TY - BOOK
T1 - Late Ordovician brachiopods from West-central Alaska
T2 - systematics, ecology and palaeobiogeography
AU - Mac Ørum Rasmussen, Christian
AU - Harper, David A. T.
AU - Blodgett, Robert B.
PY - 2012/3
Y1 - 2012/3
N2 - A silicified brachiopod fauna from the White Mountain area, west-central Alaska is catalogued and interpreted within a palaeoecological and biogeographical context. This area is situated within the Nixon Fork Subterrane of the Farewell Terrane; its origin and timing of final docking with Laurentia has been much debated. The current study adds new faunal data to the debate. The fauna was collected from three localities; a main locality in the upper Darriwilian - lower Sandbian and two additional middle-upper Katian localities. All three localities contain a predominantly deep-water autochthonous fauna that was mixed with an allochthonous fauna as a result of down-slope movement of turbidity currents at the shelf-break to slope transition. Deposition of the autochthonous fauna was within Benthic Assemblage zones 4-5, possibly shallower in the Katian localities. The three localities comprise a very diverse fauna consisting of nearly 100 taxa. Of these the genera Callositella cheeneetnukensis, Duolobella sandiae, Palaeowingella farewellensis and Transridgeia costata are new. In addition nine new species are described: Anisopleurella tricostata, Christiania aseptata, Craspedelia potterella, Gelidorthis perisiberiaensis, Leptaena (Septomena) alaskensis, Oanduporella kuskokwimensis, Ptychoglyptus alaensis, Sowerbyella (Rugosowerbyella) praecursor and Sowerbyella (S.) rectangularis. Furthermore, Leptellina pulchra and Strophomena planobesa are revised and assigned to Anoptambonites and Tetraphalerella, respectively. The large number of new taxa indicates an endemic fauna that has affinities with the cosmopolitan deep-water faunas of this time interval. However, the fauna demonstrates great similarity with those from the Eastern Klamath Terrane, northern California and the Jones Ridge area on the Alaska - Yukon border, as well as faunas of Eastern USA. As the Laurentian affinities are all based on deep-water taxa, it may not indicate particularly close faunal links between the Farewell Terrane and Laurentia. More noteworthy, several taxa indicate faunal exchange, in some cases at the species level, between peri-Laurentian terranes such as the Midland Valley Terrane and the palaeocontinents of Siberia and even Baltica. Notably the link to Siberia is strengthened by two cluster analyses conducted for the studied localities, indicating that the Farewell Terrane probably is derived from Siberia but by the Late Ordovician was in a sufficiently isolated position to develop a whole suite of endemic taxa.
AB - A silicified brachiopod fauna from the White Mountain area, west-central Alaska is catalogued and interpreted within a palaeoecological and biogeographical context. This area is situated within the Nixon Fork Subterrane of the Farewell Terrane; its origin and timing of final docking with Laurentia has been much debated. The current study adds new faunal data to the debate. The fauna was collected from three localities; a main locality in the upper Darriwilian - lower Sandbian and two additional middle-upper Katian localities. All three localities contain a predominantly deep-water autochthonous fauna that was mixed with an allochthonous fauna as a result of down-slope movement of turbidity currents at the shelf-break to slope transition. Deposition of the autochthonous fauna was within Benthic Assemblage zones 4-5, possibly shallower in the Katian localities. The three localities comprise a very diverse fauna consisting of nearly 100 taxa. Of these the genera Callositella cheeneetnukensis, Duolobella sandiae, Palaeowingella farewellensis and Transridgeia costata are new. In addition nine new species are described: Anisopleurella tricostata, Christiania aseptata, Craspedelia potterella, Gelidorthis perisiberiaensis, Leptaena (Septomena) alaskensis, Oanduporella kuskokwimensis, Ptychoglyptus alaensis, Sowerbyella (Rugosowerbyella) praecursor and Sowerbyella (S.) rectangularis. Furthermore, Leptellina pulchra and Strophomena planobesa are revised and assigned to Anoptambonites and Tetraphalerella, respectively. The large number of new taxa indicates an endemic fauna that has affinities with the cosmopolitan deep-water faunas of this time interval. However, the fauna demonstrates great similarity with those from the Eastern Klamath Terrane, northern California and the Jones Ridge area on the Alaska - Yukon border, as well as faunas of Eastern USA. As the Laurentian affinities are all based on deep-water taxa, it may not indicate particularly close faunal links between the Farewell Terrane and Laurentia. More noteworthy, several taxa indicate faunal exchange, in some cases at the species level, between peri-Laurentian terranes such as the Midland Valley Terrane and the palaeocontinents of Siberia and even Baltica. Notably the link to Siberia is strengthened by two cluster analyses conducted for the studied localities, indicating that the Farewell Terrane probably is derived from Siberia but by the Late Ordovician was in a sufficiently isolated position to develop a whole suite of endemic taxa.
M3 - Book
SN - 9781118384176
T3 - Fossils and Strata
BT - Late Ordovician brachiopods from West-central Alaska
PB - Wiley-Blackwell
ER -