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Franciscan complex exposed in Grindstone Creek Work in Progress Tom MacKinnon t om.mackinnon@comcast.net. Grindstone Creek from Longpoint trail. Grindstone Creek area. Next slide. ppsm. 313. Ybc ?. Willows 1:100,000 Geologic map. ppv2. Hardin Hole R idge. Upstream area. ppv2.
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Franciscan complex exposed in Grindstone Creek Work in Progress Tom MacKinnon tom.mackinnon@comcast.net
ppsm 313 Ybc? Willows 1:100,000 Geologic map ppv2 Hardin Hole Ridge Upstream area ppv2 Long Point ppv3
Conglomerate • ~ 325 meters thick • 100% exposure • Deposited by sediment gravity flows • Sediment is mainly of volcanic origin • ~10-15% is graywacke/argillite
Bulk of section consists of this lithology, may be red or green
Poorly sorted pebbly siltstone/mudstone with a few clasts to 10 cm
Top of Conglomeratic section Graywack- argillite Fault contact
Volcanic sequence • ~ 400 meters thick • 100% exposure • Seamount origin? • Chert at top
Volcanic section Pillow lava?
Pebble Conglomerate Pebble Conglomerate