Cenozoic Diatom Research Articles

Zoya Il'inichna Glezer – life and scientific achievements

Zoya Ilyinichna Glezer is the largest Russian micropaleontologist, a specialist in siliceous microfossils — Cenozoic diatoms and silicoflagellates. Since the 1960s, she systematically studied Paleogene siliceous microfossils from various regions of the country and therefore was an indispensable participant in the development of unified stratigraphic schemes for Paleogene siliceous plankton of various regions of the USSR. She made a great contribution to the creation of the newest Paleogene schemes in the south of European Russia and Western Siberia, to the correlations of the Paleogene deposits of the Kara Sea.

Testing the accuracy of genus-level data to predict species diversity in Cenozoic marine diatoms

Abstract Correlations between past biotic diversity and climate can inform humanity’s response to predictions of future global climate change, e.g., extinction risk with global warming. Paleodiversity studies, however, frequently use genera as a proxy for species diversity, a practice that has often been questioned. Tests using actual data of the impact of using species-level versus genus-level taxonomy in paleodiversity-paleoenvironmental studies are also lacking. We conduct such a test, based on a recent study that showed a strong correlation of Cenozoic marine planktonic diatom species diversity to geochemical climate proxies. Using an updated version of the data set, we still find a strong correlation of Cenozoic diatom species diversity to environment. Using identical data but instead genera results in the loss of all significant correlations of diversity to environmental change. This occurs due to the earlier rise and later stability in genus versus species diversity data, a pattern known to be common between taxonomic ranks in the fossil record, and in general models of diversification. We conclude that studies of paleodiversity, particularly those addressing biotic responses to future environmental change, need to demonstrate the adequacy of genera as a proxy for species diversity, or use species-level data.

The Cenozoic diatom zonation and its significance for stratigraphic correlations in the North Pacific

The current state of the North Pacific Cenozoic diatom zonation is reviewed. The high resolution of diatom zonation is shown, which is comparable to that of groups of calcareous planktonic microfossils. The significance of diatom assemblages for the dating and correlation of various Tertiary marine sediments in the North Pacific is discussed. Recent examples of subdivision of the Oligocene-Neogene sequences of this region and dating of geological events on the zonal basis are given.

Neogene diatoms from the Sandy Ridge section, Alaska Peninsula: Significance for stratigraphic and paleogeographic reconstructions

Fossil diatoms from the Milky River Formation of the Sandy Ridge section, Alaska Peninsula are analyzed. Data on stratigraphic distribution of diatoms and silicoflagellates are presented. Based on presence of stratigraphically important forms (Neodenticula kamtschatica, Thalassiosira oestrupii, Cosmiodiscus insignis), the assemblages studied are correlated with the North Pacific Cenozoic diatom zones. An assemblage similar to that of subzone “b” of the Neodenticula kamtschatica Zone (Barron and Gladenkov, 1995) indicates the latest Miocene-initial early Pliocene (5.5-4.8 Ma) age of its host deposits. Additional species of biostratigraphic importance (Thalassiosira temperei, Th. latimarginata, and others) refine ages of different parts of the section. In particular, age of stratigraphically lowest beds bearing Astarte (mollusks valuable for establishing the Bering Strait opening) were dated at 5.5-5.4 Ma. Some paleogeographic inferences are made from analysis of composition of the diatom assemblages.

The late Cenozoic diatom stratigraphy and paleolimnology of Tule Lake, Siskiyou Co. California

Lacustrine diatoms are diverse, well preserved and abundant in cores of lake sediment to 334 m depth near the town of Tulelake, Siskiyou County, northern California. The cores have been dated by radiometric, tephrochronologic and paleomagnetic techniques, which indicate a basal age of about 3 million years (Ma) and a nearly continuous depositional record for the Tule Lake basin for the last 3 million years (My). Fossil diatoms document the late Cenozoic paleolimnologic and paleoclimatic history for the northwestern edge of the Basin and Range Province. During the last 3 My, Tule Lake was typically a relatively deep, extensive lake. The Pliocene is characterized by a diatom flora dominated by Aulacoseira solida suggesting more abundant summer precipitation and warmer winters. Increases in ‘Fragilaria’ at 2.4 Ma and between 2.0 and 1.7 Ma imply cooler summers that correlate to glacial environments recorded elsewhere in the world.