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George W. Andrews

Publications and source records attributed to George W. Andrews.

At least 19 recordsLinked to original sources
USGS1990

Silicoflagellate and diatom biostratigraphy in successive Burdigalian transgressions, middle Atlantic coastal plain

The earliest Miocene strata on the Middle Atlantic Coastal Plain were deposited in two distinct marine transgressions separated by a hiatus in sedimentation of approximately one million years. The older unit (Bed 3A of the Calvert Formation and its correlatives) was deposited in a relatively restricted basin of middle Burdigalian (middle early Miocene) age. The younger unit (Bed 3B of the Calvert Formation and its correlatives) was deposited in a much more widespread basin of late Burdigalian (late early Miocene) age. The older deposit was completely overlapped by the younger deposit. These two beds of substantially differing geologic age are difficult, if not impossible, to distinguish solely by lithostratigraphy. They are, however, readily differentiated on the basis of their distinctive silicoflagellate and diatom assemblages.

Delaware, Maryland, New Jersey↗
USGS1989

The middle Eocene araphid diatom Rhaphoneis atlantica sp. Nov.: morphology and evolutionary significance

A middle Eocene deposit near the base of the continental slope 205 km east of Rehoboth Beach, Delaware, contains an assemblage of abundant diatoms, including a species herein described as Rhaphoneis atlantica. This species is substantially older than the better known species of Rhaphoneis of Miocene and younger age, and it shows morphological features that appear to be primitive for the genus. Rhaphoneis atlantica provides clues to the evolutionary history of the genus Rhaphoneis as well as other genera in the araphid subfamily Fragilarioideae.

Diatom Research↗
USGS1987

Morphology and evolutionary significance of Adoneis pacifica gen. et sp. Nov. (Fragilariaceae, Bacillariophyta), a marine araphid diatom from Chile

A new marine diatom genus and species, Adoneis pacifica G.W. Andrews and P. Rivera, has been identified in Chilean coastal waters. This taxon shows obvious affinities to the genera Rhaphoneis and Delphineis , but cannot be classified in either, as they are currently construed. Adoneis pacifica resembles Rhaphoneis in outline and to some degree in the pseudocelli, whereas it resembles Delphineis in the structure of the vela and the positioning of the apical rimoportulae. However, distinctive characters of this new monotypic genus are: (1) the usual positioning of a single rimoportula near the centre of each lateral margin of the valve, and (2) the occurrence of well organized apical pore fields (pseudocelli), in which the pores are much smaller than elsewhere on the valve. These appear to be primitive traits for the araphid diatom family Fragilariaceae, and they suggest that Adoneis pacifica may be a conservative species important in the study of the evolution of the family.

Diatom Research↗
USGS1980

Neogene diatoms from Petersburg, Virginia

Sixty-two diatom taxa have been identified from a diatomaceous sandy clay that crops out near the outlet of Wilcox Lake, Petersburg. Virginia. These diatoms are mostly cosmopolitan marine forms, but some species suggest deposition in brackish water that had a freshwater inflow. The regional stratigraphy, as well as the pelecypods and foraminifers, indicates that the beds may have been laid down in a lagoonal or estuarine environment. The diatom assemblage suggests that the deposit is of early Pliocene age, although previous biostratigraphic studies have considered it to be latest Miocene.

Virginia↗
USGS1979

Middle Miocene marine diatoms from the Hawthorn Formation within the Ridgeland Trough, South Carolina and Georgia

Diatomaceous sediments in outcrops of the Miocene Hawthorn Formation at Dawsons Landing in South Carolina and at Berrys Landing in Georgia, have yielded a total of 111 marine diatom taxa. Varving of the diatomaceous clay suggests that the diatoms were deposited in a restricted basin or lagoonal area that had oxygen-deficient bottom waters. The Middle Miocene diatom assemblage of the Hawthorn is correlative with that of approximately the upper half of Miocene Lithologic Unit 16 of the Choptank Formation in the Chesapeake Bay region of Maryland and with the Serravallian Stage.

Georgia, South Carolina↗