Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico:  a restudy of DSDP Leg 77 Sites 536 and 540.
Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time.  Five units are recognized:  (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion.  (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age.  (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami.  (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave.  (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age.  Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.
Alvarez
W
W
Department of Geology and Geophysics, University of California, Berkeley 94720, USA.
Smit
J
J
Lowrie
W
W
Asaro
F
F
Margolis
S V
SV
Claeys
P
P
Kastner
M
M
Hildebrand
A R
AR
D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis / Q000737:chemistry; D056890:Eukaryota; D005580:Fossils; D055593:Geological Phenomena; D005844:Geology; D005898:Glass / Q000032:analysis*; D006205:Haiti; D007495:Iridium / Q000032:analysis*; D008386:Marine Biology; D008800:Mexico; D008903:Minerals / Q000032:analysis; D009791:Oceanography; D009792:Oceans and Seas; D010163:Paleontology; D011791:Quartz / Q000032:analysis*; D016082:Solar System
D008903:Minerals; D011791:Quartz; D007495:Iridium; D002119:Calcium Carbonate