Regarding an Oceanic Crust/Upper Mantle Geochemical Signature at the KT Boundary: If not from Chicxulub Crater, then Where Did it Come from?


Peter OLDS;Norm SLEEP;College of Alameda;Stanford University;


College of Alameda;Stanford University;


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~35km thick continental crust(De Paolo 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-Caribbeantransform plate boundary.




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Total: 9 articles

  • [1] Antonio Garcia-Casco;Manuel Iturralde-Vinent;James Pindell, Latest Cretaceous Collision/Accretion between the Caribbean Plate and Caribeana: Origin of Metamorphic Terranes in the Greater Antilles, International Geology Review,
  • [2] D.J. DePaolo;;F.T. Kyte;;B.D. Marshall;;J.R. O'Neil;;J. Smit, Rb-Sr, Sm-Nd, K-Ca, O, and H isotopic study of Cretaceous-Tertiary boundary sediments, Caravaca, Spain: evidence for an oceanic impact site, Earth and Planetary Science Letters, Earth and Planet (Earth and Planet)
  • [3] Alan R. Hildebr;;William V. Boynt, Proximal Cretaceous-Tertiary Boundary Impact Deposits in the Caribbean, Science, Science (Science)
  • [4] Aless;;ro Montanari;; Richard L. Hay;; Walter Alvarez;; Frank Asaro;; Helen V. Michel;; Luis W. Alvarez;;Jan Sm, Spheroids at the Cretaceous-Tertiary boundary are altered impact droplets of basaltic composition, Geology, The Journal of Geology (The Journal of Geology)


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