Latest Quaternary sedimentation in the northern Gulf of Mexico Intraslope Basin Province: I. Sediment facies and depositional processes

Abstract

I met Bill Normark in the early 1970s when I was revising my first paper on Amazon Fan based on the excellent review he had just provided. He had already become one of the foremost authorities on modern fans. After that, I had the good fortune to interact with Bill numerous times during his career including at meetings, collaboration on publications, and describing Amazon Fan cores together during Ocean Drilling Program Leg 155. Early on I realized that Bill would always convey important ideas, suggestions, observations, or criticisms that had never occurred to me. I came to expect this whenever we interacted; I was never disappointed. Our field greatly misses his expertise and leadership. Charley Hollister was finalizing his landmark thesis on contourites at Lamont Geological Observatory (now Lamont-Doherty Earth Observatory) under Bruce C. Heezen, when I began my graduate studies under Bruce. As a senior graduate student, Charley provided invaluable guidance for operating in the Lamont environment both in the lab and at sea. Most importantly, he introduced me to the method of echo-character mapping with 12 kHz records, which he developed for his contourite studies. Charley and Bruce suggested that I use the same method, except with 3.5 kHz records, in my thesis research. This inspired me to develop a classification for 3.5 kHz echo character and to use echo-character mapping techniques in many different basins during my career; the most recent study is presented below. Charley was not only an exceptional scientist but also a great promoter and fundraiser within the marine geology community. His abilities and advice greatly helped me and others, who mainly relied on soft money. His untimely accidental death left a huge gap in the community.

Strike-Slip Transpressional Uplift Offshore San Onofre, California Inhibits Sediment Delivery to the Deep Sea

“…As such, paleoseismology studies that rely on turbidite emplacement records (e.g., Goldfinger et al, 2003Goldfinger et al, , 2007 should be approached with caution. The most conclusive results of this study confirm findings of regional scales from Covault et al (2007 and Normark et al (2009) and the effects of local ponded basins sensu Prather et al (1998) and Damuth and Olson (2015). The wide shelf offshore San Onofre likely prevents terrigenous supply to the deep sea during the post-glacial transgression and highstand, whereas the narrow shelf offshore Dana Point remains connected to sediment sources and has allowed for the recent emplacement of turbidites within the past 1000 years.…”

“…Such hemipelagic deposits are also observed draping inactive canyons that halted deposition ∼15-20 kyr ago (Sweet and Blum, 2016), such as the Mississippi (Normark et al, 1986), Amazon (Milliman et al, 1975;Normark et al, 1997), and Nile (Ducassou et al, 2009). While recent papers in the ICB have interpreted mud deposits interbedded with turbidites as hemipelagic background sedimentation (e.g., Maier et al, 2017), some studies in the Gulf of Mexico interpret gray-brown muds interbedded with turbidites as hemiturbidites, or thin fluid-mud flows moving continuously downslope (Damuth, 1977;Damuth and Olson, 2015). It is difficult for us to discern their exact origin, as laminations are obscured by bioturbation.…”

“…Morphologic factors such as bathymetry and shelf width may also exert important controls on sediment flux to canyons (Xu et al, 2010;Damuth and Olson, 2015). Distance from a river source and shelf width may change throughout sea-level cycles.…”

“…Nonetheless, recent studies have proposed that sea-level is subordinate to the distance between the canyon head and shoreline Blum et al, 2013;Gamberi et al, 2015) and proposed that distances < 5 km result in canyons characterized by active sand transport (Sweet and Blum, 2016). Secondary factors can exert controls on sediment flux to the deep sea, including ponded basins, which may serve as local depocenters that trap flow deposits (Prather et al, 1998;Damuth and Olson, 2015). Intraslope basins formed by diapirs or tectonic deformation may influence trends in bathymetry and subsequently the morphology of submarine canyons (Damuth, 1994;Damuth and Olson, 2015;Qin et al, 2019).…”

“…Secondary factors can exert controls on sediment flux to the deep sea, including ponded basins, which may serve as local depocenters that trap flow deposits (Prather et al, 1998;Damuth and Olson, 2015). Intraslope basins formed by diapirs or tectonic deformation may influence trends in bathymetry and subsequently the morphology of submarine canyons (Damuth, 1994;Damuth and Olson, 2015;Qin et al, 2019).…”