DOCSLIB.ORG

Testing the Relationship Between Marine Transgression and Evolving Island Palaeogeography Using 3D GIS: an Example from the Late Triassic of SW England

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Testing the Relationship Between Marine Transgression and Evolving Island Palaeogeography Using 3D GIS: an Example from the Late Triassic of SW England Downloaded from http://jgs.lyellcollection.org/ at University of Bristol Library on April 27, 2021 Research article Journal of the Geological Society https://doi.org/10.1144/jgs2020-158 | Vol. 178 | 2021 | jgs2020-158 Testing the relationship between marine transgression and evolving island palaeogeography using 3D GIS: an example from the Late Triassic of SW England Jack Lovegrove1, Andrew J. Newell2, David I. Whiteside1,3 and Michael J. Benton1* 1 School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK 2 British Geological Survey, Maclean Building, Crowmarsh Gifford, Wallingford OX10 8BB, UK 3 The Natural History Museum, Cromwell Road, London SW7 5BD, UK DIW, 0000-0003-1619-747X; MJB, 0000-0002-4323-1824 * Correspondence: [email protected] Abstract: The Rhaetian transgression marked a major change in landscape. The Permian and Triassic had been a time of terrestrial conditions across Europe, including much of mainland UK, as well as the North Sea and Irish Sea, represented by red bed clastic successions. Seas flooded across Europe at 205.7 Ma and the shift from terrestrial to marine environments is marked in the UK by the switch from the red beds of the Mercia Mudstone Group to the black mudstones and shelly limestones and sandstones of the Penarth Group. The area around Bristol was marked by a complex landscape in which an archipelago of islands of Carboniferous limestone was formed in the new shallow seas. The application of new methods in geographical information systems allows a detailed exploration of a number of conformable surfaces, the unconformity between the underlying Paleozoic rocks and the overlying Mesozoic strata, as well as levels within the latest Triassic sediments, marking the advance of the sea and interactions with the coeval tectonics, which caused some islands to rise and some basins to descend. The new geographical information system models show a sequence of palaeogeographical reconstructions of the archipelago and relate this to the island tetrapod faunas, which show strong evidence of the species–area effect. Supplementary material: Supplementary tables S1-S6 and 2D island map GIS files are available at https://doi.org/10.6084/ m9.figshare.c.5273256 Received 20 August 2020; revised 24 December 2020; accepted 16 January 2021 The transition from the Triassic to the Jurassic was a time of major slender crocodyliforms. The age of the fissures has been debated, global environmental change, with evidence for massive volcanism, with suggestions that they are either Carnian or Norian, and so accelerated rates of extinction, high-magnitude changes in sea-level predate the Rhaetian transgression (Robinson 1957), or Rhaetian and and extraterrestrial impacts. The overarching event was the break-up so more or less coeval with the transgression (Whiteside et al. 2016). of the Pangaean supercontinent and the onset of eruptions from the Key questions concern the impact of the Rhaetian transgression and Central Atlantic Magmatic Province, which drove a rapid fall and evolving palaeogeography on the fauna and flora. For example, it is subsequent rise in sea-level, resulting in a sustained marine understood from studies of modern organisms on islands that species transgression across much of western Europe, transforming Permo- numbers match island size, and that some groups may show dwarfing Triassic continental environments into epicontinental seas. The Late as a means of survival in small spaces. Moreover, the age and origin Triassic and Early Jurassic stratigraphy of SW Britain has played a of the palaeokarstic systems in which many of the fossils were globally significant part in unravelling the sequence of events around preserved have been the subject of much debate. this Rhaetian transgression and is the focus of this paper. Our aim here is to test whether we can use GIS methods to Although most previous work has focused on well-exposed produce a 3D model of a focused area in the British Isles, consisting outcrop sections, here we take a broader approach using of multiple stratigraphic marker horizons reconstructed as surfaces. geographical information system (GIS) models and 3D visualiza- We then explore how the tectonics preceding the Triassic, as well as tion. We analyse a large amount of published and unpublished data contemporary Earth movements through the Late Triassic and on stratigraphic thicknesses from boreholes, quarries, railway and Jurassic, affected the nature of the Carboniferous–Mesozoic road cuttings, and natural exposures across the Bristol–Bath– unconformity as well as basin-deepening and island-swamping by Mendips area in an attempt to gain new insights into the impact of the rising sea-levels of the latest Triassic. We explore whether these the Rhaetian transgression on the palaeogeography and palaeobio- new methods enable us to produce a more accurate map of the geography of SW England. archipelago (cf. the maps in Fig. 1), date the karst fissures on the A key aspect of the palaeogeography of this area is the Bristol– islands and estimate their sizes, and relate these geographical Severn palaeoarchipelago (Whiteside et al. 2016). This was an array features to contemporary island life. of structural highs in the Late Triassic and Early Jurassic, formed largely from Carboniferous limestone, the area and connectivity of which must have changed throughout the Rhaetian transgression Geological setting of the Bristol–Mendip Massif (Fig. 1). These palaeoislands are noted for their populations of small tetrapods, including some of the first dinosaurs and mammals, as Paleozoic basement well as lizard-like sphenodontians, gliding kuehneosaurids, broad- The study area is triangular and is bounded by the Bristol Channel to toothed procolophonids and trilophosaurids (Robinson 1957), and the west, the Mendip Hills to the south and the Cotswolds © 2021 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://jgs.lyellcollection.org/ at University of Bristol Library on April 27, 2021 2 Lovegrove et al. Fig. 1. Comparison between old and new maps of the Bristol archipelago. (a) Robinson (1957),(b) Whiteside et al. (2016),(c) Whiteside and Marshall (2008), and (d) our new map. Note that the map of Robinson (1957) represents Paleozoic rock outcrops and the fissure localities only because this author did not envisage a palaeoarchipelago at the time of sauropsid fissure filling. escarpment to the east (Fig. 2). In this area, the Jurassic and younger and Early to Late Triassic, when the adjacent Wessex Basin and rocks that make up the Cotswolds and regions to the east have been Worcester Graben formed major depocentres. Adjacent to the deeply eroded to reveal underlying folded and faulted Paleozoic steeply dipping fold limbs of Carboniferous limestone, the MMG is ‘basement’ rocks of Devonian and Carboniferous age. Older rocks represented by coarse scree and alluvial fan deposits of the are exposed in some areas, such as the Silurian sediments of the ‘Dolomitic Conglomerate’, now termed the MMG (marginal Tortworth inlier (Reed and Reynolds 1908). facies), which infills gullies developed on the flanks of the fold Areas of high elevation in the district are largely Carboniferous structures and dramatically highlights the exhumed Late Triassic limestone, except for the Devonian sandstones and Silurian igneous palaeotopography that is still present today. These parts of the rocks exposed in the core of the large periclines that make up the MMG are mainly assigned to the Branscombe Mudstone Formation. Mendip Hills (Fig. 2). These Paleozoic rocks were deformed by The upper part of the MMG, the Blue Anchor Formation (BAF), compression during the Variscan Orogeny in the Late overlies the Branscombe Mudstone Formation and is identified by a Carboniferous (Williams and Chapman 1986). The Carboniferous change from red beds to mudstones and fine-grained, green–grey limestones form a series of curved ridges that represent the often sandstones. The BAF contains marine trace fossils and bivalves and steeply dipping limbs of major fold structures, including the west– it records the initial Late Triassic marine transgression in SW Britain east-trending periclines of the Mendip Hills and the north–south- (Mayall 1981). Landon et al. (2017) recorded echinoid and trending Coalpit Heath Syncline between Bristol and Cromhall, ophiuroid echinoderms as well as cephalopod arm hooks in the which has a core of Carboniferous Coal Measures. BAF at Stoke Gifford, Bristol, confirming the marine conditions. The BAF is 20–40 m thick in the Central Somerset Basin, but thins – rapidly towards the Mendips and locally includes altered evaporite Stratigraphy of the Late Triassic Early Jurassic cover deposits (Green 1992). Traditionally, the Norian–Rhaetian bound- The Carboniferous and older basement rocks have a partial, ary was placed between the uppermost part of the BAF (the Williton unconformable cover of essentially flat-lying or gently dipping Member of Mayall (1981) is generally considered Rhaetian) and the Late Triassic and Early Jurassic strata of the Mercia Mudstone and Penarth Group, but uncertainties over palynological dating and Penarth groups, and the overlying Lias (Fig. 2). These units formed some local diachroneity mean that the Branscombe Mudstone prior to and during the Rhaetian transgression and show an Formation and BAF are dated as ‘Norian to
Load more

Recommended publications
  • A Building Stone Atlas of Warwickshire
    Strategic Stone Study A Building Stone Atlas of Warwickshire First published by English Heritage May 2011 Rebranded by Historic England December 2017 Introduction The landscape in the county is clearly dictated by the Cob was suitable for small houses but when more space was underlying geology which has also had a major influence on needed it became necessary to build a wooden frame and use the choice of building stones available for use in the past. The wattle fencing daubed with mud as the infilling or ‘nogging’ to geological map shows that much of this generally low-lying make the walls. In nearly all surviving examples the wooden county is underlain by the red mudstones of the Triassic Mercia frame was built on a low plinth wall of whatever stone was Mudstone Group. This surface cover is however, broken in the available locally. In many cases this is the only indication we Nuneaton-Coventry-Warwick area by a narrow strip of ancient have of the early use of local stones. Adding the stone wall rocks forming the Nuneaton inlier (Precambrian to early served to protect the wooden structure from rising damp. The Devonian) and the wider exposure of the unconformably infilling material has often been replaced later with more overlying beds of the Warwickshire Coalfield (Upper durable brickwork or stone. Sometimes, as fashion or necessity Carboniferous to early Permian). In the south and east of the dictated, the original timber framed walls were encased in county a series of low-lying ridges are developed marking the stone or brick cladding, especially at the front of the building outcrops of the Lower and Middle Jurassic limestone/ where it was presumably a feature to be admired.
    [Show full text]
  • Journey 400 Repaired.Indd
    A journey across 400 million yearsA journey 400 million years across The story of geology & landscape 610 570 510 440 410 360 290 245 210 145 65 0 Ediacaran Cambrian Ordovician Silurian Devonian Carboniferous Permian inTriassic SouthJurassic GloucestershireCretaceous Caenozoic Era 1 Palaeozoic Era Mesozoic Era Skull and front flipper of an Ichthyosaurus © Copyright South Gloucestershire Council (x0.2) � � All rights reserved LA100023410, 2007 � One of the early Jurassic marine reptiles � � ��������� known as ‘Sea Dragons’ (Bristol Museum) � �������� �������� � �� A journey 400 million years across � ��������� N � ��������� � �� � � ��������� �� �� � � � � � � � ������������ �������� �������� � � � ���� � � ������� � � � �� �� ����������� �� �� ���������� ������ ����� ����� ������� ����������� � � � � � ���� � Introduction ����� �������� � ��������� � ������� ��� � �������� � � ��������� ������� � ������� This booklet tells the story of Some sites, such as Aust Cliff, will �� ����� ������������ �� the geological history of South require an hour or two to explore �������� ���� � � � � ������� � ����� �������������� Gloucestershire, spanning some fully. Others – where the rocks � ����� � ������� � � ��������� 400 million years. are physically inaccessible or in a ����� � � dangerous location, like a working ������ � � �������� � �� � � It involves vast, almost unimaginable quarry – can only be viewed from a � � ������������ ������� �������� earth movements and dramatic, specific, safe vantage point. ����� radical changes in continents, ������
    [Show full text]
  • Macroevolutionary Patterns in Rhynchocephalia: Is the Tuatara (Sphenodon Punctatus) a Living Fossil? Palaeontology, 60(3), 319-328
    Herrera Flores, J., Stubbs, T., & Benton, M. (2017). Macroevolutionary patterns in Rhynchocephalia: is the tuatara (Sphenodon punctatus) a living fossil? Palaeontology, 60(3), 319-328. DOI: 10.1111/pala.12284 Publisher's PDF, also known as Version of record License (if available): CC BY Link to published version (if available): 10.1111/pala.12284 Link to publication record in Explore Bristol Research PDF-document University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms.html [Palaeontology, 2017, pp. 1–10] MACROEVOLUTIONARY PATTERNS IN RHYNCHOCEPHALIA: IS THE TUATARA (SPHENODON PUNCTATUS) A LIVING FOSSIL? by JORGEA.HERRERA-FLORES , THOMAS L. STUBBS and MICHAEL J. BENTON School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK; jorge.herrerafl[email protected], [email protected], [email protected] Typescript received 4 July 2016; accepted in revised form 19 January 2017 Abstract: The tuatara, Sphenodon punctatus, known from since the Triassic, rhynchocephalians had heterogeneous rates 32 small islands around New Zealand, has often been noted of morphological evolution and occupied wide mor- as a classic ‘living fossil’ because of its apparently close phospaces during the Triassic and Jurassic, and these then resemblance to its Mesozoic forebears and because of a long, declined in the Cretaceous. In particular, we demonstrate low-diversity history. This designation has been disputed that the extant tuatara underwent unusually slow lineage because of the wide diversity of Mesozoic forms and because evolution, and is morphologically conservative, being located of derived adaptations in living Sphenodon.
    [Show full text]
  • Aust Cliff and Manor Farm
    This excursion guide is a draft chapter, subject to revision, to be published in a field guide book whose reference is: Lavis, S. (Ed.) 2021. Geology of the Bristol District, Geologists’ Association Guide No. 75. It is not to be circulated or duplicated beyond the instructor and their class. Please send any corrections to Michael Benton at [email protected] Aust Cliff and Manor Farm Michael J. Benton Maps OS Landranger 172 1:50 000 Bristol & Bath Explorer 167 1:25 000 Thornbury, Dursley & Yate BGS Sheet 250 1:50 000 Chepstow Main references Swift & Martill (1999); Allard et al. (2015); Cross et al. (2018). Objectives The purpose of the excursion is to examine a classic section that documents the major environmental shift from terrestrial to marine rocks caused by the Rhaetian transgression, as well as the Triassic-Jurassic boundary, and to sample the rich fossil faunas, and espe- cially the Rhaetian bone beds. Risk analysis Low tides are essential for the excursion to Aust Cliff. Tides rise very rapidly along this section of coast (with a tidal range of about 12 m) and strong currents sweep past the bridge abutment. Visitors should begin the excursion on a falling tide. If caught on the east side of the bridge abutment when the tide rises, visitors should continue east along the coast to the end of the cliff where a path leads back to the motorway service area. In addition, the entire section is a high cliff, and rock falls are frequent, so hard hats must be worn. The Manor Farm section lies inland and is lower, so hard hats are less necessary.
    [Show full text]
  • Stratigraphy, Basins, Ireland, Triassic, Jurassic, Penarth Group, Lias Group
    [Type text] Raine et al. Uppermost Triassic and Lower Jurassic sediments, NI and ROI [Type text] 1 Uppermost Triassic to Lower Jurassic sediments of the island of Ireland and its surrounding basins. 2 3 RoBert Raine1, Philip Copestake2, Michael J. Simms3 and Ian Boomer4 4 5 1Geological Survey of Northern Ireland, Dundonald House, Upper Newtownards Road, Belfast, BT4 3SB, 6 Northern Ireland 7 2Merlin Energy Resources Ltd., Newberry House, New St, Herefordshire, HR8 2EJ, England, 8 3Ulster Museum, Belfast, BT9 5AB, Northern Ireland 9 4Geosciences Research Group, GEES, University of Birmingham, B15 2TT, England 10 11 Abstract 12 The uppermost Triassic to Lower Jurassic interval has not been extensively studied across the island 13 of Ireland. This paper seeks to redress that situation and presents a synthesis of records of the 14 uppermost Triassic and Lower Jurassic from both onshore and offshore basins as well as descriBing 15 the sedimentological characteristics of the main lithostratigraphical units encountered. Existing data 16 have been supplemented with a re-examination and logging of some outcrops and the integration of 17 data from recent hydrocarbon exploration wells and boreholes. The Late Triassic Penarth Group and 18 Early Jurassic Lias Group can Be recognised across the RepuBlic of Ireland and Northern Ireland. In 19 some onshore basins, almost 600 m of strata are recorded, however in offshore Basins thicknesses in 20 excess of two kilometres for the Lower Jurassic have now been recognised, although little detailed 21 information is currently availaBle. The transition from the Triassic to the Jurassic was a period of 22 marked gloBal sea-level rise and climatic change (warming) and this is reflected in the 23 lithostratigraphical record of these sediments in the basins of Northern Ireland and offshore Basins 24 of the Republic of Ireland.
    [Show full text]
  • The Quaternary Evolution of the Gordano Valley, North Somerset
    The Quaternary Evolution of the Gordano Valley, North Somerset, UK. Thomas Charles Bernard Hill A thesis submitted in partial fulfilment of the requirements of the University of the West of England, Bristol for the degree of Doctor of Philosophy. Faculty of the Built Environment, University of the West of England, Bristol January 2006 Abstract The Gordano Valley is a low-lying valley positioned in close proximity to the Severn Estuary, in southwest England. Although its late Quaternary and Holocene sedimentary archive is extensive, the spatial and temporal evolution of the Gordano Valley has received only limited attention from previous researchers. In this study, stratigraphic analysis of the valley archive, combined with pollen, diatom and particle size analysis are utilised in a detailed reconstruction of the evolution of the Gordano Valley. Two contrasting depositional environments are present, separated by a sedimentary ridge traversing the width of the valley. A tentative mechanism is presented for the development of the ridge in response to periglacial hillslope erosion and deposition during the Devensian glacial period (c. 115,000-11,500 Cal. yrs BP). In contrast, the chronology and development of the two depositional environments is clearer. Detailed multiproxy analysis of the two sedimentary archives reveals the development of an enclosed lake basin headward of the ridge during the late glacial period (c. 18,000-15,000 Cal. yrs BP). Subsequent climatic amelioration in response to the transition from glacial to interglacial conditions resulted in the terrestrialisation of the lake at the onset of the BØlling/AllerØd interstadial, c. 15,000 Cal. yrs BP. A complete hydroseral succession sequence is present in the headward region of the valley, where the terrestrialised lake sequence developed into the fen peatland that is present today.
    [Show full text]
  • Constraints on the Timescale of Animal Evolutionary History
    Palaeontologia Electronica palaeo-electronica.org Constraints on the timescale of animal evolutionary history Michael J. Benton, Philip C.J. Donoghue, Robert J. Asher, Matt Friedman, Thomas J. Near, and Jakob Vinther ABSTRACT Dating the tree of life is a core endeavor in evolutionary biology. Rates of evolution are fundamental to nearly every evolutionary model and process. Rates need dates. There is much debate on the most appropriate and reasonable ways in which to date the tree of life, and recent work has highlighted some confusions and complexities that can be avoided. Whether phylogenetic trees are dated after they have been estab- lished, or as part of the process of tree finding, practitioners need to know which cali- brations to use. We emphasize the importance of identifying crown (not stem) fossils, levels of confidence in their attribution to the crown, current chronostratigraphic preci- sion, the primacy of the host geological formation and asymmetric confidence intervals. Here we present calibrations for 88 key nodes across the phylogeny of animals, rang- ing from the root of Metazoa to the last common ancestor of Homo sapiens. Close attention to detail is constantly required: for example, the classic bird-mammal date (base of crown Amniota) has often been given as 310-315 Ma; the 2014 international time scale indicates a minimum age of 318 Ma. Michael J. Benton. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, U.K. [email protected] Philip C.J. Donoghue. School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, U.K. [email protected] Robert J.
    [Show full text]
  • BRSUG Number Mineral Name Hey Index Group Hey No
    BRSUG Number Mineral name Hey Index Group Hey No. Chem. Country Locality Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-37 Copper Au) 1.1 4[Cu] U.K., 17 Basset Mines, nr. Redruth, Cornwall Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-151 Copper Au) 1.1 4[Cu] U.K., 17 Phoenix mine, Cheese Wring, Cornwall Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-280 Copper Au) 1.1 4[Cu] U.K., 17 County Bridge Quarry, Cornwall Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and South Caradon Mine, 4 miles N of Liskeard, B-319 Copper Au) 1.1 4[Cu] U.K., 17 Cornwall Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-394 Copper Au) 1.1 4[Cu] U.K., 17 ? Cornwall? Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-395 Copper Au) 1.1 4[Cu] U.K., 17 Cornwall Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-539 Copper Au) 1.1 4[Cu] North America, U.S.A Houghton, Michigan Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-540 Copper Au) 1.1 4[Cu] North America, U.S.A Keweenaw Peninsula, Michigan, Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu, Ag and B-541 Copper Au) 1.1 4[Cu] North America, U.S.A Keweenaw Peninsula, Michigan, Elements and Alloys (including the arsenides, antimonides and bismuthides of Cu,
    [Show full text]
  • JNCC Coastal Directories Project Team
    Coasts and seas of the United Kingdom Region 11 The Western Approaches: Falmouth Bay to Kenfig edited by J.H. Barne, C.F. Robson, S.S. Kaznowska, J.P. Doody, N.C. Davidson & A.L. Buck Joint Nature Conservation Committee Monkstone House, City Road Peterborough PE1 1JY UK ©JNCC 1996 This volume has been produced by the Coastal Directories Project of the JNCC on behalf of the project Steering Group and supported by WWF-UK. JNCC Coastal Directories Project Team Project directors Dr J.P. Doody, Dr N.C. Davidson Project management and co-ordination J.H. Barne, C.F. Robson Editing and publication S.S. Kaznowska, J.C. Brooksbank, A.L. Buck Administration & editorial assistance C.A. Smith, R. Keddie, J. Plaza, S. Palasiuk, N.M. Stevenson The project receives guidance from a Steering Group which has more than 200 members. More detailed information and advice came from the members of the Core Steering Group, which is composed as follows: Dr J.M. Baxter Scottish Natural Heritage R.J. Bleakley Department of the Environment, Northern Ireland R. Bradley The Association of Sea Fisheries Committees of England and Wales Dr J.P. Doody Joint Nature Conservation Committee B. Empson Environment Agency Dr K. Hiscock Joint Nature Conservation Committee C. Gilbert Kent County Council & National Coasts and Estuaries Advisory Group Prof. S.J. Lockwood MAFF Directorate of Fisheries Research C.R. Macduff-Duncan Esso UK (on behalf of the UK Offshore Operators Association) Dr D.J. Murison Scottish Office Agriculture, Environment & Fisheries Department Dr H.J. Prosser Welsh Office Dr J.S.
    [Show full text]
  • Palaeolithic and Pleistocene Sites of the Mendip, Bath and Bristol Areas
    Proc. Univ. Bristol Spelacol. Soc, 19SlJ, 18(3), 367-389 PALAEOLITHIC AND PLEISTOCENE SITES OF THE MENDIP, BATH AND BRISTOL AREAS RECENT BIBLIOGRAPHY by R. W. MANSFIELD and D. T. DONOVAN Lists of references lo works on the Palaeolithic and Pleistocene of the area were published in these Proceedings in 1954 (vol. 7, no. 1) and 1964 (vol. 10, no. 2). In 1977 (vol. 14, no. 3) these were reprinted, being then out of print, by Hawkins and Tratman who added a list ai' about sixty papers which had come out between 1964 and 1977. The present contribution is an attempt to bring the earlier lists up to date. The 1954 list was intended to include all work before that date, but was very incomplete, as evidenced by the number of older works cited in the later lists, including the present one. In particular, newspaper reports had not been previously included, but are useful for sites such as the Milton Hill (near Wells) bone Fissure, as are a number of references in serials such as the annual reports of the British Association and of the Wells Natural History and Archaeological Society, which are also now noted for the first time. The largest number of new references has been generated by Gough's Cave, Cheddar, which has produced important new material as well as new studies of finds from the older excavations. The original lists covered an area from what is now the northern limit of the County of Avon lo the southern slopes of the Mendips. Hawkins and Tratman extended that area to include the Quaternary Burtle Beds which lie in the Somerset Levels to the south of the Mendips, and these are also included in the present list.
    [Show full text]
  • Severn Estuary RCZAS Updated Project Design for Phase 2 Main
    Severn Estuary Rapid Coastal Zone Assessment Survey Updated Project Design for Phase 2 Main Fieldwork for English Heritage (HEEP Project No. 3885) Toby Catchpole and Adrian M. Chadwick Version 2 Revised, March 2010 Contents List of figures ............................................................................................................ iii Project details ............................................................................................................ v Summary ................................................................................................................. vii 1 Introduction and project background..................................................................1 2 Research aims and objectives ...........................................................................3 3 Summary of Phases 1 and 2a ...........................................................................5 3.1 Introduction .........................................................................................5 3.2 Sites identified as requiring further study in Phase 2a ......................... 5 3.3 The results of the Phase 2a fieldwork ................................................. 6 4 Project interfaces ...............................................................................................9 5 Communications and project products ............................................................. 11 6 Project review ..................................................................................................13 7 Health
    [Show full text]
  • Somerset Geology-A Good Rock Guide
    SOMERSET GEOLOGY-A GOOD ROCK GUIDE Hugh Prudden The great unconformity figured by De la Beche WELCOME TO SOMERSET Welcome to green fields, wild flower meadows, farm cider, Cheddar cheese, picturesque villages, wild moorland, peat moors, a spectacular coastline, quiet country lanes…… To which we can add a wealth of geological features. The gorge and caves at Cheddar are well-known. Further east near Frome there are Silurian volcanics, Carboniferous Limestone outcrops, Variscan thrust tectonics, Permo-Triassic conglomerates, sediment-filled fissures, a classic unconformity, Jurassic clays and limestones, Cretaceous Greensand and Chalk topped with Tertiary remnants including sarsen stones-a veritable geological park! Elsewhere in Mendip are reminders of coal and lead mining both in the field and museums. Today the Mendips are a major source of aggregates. The Mesozoic formations curve in an arc through southwest and southeast Somerset creating vales and escarpments that define the landscape and clearly have influenced the patterns of soils, land use and settlement as at Porlock. The church building stones mark the outcrops. Wilder country can be found in the Quantocks, Brendon Hills and Exmoor which are underlain by rocks of Devonian age and within which lie sunken blocks (half-grabens) containing Permo-Triassic sediments. The coastline contains exposures of Devonian sediments and tectonics west of Minehead adjoining the classic exposures of Mesozoic sediments and structural features which extend eastward to the Parrett estuary. The predominance of wave energy from the west and the large tidal range of the Bristol Channel has resulted in rapid cliff erosion and longshore drift to the east where there is a full suite of accretionary landforms: sandy beaches, storm ridges, salt marsh, and sand dunes popular with summer visitors.
    [Show full text]