Sedimentary Rocks

Assignment: Complete Sedimentary Rock Worksheet, pg. 147.

Sedimentary Rocks are derived from pre-existing materials, having been broken down as a result of __________________ and _________________ weathering and then deposited elsewhere.

Later, the material is lithified. Lithification is the ___________ and/or _______________ of loose sediments into rock.

• The types of sedimentary rocks formed are determined by where they formed and what they are made of.

Three classfication types

1. The first type is clastic sedimentary rocks derived form inorganic sediments that have been broken down by mechanical weathering and then transported by gravity, wind, water, ice, etc and deposited elsewhere. Since these rocks are often formed in water, they can have lots of interesting features like ripple marks, cross beds and mud cracks!
2. The second type is chemical sedimentary rocks derived form inorganic chemical precipitates. These rocks were formed not from fragments of pre-existing material, but from material which was ______________ and then later precipitated. They can be course or fine grained. Think rock candy!
3. The third type of sedimentary rock is biogenic sedimentary rock derived from organic remains- both _______________ and plants. Only sedimentary rocks have fossils but the rock must be FILLED with fossils to be considered organic sedimentary.

Textural Terms

Clastic- clastic sedimentary rocks are composed wholly or partly of ____________ (as in sandstone and graywacke).

Clastic rocks are further described in terms of the ____________ of these fragments or grains.

• The sediment sizes in increasing order of size are: _______________, _______________, _____________, _____________, __________________, __________________ and ______________.

In addition to size, the ________ of the grains is also used to classify sedimentary rocks.

• Angular (as in breccia) or rounded (as in conglomerate) are generally used.
• ____________ in grain size is also important. Rocks composed of mostly one grain size would be considered well sorted (as in sandstone). A wide variation of grain sizes would be considered poorly sorted (as in arkose).

Crystalline- a sedimentary rock composed of interlocking _______________.

Microcrystalline- crystals are too small to _____ without magnification.

Oolitic- composed of tiny rounded particles like beads or tiny pearls called ooliths. Ooliths form when material, usually _____________, (as in oolitic limestone) is deposited in concentric layers around a central nucleus such as a sand grain.

Dense or amorphous- very ___________, non or micro-crysatlline rock, oftern displaying concoidal fracture (as in chert).

Bioclastic- composed of fragments of ____________________ (as in coquina).

Miscellaneous Terms

Matrix- the finer-grained material ___________ the larger grains in a sedimentary rock.

Fossiliferous- prefix for rocks containing evidence of ________________.

Calcarious- prefix for rocks containing minor amounts of _______________ minerals.

Arkosic- prefix for rocks containing minor amounts of ________________.

Graywacke- ________ mixed with a lot of mud.