| OCR Text |
Show 155 A broad bench, developed merate, generally marks the the resistant on top of the resistant Salt Wash softer mudstones and shales of the Statigraphic relationships Salt Wash both are "Christmas-tree" conglo Basin formation. The lower and upper contacts of the - gradational. overlying Brushy and the In general the transition from the marine Jurassic to the continental Salt Wash shows little evidence of interruption in sedimentation. Neither paleontologic evidence indicates nor transition fro marine to composition over large the sharp change in lithology any considerable time gp in the non-marine; areas a there is boundary sandstone. ris a little must be set The lower contact in Colorado has been writer at the top of so change in arbitrarily. arbitrarily set 3 to 5 foot horizontally bedded widespread sandstone has been traced over mot of western Colo rado and the writer is convinced that the bed is continuous. this sandstone bed is limestone, a unit of thin-bedded and occasional cut and fill The limestones contain remains of pelecypods and gastropods. unit is indicative of few widely separated positing the large streams scour algae, crossing marker sandate ne dominantly limestone unit is unit and it.is difficult to fresh water sandstone channels. fresh water fresh water lakes and type are the flat ostracods, with floodplain red, reddish area brown and a and de Below grayish In southwestern Colorado replaced by separate playas in the scoured channels. red siltstones which weather "brick-red". the sandstone, Above The environment of the lower Morrison sands of the Salt Wash widespread the by a reddish brown mUdstone the upper reddish brown mUdstones of the Summerville from the reddish brown mUdstones of the lower |
