(Earth Science) Sedimentary Rocks Identification Assignment. For Part 2 of this

Question

(Earth Science)

Sedimentary Rocks Identification Assignment.

For Part 2 of this assignment, you need to compare the environments listed in table 2 and the descriptions and rock names you listed in Part 1.

Note: I have already done Part 1 of this assignment and provided Part 1 Sedimentary Rocks Table for it. Also, the environments listed in table 2 and the lines that need to be filled in for Part 2 of this assignment is provided below as well.

Part 1 Sedimentary Rocks Table:

Table 2:

Lines that need to be filled in/out for each sedimentary rock sample that is provided in Part 1 Sedimentary Rocks Table:

Rock Nam e Other ROCK SAMPLE ROCK TYPE | COMPOSITION | TEXTURES Grain Size Shape, ect) Observations Mostly quartz Mostly sand Quartz grains (weatheredmm) from other rocks) Clastic Presence of (1/16 mm-2 Sandstone some dark mineral/rock fragment. Clastic Shale Mostly rock Mostly clay and mineral(K1/256 mm) fragments (weathered from other rocks) Splits easily fissile Biogenic Mostly shells Poorly Commonly marine environment. Coquina consolidated mass of shells & shell fragments or shell fragments may or may not be visible with the naked eye) and/or very fine- grained calcite (mud); effervesces in acid Scratches glass; conchoidal fracture Chemical Mostl Microcrystalline Chert varieties of quartz (chalcedony, flint, opal etc Clastic Mostly rock Mostly gravel Conglomerate Rounded and mineral(2mm) fragments (weathered from part can be minerals or

Explanation / Answer

Answer:

G (Quartz sandstone): Desert, Beach, Shallow sea. Sandstone are found wherever the deposits of silica-rich sediments may occur followed by compaction and lithification. The most common sandstones are seen in desert where they show spectacular examples of cross-bedding (formed by the change in direction of the wind that deposited the sand particles).

H (Shale): Lakes (if they are deep enough), Deep sea, Deltas. These are clastic rocks commonly found where the water is deep and generally tranquil enough for fine clay particles to settle down and undergo compaction.

I (Coquina):Shallow Sea, Lakes, Reef. These rocks are of clastic, biogenic material and show beautiful assortments of shells cemented together by a calcareous composition.

J (Chert): Shallow sea (chemical), deep sea (chemical). Chert is formed by the alteration of calcareous rocks like limestone and mainly involves the replacement of CaCo3 (calcium carbonate) with Silica (formation of quartz is common).

K (Conglomerate): Glacier, River, Delta. Conglomerates show poor sorting that is you can see big rock fragments embedded in a matrix (cement) of finer composition. These kind of rocks are formed where a medium (water or snow), have strong currents to carry the bigger rock fragments and deposit them where their velocity is checked- depositing them with the finer matrix that the current carries with the flow as well. This can happen along river channels, at glacier (especially during avalanches) and deltas (where flood plains can create an ill-sorted deposit).

Fun fact-the more angular the grains are in a conglomerate, the lesser distance it has travelled while the more rounded grains have travelled over a big distance through which the grains have undergone erosion and smoothing.

L (Rock Gypsum): Lake (chemical).Gypsum is formed where there is enough content of calcium and sulphates. They are easily soluble in water and when the water evaporates, a fresh layer is precipitated every time the place is refilled with water of the same content- giving rise to massive gypsum deposits over time.

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