- Friday, September 11, 2015
- 1:30 PM–2:30 PM
- Science Building 010
Ralph Stearley Ph.D. Professor of Geology Calvin College
The earliest known instance of a salmonid fish is Eosalmo, from the Eocene of NW North America, but the fossil record of salmonids is poor until circa 20 million years before the present. During the Neogene (23 Ma to present) the global climate cooled, Arctic and Antarctic ice appeared, and our existing marine surface circulation systems were emplaced. Representatives of several lineages of salmonids appear in western North America during this period, contemporaneous with climatic cooling. Their diversity at this time leads to the conclusion that much evolution within the group had occurred prior to 20 Ma, but in boreal environments for which we have little record. Tectonic developments in the western North America Cordillera during the Neogene resulted in the production of numerous small and large lacustrine basins and shifting drainage connections, promoting speciation as well as providing settings under which fossils could be preserved. A dense Neogene record of diverse chars, trouts (rainbow and cutthroat lineages), and salmons, including planktivorous and piscivorous forms, has been extracted from coastal marine sediments and from lacustrine sediments over the past 150 years. The fossil salmons include the giant extinct spike-tooth salmon, O. rastrosus. These fossils demonstrate that familiar salmonid metapopulation dynamics and life-history strategies were present early in the history of this group and are extremely successful in the climatic, oceanographic and tectonic context of the Northern Pacific rim over the past 20 million years or more.
This seminar is co-sponsored by the Mellema Program and the Geology, Geography & Environmental Studies Department of Calvin College.