sedimentary rocks Flashcards
sediment
material weathered from pre-existing rocks
lithification
process of converting sediment to sedimentary rocks
- depostion forms pile of sediment with lots of pores
- pile grows thicker and the weight compacts layers
- grains cemented by remobilization of some minerals through pressure solution. Water moving through pores ppt. minerals
significant decrease in pore space, increase in strength
common example of sedimentary rock
quartz grains with calcite cement
5 groupings of sedimentary rocks
- clastic - made of clasts (pieces of weathered mineral) e.g. sandstone
- biogenic/bioclastic - made of particles originally from living organisms e.g. shells to limestone
- organic - made of compressed and heated plant material e.g. coal
- chemical - made from ppt. dissolved particles e.g. evaporite, ironstone
- volcanicalstic - same as clastic but clasts are of volcanic origin
order these in terms of clast size smallest first:
mudstone, conglomerate, sandstone
- mudstone
- sandstone
- conglomerate
what is a clue to transportation distance of clasts?
further transport distance = smaller and rounder clasts
3 categories to categorise clastic rocks
- compostition of clasts - quartz, feldspar, clays, etc
- presence of matrix
- type of cement
Breccia and conglomerate
a clastic sedimentary rock with large angular clasts in cement
mudstone vs shale
mudstone breaks into blocks, shale is fissle and breaks into thin layers along parallel planes
sandstone vs siltstone
cant see clasts with naked eye in siltstone and sandstone feels grittier
limestone is an example of a ________ sedimentary rock. explain formation
biogenic.
shells, ppt. of CaCO3 from water.
can look crystalline
coal
organic.
forms from plant debris in swampy environments.
burial drives off volatile and compacts coal. Higher grade = fewer volatiles
most common form of chemical sedimentary rocks and where they form
evaporites. e.g halite from salt rich water. form in VERY arid climates
bedding in sedimentary rocks
layers of rock that have lithological, textural, or structural differences from layers above/below.
represent changes in environment
what is grading?
beds with largest sediments on the bottom and smallest on the top, caused by dissipation of transport energy