PALEOCLIMATIC AND PALEOECOLOGICAL IMPLICATIONS OF A PALEOCENE–EOCENE FOSSIL LEAF ASSEMBLAGE, CHICKALOON FORMATION, ALASKA

• Published in: Palaios Vol. 26; no. 6; pp. 335 - 345
• Main Authors: SUNDERLIN, DAVID, LOOPE, GARRISON, PARKER, NANCY E, WILLIAMS, CHRISTOPHER J
• Format: Journal Article
• Language: English
• Published: SEPM Society for Sedimentary Geology, 4111 S Darlington, Suite 100, Tulsa, OK 74135-6373, U.S.A SEPM Society for Sedimentary Geology 01-06-2011; Society for Sedimentary Geology; SEPM (Society for Sedimentary Geology)
• Subjects: Alaska; Angiospermae; assemblages; Cenozoic; Chickaloon Formation; Climate change; Climate Leaf Analysis Multivariate Program; Climate models; Coal; Dicotyledoneae; Evan Jones Mine; Flora; Fossils; Gastropoda; Geology; Herbivores; Infestation; Leaves; lithostratigraphy; Matanuska Valley; Metasequoia; morphology; numerical models; Paleocene-Eocene Thermal Maximum; Paleoclimatology; paleoecology; Paleogene; Plantae; preservation; Spermatophyta; Stratigraphy; Sutton Alaska; Tertiary; United States; Canada; PN, Arctic; USA, Alaska
• ISSN: 0883-1351; 1938-5323
• DOI: 10.2110/palo.2010.p10-077r

New collections of a leaf compression-impression paleoflora preserved in fluvio-lacustrine sediments of the upper Chickaloon Formation, south-central Alaska, United States, provide leaf physiognomic climate estimates for the early Eocene in southern Alaska and rare data on plant-insect interactions from a subarctic setting. Thirty-nine broadleaf angiosperm morphotypes occur in a parautochthonous assemblage along with Metasequoia shoots and trunks, compressions of a diverse suite of seeds, monocotyledonous aquatic plants, freshwater gastropods, and inclusion-bearing dispersed amber. Leaf-character derived mean annual temperature estimates (11–14.6 °C) are significantly warmer than Alaska at present and indicate warm temperate conditions at the time of deposition. Leaf-derived mean annual precipitation estimates of ∼110–160 cm/annum are comparable to those from similar-age paleofloras in Arctic Canada and indicate wetter conditions than nearly coeval paleofloras further south in the North American mid-latitudes. Leaf herbivory is rare in the Chickaloon assemblage (∼9% of leaf fragments) as compared to other, lower latitude Eocene assemblages, but exhibits four of the main leaf-damage guilds (hole feeding, margin feeding, surface feeding, and skeletonization). These data provide a rare glimpse at a high-latitude terrestrial forested ecosystem during a global hothouse climate phase and thus have implications in understanding how biogeographic patterning and ecological systems respond to non-analog, warm high-latitude environmental conditions.