Title of article :
Micropaleontology and sedimentology across the Cretaceous/Tertiary boundary at La Ceiba (Mexico): impact-generated sediment gravity flows
Author/Authors :
Arz، Helge W. نويسنده , , J.A. and Arenillas، نويسنده , , I and Soria، نويسنده , , A.R and Alegret، نويسنده , , L and Grajales-Nishimura، نويسنده , , J.M and Liesa، نويسنده , , C.L and Meléndez، نويسنده , , A and Molina، نويسنده , , E and Rosales، نويسنده , , M.C، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2001
Pages :
15
From page :
505
To page :
519
Abstract :
A micropaleontological and sedimentological study across the Cretaceous/Tertiary boundary-officially Cretaceous/Paleogene (K/P) boundary from the La Ceiba section (Mexico) was performed to examine the K/P planktic foraminiferal biostratigraphy, the sedimentology of a controversial K/P clastic unit, and the benthic and planktic foraminiferal assemblages turnover across this boundary. The clastic unit is stratigraphically placed between two pelagic marly units (Méndez and Velasco Formations) and displays a fining-upward gradation similar to a turbidite sequence. This K/P clastic unit contains a basal subunit consisting of calcareous marls rich in millimeter-sized spherules (microtektites) altered to clay minerals, abundant detrital quartz, mica minerals, and shocked quartz. According to the K/P stratotype definition from El Kef (Tunisia), the K/P boundary at La Ceiba must be placed at the base of the clastic (microspherules) unit since it is equivalent to the base of the boundary clay at El Kef. A short hiatus affects the lower part of the Danian, including the Guembelitria cretacea and Parvularugoglobigerina eugubina biozones and the lower part of the Parasubbotina pseudobulloides biozone. Nearly all commonly recorded Maastrichtian planktic foraminiferal species were found in the uppermost Maastrichtian interval, and there was no support for a gradual mass extinction pattern in the terminal Cretaceous. Benthic foraminiferal assemblages suggest that the La Ceiba section was deposited at lower bathyal depths. Oscillating megatsunami waves and/or a sea-level lowstand cannot explain the nature of the clastic deposits because of the observed deposition paleodepth (more than 1000 m). There is also evidence that the clastic unit was deposited under a high-sedimentation rate in upper flow regimes and that was emplaced as a single-pulse event as turbidites. This datum and other sedimentological features support a sediment gravity flow genesis for the clastic unit. All these results are consistent with the K/P impact theory and the asteroid impact on the Yucatan Peninsula.
Keywords :
Impact generated sediment gravity flows , Cretaceous/Tertiary boundary , La Ceiba
Journal title :
Journal of South American Earth Sciences
Serial Year :
2001
Journal title :
Journal of South American Earth Sciences
Record number :
2239059
Link To Document :
بازگشت