A Review of Paleotemperature Lapse Rate Methods for Estimating Paleoelevation from Fossil Floras

Abstract

One widely-applied method for estimating paleoelevation from fossil floras uses the relation between vegetation and temperature to estimate mean annual temperature from two isochronous fossil assemblages (one at elevation and one at or near sea level), and the difference between these temperatures is multiplied by the reciprocal of a temperature lapse rate to estimate paleoelevation. Three fundamentally different approaches have been developed, and these vary both in the method by which paleotemperatures are estimated and in the way by which modern lapse rates can be measured. Paleotemperature methodologies include the use of plant physiognomy, or the use of nearest living relatives. Lapse rate methodologies use either a global terrestrial lapse rate as the world mean, a regional terrestrial lapse rate that represents a large portion of a continent, or a local terrestrial lapse rate for areas narrowly confined by latitude and longitude. Other variables and/or corrective factors that should be considered in these applications include the thermal effects of continentality and elevated land surfaces in the continental interior, and standardization to compensate for fluctuations or variability in sea level, global climate change, and paleolatitude. These different methodologies can be contrasted by their common application to the late Eocene Florissant flora of Colorado, with results ranging from 455 to 4133 meters.