Flow Regime Warm-Up

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Essay Question

A current is flowing with a mean velocity of 20 cm/sec, over a bed where the grain size is 1.0 mm and flow depths are 18-22 cm. Describe the bedform and stratification type for these conditions. Now, the current over the same bed increases gradually from 20 cm/sec to 200 cm/sec. Describe the succession of bedforms and stratification types which evolve throughout this increase. What would happen to bedforms and stratification type if, in the initial condition, water depth were decreased to 4 cm?

Multiple Choice Questions

Which of the following sedimentary structures will develop in a macro-tidal environment where sand is sand is dominant over mud?

lenticular bedding

symmetrical ripples with peaked crests

reactivation surfaces

hummocky cross stratification

flaser bedding

Paleocurrent analysis is a very important aspect of the regional study of sedimentary rocks. Which of the following features can be used to established ancient current directions?

plane-bed lamination

planar cross bedding with foresets tangential to bottomsets

trough cross bedding

flute casts

imbrication of pebbles in a conglomerate

ball-and-pillow structures