Basin and Range Geoscientific Experiment (BARGE)

Wernicke BARGE是对地球大陆岩石圈区域的综合、多学科研究，该区域在高度扩展的地形和构造稳定的块体之间存在突然边界。本研究的主要研究目的是利用岩石圈最上部大应变梯度的“自然实验”，了解莫霍等深部不连续对伸展的响应，从而量化岩石圈大水平应变与均衡控制下各层次垂直运动的关系。通过在盆地和山脉省的地质测绘，已经确定了一些这样的地区。其中，科罗拉多高原的西部边缘是实现我们目标的最合适的例子。它有以下优点：(1)唐突；(2)地质背景表明简单的伸展前地壳构造；(3)熟知的大尺度伸展运动史；或许最重要的是，(4)一条适合进行深部地球物理研究的大型内陆水道——米德湖（Lake Mead），它恰好横越了边界，在这个位置上，地质学研究可以在伸展过程中确定地壳隆起的边界。主要研究人员正在整合地质和地质年代学研究，海洋多通道地震反射剖面，协调陆地和海洋地震折射剖面，以及重力建模，以揭示岩石圈对严重拉伸应变响应的运动学和动力学。驳船项目地质部分的主要目标已接近完成。主要目的是通过地质测绘、岩石学和热年代学研究以及元古代结晶基底的古地磁研究，表征地壳中金丘构造块体的大规模前伸展构造。BARGE的地球物理部分比地质部分晚一年完成。由于无法预见的后勤延误，地球物理实验将在1994年初进行，即在研究的地质部分的赠款到期后将近一年。该项目涉及对BARGE地质部分的适度延续，主要有两个目标：1)对金丘和邻近的小断块进行额外的地质测绘，特别是块体的最上部，主要上地壳断裂带与高分辨率反射线相交；2) PI参与地球物理实验，包括解释结果和准备发表稿件。＊＊＊

9219939 Wernicke BARGE is an integrated, multi-disciplinary investigation of a region of the earth's continental lithosphere where an abrupt boundary exists between highly extended terrain and a tectonically stable block. The main research objective of this study is to use the "natural experiment" of a large strain gradient in the uppermost part of the lithosphere to understand how the Moho and other deep discontinuities respond to extension, thus quantifying how large horizontal strains of the lithosphere relate to vertical motions at various levels, controlled by isostasy. A number of such regions have been identified by geological mapping in the Basin and Range province. Of these, the western margin of the Colorado Plateau is the best suited example for accomplishing our objective. It has the virtues of (1) abruptness; (2) a geologic setting that indicated a simple pre-extensional crustal structure; (3) a well-understood large-scale extensional kinematic history; and perhaps most importantly, (4) a large inland waterway suitable for deep geophysical studies, Lake Mead, that transects the boundary in precisely the location where geological studies can place bounds on crustal uplift during extension. The Principal Investigators are integrating geological and geochronologic studies, marine multi-channel seismic reflection profiling, coordinated land and marine seismic refraction profiling, and gravity modeling to unravel the kinematic and dynamics of the lithosphere's response to severe extensional strain. The main objective of the geologic portion of the BARGE project are nearing completion. The primary objective was to characterize the large-scale pre-extensional configuration of the Gold Butte structural block in the crust through geologic mapping, a petrologic and thermochronometic studies, and paleomagnetic studies of the Proterozoic crystalline basement that comprises the bulk of the block. The geophysical component of BARGE was fun ded a year later than the geological portion. Due to unforseen logistical delays, the geophysical experiment will be conducted in early 1994, nearly a year after the expiration of the grant for the geological portion of the research. This project involves a modest continuation of geological portion of BARGE with two principal objectives: 1) Additional geologic mapping of the Gold Butte and neighboring small fault blocks, in particular the uppermost part of the block where major upper crustal fault zones intersect the high-resolution reflection lines; 2) Participation of the PI in the geophysical experiment, including interpretation of results and preparation of manuscripts for publication. ***