Department of Geology, University of New Brunswick, Box 4400, Fredericion, New Brunswick, E3B 5A3, Canada.
Liquefaction, fluidization and erosional structures associated with bituminous sands of the Bracklesham Formation (Middle Eocene) of Dorset, England
Article first published online: 14 JUN 2006
Volume 30, Issue 4, pages 525–535, August 1983
How to Cite
PLINT, A.G. (1983), Liquefaction, fluidization and erosional structures associated with bituminous sands of the Bracklesham Formation (Middle Eocene) of Dorset, England. Sedimentology, 30: 525–535. doi: 10.1111/j.1365-3091.1983.tb00690.x
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- Manuscript received 10 Sepiember 1982; revision received 21 January 1983
ABSTRACT At Hengistbury Head, Dorset, the Boscombe Sands (Middle Eocene, Bracklesham Formation) are of estuarine channel facies. A mud-filled channel is exposed, the banks and eastern flank of which have a black carbonaceous stain, the degraded remains of a bitumen. At the time of deposition, the bitumen rendered the sediment firm and it was extensively burrowed by a Thalassinoides-forming organism (crustacean). The bituminous sand on the eastern channel bank suffered brecciation and dilation as a result of liquefaction and flowage of the underlying sediments. This is thought to have been due to rapid expulsion of pore water, possibly as a result of seismic shock. The layers of bituminous sand below the surface were ruptured during water-escape, resulting in localized zones of rapid flow causing fluidization and the development of dewatering pipes up to 1.2 m long. The estuarine sediments were subsequently transgressed during which the bituminous sand was exposed on the seafloor, when it was eroded into a hummocky topography and heavily burrowed. Blocks of bituminous sand were reworked into the marine basal conglomerate, composed mainly of flints, demonstrating the remarkable strength of the bituminous cement.