Stan Awramik-Keynote

Professor in the Department of Earth Science

University of California, Santa Barbara


Stan Awramik has been at the University of California, Santa Barbara, since 1974, where he teaches paleontology and historical geology. His research over the last 40+ years has primarily involved microbialites and microbial fossils preserved in chert. Much of his earlier work dealt with the Precambrian with an eye to understanding the Archean and Proterozoic Earth systems from a paleobiological point of view. In an attempt to better understand Precambrian microbialites, Awramik looked to lacustrine microbialites as more appropriate analogs. As a result, his research has covered microbialites of all ages (Archean to Recent) and from all environments (lakes, springs, and oceans).

The development and distribution of microbialites in giant lacustrine systems take center stage in his research. He is teamed up with Paul Buchheim (Loma Linda University) to study these lake systems. They include the Late Archean Meentheena Member (Tumbiana Formation) in Western Australia and the Eocene Green River Formation in Colorado, Utah, and Wyoming. These ancient giant lake systems were rich in carbonates and microbialites. Currently we are working on determining the factors that control initiation and development of lacustrine microbialites, and how they develop into biostromes and bioherms. We place the microbialites in their sedimentologic and depositional framework, determine their stratigraphic distribution, and analyze their facies relationships. 

A native of the Boston area, he grew up outside of Niagara Falls, New York and returned to the Boston area for his higher education. He received a BA in Geology from Boston University and PhD in Geology from Harvard. He did a one-year postdoc in Biology, also at Harvard. He then accepted a faculty position at the University of California, Santa Barbara, where he is currently a Professor in the Department of Earth Science. He is a Fellow of the American Association for the Advancement of Science and the Geological Society of America.

Title: A Brief, 3.5 Billion-Year History of Microbialites

9:15am - Wednesday, May 11th

Abstract: Microbialites are organosedimentary structures produced by the activity of microbes, primarily cyanobacteria. There are five types of microbialites: (1) stromatolites, characterized by lamination; (2) thrombolites, characterized by a clotted appearance; (3) dendrolites, characterized by a dendritic mesostructure; (4) leiolites, characterized by a structureless mesostructure; and (5) microbially induced sedimentary structures (MISS), characterized by microbially modified bedding.

Microbialites (stromatolites and MISS) constitute the oldest convincing evidence of life on Earth. Examples are found in rocks 3.49 Ga (billion years old). Microbialites have a continuous record throughout geologic time and are found forming in a variety of environments today. Microbialites can be grouped into four major episodes: (1) the Archean (3.5 to 2.5 Ga); (2) the Proterozoic (2.5 to 0.54 Ga); (3) the Phanerozoic (0.54 Ga up to the present day); and (4) the present day.

Most Archean microbialites are stromatolites and they are the most conspicuous evidence of life in the Archean. Generally, the stromatolites have simple shapes dominated by flat- laminated, domical and columnar structures. Some columnar forms are conical with an axial zone suggesting photosynthesis. Stromatolites formed in marine, lacustrine, and thermal spring settings.

In the Proterozoic all types of microbialites are found, except for dendrolites. Stromatolites predominate and exhibit a wide variety of shapes including elaborately branched columns. A number of the shapes are distinctive, have restricted time ranges in the Proterozoic, and are used for biostratigraphy. The Proterozoic was the golden age for stromatolites.  Most microbialites are found in marine settings.

The Phanerozoic has all five types of microbialites, but is still dominated by stromatolites. The stromatolites, however, are markedly less diverse morphologically and are often coarse-grained. The marine record dominates, but numerous lacustrine examples are known, particularly from the Cenozoic.

Today, all five types of microbialites occur. Stromatolites still seem to dominate with thrombolites quite common. Morphologically, shapes range from flat mats to domes and columns. There are numerous places where modern microbialites are forming, but there seems to be more lacustrine occurrences than marine. All modern occurrences are critical for our understanding of the biological, chemical, and physical processes operating and apply this knowledge to the interpretation of ancient microbialites.

Research and interest in microbialites is greater today than it ever has been. This is due to several factors, among them: (1) widespread new research on modern microbialites; (2) the search for the oldest evidence of life on Earth and developing criteria that provide convincing evidence of the biogenic nature of the fossil; and (3) the petroleum industry has discovered extensive hydrocarbon accumulations in microbialite reservoirs and need to understand factors that produced the microbialites.