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The transgressive development in the Lower and Middle Cenomanian of the Salzgitter area (N-Germany) recorded by sea level-controlled eco- and litho-events

by Gundolf Ernst & Ursula Rehfeld, Berlin

ERNST, G. & REHFELD, U. (1997): The transgressive development in the Lower and Middle Cenomanian of the Salzgitter area (N-Germany) recorded by sea level-controlled eco- and litho-events. - Freiberger Forschungshefte C 468. - Paläontologie, Stratigraphie, Fazies, Heft 5. - S. 79-107. - Freiberg 1997.

Abstract

The development of the Cenomanian transgression in the eastern Lower Saxony Basin is documented by lithological and ecological events in the key Baddeckenstedt section and nine reference sections.

Onlap is documented by three main pulses in the Lower and Middle Cenomanian, which likewise define third-order sequences. Sequences are herein introduced as the ultimus, Mariella and primus sequence. Onlap is reflected by lithological and faunal characteristics. These are 1) increase in the carbonate content, 2) changes from wacke-and packstones, dominated by calcispheres and benthic foraminifera to those with predominating calcareous nannoplankton, and a sudden increase of planktonic foraminifera (p/b break), 3) depletion of the macrofauna and 4) changes in the allochthonite facies from shallow water coquina tempestites to deeper water calciturbidite deposits.

Stratigraphy, lithology, and faunal content of the three sequences are described and interpreted with respect to palaeoenvironmental conditions and sea level development.

The sequence boundaries of the ultimus and primus sequences are marked by interregionally correlatable hiatuses. Lowstand and early transgressive deposits are characterized by glauconitic marls or arenitic inoceramid wacke-and packstones ("Grobkreide"). The early periods of each sequence are marked by characteristic pulse faunas.

All three transgressive pulses (sequences) can be traced to northern Thuringia and Westphalia.
The three Lower to Middle Cenomanian sequences are followed by two further sequences in the Upper Cenomanian, introduced as the Pycnodonte and plenus sequences.