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Albert, N.R., 1988

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Bibliographic Reference

Albert, N.R., 1988, Dinoflagellate cysts from the early Cretaceous of the Yukon-Koyukuk basin and from the Upper Jurassic Naknek Formation, Alaska: Palo Alto, California, Stanford University, Ph.D. dissertation, 481 p., illust., maps, 52 plates.

Abstract

Dinoflagellate cyst assemblages have been recovered from the Hughes Creek section, a reconnaissance-type measured section in unnamed Early Cretaceous rocks in the northeast part of the Yukon-Koyukuk basin, interior Alaska and from the Wandering Ridge, Mount Pedmar, and Chisik Island measured sections in the Late Jurassic Naknek Formation, southern Alaska. Of the 139 dinoflagellate taxa recorded from these sections, 107 are from the Hughes Creek section and 32 are from the three sections in the Naknek Formation. The taxa from the Hughes Creek section include: two new genera, Epikrokon and Hatdolitnia; and six new species, Aldorfia laticincta, Epikrokon fenestratum, Hatdolitnia phalanx, Meiourogonyaulax paradigmatos, Oligosphaeridium flaccidum, and Pentadinium antiquarium. The taxa from the three sections in the Naknek Formation include: one new genus, Lacrymodinium; and five new species, Batiacasphaera puticulata, Impagidinium grycii, Lacrymodinium warrenii, Leptodinium vagicristatum, and Rhynchodiniopsis kimmeridgiana. Prior to this study, megafossils established a Hauterivian to early or middle Albian age for the part of the Hughes Creek section from which samples yielding dinoflagellates were collected. Age ranges for the extracted dinoflagellate assemblages, characterized by high diversity and moderate to high abundances, however, indicate that this part of the section can be divided into three zones, ranging from middle late Hauterivian to latest early Aptian. The late middle Oxfordian through early Kimmeridgian ages given for the three measured sections of the Naknek Formation on the basis of the pelecypod, Buchia, correlate with the age ranges for the dinoflagellate taxa identified in this study. The dinoflagellate assemblages from these measured sections are characterized by very low diversity and high abundances of one to several species. Numerous samples contain extremely high abundances of one or two species and may reflect ancient plankton blooms. One new genus, Lacrymodinium, is characterized by a srngle, middorsal intercalary archeopyle and a gonyaulacoid paratabulation, with an exsert epicyst pattern most similar to the epithecal tabulation pattern of modern Triadinium, and a partiform hypocyst pattern most similar to that of fossil Carpathodinium and Microdinium.

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