Unit 2 sedimentary rocks

What components should be included in a rock description?

• Size, sphericity, structures, colour, matrix,

• Size, shape, sorting, colour, composition, cement

• How the rock formed, how far the grains travelled, what they’re made of

• Sedimentary structures, name, colour, composition, phi

Describe the process of hydrolysis

• Limestone dissolves due to carbonic acid, releasing carbon dioxide

• Feldspars break down and leave only quartz

• Feldspars weather to clay minerals due to the H+ ions in water

• Feldspars dissolve due to acidic water, leaving more mature sediment

Why is quartz often the final remaining mineral?

• It is inert

• It has 2 cleavages

• It has a hardness of 7

• It has a high maturity

• It has no cleavage

What does sorting describe?

• How many different grain sizes are present

• How many different grain shapes there are

• The maturity of the sediment

• How many different types of minerals are present

What determines the roundness of a sediment

• How many cleavages the mineral has

• What the grains are made of

• How far the grains have been transported

• How much attrition and abrasion the grains have gone through

• How much erosion the grains have experienced

What will happen to a grain that is 0.3mm diameter and is travelling in a flow at 2cm/s?

• Erosion

• Transport

• Deposition

Describe the sorting of the sample

• Well sorted

• Moderately sorted

• Poorly sorted

Describe the shape of the grains

• Angular

• Subangular

• Subrounded

• Rounded

Which weathering process does this describe: warmth during the day causes the rock to expand, then as the rock cools overnight it contracts. As this repeat, layers fracture and break off.

• Freeze thaw weathering

• Insolation

• Carbonation

• Abrasion

• Attrition

What sedimentary structure is visible in this image?

• Ripple marks

• Flute casts

• Cross bedding

• Laminations