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2 Acta Geologica Polonica

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Cenomanian through Lower Coniacian events in the Upper Cretaceous of Saxony, Germany

100%

Troger K.

2004

tom Vol. 54, no. 4

629-638

The event sequence recognised in the Cenomanian through basal Coniacian (Late Cretaceous) of the Elbe Valley is compared with the event stratigraphic scheme worked out in NW Germany. The following events, recognised originally in Lower Saxony, and subsequently in other Cretaceous areas of north-western Europe, were found in Saxony: Schloenbachia / virgatus eustatoevent (Lower Cenomanian); Chondrites ecoevent, Puzosia eustatoevent and plenus eustatoevent (Upper Cenomanian); hattini ecoevent, Mytiloides ecoevents, hercynicus ecoevent, Hyphantoceras ecoevent, Didymotis ecoevents and waltersdorfensis ecoevent (Turonian); erectus ecoevent, hannovrensis ecoevent, and incostans ecoevent (Lower Coniacian). Both the oxic/anoxic Cenomanian/Turonian boundary event and the facies change at the base of the Metoicoceras geslinianum Zone are recognisable. With the exception of the Mytiloides ecoevents, recorded in all facies types, all the events are well developed only in the marly-silty facies.Local events, specific to the Cretaceous of Saxony are: the Late Cenomanian Pennrich event, known from the Sudetic area, and the Middle Turonian rhynchonellid events, occurring in sandy and transitional facies between Pirna and Bad Schandau.

The Turonian/Coniacian (T/C) boundary in the Upper Cretaceous of the Elbe Valley/Saxony (Germany)

63%

Troger K. , Wejda M.

1998

tom Vol. 48, no. 4

387-394

Three lithofacies characterize the Turonian/Coniacian sequences in the Upper Cretaceous of the Elbe Valley. The marly lithofacies, between Weinbohla - Dresden - Heidenau, consists of marls and calcareous clays (Strehlen Formation). A transitional lithofacies, with alternations of marls, clays and blocky sandstones, follows to the southeast (area between Rosenthal - Pirna - Lohmen). A sandy lithofacies, with blocky sandstones, is developed even farther to the southeast (Elbsandsteingebirge). The T/C boundary is situated in the lower part of the Strehlen Formation in the marly lithofacies, known from several boreholes. Coniacian index ammonites are absent across the T/C boundary in the three investigated boreholes apart from a deformed and incomplete specimen of Placenticeras cf. orbignyanum (GEINITZ). Therefore, bivalves must be used to place the T/C boundary. The Didymotis event II (Dresden-Marienhof Borehole), with Cremnoceramus waltersdorfensis (ANDERT), lies at the top of the Upper Turonian M. scupini Zone. The rarity or absence of the bivalve Didymotis in the Dresden-Blasewitz and Graupa boreholes is caused by facies changes. The FAD of Cremnoceramus rotundatus (TROGER non FIEGE), especially the C. rotundatus Event (Graupa Borehole, Hinterjessen Marl), can be used to place the T/C boundary. A small interval below the FAD of C. rotundatus and above the Didymotis II event, which may belong to the basal Coniacian, yields Cremnoceramus waltersdorfensis (ANDERT), Cremnoceramus waltersdorfensis hannovrensis (HEINZ), Mytiloides carpathicus (SIMONESCU) and Placenticeras cf. orbignyanum (GEINITZ). In the sandy lithofacies fossils are rare. It is not possible to place the boundary in either the Herrenleite Sandstone or in sandstone d. In the marly lithofacies of the Upper Cretaceous of Saxony bracketing of the T/C boundary is possible by means of planktonic foraminifera. It is possible to identify the evolution of planoconvex double-keeled globotruncanids of the Dicarinella hagni - Dicarinella primitiva - Dicarinella concavata group from the Upper Turonian. In the Dresden-Blasewitz and Dresden-Marienhof boreholes this group is represented in the T/C boundary interval by Marginotruncana paraconcavata PORTHAULT and Dicarinella cf concavata (BROTZEN). They are of rare occurrence because they are facies controlled. It is not possible to recognize the boundary between the scheegansi and concavata zones because of the restricted occurrence and rarity of the index forms in the investigated sections. In the Dresden-Blasewitz and Dresden-Marienhof boreholes the benthonic species Stensioeina granulata (OLBERTZ) was identified.