Showing papers in "Newsletters on Stratigraphy in 2013"

Geobiodiversity Database: a comprehensive section-based integration of stratigraphic and paleontological data

Abstract: The Geobiodiversity Database (GBDB – www.geobiodiversity.com), an integrated system for the management and analysis of stratigraphic and paleontological information, was started in 2006 and became available online in 2007. Its goal is to facilitate regional and global scientific collaborations focused on regional and global correlation, quantitative stratigraphy, systematics, biodiversity dynamics, paleogeography and paleoecology. It is unique among global, public access databases in that it is a section-based online database system, incorporating data from a wide range of disciplines of stratigraphy and paleontology, with inherent interrelationship between different kinds of data sets. It provides the capability of completely digitizing raw data, as well as integrating of different interpretations to the same paleontological and stratigraphic content. Several Windows-based visualization and analysis applications, either fully integrated with the database or supported by subset-export functions, have been developed to make the database more useful as a scientific and educational tool. The GBDB became the formal database of the International Commission on Stratigraphy (ICS) in August 2012 at the 34th International Geological Congress in Brisbane, and will produce comprehensive and authoritative web-based stratigraphic information service for global geoscientists, educators and the public.

Chemostratigraphy (CaCO3, TOC, delta C-13(org)) of Sinemurian (Lower Jurassic) black shales from the Wessex Basin, Dorset and palaeoenvironmental implications

Abstract: The Shales-with-'Beef' and Black Ven Marls of the Charmouth Mudstone Formation (Sinemurian) exposed on the Dorset Coast in southern England (Wessex Basin) show stratigraphic variation in carbonate, organic carbon and organic-carbon isotopes. Little environmental significance is attached to the variation of carbonate except in the case of the tabular and nodular limestones interrupting the sequence that probably record stratigraphic condensation and/or sedimentary stillstands that, in an extreme case, were accompanied by sea-floor erosion to produce the bored and encrusted ?Coinstone'. Relatively high total organiccarbon (TOC) contents are present in the laminated mudstones of the lower turneri Zone (upper brooki and lower birch Subzones) and the obtusum Zone (obtusum and stellare Subzones). Basin stratification related to fresh-water influx was the most likely aid to deoxygenation and enhanced preservation of organic matter. The organic-carbon isotope curve (δ13Corg), which shows positive excursions in the upper turneri Zone (upper birchi Subzone) and highest obtusum-raricostatum Zones (highest stellare Subzone, densinodulum and lower raricostatoides Subzones), does not correlate with the TOC stratigraphy and was clearly not controlled by local patterns of organic-matter burial. Long-term (hundreds-of-thousands of years) variations in the carbonisotope (δ13Corg) curve are interpreted as reflecting changing seawater isotopic composition and, in the case of the stratigraphically higher interval, may be related to marine organic-carbon burial on the margins of the proto-Atlantic, as exemplified by the Lusitanian Basin in Portugal. Correlation of the carbon-isotope profile with putative sea-level curves is problematic in detail, although significant local transgressive pulses in the turneri and late raricostatum Zones are approximately coincident with positive δ13Corg excursions.© 2013 Gebruder Borntraeger, Stuttgart, Germany.

Core alignment and composite depth scale for the lower Paleogene through uppermost Cretaceous interval at Deep Sea Drilling Project Site 577

Abstract: Deep Sea Drilling Project Site 577 on Shatsky Rise (North Pacific Ocean) recovered a series of cores at three holes that contain calcareous nannofossil ooze of latest Cretaceous (late Maastrichtian ...

First report of a newly discovered ediacaran biota from the irkineeva uplift, East Siberia

Abstract: New Ediacara-type macrofossils are described from the Irkineeva Uplift of East Siberia, Russia. Preliminary field studies within the Taseeva Group reveal probable examples of the Ediacaran taxa Arkarua adami and Beltanelliformis minutae; the organo-sedimentary structure 'Arumberia'; and 'elephant skin' microbial mat fabrics. These impressions are consistent with a latest Ediacaran age for the units of the upper Taseeva Group, suggesting that they are tens of millions of years younger than has previously been reported. Large discoidal specimens from the upper part of the Sukhoy Pit Group, likely to be Middle Riphean (Mesoproterozoic) in age, are tentatively assigned to the taxon Nimbia occlusa, and are suggested to be microbial in origin. These discs, and a contemporaneous acritarch assemblage of long-ranging sphaeromorphic taxa, cannot be precisely geochronologically constrained at present, but are highly likely to be pre-Ediacaran in age. The Irkineeva finds supplement a diverse suite of Russian Ediacaran (Vendian) fossil localities, and may be of considerable importance in correlating disparate Meso- and Neoproterozoic stratigraphic units across the Siberian Platform. This report emphasises the largely unexplored potential of the Irkineeva Uplift for palaeontological study, and provides tantalising evidence for the preservation of Late Ediacaran macro-organisms in this region.

Stratigraphic guide to the Rogaland Group, Norwegian North Sea

Abstract: This guide provides a major revision and update of the lithostratigraphy of the Rogaland Group for the Norwegian North Sea. An abundance of recent well and seismic data sheds new light on lithology, biostratigraphy, provenance, geographic distribution and terminology of all Rogaland rock units, used widely in the search for oil and gas. While finer siliciclastic units largely remain as previously defined, previous sandstone/siltstone formations and one (reworked) chalky unit are now re-defined. These lithostratigraphic units are local sediment bodies of a lithology different from the surrounding and embracing formation. Hence, these lithostratigraphic units are members in the formal stratigraphical hierarchy. With the new definitions and re-definitions the Rogaland Group now consists of four formations and 15 members, which span the stratigraphic interval from lower Paleocene to lower Eocene. The revisions concerning the sandstone bodies are of four different types: – Re-definition from formations to members – Re-definition of lithological criteria – Introduction of members long used already offshore England and Denmark – Definition of new members For those practicing geologists not familiar with historic precedence, an important ʻsine qua nonʼ in (litho-) stratigraphy, it should be pointed out that 8 out of 15 members discussed here have been predefined in literature dealing with the UK and Danish sectors of the North Sea. The present study thus updates the Norwegian lithostratigraphic bulletins of the nineteen eighties for its offshore area. The internet site www.nhm2.uio.no/ norlex provides an interactive digital version of this study, with links to well data, biozonations and core archives relevant to the Rogaland Group.

The basal Lutetian Transgression on the Tethyan shelf of the European craton (Adelholzen beds, Eastern Alps, Germany)

Abstract: The middle Eocene Adelholzen beds were deposited on the northern part of the Tethyan shelf of the European Plate. In the Eastern Alps, the Wimmern section near Teisendorf (Germany) is the only known outcrop exposing the basal unconformity of this sequence. The outcrop comprises an 8 m thick condensed transgressive shallow marine succession characterized by glauconite-rich weakly consolidated greensand and mudstone containing abundant larger benthic foraminifera. It spans the lower part of calcareous nannoplankton Zone NP15 (Sub-Zones NP15a and lower part of NP15b), planktonic foraminifera Sub-Zone E7b and Zone E8 partim and the upper part of shallow benthic Zone SBZ13. The landward migration of the paleo-shoreline was not an effect of flexural downbending of the European Plate but can be correlated to the major unconformity at the base of eustatic supercycle TA3. The onset of this sea-level rise was in the latest part of Biochron NP14b and almost coincided with the NP14b/NP15a-boundary.

Differentiating between tectonic and eustatic signals in the Rupelian Boom Clay cycles (Lower Oligocene, Southern North Sea Basin)

Abstract: The Rupelian Boom Clay in Belgium is a marine sedimentary deposit with an extensive data set. Astronomical control on high-frequency cyclicity has been proven before, and sedimentological analyses have shown climate-driven cycles caused by sea-level fluctuations. A long cycle in grain-size and bed thickness, involving the entire Boom Clay section, is related to tectonism. Shorter-duration low-frequency cycles, attributed in the past also to climate-driven eustasy, show a relationship with sediment supply expressed by bed thickness but related to tectonism. This apparent contradiction is studied by measuring the thickness differences of the individual Milankovitch-related (astronomical) beds in several wells with the thickness of the same bed in a reference well in the area. Such an approach eliminates eustasy as a controlling factor in the observed cyclicity patterns. Cumulative differential evolution maps of the basin are provided, and the evolution of the relative subsidence in all individual wells through time is visualised as cumulative-difference curves. Both approaches demonstrate that the levels considered in previous studies as controlled by eustasy in fact reflect tectonic history.

Unraveling the Paleocene-Eocene thermal maximum in shallow marine Tethyan environments: the Tunisian stratigraphic record

Abstract: Despite the increasing understanding of the Paleocene-Eocene thermal maximum (PETM) in open marine environments, shallow marine settings remain relatively unexplored. We investigated an upper Paleocene to lower Eocene shallow-water sequence near Kalaat Senan in Tunisia (Sidi Nasseur and Wadi Mezaz sections) in order to generate a stratigraphic framework of the PETM in a shallow marine fine-grained siliciclastic setting of the Southern Tethys. These sections expose the top part of the El Haria Formation (Fm.), the Chouabine Fm. and the lower part of the limestone bearing El Garia Fm., covering the upper Paleocene- lower Eocene (NP9a to NP11). The PETM interval is situated near the top of the El Haria Fm. and the re- gional stratigraphy is compared to the well-known Egyptian setting. The isotope record of total organic car- bon (δ 13 Corg) reveals the characteristic negative carbon isotope excursion (CIE), comparable to the δ 13 Corg record of the Global Boundary Stratotype Section and Point of the Eocene at Dababiya (Egypt). Although the Tunisian PETM interval is quite expanded, no anomalous beds are observed and only the CIE "core" is part- ly represented as the top part of the PETM is truncated. In addition to a well-expressed CIE, the position of the Paleocene-Eocene boundary is supported by the appearance of nannoplankton (Discoaster araneus) and foraminiferal (e. g. Acarinina multicamerata) marker taxa. Furthermore, ostracode and benthic foraminifer- al turnovers coincide with the onset of the PETM and are characterized by the disappearance of many com- mon Paleocene taxa (e. g. Frondicularia aff. phosphatica) in this area. The lowest occurrences of Alo- copocythere attitogonensis and Buntonia? tunisiensis (ostracodes), Reophax sp. 1 (benthic foraminifera) and Fasciculithus tonii (calcareous nannoplankton) may be applicable for regional correlation. These results in- dicate that characteristic PETM taxa evolved and/or dispersed immediately after the main δ 13 Corg shift.

An expanded lower Eocene shelf sequence from the eastern Aquitaine Basin, SW France: biostratigraphy, biofacies, and stable carbon and oxygen isotopes

Abstract: The early Eocene is characterized by a succession of orbitally-controlled global stable carbon isotope excursions, with some being linked to climatic and related biotic perturbations. The impact of these isotopic excursions has been primarily studied in deep-sea sections under comparably stable conditions. In order to investigate the impact of global post-PETM isotopic signals on shallow marine settings, the Ypresian neritic ʻBlue Marls’ of the Corbieres (SW France) were investigated. High-resolution records of microfossil biota and stable carbon and oxygen isotopes pinpoint biostratigraphic, paleoecologic and geochemic constraints. Calcareous nannofossil biostratigraphy positions the sequence in the upper part of zone NP11, possibly ranging into basal NP12, which is conformable with larger benthic foraminifera data indicating shallow benthic zone SBZ8. This implies a time span of about 0.4 Myr and high overall sedimentation rates of about ~ 32 cm/kyr for the section. A shallowing upward trend from outer neritic to coastal settings is observed in the development of the lithostratigraphy and the microfossil assemblage. The assemblages can be subdivided in seven larger biofacies and four ostracod assemblage zones. The lower third of the section is characterized by strongly fluctuating and partly high plankton/benthos-ratios for neritic settings. A final pronounced peak in plankton occurrence is associated with strong decrease of benthic biota, suggesting anoxic conditions in the outer neritic environment. Several local negative δ13C- and δ18O-excursions can be identified in the section. The upper, most pronounced and consistent negative δ13C excursion is tentatively linked to global carbon isotope excursion K (ETM3) based on the biostratigraphic constraints.