- Usage in publication:
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- Windy Hills Gneiss
- Modifications:
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- Original reference
- Dominant lithology:
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- Gneiss
- Amphibolite
- AAPG geologic province:
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- Piedmont-Blue Ridge province
Summary:
Pg. 11-12, 39; W.S. Schenck and others, 2000, Delaware Geol. Survey, Geol. Map. Ser., no. 10, scale 1:36,000. Windy Hills Gneiss of Wilmington Complex. Thinly interlayered, fine- to medium-grained hornblende-plagioclase amphibolite, biotite gneiss, and felsic gneiss, possibly metavolcanic. Metamorphic grade decreases from granulite facies in the northeast to amphibolite facies toward the southwest. Rocks previously included in amphibolite A and B of the Wilmington Complex and in James Run Formation. Is much older than the James Run at its type locality [459 +/-5 Ma, Horton and others, 1998, GSA Abs. w/Prog., v. 30, p. 126]. Is correlated (geol. map) with Big Elk Member of James Run Formation of Cecil County, Maryland. Age of igneous crystallization is [Early Ordovician], based on isotopic dating. Zircons from a sample of felsic biotite-gedrite-cordierite gneiss (locality Cb35-a) yielded a U-Pb age of 481 +/-4 Ma (J.N. Aleinikoff, USGS, personal commun., 2000).
Source: Publication.
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
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