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Chevron U.S.A. <br /> Page a <br /> _ metamorphic and marine sedimentary rocks of pre-Tertiary age. Folded and f-ulted <br /> sedimentary rocks of Mesozoic and Cenozoic age of the Coast Flanges predominate tho <br /> western boundary of the San Joaquin Valley. The San Joaquin Valley trough segment G#' <br /> the rentrai Valley trough has baen filled with as much as six vertical miles of <br /> sediments,ranging in age from Jurassic to Holocene. <br /> The area beturc:n Sacramento Valley proper on the north and San Joaquin Malley <br /> proper to the south is commonly referred to as the Delta,a marsh area generally <br /> outlinod by the City of Sacramento on the north,The City of Stockton on the south and <br /> Suisun Bay on the west. <br /> The topography of the Delta is flat,with levees and dredged material disposal <br /> areas frequently constituting the highest ground. land surfaces range in elevation <br /> ' from about 20 feet above mean sea level to about 25!aet below mean sea level. <br /> The Delta Is a structural and topographic basis underlain by an estimated 37,000 <br /> feet of sediments which accumulated during the Mesozoic and Cenozoic periods. <br /> Regional subsidence acid deposition in a marine environment ended in fate Eocene time. <br /> During middle and late Eocene time,the margins of the basin experienced mild uplift, <br /> folding,and faulting. From laic Eocene to Pleistocene,the basin received <br /> continental fluviatile deposits. Volcanic debris was also carried into the valley <br /> from the Sierra and Coast Mange. Tectonic subsidence in the California Delta and the <br /> Sacramento Basin ended in Cuaternary time. At the end of the Pleistocene period, <br /> about 10,700 years ago,the sea level began to rise and peat and detrital sPaiments <br /> accumulated. <br /> - l6�OU-205-D44 <br /> ism EMWZ9NMHWM--- <br /> 1).�s�t•+ � ttir.,Et�. <br /> i <br /> j <br /> i <br /> i <br /> i <br />