4.5 Alluvial fans. Basin margin (fault) Feeder canyon Active depositional lobe Fan apex Fan toe Alluvial fans. - презентация

1 4.5 Alluvial fans

2 Basin margin (fault) Feeder canyon Active depositional lobe Fan apex Fan toe Alluvial fans

3 An alluvial fan at the edge of a basin in a hot, arid climate

4 Scree and debris flow fan ~50 m radius (Spitsbergen) Fluvial fan ~50 km radius (Taklimakan Desert, China)

5 Types of alluvial fan Mixtures of these processes can occur on a single fan

6 Debris-flow dominated alluvial fans are small, steep and made up of overlapping lobes of poorly-sorted conglomerate

7 Debris flows

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11 Sedimentary logs through alluvial fan deposits Debris flow dominated fan. Matrix-supported, poorly sorted conglomerate beds, no sedimentary structures Sheetflood fan deposits. Horizontally stratified conglomerate and sandstone Stream channel fans. Channel-fill units of conglomerates and sandstones in fining- up successions (braided river deposits) metres - 10s metres

12 Sheetflood dominated alluvial fans are typically kilometres in radius and made up of sheets of moderately-sorted, clast-supported conglomerate

13 Sheetfloods

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15 Sedimentary logs through alluvial fan deposits Debris flow dominated fan. Matrix-supported, poorly sorted conglomerate beds, no sedimentary structures Sheetflood fan deposits. Horizontally stratified conglomerate and sandstone Stream channel fans. Channel-fill units of conglomerates and sandstones in fining- up successions (braided river deposits) metres - 10s metres

16 Stream dominated alluvial fans are kilometres to tens of kilometres in radius and made up of stream channel deposits and overbank sediments

17 Imbricated, clast supported Conglomerates and sandstones Stream channel deposits