Tenby Field Trip 5 9 May 2017 Area Map Geological Overview South - - PowerPoint PPT Presentation

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Tenby Field Trip 5 9 May 2017 Area Map Geological Overview South - - PowerPoint PPT Presentation

Feb 24, 2023 189 likes •1.77k views

Tenby Field Trip 5 9 May 2017 Area Map Geological Overview South Pembrokeshire Mainly sedimentary upper Palaeozoic rocks Devonian to Permian ESE WNW trending tracts Conformable and unconformable transitions from marine

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Tenby Field Trip

5 – 9 May 2017

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Area Map

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Geological Overview

  • South Pembrokeshire
  • Mainly sedimentary upper Palaeozoic rocks
  • Devonian to Permian
  • ESE – WNW trending tracts
  • Conformable and unconformable transitions from marine Silurian to

continental Devonian red sandstones

  • Sandstones, limestones, mudstones and coal measures
  • Rich variety of fossils
  • Older sedimentary and igneous strata exposed along

major fault lines and cores of anticlines

  • Precambrian to Silurian
  • Mainly in the North of the region
  • Oldest (643 MYA) is the Johnston Complex of metamorphosed

plutonic igneous rocks

  • Diorites; Granodiorites and granites
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Plate Tectonics Setting for Deformation of South Wales Rocks

  • Early Palaeozoic Deformations
  • Caledonian Orogeny
  • Avalonia docks with Laurentia closing the Iapetus Ocean (Late Silurian)
  • Acadian Orogeny
  • Closing of the Rheic Ocean (Mid Devonian)
  • Later Palaeozoic Deformations
  • Variscan Orogeny
  • Progressive convergence of Gondwana with Larussia (Upper

Carboniferous)

  • Eventual formation of Pangea supercontinent
  • South Wales lies in the ‘Forebold Edge’ of the thrust
  • Uplifting, folding, faulting and erosion over 50 – 100 MY
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SLIDE 5

From: Geology of South Wales, second edition - Gareth T. George

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Day 2 – 6 May 2017

  • Morning
  • Skrinkle Haven
  • Afternoon
  • Manorbier
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Skrinkle Haven

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Skrinkle Haven

  • Late Devonian to Early Carboniferous
  • Transitional contact visible between:
  • Pembroke Limestone Group
  • Lower Limestone Shales
  • Skrinkle Sandstone
  • Ridgeway Conglomerate
  • Freshwater West Formation
  • ‘Cavern Collapse’ Breccia
  • Visible along coast line
  • Fossiliferous
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The Geo eology of f Shrinkle Haven

From: Geology of South Wales, second edition - Gareth T. George

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Skrin inkle Haven

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Im Impressive Natural Arch in in th the Bla lack Rock Lim imestone Forming th the Horseback

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Coprolit ite

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Crin inoid Stems

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Chertified Lim imestone

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Humocky cr cross - Str tratifi fication

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Bry ryozoa

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Skri rinkle Carboniferous Fossil il Assemblage: Crinoids, , Fenestella Bry ryozoa, , Rugose Corals

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Mic ichelinia Tab abulate Co Coral

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Pala laeocasts

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Draught - Lydstep Penin insula la

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Th The Group at th the Lydstep Peninsula

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At Draught on Lydstep Peninsule – Showing Blo lowhole and Coll llapsed Breccia

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Manorbier

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Manorbier

  • Devonian
  • Freshwater West Formation
  • Old Red Sandstone (ORS)
  • Near Vertical Strata in Cliffs above high water mark
  • Fining up
  • Six cycles visible each capped with fine mudstones containing Calcretes
  • Interpreted as fills of ephemeral meandering fluvial channels
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Th The Geolo logy of Manorbie ier

From: Geology of South Wales, second edition - Gareth T. George

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Manorbie ier Bay

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Red Beds wit ith Many Trace Fossil ils

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ORS S - with ith Whit ite Ca Calc lcrete and Halo los Around th the Bu Burr rrows

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Beaconit ites Trace Fossil

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ORS - With White Calcrete an and Halo los Around th the Burrows

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Trace fossil - A Sin ingle Mil illipede in in Cross Sectio ion

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Mud Aggregate in in Mudstone

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Matu ture Soil il Profile le

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Beaconit ites Trace Fossil

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Dis ispla lacement on Fault lt

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Erosio ional Base of f Sandstone

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Buria ial l Chamber at t Kin ing's Quoit it

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Sit itting on th the Burial Chamber at t Kin ing's Quoit

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Tuff Band

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Townsend Tuff

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Tuff Band at t Rooks Cave

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Tuff Band at t Rooks Cave

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Possib ible le Faecal Pelle llets

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Day 3 – 7 May 2017

  • Morning
  • Freshwater West
  • Afternoon
  • West Angle Bay
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Freshwater West

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Freshwater West

  • Lower Limestone Shales
  • Upper ORS
  • Skrinkle Sandstone
  • Lower ORS
  • Ridgeway Conglomerate
  • Freshwater West Formation
  • Moor Cliffs Formation
  • Chapel Point Calcretes
  • Townsend Tuff Bed
  • Silurian Shales (Wenlock)
  • Ordovician Shales (Llanvirn)
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Freshwater West

From: Geology of South Wales, second edition - Gareth T. George

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Freshwater West

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Gareth Exp xplains Rock Types and Deposition Str tructures

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Using th the Str tream to Demonstrate Deposition Str tructures in in Flo lowing Water

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Standin ing Waves

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Alm lmost Anti ti-Dune

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Mudstone in in Silt ilt - Lower Ordovician - Lla lanvirn Ser eries

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Lava Bread Seaweed

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Freshwater East Formatio ion - Upper Silu ilurian

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Porphyry ry - From Outside of f This Area

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Red Beds of f th the Moor Cli liffs Formation

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Fault lt - Silu iluria ian / / Devonia ian Unconformit ity

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Fossili liferio ious Rock A

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Fossili liferio ious Rock B

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Chapel l Poin int Calc lcrete at t th the Fault lt

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Chapel l Poin int Calc lcrete - at t th the Fault lt

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Chapel l Poin int Calc lcrete

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Freshwater West Formation

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Rip ipple les at t Top of f Formation

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Fin inin ing up Sequence

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Trace Fossil of f Large Worm Tube

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Laminatio ions Approaching Beaconites Beds

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Orthocone - Long Shore Dri rift

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Beaconit ites Trace Fossil ils

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Beaconit ites Trace Fossils

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Green Sand

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Beaconites Trace Fossils in in Green Sand

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Mult lti Story Orig igin inal l Erosional l Surface

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Rid idgeway Conglomorate A

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Rid idgeway Conglomorate B

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West Angle Bay

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West Angle Bay

  • Formed by erosion of lower Carboniferous (Dinantian)

Limestone within the Angle Syncline

  • Main Rock Types
  • Blackrock Limestone
  • Avon Group (Limestone Shales)
  • Very Fossiliferous
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West Angle Bay

From: Geology of South Wales, second edition - Gareth T. George

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Lower Lim imestone Shales of f th the Avon Group

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Crin inoid Debris in in th the Sandy Lim imestone

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Slic lickensid ides Min inerali lised wit ith Calc lcit ite

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Zaphrentis is – A Rugose Coral

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Worm Burrow

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Approachin ing North Cove

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Sili ilicifie ied Worm Burrows

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Mappin ing th the Peric icli lines - North Cove

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Dynamite Cracks fr from Previous Quarrying - North Cove

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Sty tylo loli litic ic Contact in in North Cove

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Gla lacial l Ti Till ll - Dia iamic icton

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Gastropod

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Day 4 – 8 May 2017

  • Morning
  • Tenby South beach
  • Tenby North beach
  • Afternoon
  • Amroth
  • Ladies Cave
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Tenby South Beach

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Tenby South Beach

  • Rock Types
  • Bioclastic and Oolitic (Hunts Bay) Limestone
  • Crowded with Brachiopods
  • Caswell Bay Mudstone
  • Thinly bedded with Hunts Bay Limestone
  • Dipping steeply in cliffs
  • Blackrock Limestone
  • Dolomitised Bioclastic Limestone
  • High Tor Limestone
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Geology of Tenby

From: Geology of South Wales, second edition - Gareth T. George

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Slic lickensid ides on South Beach Clif liffs

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Small ll Cave at t th the Start of f South Beach

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Large Calc lcit ite Vein ins - South Beach

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Observing the Dip at the Start of the South Beach Cliffs

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Jell llyfish

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Pseudo-Breccia Formed Durin ing Dia iagenesis

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South Beach – Steps le leading to th the Atlantic Hotel

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Gig igantoproductus Gig iganteus

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Sip iphonodendron Martin ini i - Colonial Rugose Coral

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Corals

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The Group Progresses Along South Beach

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Syringapora Coral

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Examinin ing Another Pseudo-Breccia ia

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Lit ithostrotion Coral

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Unknown Coral

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Slic lickensid ides - South Beach Clif liffs

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Lit ithostrotion Coral l - Dis istance

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Lit ithostrotion Coral - Clo lose Up p - Was on a Reef

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Sip Siphonodendron Ju Junceum - Sp Spaghetti i Lik ike, , Co Colo lonia ial l Rugose Co Coral

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Rugose Coral

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Tenby North Beach

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Tenby North Beach

  • Complex Folding and Faulting during the Variscan Orogeny
  • Seen in cliff and low outcrops on the beach
  • Main Rock Types
  • Marros Group (Middle Carboniferous)
  • Sandstone, Mudstone & Siltstone
  • Pembroke Limestone Group (Lower Carboniferous)
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North Beach- Pla lan & Cross Section

From: Geology of South Wales, second edition - Gareth T. George

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Start of f North Beach fr from Tenby Harbour

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Gosker Rock fr from Tenby Harbour

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Conglomerate Horiz izon at t Fir irst Poin int

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Amroth

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Amroth

  • Rock Types
  • Upper Carboniferous (Westphalian Strata)
  • South Wales coal measures
  • Sandstone, Mudstone, Limestone & ORS
  • Heavily folded and faulted
  • Slumping
  • Fossiliferous
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Th The Geo eology Around th the Amroth Area

From: Geology of South Wales, second edition - Gareth T. George

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Amroth Notic ice Board

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Walk lkin ing Towards Amroth East

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St Stratig igraphy at t Amroth th East – Th The La Lady Froli lic Co Coal l Se Seam Above th the Bla Black Mudstones

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Clo loser Detail of f th the Str tratigraphy at Amroth East

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Th The Amroth Slu lump Sheet

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Th The Amroth Slu lump Sheet

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Rip ipple le Marks in in th the Slu lump Sheet

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Basal Lag Conglomerate fr from th the Tel elpyn Point Sandstone

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Cli limbing Rip ipple Cross Lamination

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Ir Iron Nodule les

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Non-Marine Bivalves (Mussels) in Amroth Freshwater Limestone - Possibly Anthracosia Regularis

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Pla lant Remain ins

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Non-Marine Bivalves (Mussels) in Amroth Freshwater Limestone

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Ladies Cave

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Ladies Cave

  • Classic Chevron Fold Anticline
  • Shale Beds
  • Softer Mudstone at fold hinge
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Cross Section Around Ladie ies Cave

From: Geology of South Wales, second edition - Gareth T. George

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Ladies Cave

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Ladie ies Cave

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Fossil Leaf at Ladies Cave

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Day 5 – 9 May 2017

Laugharne

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Laugharne

  • Succession of ORS Facies
  • Red Mudstones
  • Red Siltstones
  • Immature Calcretes
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Boat House

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Local Trouble Mak akers Examining th the Devonian ORS Cli liffs

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Graphic ic Log of Exposed Clif liffs Alo long th the Estu tuary

From: Geology of South Wales, second edition - Gareth T. George

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Calc lcretes

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Base ase of

  • f In

Intraformational Con

  • nglomerate Bed of
  • f Reworked

Calc alcrete Nodule les

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Lensoid idal Sandstone Str trin ingers

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Clim limbin ing Rip ipple les

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Beaconites Burrows in in Mudstone

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Cross Sectio ions of f Beaconites Burrows in in Sandstone

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Concoidal Fracture

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Small ll Dyke

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An Ic Ice Cream and Th Then Home

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The End