Lecture 7 - Facies Models Part II Flashcards
What are aeolian desposits?
this is where incoming radiation heats the lower lats and takes mositire from here and moves it to the high lats, meaning a dry arid enviroment such as a desert
what is sandblasting?
Grains move just above the sediment surface by saltation colliding with toher grains
What is sandblasting effects on pebbles?
Sand blasting gives pebbles curbed or straight sides theses are called Ventifacts
What is the most common desert mineral
Quatz
What else occours here?
microscopic pitting and frosting
What is the sorting and rounding of these sand grains
Well rounded and well sorted
Wind transport properties
Wind is obvsiously much less dense than water so a really strong wind is needed to transport size grains.
What does this wind form
Dunes, either around obstacles forming two dunes then the weak eddies allow the dunes to grown to form one large sand dune.
explanation of sanddune migration
Sand dues are eroded or the windward side and deposited on the lee slope. Successive slip faces make for cross bedding.
Techtonic setting for sand dunes
Inland basins, 10-30defrees or behind mountain rain shaddows
Geometry of sand dunes
Thick tabular bodies can go for 100s of km
Sedimentolofy
Enormous cross cut beds some mud cracked shales desert pavement gravles well rounded quatx rich no fine matrix
Fossils?
Rare footprints, insect burrows
What do these cross cut beddings in the rock record indicate
Past wind directions
Deltas explaination
Sedimenty desposits at river mouths, deltas prograde (build out)
What are the three types of deltas
Small, Lobate, elongate
One delta can contain three enviorments, what the they?
Delta plain, delta front, prodelta
Techtonic setting of a delta
Passive margins and subsiding basins
Geometry of a delta
Roughly tirangluar plans
Wednge shape in cross section
Sedimentology
Coarse sand to fine mud, sometimes coal ripples and cross bedded sandstones
Fossils
Organic matter common in interdistribuaty areas
Preitidal envroiments explainations
found between high and low tide, found in costal regions where river sediments < marine eriosin, Unlike prograding deltas, sediment in peritidal environments is reworked by tides
Peritidal tectonic settings
passive margin with shallow coastal regiions
Geometry
Tabular, local sand bodies paralell to shorine
Sedimentology
Sand and mud cracks, hering bone cross cutting bedding
Fossils?
Oysters, plant remans and algea mats
