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The Bailey Hill Formation: Ludlow Series turbidites in the Welsh Borderland reinterpreted as distal storm deposits
Author(s) -
Tyler J. E.,
Woodcock N. H.
Publication year - 1987
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350220508
Subject(s) - geology , turbidite , paleontology , storm , palaeogeography , trough (economics) , sedimentary depositional environment , ordovician , geomorphology , oceanography , tectonics , structural basin , volcanism , macroeconomics , economics
The mainly Gorstian (Lower Ludlow, Silurian) Bailey Hill Formation, defined here, has previously been interpreted as a ‘bathyal’ turbidite sequence deposited in the north–south elongated Montgomery Trough. It has been seen as the Ludlow equivalent of the Wenlock and Llandovery turbidite systems preserved further west. Slowly deposited background sediments are punctuated by event deposits interpreted here not as turbidites but as distal storm deposits accumulated in an outer shelf setting. The model envisages entrainment of sediment above storm wave base on the inner shelf, lateral transport in the storm forced flow, and redeposition below storm wave base under the residual influence of this same flow. The distribution of the formation reflects the interplay between the palaeoslope of a broad shelf and palaeooceanographic factors such as storm wavebase, during a period of high sea level. Contemporaneous true turbidites to the northwest suggest that a depositional low existed outboard of the area of Bailey Hill Formation deposition at this time, in continuity with earlier Silurian turbidite systems. The revised palaeogeography is consistent with other aspects of Ludlow regional geology. By mid‐Ludlow time a tectonic modification of palaeogeography was underway, marked by extensive submarine slides.