MIDDLE EOCENE MARKLEY CANYON IN THE SACRAMENTO BASIN

The Markley Canyon is the youngest of the submarine canyons that originated on the shelf and slope in the Sacramento Basin in Paleogene times. These canyons were cut during lowstands of sea level and canyon formation can by correlated with the global sea level curves. The present study shows that the Markley Canyon was cut and filled in middle Eocene times. Previous studies have dated the fill as Oligocene to Miocene age. The canyon fill, however, can be correlated with the Sidney Flat Shale and the Kellogg Shale of middle Eocene age in the southern Sacramento Basin. Mapping of the Markley Canyon has shown that the incisement is located in the subsurface on the western margin of the basin and can be traced from Wheatland in the north, southward to the Byron area. The canyon is incised predominantly into sand rich turbidite units of the under lying Markley Formation. The Markley Canyon, as it is traced in the subsurface, has been extensively eroded below the regional late Tertiary unconformity. Erosion is most pronounced on its eastern and southern margins. The canyon fill can be seen in outcrops of Sidney Flat Shale on the southwestern margin of the basin. In outcrops in the Byron area, the canyon fill is comprised of the Kellogg Shale that rests directly on Nortonville Shale. Many gas fields are located on the margins of these Paleogene submarine canyons and the extension of the Markley Canyon into southern parts of the basin opens up new areas for hydrocarbon exploration.