--> Abstract: Controls on Clastic Sequences in an Intracontinental Seaway: The Bohemian Cretaceous Basin, Central Europe, by David Ulicny, Jiri Laurin, and Stanislav Cech; #90039 (2005)

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Controls on Clastic Sequences in an Intracontinental Seaway: The Bohemian Cretaceous Basin, Central Europe

David Ulicny1, Jiri Laurin2, and Stanislav Cech3
1 University of Western Ontario, London, ON
2 Czech Academy of Sciences, Prague, Czech Republic
3 Czech Geological Survey, Prague, Czech Republic

The Bohemian Cretaceous Basin of Central Europe acted as fault-controlled, shallow seaway formed due to mid-Cretaceous reactivation of basement strike-slip fault zones that coincided with a eustatic flooding of large parts of Europe. Between two major flooding episodes in the early Turonian and early Coniacian, eight major clastic wedges prograded from the marginal fault zones, comprising large numbers of high-frequency sequences dominated by sandy to gravelly deltas and shorefaces passing into offhore fines. During this time interval, marine currents of inferred tidal origin, flowing along the basin axis, redistributed the sand along delta fronts. The current activity also led to separation and removal of mud-grade suspension, via hypopycnal plumes.

The geometry of the clastic sequences was controlled by the interplay between long and short-term transgressive-regressive cycles, a shift in source areas, and by local basin-margin topography. Thus, a range of delta types formed, from thin, shallow-water types to Gilbert-type deltas, up to 100 m thick. While global sea-level trends were clearly involved in the Early Turonian relative sea-level high and Middle Turonian low, increased fault activity during the Late Turonian strongly influenced regional accommodation by acceleration of subsidence and narrowing of the main clastic depocenter. Growth of an intrabasinal high at this time contributed to formation of a separate depocenter filled by hemipelagic carbonates in a close proximity to coarse nearhsore clastics. The complexity of stratigraphic response to a number of controls in a relatively "simple“ basin underlines the importance of detailed, three-dimensional sequence correlation in understanding basin evolution.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005