Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 22 November 2011 Ping Liu, Chenglong Deng, Shihu Li, Shuhui Cai, Hongjiang Cheng, ... The Nihewan Basin sedimentary sequences in northern China are rich in mammalian fossil and Paleolithic sites, thus providing insights into our understanding of Quaternary land mammal biochronology and early human settlements in East Asia. Here we present high-resolution magnetostratigraphic results that place stringent age controls on the Xiashagou (XSG) Fauna (that is, the well-known Nihewan Fauna sensu stricto) in the Nihewan Basin, northern China. Results show that the XSG sequence recorded the Brunhes normal chron, the Matuyama reverse chron and the late Gauss normal chron. The XSG Fauna resides in the Matuyama reverse chron (between the pre-Reunion Matuyama chron and the post-Olduvai Matuyama chron), yielding an estimated age of ca. 2.2−1.7 Ma. The Pliocene−Pleistocene boundary (Gauss/Matuyama boundary) is located in the lower part of the XSG section. The combination of our study and previously published magnetostratigraphic data suggest that the mammalian fossil sites in the eastern Nihewan Basin can be placed between the Gauss–Matuyama geomagnetic reversal and the Matuyama–Brunhes geomagnetic reversal (2.58−0.78 Ma), leading to a time range of ca. 2.6−0.8 Ma for the Nihewan mammalian faunas. Highlights ► Precise age of the Nihewan faunas is crucial for Quaternary mammal biochronology. ► We report a new magnetostratigraphy on the Xiashagou Fauna in the Nihewan Basin. ► The Xiashagou Fauna (the Nihewan Fauna sensu stricto) is dated to be 2.2−1.7 Ma. ► The age of the Nihewan faunas can be revised to a time range of ca. 2.6−0.8 Ma. ► The chronology of the well-known Nihewan faunas has been significantly improved.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 19 November 2011 Karla M. Parsons-Hubbard, Carlton E. Brett, Sally E. Walker Fossilization of organism remains is the result of biological, physical, and chemical processes at work in the environment of deposition. The pathways taken by the remains of organisms through death, decay, burial, and diagenesis (known as taphonomic pathways) affect the fossil record of life in important ways, from complete removal and recycling of remains to preservation of hard parts and sometimes to exceptional preservation of soft tissues. Our understanding of taphonomic processes informs our interpretations of the fossil record and helps in the reconstruction of ancient environments. Research into taphonomic pathways in modern environments provides important insight into the fossilization process. In 1993, a group of paleontologists formed the Shelf and Slope Experimental Taphonomy Initiative (SSETI) and began a long-term comparative study of taphofacies and differential decay of taxonomic groups by placing experimental arrays containing bivalves, gastropods, decapod crustaceans, sea urchins, and wood species at multiple marine shelf and slope sites in the Bahamas and Gulf of Mexico. The goal of SSETI is to observe taphonomic processes over a period of decades to better understand taphonomic pathways for these various groups of taxa in a wide variety of depositional environments beyond the shallow near shore region. This special volume brings together eight studies that are the result of the SSETI program. The focus of this contribution is to first review the body of published work concerned with the fossilization process through the experimental manipulation of the remains of organisms in modern marine environments. We also present the methods of the SSETI project and its contributions to our understanding of taphonomic processes in relation to carbonate and wood recycling and preservation.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 21 November 2011 Pengfei Chen, Jisuo Jin, Alfred C. Lenz Brachiopod communities have been widely used for palaeoecological studies and reconstruction of sea-level changes in Earth history. Previous studies of brachiopod communities emphasised sampling benthic shelly fossils preserved in situ to avoid preservation bias. Silurian (Wenlock) brachiopod assemblages are well preserved as debris-turbidity flows, including calcareous concretions, embedded in thick sequences of black shale of the Cape Phillips Formation, with a mixture of deep-water brachiopods and transported shallow-water forms. In this study, the first attempt is made to use the transported assemblages to reconstruct Silurian brachiopod communities that once lived along a palaeogradient from the shallow-water Arctic Platform to the deep-water Franklinian Basin. Seven transported brachiopod assemblages were recognised using multivariate analyses (cluster analysis and principal components analysis), with varying ratios of shallow- versus deep-water shells, segregated according to their known palaeobathymetric ranges in other regions. The Wenlock–early Ludlow sea-level fluctuations in the study area, reconstructed using the percentage values of shallow- and deep-water brachiopod specimens as a proxy, have a high degree of agreement with the Arctic Silurian sea-level curve and moderate agreements with global sea-level histories of other regions such as the British Isles and Gotland interpreted from graptolite abundance and diversity changes, and sequence and event stratigraphical methods, respectively. Highlights ► Silurian brachiopod assemblages are rich and diverse in debris/turbiditic flow deposits of Arctic Canada; ► Varying ratios of deep- vs. shallow-water taxa in transported brachiopod assemblages were controlled by changes in sea level and proximity to shoreline; ► Silurian sea-level curve can be reconstructed using brachiopod assemblages as a proxy.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 21 November 2011 G.C. Baird, J.J. Zambito, C.E. Brett The Middle Devonian (late middle Givetian) Tully Formation in New York State is the type regional expression of the global Taghanic Biocrisis. It is marked by anomalous development of massive to rhythmically bedded, micritic limestone deposits within a vastly thicker Acadian foreland basin clastic succession. Lower-medial Tully carbonates record the incursion of tropical Old World Realm (OWR) taxa (Tully Fauna) and the outage of the long-standing, higher diversity, cooler-water, endemic Eastern Americas Realm (EAR) biota (Hamilton Fauna). Succeeding Tully strata record a return of the Hamilton Fauna followed by its demise due, both to replacement by the lower diversity, cosmopolitan Genesee Fauna and by the overspread of widespread anoxic bottom conditions coupled with the onset of drastically increased sediment input following Tully Group deposition.Massive, micritic limestones, yielding modest diversity Tully Fauna assemblages are particularly characteristic of the lower-medial Tully succession on the western New York Tully platform; these are coeval with nearly barren ribbon limestone and siltstone deposits in the adjacent New Berlin (east-central New York) and central Pennsylvania basins. These depocenters trapped terrigenous sediment and helped to create sediment-starved conditions on the platform. Anomalous Tully carbonate deposition is believed to be coincident with strong super estuarine water mass stratification in offshore Tully shelf and basin settings where a warmer, denser, more saline water mass flowed northward (shoreward) across the study area beneath a counter flow of oxygenated, river-influenced surface water. Dysoxic conditions would have developed below the pycnocline, favoring the Tully Fauna incursion, precipitation of carbonate mud, and possibly promoting the formation of ooidal chamosite.At least five thin (1–30 cm-thick) mappable beds of black, ooidal, chamosite, are observed in Taghanic shelf margin, slope, and basin deposits. These beds are typically intensely bioturbated, variably rich in associated siderite, contain corroded low-diversity fossil assemblages, and are regionally associated with condensed lag deposits above unconformities. Work by others suggests that chamosite formation occurs under minimally reducing, post-oxic, interstitial conditions which are followed, in turn, by more strongly reducing conditions which allow for variable siderite and pyrite formation. Terrestrial pedogenic alteration of silicates by evolving land plant communities under warm, humid conditions led to an increased supply of kaolinite as well as Iron oxides and hydroxides that served as precursors to chamosite formation. In the New Berlin Basin, the transgressive, top-Hamilton-base-Taghanic succession is marked by a succession of diastems associated with basin deepening and upward-increasing chamosite occurrence in dysoxic facies. Occurrence of ooidal chamosite in upper medial Tully platform deposits (Smyrna Bed) may reflect water mass stratification and extreme sediment-starvation at the shelf margin. Eastward spectral transformation of sparsely fossiliferous Smyrna ooidal chamosite in the western New Berlin Basin into richly fossiliferous, non-chamositic, equivalent neritic deposits east of that basin, suggests that the counter-flow of oxygen and nutrient-rich, lower salinity water had blocked the denser, restricted water layer from advancing over the eastern Tully clastic shelf closer to shore. Highlights ► We examine relationship of Taghanic biocrisis to unusual sediment accumulation. ► We describe anomalous limestone and chamosite deposits of Tully Formation. ► We link these deposits to patterns of biotic overturn and stress. ► chamosite is linked to sediment-starvation and weakly reducing, interstitial conditions. ► Tully deposits and faunas are linked to episodes of water mass stratification.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 22 November 2011 Ian G. Percival Early to Middle Ordovician cherts and cherty siltstones associated with distal turbidite deposition in back-arc basins, are widespread in the Hermidale and Albury-Bega Terranes of the Lachlan Orogen in New South Wales. Study of more than 2500 bedding plane-parallel thin sections prepared to a thickness of 50 microns from these cherts enables recognition of four conodont zones that range in age from the late Tremadocian to latest Darriwilian. Comparable cherts are present in two small remnants of oceanic derivation now exposed on the coast of New South Wales, in the Narooma Terrane (Furongian to Darriwilian), and in the New England Orogen at Port Macquarie in allochthonous blocks (Late Ordovician). Associated fauna include radiolaria, sponge spicules, lingulide and acrotretide brachiopods, fragmentary graptolites, and rare filaments attributed to cyanobacteria. Some of these organisms were pelagic, or may have been attached to floating material, and hence became entrapped in siliceous ooze on the sea floor when they settled under gravity. Others (e.g. the brachiopods) may have been attached to sponges growing on the sea floor. The presence of burrows and bioturbation demonstrates that the deep-sea environment in the Middle Ordovician was well-oxygenated, though this contrasts with Lower Ordovician environments where evidence for infauna is lacking. Predominant coloration of the cherts examined in thin section ranges from honey and yellow-brown (typical of semitransparent cherts) through cream-colored translucent lithologies to opaque varieties. Dark brown cherty rocks that show evidence of burrowing or bioturbation tend to have a higher silt component. The Ordovician is also a time of extensive chert deposition elsewhere, including terranes in Kazakhstan (commencing in the Late Cambrian); these siliceous sediments display many of the features described from eastern Australia. Highlights ► Ordovician cherts & biota from SE Australia described and illustrated in colour. ► These cherts & associated siliceous sediments are compared with Kazakhstan. ► Timing of transition from anoxic to oxygenated conditions in Ordovician oceans.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 25 November 2011 Dmitry A. Ruban Possible dependence of ammonite diversity dynamics on shoreline shifts, i.e., transgressions and regressions, is yet to be understood. Data from the Greater Caucasus Basin, which was located on the northern active margin of the Neo-Tethys Ocean in the Mesozoic, permit to analyze the noted dependence at the Toarcian–Aalenian time interval. Distribution of 161 species and 40 genera in each regional ammonite-based biozone of this interval allows to evaluate the diversity dynamics of ammonites. The total number of both species and genera changed cyclically. The diversity maxima occurred in the H. bifrons, G. thouarsense, and L. murchisonae zones. The diversity minima occurred in the D. semicelatum, H. variabilis, P. aalensis, and G. concavum zones. Semi-quantitative analysis of facies distribution in 28 areas of the basin indicates a stepwise early Toarcian–middle Aalenian transgression, followed by a late Aalenian regression. The general trend towards species diversification through the study interval coincided with the noted transgression. This is an evidence of partial dependence, but no dependence between the generic diversity dynamics and shoreline shifts is visible. It is hypothesized that transgressions facilitated the growth of the ammonite diversity, but, when they stopped, the diversity was controlled by other factors. Changes in the spatial distribution of deep-marine palaeoenvironments might also affect the ammonite diversity dynamics, but no regional evidence of importance of oxygen depletion and seawater temperature fluctuations is found. The minimal ammonite diversity in the D. semicelatum Zone could be a consequence of the Early Toarcian mass extinction. In the Greater Caucasus Basin, the latter occurred at a peak of regression. Highlights ► Regional ammonite diversity changed cyclically during the Toarcian–Aalenian ► Transgression facilitated an increase in the total number of species ► Early Toarcian mass extinction affected ammonites in the Greater Caucasus Basin

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 25 November 2011 Lindsey C. Henry, John L. Isbell, Christopher R. Fielding, Eugene W. Domack, Tracy D. Frank, ... The Wynyard Formation of Tasmania, Australia, provides the last evidence of grounded ice during the Late Carboniferous – Early Permian in the Tasmania Basin of southeastern Gondwana during the late Paleozoic ice age. Within the Wynyard Formation, four facies associations are recognized: 1) massive diamictite, 2) stratified diamictite, 3) conglomerate and sandstone, and 4) deformed mudstone and fine sandstone. A detailed facies analysis was performed in order to interpret the depositional processes and environments. The massive diamictite facies association contains massive diamictite and massive sandstone and was deposited primarily by iceberg rain-out in a subaqueous morainal bank setting. The stratified diamictite facies association is composed of stratified diamictite, sandstone, and conglomerate, and was deposited by debris flows and iceberg rain-out, and deformed by glacial pushing. The conglomerate and sandstone facies association is made up of cross-stratified, channelized conglomerate and pebbly sandstone that were deposited by glacial outwash on grounding-line fans. The deformed mudstone and fine sandstone facies association is composed of pervasively deformed pebbly mudstone and fine-grained sandstone that exhibit volcano, flame, and dyke structures. This facies association was deposited by a combination of suspension settling, iceberg rain-out, and soft sediment deformation, in a quiet distal proglacial setting. The facies analysis supports the interpretation that the Wynyard Formation was deposited by a wet-based, tidewater glacier or glaciers. The depositing glacier(s) occupied a ~ 40 km - wide trough in northwest Tasmania. Based on the distribution of the Wynyard Formation and the presence of glacial deposits in other eroded troughs in Tasmania, glaciation occurred in the region within broadly eroded valleys. The Wynyard Formation and overlying mudstone of the Inglis Formation provide a glacial-postglacial signature similar to those in South Africa, Antarctica, and eastern Australia during the latest Carboniferous – Early Permian, therefore the climate warmed in southern Gondwana following this glacial interval. Continued glaciation in eastern Australia was a result of regional topography and oceanographic processes. Highlights ► A facies analysis was performed to interpret the depositional processes and environments. ► The Wynyard Formation was deposited by wet-based, tidewater glaciers. ► The glacial-postglacial signature is similar in South Africa, Antarctica, and Australia. ► Continued glaciation in eastern Australia was a result of topography.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 25 November 2011 Kentaro Izumi, Tsuzumi Miyaji, Kazushige Tanabe The early Toarcian oceanic anoxic event (T-OAE) was marked by the worldwide burial of organic-rich black shales and a coincident pronounced negative carbon-isotope excursion of carbonates, organic matter, and fossil wood. This characteristic carbon-isotope perturbation and other geochemical records have been recognized in many sections in the European domain and in selected sections in the central and eastern Panthalassa, but not in the western Panthalassa. We present herein, for the first time, data of carbon isotope ratios of organic carbon, total organic carbon (TOC) contents, and sedimentary fabrics from the uppermost Pliensbachian to the lower Toarcian sequence in the Sakuraguchi-dani Valley, Toyora area, west Japan, that was deposited in the shelf basin of the northwestern Panthalassa. The carbon-isotope profile displays a similar trend to those in contemporaneous strata in the Tethys and in the eastern and central Panthalassic regions, which is characterized by a distinct negative excursion around the Tenuicostatum/Falciferum Zone boundary in the early Toarcian. This evidence suggests that the widely recognized negative carbon-isotope excursion represents a nature of the global carbon-cycle perturbation. Analyses of total organic carbon contents and sedimentary fabrics in the study section reveal that accumulation of organic carbon occurred and anoxic bottom-water was prevalent during the early Toarcian. The most organic-rich strata and bottom-water anoxia described in the study section, however, exist in the interval showing the carbon-isotope positive recovery after the abrupt negative shift, and this fact suggests that the accumulation of organic matters and development of marine anoxia were globally diachronous, even though the negative CIE was interpreted as a synchronous event. Our study also demonstrates that the early Toarcian anoxia in the northwestern Panthalassic basin was not a single and continuous anoxic event but was interrupted by episodic short-term oxygenation events. Highlights ► We present the first early Toarcian carbon-isotope data from NW Panthalassa. ► TOC accumulation did not precisely coincide with the negative CIE. ► Bottom-water anoxia was episodically interrupted by short-term oxygenation events.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 1 December 2011 Jenaro L. García-Alcalde, Brooks B. Ellwood, Francisco Soto, Montse Truyóls-Massoni, Jonathan H. Tomkin The ability to correlate with high precision among geological successions is critical in evaluating the global coincidence and therefore magnitude and duration of geological events. This is a difficult problem given resolution uncertainties and ambiguities in biostratigraphic data sets. The magnetostratigraphy susceptibility (MSS) method, based on low-field bulk magnetic susceptibility (MS) measurements of closely-spaced samples, provides a well-established, abiotic, high-resolution correlation tool in stratigraphy, that when combined with bio-, chemostratigraphic, and other geophysical techniques, offers ways to resolve correlation problems. In addition, such data sets lend themselves to time-series analysis, where developing high-resolution timing of events becomes possible. This paper examines the final episode (equivalent to the Geneseo Bioevent in the Appalachian Basin) of the important Taghanic Biocrisis known from globally distributed Middle Devonian geological sections. The Geneseo Bioevent is important because the extinction of some major fossil groups occurred during this time, while other groups declined significantly, including many benthonic groups. However, the maxima of extinctions does not appear to have occurred everywhere simultaneously. To help resolve timing of this bioevent, results are reported for two Middle Devonian successions from Northern Spain, the S. Huergas de Gordón and Punta Boletos sections, both showing the final Taghanic Biocrisis, Geneseo interval, and correlate these sucessions to the same interval within an independent, global database. Time-series analyses of the MSS data sets from the Spanish sections was performed using Multi-Taper (MTM) and Fourier Transform (FT) methods, and have extracted well-defined Milankovitch bands from the primary MS data from each section. Using FT and MTM values for eccentricity at ~ 400 kyr and ~ 100 kyr, a floating-point time scale was developed for the two Spanish sections that provides age resolution to ~ 50 kyr for these sucessions. The results show that the Geneseo Bioevent in Northern Spain occurred within a narrow time window estimated to have lasted for ~ 70 kyr. This time window fallswithin thePolygnathus ansatus (uppermost part)—Ozarkodina semialternansconodont zones, just at the Middle—Upper Givetian boundary of the Middle Devonian in what appears to be the upper, regressive phase of T-R cycle IIa. Highlights ► To help resolve timing of the uppermost Taghanic Biocrisis, Geneseo Bioevent, we report our results for two Middle Devonian successions from Northern Spain, the S. Huergas de Gordón and Punta Boletos sections, both containing the Geneseo Bioevent, and correlate these sequences to theTaghanic Biocrisis interval within an independent, global database. ► The results show that the Middle Devonian Geneseo Bioevent in Northern Spain occurred within a narrow time window estimated to have lasted for ~ 70 kyr. This time window fall s within the Polygnathus ansatus — Ozarkodina semialternans conodont Zone, just below the Middle—Upper Givetian boundary of the Middle Devonian in what appears to be the upper, regressive phase of T-R cycle IIa. ► We have extracted well-defined Milankovitch bands from the primary magnetic susceptibility data from the two Spanish sections studied. Using Multi-Taper and Fourier transform values for eccentricity at ~ 400 kyr and 100 kyr, we have developed a floating-point time scale for the two sections that provides age resolution to ~ 50 kyr for these sequences.

Description: Publication year: 2011 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Available online 3 December 2011 Andrea K. Kern, Mathias Harzhauser, Ali Soliman, Werner E. Piller, Martin Gross High resolution pollen and dinoflagellate analyses were performed on a continuous 98-cm-long core from Tortonian deposits of Lake Pannon in the Styrian Basin in Austria. The sample distance of 1-cm corresponds to a resolution of roughly one decade, allowing insights into environmental and climatic changes over a millennium of Late Miocene time. Shifts in lake level, surface water productivity on a decadal- to centennial-scale can be explained by variations of rainfall during the Tortonian climatic optimum. Related to negative fine scale shifts of mean annual precipitation, shoreline vegetation belts reacted in an immediate replacement of Poaceae by Cyperaceae as dominant grasses in the marshes fringing the lake. In contrast to such near-synchronous ecosystem-responses to precipitation, a delayed lake level rise of 4–6 decades is evident in the hydrological budget of Lake Pannon. This transgression, caused by a precipitation increase up to 〉 1200 mm/yr, resulted in a complete dieback of marshes. Simultaneously, “open-water” dinoflagellates, such asImpagidinium, took over in the brackish lagoon and fresh water dinoflagellates disappeared. As soon as the rainfall switched back to moderate levels of ~ 1100–1200 mm/yr, the rise of the lake level slowed down, the marsh plants could keep up again and the former vegetation belts became re-established.Thus, mean annual precipitation, more than temperature, was the main driving force for high-frequency fluctuations in the Tortonian wetlands and surface water conditions of Lake Pannon. Such high resolution studies focusing on Tortonian decadal to centennial climate change will be crucial to test climate models which try to compare the Tortonian models with predictions for future climate change. Highlights ► High-resolution analyses were performed on a Late Miocene lake-sediment core. ► Pollen and dinoflagellates suggest lake-land-interlinkage on a decadal scale. ► Small variations in mean annual rainfall caused swift environmental changes. ► Miocene climate variability is detected on a scale comparable to Holocene records.