Publication Date:
1994-09-01
Description:
Maastrichtian strata of the Zumaya-Algorta Formation of southwestern France and northeastern Spain record a major pulse of extinction among inoceramid bivalves well before the Cretaceous–Tertiary (K–T) boundary. Inoceramids are the most abundant macrofossils preserved in the study sections; at least six species ofInoceramus[I. (Endocostea)aff.I.(En.) balticusGiers,I.(En.) pteroidesGiers,I.(Platyceramus)aff.I.(Pl.) cycloidesWegner,I.(Trochoceramus) nahorianensisKociubynskij,I.(Tr.) morganiSornay, andI.(?)goldfussianusd'Orbigny] are common to abundant in lower Maastrichtian strata. However, all six species disappear over a few tens of meters of section near the base of the upper Maastrichtian, as defined by the first appearance of the planktonic foraminiferAbathomphalus mayaroensis. Tenuipteria argentea(Conrad), which has not been recovered from the lower Maastrichtian portions of the sections, occurs at low abundances through the upper Maastrichtian, disappearing within 10 cm of the K–T boundary.The mid-Maastrichtian extinction interval among inoceramids occurs within the upperGlobotruncana gansserito lowerAbathomphalus mayaroensisplanktonic foraminiferal zone, in nannofossil zone 24 to 25A, in theAnapachydiscus fresvillensisammonite zone, in magnetochron 31N, and near the base of a change in slope of the seawater strontium curve, all as recognized by previous studies in one or more of the study sections. Whereas the new data presented here are not global in extent, the observed distribution of inoceramids may be the local manifestation of global oceanic changes during the mid-Maastrichtian.
Print ISSN:
0022-3360
Electronic ISSN:
1937-2337
Topics:
Geosciences
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