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

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.Supplementary materials: Data for trace elements are available at www.geolsoc.org.uk/SUP18585. research-articleResearch Article170X10.1144/jgs2012-029B. GertschThe KTB Transition in NE Brazil 2013 at Mount Royal University on June 14, 2015 http://jgs.lyellcollection.org/ Downloaded from B. GERTSCH ET AL. 250 macrofossils were noted, described and photographed for the record.Poty Well-B and the quarry exposures were sampled at 3-5 cm intervals across the suspected KTB and at 5-10 cm intervals through an event deposit (described below), bioturbated intervals and the Danian. The Maastrichtian was sampled at 20 cm intervals. In the laboratory, samples were processed for foraminiferal extraction using standard methods .The PGE, and carbon and oxygen isotopes were analysed on powdered bulk-rock samples at the Institute for Mineralogy und Geochemistry, Karlsruhe Institute of Technology, Germany. PGE were measured by isotope dilution high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) after pre-concentration and matrix reduction by Ni-fire assay (Kramar et al. 2001). Carbon and oxygen isotope measurements were carried out using a Delta V Advantage ratio mass spectrometer equipped with an online carbonate preparation line (GasBench) with separate vials for each sample (Thermo Finnigan, Bremen, Germany). The results are expressed on the V-PDB scale with standard deviations <0.05% for δ 13 C and <0.1% for δ 18 O.Mineralogical analyses were carried out at the Geological Institute of the University of Neuchâtel, Switzerland. Bulk-rock and clay mineral assemblages were analysed by X-r...

New dyrosaurid remains (Crocodyliformes, Mesoeucrocodylia) from the Paleocene of the Paraíba Basin, NE Brazil

“…The coastal region is divided into three main depocenters, Olinda, Alhandra and Miriri, from south to north respectively. The sedimentary filling of this basin is mainly composed of six formations: (1) the Coniacian?/Santonian Beberibe Formation, consisting of continental sandstones, siltstones and claystones (Beurlen, 1967a,b;Muniz, 1993;Barbosa, 2007); (2) the middle Campanian/upper Maastrichtian Itamaracá Formation, consisting of transitional and sandy limestones, marls and dolostones (Beurlen, 1967a,b;Tinoco, 1971;Souza & Lima Filho, 2005;Moura, 2007); (3) the Maastrichtian Gramame Formation, consisting of marls, limestones and marly limestones from a shallow marine platform (Beurlen, 1967a;Albertão et al, 1994;Gertsch et al, 2013); (4) the Danian Maria Farinha Formation, consisting of limestones, dolostones, marly limestones and sandy limestones formed on a shallow marine platform (Albertão et al, 1994;Stinnesbeck & Keller, 1995;Keller & Stinnesbeck, 1996;Koutsoukos, 1998;Barbosa et al, 2003;Barbosa & Lima Filho, 2006;Barbosa, 2007;Gertsch et al, 2013); (5) the Eocene Tambaba Formation, consisting of dolostones, and limestones deposits formed in reefal-lagoon systems (Correia Filho et al, 2015); and (6) the Miocene Barreiras Formation, consisting of continental sandstones, siltstones and claystones (Rossetti et al, 2011). We adopted the stratigraphic hypothesis of Correia Filho et al (2015) that proposed the Tambaba Formation as Eocene reefal carbonate deposits that was previously treated as the upper part of the Paleocene Maria Farinha Formation (Beurlen, 1967a).…”

Ostracoda and foraminifera from Paleocene (Olinda well), Paraíba Basin, Brazilian Northeast

“…Koutsoukos 1996, Gertsch et al 2013. Zeauvigerina waiparaensis occurs from the Maastrichtian (Abathomphalus mayaroensis Zone) to the late Paleocene, presenting abundance levels at the base of the Danian.…”

“…Subsequently, biostratigraphic and paleoenvironmental studies were intensified (Albertão et al 1994, Stinnesbeck and Keller 1995, Koutsoukos 1996, Gertsch et al 2013, mainly in the K-Pg boundary sequence of the Poty quarry, where the uppermost Maastrichtian Plummerita hantkeninoides Zone (CF1) was identified. In the Paleocene, the upper Pα, P1a/P1b and P1c zones were identified, above a biostratigraphic gap at the base, which was recognized by the absence of the Guembelitria cretacea Zone (P0) and the basal part of Pα (Koutsoukos 1996(Koutsoukos , 2006, which may extend up to the top of Plummerita hantkeninoides Zone (CF1) according to the studies of Gertsch et al (2013).…”

Quimioestratigrafia Isotópica (C e O) e Geoquímica de Calcários Recifais da Formação Tambaba, Bacia Paraíba, Nordeste do Brasil

“…The age proposed by Almeida (2000) for the reef limestones of the Tambaba Formation based on the fossil content differs from that proposed for the Maria Farinha Formation, which is considered Danian (Lower Paleocene) in the Olinda Sub-Basin. Compared with the Maria Farinha Formation, which has been a target of several micropaleontological studies (e.g., Albertão, 1993;Albertão & Martins Jr., 1996;Stinnesbeck & Keller, 1996;Fauth, 2000;Gertsch et al, 2013), the ages of these reef limestones have not yet been established.…”