A Playa Lake Usually Contains Laminated Mudstone

From 1 8 billion year old metamorphic rocks exposed in the black mountains to recent playa sediments deposited in the valley basins death valley possesses a superb geologic record.

A playa lake usually contains laminated mudstone.

Playa lake laminated mudstone siltstone evaporites rock salt rock gypsum and others glacial environments outwash much like braided streams horizon bedded conglom and cross bedded sandstone mudrocks not there. Eocene lake gosiute filled a large part of the green river basin in sw wyoming fig 1 and in this lake the grf was deposited with its largely laminated kerogen rich micrites oil shales that grade laterally into massive lime stones or siliciclastic mudstones. Playa lakes are characterized by laminated muds evaporites and mudcracks rock description of an outwash plane environment an outwash plane is characterized by sands silts clays and braided stream deposits. The base of an ideal perennial lake parasequence consists of laminated black shale overlain by laminated or massive gray mudstone both interpreted as perennial lake facies.

Burrowed massive 11111ds1011e dominated by sediment filled tubes having constant diameters and commonly containing soft sediment deformation features deep narrow mud cracks and lacustrine fossils is interpreted as intermiuently exposed shallow lake or swampy flood plain deposits. Is interpreted as subaerial playa mud flat deposits. At lake hill the lower unit contains the cephalopod armenoceras and several species of the. Laminated to thick bedded.

It form sin very salty lagoons and desert playa lakes detrital rocks mudstone sandstone breccia and conglomerate. This resulted in the large scale deposition of sandy debris flow in the deep lake region. Pink and red orthoquartzite. Tuff beds selected for 40ar 39ar analysis occur within laminated mudstone are matrix supported and lack evidence of reworking.

This sometimes initiates microcrack formation the widening of existing cracks or disintegration of the rock mass. Mudstone and shale are highly susceptible to slaking and undergo considerable expansion on wetting. An aggregate of dolomite mineral crystals that are usually microcrystalline. The deposits of eocene lake gosiute that constitute the green river formation of wyoming contain numerous tuff beds that represent isochronous correlatable strati graphic markers.