USGS-GD-Scientific Capabilities - MICROFOSSILS DIATOMS Equipment





Because of their rapid evolution during the Cenozoic, particularly during time of climate change, diatoms are extremely useful in providing a chronology for marine stratigraphic sections. Major advances have been made as a result of the Ocean Drilling Program (ODP) and its predecessor, the Deep Sea Drilling Project (DSDP). Diatom biostratigraphy is particularly useful in high-latitude environments, where due to the dissolution of calcareous microfossils, diatoms may be the only biostratigraphic marker preserved in the sediments. Many of chronologies developed at deep ocean sites (DSDP and ODP) can be utilized in onshore sequences such at the Monterey Group in California.

Coastal and estuarine studies
Diatoms have been used to evaluate the impact of man on the nearshore environment. Recent studies in Chesapeake Bay have documented changes in the ecosystem as a result of clearing land for agricultural purposes and the overuse of inorganic fertilizers. In San Francisco Bay, diatoms have been used to identify natural variations in precipitation over the past 3,000 years, as well as for studying the impact of reducing freshwater flow into the bay as a result of increased damming of rivers for agricultural and municipal uses.

The sensitivity of diatoms to changes in temperature, salinity, and nutrients makes them ideal indicators of past ocean history. They can be used to analyze the effect of large-scale changes in global temperature such as took place in the mid-Pliocene and during interglacial intervals in the Pleistocene; the tectonically driven opening and closing of major marine pathways such as the Isthmus of Panama; or short-term events such as El Niņo.

Due to the relative small size (even the Great Lakes) of the basins, lake systems are subject to substantial variations in temperature, conductivity, and nutrient load. Diatoms are excellent proxies for all these parameters. In the upper Midwest, the shifting of air masses resulting from the melting of continental glaciers and middle Holocene aridity have been documented. The impact of the pioneers transforming the forests of the upper Midwest to agricultural land can be seen through changes (which reflect nutrient load) in the diatom flora of small lakes. In eastern California, the rise and fall of pluvial lakes over 800,000 years has been tracked.

Earthquake studies
Along the Oregon and Washington coasts, magnitude 9 or greater seismic events have left their marks in the diatom record. An instantaneous influx of shallow marine diatoms into a shallow freshwater pond may suggest the rapid subsidence of the area as a result of an earthquake.

Environmental quality
The sensitivity of diatoms to environmental change makes them useful indicators of such man-made problems as acid rain. The pH tolerance of particular taxa can be used to document both the damage to the ecosystem and its subsequent recovery.

One of the most interesting applications of diatoms occurred during World War II. Diatoms were used to determine the launch point for the balloons used by the Japanese to bomb the Pacific Northwest. Sediments from ballast were used to pinpoint the beach from which the balloons were launched. Diatom assemblages are also unique enough that they can be used to trace the movement of stolen property (based on the diatoms that accumulate on the surface over time), including vertebrate fossils (based on the composition of the matrix in which the fossils were found).


Western Lakes Project
Work in Owens Lake is unraveling the rate and timing of glacial-interglacial cycles in the Western U.S.

Diatoms used in conjunction with other microfossils to document increased global warming during the mid-Pliocene.

Warm Climate Intervals
High-resolution studies of diatom floras are being used to document rapid (decadal to century) fluctuations in climate along the California coast.

Cascadia Margin
Diatom studies in coastal ponds and marshes have helped to refine our knowledge of the interval between large seismic events along this subduction zone.

National Cooperative Geologic Mapping Program
Diatoms provide stratigraphic control for several mapping along the West Coast, particularly in rocks of Cretaceous, Eocene, Miocene, and Pliocene age.

USGS Energy Program
Diatoms can be used for both stratigraphic control and assessing the productivity of the environment in which sediment were deposited.


The Diatom Collection of the California Academy of Sciences

Diatom Home Page

Diatom Paleolimnology Data Cooperative NOAA Paleoclimatology Program

Great Lakes Diatoms

Introduction to the Bacillariophyta

Patrick Center for Environmental Research at The Academy of Natural Sciences

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