Paper No. 11
Presentation Time: 10:45 AM


ULICNY, David1, GROCKE, Darren R.2, CECH, Stanislav3, LAURIN, Jiri1, JARVIS, Ian4, OLDE, Kate4, TRABUCHO-ALEXANDRE, Joao5, SVABENICKA, Lilian3 and PEDENTCHOUK, Nikolai6, (1)Institute of Geophysics, Czech Academy of Sciences, Bocni II/1401, Prague, 14131, Czech Republic, (2)Department of Earth Sciences, Durham University, South Road, Durham, DH1 3LE, United Kingdom, (3)Czech Geological Survey, Klarov 3, Prague, 118 21, Czech Republic, (4)School of Geography, Geology and the Environment, Kingston University, London, Penrhyn Road, Kingston-Upon-Thames, KT12EE, United Kingdom, (5)Institute of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, Netherlands, (6)School of Environmental Sciences University of East Anglia, Norwich, NR4 7TJ, United Kingdom,

A basin-scale record of high-frequency transgressive-regressive fluctuations of Turonian age in the Bohemian Cretaceous Basin (Central Europe) has previously been interpreted as being influenced by short-term eustasy. In our study, nearshore siliciclastic strata in two separate sub-basins are correlated to a multi-stratigraphic dataset from a new research core (Bch-1) drilled in offshore marine sediments of the central basin. A high-resolution δ13Corg record from the Bch-1 core is presented along with major- and minor-element proxies, TOC, carbonate contents, terrestrial to marine palynomorph ratios, and detailed macro- and microfossil biostratigraphy. The 400 m thick Turonian through Lower Coniacian interval permits correlation to the highest-resolution C-isotope curves available: all carbon-isotope events demonstrated by δ13Ccarb studies in the British Chalk, NW Germany and other reference sections are recognised in the δ13Corg curve from Bch-1, thus offering a significantly improved resolution of temporal correlation of relative sea-level changes and other events. A number of short-term, basin-wide regressions in the Bohemian Cretaceous Basin show a recurrence interval of 100 kyr or less , implying probably a glacio-eustatic mechanism. This is an order of magnitude shorter than the timing of sea-level falls inferred from the New Jersey margin and the Apulian platform, previously interpreted as driven by glacioeustacy. The relatively small magnitude of the Bohemian Basin sea-level falls, typically 10-20m, and generally below 40 m, indicates that the 2.4 Myr period suggested by others to generate 3rd -order cycles, is too long to be the principal cycle generating unconformities in tectonically active basins, where the rate of eustatic fall must exceed the subsidence rate. Unconformities in low-accommodation settings such as passive margins must represent amalgamated records of multiple cycles of sea-level fluctuations of 100 kyr scale, recognizable only in high-resolution datasets from expanded basinal sections. This research was supported by the Czech Science Foundation (GACR) grant No. P210-10-1991.