COMPARISON OF HIGH-RESOLUTION EOCENE-OLIGOCENE TRANSITION PALEOCLIMATIC RECORDS FROM NORTH AMERICA AND NORTHERN EUROPE

For many paleoclimatic events, it is difficult to obtain similar resolution records from continental records as from marine records, making it difficult both to correlate between the different realms to understand the tempo and timing of events as well as to consider causal mechanisms. An exception to this is the Eocene-Oligocene transition (EOT) where thick, nearly continuous sections of continental rocks span the critical transition on multiple continents. In North America, high-resolution paleoprecipitation records derived from paleosols have been compiled for Oregon, Montana, and Nebraska, whereas in northern Europe, similar records have been compiled in Spain and the UK. In both regions, continental interior and coastal plain records can be compared to understand spatial patterns in paleoprecipitation distribution. Paleotemperature and paleomoisture composition records derived from both conventional and clumped isotopes exist for both Nebraska and the UK, making it possible to compare and contrast both differences between continents and between a continental interior and a coastal plain record. By making these broad scale regional comparisons, a number of general conclusions can be drawn: 1) significant aridification precedes the EOT in both continental interior and coastal plains sites, except in endoreheic basins (Montana, Spain) where this is little or no precipitation response, 2) amplification of cooling trends as compared with marine records is greatest in coastal plains sites and is minimized in continental interior sites, 3) more northerly sites generally show an enhanced temperature response, 4) inferred paleovegetation responses indicate only minor changes rather than a significant turnover, and 5) reconstructed changes in atmospheric CO2 appear broadly to be driving these patterns, but current reconstructions from either marine or continental settings lack the resolution to make detailed correlations in time.