Correlation of Tertiary Nonmarine Deposits in Alaska and Northeastern Asia1
Published:January 01, 1973
Comprehensive paleobotany studies of the major stratigraphie sections of the Tertiary nonmarine deposits of Alaska and Asia show that correlation is possible.
In Alaska, the basal Tertiary Chickaloon Formation is correlative with the Avekova Suite of Asia. Warm-temperate plant assemblages with minor quantities of subtropical plants characterized the time of deposition of these strata. The Fultonian of Alaska correlates with the lower Ravenian Tastakh Suite of Asia. This de-positional period was characterized by subtropical and tropical assemblages, but some flora represent warm-temperate trees. Both angiosperms and gymnosperms (of the latter, mainly Cupressaceae and Taxodiaceae with minor Pinaceae) are present.
The upper Kummerian Omoloy Suite is characterized by a warm-temperate flora including angiosperms (Betulaceae with minor evidence of broad-leaved trees) and gymnosperms (Pinaceae, including Ketelleria, Cedrus and Dacridium, and minor Taxodiaceae). The assemblages from the lower units of the Koynatkhun Beds resemble those of the upper Angoonian Stage in northeastern Asia, and the upper strata resemble lower Seldovian units. In Alaska, the Miocene(?) Tsa-daka Formation and the lower part of the Kenai Group are equivalents of the Omoloy.
Among the Seldovian suites—Marekane, Pekulneyveyem, Namtsy, and Mamontova Gora, and the upper Nera Beds—are found flora of coastal conifers (e.g., broad-leaved trees with minor subtropical components) and midland-upland conifers and birch and minor broad-leaved trees. The age of the Marekane Suite is confirmed by marine mollusks. In Alaska, the Kenai Group, except for the lower part, is considered to be equivalent to the named Seldovian suites.
In the Osinovskaya Member of the Homerian, Pinaceae and Betulaceae predominate, but scarce broad-leaved plants are represented.
Transitional beds characterize the upper Homerian and the lower Clamgulchian Stage of Alaska. In northeastern Asia, the following units are correlative with those transitional beds: Tirekhtyakh, Khapchan, Gu-sinka, Delyankyr, and Erman. The lower units of the Clamgulchian are similar to the Homerian, whereas middle and upper units contain boreal assemblages with a dominance of Betulaceae and Pinaceae. The age of the Erman Suite is confirmed by marine faunas. The middle Clamgulchian is correlative with the Erlernten Suite and the Impoveyem Beds of northeastern Asia. The Enemten contains Salix assemblages with Betulaceae and Pinaceae; the Impoveyem contains different genera of Pinaceae.
The evolution of the Tertiary floras in Asia proceeded from warm-temperate Paleogene floras to subtropical Eocene floras; in middle Oligocene-late Miocene time, the dominant floras were warm-temperate ones of Turgay type, which gradually became extinct. Pliocene floras were a temperate type which were ancestors of the Quaternary floras.
Figures & Tables
Following the discovery of Prudhoe Bay oil field in 1968, much attention was turned to the Arctic in the search for giant hydrocarbon accumulations. The Soviets had already proved giant reserves in their West Siberian Basin, and exploration was moving ahead quickly in the Canadian Arctic. Plans were drawn up for an AAPG Symposium on Arctic Geology and held in February 1971. Papers were selected from the Symposium for this publication and cover seven topical groupings: Regional Arctic Geology of Canada, Regional Arctic Geology of the Nordic Countries, Regional Arctic Geology of the USSR, Regional Arctic Geology of Alaska, Comparisons in the North Atlantic Borders, Evolution of the Arctic Ocean Basin, and Economics of Petroleum Exploration and Production in the Arctic.