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18 March 2010
Transect Trip 27: fluvial overbank deposits
Over on the far right by Chuck Bailey (yellow shirt) you can see the crescent-shaped profile of a river channel (gray color). To the left of that, you can see levee deposits, and beyond that (to the left) crevasse splay deposits and the floodplain (dark red mudstones). This is in the Hampshire Formation, part of the Acadian “clastic wedge.”
Transect Trip 26: Bouma sequence
Here we are in the Brallier Formation, a Devonian turbidite sequence. Prominent in the middle of this photo is the Bouma “C” horizon with the cross- bedding.
Transect Trip 25: sheared microbrachiopods
This one is also from the Millboro Formation: itty bitty brachs (not too much oxygen in those depths for building up big body sizes) that have been sheared during Alleghanian deformation.
Transect Trip 24: soft sediment deformation
This photo is from the Millboro Formation: mostly deep water black shale, but with the occasional heavy turbidite coursing in and settling its bulk down on the squishy mud beneath. Some folks on our trip suggested these might be seismites: soft sediment deformation resulting from earthquake-induced vibration.
Transect Trip 22: S-fold breached by thrust fault
Oriskany sandstone, folded into an S-fold, then snapped down the middle!
Transect Trip 21: hanging wall anticline
Hoo-hoo! An anticline in the hanging wall of a thrust fault in the Valley & Ridge. This is the redbeds of the latest-Ordovician Juniata Formation. Lynn Fichter for scale.
Transect Trip 20: chlorite slickensides
This is a nice sample of slicks. On the other side, burrows! I like that: a primary structure on one face, a secondary structure on the opposite side.
Transect Trip 19: Germany Valley
Looking north along the Germany Valley, which lies in the core of a breached plunging anticline. The topography is defined by the erosion-resistant ridge of Tuscarora Sandstone. This is the Wills Mountain Anticline. The Tuscarora is Silurian; at the bottom of the valley (core of the anticline), you find Ordovician carbonates.
Transect Trip 18: Judy Gap
Fault-duplicated double section of the (Silurian aged) erosion-resistant Tuscarora Sandstone:
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.