Syneresis cracks: subaqueous shrinkage in argillaceous sediments caused by earthquake-induced dewatering
Pratt BR. 1998. Syneresis cracks: subaqueous shrinkage in argillaceous sediments caused by earthquake-induced dewatering. Sedimentary Geology. 117(1-2):1-10
Syneresis cracks, often confused with subaerial desiccation phenomena, are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay. This and other previously proposed mechanisms fail to account for their occurrence in low-energy, typically non-evaporitic facies, stratigraphically sporadic distribution, intrastratal formation under shallow burial depths, variation in morphology, degree of contraction, generation of sedimentary dikelets as crack fills, and deformation of dikelets and enclosing layers. Instead, it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater, interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures, and then these dikelets to be distorted. Comparative rarity of syneresis cracks in Phanerozoic versus Precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column, greater input of organic matter into the sediment, and the diversification of sediment-dwelling bacteria and meiofauna in Phanerozoic deposits.
- Type
- Journal Article
- Authors
- Pratt, Brian
- Units
- GLAC
- Keywords
- Geology, Geomorphology, Glacier National Park MT, Physical Sciences, seismites, syneresis