Sedimentary response to ignimbrite emplacement across a fluvial-shallow-marine transition: Ordovician Mweelrea Formation, South Mayo Trough, Western Ireland

Nancy R Riggs, Brian Mcconnell

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The Ordovician Mweelrea Formation is part of the basin fill of the South Mayo Trough in western Ireland and records progradation of alluvial facies northwestward across shallow- and marginal-marine Mweelrea 'passage beds' to marine Glenummera Formation facies. Early in Mweelrea Formation sedimentation, the first of a series of ignimbrites was emplaced, causing a disruption in this progradation. The preserved thickness of the ignimbrite is up to ca. 12m, and the sedimentary response varied depending on the environment that was affected. Eastern exposures of the Mweelrea Formation are coarse grained and represent fluvial facies. Emplacement of the ignimbrite caused overlying sediment to become richer in feldspar as well as coarser grained; heavy-mineral laminations are common here and in many supra-ignimbrite exposures, but the depositional style was unchanged. The ignimbrite overlies decreasing thickness of fluvial sandstone towards the west to where it directly overlies shoreline and shallow-marine passage beds. Here, sandstone that overlies the ignimbrite is fluvial, indicating that emplacement of the ignimbrite brought about an abrupt progradation. At the westernmost outcrops of Mweelrea Formation, the ignimbrite lies at the contact with the underlying marine Glenummera Formation. Marine sedimentation continued after emplacement of the ignimbrite, although a coarse conglomerate horizon immediately overlying the ignimbrite together with development of a delta suggests that sediment input was vastly increased.

Original languageEnglish (US)
JournalGeological Journal
DOIs
StateAccepted/In press - 2016

Fingerprint

ignimbrite
Ordovician
emplacement
trough
progradation
sandstone
sedimentation
basin fill
lamination
heavy mineral
sediment
conglomerate
feldspar
shoreline
outcrop

Keywords

  • Ignimbrite emplacement
  • Mweelrea Formation
  • Sedimentary response
  • South Mayo Trough

ASJC Scopus subject areas

  • Geology

Cite this

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title = "Sedimentary response to ignimbrite emplacement across a fluvial-shallow-marine transition: Ordovician Mweelrea Formation, South Mayo Trough, Western Ireland",
abstract = "The Ordovician Mweelrea Formation is part of the basin fill of the South Mayo Trough in western Ireland and records progradation of alluvial facies northwestward across shallow- and marginal-marine Mweelrea 'passage beds' to marine Glenummera Formation facies. Early in Mweelrea Formation sedimentation, the first of a series of ignimbrites was emplaced, causing a disruption in this progradation. The preserved thickness of the ignimbrite is up to ca. 12m, and the sedimentary response varied depending on the environment that was affected. Eastern exposures of the Mweelrea Formation are coarse grained and represent fluvial facies. Emplacement of the ignimbrite caused overlying sediment to become richer in feldspar as well as coarser grained; heavy-mineral laminations are common here and in many supra-ignimbrite exposures, but the depositional style was unchanged. The ignimbrite overlies decreasing thickness of fluvial sandstone towards the west to where it directly overlies shoreline and shallow-marine passage beds. Here, sandstone that overlies the ignimbrite is fluvial, indicating that emplacement of the ignimbrite brought about an abrupt progradation. At the westernmost outcrops of Mweelrea Formation, the ignimbrite lies at the contact with the underlying marine Glenummera Formation. Marine sedimentation continued after emplacement of the ignimbrite, although a coarse conglomerate horizon immediately overlying the ignimbrite together with development of a delta suggests that sediment input was vastly increased.",
keywords = "Ignimbrite emplacement, Mweelrea Formation, Sedimentary response, South Mayo Trough",
author = "Riggs, {Nancy R} and Brian Mcconnell",
year = "2016",
doi = "10.1002/gj.2822",
language = "English (US)",
journal = "Geological Journal",
issn = "0072-1050",
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T2 - Ordovician Mweelrea Formation, South Mayo Trough, Western Ireland

AU - Riggs, Nancy R

AU - Mcconnell, Brian

PY - 2016

Y1 - 2016

N2 - The Ordovician Mweelrea Formation is part of the basin fill of the South Mayo Trough in western Ireland and records progradation of alluvial facies northwestward across shallow- and marginal-marine Mweelrea 'passage beds' to marine Glenummera Formation facies. Early in Mweelrea Formation sedimentation, the first of a series of ignimbrites was emplaced, causing a disruption in this progradation. The preserved thickness of the ignimbrite is up to ca. 12m, and the sedimentary response varied depending on the environment that was affected. Eastern exposures of the Mweelrea Formation are coarse grained and represent fluvial facies. Emplacement of the ignimbrite caused overlying sediment to become richer in feldspar as well as coarser grained; heavy-mineral laminations are common here and in many supra-ignimbrite exposures, but the depositional style was unchanged. The ignimbrite overlies decreasing thickness of fluvial sandstone towards the west to where it directly overlies shoreline and shallow-marine passage beds. Here, sandstone that overlies the ignimbrite is fluvial, indicating that emplacement of the ignimbrite brought about an abrupt progradation. At the westernmost outcrops of Mweelrea Formation, the ignimbrite lies at the contact with the underlying marine Glenummera Formation. Marine sedimentation continued after emplacement of the ignimbrite, although a coarse conglomerate horizon immediately overlying the ignimbrite together with development of a delta suggests that sediment input was vastly increased.

AB - The Ordovician Mweelrea Formation is part of the basin fill of the South Mayo Trough in western Ireland and records progradation of alluvial facies northwestward across shallow- and marginal-marine Mweelrea 'passage beds' to marine Glenummera Formation facies. Early in Mweelrea Formation sedimentation, the first of a series of ignimbrites was emplaced, causing a disruption in this progradation. The preserved thickness of the ignimbrite is up to ca. 12m, and the sedimentary response varied depending on the environment that was affected. Eastern exposures of the Mweelrea Formation are coarse grained and represent fluvial facies. Emplacement of the ignimbrite caused overlying sediment to become richer in feldspar as well as coarser grained; heavy-mineral laminations are common here and in many supra-ignimbrite exposures, but the depositional style was unchanged. The ignimbrite overlies decreasing thickness of fluvial sandstone towards the west to where it directly overlies shoreline and shallow-marine passage beds. Here, sandstone that overlies the ignimbrite is fluvial, indicating that emplacement of the ignimbrite brought about an abrupt progradation. At the westernmost outcrops of Mweelrea Formation, the ignimbrite lies at the contact with the underlying marine Glenummera Formation. Marine sedimentation continued after emplacement of the ignimbrite, although a coarse conglomerate horizon immediately overlying the ignimbrite together with development of a delta suggests that sediment input was vastly increased.

KW - Ignimbrite emplacement

KW - Mweelrea Formation

KW - Sedimentary response

KW - South Mayo Trough

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