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A revised sedimentary and biostratigraphical architecture for the Type Llandovery area, Central Wales

(2013) GEOLOGICAL MAGAZINE. 150(2). p.300-332
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Abstract
The global standard for the Llandovery Series (early Silurian) in centralWales is re-assessed in the light of detailed geological surveying, biostratigraphical sampling and a rigorous examination of published datasets. A new sedimentary and biostratigraphical architecture is presented. Key graptolite, brachiopod, acritarch and, for the first time, chitinozoan assemblages are critically assessed. Upper Hirnantian to Aeronian strata record events that followed the Late Ordovician glacial maximum and comprise a series of progradational sequences bounded by flooding surfaces, but inferred still to be glacioeustatic in origin. Significant faunal renewals associated with many of the flooding levels underpin their potential for international recognition. Compound non-sequences are a feature of proximal parts of the system where erosion associated with fault footwall uplift was an important process. Extensive slump sheets contribute to further stratal loss and displacement in distal facies. A re-assessment of the Aeronian Stage GSSP reveals shortcomings with the biostratigraphical criteria used in its selection. Telychian portions of the succession display the disrupting effects of intra-Wenlock synsedimentary sliding; hence the relevance of key published fossil assemblages and the criteria used to erect the stage GSSP are undermined. However, the Llandovery area remains one of the best studied early Silurian successions in the world. This, together with regional considerations, supports the retention of the series standard in mid Wales where the contiguous deep-water basinal succession affords internationally cited exposure of richly graptolitic facies for the whole series and, significantly, for the post-sedgwickii Biozone interval.
Keywords
MID-WALES, WELSH BASIN, CONODONT COMMUNITY ANALYSIS, SILURIAN GRAPTOLITE BIOSTRATIGRAPHY, SEA-LEVEL CHANGES, microfossils, sequence stratigraphy, biostratigraphy, sedimentary architecture, Telychian, Llandovery, Aeronian, MARINE COMMUNITIES, ANTICOSTI ISLAND, RHEIDOL GORGE, WYE VALLEY, ORDOVICIAN

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Chicago
Davies, Jeremy R, Richard A Waters, Stewart G Molyneux, Mark Williams, Jan A Zalasiewicz, Thijs Vandenbroucke, and Jacques Verniers. 2013. “A Revised Sedimentary and Biostratigraphical Architecture for the Type Llandovery Area, Central Wales.” Geological Magazine 150 (2): 300–332.
APA
Davies, J. R., Waters, R. A., Molyneux, S. G., Williams, M., Zalasiewicz, J. A., Vandenbroucke, T., & Verniers, J. (2013). A revised sedimentary and biostratigraphical architecture for the Type Llandovery area, Central Wales. GEOLOGICAL MAGAZINE, 150(2), 300–332.
Vancouver
1.
Davies JR, Waters RA, Molyneux SG, Williams M, Zalasiewicz JA, Vandenbroucke T, et al. A revised sedimentary and biostratigraphical architecture for the Type Llandovery area, Central Wales. GEOLOGICAL MAGAZINE. 2013;150(2):300–32.
MLA
Davies, Jeremy R, Richard A Waters, Stewart G Molyneux, et al. “A Revised Sedimentary and Biostratigraphical Architecture for the Type Llandovery Area, Central Wales.” GEOLOGICAL MAGAZINE 150.2 (2013): 300–332. Print.
@article{3039226,
  abstract     = {The global standard for the Llandovery Series (early Silurian) in centralWales is re-assessed in the light of detailed geological surveying, biostratigraphical sampling and a rigorous examination of published datasets. A new sedimentary and biostratigraphical architecture is presented. Key graptolite, brachiopod, acritarch and, for the first time, chitinozoan assemblages are critically assessed. Upper Hirnantian to Aeronian strata record events that followed the Late Ordovician glacial maximum and comprise a series of progradational sequences bounded by flooding surfaces, but inferred still to be glacioeustatic in origin. Significant faunal renewals associated with many of the flooding levels underpin their potential for international recognition. Compound non-sequences are a feature of proximal parts of the system where erosion associated with fault footwall uplift was an important process. Extensive slump sheets contribute to further stratal loss and displacement in distal facies. A re-assessment of the Aeronian Stage GSSP reveals shortcomings with the biostratigraphical criteria used in its selection. Telychian portions of the succession display the disrupting effects of intra-Wenlock synsedimentary sliding; hence the relevance of key published fossil assemblages and the criteria used to erect the stage GSSP are undermined. However, the Llandovery area remains one of the best studied early Silurian successions in the world. This, together with regional considerations, supports the retention of the series standard in mid Wales where the contiguous deep-water basinal succession affords internationally cited exposure of richly graptolitic facies for the whole series and, significantly, for the post-sedgwickii Biozone interval.},
  author       = {Davies, Jeremy R and Waters, Richard A and Molyneux, Stewart G and Williams, Mark and Zalasiewicz, Jan A and Vandenbroucke, Thijs and Verniers, Jacques},
  issn         = {0016-7568},
  journal      = {GEOLOGICAL MAGAZINE},
  language     = {eng},
  number       = {2},
  pages        = {300--332},
  title        = {A revised sedimentary and biostratigraphical architecture for the Type Llandovery area, Central Wales},
  url          = {http://dx.doi.org/10.1017/S0016756812000337},
  volume       = {150},
  year         = {2013},
}

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