Collaborative Research: Antarctic Cretaceous-Cenozoic Climate, Glaciation, and Tectonics: Site Surveys for Drilling from the edge of the Ross Sea Shelf

Luyendyk等人：该奖项由极地计划办公室南极地质和地球物理计划提供，支持罗斯海中南部和东部海洋地质和地球物理的合作研究计划。该项目将进行从罗斯冰架到其下海底钻探的现场调查，有关东南极冰盖和西南极冰盖演变、南极气候、全球海平面和西南极裂谷系构造历史的许多悬而未决的问题都可以通过钻探罗斯海海底来解决。白垩纪和新生代早期的气候数据缺乏南极洲的这一部门。气候问题包括：在白垩纪晚期有冰吗？在古新世-始新世全球变暖期间，南极的气候如何？新生代南极冰川作用是什么时候开始的，冰川是什么时候到达海岸的，又是什么时候向边缘推进的？罗斯海大陆架在晚白垩世是非海洋的吗？它是什么时候变成海洋的？构造问题包括：罗斯海裂谷白垩纪伸展的时间是什么;它位于哪里？地下室的组成和结构是什么？阿代尔海槽影响扩展的时空界限在哪里？另一个钻探目标是对东部盆地和中央海槽中绘制的RSU 6不整合面的沉积剖面进行采样和定年，以解决有关其年龄和区域范围的问题。深海钻探项目（DSDP）第28航次于20世纪70年代初在四个钻探地点完成了取样，但采收率较低，没有对新生代早期进行取样。其他钻探仅限于罗斯海西部的麦克默多海峡地区，其结果可与维多利亚陆地盆地相关联，但不能向东跨越基底高点。此外，尚未对新生代早期和白垩纪岩石进行取样。一个新的机会正在发展，从罗斯冰架钻探。这是罗伯茨角钻井项目的后续项目。一个压倒一切的困难是需要在冰架下的钻探地点进行现场勘测。该项目将克服这一障碍，在中央海槽和东部海盆的罗斯冰架前部进行海洋地球物理钻探。调查将在冰架前缘以北一两公里处进行，最近的冰裂事件导致冰架边缘的位置偏南。几年后，冰架向北的推进将超过测量的位置，钻探可能完成。将使用的系统包括条带测深、重力、磁力、啁啾声纳、高分辨率地震剖面和48次地震。将采集岩芯，以获得岩土性质的样本，研究冰下架现代沉积过程，并在更深的部分暴露的位置进行调查。这项调查将包括潜在钻探地点的长剖面和详细网格。测量线将与现有的地球物理剖面和DSDP 270相联系。最近的一个事件使这一计划变得及时，那就是巨大的冰山B-15（2000年3月）和其他冰山从罗斯海东部的冰锋崩解。这次新的冰解事件和1987年的一次冰解事件暴露了16,000平方公里的海底，这些海底几十年来一直被冰架覆盖，没有被探索过。现在可以用现代地球物理方法绘制新暴露的地区的地图。该项目将绘制更远的南部和东部不整合面RSU 6以下的地质结构和地层图，研究罗斯福岛在罗斯海裂谷历史中的位置，并确定更远的南部和东部晚新生代（后RSU 6）的沉降历史。最后，该项目将观察新暴露地区冰架下的现代沉积过程。

Luyendyk et al.: OPP 0088143Bartek: OPP 0087392Diebold: OPP 0087983This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research program in marine geology and geophysics in the southern central and eastern Ross Sea. The project will conduct sites surveys for drilling from the Ross Ice Shelf into the seafloor beneath it. Many of the outstanding problems concerning the evolution of the East and West Antarctic Ice Sheets, Antarctic climate, global sea level, and the tectonic history of the West Antarctic Rift System can be addressed by drilling into the seafloor of the Ross Sea. Climate data for Cretaceous and Early Cenozoic time are lacking for this sector of Antarctica. Climate questions include: Was there any ice in Late Cretaceous time? What was the Antarctic climate during the Paleocene-Eocene global warming? When was the Cenozoic onset of Antarctic glaciation, when did glaciers reach the coast and when did they advance out onto the margin? Was the Ross Sea shelf non-marine in Late Cretaceous time; when did it become marine? Tectonic questions include: What was the timing of the Cretaceous extension in the Ross Sea rift; where was it located? What is the basement composition and structure? Where are the time and space limits of the effects of Adare Trough spreading? Another drilling objective is to sample and date the sedimentary section bounding the mapped RSU6 unconformity in the Eastern Basin and Central Trough to resolve questions about its age and regional extent. Deep Sea Drilling Project (DSDP) Leg 28 completed sampling at four drill sites in the early 1970's but had low recovery and did not sample the Early Cenozoic. Other drilling has been restricted to the McMurdo Sound area of the western Ross Sea and results can be correlated into the Victoria Land Basin but not eastward across basement highs. Further, Early Cenozoic and Cretaceous rocks have not been sampled. A new opportunity is developing to drill from the Ross Ice Shelf. This is a successor program to the Cape Roberts Drilling Project. One overriding difficulty is the need for site surveys at drilling locations under the ice shelf. This project will overcome this impediment by conducting marine geophysical drill site surveys at the front of the Ross Ice Shelf in the Central Trough and Eastern Basin. The surveys will be conducted a kilometer or two north of the ice shelf front where recent calving events have resulted in a southerly position of the ice shelf edge. In several years the northward advance of the ice shelf will override the surveyed locations and drilling could be accomplished. Systems to be used include swath bathymetry, gravity, magnetics, chirp sonar, high resolution seismic profiling, and 48 fold seismics. Cores will be collected to obtain samples for geotechnical properties, to study sub-ice shelf modern sedimentary processes, and at locations where deeper section is exposed.This survey will include long profiles and detailed grids over potential drill sites. Survey lines will be tied to existing geophysical profiles and DSDP 270. A recent event that makes this plan timely is the calving of giant iceberg B-15 (in March, 2000) and others from the ice front in the eastern Ross Sea. This new calving event and one in 1987 have exposed 16,000 square kilometers of seafloor that had been covered by ice shelf for decades and is not explored. Newly exposed territory can now be mapped by modern geophysical methods. This project will map geological structure and stratigraphy below unconformity RSU6 farther south and east, study the place of Roosevelt Island in the Ross Sea rifting history, and determine subsidence history during Late Cenozoic time (post RSU6) in the far south and east. Finally the project will observe present day sedimentary processes beneath the ice shelf in the newly exposed areas.