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Sand–mud couplets deposited by spontaneous remobilization of subaqueous transitional flows
Author(s) -
Koo Woong Mo,
Mohrig David,
Buttles James,
Sturmer Daniel,
Pontén Anna,
Hess Thomas
Publication year - 2020
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/sed.12625
Subject(s) - geology , turbidite , sedimentary depositional environment , debris flow , sediment , turbidity current , settling , geomorphology , deposition (geology) , compaction , hyperconcentrated flow , varve , moraine , geochemistry , geotechnical engineering , petrology , debris , sediment transport , structural basin , glacier , bed load , oceanography , environmental engineering , engineering
Clean basal and capping argillaceous sandstone couplets in deep water settings have been previously interpreted as the result of spatially segregated turbidity currents and debris flows or spatio‐temporal transitioning of a turbulent flow to a transitional/laminar state. However, this paper presents three‐dimensional laboratory experiments demonstrating that a single sediment‐gravity flow can develop sand–mud couplets by autogenic remobilization of sediments that are still in the process of being deposited. This remobilization appears common to flows composed of mixtures of sand and mud with viscosities and strengths measurably greater than water, but not so high as to fully suppress the settling of sand through the depositional current. Dewatering in the early sand deposit acts to lubricate the basal portion of the increasingly muddy upper division of the flow, causing it to accelerate downslope, triggering a secondary flow with a sediment composition distinct from the original mixture. Sediment deposition and remobilization processes in a single sediment‐gravity flow and their resultant deposit were imaged acoustically and cored at representative locations within the deposit. The acoustic data and cores show sand–mud couplets that are qualitatively similar to interpreted turbidite–debrite‐like couplets in natural systems.