Michael R. Rosen

U.S. Geological Survey

Water Science Field Team, Nevada


Michael joined the USGS in 2001 and is based in Carson City, Nevada.  He is currently the Water Science Field Team, Water Quality Specialist for the western United States.  From 2001 to 2011 he was a Research Hydrologist at the USGS working on groundwater and surface water quality as well as the role of groundwater in the formation of microbialites in Great Basin lakes.  He is an adjunct professor in the Department of Geological and Engineering Sciences and a faculty member of the Hydrological Sciences Program at the University of Nevada – Reno.  Michael was named as a Fellow of the Geological Society of America in 2010.  He was previously employed at the Inst. Geological & Nuclear Sciences, New Zealand, the Division of Water Resources, CSIRO, and Curtin University of Technology in Western Australia, and the Limnological Research Center at the University of Minnesota.  He received his BS at Haverford College (majoring in Geology at Bryn Mawr College), his MS from the University of Rochester and his PhD from the University of Texas - Austin.    He has been working on microbialites and saline lakes since 1985 and is actively conducting research on microbialites in Nevada and California saline lakes as well as microbialites from Western Australia.

Title: The Role of Groundwater in the Formation of Great Basin Microbialites and Tufa

2:10pm - Wednesday, May 11th

Abstract: The role that groundwater plays in microbialite and tufa formation in the Great Basin of the United States has largely been deduced from direct visual field observation (modern tufas) or by inference (Pleistocene tufas).  More than 38 localities worldwide have been interpreted as having groundwater sources for microbialite formation.  All extensive occurrences of microbialites in the Great Basin, with the exception of Great Salt Lake bioherms, have been interpreted to rely on groundwater to form the microbial mounds.  However, few direct measurements of chemical changes in the water passing through the mounds   or measurements of water table fluctuations or heads over seasons or years within the mounds have been made.  However, little is known regarding groundwater flow rates and pore-water chemistry within the mounds in comparison to locations where the mounds are not forming.  These more detailed observations are critical to evaluating how hydrological inputs may be contributing nutrients and/or supporting chemical microenvironments conducive to microbial growth or if simple inorganic saturation caused by mixing between mostly saline lake water and fresh groundwater is important.  This abstract presents case studies from Big Soda Lake, Nevada and Mono Lake, California with examples from other lakes in the Great Basin and elsewhere to demonstrate direct evidence of the role that groundwater plays in microbialite formation.  Continued monitoring of groundwater heads and chemistry, both seasonally and annually, will be critical to understanding how climate-driven hydrological changes impact microbialite development in the Great Basin.