Sedimentation and diagenesis at a Late Cambrian biomere extinction horizon

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6598007

Grimm, K A; Miller, J F; Taylor, J F

The base of the Eurekia apopsis Subzone of the Saukia Zone, slightly below the present Cambrian-Ordovician boundary, has been interpreted as a biomere extinction crisis for trilobites and conodonts. This boundary can be recognized to within two centimeters in platform carbonates in Utah, Nevada, Texas, and Oklahoma. Regional stratigraphy in West Utah reveals that this extinction horizon occurs within a shoaling upward sequence in which sedimentation was predominantly episodic. Shallow subtidal sedimentation, producing bioturbated mixed-skeletal wackestones and graded intraclastic grainsupportstones (tempestites), shifted to peritidal sedimentation through the boundary interval and for the duration of the E. apopsis Subzone. Associated lithofacies include sponge-dominated thrombolite mounds with tidal channels, sublittoral stromatolite reefs, and a restricted marine lagoon. The base of the E. apopsis Subzone in West Utah is a sharp contact but is interpreted as neither a disconformity nor a surface of subaerial exposure. In Texas, this boundary is a planar disconformity between biosparites. The bed underlying this surface displays features that reflect wholesale aragonite dissolution followed by two stages of inferred meteroic phreatic cementation. The surface is well washed and provided a clean substrate for epitaxial cementation across the boundary. The overlying basal strata of the E. apopsis Subzone are cemented with marine phreatic non-ferroan calcite and contain faunas that are strikingly dissimilar to those below.

• Research Organization: Univ. of Wisconsin, Madison (USA)
• OSTI ID: 6598007
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CARBONATE ROCKS
DIAGENESIS
PALEONTOLOGY
PETROLOGY
STRATIGRAPHY
NEVADA
OKLAHOMA
TEXAS
UTAH
BIOLOGICAL EXTINCTION
CAMBRIAN PERIOD
GEOLOGIC HISTORY
LITHOLOGY
SEDIMENTATION
FEDERAL REGION IX
FEDERAL REGION VI
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGY
NORTH AMERICA
PALEOZOIC ERA
ROCKS
SEDIMENTARY ROCKS
USA
580100* - Geology & Hydrology- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)