GE Sedimentary processes and products

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Presentation transcript:

GE0-3112 Sedimentary processes and products Lecture 7. Aeolian sediments Literature: - Leeder 1999. Ch. 16 Aeolian sediments in low-latitude deserts (See also Ch. 8 & Ch. 13). Geoff Corner Department of Geology University of Tromsø 2006

Contents 7.1 Aeolian environments 7.2 Desert types and distribution 7.3 Sediment flow paths 7.4 Dunes and draas 7.5 Desert facies and architecture

Aeolian environments Types: Characteristics: GEO-3112 2006 Aeolian environments Types: Deserts and semi-arid regions Beaches and sabkas Sandy river banks Periglacial regions Characteristics: Lack of vegetation Moderate to strong winds Mobile sand and silt sediment

Aeolian GEO-3112 2006 Definitions Desert: arid zone having a large deficit of precipitation (P) in relation to evaotranspiration (ET) Definitions/subdivision (P/ET ratios): Hyperarid: <0.03 Arid: 0.03-0.2 Semiarid: 0.2-0.5 Subhumid: 0.5-0.7

World distribution of deserts (arid, hyperarid) and other dry areas. Aeolian GEO-3112 2006 Southwest N. America Gobi Sahara Arabia Atacama (Chile) South-central Australia Namib Kalahari Patagonia (Argentina)) World distribution of deserts (arid, hyperarid) and other dry areas.

Desert types and distribution Aeolian GEO-3112 2006 Desert types and distribution Trade wind deserts (subtropical high-pressure) N. Africa, Arabia, south-central Australia. Atacama, Namib (cool offshore current). Continental deserts Central asia. Rain shadow/continental western N. America, sub-Andean S. America.

Sub-tropical high pressure cells and trade winds. Aeolian GEO-3112 2006 Sub-tropical high pressure cells and trade winds.

Rain shadow effect (lower precipitation E of mountains) Aeolian GEO-3112 2006 Rain shadow effect (lower precipitation E of mountains)

Deserts and aeolian deposits GEO-3112 2006 Deserts and aeolian deposits Rocky deserts Sandy deserts Most deserts contain rock outcrops and aeolian, lake or playa, and alluvial deposits Loess deposits in and beyond deserts

Distribution of aeolian deposits GEO-3112 2006 Distribution of aeolian deposits Presently active sand dunes. Glacial maximum sand dunes. Loess (mostly glacial maximum).

Sediment transport Sand Sand-flow map for Saharan ergs Aeolian GEO-3112 2006 Sediment transport Sand Sand-flow map for Saharan ergs

Dust Aerosol dust budgets for the Sahara and adjacent Atlantic Oceann. Aeolian GEO-3112 2006 Dust Aerosol dust budgets for the Sahara and adjacent Atlantic Oceann.

Aeolian GEO-3112 2006

Dune types and interdune terrain Aeolian GEO-3112 2006 Dune types and interdune terrain Bedrock and erosional forms (yardangs) Dunes Barchans Transverse dunes Linear dunes Star dunes Lakes and (saline) playas Alluvial fans and stream beds

Saharan dunes Barchan dunes Star dunes Linear and compound dunes Aeolian Barchan dunes GEO-3112 2006 Star dunes Linear and compound dunes Interdune and intererg areas Linear dunes Saharan dunes

Aeolian GEO-3112 2006 Barchan dunes Star dunes

Aeolian GEO-3112 2006 Linear dunes

Linear and compound dunes Aeolian GEO-3112 2006 Linear and compound dunes

Aeolian GEO-3112 2006 Transverse dunes? Star dunes Namib desert

Aeolian GEO-3112 2006 Uluru (Ayer’s Rock), Central Australia

Controls on sand deposition Aeolian GEO-3112 2006 Controls on sand deposition

Facies and architecture Aeolian GEO-3112 2006 Facies and architecture Facies sequences at the margins of an erg.

Aeolian Aeolian architecture GEO-3112 2006 Interdune Dune

U. Jurassic Entrada sandstone, W. USA. Aeolian GEO-3112 2006 U. Jurassic Entrada sandstone, W. USA.

Permian Rotliegendes, NW Europe Aeolian GEO-3112 2006 Permian Rotliegendes, NW Europe

Active dry phase Wet phase Formation of ’supersurface’ Aeolian GEO-3112 2006 Active dry phase Formation of ’supersurface’ Wet phase

Aeolian GEO-3112 2006

Further reading Galloway & Hobday 1996. Ch. 10. Eolian systems. Aeolian GEO-3112 2006 Further reading Galloway & Hobday 1996. Ch. 10. Eolian systems. Kocurek, in Reading (ed.), 1996. Ch. 5. Desert aeolian systems.