Chapter V: Sedimentary Enviornments Flashcards
What kinds of nonmarine sedimentary deposits reflect arid environmental conditions?
gravelly alluvial fans; cross-bedded gravels and sands; shallow playa lakes and salt flats; dunes of clean, cross bedded sand; mudcracks;
What kinds of nonmarine sedimentary deposits reflect cold environmental conditions?
Glacial sedimentary deposits
What kinds of deposits indicate the presence of rugged terrain in the vicinity of a nonmarine depositional basin?
coarse grained alluvial fans;
In what nonmarine setting do gravelly sediments often accumulate?
Mountains, in braided streams/alluvial fans;
What patterns of occurrence and sedimentary structures are shown by; meandering rivers, deltas, and turbidity currents?
Meandering Rivers:
graded beds; point-bar deposition; muddy flood plain sediments;
Deltas:
upward-coarsening sequence; shallow water sands over deeper water muds; barrier islands;
Turbidity Currents: graded beds (turbidites); calcareous and siliceous ooze;
What are the depositional environments of a barrier island-lagoon complex?
cross-bedded tidal deltas; tidal flats
What features typify sediments that accumulate in the centers of lakes?
thin horizontal layers; few burrows; absence of marine fossils
How do stromatolites form?
Cyanobacteria traps mud then grows through it, forming layer after layer which accumulate to form stromatolites
Describe the kind of rock found in a typical organic reef.
Carbonate sedimentary rock. Calcium Carbonate
Where is a lagoon in relation to a barrier reef? In relation to an atoll?
Lagoons lie behind long barrier islands and within atolls
Which features of carbonate rocks suggest intertidal or supratidal deposition?
algal lamentation and stromatolites
what types of sediments and sedimentary structures usually reflect deposition in a deep-sea setting?
pelagic sediments; calcareous ooze; silicous ooze; formed into turbidites
siliceous ooze
carpets deep sea floors; made of skeletons of two groups of organisims, phytoplankton (nontropical) and radiolarians
Glacial Features
scoured, scratched rock surfaces (striations); poorly sorted gravelly sediment (glacial till); dropstones; associated lake deposits with annual layers;
moraines, lithified till;
humus
organic matter which gives topsoil its black color
caliche
precipitated deposits of calcium carbonate (warm climates)
oxisols
soils rich in iron oxide
varves
annual pairs of coarse grained/fine grained layers in lake beds
playa lakes
lakes in areas with interior drainage, usually temporary
braided streams
complex network of streams on an alluvial fan
tempestites
thin, sandy beds produced by storms over usually muddy shelves
talus
rubble pile fallen from the wave-swept reef front
oolites
spherical sediment formed by ooids
