GLOBAL HYPERWARMING AND SHALLOW MARINE DEPOSITION OF HYDROCARBON SOURCE ROCKS DURING OROGENY

Global hyperwarming, a recently proposed (by EL) climate control mechanism, features extreme deviations from the default greenhouse conditions of the Phanerozoic. Its onset apparently does not follow from higher atmospheric greenhouse gas concentration/increased plate tectonic rates. Hyperwarming involves a feedback with rising sea level and warming of tropical epeiric seas that leads to thermal expansion of the world ocean, accelerated eustatic rise, and very high eustatic and temperature levels. Increased ocean temperatures could lead to CO₂ outgassing and further warming, as well as increased salinity and lower dissolved oxygen. Hyperwarming is marked by expansion of the mid-water low oxygen water mass and dark organic-rich mud deposition on the shelves and lower down the continental slope of tropical and high latitude continents. First detailed from Lower Paleozoic passive margins, hyperwarming may have accompanied epeirogenic submergence of east Laurentia in the Taconian and Acadian orogenies. In both cases, organic-rich mud deposition was promoted by lowered oxygen solubility in hot fore-arc seas and increased turbidity and reduced photosynthesis in the water column with orogen erosion. In many cases, outcrops and well logs show that organic-rich black mud was laid down on subaerial unconformities that extend across vast areas of Laurentia. Evaporite crystals in some synorogenic black shales suggest elevated salinity. Thus, the traditional interpretation of these organic-rich mudstones as restricted “Black Sea”-type or deep fore-arc deposits is unsubstantiated. Identical organic-rich, synorogenic muds terminated Late Ordovician and Middle Devonian carbonate platform deposition. This emphasizes that the origin of forests, development of large igneous provinces, or ocean upwelling had nothing to do with the origin of these hydrocarbon source rocks. Briefly stated—petroleum source rock accumulation accompanies and ultimately terminates global hyperwarming by carbon burial.