--> ABSTRACT: Stratigraphic Architecture of Paris Basin Cretaceous Chalk: From High Resolution Stratigraphy to Seismic Image, by M. Mettraux, F. Guillocheau, A. Schwab, and P. Homewood; #91021 (2010)

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Stratigraphic Architecture of Paris Basin Cretaceous Chalk: From High Resolution Stratigraphy to Seismic Image

METTRAUX, M.,  F. GUILLOCHEAU, A. SCHWAB, and P. HOMEWOOD

Detailed field and analytical sedimentology provided understanding of facies changes as a function of accommodation cycles in Campanian chalk at Boran and Precy quarries near the Oise river, north of Paris.

Ten facies were identified in the field and were validated by thin section and SEM analysis. Patterns of chert distribution and abundance, early cemented firm-grounds to hard-grounds, and evidence of current reworking, allowed interpretation in terms of progradation, aggradation and sediment starvation.

Depositional environments were generally below storm and fairweather wave-base, but the tops of some shallowing upward cycles were reworked by current activity. Cherts are more abundant in progradational phases of higher frequency cycles, and a major hardground marks the turn-around of longer term decreasing to increasing accommodation.

Regional correlation of larger scale sequences was carried out across the Paris Basin on wireline logs, after calibration with the outcrop-based stratigraphic model. Higher gamma-ray signatures are thought to correspond to increased clay content and are related to regional transgression.

The abundance and distribution of chert may explain amplitude changes observed on regional seismic in the Paris Basin. Progradational intervals with higher concentrations of chert should create continuous reflections on the seismic line, but of variable amplitude due to the spacing between individual chert layers. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.