Sedimentary Rocks Lab

Question 1

Two sedimentary textures

Answer 1

Crystalline texture (crystals grown together) and Clastic texture (“aggregate of grains”; rocks cemented together)

Question 2

How does a clastic sedimentary rock form?

Answer 2

Clastic rocks come from loose, unconsolidated aggregate of mineral grains and rock fragments and subsequent cementation (gluing together) and compaction (squishing)

Question 3

How does a chemical sedimentary rock form?

Answer 3

Chemical sedimentary rocks form from the precipitation of minerals out of solution (sea, water, lakes, etc). Common chemical sedimentary rocks are limestone and rock salt.

Question 4

Framework

Answer 4

Packed clasts that are in partial or full contact with one another (basically the big rocks in sedimentary rocks that are held by the matrix and cement)

Question 5

Matrix

Answer 5

Consists of smaller grains that fill spaces between the larger framework grains

Question 6

Cement

Answer 6

Binds the framework and/or matrix grains to form sedimentary rocks. Cements form when a water-based solution is present within the pore space of sediment and minerals precipitate from this solution, partially or entirely filling the pores between sediment grains. The most common types of cement are quartz (silica), calcite, dolomite, hematite, and clay minerals

Question 7

Pore space

Answer 7

Non-solid space between grains that is filled with fluid (air, water, oil, natural gas)

Question 8

Conglomerate vs breccia

Answer 8

Conglomerate has rounded clasts and breccia has angular clasts. In both cases, clasts have to be 2 mm and larger, otherwise the rock will be considered a sandstone.

Question 9

Granule

Answer 9

2-4 mm

Question 10

Pebble

Answer 10

4-64 mm

Question 11

Cobble

Answer 11

64-256 mm

Question 12

Boulder

Answer 12

more than 256 mm

Question 13

Two types of clay

Answer 13

Mudstone (if massive) or shale (if fissile)

Question 14

Naming sedimentary rocks

Answer 14

When naming any sedimentary rock, it is very important to remember to include a grain-size modifier for the dominant clast size.

Question 15

3 types of roundness

Answer 15

Very angular, subrounded/subangular, well rounded

Question 16

How do you determine the maturity of a rock?

Answer 16

The more mature the rock is, the less clay (or none) it will have., Mature rocks are also well-sorted and have well-rounded clasts.