Premium
Regarding an Oceanic Crust/Upper Mantle Geochemical Signature at the KT Boundary: If not from Chicxulub Crater, then Where Did it Come from?
Author(s) -
OLDS Peter,
SLEEP Norm
Publication year - 2017
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.13164
Subject(s) - geology , ophiolite , oceanic crust , impact crater , lithosphere , mantle (geology) , crust , paleontology , convergent boundary , continental crust , plate tectonics , north american plate , subduction , tectonics , physics , astronomy
Evidence for a mantle and/or basaltic component in KT boundary distal ejecta is apparently inconsistent with ejection from Chicxulub Crater since it is located on ∼35 km thick continental crust (DePaolo et al., 1983; Montanari et al., 1983; Hildebrand and Boynton, 1988, 1990). This evidence, along with ejected terrestrial chromites (Olds et al., 2016) suggest the impact sampled terrestrial mafic and/or ultramafic target rocks which are not known to exist in the Chicxulub target area. Possible resolutions to the paradox are: 1) the existence of an unmapped/unknown suture in Yucatan Platform basement, 2) an additional small unmapped/unknown impact site on oceanic lithosphere, or 3) an additional large impact on oceanic lithosphere or continental margin transitional to oceanic lithosphere. The third hypothesis is elaborated here since: 1) Ophiolites nearest to Chicxulub crater are found in Cuba and apparently were obducted in latest Cretaceous/earliest Danian times (García‐Casco, 2008), inconsistent with the documented Eocene collision of Cuba with the Bahamas platform; and 2) Cuba hosts the world's thickest known KT boundary deposits (Iturralde‐Vinent, 1992; Kiyokawa et al., 2002; Tada et al., 2003). These and geometric considerations suggest oceanic crust and upper mantle rock, exposed as ophiolite in the Greater Antilles island chain, marks the rim of a roughly 700 km diameter impact basin deformed and dismembered from an originally circular form by at least 50 million years of left‐lateral shear displacement along the North American‐Caribbean transform plate boundary.