Publikationen

Matthew G. Powell

Research Synopsis

Marine organisms suffered a mass extinction at the beginning of the late Paleozoic ice age, 327 million years ago, and then did not recover for nearly 40 million years. During my stay with INCREMENTS (funded through the Humboldt Foundation) I studied the unique climate of this interval in order to uncover the reasons for this new state of the global marine ecosystem. My approach combines sclerochronology with trace element geochemistry of brachiopods (an abundant Paleozoic marine invertebrate) in order to resolve a seasonal record of paleotemperatures before and during the late Paleozoic ice age. My results using a Mg/Ca thermometer demonstrate a drop in average tropical ocean temperature from about 17-18°C in early Visean time to about 8-11°C by Moscovian time, a drop of ~8°C. Most of the decrease was due to declining maximum (presumably summer) temperature, resulting in reduced seasonality during the late Paleozoic ice age.

Publications

In review and submitted:

(1) Powell MG. Geographic range and genus longevity of Late Paleozoic brachiopods.

(2) Powell MG. Timing and selectivity of the late Mississippian mass extinction of brachiopod genera from the Central Appalachian basin.

Peer-reviewed:

(6) Powell MG, Schöne BR and Jacob DE 2009. Tropical marine climate during the late Palaeozoic ice age using trace element analyses of brachiopods. Palaeogeography, Palaeoclimatology, Palaeoecology 280, 143-149.

(5) Powell MG, 2007. Latitudinal diversity gradients for brachiopod genera during late Paleozoic time: Links between climate, biogeography, and evolutionary rates. Global Ecology & Biogeography, in press.

(4) Powell, MG, 2005. Climatic basis for sluggish macroevolution during the late Paleozoic ice age. Geology 33, 381-384.

(3) Stanley SM & Powell MG, 2003. Depressed rates of origination and extinction during the late Paleozoic ice age: A new state for the global marine ecosystem. Geology 31, 877-880.

(2) Powell MG & Kowalewski M, 2002. Increase in evenness and sampled alpha diversity through the Phanerozoic: Comparison of early Paleozoic and Cenozoic marine fossil assemblages. Geology 30, 331-334.

(1) Bush AM, Powell MG, Bert TM, Arnold WS & Daley GM, 2002. Time-averaging, evolution, and morphologic variation. Paleobiology 28, 9-25.