Geology Question: Please someone who majored in geology help!?

Question

Which enviroment would you be able to find:
plane beeding
cross bedding
symmetrical ripples
asymmetricla ripples
chert
limestone
dolostone

Answer 1

Centimetre to metre scale planar bedding is very common in sedimentary rocks, but is often particularly well developed in turbidites (typically deep marine rocks). Millimetre scale planar bedding is characteristic of many fine-grained sediments deposited in any low energy environments, away from strong wave or current activity.

Cross bedding is common in sediments/rocks deposited by rivers, wind-blown sands, and some shallow marine sediments. It requires unidirectional current activity (air or water) to form.

Symmetrical ripples are almost always found in rocks/sediments deposited in very shallow water, where the wave activity affects the bottom of the body of water, but other current activity is minimal. Commonly found in very shallow marine sediments and lake sediments. Requires a bidirectional current to form.

Asymmetrical ripples = small scale cross bedding. Common in shallow marine rocks, river sediments. Also common within individual turbidite beds.

Note that the different types of bedding are not all mutually exclusive.

Chert is commonly found associated with deep marine volcanic rocks (pillow basalts), where is probably forms as a chemical precipitate. Chert is also commonly associated with limestones (see below), where it probably forms by the dissolution and re-precipitation of silica derived from various beasties (sponges, diatoms etc.) that had silica shells.

Limestones are typically (but by no means exclusively) deposited is shallow seas, where the input of detrital sediment (sand, mud) is minimal.

Dolostone is usually formed by the secondary alteration of limestone