Paleozoic strata of the Dyckman Mountain area, northeastern Medfra quadrangle, Alaska

Professional Paper 1615
By: , and 



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
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