Continental: Lacustrine Facies
Impt. Facts:
Lakes make up 1% of the earth land surface
Largest modern lake surface area in the world = Caspian Sea (436,000
sq. km.)
Deepest (greatest volume) modern lake = Lake Baikal (1700 m depth)
Origins
a. tectonic motion, faulting and rifting - groundwater flow and
springs
Lake Bonneville, East African rift lakes, Caspian
b. glacial processes
Great Lakes
c. landsides and mass movements
d. volcanics - ponded flows and caldera
Yellowstone, Creede
e. eolian deflation and interdunes areas
f. fluvial migration - oxbow and levee lakes
Climatic Links
a. lake level = balance of evaporation and precipitation
b. lake chemistry = humidity and runoff water chemistry
c. lake controlled weather (i.e. snow effect)
Physical Lake Processes (hydrology, climate; Fig. 9.26, p.
297)
a. wind
b. river inflow
c. atmospheric heating and stratification
d. surface barometric pressure
e. gravity
Lake Characteristics
a. hydrologically open lakes systems
inflow and precipitation balanced by outflow
b. hydrologically closed lake systems
no major outflow
evaporation and infiltration exceed inflow
c. low wave energy, so all coarse sediments confined to shallows
d. 10X greater sedimentation rates than marine environments
e. no tides
f. varves - dark = cold high OM, light = warmer higher sed input
g. OM and CO2 sinks
h. organic processes
skeletal precipitation, respiration/photosynthesis
bioturbation, plant remains, geomicrobiology
i. sedimentary versus chemical precipitation
j. open to closed system evolution
Lake Systems
Open (Fig. 9.28, p. 300)
Closed (Fig. 9.29, p. 301)
Continental to Marginal Marine: Glacial
Glacial = permananent accumulations of ice and snow
a. high latitudes at all elevations
b. lower latitudes at high elevations - above snow line
c. continental glaciers
d. marine glaciers
Environmental Settings - all environments in contact with glacial
ice
a. basal or subglacial zone - bottom surface of glacier
b. supraglacial zone - top surface of glacier
c. ice-contact zone - laterl sides of glacier
d. englacial zone - interior of glacier
e. proglacial zone - glacial meltwater (fluvial, lacustrine,
marine)
f. periglacial zone - areas beyond direct melt water affect
g. ice-rafting - debris transported in floating ice blocks (icebergs)
h. dropstone - debris dropped from melting icebergs
Composition and Deposition (Fig. 9.35, p. 309)
a. heterogeneous mix of sediments (extremely poorly sorted)
b. front of glacier is point where melting/sublimation rate >
or = accumulation rate
c. ice flows forward toward the melting/sublimation zone
internal deformation - ice crystal distortion
basal sliding
d. glacial drift (till [Scottish word], diamictites)- sediments
deposited by glaciers
e. glacial erratic - large boulders
f. morains - till deposits at margins of a glacier (French word)
g. loess (German word) - windblown silt-sized till
h. esker - sinuous meltwater channels at base of glaciers filled
with sands/gravels
Distal Successions (Fig. 9.43, p. 319)
a. only massive diamictites
b. upward fining (diamictite - braided fluvial - lacustrine)