A Playa Lake Usually Contains Laminated Mudstone

An aggregate of dolomite mineral crystals that are usually microcrystalline.

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. This resulted in the large scale deposition of sandy debris flow in the deep lake region. Perennial lake parasequences are capped by red siltstones and paleosols representing dry playa environments similar to those in the playa parasequences. It form sin very salty lagoons and desert playa lakes detrital rocks mudstone sandstone breccia and conglomerate.

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. 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. This sometimes initiates microcrack formation the widening of existing cracks or disintegration of the rock mass. Is interpreted as subaerial playa mud flat 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. 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. At lake hill the lower unit contains the cephalopod armenoceras and several species of the. Tuff beds selected for 40ar 39ar analysis occur within laminated mudstone are matrix supported and lack evidence of reworking.

Mudstone and shale are highly susceptible to slaking and undergo considerable expansion on wetting. 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. 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. Laminated to thick bedded.