The Cenomanian-Turonian (late Cretaceous) anoxic event in SW England : evidence from Hooken Cliffs near Beer, SE Devon
Jarvis, Ian; Carson, Greg; Hart, Malcolm; Leary, Paul; Tocher, Bruce
Newsletters on Stratigraphy Volume 18 Number 3 (1988), p. 147 - 164
published: Apr 5, 1988
ArtNo. ESP026001803006, Price: 29.00 €
The Cenomanian-Turonian boundary succession is described for marginal limestone and chalk facies near Beer, SE Devon. The macrofaunal, foraminiferal and dinoflagellate biostratigraphy of this succession is presented and carbon stable-isotope data are used to constrain the position of the Cenomanian-Turonian Oceanic Anoxic Event (OAE) in the sequence. The stage boundary is precisely defined by the appearance of mytiloid inoceramid bivales and species of the ammonite Watinoceras immediately above a regionally-developed hardground surface (Haven Cliff Hardground). A major carbon isotope excursion with a shift of up to +2.0‰ δ13C (PDB) occurs immediately above a second hardground, located a short distance below the stage boundary. The base of the isotope excursion coincides exactly with the base of the "Hedbergella" archaeocretacea Partial Range Zone in the section studied. Correlation with coeval basinal chalk sequences in SE England indicates that the beginning of the OAE is represented only by reworked sediment in SE Devon. Major changes in the structure of planktonic foraminiferal assemblages in these 'shallow water' sediments during the OAE, are related to the development of oxygen-depleted deep-water masses in oceanic areas.