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Paleobiogeography What is it? • Studying geographic distributions of fossil organisms • So what? – Biostratigraphy – correlating between biotic provinces – Paleogeography – tracking sea level changes, reconstructing plates and continents – Paleoclimatology – using organisms to track climate Water Masses • “Bodies of ocean water with relatively uniform conditions of temperature and salinity • E.g.: California Current, Central Pacific Water http://oceanmotion.org/html/background/timeline1978-88.htm Implications: • Geographic distributions of organisms can reflect boundaries of water masses • Equatorial currents act as dispersal barriers to marine organisms (cold water critters can’t cross equator) • Ocean currents depend on: – Continental positions – Heat budget of Earth – And so does the geographic distribution of organisms • So mapping the organisms can map ancient ocean water masses and currents Tectonic processes affect the distribution of organisms • Creation/elimination of dispersal barriers – E.g. Opening of Atlantic is barrier to land organisms, pathway for marine organisms • Changes in ocean currents • Changes in basin depth & therefore sea level • Changes in climate – continentality promotes extreme terrestrial climates Implications • Plate distributions can explain organism distributions – E.g., Tethys organisms • Organisms can be evidence for plate reconstructions Examples • Gondwana reconstructions – Mesosaurus – freshwater lizard – Glosspteris – tropical flora – “Viking funeral ships” – dead when the continents separated http://www.mrsciguy.com/sciimages/fossil_record.gif Examples • Gondwana reconstructions – Mesosaurus – freshwater lizard – Glosspteris – tropical flora – “Viking funeral ships” – dead when the continents separated • Baja rifting – Legless worm lizard – “Noah’s ark” – range separated while species was extant Examples • Exotic terranes: – Late Paleozoic to Meoszoic California (and the ret of the Cordillera) is made of many accreted terranes – • As small as island arcs from subduction zones • As large as continental fragments • Evidence – Lithologic – Paleomagnetic – magnetic declination & inclination – Fossils – tropical fusilinids in Permian rocks http://plate- Organisms & Climate • Distribution of organisms is affected by climate & climate change • If you know the biology, you can infer the climate: pollen • If you know the climate (using other evidence – isotopes, pollen), you can infer biology: high latitude dinosaurs & homeothermy • Maybe we can use past climate & biogeographic shifts to predict the current change – What happened in interglacials? Where to the climate & vegetation belts go?
