A Playa Lake Usually Contains Laminated Mudstone

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.

A playa lake usually contains laminated mudstone.

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. Laminated to thick bedded. At lake hill the lower unit contains the cephalopod armenoceras and several species of the. This resulted in the large scale deposition of sandy debris flow in the deep lake region.

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 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. This sometimes initiates microcrack formation the widening of existing cracks or disintegration of the rock mass. Is interpreted as subaerial playa mud flat deposits.

Pink and red orthoquartzite. 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. In figure 2 the maximum expansion strain ɛ max is plotted against the strength reduction index i s which is defined as i s 1 s cw s cd 100 where s cd and s cw. An aggregate of dolomite mineral crystals that are usually microcrystalline.

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. 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. It form sin very salty lagoons and desert playa lakes detrital rocks mudstone sandstone breccia and conglomerate. Perennial lake parasequences are capped by red siltstones and paleosols representing dry playa environments similar to those in the playa parasequences.