1a - intro to clastic sediments

what is clastic vs non-clastic?

clastic - made up of fragments (clasts) of existing rocks

non - produced by precipitation/evaporation

what are the features of clastic rocks?

clasts - sediment grains

matrix - mass between large grains

cement - material binding grains together

porosity - pore spaces

what are the sources of clastic sediments?

erosion of pre-existing rocks

chemical/mechanical weathering (esp high hinterland areas + orogenic belts)

why is there a lot of clastic sediment near high hinterland areas?

up lifted crust = inc erosion + inc transport

create gravitational potential/gradient for sediment to move down

what is mechanical sieving?

pass sediment through diff size mesh

plot data on cumulative curve

problem - dont often have large enough sample size (need truck load)

what is laser diffraction?

light diffracted from particles passing through laser determines its diameter

produces large number of size classes

what is sorting?

measure range of grain size present in sample

indicate transport process and energy levels

what is grain shape?

describe shape of clasts using length of 3 perpendicular axes

measure degree of roundness + sphericity

what is fabric?

preferential orientation of particles in sediments

can use for paleocurrent analyses and depositional processes

what is a/b-axis alignment?

long axis (A) aligned with flow direction

intermediate axis (B) aligned with flow direction

what is framework?

matrix supported - most grains not in contact

clast supported - most grains in contact

what is composition?

mineralogical composition