Highstand fans in the California borderland: The overlooked deep-water depositional systems

Abstract

Contrary to widely used sequence-stratigraphic models, lowstand fans are only part of the turbidite depositional record; our analysis reveals that a comparable volume of coarsegrained sediment has been deposited in California borderland deep-water basins regardless of sea level. Sedimentation rates and periods of active sediment transport have been determined for deep-water canyon-channel systems contributing to the southeastern Gulf of Santa Catalina and San Diego Trough since 40 ka using an extensive grid of high-resolution and deep-penetration seismic-refl ection data. A regional seismic-refl ection horizon (40 ka) has been correlated across the study area using radiocarbon age dates from the Mohole borehole and U.S. Geological Survey piston cores. This study focused on the submarine fans fed by the Oceanside, Carlsbad, and La Jolla Canyons, all of which head within the length of the Oceanside littoral cell. The Oceanside Canyon-channel system was active from 45 to 13 ka, and the Carlsbad system was active from 50 (or earlier) to 10 ka. The La Jolla system was active over two periods, from 50 (or earlier) to 40 ka, and from 13 ka to the present. One or more of these canyon-channel systems have been active regardless of sea level. During sea-level fl uctuation, shelf width between the canyon head and the littoral zone is the primary control on canyonchannel system activity. Highstand fan deposition occurs when a majority of the sediment within the Oceanside littoral cell is intercepted by one of the canyon heads, currently La Jolla Canyon. Since 40 ka, the sedimentation rate on the La Jolla highstand fan has been >2 times the combined rates on the Oceanside and Carlsbad lowstand fans.

Connections Between Fluvial To Shallow Marine Environments and Submarine Canyons: Implications For Sediment Transfer To Deep Water

“…Republished with permission from the Geological Society of America, , their figures 3 and 4. (Ducassou et al 2009), the Danube (Popescu et al 2001), the Astoria (Carlson and Nelson 1969;Nelson et al 2009), the Var , the La Jolla (Covault et al 2007), and the Golo (Gervais et al 2006). In some cases there is one long-lived canyon (e.g., the Zaire), whereas in other cases multiple canyons may feed the fan at different times as fluvial avulsion and delta-lobe switching changes the location of pointsource sediment input (e.g., the Gulf of Lion, Berné and Gorini 2005).…”

“…In contrast to the sequence stratigraphic models of the 1980s, Covault et al (2007), , and used highresolution seismic, bathymetric, and geochronologic data from Quaternary systems to understand how the interaction between sea level, climate, shelf width, and the location of littoral cells controlled the volume of sediment delivered to deep water. The approach of these studies was different from earlier work because the focus was on the detailed observations during a small slice of the stratigraphic record in the Quaternary, a time of highfrequency, glacially driven sea-level change, and they did not explore the impact of tectonic subsidence.…”

Rapid Adjustment of Submarine Channel Architecture To Changes In Sediment Supply

“…Sediment supply, as in subaerial systems, must play a key role as well in the architectural evolution of submarine depositional systems. Many studies have documented sediment-supply-induced changes in submarine channel and fan activity (Covault et al, 2007;Romans et al, 2009;Paull et al, 2010Paull et al, , 2011. However, few studies have been able to constrain changes in the architecture of deep-water depositional systems caused by variations in sediment supply (Piper et al, 1999).…”

Role of sea-level change in deep water deposition along a carbonate shelf margin, Early and Middle Permian, Delaware Basin: implications for reservoir characterization

“…However, the turbidite sedimentation on the Mississippi Fan (Kolla & Perlmutter 1993), deep water fans in the Lance-Fox Hills-Lewis shelf margin (Carvajal & Steel 2006), and fans in the California borderland (Covault et al 2007) show that large amounts of sand can be transported to deep water even during sea level rise and highstand. Pointsourced sandy fans may be well developed as a result of high sediment supply on the shelf during highstand, as opposed to sand/mud-rich deep sea fans which developed during falling or low sea level (Steel et al 2008).…”