Lower Devonian conodonts from the Karheen Formation, southeastern Alaska

Abstract

Conodonts from the eastern end of Heceta Island and from a small island of the Ham Island group in the Karheen Passage, southeastern Alaska, include Ozarkodina eberleini n. sp., Eognathodus sulcatus Philip, Pandorinellina exigua philipi (Klapper), Icriodus angustoides castilianus Carls, and Pelekysgnathus klamathensis Savage. Both localities are in the Karheen Formation. The age of the faunas is considered to be early Pragian (Faunal units 5 and 6 of Klapper et al.). The early form of Eognathodus sulcatus predominates in the Heceta Island collection from Locality 1, suggesting Fauna 5, and the late form predominates in the Ham Island collection from Locality 2, suggesting Fauna 6. A middle Early Devonian age for the faunas is significant in that Locality 1 is also USGS locality 2689 which previously has yielded brachiopod and coral faunas considered to be of Late Silurian age.

Revision of the rhynchonellid and atrypid brachiopods from the lower Pragian (Devonian) of Southeast Alaska (Heceta Island)

“…1). This important locality was originally thought to be late Silurian in age (Kirk & Amsden, 1952), but subsequently revised to an early Pragian age (Savage 1977(Savage , 1981Blodgett et al 2010;Baranov &Blodgett 2011, 2012, andherein). The material used in this study was collected by R.B.…”

“…This locality is the same as USGS locality 2689-SD [= field locality 47-AH-R120(F) of G. Donald Eberlein which he and his USGS field party collected in 1947 during regional geologic mapping]. The geographic coordinates given for this locality in Savage (1977) is latitude 55°48´N and longitude 133°21´W. This exposure of limestone, shaly limestone and shale was included within the red-bed clastic unit named the Karheen Formation by Eberlein & Churkin (1970), and is surrounded along the adjoining shoreline to the north and south by typical exposures consisting of red colored sandstones of the Karheen Formation (see Savage 1981, fig.…”

“…Subsequently, Blodgett et al (2010) suggested placing this exposure rather in the overlying Devonian age Wadleigh Limestone, and having it fault-bounded to the north and south by structurally discordant beds of the latest Silurian age Karheen Formation. conodonts, with only detailed taxonomic descriptions or illustrations being provided for on the brachiopods (Kirk & Amsden 1952, Savage 1981, and herein), rugose corals (Merriam in Oliver et al 1975), and conodonts (Savage 1977). Kirk & Amsden (1952) in their monographic study "Upper Silurian brachiopods of Southeastern Alaska" described brachiopods from seven U.S. Geological Survey collections, one of which (USGS locality 2689-SD) (see Fig.…”

“…Kirk & Amsden (1952) in their monographic study "Upper Silurian brachiopods of Southeastern Alaska" described brachiopods from seven U.S. Geological Survey collections, one of which (USGS locality 2689-SD) (see Fig. 1 for location) was subsequently shown to be early Pragian (Middle Early Devonian) in age by Savage (1977Savage ( , 1981. The six other collections are correctly assigned a late Silurian age.…”

“…Later, Savage (1977Savage ( , 1981 described conodonts and brachiopods, respectively, from USGS locality 2689-SD. Among the conodonts (Savage 1977) reported the zonal subspecies-index of the lower Pragian Eognathodus sulcatus sulcatus Philip and the following species: Ozarkodina eberleini sp.…”