Are Displaced Miogeoclinal Rocks present in metamorphic pendants in the central and southern Sierra Nevada
Abstract
In high flux arcs regional tectonic events are largely preserved in small host rock pendants. It has been proposed in the Sierran arc, California that a block of passive margin sediments (Snow Lake block) has been displaced to its present location from an uncertain origin. Members of the USC undergraduate team research program have studied two pendants, the Boyden Cave pendant and further north, the Iron Mountain pendant to determine if passive margin sediments exist in these areas. The Boyden Cave pendant was composed of Cretaceous metasedimentary rocks and metavolcanics potentially resembling a Mesozoic overlap sequence seen elsewhere in Sierran pendants on top of the passive margin metasediments. Further west, the area contained limestones and very pure quartzites of unknown ages that could have miogeoclinal origins. The Iron Mountain pendant has been mapped also as part of the Snow Lake Block, but we believe this to be incorrect. The Iron Mountain pendant is composed of a mix of volcanic, volcaniclastic, and sedimentary rocks associated with a hypabyssal pluton and may represent an old caldera, possibly of Mesozoic age. If correct this pendant represents some of the most western and potentially youngest Mesozoic volcanics preserved in this part of the arc. Zircon dating and geochemistry underway will allow us to better constrain the likely ages and protolith of quartzites from Boyden Cave and if the Iron Mountain pendant represents a Cretaceous caldera complex.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.V43E2319G
- Keywords:
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- 1100 GEOCHRONOLOGY;
- 8000 STRUCTURAL GEOLOGY