A small outcrop showing two compositional members of the late Ordovician Georgetown Intrusive Suite.
Which came first, the light-colored one or the dark-colored one?
Outcrop on the bike path where it enters Zoo property, near upstream end of Beach Drive Tunnel.
Outcrop on the bike path where it crosses through the National Zoo.
Faulted dike and sheared gabbro in Georgetown Intrusive Suite.
Devonian shale w/ turbidites, carbonate nodules, and itty-bitty brachiopod fossils.
Fossils from this site:
Carbonate nodules from this site:
Lower Martinsburg Formation limy shale exposed near Tumbling Run section.
Trace fossils in Devonian mudrock.
Devonian sediment-mining feeding traces preserved in Devonian-aged mudrock, Fort Valley, Virginia.
Cambrian quartz sandstone from the Blue Ridge; showing primary sedimentary features.
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