Climatic implications of terrestrial arthropods from the Parachute Creek Member (Middle Eocene), Green River Formation, Garfield County, Colorado

• Main Author: Codington, Larry A.
• Format: Text
• Language: English
• Published: Fort Hays State University 1993
• Subjects: Geology; Arctic
• Online Access: http://contentcat.fhsu.edu/cdm/ref/collection/thesis/id/666

In an attempt to determine if fossil insects could be used for paleoclimatic determinations, a portion of the Parachute Creek Member of the Green River Formation in Western Colorado was trenched and all fossils were collected. The study area is located in Sec’s. 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, T55, R101W and 31, 32, 33, T4S, R101W. The Parachute Creek Member is a finely varved shale measuring 69 m thick in the study area. The Parachute Creek Member overlies and interfingers with the Douglas Creek Member of the Green River Formation. Seven orders of insects were collected all representing extant orders. These insects represent 44 genera of which 14 are extant. All species are extinct. The extant genera of Diptera and Coleoptera were used to determine the paleoclimatic conditions at the time of deposition by using the ranges of extant species as representative of the extinct species ranges. This data was then compared to results obtained from paleobotancial research. Modern representatives of these genera range from the Arctic to Central America and overlap primarily in the Texas-Mexico region. These ranges suggest that the paleoclimatic conditions at the time of Parachute Creek Member deposition, were a regime like that found around an intermontane, lake existing at the latitude of Texas-northern Mexico. This paleoclimatic interpretation is in agreement with that derived from paleobotanical data. This agreement indicates that Tertiary insect faunas may be useful in the determination of paleoclimatic regimes.