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Contents of 5.7 How do we know how to interpret unseen turbidity currents?

5.7 How do we know how to interpret unseen turbidity currents?

• How is coarse sediment deposited in the deep sea?
• Before 1900, geologists observed and interpreted the layers and structures of sandstone and shale layers found in these ocean deposits.
• Graded beds implying settling (fine over coarse particles)
• Ripple-scale cross-bedding with a sharp, but not flat, base (evidence of pre-deposition scouring)
• This is interpreted as meaning the sediment did not just settle, but was also being swept along by a current that eroded the muddy seafloor before sand accumulation.
• Shale layers in between indicate times of slow accumulation.