Publication Type:
Book ChapterSource:
Geological Society of America, Northeastern Section, 35th annual meeting, Geological Society of America (GSA), Boulder, CO, United States, Volume 32, p.31 (2000)ISBN:
0016-7592Keywords:
Appalachians, Ashgillian, basins, bioclastic sedimentation, Canada, Caradocian, carbonate rocks, clastic sediments, eastern canada, erosion, foreland basins, Hirnantian, Iapetus, Laurentia, limestone, Llandovery, Lower Silurian, mud, North America, Ordovician, Paleozoic, quebec, Sedimentary rocks, sedimentation, sediments, sequence stratigraphy, Silurian, subsidence, tectonics, Telychian, Upper OrdovicianAbstract:
From Rawtheyan to mid-Telychian times, the Anticosti Platform, lay in a south equatorial-tropical regime along the eastern margin of Laurentia. This segment of the Appalachian foreland basin remained open to Iapetus ocean, and was bathed by the warm waters of a south tropical current system. The resultant carbonate ramp was battered by periodic tropical storms, which swept west from Iapetus. The area was largely protected from northward directed storms by rising tectonic highlands in the Gaspe Bay and Miramichi areas to the south. During landward directed barometric events, coastal setup of storm driven waters produced oblique cross-shelf currents which redistributed shallow water carbonate muds and bioclasts into deeper waters of the mid and outer shelf. On Anticosti Island, this led to deposition of over a kilometre of interbedded limestone and mudstone, with some mixed carbonate-siliciclastic sandstone, in water depths from 5 to 120 m. While major second order sea-level changes are recognised in both the sedimentary and paleontological record, higher order cycles, other than high frequency glacially driven cycles in the Hirnantian, are more difficult to correlate on a global scale due to marked tectonic influence on subsidence rates. Long term subsidence rates during the Caradocian were between 20 and 25 m/Ma, increasing to 75 m/Ma in the early Ashgill, reflecting loading by allochthonous terrains to the south during the Pusgillian and Cautlean. Load induced subsidence increased to a maxima of 276 m/Ma during the Rawtheyan, but declined significantly to 44 m/Ma in the Hirnantian, resuming an exponential decline from 19 to 8 m/Ma during the Llandovery. Load induced subsidence along this segment of the foreland basin appears to be out of step with loading events in the Appalachians to the south, although all or part of the Salinic disturbance may be represented by erosion of post Telychian strata from the Anticosti shelf.
Notes:
GeoRef, Copyright 2018, American Geological Institute.<br/>2003-017198<br/>Anticosti Platform<br/>Cautlean<br/>Pusgillian<br/>Rawtheyan
