The Markley Submarine Canyon in the Sacramento Basin, Northern California

Sullivan, Raymond and Sullivan, Morgan D.
[email protected]

The lower Tertiary section in the Sacramento basin includes several submarine canyons at different stratigraphic levels in the succession. The Markley submarine canyon is the youngest and has been dated as late Eocene/Oligocene age (Almgren, 1978, and Almgren et al 1988). As mapped, the Markley submarine canyon is limited to the central part of the basin. The system is oriented in a north-south direction along the axis of basin for some 45 miles in length and in places is up to 10 miles wide. Filling the deeply incised Markley submarine canyon is the Markley mudstone which is up to 2500 feet in thickness in subsurface. Dominating the canyon-fill are low-density, muddy turbidites. The canyon is deeply incises into submarine fan deposits of the Markley Sandstone of middle Eocene age and older formations. Several important gas fields are located along the trend of the Markley Canyon.

As part of the present study, a new, previously undescribed, submarine canyon has been documented in the southern part of the Sacramento basin which is older in age but has a similar stratigraphic relationship in the section as the Markley submarine canyon to the north. The southern canyon is filled with Sidney Flat Shale of middle Eocene age and is deeply incised into the underlying Markley Sandstone. The Sidney Flat Shale is made up of 1000 feet of distal muddy turbidites and diatomaceous mudstones in the outcrops on the north flanks of Mount Diablo. The submarine canyon fill reaches a maximum thickness of 1500 feet in the subsurface. It is oriented in a general north-south direction and can be traced for a distance of about 15 miles along the axis of the basin.

At least five mudstone-filled submarine canyons are now recognized in the lower Tertiary section in the Sacramento basin. These mudstone-filled submarine canyons are vertically stacked similarly to the Eocene fluvial/estuarine incised valley systems previous documented (Sullivan et al, 2012). The locations of these depositional systems are interpreted to have been controlled by tectonic subsidence due to their vertical stacking along the Sacramento basin axis. The timing of the submarine canyons and also the fluvial/estuarine incised valley systems appear to have been eustatically controlled based on the strong correlation between the ages of sediment filling relative to the worldwide coastal onlap curve. This suggests tectonics controlled the location of these deeply incised systems, both on the shelf and upper slope, but eustacy controlled the timing of incision, even in this clearly tectonically active basin. This has important implications for predicting where and when deeply incised canyons and valleys maybe have formed in similar depositional settings.

References

Almgren, A. A., 1984, Timing of Submarine Canyon and Marine Cycles of Deposition in the Southern Sacramento Valley, California: in Almgren A.A. and Hacker, P.D. eds., Paleogene submarine canyons of the Sacramento Valley, Califoirnia, Pacific section, AAPG, p. 1-16.

Almgren, A.A., Filewicz, M.V., and Heitman, H.L., 1988, Lower Tertiary Foraminiferal and calcareous Nannofossil zonation of California, in Filewicz, M.V., and Squires, R.I., eds., Paleogene Stratigraphy, West Coast of North America: Pacific Section, SEPM, p. 83-105.

Sullivan, R., and Sullivan, M.D., 2012, Sequence Stratigraphy and Incised Valley Architecture of the Domengine Formation, Black Diamond Mines Regional Preserve and the Southern Sacramento Basin, California, U.S.A., Journal of Sedimentary Research v. 82, p.781-800.

AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013