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Abstract: Paleomagnetic Characterization of the Proposed Texas Low-Level Radioactive Waste Repository, Sierra Blanca, West Texas

M. J. Whitelaw, J. A. Raney, M. L. W. Jackson

The results of paleomagnetic studies conducted on cores collected from a proposed site for the Texas low-level radioactive waste repository are presented. The proposed site is located 6 km east of Sierra Blanca, west Texas, and occurs within the Eagle Flat basin. A total of 648 oriented samples from nine cores and a single trench were collected for magnetostratigraphic study. The study was highly successful, producing high-fidelity records that allow correlation between cores, and a determination of the age of the basin.

The longest core, YM#17/53 (672 ft), penetrated Cretaceous bedrock and preserves a magnetostratigraphic record, which indicates that sedimentation was initiated in the Eagle Flat basin by approximately 12.0 m.y. Cores YM#4 (249.5 ft) and YM#6 (250.5 ft), both also to Cretaceous bedrock, preserve records of the Brunhes, Matuyama, Gauss, and Gilbert Chrons, indicating that sedimentation was initiated in these shallower parts of the basin by 5.0 Ma, and perhaps as early as 5.5 Ma. Thickness variations of characteristic magnetozones preserved within the nine cores suggest that basinal sedimentation rates have varied considerably, both within and between cores. The Brunhes Chron is represented by anomalously short magnetozones at the top of each core, suggesting radical changes in depositi nal regime over the last 780 k.y.

AAPG Search and Discovery Article #90980©1994 AAPG Southwest Section Meeting, Ruidoso, New Mexico, April 24-26, 1994