-01-01

In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

The role of sandstone in the development of an Ozark karst system, south-central Missouri

USGS Publications Warehouse

Orndorff, R.C.; Weary, D.J.; Harrison, R.W.

2006-01-01

Cave, spring, and sinkhole development in the Ozarks of south-central Missouri is placed in a geologic framework through detailed geologic mapping. Geologic mapping shows that initial dissolution and inception of cave development is concentrated just beneath sandstone beds within Upper Cambrian and Lower Ordovician dolostone. Although rocks of the Ozarks have systematic and pervasive vertical joints, the development of karst conduits is controlled by bedding planes and stratigraphic variability. In the Salem Plateau of south-central Missouri, sinkholes occur in the lower part of the Ordovician Roubidoux Formation, where sinkholes are rimmed with and contain sandstone that has collapsed into voids in the underlying Ordovician Gasconade Dolomite. Cave diving by the Ozark Cave Diving Alliance into Alley Spring, a large (average flow 3.7 m3/s) spring along the Jacks Fork in the Ozark National Scenic Riverways, shows that although the spring discharges from the middle part of the Gasconade, the source of water is a cave passage just beneath the Gunter Sandstone Member of the Gasconade Dolomite. Artesian conditions cause the upward movement of groundwater from cavernous dolostone beneath the sandstone aquitards to the large springs. We hypothesize that sandstone, which is largely impermeable due to silica cementation, acts as a confining unit where hydraulic pressure, combined with mixing of water of differing chemistry, increases dissolution in the underlying dolostone beds. ?? 2006 Geological Society of America.

Distribution and character of upper mesozoic subduction complexes along the west coast of North America

USGS Publications Warehouse

Jones, D.L.; Blake, M.C.; Bailey, E.H.; McLaughlin, R.J.

1978-01-01

Structurally complex sequences of sedimentary, volcanic, and intrusive igneous rocks characterize a nearly continuous narrow band along the Pacific coast of North America from Baja California, Mexico to southern Alaska. They occur in two modes: (1) as complexly folded but coherent sequences of graywacke and argillite that locally exhibit blueschist-grade metamorphism, and (2) as melanges containing large blocks of graywacke, chert, volcanic and plutonic rocks, high-grade schist, and limestone in a highly sheared pelitic, cherty, or sandstone matrix. Fossils from the coherent graywacke sequences range in age from late Jurassic to Eocene; fossils from limestone blocks in the melanges range in age from mid-Paleozoic to middle Cretaceous. Fossils from the matrix surrounding the blocks, however, are of Jurassic, Cretaceous, and rarely, Tertiary age, indicating that fossils from the blocks cannot be used to date the time of formation of the melanges. Both the deformation of the graywacke, with accompanying blueschist metamorphism, as well as the formation of the melanges, are believed to be the result of late Mesozoic and early Tertiary subduction. The origin of the melanges, particularly the emplacement of exotic tectonic blocks, is not understood. ?? 1978.

An alternative hypothesis for the mid-Paleozoic Antler orogeny in Nevada

USGS Publications Warehouse

Ketner, Keith B.

2012-01-01

A great volume of Mississippian orogenic deposits supports the concept of a mid-Paleozoic orogeny in Nevada, and the existence and timing of that event are not questioned here. The nature of the orogeny is problematic, however, and new ideas are called for. The cause of the Antler orogeny, long ascribed to plate convergence, is here attributed to left-lateral north-south strike-slip faulting in northwestern Nevada. The stratigraphic evidence originally provided in support of an associated regional thrust fault, the Roberts Mountains thrust, is now known to be invalid, and abundant, detailed map evidence testifies to post-Antler ages of virtually all large folds and thrust faults in the region. The Antler orogeny was not characterized by obduction of the Roberts Mountains allochthon; rocks composing the "allochthon" essentially were deposited in situ. Instead, the orogeny was characterized by appearance of an elongate north-northeast-trending uplift through central Nevada and by two parallel flanking depressions. The eastern depression was the Antler foreland trough, into which sediments flowed from both east and west in the Mississippian. The western depression was the Antler hinterland trough into which sediments also flowed from both east and west during the Mississippian. West of the hinterland trough, across a left-lateral strike-slip fault, an exotic landmass originally attached to the northwestern part of the North American continent was moved southward 1700 km along a strike-slip fault. An array of isolated blocks of shelf carbonate rocks, long thought to be autochthonous exposures in windows of the Roberts Mountains allochthon, is proposed here as an array of gravity-driven slide blocks dislodged from the shelf, probably initiated by the Late Devonian Alamo impact event.

The Collyhurst Sandstone as a secondary storage unit for CCS in the East Irish Sea Basin (UK)

NASA Astrophysics Data System (ADS)

Gamboa, D.; Williams, J. D. O.; Kirk, K.; Gent, C. M. A.; Bentham, M.; Schofield, D. I.

2016-12-01

Carbon Capture and Storage (CCS) is key technology for low-carbon energy and industry. The UK hosts a large CO2 storage potential offshore with an estimated capacity of 78 Gt. The East Irish Sea Basin (EISB) is the key area for CCS in the western UK, with a CO2 storage potential of 1.7 Gt in hydrocarbon fields and in saline aquifers within the Triassic Sherwood Sandstone Formation. However, this theoretical storage capacity does not consider the secondary storage potential in the lower Permian Collyhurst Sandstone Formation. 3D seismic data were used to characterise the Collyhurst Sandstone Formation in the EISB. On the southern basin domain, numerous fault-bound blocks limit the lateral continuity of the sandstone strata, while on the northern domain the sandstones are intersected by less faults. The caprock for the Collyhurst sandstones is variable. The Manchester Marls predominate in the south, transitioning to the St. Bees evaporites towards the north. The evaporites in the EISB cause overburden faults to terminate or detach along Upper Permian strata, limiting the deformation of the underlying reservoir units. Five main storage closures have been identified in the Permian strata. In the southern and central area these are predominantly fault bounded, occurring at depths over 1000m. Despite the higher Collyhurst sandstone thickness in the southern IESB, the dolomitic nature of the caprock constitutes a storage risk in this area. Closures in the northern area are deeper (around 2000-2500m) and wider, reaching areas of 34Km2, and are overlain by evaporitic caprocks. The larger Collyhurst closures to the north underlie large Triassic fields with high storage potential. The spatial overlap favours storage plans including secondary storage units in the EISB. The results of this work also expand the understanding of prospective areas for CO2 sequestration in the East Irish Sea Basin in locations where the primary Sherwood Sandstone Formation is either too shallow

Sample-Collection Drill Hole on Martian Sandstone Target Windjana

NASA Image and Video Library

2014-05-06

This image from the Navigation Camera Navcam on NASA Curiosity Mars rover shows two holes at top center drilled into a sandstone target called Windjana. The farther hole, with larger pile of tailings around it, is a full-depth sampling hole.

Diagenesis and porosity evolution of tight sand reservoirs in Carboniferous Benxi Formation, Southeast Ordos Basin

NASA Astrophysics Data System (ADS)

Hu, Peng; Yu, Xinghe; Shan, Xin; Su, Dongxu; Wang, Jiao; Li, Yalong; Shi, Xin; Xu, Liqiang

2016-04-01

The Ordos Basin, situated in west-central China, is one of the oldest and most important fossil-fuel energy base, which contains large reserves of coal, oil and natural gas. The Upper Palaeozoic strata are widely distributed with rich gas-bearing and large natural gas resources, whose potential is tremendous. Recent years have witnessed a great tight gas exploration improvement of the Upper Paleozoic in Southeastern Ordos basin. The Carboniferous Benxi Formation, mainly buried more than 2,500m, is the key target strata for hydrocarbon exploration, which was deposited in a barrier island and tidal flat environment. The sandy bars and flats are the favorable sedimentary microfacies. With an integrated approach of thin-section petrophysics, constant velocity mercury injection test, scanning electron microscopy and X-ray diffractometry, diagenesis and porosity evolution of tight sand reservoirs of Benxi Formation were analyzed in detail. The result shows that the main lithology of sandstone in this area is dominated by moderately to well sorted quartz sandstone. The average porosity and permeability is 4.72% and 1.22mD. The reservoirs of Benxi Formation holds a variety of pore types and the pore throats, with obvious heterogeneity and poor connection. Based on the capillary pressure curve morphological characteristics and parameters, combined with thin section and phycical property data, the reservoir pore structure of Benxi Formation can be divided into 4 types, including mid pore mid throat type(I), mid pore fine throat type(II), small pore fine throat type(III) and micro pro micro throat type(Ⅳ). The reservoirs primarily fall in B-subsate of middle diagenesis and late diagenesis, which mainly undergo compaction, cmentation, dissolution and fracturing process. Employing the empirical formula of different sorting for unconsolideated sandstone porosity, the initial sandstone porosity is 38.32% on average. Quantitative evaluation of the increase and decrease of

Proposed moduli of dry rock and their application to predicting elastic velocities of sandstones

USGS Publications Warehouse

Lee, Myung W.

2005-01-01

Velocities of water-saturated isotropic sandstones under low frequency can be modeled using the Biot-Gassmann theory if the moduli of dry rocks are known. On the basis of effective medium theory by Kuster and Toksoz, bulk and shear moduli of dry sandstone are proposed. These moduli are related to each other through a consolidation parameter and provide a new way to calculate elastic velocities. Because this parameter depends on differential pressure and the degree of consolidation, the proposed moduli can be used to calculate elastic velocities of sedimentary rocks under different in-place conditions by varying the consolidation parameter. This theory predicts that the ratio of P-wave to S-wave velocity (Vp/Vs) of a dry rock decreases as differential pressure increases and porosity decreases. This pattern of behavior is similar to that of water-saturated sedimentary rocks. If microcracks are present in sandstones, the velocity ratio usually increases as differential pressure increases. This implies that this theory is optimal for sandstones having intergranular porosities. Even though the accurate behavior of the consolidation parameter with respect to differential pressure or the degree of consolidation is not known, this theory presents a new way to predict S-wave velocity from P-wave velocity and porosity and to calculate elastic velocities of gas-hydrate-bearing sediments. For given properties of sandstones such as bulk and shear moduli of matrix, only the consolidation parameter affects velocities, and this parameter can be estimated directly from the measurements; thus, the prediction of S-wave velocity is accurate, reflecting in-place conditions.

Geology of the Harpers Ferry Quadrangle, Virginia, Maryland, and West Virginia

USGS Publications Warehouse

Southworth, Scott; Brezinski, David K.

1996-01-01

The Harpers Ferry quadrangle covers a portion of the northeast-plunging Blue Ridge-South Mountain anticlinorium, a west-verging allochthonous fold complex of the late Paleozoic Alleghanian orogeny. The core of the anticlinorium consists of high-grade paragneisses and granitic gneisses that are related to the Grenville orogeny. These rocks are intruded by Late Proterozoic metadiabase and metarhyolite dikes and are unconformably overlain by Late Proterozoic metasedimentary rocks of the Swift Run Formation and metavolcanic rocks of the Catoctin Formation, which accumulated during continental rifting of Laurentia (native North America) that resulted in the opening of the Iapetus Ocean. Lower Cambrian metasedimentary rocks of the Loudoun, Weverton, Harpers, and Antietam Formations and carbonate rocks of the Tomstown Formation were deposited in the rift-to-drift transition as the early Paleozoic passive continental margin evolved. The Short Hill fault is an early Paleozoic normal fault that was contractionally reactivated as a thrust fault and folded in the late Paleozoic. The Keedysville detachment is a folded thrust fault at the contact of the Antietam and Tomstown Formations. Late Paleozoic shear zones and thrust faults are common. These rocks were deformed and metamorphosed to greenschist-facies during the formation of the anticlinorium. The Alleghanian deformation was accompanied by a main fold phase and a regional penetrative axial plane cleavage, which was followed by a minor fold phase with crenulation cleavage. Early Jurassic diabase dikes transected the anticlinorium during Mesozoic continental rifting that resulted in the opening of the Atlantic Ocean. Cenozoic deposits that overlie the bedrock include bedrock landslides, terraces, colluvium, and alluvium.

Alteration in the Madera Limestone and Sandia Formation from core hole VC-1, Valles caldera, New Mexico

USGS Publications Warehouse

Keith, T.E.C.

1988-01-01

Core hole VC-1 penetrated the southwestern ring fracture zone of the 1.1 Ma Valles caldera and at a depth of 333 m intersected the top of the Paleozoic section including the Abo Formation, Madera Limestone, and Sandia Formation, reaching a total depth of 856 m. The Paleozoic rocks, which consist of thin-bedded limestone, siltstone, mudstone, sandstone, and local conglomerate, are overlain by volcanic rocks of the caldera moat that are less than 0.6 Ma. Diagenetic and at least three hydrothermal alteration stages were identified in the Madera Limestone and Sandia Formation. Diagenetic clay alteration was pervasive throughout the sedimentary rocks. Volcanic activity at 16.5 Ma and continuing through the formation of the Valles caldera resulted in high thermal gradients, which caused recrystallization of diagenetic clay minerals. Interstratified smectite-illite is the most diagnostic clay mineral throughout the section; structurally, the illite component in the ordered interstratified illite-smectite changes gradationally from 70% at the top of the Madera Limestone to 95% at the base of the section in the Sandia Formation. Pyrite that occurs as small clots and lenses as well as finely disseminated is interpreted as being of diagenetic origin, especially in organic-rich beds. Low permeability of much of the paleozoic section precluded the deposition of hydrothermal minerals except in fractures and intergranular space in some of the more permeable sandstone and brecciated horizons. Three stages of hydrothermal mineral deposition are defined. -from Author

Sandstone copper assessment of the Teniz Basin, Kazakhstan: Chapter R in Global mineral resource assessment

USGS Publications Warehouse

Cossette, Pamela M.; Bookstrom, Arthur A.; Hayes, Timothy S.; Robinson, Gilpin R.; Wallis, John C.; Zientek, Michael L.

2014-01-01

A quantitative mineral resource assessment has been completed that (1) delineates one 49,714 km2 tract permissive for undiscovered, sandstone subtype, sediment-hosted stratabound copper deposits, and (2) provides probabilistic estimates of numbers of undiscovered deposits and probable amounts of copper resource contained in those deposits. The permissive tract delineated in this assessment encompasses no previously known sandstone subtype, sediment-hosted stratabound copper deposits. However, this assessment estimates (with 30 percent probability) that a mean of nine undiscovered sandstone subtype copper deposits may be present in the Teniz Basin and could contain a mean total of 8.9 million metric tons of copper and 7,500 metric tons of silver.

Use of seasonal trend decomposition to understand groundwater behaviour in the Permo-Triassic Sandstone aquifer, Eden Valley, UK

NASA Astrophysics Data System (ADS)

Lafare, Antoine E. A.; Peach, Denis W.; Hughes, Andrew G.

2016-02-01

The daily groundwater level (GWL) response in the Permo-Triassic Sandstone aquifers in the Eden Valley, England (UK), has been studied using the seasonal trend decomposition by LOESS (STL) technique. The hydrographs from 18 boreholes in the Permo-Triassic Sandstone were decomposed into three components: seasonality, general trend and remainder. The decomposition was analysed first visually, then using tools involving a variance ratio, time-series hierarchical clustering and correlation analysis. Differences and similarities in decomposition pattern were explained using the physical and hydrogeological information associated with each borehole. The Penrith Sandstone exhibits vertical and horizontal heterogeneity, whereas the more homogeneous St Bees Sandstone groundwater hydrographs characterize a well-identified seasonality; however, exceptions can be identified. A stronger trend component is obtained in the silicified parts of the northern Penrith Sandstone, while the southern Penrith, containing Brockram (breccias) Formation, shows a greater relative variability of the seasonal component. Other boreholes drilled as shallow/deep pairs show differences in responses, revealing the potential vertical heterogeneities within the Penrith Sandstone. The differences in bedrock characteristics between and within the Penrith and St Bees Sandstone formations appear to influence the GWL response. The de-seasonalized and de-trended GWL time series were then used to characterize the response, for example in terms of memory effect (autocorrelation analysis). By applying the STL method, it is possible to analyse GWL hydrographs leading to better conceptual understanding of the groundwater flow. Thus, variation in groundwater response can be used to gain insight into the aquifer physical properties and understand differences in groundwater behaviour.

The first direct evidence of a Late Devonian coelacanth fish feeding on conodont animals

NASA Astrophysics Data System (ADS)

Zatoń, Michał; Broda, Krzysztof; Qvarnström, Martin; Niedźwiedzki, Grzegorz; Ahlberg, Per Erik

2017-04-01

We describe the first known occurrence of a Devonian coelacanth specimen from the lower Famennian of the Holy Cross Mountains, Poland, with a conodont element preserved in its digestive tract. A small spiral and phosphatic coprolite (fossil excrement) containing numerous conodont elements and other unrecognized remains was also found in the same deposits. The coprolite is tentatively attributed to the coelacanth. Although it is unclear whether the Late Devonian coelacanth from Poland was an active predator or a scavenger, these finds provide the first direct evidence of feeding on conodont animals by early coelacanth fish, and one of the few evidences of feeding on these animals known to date. It also expands our knowledge about the diet and trophic relations between the Paleozoic marine animals in general.

Experimental Study of Cement - Sandstone/Shale - Brine - CO2 Interactions

PubMed Central

2011-01-01

Background Reactive-transport simulation is a tool that is being used to estimate long-term trapping of CO2, and wellbore and cap rock integrity for geologic CO2 storage. We reacted end member components of a heterolithic sandstone and shale unit that forms the upper section of the In Salah Gas Project carbon storage reservoir in Krechba, Algeria with supercritical CO2, brine, and with/without cement at reservoir conditions to develop experimentally constrained geochemical models for use in reactive transport simulations. Results We observe marked changes in solution composition when CO2 reacted with cement, sandstone, and shale components at reservoir conditions. The geochemical model for the reaction of sandstone and shale with CO2 and brine is a simple one in which albite, chlorite, illite and carbonate minerals partially dissolve and boehmite, smectite, and amorphous silica precipitate. The geochemical model for the wellbore environment is also fairly simple, in which alkaline cements and rock react with CO2-rich brines to form an Fe containing calcite, amorphous silica, smectite and boehmite or amorphous Al(OH)3. Conclusions Our research shows that relatively simple geochemical models can describe the dominant reactions that are likely to occur when CO2 is stored in deep saline aquifers sealed with overlying shale cap rocks, as well as the dominant reactions for cement carbonation at the wellbore interface. PMID:22078161

Lattice strain measurements on sandstones under load using neutron diffraction

NASA Astrophysics Data System (ADS)

Frischbutter, A.; Neov, D.; Scheffzük, Ch.; Vrána, M.; Walther, K.

2000-11-01

Neutron diffraction methods (both time-of-flight- and angle-dispersive diffraction) are applied to intracrystalline strain measurements on geological samples undergoing uniaxial increasing compressional load. The experiments were carried out on Cretaceous sandstones from the Elbezone (East Germany), consisting of >95% quartz which are bedded but without crystallographic preferred orientation of quartz. From the stress-strain relation the Young's modulus for our quartz sample was determined to be (72.2±2.9) GPa using results of the neutron time-of-flight method. The influence of different kinds of bedding in sandstones (laminated and convolute bedding) could be determined. We observed differences of factor 2 (convolute bedding) and 3 (laminated bedding) for the elastic stiffness, determined with angle dispersive neutron diffraction (crystallographic strain) and with strain gauges (mechanical strain). The data indicate which geological conditions may influence the stress-strain behaviour of geological materials. The influence of bedding on the stress-strain behaviour of a laminated bedded sandstone was indicated by direct residual stress measurements using neutron time-of-flight diffraction. The measurements were carried out six days after unloading the sample. Residual strain was measured for three positions from the centre to the periphery and within two radial directions of the cylinder. We observed that residual strain changes from extension to compression in a different manner for two perpendicular directions of the bedding plane.

Redescription of Bellerophon asiaticus Wirth (Early Triassic: Gastropoda) from China, and a survey of Triassic Bellerophontacea.

USGS Publications Warehouse

Yochelson, E.Y.; Yin, Hongfu

1985-01-01

The bilaterally symmetrical gastropod Bellerophon asiaticus Wirth is redescribed from specimens collected in Guizhou Province, PRC. The species is reassigned to Retispira, a common late Paleozoic taxon. Retispira is another example of a Paleozoic gastropod genus that crossed the era boundary. Associated pelecypods that date these Guizhou occurrences as Early Triassic are well known species in PRC and are illustrated. Both Bellerophon and Euphemites probably occur in the Early Triassic, though the quality of illustrations leaves some uncertainty; the existence of Stachella in the Triassic is more problematic. There was no dramatic reduction of the Bellerophontacea from their abundance and diversity in the Permian. It may be a general phenomenon that most late Paleozoic family-level and many generic-level taxa of gastropods were unaffected by the late Permian 'crisis'. from Authors

Nivelstein sandstone, weakly lithified pure silica sands from the Dutch-German border area, intermittently used in architecture for two millennia

NASA Astrophysics Data System (ADS)

Nijland, Timo G.; Wim Dubelaar, C.

2017-04-01

The current paper provides a concise overview of the geological setting of the Nivelstein sandstone in broad sense, its petrographic and physical characteristics, and its use as natural stone. Miocene pure silica sands occur around Heerlen in the southeastern part of the Dutch province of Limburg and Herzogenrath in adjacent Germany, as well as in the Belgian province of Limburg near Opgrimbie. In Dutch Limburg and in Germany are three large active exploitations, quarrying the sands for industrial purposes. On top of the unconsolidated sands in the Herzogenrath quarry, lithified banks of sandstone occur, known as Nivelstein (or more rarely Herzogenrath) sandstone. This sandstone has been used as dimension stone and ornamental stone since Roman times. In the 11th century the quarry was reopened and after a long period of disuse sandstone blocks were again quarried in the second half of the 19th century. The lithification of the Nivelstein sandstone usually is very weak, with grain to grain contacts and some newly formed quartz rims only. The clay content is extremely low and is restricted to tiny booklets of kaolinite. Despite the weak cementation the Nivelstein sandstone has proved to be very time-resistant building stone that forms a major element in the stone cultural heritage of the Dutch- German border area.

Integrated interpretation of C-8 and G-61 sandstones at Badak and Nilam fields in Sanga-Sanga block of east Kalimantan, Indonesia

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

Ade, W.C.; Suwarlan, W.

1989-03-01

Huffco's Badak and Nilam fields are giant gas fields that together currently produce more than 1.0 bcf of gas per day from sandstones within the Miocene Balikpapan beds. The reservoir sandstones were deposited within a thick regressive deltaic sequence that includes coals, shales, and occasional limestones. Wells typically encounter multiple stacked pay sandstones at depths ranging from about 5500 ft to more than 13,000 ft. Individual sandstone thicknesses can vary from several feet to more than 20 ft. Abrupt lateral stratigraphic variations in sandstone thickness are the rule rather than the exception. Sandstone reservoir interpretations are based on an integratedmore » approach by incorporating the study of well logs, cores, seismic sections, normal moveout-corrected gathers, amplitude variations with offset (AVO) graphs, and pressure and reservoir performance data.« less

CHARACTERIZATION OF SANDSTONE RESERVOIRS FOR ENHANCED OIL RECOVERY: THE PERMIAN UPPER MINNELUSA FORMATION, POWDER RIVER BASIN, WYOMING.

USGS Publications Warehouse

Schenk, C.J.; Schmoker, J.W.; Scheffler, J.M.

1986-01-01

Upper Minnelusa sandstones form a complex group of reservoirs because of variations in regional setting, sedimentology, and diagenetic alteration. Structural lineaments separate the reservoirs into northern and southern zones. Production in the north is from a single pay sand, and in the south from multi-pay sands due to differential erosion on top of the Upper Minnelusa. The intercalation of eolian dune, interdune, and sabkha sandstones with marine sandstones, carbonates, and anhydrites results in significant reservoir heterogeneity. Diagenetic alterations further enhance heterogeneity, because the degree of cementation and dissolution is partly facies-related.

Paleozoic sedimentary rocks in the Red Dog Zn-Pb-Ag district and vicinity, western Brooks Range, Alaska: provenance, deposition, and metallogenic significance

USGS Publications Warehouse

Slack, John F.; Dumoulin, Julie A.; Schmidt, J.M.; Young, L.E.; Rombach, Cameron

2004-01-01

The distribution and composition of Paleozoic strata in the western Brooks Range may have played a fundamental role in Zn-Pb mineralization of the Red Dog district. In our model, deposition and early lithification of biogenic chert and bedded siliceous rocks in the upper part of the Kuna Formation served as a regional hydrologic seal, acting as a cap rock to heat and hydrothermal fluids during Late Mississippian base-metal mineralization. Equally important was the iron-poor composition of black shales of the Kuna Formation (i.e., low Fe/Ti ratios), which limited synsedimentary pyrite formation in precursor sediments, resulting in significant H2S production in pore waters through the interaction of aqueous sulfate with abundant organic matter. This H2S may have been critical to the subsurface deposition of the huge quantities of Zn and Pb in the district. On the basis of this model, we propose that low Fe/Ti and S/C ratios in black shale sequences are potential basin-scale exploration guides for giant sediment-hosted, stratiform Zn-Pb-Ag deposits.

Hydrothermal zebra dolomite in the Great Basin, Nevada--attributes and relation to Paleozoic stratigraphy, tectonics, and ore deposits

USGS Publications Warehouse

Diehl, S.F.; Hofstra, A.H.; Koenig, A.E.; Emsbo, P.; Christiansen, W.; Johnson, Chad

2010-01-01

In other parts of the world, previous workers have shown that sparry dolomite in carbonate rocks may be produced by the generation and movement of hot basinal brines in response to arid paleoclimates and tectonism, and that some of these brines served as the transport medium for metals fixed in Mississippi Valley-type (MVT) and sedimentary exhalative (Sedex) deposits of Zn, Pb, Ag, Au, or barite. Numerous occurrences of hydrothermal zebra dolomite (HZD), comprised of alternating layers of dark replacement and light void-filling sparry or saddle dolomite, are present in Paleozoic platform and slope carbonate rocks on the eastern side of the Great Basin physiographic province. Locally, it is associated with mineral deposits of barite, Ag-Pb-Zn, and Au. In this paper the spatial distribution of HZD occurrences, their stratigraphic position, morphological characteristics, textures and zoning, and chemical and stable isotopic compositions were determined to improve understanding of their age, origin, and relation to dolostone, ore deposits, and the tectonic evolution of the Great Basin. In northern and central Nevada, HZD is coeval and cogenetic with Late Devonian and Early Mississippian Sedex Au, Zn, and barite deposits and may be related to Late Ordovician Sedex barite deposits. In southern Nevada and southwest California, it is cogenetic with small MVT Ag-Pb-Zn deposits in rocks as young as Early Mississippian. Over Paleozoic time, the Great Basin was at equatorial paleolatitudes with episodes of arid paleoclimates. Several occurrences of HZD are crosscut by Mesozoic or Cenozoic intrusions, and some host younger pluton-related polymetallic replacement and Carlin-type gold deposits. The distribution of HZD in space (carbonate platform, margin, and slope) and stratigraphy (Late Neoproterozoic Ediacaran-Mississippian) roughly parallels that of dolostone and both are prevalent in Devonian strata. Stratabound HZD is best developed in Ediacaran and Cambrian units, whereas

Giant weathering pits in the Entrada Sandstone, southeastern Utah: Preliminary findings

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

Netoff, D.I.; Shroba, R.R.

Giant weathering pits formed in outcrops of the lower Entrada Sandstone slickrock of Jurassic age are present in two areas in the Glen Canyon region of arid southeastern Utah. The pits are far larger than any previously described in the geologic literature. The pits near Cookie Jar Butte are commonly cylindrical, typically have low width-to-depth ratios (1.5--3.6), and have a depth of closure of as much as 18 m. There are no obvious lithologic or structural controls that determine their shape or location. Many of the pits at Rock Creek Bay are elongate; several of them have long axes inmore » excess of 53 m, and the longest one is 74 m. Many of the pit walls are breached at the top, and the depth of closure is generally less than 6 m. The shapes of these pits are influenced by point orientation and pit coalescence. Thin-section analyses of near-surface sandstone cores taken near Cookie Jar Butte from pit walls, floors, and rims reveal no significant diagenetic alteration of the fine-grained to very fine frained quartzose sandstone (quartz arenite). Quartz grains appear fresh, and feldspar grains are only slightly weathered. The cement between the grains is mostly CaCO[sub 3]. In several of the pits in both areas sandy sediment veneers the bedrock floor. This sediment is similar in character to the adjacent sandstone and is probably locally derived. Possible origins of the giant pits include various physical, chemical, and biological weathering processes that initiate pit development, followed by excavation by plunge-pool action, wind deflation, dissolution, and piping. Preliminary field and laboratory data do not clearly identify and single process of group of processes that account for pit development.« less

Simulation of forced convection in non-Newtonian fluid through sandstones

NASA Astrophysics Data System (ADS)

Gokhale, M. Y.; Fernandes, Ignatius

2017-11-01

Numerical simulation is carried out to study forced convection in non-Newtonian fluids flowing through sandstones. Simulation is carried out using lattice Boltzmann method (LBM) for both shear-thinning and shear-thickening, by varying the power law index from 0.5 to 1.5 in Carreau-Yasuda model. Parameters involved in LBM and Carreau model are identified to achieve numerical convergence. Permeability and porosity are varied in the range of 10-10-10-6 and 0.1-0.7, respectively, to match actual geometrical properties of sandstone. Numerical technology is validated by establishing Darcy's law by plotting the graph between velocity and pressure gradient. Consequently, investigation is carried out to study the influence of material properties of porous media on flow properties such as velocity profiles, temperature profiles, and Nusselt number.

Is there a basin-centered gas accumulation in Cotton Valley Group Sandstones, Gulf Coast Basin, U.S.A.?

USGS Publications Warehouse

Bartberger, Charles E.; Dyman, Thaddeus S.; Condon, Steven M.

2002-01-01

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is reevaluating the resource potential of selected domestic basin-centered gas accumulations. Basin-centered gas accumulations are characterized by presence of gas in extensive low-permeability (tight) reservoirs in which conventional seals and trapping mechanisms are absent, abnormally high or low reservoir pressures exist, and gas-water contacts are absent. In 1995, the USGS assessed one basin-centered gas play and two conventional plays within the trend of Jurassic and Cretaceous Cotton Valley Group fl uvial-deltaic and barrierisland/ strandplain sandstones across the onshore northern Gulf of Mexico Basin. Detailed evaluation of geologic and production data provides new insights into these Cotton Valley plays. Two Cotton Valley sandstone trends are identifi ed based on reservoir properties and gas-production characteristics. Transgressive blanket sandstones across northern Louisiana have relatively high porosity and permeability and do not require fracture stimulation to produce gas at commercial rates. South of this trend, and extending westward into eastern Texas, massive sandstones of the Cotton Valley trend exhibit low porosity and permeability and require fracture stimulation. The high permeability of Cotton Valley blanket sandstones is not conducive to the presence of basin-centered gas, but lowpermeability massive sandstones provide the type of reservoir in which basin-centered gas accumulations commonly occur. Data on source rocks, including burial and thermal history, are consistent with the interpretation of potential basincentered gas within Cotton Valley sandstones. However, pressure gradients throughout most of the blanket- and massivesandstone trends are normal or nearly normal, which is not characteristic of basin-centered gas accumulations. The presence of gas-water contacts in at least seven fi elds across the blanket-sandstone trend together with relatively

Elemental Gains/Losses Associated with Alteration Fractures in an Eolian Sandstone, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Yen, A. S.; Gellert, R.; Sutter, B.; Berger, J. A.; Thompson, L. M.; Schmidt, M. E.; Morris, R. V.; Treiman, A. H.

2016-01-01

The Mars Science Laboratory rover Curiosity has traversed up section through approximately 100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation unconformably overlies a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Unaltered Stimson sandstone has a basaltic composition similar to the average Mars crustal composition, but is more variable and ranges to lower K and higher Al. Fluids passing through alteration "halos" adjacent to fractures have altered the chemistry and mineralogy of the sandstone. Elemental mass gains and losses in the alteration halos were quantified using immobile element concentrations, i.e., Ti (taus). Alteration halos have elemental gains in Si, Ca, S, and P and large losses in Al, Fe, Mn, Mg, Na, K, Ni, and Zn. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes. The igneous phases were less abundant in the altered sandstone with a lower pyroxene/plagioclase feldspar. Large elemental losses suggest acidic fluids initially removed these elements (Al mobile under acid conditions). Enrichments in Si, Ca, and S suggest secondary fluids (possibly alkaline) passed through these fractures leaving behind X-ray amorphous Si and Ca-sulfates. The mechanism for the large elemental gains in P is unclear. The geochemistry and mineralogy of the altered sandstone suggests a complicated diagenetic history with multiple episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

Lattice Boltzmann Simulation of Seismic Mobilization of Residual Oil in Sandstone

NASA Astrophysics Data System (ADS)

Guo, R.; Jiang, F.; Deng, W.

2017-12-01

Seismic stimulation is a promising technology for enhanced oil recovery. However, current mechanism studies are mainly in the single constricted tubes or idealized porous media, and no study has been conducted in real reservoir porous media. We have developed a numerical simulation which uses the lattice Boltzmann method to directly calculate the characteristics of residual oil clusters to quantify seismic mobilization of residual oil in real Berea sandstone in a scale of 400μm x 400μm x 400μm. The residual oil clusters will be firstly obtained by applying the water flooding scheme to the oil-saturated sandstone. Then, we will apply the seismic stimulation to the sandstone by converting the seismic effect to oscillatory inertial force and add to the pore fluids. This oscillatory inertial force causes the mobilization of residual oil by overcoming the capillary force. The response of water and oil to the seismic stimulation will be observed in our simulations. Two seismic oil mobilization mechanisms will be investigated: (1) the passive response of residual oil clusters to the seismic stimulation, and (2) the resonance of oil clusters subject to low frequency seismic stimulation. We will then discuss which mechanism should be the dominant mechanism for the seismic stimulation oil recovery for practical applications.

Diagenesis and reservoir quality of the Lower Cretaceous Quantou Formation tight sandstones in the southern Songliao Basin, China

NASA Astrophysics Data System (ADS)

Xi, Kelai; Cao, Yingchang; Jahren, Jens; Zhu, Rukai; Bjørlykke, Knut; Haile, Beyene Girma; Zheng, Lijing; Hellevang, Helge

2015-12-01

The Lower Cretaceous Quantou Formation in the southern Songliao Basin is the typical tight oil sandstone in China. For effective exploration, appraisal and production from such a tight oil sandstone, the diagenesis and reservoir quality must be thoroughly studied first. The tight oil sandstone has been examined by a variety of methods, including core and thin section observation, XRD, SEM, CL, fluorescence, electron probing analysis, fluid inclusion and isotope testing and quantitative determination of reservoir properties. The sandstones are mostly lithic arkoses and feldspathic litharenites with fine to medium grain size and moderate to good sorting. The sandstones are dominated by feldspar, quartz, and volcanic rock fragments showing various stages of disintegration. The reservoir properties are quite poor, with low porosity (average 8.54%) and permeability (average 0.493 mD), small pore-throat radius (average 0.206 μm) and high displacement pressure (mostly higher than 1 MPa). The tight sandstone reservoirs have undergone significant diagenetic alterations such as compaction, feldspar dissolution, quartz cementation, carbonate cementation (mainly ferrocalcite and ankerite) and clay mineral alteration. As to the onset time, the oil emplacement was prior to the carbonate cementation but posterior to the quartz cementation and feldspar dissolution. The smectite to illite reaction and pressure solution at stylolites provide a most important silica sources for quartz cementation. Carbonate cements increase towards interbedded mudstones. Mechanical compaction has played a more important role than cementation in destroying the reservoir quality of the K1q4 sandstone reservoirs. Mixed-layer illite/smectite and illite reduced the porosity and permeability significantly, while chlorite preserved the porosity and permeability since it tends to be oil wet so that later carbonate cementation can be inhibited to some extent. It is likely that the oil emplacement occurred

Depositional environments and sand body morphologies of the muddy sandstones at Kitty Field, Powder River Basin, Wyoming

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

Larberg, G.M.B.

1980-01-01

Lower Cretaceous muddy sandstones form a stratigraphic trap at Kitty Field, Campbell County, Wyoming. Porosity and permeability are generally low, but the best reservoir develop maximum effective porosity of 17% and maximum permeability of 442 md. Reservoirs sandstones average less than 15 ft and rarely exceed 30 ft in thickness. Ultimate recovery from the field is estimated at 23 million bbl. Based on electric log character, 4 easily recognizable zones within the muddy interval at Kitty were numbered one through 4 in slabbed cores and petrographic analyses of selected core samples, suggest that sandstones in the second, third, and fourthmore » muddy zones were deposited as part of a sequence associated with the overall transgression of the lower Cretaceous sea. Fourth zone sandstones are fluvial in origin, and were deposited in lows on the unconformable surface of the underlying skull creek shale. 18 references.« less

Zeolites in the Miocene Briones Sandstone and related formations of the central Coast Ranges, California

USGS Publications Warehouse

Murata, K.J.; Whiteley, Karen R.

1973-01-01

Authigenic zeolites present in the generally tuffaceous Miocene Briones Sandstone and related formations of the central Coast Ranges of California indicate three stages of diagenetic history: (1) Initial alteration of pyroclastic materials to clinoptilolite (and montmorillonite) that is widely distributed in small amounts throughout the region. (2) Subsequent crystallization of heulandite followed by stilbite in fractures at a few places. (3) Widespread development of laumontite in only the southern part of the region, where the sandstone appears to have been downfolded and faulted to greater depths than elsewhere. Laumontite occurs both as pervasive cement of sandstone and as filling of fractures, and was produced through the reaction of interstitial solutions with other zeolites and with such major constituents of the sandstone as plagioclase, montmorillonite, and calcite at temperatures of 100° C or higher. Mordenite was found at only one locality, closely associated with clinoptilolite and opal. Analcite occurs in diverse settings, and its relation to the other zeolites is obscure.  Sparry calcite and coexisting stilbite, laumontite, or analcite in veins seem to make up nonequilibrium assemblages.

Transport of Organic Contaminants Mobilized from Coal through Sandstone Overlying a Geological Carbon Sequestration Reservoir

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

Zhong, Lirong; Cantrell, Kirk J.; Bacon, Diana H.

2014-02-01

Column experiments were conducted using a wetted sandstone rock installed in a tri-axial core holder to study the flow and transport of organic compounds mobilized by scCO2 under simulated geologic carbon storage (GCS) conditions. The sandstone rock was collected from a formation overlying a deep saline reservoir at a GCS demonstration site. Rock core effluent pressures were set at 0, 500, or 1000 psig and the core temperature was set at 20 or 50°C to simulate the transport to different subsurface depths. The concentrations of the organic compounds in the column effluent and their distribution within the sandstone core weremore » monitored. Results indicate that the mobility though the core sample was much higher for BTEX compounds than for naphthalene. Retention of organic compounds from the vapor phase to the core appeared to be primarily controlled by partitioning from the vapor phase to the aqueous phase. Adsorption to the surfaces of the wetted sandstone was also significant for naphthalene. Reduced temperature and elevated pressure resulted in greater partitioning of the mobilized organic contaminants into the water phase.« less

Soil-landscape development and late Quaternary environmental change in coastal Estremadura, Portugal

NASA Astrophysics Data System (ADS)

Daniels, Michael; Haws, Jonathan; Benedetti, Michael; Bicho, Nuno

2015-04-01

This poster integrates soil-landscape analysis with archaeological survey and paleoenvironmental reconstruction. Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms, and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the distribution and condition of Paleolithic archaeological sites and help understand the record of human settlement in the region. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine (Pinus pinaster) forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. A conceptual model of soil-landscape evolution through the late Quaternary and Holocene results from the integration of soil profile data, proxy paleoenvironmental data, and the partial record of human settled as revealed in the archaeological record.

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

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

A Systems Approach to Identifying Exploration and Development Opportunities in the Illinois Basin: Digital Portifolio of Plays in Underexplored Lower Paleozoic Rocks [Part 1 of 2

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

Seyler, Beverly; Harris, David; Keith, Brian

2008-06-30

This study examined petroleum occurrence in Ordovician, Silurian and Devonian reservoirs in the Illinois Basin. Results from this project show that there is excellent potential for additional discovery of petroleum reservoirs in these formations. Numerous exploration targets and exploration strategies were identified that can be used to increase production from these underexplored strata. Some of the challenges to exploration of deeper strata include the lack of subsurface data, lack of understanding of regional facies changes, lack of understanding the role of diagenetic alteration in developing reservoir porosity and permeability, the shifting of structural closures with depth, overlooking potential producing horizons,more » and under utilization of 3D seismic techniques. This study has shown many areas are prospective for additional discoveries in lower Paleozoic strata in the Illinois Basin. This project implemented a systematic basin analysis approach that is expected to encourage exploration for petroleum in lower Paleozoic rocks of the Illinois Basin. The study has compiled and presented a broad base of information and knowledge needed by independent oil companies to pursue the development of exploration prospects in overlooked, deeper play horizons in the Illinois Basin. Available geologic data relevant for the exploration and development of petroleum reservoirs in the Illinois Basin was analyzed and assimilated into a coherent, easily accessible digital play portfolio. The primary focus of this project was on case studies of existing reservoirs in Devonian, Silurian, and Ordovician strata and the application of knowledge gained to future exploration and development in these underexplored strata of the Illinois Basin. In addition, a review of published reports and exploration in the New Albany Shale Group, a Devonian black shale source rock, in Illinois was completed due to the recent increased interest in Devonian black shales across the United States

Axial and Radial Permeability Evolutions of Compressed Sandstones: End Effects and Shear-band Induced Permeability Anisotropy

NASA Astrophysics Data System (ADS)

Dautriat, Jeremie; Gland, Nicolas; Guelard, Jean; Dimanov, Alexandre; Raphanel, Jean L.

2009-07-01

The influence of hydrostatic and uniaxial stress states on the porosity and permeability of sandstones has been investigated. The experimental procedure uses a special triaxial cell which allows permeability measurements in the axial and radial directions. The core sleeve is equipped with two pressure samplers placed distant from the ends. They provide mid-length axial permeability measure as opposed to the overall permeability measure, which is based on the flow imposed through the pistons of the triaxial cell. The core sleeve is also equipped to perform flows in two directions transverse to the axis of the sample. Two independent measures of axial and complementary radial permeability are thus obtained. Both Fontainebleau sandstone specimens with a porosity of about 5.8% to 8% and low permeability ranging from 2.5 mD to 30 mD and Bentheimer sandstone with a porosity of 24% and a high permeability of 3 D have been tested. The initial axial permeability values obtained by each method are in good agreement for the Fontainebleau sandstone. The Bentheimer sandstone samples present an axial mid-length permeability 1.6 times higher than the overall permeability. A similar discrepancy is also observed in the radial direction, also it relates essentially to the shape of flow lines induced by the radial flow. All the tested samples have shown a higher stress dependency of overall and radial permeability than mid-length permeability. The effect of compaction damage at the pistons/sample and radial ports/sample interfaces is discussed. The relevance of directional permeability measurements during continuous uniaxial compression loadings has been shown on the Bentheimer sandstone until the failure of the sample. We can efficiently measure the influence of brittle failure associated to dilatant regime on the permeability: It tends to increase in the failure propagation direction and to decrease strongly in the transverse direction.

Detrital Record of Phanerozoic Tectonics in Iran: Evidence From U-Pb Zircon Geochronology

NASA Astrophysics Data System (ADS)

Horton, B. K.; Gillis, R. J.; Stockli, D. F.; Hassanzadeh, J.; Axen, G. J.; Grove, M.

2004-12-01

Ion-microprobe U-Pb ages of 91 detrital zircon grains supplement ongoing investigations of the tectonic history of Iran, a critical region bridging the gap between the Alpine and Himalayan orogenic belts. These data improve understanding of the distribution of continental blocks during a complex history of Late Proterozoic (Pan-African) crustal growth, Paleozoic passive-margin sedimentation, early Mesozoic collision with Eurasia, and Cenozoic collision with Arabia. U-Pb analyses of detrital zircon grains from four sandstone samples (two Lower Cambrian, one uppermost Triassic-Lower Jurassic, one Neogene) collected from the Alborz mountains of northern Iran reveal a spectrum of ages ranging from 50 to 2900 Ma. Most analyses yield concordant to moderately discordant ages. The Lower Cambrian Lalun and Barut sandstones yield age distribution peaks at approximately 550-650, 1000, and 2500 Ma, consistent with a Gondwanan source area presently to the south and west in parts of Iran and the Arabian-Nubian shield (Saudi Arabia and northwestern Africa). The uppermost Triassic-Lower Jurassic Shemshak Formation exhibits a broad range of U-Pb ages, including peaks of approximately 200-260, 330, 430, 600, and 1900 Ma, requiring a Eurasian source area presently to the north and east in the Turan plate (Turkmenistan and southwestern Asia). Neogene strata display both the youngest and oldest ages (approximately 50 and 2900 Ma) of any samples, a result of substantial sedimentary recycling of older Phanerozoic cover rocks. Because the youngest zircon ages for three of the four samples are indistinguishable from their stratigraphic (depositional) ages, these data suggest rapid exhumation and help constrain the termination age of Late Proterozoic-Early Cambrian (Pan-African) orogenesis and the timing of the Iran-Eurasia collision.

The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

NASA Astrophysics Data System (ADS)

Atapour, Hadi; Mortazavi, Ali

2018-04-01

The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

Identifying Early Paleozoic tectonic relations in a region affected by post-Taconian transcurrent faulting, an example from the PA-DE Piedmont

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

Alcock, J.; Wagner, M.E.; Srogi, L.A.

1993-03-01

Post-Taconian transcurrent faulting in the Appalachian Piedmont presents a significant problem to workers attempting to reconstruct the Early Paleozoic tectonic history. One solution to the problem is to identify blocks that lie between zones of transcurrent faulting and that retain the Early Paleozoic arrangement of litho-tectonic units. The authors propose that a comparison of metamorphic histories of different units can be used to recognize blocks of this type. The Wilmington Complex (WC) arc terrane, the pre-Taconian Laurentian margin rocks (LM) exposed in basement-cored massifs, and the Wissahickon Group metapelites (WS) that lie between them are three litho-tectonic units in themore » PA-DE Piedmont that comprise a block assembled in the Early Paleozoic. Evidence supporting this interpretation includes: (1) Metamorphic and lithologic differences across the WC-WS contact and detailed geologic mapping of the contact that suggest thrusting of the WC onto the WS; (2) A metamorphic gradient in the WS with highest grade, including spinel-cordierite migmatites, adjacent to the WC indicating that peak metamorphism of the WS resulted from heating by the WC; (3) A metamorphic discontinuity at the WS-LM contact, evidence for emplacement of the WS onto the LM after WS peak metamorphism; (4) A correlation of mineral assemblage in the Cockeysville Marble of the LM with distance from the WS indicating that peak metamorphism of the LM occurred after emplacement of the WS; and (5) Early Paleozoic lower intercept zircon ages for the LM that are interpreted to date Taconian regional metamorphism. Analysis of metamorphism and its timing relative to thrusting suggest that the WS was associated with the WC before the WS was emplaced onto the LM during the Taconian. It follows that these units form a block that has not been significantly disrupted by later transcurrent shear.« less

A condensed middle Cenomanian succession in the Dakota Sandstone (Upper Cretaceous), Sevilleta National Wildlife Refuge, Socorro County, New Mexico

USGS Publications Warehouse

Hook, Stephen C.; Cobban, William A.

2007-01-01

The upper part of the Dakota Sandstone exposed on the Sevilleta National Wildlife Refuge, northern Socorro County, New Mexico, is a condensed, Upper Cretaceous, marine succession spanning the first five middle Cenomanian ammonite zones of the U.S. Western Interior. Farther north in New Mexico these five ammonite zones occur over a stratigraphic interval more than an order of magnitude thicker. The basal part of this marine sequence was deposited in Seboyeta Bay, an elongate east-west embayment into New Mexico that marked the initial transgression of the western shoreline of the Late Cretaceous seaway into New Mexico. The primary mechanism for condensing this section was nearshore, submarine erosion, although nondeposition played a minor role. The ammonite fossils from each zone are generally fragments of internal molds that are corroded on one side, indicating submarine burial, erosion of the prefossilized steinkern, and corrosion on the sea floor. In addition, the base of the condensed succession is marked by a thin bed that contains abundant, white-weathering, spherical to cylindrical phosphate nodules, many of which contain a cylindrical axial cavity of unknown origin. The nodules lie on the bedding surface of the highly burrowed, ridge-forming sandstone near the top of the Dakota and occur in the overlying breccia. The breccia consists of rip-up clasts of sandstone and eroded internal molds of the ammonite Conlinoceras tarrantense, the zonal index for the basal middle Cenomanian. The nodules below the breccia imply a time of erosion followed by nondeposition or sediment bypass during which the phosphatization occurred. The breccia implies a time of submarine erosion, probably storm-related. Remarkably, this condensed succession and the basal part of the overlying Mancos Shale tongue contain one of the most complete middle Cenomanian ammonite sequences in the U.S. Western Interior. Five of the six ammonite zones that characterize the middle Cenomanian of the

Waterborne Superhydrophobic and Superoleophobic Coatings for the Protection of Marble and Sandstone

PubMed Central

Aslanidou, Dimitra; Lampakis, Dimitrios

2018-01-01

Silica nanoparticles were dispersed in an aqueous emulsion of alkoxy silanes and organic fluoropolymer. The dispersion was sprayed onto white marble and sandstone. The deposited composite coatings exhibited (i) superhydrophobicity and superoleophobicity, as evidenced by the high (>150°) static contact angles of water and oil drops as well as (ii) water and oil repellency according to the low (<7°) corresponding tilt contact angles. Apart from marble and sandstone, the coatings with extreme wetting properties were deposited onto concrete, silk, and paper, thus demonstrating the versatility of the method. The siloxane/fluoropolymer product was characterized using Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy and Scanning Electron Microscopy equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDX). Moreover, SEM and FT-IR were used to reveal the surface structures of the composite coatings and their transition from superhydrophobicity to superhydrophilicity which occurred after severe thermal treatment. The composite coatings slightly reduced the breathability of marble and sandstone and had practically no optical effect on the colour of the two stones. Moreover, the coatings offered good protection against water penetration by capillarity. PMID:29642652

Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

USGS Publications Warehouse

McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

2008-01-01

Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

Diagenetic history of the Surma Group sandstones (Miocene) in the Surma Basin, Bangladesh

NASA Astrophysics Data System (ADS)

Rahman, M. Julleh Jalalur; McCann, Tom

2012-02-01

This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of δ 18O values (-10.3‰ to -12.4‰) and a wide range of δ 13C value (+1.4‰ to -23.1‰). The δ 13C VPDB and δ 18O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor

Remote detection of fluid-related diagenetic mineralogical variations in the Wingate Sandstone at different spatial and spectral resolutions

NASA Astrophysics Data System (ADS)

Okyay, Unal; Khan, Shuhab D.

2016-02-01

Well-exposed eolian units of the Jurassic system on the Colorado Plateau including the Wingate Sandstone, show prominent color variations throughout southeastern Utah due to diagenetic changes that include precipitation and/or removal of iron oxide, clay, and carbonate cement. Spatially variable characteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic mineral variability and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability from regional to outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnostic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparison of reflectance spectroscopy with satellite, airborne, and ground-based imaging spectroscopy data provided a method for mapping and evaluating spatial variations of diagenetic minerals. The Feature-oriented Principal Component Selection method was used on Advanced Spaceborne Thermal Emission and Reflection Radiometer data so as to map common mineral groups throughout the broader Wingate Sandstone exposure in the area. The Minimum Noise Fraction and Spectral Angle Mapper methods were applied on airborne HyMap and ground-based hyperspectral imaging data to identify and map mineralogical changes. The satellite and airborne data showed that out of 25.55 km2 total exposure of Wingate Sandstone in Lisbon Valley, unaltered sandstone cover 12.55 km2, and altered sandstone cover 8.90 km2 in the northwest flank and 5.09 km2 in the southern flank of the anticline. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near

Variable post-Paleozoic deformation detected by seismic reflection profiling across the northwestern "prong" of New Madrid seismic zone

USGS Publications Warehouse

McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.; Devera, J.A.; Denny, F.B.; Woolery, E.W.

2003-01-01

High-resolution shallow seismic reflection profiles across the northwesternmost part of the New Madrid seismic zone (NMSZ) and northwestern margin of the Reelfoot rift, near the confluence of the Ohio and Mississippi Rivers in the northern Mississippi embayment, reveal intense structural deformation that apparently took place during the late Paleozoic and/or Mesozoic up to near the end of the Cretaceous Period. The seismic profiles were sited on both sides of the northeast-trending Olmsted fault, defined by varying elevations of the top of Mississippian (locally base of Cretaceous) bedrock. The trend of this fault is close to and parallel with an unusually straight segment of the Ohio River and is approximately on trend with the westernmost of two groups of northeast-aligned epicenters ("prongs") in the NMSZ. Initially suspected on the basis of pre-existing borehole data, the deformation along the fault has been confirmed by four seismic reflection profiles, combined with some new information from drilling. The new data reveal (1) many high-angle normal and reverse faults expressed as narrow grabens and anticlines (suggesting both extensional and compressional regimes) that involved the largest displacements during the late Cretaceous (McNairy); (2) a different style of deformation involving probably more horizontal displacements (i.e., thrusting) that occurred at the end of this phase near the end of McNairy deposition, with some fault offsets of Paleocene and younger units; (3) zones of steeply dipping faults that bound chaotic blocks similar to that observed previously from the nearby Commerce geophysical lineament (CGL); and (4) complex internal deformation stratigraphically restricted to the McNairy, suggestive of major sediment liquefaction or landsliding. Our results thus confirm the prevalence of complex Cretaceous deformations continuing up into Tertiary strata near the northern terminus of the NMSZ. ?? 2003 Elsevier Science B.V. All rights reserved.

The evolution of Phanerozoic seawater - Isotope paleothermometry finds consensus on Early Paleozoic warmth and constant seawater δ18O

NASA Astrophysics Data System (ADS)

Grossman, E. L.; Henkes, G. A.; Passey, B. H.; Shenton, B.; Yancey, T. E.; Perez-Huerta, A.

2015-12-01

Evolution of metazoan life is closely linked to the Phanerozoic evolution of ocean temperatures and chemistry. Oxygen isotopic evidence for early Phanerozoic paleotemperatures has been equivocal, with decreasing δ18O values with age being interpreted as warmer early oceans, decreasing seawater δ18O with age, or increasing diagenetic alteration in older samples. Here we compare an updated compilation of oxygen isotope data for carbonate and phosphate fossils and microfossils (Grossman, 2012, Geol. Time Scale, Elsevier, 195-220) with a compilation of new and existing clumped isotope data. Importantly, these data are curated based on sample preservation with special consideration given to screening techniques, and tectonic and burial history. Burial history is critical in the preservation of carbonate clumped isotope temperatures in particular, which can undergo reordering in the solid state. We use a model derived for reordering kinetics (Henkes et al., 2014, Geochim. Cosmochim. Acta 139:362-382) to screen clumped isotope data for the effects of solid-state burial alteration. With minor but significant exceptions (Late Cretaceous, Early Triassic), average δ18O values (4 m.y. window, 2 m.y. steps) for post-Devonian brachiopods, belemnites, and foraminifera, representing tropical-subtropical surface ocean conditions, yield average isotopic temperatures below 30°C (assuming a seawater δ18O value [ -1‰ VSMOW] of an "ice-free" world). In contrast, Ordovician to Devonian data show sustained temperatures of 35-40°C. Likewise, isotopic paleotemperatures from conodont apatite, known to be resistant to isotopic exchange, follow the same pattern. Clumped isotope data derived from Paleozoic brachiopod shells that experienced minimal burial (< 100 °C) and <1% reordering according to the taxon-specific clumped isotope reordering model yield typical temperatures of 25-30°C for the Carboniferous, and 35-40°C for the Ordovician-Silurian. Inserting clumped temperatures and

The Manciano Sandstone: a shoreface deposit of Miocene basins of the Northern Apennines, Italy

NASA Astrophysics Data System (ADS)

Martini, I. P.; Cascella, A.; Rau, A.

1995-09-01

Well exposed, diamond-line cut, quarry-exposures of the Manciano Sandstone allow a detailed analysis of sandy, fossiliferous, nearshore deposits of the shelf of the Northern Apennines. The Manciano Sandstone is characterized by medium to very coarse, washed, fairly well sorted, lithic sandstone, with thin interlayers of sandy conglomerates. It displays two principal, rhythmically alternating sandy facies: (a) slightly burrowed (mostly Macaronichnus, Ophiomorpha, Skolithos) units, trough cross-bedded, locally showing possible tidal bundles with few whole Scutella (echinoid) shells reworked on foresets, or occasional large-scale (approximately 2 m) planar cross-bedded, bar-accretion units; and (b) slightly finer, darker-coloured reddish-brown sandstone units, heavily bioturbated ( Cruziana-Skolithos) ichnofauna) representing slightly more sheltered settings. Large oysters are present in near-living position in a few thin layers and, more commonly, as reworked, comminuted fragments in sandy layers. Many calcareous pebbles and oyster fragments are bored. Other fossils consist of echinoids ( Scutella), some balanids and reworked foraminifera and bryozoa. The Manciano sands were deposited primarily in a wave-dominated shoreface, containing migrating bars/ridges and affected by wave-induced, possibly tidal-enhanced currents. This tidal influence confirms the opening of the Miocene Apenninic Sea to oceans, both the developing Atlantic Ocean to the west and, through a long, narrow seaway, the Asian portion of the Tethys Sea to the east.

Upper crust beneath the central Illinois basin, United States

USGS Publications Warehouse

McBride, J.H.; Kolata, Dennis R.

1999-01-01

Newly available industry seismic reflection data provide critical information for understanding the structure and origin of the upper crust (0-12 km depth) beneath the central Illinois basin and the seismic-tectonic framework north of the New Madrid seismic zone in the central Mississippi Valley. Mapping of reflector sequences furnishes the first broad three-dimensional perspective of the structure of Precambrian basement beneath the central United States Midcontinent. The highly coherent basement reflectivity is expressed as a synformal wedge of dipping and subhorizontal reflections situated beneath the center of the Illinois basin that thickens and deepens to the northeast (e.g., 0 to ???5.3 km thickness along a 123 km south to north line). The thickening trend of the wedge qualitatively mimics the northward thickening of the Late Cambrian Mt. Simon Sandstone; however, other Paleozoic units in the Illinois basin generally thicken southward into the basin center. The seismic data also reveal an anomalous subsequence defined by a spoon-shaped distribution of disrupted reflections located along the southern margin of the wedge. The boundaries of this subsequence are marked by distinct steeply dipping reflections (possible thrust faults?) that continue or project up to antiformal disruptions of lower Paleozoic marker reflectors, suggesting Paleozoic or possibly later tectonic reactivation of Precambrian structure. The areal extent of the subsequence appears to roughly correspond to an anomalous concentration of larger magnitude upper to middle crustal earthquakes. There are multiple hypotheses for the origin of the Precambrian reflectivity, including basaltic flows or sills interlayered with clastic sediments and/or emplaced within felsic igneous rocks. Such explanations are analogous to nearby Keweenawan rift-related volcanism and sedimentation, which initiated during Proterozoic rifting, and were followed eventually by reverse faulting along the rift margins caused

Evaluation of stratigraphic relations of sandstone-producing reservoirs in upper Council Grove and Chase groups (Permian) in north-central Oklahoma

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

Chaplin, J.R.

1989-08-01

Poor well control and the absence of surface stratigraphic control made previous interpretations of the stratigraphic relations of sandstone-producing reservoirs tenuous. Recent extensive analyses of surface outcrops and well and core data support the contention that the major sandstone-producing reservoirs can be physically correlated with formations in the outcrop section. Sandstone bodies within the upper Council Grove Group include Neva sand and Blackwell sand (Neva Limestone), Hotson-Kisner sand (Eskridge Shale), and the Whitney-Hodges sand. The Whitney-Hodges sand correlates, in part, with the Speiser Shale (Garrison Formation) of the outcrop section. However, previous usage suggested tentative correlations with sandstone bodies stratigraphicallymore » lower in the section. These sands were probably deposited in channels that were, in part, fluvial, tidal, or estuarine. Production from the Chase Group occurs locally within channelform sandstone bodies referred to as the Hoy-Matfield sand. These sands appear to be equivalent, occupying essentially the position of the Kinney Limestone Member (Matfield Shale) of the outcrop section. Detailed core-hole data at and in the vicinity of Kaw Dam, southeastern Kay County, and outcrops along the shoreline of Kaw Lake at Kaw City, Kay County, clearly demonstrate the facies distribution of the Hoy sand. Core-hole data has also delineated additional potential sandstone reservoirs within and near or at the top of the Fort Riley Limestone Member (Barneston Limestone). The Wolfe sand, a producing sandstone locally, occupies a stratigraphic position within the Doyle Shale.« less

Subdivision of the Cambrian-Ordovician Upper Sandstone Aquifer'' in the Fox Cities area, east-central Wisconsin

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

Erikson, K.A.; Smith, G.L.

The informally-named Upper Sandstone Aquifer,'' a lithologically heterogeneous unit, has been subdivided into three thinner hydrostratigraphic units, the Upper Cambrian Jordan Formation (sandstone), the Lower Ordovician Prairie du Chien Group (dolomite), and the Middle Ordovician St. Peter Formation (mostly sandstone). Reevaluation of the Upper Sandstone Aquifer'' in the Fox Cities area (Appleton, Neenah, Menasha) was based on detailed analysis of 125 geologic well logs and 200 well-construction reports. Isopach maps and geologic cross-sections of these units in the Fox Cities area show extreme variations in thickness over short lateral distances. Although the Jordan Formation has a uniform thickness of 13more » m (40 ft), the Prairie du Chien Group varies from 0--88 m (0--275 ft). The St. Peter Formation varies in thickness from 0--108 m (0--335 ft). The Prairie du Chien Group is relatively thin or absent in the Fox Cities area in locations where the overlying St. Peter Formation is relatively thick. St Peter can be further subdivided into Readstown, Tonti, and Glenwood Members. The Readstown Member is a lithologically heterogeneous unit of variable thickness and distribution. The Tonti Member is a poorly cemented, fine-medium quartz arenite with which is lumped the Glenwood Member, a conglomeratic, silty medium-coarse sandstone. Maximum St. Peter thicknesses represent filled paleokarst depressions developed on top of the Prairie du Chien Group, with profound implications for estimates of hydraulic conductivity.« less

Reservoir performance of Late Eocene incised valley fills, Cusiana Field, Llanos Foothills, Eastern Colombia

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

Pulham, A.; Edward, W.; App, J.

1996-12-31

The Cusiana Field is located in the Llanos Foothills of Eastern Colombia. The principal reservoir is the late Eocene Mirador Formation which comprises >50% of reserves. Currently the Mirador reservoir is providing nearly all of the 150,00bopd of production from the Cusiana Field. The Mirador reservoir comprises a stack of incised valley deposits. The fills of the valleys are dominated by quartz arenite sandstones. The average porosity of the valley sandstones is 8% which reflects abundant quartz cement ({approximately}14%) and significant compaction during deep burial ({approximately}20,000feet). Single valleys are up to 70 feet thick and exhibit a distinctive bipartite fillmore » that reflects changing energy conditions during filling. Bases of valleys have the coarsest grain size and have sedimentological and trace fossil evidence for deposition in highly stressed, brackish water environments. The upper parts of the valleys are typically finer grained and were deposited in more saline settings. Despite the low porosity of the Mirador valleys, drill stem tests and production log data show that they have phenomenal performance characteristics. Rates of {ge}10,000bopd are achieved from single valleys. Bases of the valley fills are the key contributors to flow. Integration of detailed core and pore system analysis with the reservoir performance data shows that the permeability fabric of the Mirador can be explained by original depositional architecture and simple loss of primary porosity. Comparison of Cusiana with other quartz-rich sandstones from around the world suggests that it`s low porosity/high performance is predictable.« less

Lower Jurassic Navaho-Aztec-Equivalent Sandstones in southern Arizona and their paleogeographic significance

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

Bilodeau, W.L.; Keith, S.B.

1986-06-01

Thick sequences of Lower Jurassic rhyolitic and andesitic volcanic rocks in several mountain ranges of southern Arizona contain interbedded quartzarenites. Locally up to 250 m thick, these sandstone lenses, composed of well-sorted and well-rounded quartz grains, commonly contain large-scale cross-stratification and are considered to be eolian sand deposits. The eolian sands were blown up against the continental side of the Early Jurassic volcanic arc that trended northwest-southeast across the southwestern margin of the North American continent and/or plate at that time. Paleocurrent data suggest southerly eolian transport of the sands from the Colorado Plateau area. Correlation of these sandstones withmore » the Lower Jurassic Navaho and Aztec Sandstones is indicated by the paleocurrent data as well as radiometric dating of the interbedded volcanics. Eolian sand transport southward across central Arizona in the Early Jurassic indicates that the Mogollon highlands either did not then exist, or were merely low, discontinuous inselbergs on a broad back-arc ramp, more appropriately called the Mogollon slope.« less