The Cretaceous-Tertiary boundary (KTB) transition in NE Brazil

B. Gertsch, Gerta Keller, T. Adatte, Z. Berner

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

At 7800 km from Yucatan the Cretaceous-Tertiary boundary (KTB) transition of the Poty Quarry, NE Brazil, is the most distant locality with published accounts of Chicxulub impact-tsunami deposits, impact spherules and Ir anomaly. New investigations based on sedimentology, biostratigraphy, mineralogy and geochemistry fail to confirm these reports. Latest Maastrichtian planktic foraminiferal zones CF1 below an erosive and bioturbated disconformity and early Danian zone P1a(1) above indicate a short hiatus, with the KTB clay (zone P0), the Ir anomaly and the characteristic negative δ 13 C excursion missing. The disconformity coincides with the globally recognized latest Maastrichtian sea-level fall. Above the disconformity, an upward-fining micro-conglomerate with abundant reworked Cretaceous foraminifera, sub-angular phosphate clasts, calcitic and phosphatic spheroids along with an early Danian zone P1a(1) assemblage is interpreted as a gravity-flow deposit. Common spheroids throughout the late Campanian-Maastrichtian appear to be chamber infillings of the benthic foraminifer Dentalina alternata. Minor Ir anomalies in thin clay layers of zone Pla and no evidence of the Chicxulub impact reveal that the Poty Quarry section remains a very important example of the complex global environmental and sea-level changes observed in KT sequences from North America to Central America that are commonly misinterpreted as impact-tsunami events.

Original languageEnglish (US)
Pages (from-to)249-262
Number of pages14
JournalJournal of the Geological Society
Volume170
Issue number2
DOIs
StatePublished - Mar 1 2013

All Science Journal Classification (ASJC) codes

  • Geology

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