Aeolian GEO3112 2006 GE 0 3112 Sedimentary processes

Aeolian GEO-3112 2006 GE 0 -3112 Sedimentary processes and products Lecture 7. Aeolian sediments Geoff Corner Department of Geology University of Tromsø 2006 Literature: - Leeder 1999. Ch. 16 Aeolian sediments in low-latitude deserts (See also Ch. 8 & Ch. 13).

Aeolian GEO-3112 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 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 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: § Arid: § Semiarid: § Subhumid: <0. 03 -0. 2 -0. 5 -0. 7

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

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.

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

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

Aeolian 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

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

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

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

Aeolian GEO-3112 2006

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

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 Linear dunes GEO-3112 2006

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

Aeolian GEO-3112 2006 Controls on sand deposition

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

Aeolian GEO-3112 2006 Aeolian architecture Dune Interdune

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

Aeolian ► Permian Rotliegendes, NW Europe GEO-3112 2006

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

Aeolian GEO-3112 2006

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