The Togiak-Tikchik complex of southwestern Alaska, a replacement for the Gemuk Group: Stratigraphic nomenclature that has outlived its time

Abstract

During early exploratory reconnaissance of southwestern Alaska in the 1940s and 1950s, the term "Gemuk Group" was used to name a varied assemblage of sedimentary and volcanic rocks in southwestern Alaska. Throughout the 1950s and early 1960s, the name was broadly applied in the region; yet by the end of the 1960s, it was no longer in use, and later maps assigned the rocks originally in this unit to various informal units and, later, to various terranes. The name "Gemuk Group" is herein abandoned, and the rocks previously assigned to the Gemuk Group, a diverse and structurally complex assemblage, are renamed the "Togiak-Tikchik Complex.

Geologic map of Alaska

“…Miller and others (2007) reexamined and mapped the area where the Gemuk Group was originally defined by Cady and others (1955) in the northwestern Taylor Mountains and southwestern Sleetmute quadrangles. Following abandonment of the name "Gemuk Group," (Wilson and Coonrad, 2005), Miller and others (2007) newly defined these rocks as the Restricted Gemuk Group. Miller and others (2007) Box and others (1993) reported poorly preserved radiolarians of Early Cretaceous and Jurassic age from rocks correlated with this unit in the Bethel quadrangle.…”

Bedrock geologic map of the northern Alaska Peninsula area, southwestern Alaska

“…data, 1958) to become a catch-all unit for many Paleozoic to Cretaceous rocks in southwestern Alaska. Wilson and Coonrad (2005) discussed the history of usage of the term Gemuk Group and formally abandoned the Gemuk Group as a stratigraphic unit and term; rocks that were traditionally included in this unit were assigned to the Togiak-Tikchik Complex. Within this map area, rocks that range from early Paleozoic to Cretaceous are included in the Togiak-Tikchik Complex, a structural assemblage of a variety of rock units; rudimentary subdivision of these rocks into informal rock units is made here on the basis of available data, especially the field notes of J.M.…”

“…(Hoare and Coonrad, 1978) (Sainsbury and MacKevett, 1965). In the Cinnabar Creek area, occurs near the top of now abandoned Gemuk Group section (Wilson and Coonrad, 2005).…”

“…data, 1958). The name "Gemuk Group" was abandoned by Wilson and Coonrad (2005) when they recognized that the rock units constitute a structural assemblage of poorly known lithologic packages; they redescribed and renamed the assemblage of lithologies the "Togiak-Tikchik Complex." In the map area, these rocks include abundant chert and graywacke and lesser limestone, basalt, and other volcanic and sedimentary rocks.…”

“…Unit, as originally defined as the Gemuk Group, consisted chiefly of dense, dark, massive siltstone having interbeds of chert, volcanic rocks, limestone, graywacke, and breccia. The name Gemuk Group was formally abandoned and the assemblage was subsequently redefined as the Togiak-Tikchik Complex in recognition of its structural character (Wilson and Coonrad, 2005 Argillite and graywacke (Lower Cretaceous to Upper Triassic)-Gray to gray-green argillite, cherty argillite, graywacke, and minor mudstone, tuffaceous sandstone, and chert. These rocks primarily occur in the northwestern part of the map area and were originally defined as constituting a major proportion of the type area of the now abandoned Gemuk Group.…”