Need some help with this one on my homework! Thanks! Question 3 Not yet answered

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Need some help with this one on my homework! Thanks!

Question 3 Not yet answered Points out of 1.00 On a hike you find a sedimentary rock that is made up of moderately well sorted, sub-rounded grains that are 1 mm across. Looking closely, you see the grains are made of quartz and potassium feldspar, lacking mafic minerals and rock fragments. How far had that sediment moved from its source before it was lithified? Select one: O a. Very long distance o b.Intermediate distance Flag c. very short distance

Explanation / Answer

Answer:

b. intermediate distance

Justification:

If a sedimentory rock does not have mafic minerals and rock fragments in it, the distance it has moved is intermediate because it could be only transported by water (rivers and streams) or wind within a range of intermediate distance.

Explanation:

Formation of Sedimentary Rocks

The term sediment refers to loose particulate material (clay, sand, gravel, etc.). Sediment becomes a sedimentary rock through a process known as lithification. Lithification begins when rocks are buried and become compacted. The pores of the rock then become filled with cement, and certain minerals begin to recrystallize. Sediment is loose material and sedimentary rock holds together when you pick it up.

Sedimentary rocks can be divided into two major categories: clastic and precipitated (or chemical). Since the character of the sedimentary rock is largely controlled by the sedimentary environment, they have a story to tell about the climate, the environment, and even who lived at the time they were laid down.

Clastic sediments

Clastic sediments form from particulate material carried by wind or water. They can form on land by the action of rivers, glaciers and lakes (terrigenous sediments), they can form in the oceans as particulate matter spreads out from the mouths of rivers (deltas), and they can form at the ocean/land interface, otherwise known as the intertidal zone (or beach!).

The major classification of clastic rocks is by grain size ranging from boulders (>256mm) to clay (<.0039mm). (Please study Table 7.5 in your book). The ability of water (or wind) to carry particles depends on its speed. Fast moving water can carry larger clasts. Still water drops its load entirely and the rate that a particle falls through water is a function primarily of its size (smallest particles stay afloat the longest). These principles allow the interpretation of sedimentary structures (such as graded bedding, ripple marks, and various kinds of stratification) to be interpreted in terms of the environment of deposition.

Chemical Sediments

Sedimentary Structures

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