Earth History Sandstone & Shale Formation

Basin An area of relative low elevation where water and sediments collect.

Sandstone Basics A sedimentary rock that forms in a basin. It is made out of sand particles cemented together by a matrix. What environments could sandstone form in?

Matrix The material that glues sand together in sandstone

Sandstone Formation I 1. Sand is loosely packed soon after deposition

Sandstone Formation II 2. Sand gets compacted over an extended period of time.

Sandstone Formation III 3. Sand is saturated by a matrix dissolved in water.

Sandstone Formation IV 4. Sand becomes cemented together by matrix after the water evaporates away

Shale Basics A sedimentary rock that forms in a basin. It is made of silt and clay particles that are compacted until all water is squeezed out. Compaction – squeezing that occurs due to pressure

Shale Basics In other words, shale is composed of silt and clay from which the water has been removed. Where did silt and clay deposit on the stream table? How fast was the water moving at this location? What real environments could this happen in?

Why does shale sometimes have plant fossils? Lots of plants grow in swamps, and when they die and get trapped in the sediment, they become fossilized.

Principle of Original Horizontality Layers of sediment are generally deposited in a flat and horizontal position. Each new layer of sediment does not mix with the older ones.

Uniformitarianism The present is the key to the past. The way things happen today is the way things happened in the past. Things in geology take millions of years to happen (rock forming, canyons being carved out, etc.) The way we see things happen today is also how they happened millions of years ago.