Early and Middle Devonian shelf-slope transition, southern Mahogany Hills, Eureka County, Nevada

Journal Article · Tue Oct 01 04:00:00 EDT 1991 · Mountain Geologist; (United States)

OSTI ID:5738324

Schalla, R A ^[1]; Benedetto, K M ^[2]

---

1. Balcron Oil, Billings, MT (United States)
2. Western Resource Associates, Inc., Reno, NV (United States)

In the southern Mahogany Hills the abrupt lateral transition between the lower McColley Canyon Formation (Kobeh Member) and the Beacon Peak (Sevy) Dolomite (Lower Devonian), and the pinch out of the Oxyoke Canyon Sandstone into the upper Sadler Ranch Formation (Middle Devonian), document lithofacies relationships between carbonate shelf and slope deposits. The McColley Canyon/Beacon Peak transition is marked by a change from thin-bedded dolomite and limestone with occasional chert nodules and scattered fossil material, to poorly bedded, largely unfossiliferous, sandy dolomite. This change suggests shallowing and concomitant circulation restriction at the shelf edge during the early stages of platform (ramp) development. Data from measured sections, in the vicinity of Combs Peak, suggest that the location of the shelf edge' was the result of both transgression and paleotopographic relief on the subjacent platform. A thin oxidized zone at the top of the Beacon Peak Dolomite on Combs Peak, interpreted as a paleosol, indicates subaerial exposure of the outer shelf prior to renewed transgression and deposition of the Bartine Member of the McColley Canyon Formation. The location of the carbonate shelf edge is further documented by the westward pinch out of unfossiliferous, arenaceous dolomites of the Oxyoke Canyon Sandstone into fossiliferous, fore-slope dolomites of the Sadler Ranch Formation. This facies change is the result of regression, which caused shoaling along the shelf edge. Lithofacies relationships Mahogany Hills document two transgressive-regressive cycles, and help to establish the location of an Early and Middle Devonian carbonate shelf-slope transition in southern Eureka County.

• OSTI ID: 5738324
• Journal Information: Mountain Geologist; (United States), Journal Name: Mountain Geologist; (United States) Vol. 28:4; ISSN MOGEA; ISSN 0027-254X
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200 -- Petroleum-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000* -- Geosciences
CARBONATE MINERALS
CARBONATE ROCKS
CHERT
CONTINENTAL MARGIN
CONTINENTAL SHELF
CONTINENTAL SLOPE
DEPOSITION
DEVELOPED COUNTRIES
DEVONIAN PERIOD
DOLOMITE
EXPLORATION
FEDERAL REGION IX
FOSSILS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
LIMESTONE
MINERAL RESOURCES
MINERALS
NEVADA
NORTH AMERICA
PALEOZOIC ERA
PETROLEUM DEPOSITS
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
USA