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;5km thick continental crust（De Paolo et al.,1983;Mont...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;5km thick continental crust（De Paolo et al.,1983;Montanari et al.,1983;Hildebrand and Boynton,1988,1990）.Evidence for mafic/ultramafic target rocks was reinforced by discovery of chromites,some with shock planar deformation features（PDF）,in impact layer samples from sites in southern Colorado and eastern Wyoming（Bohor et al.,1990）.However,until now it was unclear whether the chromites originated with an impactor or with terrestrial target rocks.To this end,high-precision 54Cr/52Cr isotope ratios were measured on KT boundary chromites along with known terrestrial chromites.We find a terrestrial 54Cr/52Cr ratio in KT boundary chromites from impact layer samples collected at the above sites over the last several years（Fig.1）.Ejected terrestrial chromites suggest the impact sampled terrestrial mafic and/or ultramafic target rocks not known to exist in the Chicxulub target area.展开更多
文摘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;5km thick continental crust（De Paolo et al.,1983;Montanari et al.,1983;Hildebrand and Boynton,1988,1990）.Evidence for mafic/ultramafic target rocks was reinforced by discovery of chromites,some with shock planar deformation features（PDF）,in impact layer samples from sites in southern Colorado and eastern Wyoming（Bohor et al.,1990）.However,until now it was unclear whether the chromites originated with an impactor or with terrestrial target rocks.To this end,high-precision 54Cr/52Cr isotope ratios were measured on KT boundary chromites along with known terrestrial chromites.We find a terrestrial 54Cr/52Cr ratio in KT boundary chromites from impact layer samples collected at the above sites over the last several years（Fig.1）.Ejected terrestrial chromites suggest the impact sampled terrestrial mafic and/or ultramafic target rocks not known to exist in the Chicxulub target area.
