Chap 7 Sedimentary rocks

Question 1

Sedimentary rocks:

Answer 1

Product of chemical and mechanical weathering. Weathering process of
sediment forms solid minerals and dissolved ions.

Question 2

Diagenesis

Answer 2

= chemical, physical, and biological changes that take place after sediments are
deposited. It includes recrystallization (development of more stable minerals from less stable ones)
and lithification.

Question 3

Lithification

Answer 3

the conversion of sediment into rock via two main steps:

Compaction - a decrease in volume due mainly to loss of pore space. Broken minerals may have exposed charges that help them to stick together.

Compaction - a decrease in volume due mainly to loss of pore space. Broken
minerals may have exposed charges that help them to stick together.

Question 4

Clastic sediment:

Answer 4

solid mineral particles that are left behind after weathering, e.g. physically
weathered parts of original rock or minerals (e.g., clays) that form by chemical weathering.
Quartz and clay are the most abundant clastic materials.

Question 5

Chemical sediment

Answer 5

dissolved ions eventually precipitate into solid minerals. Ionic (dissolved)
sediment forms ionically bonded minerals (e.g., halite, calcite). Occurs both in water bodies
(oceans, lakes) and in pore spaces between other mineral grains.

Question 6

Detrital or clastic rocks

Answer 6

composed mainly of mineral grains weathered from pre- existing
rock and cemented together by precipitated minerals

Question 7

Chemical rocks

Answer 7

composed of minerals precipitated from water by biologic or inorganic
processes, or the remains of organisms.

Question 8

Angularity

Answer 8

indicates the degree to which grains have smooth or angular corners and edges

Question 9

Sphericity

Answer 9

Refers to the degree to which a clast is equidimensional

Question 10

Sorting

Answer 10

Describes the uniformity of the grain size.

o Well sorted: Uniform grain size + uniform energy (beach)

o Poorly sorted: Wide variety of grain sizes + variable energy (alluvial fan)

Question 11

Character of cement

Answer 11

 The cement is the minerals that fills sediment pores.

 Fluids with dissolved solids flush through pore system. Dissolved ions slowly crystallize in
(and fill) pores.

 Cementation varies in degree:
o Weakly cemented: Grains easily pulled from rock
o Strongly cemented: Grains hard to dislodge

 Common cements: quartz, calcite, hematite, and clay minerals