10.6084/m9.figshare.3453233.v1
B. Gertsch
B.
Gertsch
G. Keller
G.
Keller
T. Adatte
T.
Adatte
Z. Berner
Z.
Berner
The Cretaceous–Tertiary boundary (KTB) transition in NE Brazil
Geological Society of London
2016
impact
clay
Danian zone P 1a assemblage
Cretaceous
spheroid
transition
disconformity
Poty Quarry section
Danian zone P 1a
δ 13 C excursion
benthic foraminifer Dentalina alternata
KT
Minor Ir anomalies
Chicxulub
NE Brazil
Ir anomaly
KTB
Maastrichtian planktic foraminiferal zones CF 1
Geology
2016-06-21 11:14:40
Dataset
https://geolsoc.figshare.com/articles/dataset/The_Cretaceous_Tertiary_boundary_KTB_transition_in_NE_Brazil/3453233
<p>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<sup>13</sup>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 <em>Dentalina alternata</em>. 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.
</p>