Showing papers on "Permian published in 1994"

The Permo–Triassic extinction

Abstract: The end-Permian mass extinction brought the Palaeozoic great experiment in marine life to a close during an interval of intense climatic, tectonic and geochemical change. Improved knowledge of latest Permian faunas, coupled with recent advances in isotopic studies and biostratigraphy, have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction.

A Double Mass Extinction at the End of the Paleozoic Era

Abstract: Three tests based on fossil data indicate that high rates of extinction recorded in the penultimate (Guadalupian) stage of the Paleozoic era are not artifacts of a poor fossil record. Instead, they represent an abrupt mass extinction that was one of the largest to occur in the past half billion years. The final mass extinction of the era, which took place about 5 million years after the Guadalupian event, remains the most severe biotic crisis of all time. Taxonomic losses in the Late Permian were partitioned among the two crises and the intervening interval, however, and the terminal Permian crisis eliminated only about 80 percent of marine species, not 95 or 96 percent as earlier estimates have suggested.

A Review of Selected Triassic to Early Cretaceous Ferns

Abstract: After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the earth moderated. As a result, a considerable number and variety were present and widely distributed during the Jurassic and Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became reduced in variety and greatly restricted in distribution. Some of the Mesozoic ferns are rather primitive and obviously are closely related descendants of Paleozoic taxa. Such ferns are assigned mostly to the Marattiaceae, Guaireaceae, Osmundaceae, and Gleicheniaceae. The majority of the Mesozoic ferns, however, are distinctive and appear to have originated during that era. These fossil ferns generally fit into modern orders and families such as the Matoniaceae or the Dipteridaceae. In some cases, it is difficult to clearly distinguish some of the Mesozoic ferns from living genera.

Uranium‐lead zircon ages from the Median Tectonic Zone, New Zealand

Abstract: The Median Tectonic Zone (MTZ) of New Zealand is a generally north trending belt of Mesozoic subduction‐related I‐type plutonic, volcanic, and sedimentary rocks in South Island and Stewart Island that separates Permian strata of the Eastern Province Brook Street Terrane from lower to mid‐Paleozoic Gondwana margin assemblages of the Western Province. High‐precision isotope dilution U/Pb ages of zircons from 30 rocks are reported. Pre‐digestion leaching of zircon in hydrofluoric acid yielded significantly more concordant residues by removing common Pb and dissolving more soluble high‐U domains that have been more affected by relatively recent Pb loss. The results show that MTZ magmatism ranges in age from at least Early Triassic to Early Cretaceous (247–131 Ma), with a pronounced gap in the Middle Jurassic. Triassic plutons tend to occur on the eastern side of the MTZ, and they intrude volcanic/sedimentary sequences of the MTZ in Nelson and eastern Fiordland. These sequences are in turn intruded by...

Permian-Triassic extinction: Organic δ13C evidence from British Columbia, Canada

Abstract: The Permian-Triassic (P-T) extinction is documented geochemically in a marine sequence deposited in a basinal setting at Williston Lake, northeastern British Columbia, by using elemental and isotopic organic geochemical data from well-preserved sedimentary rocks. The δ 13 C values of kerogens in the rocks exhibit a sudden shift at the P-T boundary from latest Permian values of -29‰ ± 1‰ (PDB) to a minimum of -32.6‰ 2 m above the P-T boundary and then back to the Permian value 4 m above the P-T boundary. After considering various factors, we conclude that reduced surface-water primary productivity following the P-T mass extinction is largely responsible for the observed δ 13 C shift. The abruptness of the δ 13 C shift in a sequence of continuous deposition argues that the strong pulse of extinction at the P-T boundary was sudden rather than gradual. Marine primary productivity did not recover until at least 50 to 100 ka after the time of the P-T boundary, so a higher atmospheric p CO 2 in the earliest Triassic may have resulted from buildup of dissolved CO 2 owing to reduced photosynthetic carbon demand in the surface water.

Earth's Glacial Record

Abstract: 1 Geodynamic controls on glaciation in Earth history N Eyles and G M Young 2 Glacial-marine facies in the continental rift environment: Neoproterozoic rocks of the western United States Cordillera P K Link, J M G Miller and N Christie-Blick 3 The Neoproterozoic Konnarock formation, southwestern Virginia, USA: glaciolacustrine facies in a continental rift J M G Miller 4 Glaciogenic deposits of the Permo-Carboniferous Dwyka Group in the eastern region of the Karoo Basin, South Africa V Von Brunn 5 Itarare Group: Gondwanan Carboniferous-Permian of the Parana Basin, Brazil A B Franca 6 The interpretation of massive rain-out and debris-flow diamictites from the glacial-marine environment J N J Visser 7 Neoproterozoic tillite and tilloid in the Aksu area, Tarim Basin, Xinjiang Autonomous Region, Northwest China Lu Zongnian and Gao Zhenjia 8 Lithology, sedimentology and genesis of the Zhengmuguan Formation of Ningxia, China Lu Zongnian, Gao Zhenjia, Zheng Zhaochang, Li Yuzhen and Li Huaikun 9 Architectural styles of glacially influenced marine deposits on tectonically active and passive margins M R Gipp 10 Marine to non-marine sequence architecture of an intracratonic glacially related basin Late Proterozoic of the West African platform in western Mali J N Proust and M Deynoux 11 The enigmatic Late Proterozoic glacial climate: an Australian perspective G E Williams 12 Isotopic signatures of carbonates associated with Sturtian (Neoproterozoic) glacial facies, central Flinders Ranges, South Australia A R Crossing and V A Gostin 13 Reactive carbonate in glacial systems: a preliminary synthesis of its creation, dissolution and reincarnation I J Fairchild, L Bradby and B Spiro 14 A Permian argillaceous syn- to post-glacial foreland sequence in the Karoo Basin, South Africa J N J Visser 15 A palaeoenvironmental study of black mudrock in the glacigenic Dwyka Group from the Boshof-Hertzogville regional northern part of the Karoo Basin, South Africa D I Cole and A D M Christie 16 Late Paleozoic post-glacial inland sea filled by fine-grained turbidites: Mackellar Formation, Central Transantarctic Mountains M F Miller and J W Collinson 17 Ice scouring structures in Late Paleozoic rhythmites, Parana Basin, Brazil A C Rocha-Campos, P R Dos Santos and J R Canuto 18 Soft-sediment striated surfaces and massive diamicton facies produced by floating ice C M T Woodworth-Lynas and J A Dowdeswell 19 Environmental evolution during the early phase of Late Proterozoic glaciation, Human, China Qi Rui Zhang

Superanoxia Across the Permo-Triassic Boundary: Record in Accreted Deep-Sea Pelagic Chert in Japan

Abstract: Nearly 57% of marine invertebrate families died out when the biggest mass extinction of the Phanerozoic took place at the Permo-Triassic (P/T) boundary. The lithologic change across the boundary recorded in a pelagic chert sequence in Japan suggests a remarkable oceanic anoxic event (OAE) in a deep-sea environment and its relevant effect on the extinction. The boundary unit in the deep-sea pelagic sequence occurs in the Jurassic accretionary complex in southwest Japan and consists of ca. 30 m of thick light gray to olive green siliceous claystone closely associated with jet black carbonaceous claystone (10-15 m thick). Stratigraphically under- and overlying units consist of red bedded radiolarian cherts. Paleozoic radiolarians were completely replaced by Mesozoic ones across the boundary. The boundary claystone is characterized by dark colors and ubiquitous occurrence of authigenic pyrite, indicating reductional depositional conditions, i.e., deep-sea anoxia, while hematite bearing red cherts above and below indicate a long lasting (>50 m.y.) oxic condition. As deep-sea sediments may normally record global oceanographic conditions on average, the present results suggest that an OAE occurred on a global scale across the P/T boundary and that this boundary deep-sea anoxia persisted for nearly 10 m.y. (from the Longtanian, early Late Permian to Anisian, early Middle Triassic), i.e., an extraordinarily long term in the Phanerozoic. A new term, “superanoxia”, is coined in order to discriminate this peculiar long term deep-sea OAE across the P/T boundary from other ordinary OAEs in the Phanerozoic. The P/T boundary mass extinction is probably related to this superanoxia and to the assembly of Pangea.

Triassic Deposystems, Paleogeography, and Paleoclimate of the Western Interior

Abstract: During the Triassic, the supercontinent Pangea was at its greatest size—a single landmass symmetrically disposed about the paleoequator. This configuration maximized monsoonal circulation, a global climatic pattern that had a strong influence on the distribution and facies of continental deposits. Triassic paleogeography and deposystems of the Western Interior should be examined in a global context because at that time the region lay near the western equatorial coast of Pangea, where the effects of the tropical monsoonal climate were pronounced. In addition to the climatic controls on sedimentation, sea-level fluctuations and plate tectonics, both to the west in the miogeocline and to the east on the craton, affected Early Triassic marine and Late Triassic continental deposition. Concomitant with the end of Early Triassic miogeoclinal sedimentation, an evolving magmatic arc along the western margin of Pangea produced a Late Triassic continental basin, contributed volcanic detritus, and recycled uplifted, upper Paleozoic clastic detritus to the region. The Early Triassic of the Western Interior was marked by marine-basin, marine-shelf, marginal-marine, sabkha, and deltaic systems on the west that graded eastward into coastal plain and continental red bed systems sourced from the east on the craton and from local uplifted highlands. Three Early Triassic transgressive and regressive sequences allow comparison of relative sea-level curves to Triassic marine systems throughout Pangea. Middle Triassic rocks in the Western Interior are rarely preserved because nondeposition and/or extensive erosion formed a regional unconformity. Rocks of this age are documented in only a few scattered localities on the craton, but extensive Middle Triassic marine strata are exposed farther west. Late Triassic deposystems in the southern part of the Western Interior were dominated by continental facies that included abundant stream, floodplain, lake, and marsh deposits, and at the close of the Triassic by playa-lake, eolian sand-sheet, and eolian dune deposits. Farther north in the Rocky Mountain region, Late Triassic depofacies included stream, floodplain, arid-region lakes, and play a deposits. The prominence of arid continental systems in the northern Western Interior reflects the slightly higher latitudes of this region on Pangea during the Late Triassic, a location just north of the greatest influx of monsoonal precipitation. Triassic continental systems dominated by streams, lakes, and marshes indicate abundant precipitation, in contrast to preceding Permian and subsequent Early Jurassic deposystems that were dominated by eolian ergs, arid-region lakes, and arid-climate coastal-marine systems. This larger scale climatic change reflects two major controls: (1) the norm ward migration of the Western Interior near the west coast of Pangea from near the paleoequator in the Permian to a position farther north of the paleoequator in the Jurassic and (2) the demise of the monsoonal climate, resulting from the breakup of Pangea in the latest Triassic and earliest Jurassic. Interpretations of Triassic stratigraphy, sedimentology, paleontology, and paleoecology, and comparisons with sequences worldwide must be placed in the context of Pangean paleogeography, paleoclimate, and sea-level fluctuations.

Plumes in central Panthalassa? Deductions from accreted oceanic fragments in Japan

Abstract: Accretion of a large number of seamounts or fragments of huge oceanic plateaus is recorded in the geology of Japan. Major accretion occurred twice; a late Early Carboniferous seamount chain accreted in latest Permian to Middle Jurassic time, and a Late Jurassic oceanic plateau accreted in the Early Cretaceous. The Late Jurassic plateau now in northern Japan and Sakhalin is here named the “Sorachi Plateau” and a Tithonian age for it is well documented on the basis of microfossils from pelagic cherts and limestones. Petrochemical characteristics of basalts suggest two kinds of sources; depleted mantle under oceanic lithosphere and enriched mantle related to plume upwelling. All the accreted fragments in Japan can be traced back to the central part of the Panthalassa by using paleomagnetic data and plate “trajectory analysis”. The timing of generation of the accreted seamount chain and the plateau is consistent with a time of global change. Their place of origin, in the mid-Pan thalassa, retains a positive residual geoid anomaly and slow Vp in the lower mantle, which suggest a past upwelling of hot material from the core-mantle boundary.

Brachiopods near the Permian-Triassic boundary in South China

Abstract: Xu, Guirong, and Richard E. Grant. Brachiopods Near the Permian-Triassic Boundary in South China. Smithsonian Contributions to Paleobiology, number 76, 68 pages, 54 figures, 7 tables, 1994.—Sixty-eight genera and 164 species in the Changxingian Stage and 12 genera and 20 species in the lower Griesbachian Stage are recorded on the basis of brachiopod fossils collected from 32 sections in South China and from review of the Chinese literature. Of these, 24 genera and 34 species are described here, including three new genera (Fanichonetes, Prelissorhynchia, and Rectambitus) and 24 new species (Acosarina strophiria, Enteletes asymmatrosis, Peltichia schizoloides, Derbyia pannuciella, Perigeyerella altilosina, Chonetinella cursothonia, C. volitanliopsis, Fanichonetes campigia, Cathaysia spiriferoides, Uncinunellina multicostifera, Prelissorhynchia triplicatioid, Cyrolexis antearcus, Cyrolexis beccojectus, Cartorhium xikouensis, C. twifurcifer, Callispirina rotundella, Araxathyris subpentagulata, A. beipeiensis, Spirigerella discsella, S. ovaloides, Squamulariaformilla, Hustedia orbicostata, Rostranteris ptychiventria, and Notothyris bifoldes). The Cathaysia chonetoides-Chonetinella substrophomenoides assemblage zone and the Cathaysia sinuata-Waagenites barusiensis assemblage zone represent respectively faunas of the lower Changxingian and the upper Changxingian in clastic lithofacies; whereas the Peltichia zigzag-Prelissorhynchia triplicatioid assemblage zone and the Spirigerella discusellaAcosarina minuta assemblage zone represent faunas in limestone lithofacies. The Crurithyris pusilla-Lingula subcircularis assemblage zone and Permian-type brachiopods are present in the lower Griesbachian. The Changxingian brachiopod fauna can be correlated with the Dorashamian fauna of Armenia; the brachiopod faunas of the Ali Bashi Formation, North-West Iran; unit 7 of the Hambast Formation, Central Iran; and the upper part of the Bellerophon Formation of the Southern Alps. The genera Cathaysia, Peltichia, and Prelissorhynchia are especially characteristic of the Cathaysia Tethyan Subprovince. In contrast, the West Tethyan Subprovince is characterized by the genera Costiferina, Ombonia, Comelicania, and many other species. Four brachiopod ecofacies are recognized in the Changxingian of South China: (1) antibiohermal dwellers; (2) calcareous substratum dwellers; (3) biohermal dwellers; and (4) ubiquitous substrate dwellers. In the lower Griesbachian, the brachiopod fauna of Lingula and Crurithyris spreads across the entire Tethys and is called the Circum-Pangaea brachiopod fauna. Massive extinction of brachiopod faunas occurred at the close of the Changxingian, with only a few Permian-types surviving into the early Griesbachian, and they completely vanished after the early Griesbachian except for harbingers of Mesozoic brachiopods. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The trilobite Phacops tana Green. Library of Congress Cataloging-in-Publication Data Xu, Guirong Brachiopods near the Permian-Triassic boundary in South China / Guirong Xu and Richard E. Grant. p. cm. — (Smithsonian contributions to paleobiology ; no. 76) Includes bibliographical references. 1. Brachiopoda, Fossil—China. 2. Paleontology—Triassic. 3. Paleontology—Permian. I. Grant, Richard E. II. Title. III. Series. QE701.S56 no. 76 [QE796] 560 s-dc20 [564'.8'0951] 93-11614 ® The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1984.

Structural and Tectonic Synthesis for the Perth Basin, Western Australia

Abstract: The Perth Basin is localised by reactivation of Neoproterozoic shear zones on the western margin of the Archaean Yilgarn Craton in Western Australia. While Ordovician to Silurian sandstones were deposited in the northern Perth Basin, the earliest sediments elsewhere are Middle Carboniferous to Permian in age. A sinistral transtensional regime, during which the main architecture of the basin was established, developed during NE-SW extension between Greater India and Western Australia in the Permo-Triassic. NW-SE shortening with continued NE-SW extension resulted in sinistral transpression in the late-Early to Middle Triassic. Sag-phase sedimentation in the Late Triassic followed this oblique rifting event.

The Upper Carboniferous-Permian Oslo Rift; Basin Fill in Relation to Tectonic Development

Abstract: The Permo-Carboniferous Oslo Rift, an en echelon graben system, was created by east-west extension partly caused by dextral movement along the Sorgenfrei-Tornquist-Teissure Zone. This zone was most likely activated by a late compressional event in the Variscan segment of the Hercynian Orogenic cycle. The Oslo Rift is thus an example of local suturation during the creation of the Pangea super-continent. The north-south trending Oslo Rift system consists of the onshore Oslo Graben and the offshore Skagerrak Graben. The basin-fill of the onshore Oslo Graben is characterised by large volumes of volcanics and only minor sedimentary rocks, for which a six phase development model from pre-rift to the termination phase has been derived. The pre-rift and initial rift phases (Late Carboniferous) coincided with the late Variscan stage of the Hercynian Orogeny. The basin fill which accumulated prior to the rift basin formation, the pre-rift phase, consists of a thin alluvial and deltaic succession with a marine limestone of (?) Moscovian age. The initial rift phase is recorded in the Vestfold Graben with more than 1500 m of alkali basalt lavas, while in the north, close to the transfer zone in the initial Oslo Graben, the basin fill comprises Gzelian lacustrine delta and volcaniclastic alluvial fan deposits capped by a single tholeiitic basalt. The synrift phase (Early Permian) is divided into two sub-phases that were characterized by plateau lavas, fissure eruption and normal faulting as well as formation of central volcanos and caldera collapse. The basin fill in the syn-rift phase, besides volcanics and thin but widespread continental deposits that are intercalated with the plateau lavas, developed as thick alluvial fan deposits along the master fault or locally inside the rift valley along escarpments bounding a volcanic accommodation zone, and as thick eolian and wadi deposits in the northern part of the Oslo Graben. The two last recorded phases (late Early and Late Permian) of graben development were the emplacement of young syenitic and granitic batholiths. The highly volcanic Oslo Rift is comparable with the Kenya Rift of the East African rifts and has some similarities to the Rio Grande Rift. In many periods the high production rate of extrusives in the Oslo Graben was enough to fill the relief created by extension, thus explaining the small amount of syn-rift sediments. Although only known from seismic and geophysical data, the basin-fill development of the offshore Skagerrak Graben is similar to the Oslo Graben, but probably with less volcanism. A post-rift sedimentary cover as a response to thermal cooling has probably been developed in the offshore Skagerrak Graben. A previous existence of post-rift basin fill in the onshore Oslo Graben is unclear. Post-rift sediments may also have been developed there, but at different scale and time in comparison to the Skagerrak Graben due to variations in duration and activity of the magmatism. The assumed post-rift infill is dated as Late Permian (offshore graben) and Triassic/ Early Jurassic (onshore graben) by onshore age determination and by seismic/well correlation between neighbouring basins. Subsequent uplift and erosion of the Oslo Rift and surrounding areas are suggested to have occurred in Early Triassic and “mid” Jurassic, with stripping of the post-rift basin fill in the offshore Skagerrak Graben taking place in Early Triassic, whereas “mid” Jurassic uplift removed the possible post-rift basin fill and much of the syn-rift basin fill of the onshore Oslo Graben. Potential source rocks are burned out in the Oslo Graben. However the Skagerrak Graben may yet prove to be hydrocarbon bearing.

Conodonts from the Lower Griesbachian Otoceras Latilobatum Bed of Selong, Tibet and the Position of the Permian—Triassic Boundary

Abstract: The conodont fauna from the Lower Griesbachian Otoceras latilobatum bed at Selong, Tibet comprises Hindeodus typicalis, Isarcicella? parva, Neogondolella aff. N. carinata, N. aff. N. changxingensis, N. taylorae n. sp., and N. tulongensis. A single Isarcicella isarcica is reported from the top of the bed. Concurrent appearance of Isarcicella? parva and Otoceras is confirmed. The Selong conodont fauna of the Otoceras latilobatum bed differs from that of the uppermost Permian Changhsingian and Dorashamian stages. Earlier reports of uppermost Permian conodonts in the Griesbachian, and of Griesbachian conodonts in the uppermost Permian are refuted or remain unverified. Taxonomic revision of many of the Neogondolella species from the P—T boundary interval is given, including the description of lowermost Triassic N. taylorae n. sp. and uppermost Permian N. n. sp. A.

Mesozoic-Cenozoic burial, uplift, and erosion history of the west-central Colorado Plateau

Abstract: Apatite fission-track data show that Permian strata forming the Colorado Plateau surface at the Grand Canyon underwent burial temperatures of ∼90-100 °C in the Late Cretaceous, indicating that ∼2.7-4.5 km of Mesozoic strata covered the area at that time. This is similar to the ∼2.5-3.5 km thickness of Mesozoic section preserved to the north in southern Utah and confirms that those strata once extended south over a much broader area of the Colorado Plateau. Cooling from maximum burial temperatures began about 75 Ma, indicating that Laramide-age erosion removed ∼1.3-4.5 km of Mesozoic strata from the area. This erosion was probably caused by topographic relief created by Laramide reactivation of monoclines and reverse faults. Permian strata in the Waterpocket monocline in southern Utah underwent burial temperatures of ∼90 °C in the Late Cretaceous, consistent with the idea that the Permian to Upper Cretaceous section exposed in the monocline formerly extended south over the Grand Canyon region.

Case for the Gamburtsev Subglacial Mountains of East Antarctica originating by mid-Carboniferous shortening of an intracratonic basin

Abstract: The present drainage of East Antarctica, with ice radiating from a central dome draped over the thick crust of the Gamburtsev Subglacial Mountains, recapitulates the Early Permian scene, including the south polar paleolatitude. The Permian radial drainage was on the same scale as the present drainage around the thick crust of the Tibetan Plateau. Another high region in Carboniferous- Permian time was the upland of Europe on crust thickened during the Variscan collision to form Pangea. The ancestral Gamburtsev Subglacial Mountains and a central Australian upland may have formed because of long-distance stress from the Variscan collision acting on zones of weak crust attenuated during prolonged subsidence of intracratonic basins. The mid-Carboniferous inception of widespread glaciation was possibly linked with vast uplands in northern and southern Pangea through the effects of Variscan topography and the removal of atmospheric CO 2 during accelerated erosion and weathering.