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| Jeffersoniana #19 (Free PDF Download) |
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Free Jeffersoniana #19 Download
ABSTRACT
Three unusual thrombolites were collected in June 2008 from the Late Cambrian Conococheague Formation at the Boxley Materials Blue Ridge Quarry in Bedford County, Virginia. These specimens are isolated low domes with a thrombolitic core and a pustulate, stromatolitic outer layer. The two largest domes have a distinctive thickened rim around their margins. There are apparent traces across the upper surfaces of the domes that may indicate grazing by invertebrates.
The overall structure and morphology of the Boxley specimens is reminiscent of modern thrombolites forming in Lake Thetis, a saline lake in southwestern Australia. The low domes and thickened rims in Lake Thetis specimens seem to be a result of growth in a protected setting, with shallowing water levels. Based on the similarities with the Lake Thetis specimens, the Boxley thrombolites may have formed in a protected lagoonal setting with gradually dropping water levels, followed by relatively rapid inundation and burial.
*Jeffersoniana #19 is distributed only as a free electronic download (PDF). If an alternative format is necessary, please email books@vmnh.virginia.gov or call 276-634-4141 (ext. 4319).
**Unauthroized copying or distribution of this item is prohibited. |
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