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Early Part of Last Deglaciation: A Short Interval Favorable for the Building of Coralgal Edifices on the Edges of Modern Siliciclastic Shelves (Gulf of Papua and Gulf of Mexico)

Andre Droxler1, Gianni Mallarino2, Jason M. Francis1, Jerry Dickens1, Luc Beaufort3, Samuel Bentley4, Larry Peterson5, and Bradley Opdyke6
1 Rice University, Houston, TX
2 PanTerra Geoconsultants B.V, Leiderdorp, Netherlands
3 CEREGE - Université Aix-Marseille III, France
4 Louisiana State University, Baton Rouge, LA
5 University of Miami, Miami, FL
6 Australian National University, Canberra, Australia

Two surveys, using multi beam bathymetry, 3.5 kHz seismic profiling, piston coring, and dredging, were conducted by the R/V Melville in 2004 and by the R/V Marion Dufresne in 2005 along the shelf edge of the Gulf of Papua. In the northern part of Ashmore Trough, the survey uncovered a 30 to 40 m-thick ridge that parallels the shelf edge with linear segments exceeding 10 km in length. The analyses of a core, recovered within one of the ridge cuts, demonstrate that the coastline reached the present-day shelf break during Last Glacial Maximum. During a first pulse of sea level rise, occurring between 16,000 and 13,000 calendar years, it is postulated that, during this early transgression, a coralgal reef established itself on top of a LGM siliciclastic beach barrier complex. On the northeast shelf edge of the Pandora Trough, a coralgal edifice, as thick as 80 m and sampled at its basis by a piston core, was established on top of a LGM shelf edge delta located at about 120-125 m below modern sea level. Similarly a series of 40 to 50 m-thick coralgal banks were established during the first part of the last deglaciation on top of lowstand coastal deposits along the South Texas shelf edge between the Rio Grande and Brazos/Colorado lowstand deltas offshore Corpus Christi. Those three examples illustrate that the early part of the last deglaciation was a unique interval for the establishment and growth of coralgal edifices on top of LGM siliciclastic coastal deposits.