310lect3

Uplands

I) Geologic Foundation

A) Characterization

1) Sedementary Rocks

2) Coastal subsidence

3) Isostatic Uplift

B) Basement Rock

1) Sabine Uplift

2) Monroe Uplifts

a anticlines

b provide traps for oil and gas deposits

C) North Louisiana Salt Basin and Missisippi Salt Basin

1) Between the two Uplifts

2) Salt Domes-oldest rock in Louisiana at the surface

D) South Louisiana

1) Normal Faults-subsidence

2) Baton Rouge Fault Zone-most surface displacement (20ft)

3) Slow non-seismic creep

4) http://www.es.anl.gov/htmls/transport.html

II) Tertiary Hills

1) Called the belted coastal plain

2) Deposited during the tertiary as sediment

3) Lithification

4) Various resistant strata that run east west

5) Eroded by rivers

B) Kisatchie Wold

1) Resistant sandstone

2) Various parts of the wold

3) Runs east-west of Alexandria

4) Antecendent river-Ouachita cut through wold and then was incised there.

C) Nacodoches Wold

1) Has highest elevations, but is not as impressive

2) Mt. Driskill 535

3) Influenced by the Sabine Uplift

4) Not east-west like most of the coastwise outcrops

5) Red River cuts through twice

6) Dolet Hills-rockier, because of their resistant capstones

7) Ouachita Hills

a where Ruston is

b rolling topography

c Ouachita River cuts into the eastern flank creating the Ouachita escarpment.

d Sabine Uplift does not affect the surface, but subsurface gas fields

III) Pleistocene Coastwise Terraces

1) Waxing and waning of glaciers

2) Sediment created the terraces

3) Former deltas and flood plains

4) Step-like terraces, subsidence and isostatic uplift

B) Three major Terraces (see map 3.6, fig 3.7)

1) Upland Complex

a Coarser sands and gravel, highly oxidized (Citronelle)

2) Intermediate Complex

a Smaller, sands and silts, narrow band

3) Prairie Complex

a Sand, clays and silts

b Just above the Mississippi River alluvial plain

c Poorly drained

4) Deweyville Complex

IV) Loess Deposits

A) Wind deposited silts

B) Pleistocene-aged and from the River alluvium

C) Sometimes very thick (100 ft) near bluffs

D) Tan and silty, with snail shells

E) Outcrops as cliffs sometimes

F) Easily eroded

G) Fertile, but abused during many years of cropping (West Feliciana)

H) Sunken “gut” roads, from the easily compacted loess

V) Pimple Mounds

A) Low round hills

B) Unknown origin

VI) Salt Domes

A) Jurassic aged

B) 4-8 miles down

C) lighter than rock and will flow plastically upward

D) is eroded/dissolved by ground water

E) Interior and Coastal Saltdome band

F) Mostly not noticeable on the surface

G) Makes small hills (Five Islands)-forested high ground

1) Collapse fault-where salt domes form, the mother bed sinks (like squeezing a balloon)

H) Makes lakes too where dissolution is great, and collapse occurs

VII) Conclusion