Impacts, Tsunamis, and the Haitian Cretaceous-Tertiary Boundary Layer
Impacts, Tsunamis, and the Haitian Cretaceous-Tertiary Boundary Layer
复制标题
影响、海啸和海地白垩纪-第三纪边界层
作者：
F. Maurrasse;G. Sen
在Beloc组（海地南部）的第三系-第三系边界的标志层包含丰富的粗粒微玻璃陨石和少量的冲击石英颗粒的底部。上部由中粒泥灰岩组成，混汞微玻璃陨石透镜体和细粒泥灰岩透镜体遍布其间。野外和岩相学观察，以及南极有孔虫的分布表明，该床是由一系列复杂的事件形成的。附近的一次火流星撞击产生了微玻璃陨石，这些陨石沉降下来，在底部形成了一个几乎纯净的层。具有极高地球外成分的蒸发物质最后与碳酸盐沉积物一起沿着沉降。整张床变得稀稀拉拉。随后，另一个重大的破坏性事件，也许是一场巨大的海啸，部分地改变了最初的存款。原始标志层的粘性碎片与外来物质混合，重新沉积为透镜体。这个过程也可能导致白垩纪和第三纪微体化石的进一步混合，正如在Beloc和其他地方所观察到的那样。
The marker bed at the Cretaceous-Tertiary boundary of the Beloc Formation (southern Haiti) contains abundant coarse-grained microtektites and minor amounts of shocked quartz grains in the basal part. The upper part is composed of medium-grained marl with amalgamated microtektite lenses and finer-grained marl lenses disseminated throughout. Field and petrographic observations, and the distribution of planktonic foraminifera suggest that the bed formed from a complex sequence of events. A bolide impact nearby produced microtektites that sett1led to form a nearly pure layer at the base. Vaporized materials with anomalously high extraterrestrial components settled last, along with carbonate sediments. The entire bed became sparsely consolidated. Subsequently, another major disruptive event, perhaps a giant tsunami, partly reworked the initial deposit. Cohesive fragments of the original marker bed mixed with exotic materials were redeposited as lenticular bodies. This process also may have caused further mixing of Cretaceous and Tertiary microfossils, as observed at Beloc and elsewhere.