Based on Earth History, answer the following questions correctly. Please answer

Question

Based on Earth History, answer the following questions correctly. Please answer this if only capable of answering, and don't copy paste an article from google.

- List three types of basins as they relate to different phases of the Wilson cycle and in each case, describe the mechanism for creation of accommodation space.

- What facies successions might you find in a passive-margin setting, an Andean style foreland basin, or a Laramide style basin? What depositional environments might you find evidence for in each?

- What periods in Earth history were known to be icehouse worlds with polar ice caps, and what is the evidence?

Explanation / Answer

Answer:

-Three types of basin as they relate to different phases of the Wilson cycle are:

a. Rift basins: Rift basins form in earlier stages of Wilson Cycle, more precisely, stage B, when rifting splits the continet into two pieces. Lithosphere stretches horizontally and thins vertically. Axial rifts are tens of kilometers across and elevation from the rift valley to the mountain crest is as much as 4-5km. Rift valleys are structurally block-fault graben bordered by horst mountains on either side. With time, the sea invades the valley. Small basins are created between the down-faulted blocks and the wall behind the fault. Diversity of sedimentary rocks are deposited in the graben, where facies change is very rapid. At the base of falt scarps arkosic breccia and conglomerate get deposited. Alluvial fan deltas are developed after the sea invades. The fans give way to braided rivers towards the basin axis and at this stage sediments accommodated in huge amount. The basin center gets filled with thinly laminated black clay and silt. The basin finishes filling in relatively short geological period (about 10 Ma).

b. Passive-margin basins: These form along the edges of the continents that are not plate boundaries. Passive-margin basin forms in Stage D of Wilson cycle when subsidence of stretched lithosphere continues after rifting ceases. In about 5-10 Ma, the horsts which were once well above the sea level starts to sink. Subsequently, the divergent plate margin basin cools and stabilize in about 110 Ma. In the meantime, great wedge if sediment gets deposited on the divergent margin, expanding and thickening from the feather edge of the continent side towards the ocean basin. Clastics are deposited from the eroded materials of the continet and carbonates are derived from chemical processes. Shallow-water marine deposits are mostly found here because of subsidence and deposition going on at a same rate.

c. Foreland basins: These basins form on the continental side of a mountain belt in the later stages of Wilson cycle, precisely stage F. The ancient wedge of divergent margin sediments gets compressed, folded into anticlines and synclines and faulted towards the foreland. Then, the sediments closest to the island arc get depressed down into earth by the force of the overriding arc. Barrovian metamorphism is observed here with presence of quartzite, phyllite and slate. Finally, inland from the mountain a foreland basin subsides into a deepwater basin filled with thick wedge of clastic sediments.

-In Passive margin setting, if it is present near a large river system, detrital sandstones and shales carried by river will get deposited, giving a fluvial facies model. Sedimentary environments include river channels, floodplains, deltas, beaches and depostion in the shallow water of continental shelf. It can also form in deep water continetal rise below. Deposition in this deep water environment is usually the result of turbidity currents - fluidized masses of sediment and water that tumble off the edge of the continental shelf, erode channels into the continental slope, and then are deposited on the continental rise and abyssal plain as the turbidity current loses energy.

In the Andean style foreland basin depositional environments the sediments are deposited in typically begin with black deep water shales. However, the large volume of sediment eroding from the mountain will quickly fill the basin in. Depositional environments typically begin with submarine fans which shallow upward to shelf environments, and then eventually terrestrial deposits (meandering and braided rivers.) Inland toward the craton the foreland basin shallows and the clastic wedge thins and becomes finer grained until it merges with sediments being deposited on the craton. In Bolivia, clastic sediments are mostly accumulated.

Laramide depositional systems in perimeter type basins are mostly fluvial, except in Powder river system, where lacustrine facies are also found. The nature of lacustrine environments in which the lacustrine facies of Lake Gosiute and Uinta were deposited is a topic of debate. Two hypostheses of deep stratified lakes and shallow playa lakes were given by Picard (1985) where the latter explains internal drainage enclosed by hydrologic barriers and that the former internal or external drainage. The best interpretation is accumulation of organic matter at the floors of large perennial lakes surrounded by lacustrine shoals and mudflats (Ryders et al., 1976).

-An icehouse earthis an earth that experiences ice age. Ice sheets are present and those wax and wane through glacial and interglacial periods. Greenhouse gases are less abundant and global cooling is observed. The earth is currently in ice house world period as evidence are there in continental ice sheets of Greenland and Antarctica

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