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The mid-Cenomanian eustatic low

Hancock J.

Acta Geologica Polonica

2004

Vol. 54, no. 4

611-627

Through much of the earlier part of the Middle Cenomanian the sea-levels in western Asia, northern Europe and the Western Interior of the U.S.A. were lower than during the later Early Cenomanian and most of the later Middle Cenomanian. In north-west Europe the first sign of this Mid-Cenomanian Eustatic Low was just before the end of the Zone of Cunningtoniceras inerme. There was then an abrupt and strong fall of sea-level at the base of Milankovitch couplet C 1, early in the Subzone of Turrilites costatus. Sea-level continued to be low through couplets C 1 to C 3 for some 60,000 years: this is the Mid-Cenomanian Regressive Trough. In western Germany it has been distinguished as the Primus Event. In north Texas and the Western Interior of the U.S.A. the Trough occurred in the Zone of Conlinoceras tarrantense which can be dated as 95.78 [plus-minus] 0.61 Ma.A later regressive trough occurred at the start of the Subzone of Turrilites acutus, which is marked by the Mid-Cenomanian Event in Germany. The overall lower sea-level from late in the Zone of C. inerme to early in the Subzone of T. acutus is the Mid-Cenomanian Eustatic Low. It lasted some 300,000 years.

Santonian ammonite stratigraphy of the Munster Basin, NW Germany

Kaplan U., Kennedy W.

Acta Geologica Polonica

2000

Vol. 50, no. 1

99-117

The upper Coniacian and Santonian ammonite stratigraphy of the Munster Basin, Westphalia, NW Germany, is described in the context of regional litho-, inoceramid- and sequence stratigraphy. The Sphenoceramus pachti & S. cardissoides Zone, previously regarded as basal Santonian, is placed in the uppermost Coniacian. The Lower Santonian corresponds to the Cladoceramus undulatoplicatus Zone, the lower Middle Santonian to the Cordiceramus cordiformis Zone. The Sphenoceramus pinniformis Zone spans the upper Middle Santonian to the lower Upper Santonian. The succeeding Sphenoceramus patootensiformis Zone corresponds approximately to the Marsupites testudinarius crinoid zone of the upper Upper Santonian. Occurrences of the belemnite Gonioteuthis are discussed. The ammonite occurrences are documented in the context of inoceramid and where possible, belemnite and crinoid stratigraphy. A Texanites (Texanites) pseudotexanus Zone extends from the uppermost M. subquadratus Zone to the Upper Coniacian/Lower Santonian boundary. The Kitchinites emscheris Zone comprises the Lower and Middle Santonian. The Upper Santonian corresponds to the Boehmoceras arculus Zone. The ammonite faunas are predominately endemic from the Upper Coniacian to the Middle Santonian. Only the Upper Santonianyields supraregional and even global ammonite taxa such as Boechmoceras arculus and B. krekeleri, which co-occur with the widespread crinoids Uintacrinus socialis and Marsupites testudinarius. Sequence boundaries, followed by transgressive pulses, are identified in the uppermost Coniacian, with a subordinate event in the Middle Santonian, the most significant event in the basal Upper Santonian and the last in the Lower Campanian. Ammonite occurrences are clearly related to the sequences recognized.