lecture #1 Chem rocks

Terrigenous Sediments

form from weathering/erosion of preexisting rocks, everything we have studied up to now. usually transported into the basin of deposition

Chemical Sediments

direct chemical precipitation of minerals in the depositional basin

Biogenic Sediments

precipitated within the depositional basin by a biogenic agent, including bacteria

rock with most carbonates

biogenic rocks

clastic

refers to any grains that are transported before final deposition

chemical and biogenic sediments

are commonly non-clastic

Siliciclastic influence

High clastic input (Bangladesh) kills reefs; minimal input (Great Barrier Reef) allows carbonates to grow.

Hydrocarbon source rock

Upper Cretaceous- Turonian

Lower Cretaceous- Aptian

Upper Jurassic- Kimmeridgian

Upper Jurassic- Oxfordian

how are ions introduced into rivers and ground water by

chemical and biological degradation of primary mineral grains creates a dissolved load

How do you concrete the salt into the basin? (Why seawater has dissolved salts)

Evaporation removes water and leaves salts behind

To be freshwater, the salt amount must be

less than one gram per liter

% of the weight that is dissolved salts in salinity

3.5

What mineral do u get when mixing sodium and chloride?

Salt

Tops Ions?(most abundant)

Chloride and Sodium

Ocean salinity is stable cuz?

input rate= removal rate

how many elements got a measurable value in sea water? ( but they make up only 3.5 of the weight

85

what’s the order of evaporation for sea water?

-calcium carbonate

-gypsum/anhydrite( 19% of water remaining)

-halite(9.5% left)

-bitter salts(4% left)

volumes of precipitants for sea water evaporation

most common rock type for carbonate

limestone(chalk)

most common chemical composition

(CaCo3)

most abundant modern and ancient chemical sediment

limestone

major host rock for hydrocarbons

limestone

Gypsum facts

precipitated in restricted marine bodies/saline lakes

CaSO4*H2O

Anhydrite facts

Gypsum converts into this by dehydration ( depths of over 50-60C)

Selenite

A giant, bladed crystal variety of Gypsum

what are the most common bitter salts with evaporation of sea water

sylvinite( KCl)and carnallite (MgCl)

carbonate equilibrium

pH control with carbonate equilibrium

increase in CO2 → lowers pH and dissolves CaCO3

decrease in CO2 → raises pH and precipitates CaCO3

what causes the loss of CO2 ( control of CO2)

increase in temp and decreases in water pressure

Why reefs/carbonates are found in low latitudes?

warm water holds less CO2/ promotes CaCO3 precipitation

Equator ( middle section of the continents)

warmer waters area shows in a greater increase in reefs ( Southwest Asia and South America)

What is the correlation between ocean temperature, latitude, and calcium carbonate saturation?

Low latitudes, higher temps, more saturated= more probability of reefs

what makes a carbonate sediment?

inorganic precipitation of CaCO3 ( examples are called Ooids and whitings)

what are the 3 ways that biogenic carbonate is made

direct extraction- skeletons/shells

photosynthesis- plants/bacteria remove CO2( precipitation)

fecal pellets- repackaging of sediments

vadose zone

Unsaturated zone above the water table where dissolution occurs

karst

Landscape formed by this dissolution

Speleothems

Precipitation features inside caves

when water is getting out of the ground( gw precipitation) it’s called

discharge

water coming in from the ground within the cave ( gw dissolution)

recharge

Phreatic Zone

Saturated zone below the water table

Geodes

Form slowly in the phreatic zone via mineral replacement

Travertine

Carbonate precipitates from springs, often in thin layers.

Spring Controls

Precipitation is controlled by changes in temperature, chemistry, or flow rate.

chert

rock made of Amorphous Silica-SiO2

Formed abiotically or from Diatoms(biotic hard parts)