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Sedimentary Environments and Facies
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
A middle fan consisting of a number of shallow, branching channels feeding a depositional lobe (the ‘suprafan’ of Normark 1978). Typical lithofacies: basal gravels and mud chips overlain by coarse to medium sandstones with interbedded fine-grained sandstone and mudstone. The sandstones deposited by turbidity currents are of uniform thickness for a long distance and exhibit a classical Bouma sequence.
Research progress and prospects of deep water episodically deposited mudstones
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Siqi Wang, Jianguo Zhang, Changsheng Li, Luyao Feng, Zaixing Jiang
So far, there are only a limited amount of reported works on the gravity flow-formed mudstones, which are generally described to be massive (Talling, Masson, and Sumner 2012), uniform (Tripsanas, Bryant, and Phaneuf 2004), homogeneous (Campos, Beck, and Crouzet 2013), and of variable single layer thicknesses (a few centimeters to several meters) (Talling, Masson, and Sumner 2012). Research on episodically deposited mudstones originates from that on the Bouma sequence. Specifically, the E section of the Bouma sequence is speculated to be composed of two parts, namely the massive mudstone deposited from the diluted turbidity (with volumetric mud content of 0.03% to 0.1%) in the base and the slowly deposited mudstone from the suspended particles at the top (Rupke 1975). Homogeneous massive structure is ascribed to the rapid depositional process in the turbidity flow, which results in the chaotic, rapid deposition of various suspended fine particles at the water body bottom (Stanley 1981). Funded by the Deep-Sea Drilling Program, massive mudstones were acquired in several boreholes of the Mediterranean deep-sea plain in the 1970s and 1980s, whose genesis was interpreted by the dilute turbidity deposition theory (Blanpied and Stanley 1981). Specifically, as flow hydrodynamics get weakened gradually, turbidity episodes can be classified according to thin silty sandstone layers within the massive mudstones. Generally, one turbidity episode is speculated to be recorded in the sequence bounded by silty sandstone layers in the bottom and massive mudstones at the top (Stow and Bowen 1980). Similar massive mudstones resulting from the dilute turbidity have been also reported in the Quaternary deep-sea sediments of the Gulf of Mexico (Behrens 1985). However, those thin silty sandstone layers are considered to be attributed to surges within one turbidity episode, and thus massive mudstones separated by these thin layers should be products of the same episode of turbidity (Tripsanas, Bryant, and Phaneuf 2004). Therefore, it is still controversial that whether thin silty sandstone layers are good indicators of turbidity episodes or only products of surges.