cross-stratification – Sedimentary Geology

Bed D, Wilkins Peak Member, Green River Formation, WY

March 25, 2020March 25, 2020 by Michael Smith, posted in Sedimentary Geology

Lacustrine, deltaic, and fluvial strata of the Wilkins Peak Member of the Green River Formation, Firehole Canyon, Wyoming.

Pennsylvanian Morgan Formation, Yampa River Canyon, Dinosaur National Monument, CO

March 24, 2020April 10, 2020 by Michael Smith, posted in Sedimentary Geology

morgan_yampa_canyon

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morgan_yampa_canyon2

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Cyclothems of the Pennsylvanian Morgan Formation exposed in the canyon of the Yampa River, Dinosaur National Monument, Colorado. Alternating intervals of blue-gray limestone and orange cross-stratified sandstone record repeated glacio-eustatic sea level fluctuations. Photosets acquired from raft.

Pennsylvanian Hermosa Group, Highway 550, San Juan Mountains, Colorado

March 23, 2020March 24, 2020 by Michael Smith, posted in Sedimentary Geology

hermosa_hw550

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Roadcut of Pennsylvanian Hermosa Group strata exposed between Molas Pass and Engineer Pass along US 550, San Juan Mountains, Colorado. Amalgamated cross-bedded, lenticular arkosic sandstone bodies and fine-grained mudstone partings with complex bedding relationships.

Upper Cambrian Jordan Sandstone and Ordovician Oneota Dolomite, Weaver, MN

March 22, 2020March 24, 2020 by Michael Smith, posted in Sedimentary Geology

weaver_jordan_oneota

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Roadcut of Late Cambrian Jordan Sandstone and overlying Ordovician Oneota Dolomite along Wabasha County 26, near Weaver, MN, illustrating large-scale crossbeds and unconformable formation boundary.

Upper Cambrian Franconia Formation, La Crosse, WI

March 21, 2020March 24, 2020 by Michael Smith, posted in Sedimentary Geology

franconia_lacrosse

franconia_lacrosse_closeup

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Cross-bedded glauconitic sandstone of the Franconia Formation (Tunnel City Group in local lore) exposed on Grandad Bluff, La Crosse, WI.

Late Cambrian Jordan Sandstone, HW14 roadcut near Lewiston, MN

March 20, 2020March 24, 2020 by Michael Smith, posted in Sedimentary Geology

lewiston_jordan

reduced file size version (more functional for some computers): lewiston_jordan_reduced

Large roadcut of Late Cambrian Jordan Sandstone and overlying Ordovician Oneota Dolomite between Stockton and Lewiston, MN, illustrating low-angle bedding, intraclasts, and several scales of cross-stratification.