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Jurassic Chronostratigraphic Database and the TimeScale Creator Visualization System

Ogg J., Przybylski P.

Volumina Jurassica

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2009

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Vol. 7, no. 1

175-179

EN

A joint project of the International Commission on Stratigraphy (ICS) and CHRONOS database program is to provide detailed global and regional “reference” scales of Earth history. Such scales integrate biostratigraphy (zones, datums for marine and terrestrial realms), sea-level (curves, sequences), geochemistry (trends, events), magnetic polarity chrons and astronomical cycles. The current Jurassic scale contains over 1000 events and zones correlated to Tethyan and Boreal ammonite zones with approximate numerical ages from Geologic Time Scale 2004 (Gradstein et al. 2004). This public database will be progressively enhanced through the efforts of the Jurassic Subcommission of the ICS and by other stratigraphic and regional experts. On-screen display and production of usertailored time-scale charts is provided by the TimeScale Creator, a Java package freely available from the ICS Subcommission for Stratigraphic Information or the TS-Creator websites (http://stratigraphy.science.purdue.edu or www.tscreator.org). After specifying the time interval and vertical scale, a user selects a subset of stratigraphic columns and trends. In addition to screen views and a scalable-vector graphics (SVG) file for importation into popular graphics programs, the on-screen display also has “hot-curser-points” to open windows providing additional information on events, zones and boundaries. The database and visualization package are envisioned as a convenient reference tool, chart-production assistant, and a window into the geologic history of our planet.

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Jurassic Chronostratigraphic Charts and a Display Interface. 1. Hettangian through Aalenian. 2. Bajocian through Tithonian

Przybylski P., Ogg J.

Volumina Jurassica

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2006

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Vol. 4, no. 1

199-199

EN

A joint project of the International Commission on Stratigraphy (ICS) and CHRONOS database program is to provide detailed global and regional “reference” scales of Earth history. Such scales integrate biostratigraphy (zones, datums for marine and terrestrial realms), sea-level (curves, sequences), geochemistry (trends, events), magnetic polarity chrons and astronomical cycles. These summarize our current consensus on the inter-calibration of events, their relationships to international divisions of geologic time and their estimated numerical ages. An initial Phanerozoic database (about 9000 events and zones in April 2006) includes definitions of geologic stages, major zonations and markers of all significant fossil groups, primary and secondary magnetic polarity scales, and other stratigraphic information. Annotations on each entry include source, reliability, selected taxonomic notes, inter-calibrations, and methods of interpolating numerical age. This database will be enhanced through the efforts of the subcommissions of the ICS and other stratigraphic and regional experts. A primary source for the Jurassic was the extensive “Mesozoic and Cenozoic Sequence Chronostratigraphic Framework of European Basins” chart series of inter-calibrated bio-, magneto-, chemoand sequence stratigraphy (Hardenbol et al. 1998) which had been calibrated to the geologic time scales of 1995. We recalibrated all these chronostratigraphic and sequence stratigraphy events to Geologic Time Scale 2004 (Gradstein et al. 2004) and included selected post-1995 biostratigraphic schemes, marker events and geochemistry correlated to Tethyan and Boreal ammonite zones. On-screen display and production of user-tailored time-scale charts is provided by the Time-Scale Creator, a JAVA package available from the ICS/CHRONOS websites (www.stratigraphy.org or www.chronos.org). After specifying the time interval and vertical scale, a user selects a subset of stratigraphic columns and trends. In addition to screen views and a scalable-vector graphics (SVG) file for importation into popular graphics programs (e.g., Adobe Illustrator), the on-screen display has “hot-curser-points” to open windows providing additional information on events, zones and boundaries. The database and visualization package are envisioned as a convenient reference tool, chart-production assistant, and a window into the geologic history of our planet. We present sample output for the Jurassic portion as a pair of large-format charts: Hettangian-Aalenian by Ogg and Przybylski, and an accompanying poster for Bajocian-Tithonian by Przybylski and Ogg.

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Geologic Time Scale 2004 – Why, How, and Where Next!

Gradstein F., Ogg J.

Volumina Jurassica

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2006

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Vol. 4, no. 1

167-168

EN

This lecture reviews Geologic Time Scale 2004 (Gradstein et al. 2004), constructed and detailed by 40 geoscience specialists, and indicates how it will be further refined. Since Geologic Time Scale 1989 by Harland et al. many developments have taken place: 1. Stratigraphic standardization through the work of the International Commission on Stratigraphy (ICS) has greatly refined the international chronostratigraphic scale. In some cases, traditional European-based stages have been replaced with new subdivisions that allow global correlation. 2. New or enhanced methods of extracting high-precision age assignments with more realistic uncertainties from the rock record. These have led to improved age assignments of key geologic stage boundaries and other global correlation horizons. 3. Orbital tuning has greatly refined the Neogene, and improved parts of Palaeogene and Mesozoic. 4. Statistical techniques of compiling integrated global stratigraphic scales within geologic periods. Anticipated advances to the Geologic Time Scale during the next 8 years include: • a geologically realistic Precambrian scale, and stages subdivision of the Ediacaran; • formal definition of all Phanerozoic stage boundaries; • orbital tuning of polarity chrons and biostratigraphic events for entire Cenozoic and Cretaceous; • a detailed database of high-resolution radiometric ages that includes “best practice” procedures, full error analysis, monitor ages and conversion; • resolving age dating controversies (e.g., zircon statistics and possible reworking) across Devonian/Carboniferous, Permian/Triassic, and Anisian/Ladinian boundaries; • improved and standardized dating of several “neglected” intervals (e.g., Upper Jurassic – Lower Cretaceous, and Carboniferous through Triassic); • detailed integrated stratigraphy for Upper Palaeozoic through Lower Mesozoic. The geochronological science community and ICS are focusing on these issues. A modified version of the time scale to accompany the standardization (boundary definitions and stratotypes) of all stages is planned for 2008 (to be presented at the 33th International Geologic Congress in Oslo), with a totally revised version of GTS available in 2012. At the same time ICS is closely working with the Commission for the Geological Map of the World (CGMW) to standardize stratigraphic nomenclature and the colour scheme for its units.

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A potential stratotype for the Oxfordian/Kimmeridgian boundary: Staffin Bay, Isle of Skye, UK

Wierzbowski A., Coe A., Hounslow M., Matyja B., Ogg J., Page K., Wierzbowski H., Wright J.

Volumina Jurassica

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2006

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Vol. 4, no. 1

17-33

EN

A coastal exposure of the Staffin Shale Formation at Flodigarry, Staffin Bay, Isle of Skye, Scotland, UK fulfils the criteria for definition as the Global Stratotype Section and Point (GSSP) for the base of the Kimmeridgian Stage (Upper Jurassic). This marine shale succession was deposited during a long-term transgression, and is part of a complete, relatively well-expanded stratigraphic succession. A rich fauna of ammonites above and below the Oxfordian/Kimmeridgian boundary allows recognition of the Evoluta Subzone (Pseudocordata Zone) and Rosenkrantzi Subzone (Rosenkrantzi Zone) of the Subboreal and Boreal uppermost Oxfordian, and the Densicostata Subzone (Baylei Zone) and the Bauhini Zone of the Subboreal and Boreal lowermost Kimmeridgian). A suitable level for the boundary is thus marked by the replacement of the Subboreal Ringsteadia (M)/Microbiplices (m) by Pictonia (M)/Prorasenia (m), and by the first appearance of Boreal Amoeboceras (Plasmatites). Detailed study of the microfossils reveals an excellent dinoflagellate succession. A variety of stratigraphically important dinoflagellates are found, the assemblages being intermediate in character between Boreal and Subboreal ones. The magnetostratigraphic data, though rather troublesome to extract, shows a polarity pattern which can be confidently correlated to other UK boundary sections. The upper boundary of a normal magnetozone falls at, or very near, the proposed Oxfordian/Kimmeridgian boundary. The 87Sr/86Sr ratio at the boundary, based on an analysis of belemnites, lies between 0,70689 and 0,70697, averaging 0.70693. Matching worldwide trends, no distinct change in the ratio is seen across the boundary. A lack of variations in the carbon isotope composition of belemnites across the Oxfordian/Kimmeridgian boundary does not indicate perturbation in the global carbon cycle. However, high ?13C values and their scatter suggest the influence of local fractionation affecting isotope composition of dissolved inorganic carbon (DIC) in the partly isolated Boreal sea. A fall in the belemnite ?18O values in the Upper Oxfordian and Lower Kimmeridgian compared to the Mid Oxfordian suggests a slight rise in seawater temperature.