Petrology of the Shales-with-‘Beef’

Abstract

(A) Laminated Shales Shales, which are minutely laminated at the outcrop, but appear massive when traced inwards, have been described in Part I (p. 53). The change is accompanied by progressive bleaching towards the weathered surface, and by the deposition of minute, platy crystals of selenite between the laminæ. This bleaching suggests that the development of lamination has been accompanied by a loss of certain constituents of the shales, such as carbon (or hydrocarbons), and also (as indicated by the appearance of gypsum of iron-sulphide. Thus the weathering of the shales has produced a diminution of volume, and the resulting contraction, by separating the individual laminæ, has revealed the minute internal structure of the shales. It may be noted that similar development of lamination may be seen, for example, in the Rhætic Black Shales at Beacon Hill, Newark. In bed 71 e , consisting of well-stratified blue shale, Dr. Lang has found thin biconvex discs of a mineral determined by Mr. W. Campbell Smith as barytes. These discs are irregularly distributed along bedding-surfaces, from which they are readily detached, leaving behind a perfect impression of their shape and markings. The general appearance of these barytes discs can be gathered from fig. 3. The largest specimen examined had a mean diameter of 15 mm., a maximum thickness of 2 mm., and the specific gravity = 4·58. Both the upper and lower surfaces of the discs are marked by radial furrows, very distinct at the thin edge, but faint and often absent in

Combined sea-level and climate controls on limestone formation, hiatuses and ammonite preservation in the Blue Lias Formation, South Britain (uppermost Triassic – Lower Jurassic)

“…At the levels of limestone nodules, MS was measured in the limestone rather than light marl in cases where limestone constituted more than half of that stratigraphic level (Weedon et al 1999). As far as possible, calcite ‘beef’ veins and lenses (Richardson, 1923; Marshall, 1982), most prevalent at the base of laminated shale beds at Lyme Regis, were avoided during MS measurement.…”

“…The origin and significance of the limestone beds and nodules in the uppermost Rhaetian (Triassic) to Sinemurian (Jurassic) Blue Lias Formation of Britain has long been a subject of interest (Day, 1865; Richardson, 1923; Kent, 1936). Hallam (1960, 1964) argued that the limestones owed their characteristics to both diagenetic and primary (i.e.…”

Cone-In-Cone and Beef-In-Shale Textures from DSDP Site 330, Falkland Plateau, South Atlantic

“…Cone-in-cone structures were discussed by Richardson (1923) but have been reviewed by Tarr (1932) and more comprehensively by Woodland (1964). Both cone-in-cone and "beef-in-shale" are characterized by fibrous calcite.…”

Source rocks in foreland basins: A preferential context for the development of natural hydraulic fractures

“…Within the Liassic source rocks, calcite beef are common and have drawn attention for many years from geologists (e.g. Lang et al, 1923;Richardson, 1923;Buckland & De la Beche, 1835;Marshall, 1982), who at first attributed them to early diagenesis of the sediments. However, later work revealed epitaxial growth of calcite fibers (e.g.…”