Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.
Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.
复制标题
墨西哥湾白垩纪-第三纪边界的近端撞击沉积物：对 DSDP Leg 77 站点 536 和 540 的重新研究。
作者：
W. Alvarez;Jan Smit;William Lowrie;F. Asaro;Stanley V. Margolis;Philippe Claeys;Miriam Kastner;Alan R. Hildebrand
对墨西哥湾东南部深海钻探项目现场536和540的重新研究提供了在第三纪-第三纪边界时间发生巨浪的证据。五个单位得到承认：（1）塞诺曼期灰岩位于一个白垩纪最高的五个阶段缺失的间断之下，可能是由于灾难性的K-T侵蚀。(2)厚45 m的含砾泥岩代表可能为K-T时代的海底滑坡。(3)目前层状砂岩，超过2.5米厚，含有异常铱，玻璃陨石玻璃，和冲击石英;它被解释为喷出物从附近的撞击坑，在深海海底改造所产生的海啸。(4)一个50厘米的石灰质泥岩包含小白垩纪寒武纪有孔虫和Ir峰的间隔被解释为白垩纪物质的冲击产生的波悬浮的粉粒级。(5)含基底第三纪有孔虫的钙质泥岩和Ir异常的最上部尾部覆盖在扰动层段上，将撞击和波浪事件定为K-T边界年龄。像海地的Beloc和墨西哥的Mimbral一样，536和540号地点与附近希克苏鲁布陨石坑的大K-T年龄撞击一致。
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.