marine setting witli little or no subaerial exposure. Since the overlying B unit is believed to 

 be an upper Miocene or lower Pliocene deposit the erosional episode evidenced by the white 

 reflector is probably of Miocene age. 



The red reflector has been reached by cores and there is more direct information on the 

 red and the overlying blue reflection units than for deeper strata. The red reflector is 

 underlain sequentially southward by B, D, and E units. It is overlain by Pliocene, 

 Pleistocene, and Holocene sediments. The B reflection unit was deposited on the erosion 

 surface corresponding to the white reflector. Fbraminifera in B unit indicate that the 

 deposit was probably lain down in a water depth of 150 feet or greater. The internal 

 reflectors suggest that the deposit prograded eastward for at least 5 nautical miles along a 

 front of over 70 nautical miles forming an initial 5-nautical-mile-wide series of 

 seaward-dipping beds followed by near-horizontal beds. The occurrence of medium to 

 coarse quartz sand and a relatively deep water (> 150 feet) foraminiferal assemblage 

 suggests deposition near the foot of a prograding inshore terrace rising steeply from the shelf 

 floor. If this explanation is correct B unit must have originally been much thicker than the 

 present remnant. 



The surface of B unit may have been eroded before deposition of the type L sediment 

 of early Pliocene age, which overUes it in places; however, the evidence for an unconformity 

 is not clear. Seismic reflection records indicate that in places, the eroded top of B unit is 

 well below the level in which type L sediment was encountered in overlying cores. In the 

 few cores where both type L and type M sediment were recovered the contact between 

 them was a narrow zone containing elements of both sediment types. Changes in fauna and 

 mineralogy suggest that the contact zone could not have been created by unbroken 

 transition from one to another and more likely represents the result of mixing across a 

 boundary marking an erosional liiatus. 



If B unit was eroded before deposition of type L sediment the event must have 

 occurred in late Miocene or early Pliocene time. Where B unit is not overlain by Pliocene 

 sediments its surface was probably re-eroded during a period of lower eustatic sea level in 

 Pleistocene time. The red surface is thus a product of more than one erosional episode. 



Age of the sediments contained in A reflection unit ranges from probable early Pliocene 

 to Holocene. Type L sediment lithology is the earliest known deposit of the reflection unit 

 and probably originated during a higher relative sea level stand in Pliocene time. 

 Subsequently this deposit was eroded and sediments of Pleistocene and Holocene age were 

 deposited on the eroded surface. 



Locally between Holocene-age sediments (Types A and F) and Miocene-PUocene deposits 

 (Types L and M) there exists a complex group of sediments having widely varying lithologic 

 and faunal characteristics. These deposits are judged to be of Pleistocene age, but possibly 

 they include older material. Many of these sediments can be included with the broadly 

 defined type G sediment which probably comprises several facies and possibly more than 

 one stratigraphic unit. 



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