The Black Marl of Black Ven and Stonebarrow, in the Lias of the Dorset Coast

Lang, W. D.; Spath, L. F.

doi:10.1144/gsl.jgs.1926.082.01-04.11

Cited by 46 publications

(11 citation statements)

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“…Ranging in depth from a few centimetres to 2 m below the hiatus surface are scattered concretions, the stellare nodules of earlier accounts (Lang & Spath, 1926; Fig. 4), which are similar in size and shape to the Type 1 concretions described above.…”

Section: Unexhumed Type 1 Concretions: the Stellare Nodulesmentioning

confidence: 57%

“…It has long been recognized as a layer of bored and encrusted early diagenetic concretions that is coincident with a biostratigraphic gap of three ammonite subzones (Fig. 2;Lang & Spath, 1926;Lang, 1945;Hallam, 1969;Sellwood, 1972;Cope et al, 1981). The lithological character of the Coinstone, formation and exhumation of the concretions, their colonization at the sea-floor and those characteristics that developed after reburial are described here.…”

Section: N a T U R E Of This Studymentioning

confidence: 99%

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Reworked early diagenetic concretions and the bioerosional origin of a regional discontinuity within British Jurassic marine mudstones

Hesselbo

Palmer

1992

Sedimentology

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The Coinstone is a well known hiatus‐concretion level in the Lower Lias (Lower Jurassic, Upper Sinemurian) of Dorset, southern England. It has long been recognized as a layer of bored and encrusted, early diagenetic, clay‐hosted septarian concretions coincident with a biostratigraphic gap of three ammonite subzones. Several different types of concretion of variable complexity can be distinguished, of which two, probably derived from slightly different stratigraphic levels, have been juxtaposed by condensation at the erosion surface. Diagenetic and biological processes occurring before, during and after exhumation on the Jurassic sea‐floor can be recognized. The relative timing of these events can be distinguished, suggesting that initial concretion consolidation, the first generation of septarian cracking, and the precipitation of the first generation of crack‐lining calcite preceded exhumation. These, therefore, probably took place at an early stage, at shallow burial depths within the accumulating sediment pile. The early calcite is brown, UV‐fluorescent and inclusion‐rich, and is similar to the first calcite generations seen in many other clay‐hosted septarian concretions. A generally early diagnetic origin of this material is thus inferred. Observations on crack textures and geometries and the interactions of the post‐exhumation fauna of encrusters, borers and burrowers lend support to previous suggestions that initial cracking in some septarian concretions took place in a stiff rather than a fully rigid concretion body, possibly given coherence by initial growth of some organic substance that was only later replaced by the calcite cements seen in most such concretions today. The burrowing activities of a benthic fauna in muds cause resuspension of sediment and facilitate erosion, even in the absence of high energy physical processes. Regional stratigraphic gaps may be formed as a consequence of sea level rises or falls, or as a response to sediment supply reduction independent of sea level change. Such major episodes of biologically mediated erosion in mudstone sequences may be of more general importance than has hitherto been recognized.

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Section: Unexhumed Type 1 Concretions: the Stellare Nodulesmentioning

confidence: 57%

Section: N a T U R E Of This Studymentioning

confidence: 99%

Reworked early diagenetic concretions and the bioerosional origin of a regional discontinuity within British Jurassic marine mudstones

Hesselbo

Palmer

1992

Sedimentology

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“…The Black Ven Mudstone is perhaps the most intensively sampled unit and is particularly rich in ammonites (Lang et al. 1923; Lang and Spath 1926; Simms 2004), as well as important fossils of marine reptiles (Martill 1995; McGowan and Milner 1999), the dinosaur Scelidosaurus (Martill et al. 2000) and insects (Zeuner 1962; Whalley 1985).…”

Section: Fossil Faunamentioning

confidence: 99%

“…The section also benefits from exceptionally detailed stratigraphic accounts, especially by Lang (1924, 1936; Lang et al. 1923, 1928; Lang and Spath 1926) and Buckman (1910, 1917, 1922), who devised high‐resolution bed‐by‐bed stratigraphical frameworks for the Lias (Simms 2004; Lord et al. 2010), which have provided the basis for modern lithostratigraphical interpretation.…”

mentioning

confidence: 99%

Completeness of the fossil record and the validity of sampling proxies at outcrop level

Dunhill

Benton

Twitchett³

et al. 2012

Palaeontology

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Most studies of the adequacy of the fossil record have been carried out at a global or continental scale, and they have used sampling proxies that generally do not incorporate all aspects of sampling (i.e. rock volume, accessibility, effort). Nonetheless, such studies have identified positive correlations between apparent diversity and various sampling proxies. The covariation of fossil and rock record signals has been interpreted as evidence for bias or for a common cause, such as sea level change, or as evidence that the signals are in some ways redundant with each other. Here, we compare a number of proxies representing the three main aspects of sampling, (1) sedimentary rock volume, (2) rock accessibility and (3) worker effort, with palaeodiversity in a geographically and stratigraphically constrained data set, the marine Lower Jurassic outcrop of the Dorset and East Devon Coast. We find that the proxies for rock volume and accessibility do not correlate well with the other sampling proxies, nor with apparent diversity, suggesting that the total amount of sedimentary rock preserved does not influence apparent diversity at a local scale, that is, the rock record at outcrop has been sampled efficiently. However, we do find some correlations between apparent diversity and proxies for worker effort. The fact that the proxies do not correlate significantly with each other suggests that none can be regarded as an all‐encompassing sampling proxy that covers all aspects of bias. Further, the presence of some correlations between sampling proxies and diversity most probably indicates the bonanza effect, as palaeontologists have preferentially sampled the richest rock units.

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“…Woodward (1893, p. 53) who diagrammatically depicted the Birchi Beds (beds 75 +76a of Lang's notation, 1923 and1926) dipping from a position high in West Cliff ('Devonshire Head' of Lang, Davies and others) to reach, and cross, the shore somewhere southwest of Lyme near to the Cobb (see Fig. Woodward (1893, p. 53) who diagrammatically depicted the Birchi Beds (beds 75 +76a of Lang's notation, 1923 and1926) dipping from a position high in West Cliff ('Devonshire Head' of Lang, Davies and others) to reach, and cross, the shore somewhere southwest of Lyme near to the Cobb (see Fig.…”

mentioning

confidence: 99%