A new species of the genus Droharhynchia Sartenaer is established from lower Eifelian strata of west-central Alaska and the northwestern Brooks Range of Alaska. Droharhynchia rzhonsnitskayae n. sp. occurs in the Cheeneetnuk Limestone of the McGrath A-5 quadrangle, west-central Alaska, and the Baird Group of the Howard Pass B-5 quadrangle, northwestern Alaska. These occurrences extend the lower biostratigraphic range of both the genus and the subfamily Hadrorhynchiinae into the Eifelian. They also suggest close geographic proximity of the Farewell terrane of southwestern and west-central Alaska and the Arctic Alaska superterrane of northern Alaska during Devonian time.
AbstractHolocene tephrostratigraphy in Alaska provides independent chronology and stratigraphic correlation in a region where reworked old (Holocene) organic carbon can significantly distort radiocarbon chronologies. Here, we present new glass chemistry and chronology for Holocene tephras preserved in three Alaskan lakes: one in the eastern interior and two in the southern Brooks Range. Tephra beds in the eastern interior lake-sediment core are correlated with the White River Ash and the Hayes tephra set H (~4200–3700 cal yr BP), and an additional discrete tephra bed is likely from the Aleutian arc/Alaska Peninsula. Cryptotephras (nonvisible tephras) found in the Brooks Range include the informally named “Ruppert tephra” (~2700–2300 cal yr BP) and the Aniakchak caldera-forming event II (CFE II) tephra (~3600 cal yr BP). A third underlying Brooks Range cryptotephra is chemically indistinguishable from the Aniakchak CFE II tephra (4070–3760 cal yr BP) and is likely to be from an earlier eruption of the Aniakchak volcano.
Depositional framework and regional correlation of pre-Carboniferous metacarbonate rocks of the Snowden Mountain area, central Brooks Range, Northern Alaska
