Deposits of a near-coastal fluvial plain — the toe head formation (upper devonian) of southwest cork, EIRE

Graham, John R.

doi:10.1016/0037-0738(75)90016-0

Cited by 15 publications

(9 citation statements)

References 15 publications

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“…The transition from coastal plain to marine conditions at the beginning of this episode is gradational. Regional drainage was directed along the basin axis from a coastal plain to the west (Naylor, 1975;Graham, 1975b) and also from the north west, north and north east (Fig. 20a).…”

Section: Episode 1: Transgression T1mentioning

confidence: 99%

Transgressive facies in the South Munster Basin, Ireland

MacCarthy

1987

Sedimentology

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This paper describes the sedimentation style associated with the basal Carboniferous transgression in southern Ireland and the influence which this event had on the palaeogeography of the region. The transgression as marked by the base of the Carboniferous succession is shown to represent one of several genetically related transgressive pulses which commenced during the Late Devonian. At this time an east‐west trending graben, the South Munster Basin, developed in southern Ireland. This was initially a non‐marine depositional site in which sediment was derived from the north and west. Subsidence and eustatic sea‐level rise resulted in a marine transgression which proceeded in a rhythmic style resulting in a number of transgressive‐stillstand pulses. The first transgressive pulse (T1) advanced in a westerly direction along the basin axis resulting in the development of an epicontinental‐like sea. The shoreline remained essentially static along the northern basin margin initially until a second transgressive pulse (T2) resulted in expansion of the marine area. The latter proceeded by gradual northward erosive advance of a barred coastal area as far as the northern basin margin where the stability of the bounding platform halted its progress. Erosion of the barrier shoreface was insufficient to destroy all the backbarrier lagoonal deposits which are preserved as a thin transgressive diachronous unit which grades northwards to a coastal alluvial plain. Immediately preceding the basal Carboniferous transgression (T3), a shallow, wave‐dominated, storm‐influenced shelf sea occupied the basinal area. Two sublittoral sand bar complexes developed on the shelf under the influence of shore‐parallel current regimes, apparently derived from source areas located on either side of the epicontinental sea The basal Carboniferous transgression took place in two pulses. The first (T3a) resulted in a rapid reduction in sand supply to the shelf and deposition of clay. The barrier shoreline responded by erosively retreating across the lagoon, leaving a transgressive lag in its wake. Its northwards advance was, however, limited due to the relative stability of the northern platform. Sand supply to the shelf was completely terminated in the second pulse (T3b) and the barrier rapidly migrated erosively across the northern platform for a considerable distance such that the coastal plain is overlain by a thin transgressive lag. This transgressive phase was immediately followed by shoreline stillstand and progressive shallowing of the shelf. An open sandy shelf developed on which offshore sand bars accumulated under a storm and wave dominated regime. Clay deposition continued in the deeper part of the basinal area but was eventually terminated as the shelf sands prograded centripetally into the basin. The main factor that controlled the style of the overall transgression was an interplay between eustatic sea level rise and basin subsidence. The rate of relative sea‐level rise together with the effect of differential subsidence and f...

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Section: Episode 1: Transgression T1mentioning

confidence: 99%

Transgressive facies in the South Munster Basin, Ireland

MacCarthy

1987

Sedimentology

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“…In general the lithofacies descriptions and age dating of equivalent rocks to the south of Kerry Head are not adequate enough to test this hypothesis. One exception may be Graham's (1975) Toe Head Formation In south-west Cork. This Formation is similar in lithofacies to the Kilmore Formation but is similar in age to the topmost Inshaboy Formation (-LL zone).…”

Section: Comparison With Adjacent Successionsmentioning

confidence: 99%

Quantitative interpretation of an evolving ancient river system

1983

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Multistorey sandstone bodies described from the Upper Devonian‐Lower Carboniferous of Kerry Head (Ireland) are interpreted as deposits of aggrading, perennial, river channels migrating laterally across alluvial plains. Point bars displayed surface features such as scroll bars, chute channels and chute bars. Relatively uncommon channel fills are both coarse‐ and fine‐grained. Quantitative interpretation of the sandstone bodies was accomplished by comparison with a physical model that predicts the sedimentology of single point bar deposits developed in channels of prescribed geometry and hydraulics. This analysis reveals that the separate storeys (point bars) in each sandstone body were deposited in a single channel belt in which channel geometry and hydraulics varied little with time (order of 103 yr) and space (order of 103 m). Two southerly flowing rivers of markedly different size were responsible for all sandstone bodies: bankfull widths, depths and mean velocities of both rivers varied little with time (order of 105 yr), implying a stable climatic setting. Channel sinuosities were usually 1.15–1.2 throughout the succession. Both rivers decreased in mean channel slope as time progressed, in association with a rising base‐level and a shoreline encroaching from the south. Using Bridge & Leeder's (1979) alluvial stratigraphy model, the nature and distribution of channel sandstone bodies relative to overbank deposits in the succession can be explained by an average (compacted) floodplain deposition rate of about 0.005 m yr−1, if avulsion occurred with a frequency of about once every 103 yr. Local variation in the relative amount of channel sandstone in the succession is probably due to local tectonic control of deposition.

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“…Previous studies have interpreted this association as having accumulated in a coastal plain which bordered the Late Devonian sea (Graham, 1975). A system of distributary channels (Facies 7) was flanked by relatively permanently flooded overbank areas (Facies 3c) which endured frequent sheet-flooding (Facies 4).…”

Section: Discussionmentioning

confidence: 95%

“…This led to a marine transgression into the basin from the east during the Famennian, which advanced in a westerly direction along the axis of the South Munster Basin (MacCarthy, 1987) and terminated Old Red Sandstone deposition in this area. Previous sedimentological studies ofthe non-marine basin fill have been mainly of a localized nature (Capewell, 1957(Capewell, , 1975Kuijpers, 1972;Graham & Reilly, 1972, 1976Graham, 1975;MacCarthy, Gardiner & Horne, 1978 ;Bridge, Van Veen & Matten, 1980;Penney, 1980;Ori & Penney, 1982;Bridge, 1983;Bridge & Diemer, 1983;Gardiner & Horne, 1983;Diemer, Bridge & Sanderson, 1987;Todd, 1989;Williams et al, 1989) though a few studies have formulated models for regional alluvial processes within the basin (Gardiner & MacCarthy, 1981;Graham, 1983). Of necessity, these are generalized due to the wide spread of the limited control points available at the time, allied with poor biostratigraphical control and the absence of a detailed lithostratigraphical framework.…”

Section: Introductionmentioning

confidence: 99%

Alluvial sedimentation patterns in the Munster Basin, Ireland

MacCarthy

1990

Sedimentology

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Post‐Caledonian southern Ireland witnessed the development of a NE‐SW orientated half‐graben known as the Munster Basin. More than 7 km of non‐marine sediments accumulated in the basin during the late Middle and Late Devonian. Marine conditions became established in the southern part of the basin at the end of the Devonian. In this paper, a model for the evolving style of sedimentation in the basin and its periphery is constructed with the aim of identifying the major factors which controlled sedimentation patterns and the architecture of the basin fill. The depositional history of the basin is considered in terms of four successive episodes. During Episode I, gravelly alluvial fans flanked upland areas around the northeastern and northern basin perimeter. These graded southwestwards to a floodplain dominated by sheet‐floods. In the western part of the basin, the first of three major fluvial influxes into the basin commenced. During Episode II, the first influx developed into a large sandy braided complex. The sediment was derived from a distant source area located to the north and west of the basin and was transported diagonally across the basin towards the southeast. Episode III witnessed a second influx which drained into the basin from the northeast and north. River channels were of low sinuosity and graded distally to an ephemeral playa lake. Episode IV was marked by a third fluvial influx from the west and northwest. This was confined to the southern half of the basin and drainage was directed towards the east. The fluvial distributaries were flanked by permanently flooded overbank areas. This influx coincided with the first marine transgression which advanced westwards. The end of Episode IV coincided with the beginning of the Carboniferous and was marked by a major marine transgression. Sediment input to the basin was influenced by stable areas occupied by granitic plutons on either side of the basin and a southward downthrowing fault along its northern margin. The drainage direction was principally controlled by E‐W trending within‐basin faults and an E‐W trending stable area located to the south. The basin was fundamentally of the axial transport type, the main drainage having been directed towards the east though there was also a strong lateral influx from the north, northwest and northeast. Stable areas around the, basin periphery resulted in either no sediment preservation or sequences of multistorey channel deposits while thick sequences dominated by fine‐grained floodplain or overbank deposits characterized areas of higher subsidence rate within the basin. Movement on the northern basin‐margin fault was probably the major cause of the first fluvial influx, while regional subsidence of the basin and its northern periphery resulted in the second influx. The third influx was a response to local subsidence in the southern part of the Munster Basin. This also contributed to the simultaneous westward marine transgression in this area towards the end of the Devonian. Source area denudation and re...

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Deposits of a near-coastal fluvial plain — the toe head formation (upper devonian) of southwest cork, EIRE

Cited by 15 publications

References 15 publications

Transgressive facies in the South Munster Basin, Ireland

Transgressive facies in the South Munster Basin, Ireland

Quantitative interpretation of an evolving ancient river system

Alluvial sedimentation patterns in the Munster Basin, Ireland

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