Paleozoic strata of the Dyckman Mountain area, northeastern Medfra quadrangle, Alaska
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- Document: Start page in larger work
- Larger Work: Geologic studies in Alaska by the U.S. Geological Survey, 1998
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Abstract
Paleozoic rocks in the Dyckman Mountain area (northeastern Medfra quadrangle; Farewell terrane) include both shallowand deep-water lithologies deposited on and adjacent to a carbonate platform. Shallow-water strata, which were recognized by earlier workers but not previously studied in detail, consist of algal-laminated micrite and skeletal-peloidal wackestone, packstone, and lesser grainstone. These rocks are, at least in part, of Early and (or) Middle Devonian age but locally could be as old as Silurian; they accumulated in shallow subtidal to intertidal settings with periodically restricted water circulation. Deepwater facies, reported here for the first time, are thin, locally graded beds of micrite and calcisiltite and subordinate thick to massive beds of lime grainstone and conglomerate. Conodonts indicate an age of Silurian to Middle Devonian; the most tightly dated intervals are early Late Silurian (early to middle Ludlow). These strata formed as hemipelagic deposits, turbidites, and debris flows derived from shallow-water lithologies of the Nixon Fork subterrane. Rocks in the Dyckman Mountain area are part of a broader facies belt that is transitional between the Nixon Fork carbonate platform to the west and deeper water, basinal lithologies (Minchumina “terrane”) to the east. Transitional facies patterns are complex because of Paleozoic shifts in the position of the platform margin, Mesozoic shortening, and Late Cretaceous-Tertiary disruption by strike-slip faulting.
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Paleozoic strata of the Dyckman Mountain area, northeastern Medfra quadrangle, Alaska |
| Series title | Professional Paper |
| Series number | 1615 |
| DOI | 10.3133/70180930 |
| Year Published | 2000 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Denver, CO |
| Contributing office(s) | Alaska Science Center, Central Mineral and Environmental Resources Science Center |
| Description | 15 p. |
| Larger Work Type | Report |
| Larger Work Subtype | USGS Numbered Series |
| Larger Work Title | Geologic studies in Alaska by the U.S. Geological Survey, 1998 (Professional Paper 1615) |
| First page | 43 |
| Last page | 57 |
| Country | United States |
| State | Alaska |
| Other Geospatial | Dyckman Mountain area, Medfra quadrangle |
| Google Analytic Metrics | Metrics page |