Negligible microbial matground influence on pre-vegetation river functioning: Evidence from the Ediacaran-Lower Cambrian Series Rouge, France

McMahon, William J.; Davies, Neil S.; Went, David J.

doi:10.1016/j.precamres.2017.01.020

Cited by 26 publications

(28 citation statements)

References 111 publications

(153 reference statements)

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“…They consist of red beds, succeeded by a transgressive sequence of marine sandstones, mudstones and Archaeocyatha bearing limestones (Doré, ; Brasier, ). The oldest red beds are probably best assigned a Fortunian age (Stage 1 Cambrian) but may, in part, be of slightly older, Ediacaran age (McMahon et al ., ). Deepening of the basin through the early Cambrian was associated with the transgression of an irregular shoreline from east to west (Doré, ).…”

Section: Geological Setting and Previous Workmentioning

confidence: 97%

“…Depending on their orientation relative to palaeocurrents obtained from trough cross‐strata these may be identified as marking downstream (DA – most common), oblique (downstream lateral accretion – DLA) or lateral accretion (LA) (Figs and ). These increments of accretion are interpreted as third‐order surfaces; they are fairly common, but not numerically dominant (McMahon et al ., ). Laterally extensive erosion surfaces defining sheet‐like bedsets of trough cross‐strata are most common and represent fourth‐order bounding surfaces.…”

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%

“…) and displays several more continuous bounding surfaces (fifth‐order) and some third‐order low angle, down current dipping surfaces truncated by erosion surfaces of fourth‐order. The low angle inclined surfaces are interpreted as the down‐current dipping accretion surfaces of mid channel bars ( iDA ), where ‘i’ refers to interpreted and ‘ DA ’, downstream accretion (see McMahon et al ., ).…”

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%

“…Exposure characteristics typically preclude the positive identification of the surface hierarchies seen in Facies Association 1. However, the similarity of facies supports a comparable channel‐bar origin (McMahon et al ., ).…”

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%

“…Each of the coastal localities provides a good opportunity for case study (e.g. Todd & Went, ; Went, , , ; Went & Andrews, ; Ielpi & Ghinassi, ; McMahon et al ., ). However, the true significance of certain facies or architectures may not be appreciated without consideration of the changes that are happening at basin or regional scale.…”

Section: Introductionmentioning

confidence: 97%

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Fluvial products and processes before the evolution of land plants: Evidence from the lower Cambrian Series Rouge, English Channel region

Went

McMahon

2018

Sedimentology

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Fluvial strata deposited before the advent of land plants are commonly sheet-like in geometry, lacking in channel forms. Although some pre-vegetation strata contrast strongly with fluvial strata from later eras, the characterization of pre-Devonian fluvial drainage systems remains incomplete. Field studies of the fluvial facies and architecture of the Series Rouge are presented to identify the products and processes of fluvial deposition occurring at high latitudes in the early Cambrian. Three different depositional styles or facies associations are recognized. Facies Association 1 is the most abundant (67%) comprising repetitively stacked sheets of trough cross-stratified sandstone interpreted to represent the preferential preservation of the deepest parts of low sinuosity, braided river channels, 4 to 6 m deep. Facies Association 2 is also common (30%) and displays more complex facies sequences that include stacked sheets of trough cross-strata, sets of large-scale tabular cross-strata, planar strata and subordinate mudstone. These facies are interpreted to reflect deposition in braided rivers with deeper channels, 6 to 8 m deep. These channels were more sinuous and subject to steady lateral migration which resulted in preservation of both deep and shallow parts of the river. Facies Association 3 is uncommon (3%) comprising interbedded sequences of cross-stratified sandstone and mudstone interpreted to reflect deposition on a muddy coastal plain in a mixture of braided and meandering channels, 1 to 3 m deep. The fluvial strata of the Series Rouge indicate that these pre-vegetation drainage systems were predominantly braided fluvial in origin. However, the style of braided fluvial deposition varied according to discharge and valley slope, the braided rivers becoming more migratory with decreasing slope. Meandering channel deposition was locally evident but was restricted to channels of low discharge crossing low gradient muddy coastal plains.

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Section: Geological Setting and Previous Workmentioning

confidence: 97%

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%

Section: Fluvial Deposits Of the Series Rougementioning

confidence: 97%