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Unformatted text preview: LECTURE 12 - GLACIOLACUSTRINE AND GLACIOMARINE SEDIMENTS GLACIOLACUSTRINE SEDIMENTS IN N.A. (SOFT CLAYS) • distribution and age most 18,000 to 6,000 ybp generally younger northward some still being deposited • sedimentology associated with proglacial lakes processes involve overflow, interflow, underflow • proximal facies underflow dominated sediment associations waterlaid tills flow tills subaqueous fan deposits deltaic deposits • distal facies combination of dispersal mechanisms sediment associations parallel multilaminated beds (rythmites) ball and pillow structures drop stones and disturbed laminae DELTAS • upper delta foresets underflow dominated system sed. transport by quasi-continuous currents grain flow and intermittent avalanches in places slump gen. surge currents may domin. sediments steeply dipping rhythm. bedded sand/gravel beds fining upwards sequences due to high disch. events distrib. channel shifts up to 1 m thick large clasts oriented paral. to dip some imbrication cross bedded sands rare/ clay absent •...
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- Spring '08
- Erosion, Sediment, parallel multilaminated beds, dispersal mechanics sediments, vert. aggr. rate