Folding in intertidal sediments on the west Lancashire Coast, England

Abstract

Folded mud layers are observed to be spatially associated with dune bedforms in the runnels of a wide multi-barred foreshore. An hypothesis is presented linking the formation of the folds, by porewater and sediment movements, to the growth of the dune bedforms. The hypothesis is supported by published reports of laboratory experiments by other authors.

Storm surge turbation

“…Observation 7 indicates that sedimentation as well as deformation took place at the moment when surge transported sand masses came to rest. In this respect the observed structures differ from structures formed in experiments by Rettger (1935). The latter are entirely postdepositional in relation to the deformed laminae.…”

“…They can be distinguished from water escape structures (Johnson, 1977) inter aliu by (1) the continuity of laminae across the deformed intervals; (2) the penecontemporaneity of erosional features and contortion within the deformed beds; (3) the shared vergency of several structures that are not in contact with one another; and (4) the sporadic occurrence of isolated loading structures. They are distinguished from slumps (for instance Rettger, 1935;Gregory, 1969) inter aliu by the distribution of closely interrelated deformation, erosion, and sedimentation features through sequences of several laminae, and by the frequency of loading structures that may be isolated from one another by stretches of even lamination. The same characteristics set them apart from deformation in front of advancing dunes (McKee & Goldberg, 1969;Jones, 1972;Parker, 1973) and from fault-graded seismites (Seilacher, 1969).…”

“…They are distinguished from slumps (for instance Rettger, 1935;Gregory, 1969) inter aliu by the distribution of closely interrelated deformation, erosion, and sedimentation features through sequences of several laminae, and by the frequency of loading structures that may be isolated from one another by stretches of even lamination. The same characteristics set them apart from deformation in front of advancing dunes (McKee & Goldberg, 1969;Jones, 1972;Parker, 1973) and from fault-graded seismites (Seilacher, 1969). The combined properties of the sediment may provide help in diagnosing the environment.…”

Estuarine sedimentation in the Eocene of southern England

“…Load deformation structures are quite common in estuaries and on tidal flats, though few modern examples have been described (Macar, 1951 ;Pannekoek, 1960: Coleman, 1969Parker, 1973). The sand pillows at Virginia Water (Fig.…”

“…8) are circular to elliptical in plan and are symmetrical in vertical section and therefore distinct from intraformational folds (cf. Parker, 1973;McKee & Goldberg, 1969). Examples, mainly displayed on face 3 were exhumed, exposing the muddy elevations to erosion (Fig.…”