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class="vector-toc-numb">2</span> <span>Stratigraphy</span> </div> </a> <button aria-controls="toc-Stratigraphy-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Stratigraphy subsection</span> </button> <ul id="toc-Stratigraphy-sublist" class="vector-toc-list"> <li id="toc-Blue_Anchor_Formation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Blue_Anchor_Formation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Blue Anchor Formation</span> </div> </a> <ul id="toc-Blue_Anchor_Formation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Branscombe_Mudstone_Formation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Branscombe_Mudstone_Formation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Branscombe Mudstone Formation</span> </div> 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class="vector-toc-numb">2.4.1</span> <span>Wilkesley Halite member</span> </div> </a> <ul id="toc-Wilkesley_Halite_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Wych_Mudstone_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Wych_Mudstone_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.2</span> <span>Wych Mudstone member</span> </div> </a> <ul id="toc-Wych_Mudstone_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Byley_Mudstone_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Byley_Mudstone_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.3</span> <span>Byley Mudstone member</span> </div> </a> <ul id="toc-Byley_Mudstone_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Northwich_Halite_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Northwich_Halite_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.4</span> <span>Northwich Halite member</span> </div> </a> <ul id="toc-Northwich_Halite_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bollin_Mudstone_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Bollin_Mudstone_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.5</span> <span>Bollin Mudstone member</span> </div> </a> <ul id="toc-Bollin_Mudstone_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Singleton_Mudstone_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Singleton_Mudstone_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.6</span> <span>Singleton Mudstone member</span> </div> </a> <ul id="toc-Singleton_Mudstone_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Kirkham_Mudstone_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Kirkham_Mudstone_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.7</span> <span>Kirkham Mudstone member</span> </div> </a> <ul id="toc-Kirkham_Mudstone_member-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Preesall_Halite_member" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Preesall_Halite_member"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4.8</span> <span>Preesall Halite member</span> </div> </a> <ul id="toc-Preesall_Halite_member-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Tarporley_Siltstone_Formation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Tarporley_Siltstone_Formation"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.5</span> <span>Tarporley Siltstone Formation</span> </div> </a> <ul id="toc-Tarporley_Siltstone_Formation-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" 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.latitude{white-space:nowrap}</style><span class="plainlinks nourlexpansion"><a class="external text" href="https://geohack.toolforge.org/geohack.php?pagename=Mercia_Mudstone_Group&params=52.3052_N_1.6965_W_region:GB-ENG"><span class="geo-default"><span class="geo-dms" title="Maps, aerial photos, and other data for this location"><span class="latitude">52°18′19″N</span> <span class="longitude">1°41′47″W</span></span></span><span class="geo-multi-punct"> / </span><span class="geo-nondefault"><span class="geo-dec" title="Maps, aerial photos, and other data for this location">52.3052°N 1.6965°W</span><span style="display:none"> / <span class="geo">52.3052; -1.6965</span></span></span></a></span></span></div></div> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Group of Triassic rocks in the United Kingdom</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox vcard" style="width:24.5em;"><tbody><tr><th colspan="2" class="infobox-above fn org" style="border-style:solid; border-width: 2px 33px; border-color:rgb(227,185,219)">Mercia Mudstone Group</th></tr><tr><td colspan="2" class="infobox-subheader"><a href="/wiki/Geochronology" title="Geochronology">Stratigraphic range</a>: <a href="/wiki/Early_Triassic" title="Early Triassic">Early Triassic</a>-<a href="/wiki/Rhaetian" title="Rhaetian">Rhaetian</a></td></tr><tr><th scope="row" class="infobox-label">Type</th><td class="infobox-data"><a href="/wiki/Group_(stratigraphy)" title="Group (stratigraphy)">Group</a></td></tr><tr><th scope="row" class="infobox-label">Unit of</th><td class="infobox-data"><a href="/wiki/New_Red_Sandstone" title="New Red Sandstone">New Red Sandstone Supergroup</a></td></tr><tr><th scope="row" class="infobox-label">Sub-units</th><td class="infobox-data"><a href="#Stratigraphy">Stratigraphy</a></td></tr><tr><th scope="row" class="infobox-label">Underlies</th><td class="infobox-data"><a href="/wiki/Penarth_Group" title="Penarth Group">Penarth Group</a></td></tr><tr><th scope="row" class="infobox-label">Overlies</th><td class="infobox-data"><a href="/wiki/Sherwood_Sandstone_Group" title="Sherwood Sandstone Group">Sherwood Sandstone Group</a></td></tr><tr><th scope="row" class="infobox-label">Thickness</th><td class="infobox-data">over 1,350 m (4,430 ft)</td></tr><tr><th colspan="2" class="infobox-header" style="border-style:solid; border-width: 2px 33px; border-color:rgb(227,185,219)">Lithology</th></tr><tr><th scope="row" class="infobox-label">Primary</th><td class="infobox-data"><a href="/wiki/Mudstone" title="Mudstone">Mudstone</a></td></tr><tr><th scope="row" class="infobox-label">Other</th><td class="infobox-data"><a href="/wiki/Siltstone" title="Siltstone">Siltstone</a>, <a href="/wiki/Sandstone" title="Sandstone">sandstone</a>, <a href="/wiki/Halite" title="Halite">halite</a>, <a href="/wiki/Anhydrite" title="Anhydrite">anhydrite</a></td></tr><tr><th colspan="2" class="infobox-header" style="border-style:solid; border-width: 2px 33px; border-color:rgb(227,185,219)">Location</th></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Geographic_coordinate_system" title="Geographic coordinate system">Coordinates</a></th><td class="infobox-data"><span class="geo-inline"><style data-mw-deduplicate="TemplateStyles:r1156832818">.mw-parser-output .geo-default,.mw-parser-output .geo-dms,.mw-parser-output .geo-dec{display:inline}.mw-parser-output .geo-nondefault,.mw-parser-output .geo-multi-punct,.mw-parser-output .geo-inline-hidden{display:none}.mw-parser-output .longitude,.mw-parser-output .latitude{white-space:nowrap}</style><span class="plainlinks nourlexpansion"><a class="external text" href="https://geohack.toolforge.org/geohack.php?pagename=Mercia_Mudstone_Group&params=52.3052_N_1.6965_W_region:GB-ENG"><span class="geo-default"><span class="geo-dms" title="Maps, aerial photos, and other data for this location"><span class="latitude">52°18′19″N</span> <span class="longitude">1°41′47″W</span></span></span><span class="geo-multi-punct"> / </span><span class="geo-nondefault"><span class="geo-dec" title="Maps, aerial photos, and other data for this location">52.3052°N 1.6965°W</span><span style="display:none"> / <span class="geo">52.3052; -1.6965</span></span></span></a></span></span></td></tr><tr><th scope="row" class="infobox-label">Region</th><td class="infobox-data"><a href="/wiki/Scotland" title="Scotland">Scotland</a>, <a href="/wiki/England" title="England">England</a>, <a href="/wiki/Wales" title="Wales">Wales</a></td></tr><tr><th scope="row" class="infobox-label">Country</th><td class="infobox-data"><a href="/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a></td></tr><tr><th colspan="2" class="infobox-header" style="border-style:solid; border-width: 2px 33px; border-color:rgb(227,185,219)">Type section</th></tr><tr><th scope="row" class="infobox-label">Named for</th><td class="infobox-data"><a href="/wiki/Mercia" title="Mercia">Mercia</a></td></tr><tr><td colspan="2" class="infobox-below" style="border-style:solid; border-width: 2px; border-color:rgb(227,185,219)"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Geologic_map_Wales_%26_SW_England_EN.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Geologic_map_Wales_%26_SW_England_EN.svg/240px-Geologic_map_Wales_%26_SW_England_EN.svg.png" decoding="async" width="240" height="210" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Geologic_map_Wales_%26_SW_England_EN.svg/360px-Geologic_map_Wales_%26_SW_England_EN.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/48/Geologic_map_Wales_%26_SW_England_EN.svg/480px-Geologic_map_Wales_%26_SW_England_EN.svg.png 2x" data-file-width="2220" data-file-height="1940" /></a></span><br />Map of Mercia Mudstone Group's outcrop (Triassic) in Wales and southwest England</td></tr></tbody></table> <p>The <b>Mercia Mudstone Group</b> is an early <a href="/wiki/Triassic" title="Triassic">Triassic</a> <a href="/wiki/Lithostratigraphy" title="Lithostratigraphy">lithostratigraphic</a> <a href="/wiki/Group_(stratigraphy)" title="Group (stratigraphy)">group</a> (a sequence of <a href="/wiki/Rock_strata" class="mw-redirect" title="Rock strata">rock strata</a>) which is widespread in Britain, especially in the <a href="/wiki/English_Midlands" class="mw-redirect" title="English Midlands">English Midlands</a>—the name is derived from the ancient kingdom of <a href="/wiki/Mercia" title="Mercia">Mercia</a> which corresponds to that area. It is frequently encountered in older literature as the <b><a href="/wiki/Keuper_Marl" class="mw-redirect" title="Keuper Marl">Keuper Marl</a></b> or <b>Keuper Marl Series</b>.<sup id="cite_ref-BgsLexicon_1-0" class="reference"><a href="#cite_note-BgsLexicon-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>The Mercia Mudstone Group is now divided into five formations recognised and mappable across its entire <a href="/wiki/Outcrop" title="Outcrop">outcrop</a> and <a href="/wiki/Subcrop" title="Subcrop">subcrop</a>. The formations are a mix of <a href="/wiki/Mudstone" title="Mudstone">mudstones</a>, <a href="/wiki/Siltstone" title="Siltstone">siltstones</a>, <a href="/wiki/Sandstone" title="Sandstone">sandstones</a> and <a href="/wiki/Halite" title="Halite">halites</a>. Historically this sequence of rocks has been subdivided in different ways with different names in each of the <a href="/wiki/Basinal_areas" class="mw-redirect" title="Basinal areas">basinal areas</a> in which it is found. Increasing knowledge of the sequences and the more recent development of seamless electronic mapping by the <a href="/wiki/British_Geological_Survey" title="British Geological Survey">British Geological Survey</a> (BGS) necessitated a reappraisal of these divisions. A report published by BGS in 2008 recommended the abandonment of previous divisions and naming schemes in favour of a simpler approach which, having now been adopted, is set out below.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <ul><li><b>Blue Anchor Formation</b></li> <li><b>Branscombe Mudstone Formation</b></li> <li><b>Arden Sandstone Formation</b></li> <li><b>Sidmouth Mudstone Formation</b></li> <li><b>Tarporley Siltstone Formation</b></li></ul> <p>Older schemes will remain in maps and literature well into the future,<sup id="cite_ref-FW_3-0" class="reference"><a href="#cite_note-FW-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> providing a source of potential confusion. An example might be the Arden Sandstone Formation which previously enjoyed lower status as a <a href="/wiki/Member_(geology)" class="mw-redirect" title="Member (geology)">member</a> and also higher status as a <a href="/wiki/Group_(stratigraphy)" title="Group (stratigraphy)">group</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Distribution">Distribution</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=1" title="Edit section: Distribution"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The group crops out widely across England, representing deposition within numerous Triassic basins, some of which are physically connected at depth. From the south there is an almost continuous outcrop from the <a href="/wiki/Wessex_Basin" title="Wessex Basin">Wessex Basin</a> of east <a href="/wiki/Devon" title="Devon">Devon</a>, <a href="/wiki/Somerset" title="Somerset">Somerset</a> and <a href="/wiki/Dorset" title="Dorset">Dorset</a>, through the <a href="/wiki/Bristol" title="Bristol">Bristol</a>/<a href="/wiki/South_Wales" title="South Wales">South Wales</a> area and the <a href="/wiki/Worcester_Basin" title="Worcester Basin">Worcester</a> and Knowle Basins into the English Midlands and including the Needwood Basin of <a href="/wiki/Staffordshire" title="Staffordshire">Staffordshire</a>. Northwards the outcrop splits either side of the <a href="/wiki/Pennines" title="Pennines">Pennines</a> where deposition took place across the East Midlands Shelf of <a href="/wiki/Nottinghamshire" title="Nottinghamshire">Nottinghamshire</a> and through <a href="/wiki/Yorkshire" title="Yorkshire">Yorkshire</a> to the North Sea coast at <a href="/wiki/Hartlepool" title="Hartlepool">Hartlepool</a>. A western arm includes the <a href="/wiki/Stafford_Basin" title="Stafford Basin">Stafford</a> and <a href="/wiki/Cheshire_Basin" title="Cheshire Basin">Cheshire</a> basins, West <a href="/wiki/Lancashire" title="Lancashire">Lancashire</a> and the Carlisle Basin—the latter are connected at depth beneath the <a href="/wiki/Irish_Sea" title="Irish Sea">Irish Sea</a>.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The group is most thickly developed within the <a href="/wiki/Cheshire_Basin" title="Cheshire Basin">Cheshire Basin</a> (which also extends southwards into north Shropshire) where it attains a thickness in excess of 1,350 m. </p> <div class="mw-heading mw-heading2"><h2 id="Stratigraphy">Stratigraphy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=2" title="Edit section: Stratigraphy"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Blue_Anchor_Formation">Blue Anchor Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=3" title="Edit section: Blue Anchor Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Blue_Anchor_Formation_rock.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/Blue_Anchor_Formation_rock.png/150px-Blue_Anchor_Formation_rock.png" decoding="async" width="150" height="170" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/67/Blue_Anchor_Formation_rock.png/225px-Blue_Anchor_Formation_rock.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/67/Blue_Anchor_Formation_rock.png/300px-Blue_Anchor_Formation_rock.png 2x" data-file-width="448" data-file-height="508" /></a><figcaption>A <a href="/wiki/Reptile" title="Reptile">reptile</a> tooth and a <a href="/wiki/Fish" title="Fish">fish</a> tooth from the Blue Anchor Formation, <a href="/wiki/Somerset" title="Somerset">Somerset</a></figcaption></figure> <p>The formation is named from the village of <a href="/wiki/Blue_Anchor" title="Blue Anchor">Blue Anchor</a> on the coast of west Somerset. It consists largely of green to grey mudstones and siltstones (which gave rise to the earlier name of this sequence, the Tea-green Marls) and varies from around 5 m to 67 m in thickness. Though common to all other areas, the Blue Anchor Formation is absent through erosion in the Stafford Basin and in Lancashire. It is of late Norian to early Rhaetian age. It is overlain by the Westbury Formation of the <a href="/wiki/Penarth_Group" title="Penarth Group">Penarth Group</a> which represents widespread inundation of the Triassic basins as global sea levels rose. </p> <div class="mw-heading mw-heading3"><h3 id="Branscombe_Mudstone_Formation">Branscombe Mudstone Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=4" title="Edit section: Branscombe Mudstone Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The formation consists of red-brown mudstones and siltstones in which <a href="/wiki/Gypsum" title="Gypsum">gypsum</a>/<a href="/wiki/Anhydrite" title="Anhydrite">anhydrite</a> occurs as beds, veins and nodules. It was formerly known as the 'Brooks Mill Mudstone Formation' in the Cheshire Basin (and named from a location near <a href="/wiki/Nantwich" title="Nantwich">Nantwich</a>), as the 'Cropwell Bishop Formation' on the 'East Midlands Shelf' and as the 'Twyning Mudstone Formation' in the Worcester and Knowle basins. It is equivalent to the 'Triton Formation' of the southern <a href="/wiki/North_Sea" title="North Sea">North Sea</a>. The Branscombe Mudstone Formation, which is named from <a href="/wiki/Branscombe" title="Branscombe">Branscombe</a> on the east Devon coast, is of <a href="/wiki/Norian" title="Norian">Norian</a> age, i.e. 216–204 mya. </p> <div class="mw-heading mw-heading3"><h3 id="Arden_Sandstone_Formation">Arden Sandstone Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=5" title="Edit section: Arden Sandstone Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The formation is named after the <a href="/wiki/Forest_of_Arden" class="mw-redirect" title="Forest of Arden">Forest of Arden</a> in Warwickshire. It consists of a 2 m to 24 m thickness of mudstones, siltstones and sandstones with occasional pebble beds. It generally has a more greenish grey colour than the formations above and below it though it is not readily distinguishable within the sequence in Cheshire. it has locally yielded fossils suggestive of a marine-influenced environment.<sup id="cite_ref-bgs_5-0" class="reference"><a href="#cite_note-bgs-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> The Arden Sandstone is also known as North Curry Sandstone which is used as a building material in <a href="/wiki/Somerset" title="Somerset">Somerset</a>.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Sidmouth_Mudstone_Formation">Sidmouth Mudstone Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=6" title="Edit section: Sidmouth Mudstone Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg/220px-Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg/330px-Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg/440px-Cliffs_at_the_south_end_of_Gunthorpe_weir_-_geograph.org.uk_-_629291.jpg 2x" data-file-width="640" data-file-height="480" /></a><figcaption>Sidmouth Mudstone formation at <a href="/wiki/Gunthorpe,_Nottinghamshire" title="Gunthorpe, Nottinghamshire">Gunthorpe</a></figcaption></figure> <p>The formation includes several members which formerly enjoyed 'formation' status.<sup id="cite_ref-bgs2_7-0" class="reference"><a href="#cite_note-bgs2-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> This sequence was formerly known as the Eldersfield Mudstone Formation in the Worcester and Knowle basins and as the (combined) Edwalton, Gunthorpe and Radcliffe formations on the East Midlands Shelf. In the Cheshire Basin it supersedes the former Bollin Mudstone, Northwich Halite, Wych Mudstone, Byley Mudstone and Wilkesley Halite formations, each of which is now accorded 'member' status. It is of Anisian through Ladinian to <a href="/wiki/Carnian" title="Carnian">Carnian</a> age. </p> <div class="mw-heading mw-heading4"><h4 id="Wilkesley_Halite_member">Wilkesley Halite member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=7" title="Edit section: Wilkesley Halite member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Upper Keuper Saliferous Beds and as the Wilkesley Halite Formation (named from the Cheshire hamlet of <a href="/wiki/Dodcott_cum_Wilkesley" title="Dodcott cum Wilkesley">Wilkesley</a>), this member is Ladinian to Carnian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Wych_Mudstone_member">Wych Mudstone member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=8" title="Edit section: Wych Mudstone member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as (the upper part of) the Middle Keuper Marl and as the Wych Mudstone Formation (named from the <a href="/wiki/Wych_Brook" title="Wych Brook">Wych Brook</a> on the Cheshire/Flintshire/Shropshire border), this member is Anisian to Ladinian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Byley_Mudstone_member">Byley Mudstone member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=9" title="Edit section: Byley Mudstone member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as (the lower part of) the Middle Keuper Marl and as the Byley Mudstone Formation (named from the Cheshire village of <a href="/wiki/Byley" title="Byley">Byley</a>), this member is Anisian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Northwich_Halite_member">Northwich Halite member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=10" title="Edit section: Northwich Halite member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Lower Keuper Saliferous Beds and as the Northwich Halite Formation (named from the town of <a href="/wiki/Northwich" title="Northwich">Northwich</a>), this member is Anisian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Bollin_Mudstone_member">Bollin Mudstone member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=11" title="Edit section: Bollin Mudstone member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Lower Keuper Marl, lower mudstone and also as the Bollin Mudstone Formation (named from the <a href="/wiki/River_Bollin" title="River Bollin">River Bollin</a> in east <a href="/wiki/Cheshire" title="Cheshire">Cheshire</a>), this member is (?Scythian to) Anisian in age. </p><p>In West Cumbria, the Sidmouth Mudstone Formation is divided thus:<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Singleton_Mudstone_member">Singleton Mudstone member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=12" title="Edit section: Singleton Mudstone member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Singleton Mudstone Formation (named from the Lancashire village of <a href="/wiki/Singleton,_Lancashire" title="Singleton, Lancashire">Singleton</a>), this member is Early Triassic to Anisian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Kirkham_Mudstone_member">Kirkham Mudstone member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=13" title="Edit section: Kirkham Mudstone member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Kirkham Mudstone Formation (named from the small Lancashire town of <a href="/wiki/Kirkham,_Lancashire" title="Kirkham, Lancashire">Kirkham</a>), this member is Anisian to Ladinian in age. </p> <div class="mw-heading mw-heading4"><h4 id="Preesall_Halite_member">Preesall Halite member</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=14" title="Edit section: Preesall Halite member"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Formerly known as the Preesall Salt (named from the Lancashire village of <a href="/wiki/Preesall" title="Preesall">Preesall</a>), this member is Anisian to Ladinian in age. </p> <div class="mw-heading mw-heading3"><h3 id="Tarporley_Siltstone_Formation">Tarporley Siltstone Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=15" title="Edit section: Tarporley Siltstone Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Tarporley Siltstone Formation (named from the Cheshire village of <a href="/wiki/Tarporley" title="Tarporley">Tarporley</a>) is Anisian in age and comprises siltstones, mudstones and sandstones. The thickness of the sequence varies from 20 m in parts of the East Midlands to around 220m in the Cheshire Basin. It is encountered in older literature under various guises but commonly as the Keuper Waterstones or simply Waterstones.<sup id="cite_ref-bgs3_10-0" class="reference"><a href="#cite_note-bgs3-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>These rocks feature prominently along the <a href="/wiki/Mid_Cheshire_Ridge" title="Mid Cheshire Ridge">Mid Cheshire Ridge</a> where they form the summits of such hills as Eddisbury Hill and the <a href="/wiki/Delamere_Forest#OldPale" title="Delamere Forest">Old Pale</a> and the high ground around Tarporley and <a href="/wiki/Utkinton" title="Utkinton">Utkinton</a> together with small tracts of hilly country around <a href="/wiki/Runcorn" title="Runcorn">Runcorn</a> and <a href="/wiki/Warrington" title="Warrington">Warrington</a>.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The Malpas Sandstone Member is distinguished within this formation. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=16" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Geology_of_Cheshire" title="Geology of Cheshire">Geology of Cheshire</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Mercia_Mudstone_Group&action=edit&section=17" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-BgsLexicon-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-BgsLexicon_1-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFBritish_Geological_Survey_1998–2014_(c)NERC" class="citation web cs1">British Geological Survey 1998–2014 (c)NERC. <a rel="nofollow" class="external text" href="http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=MMG">"BGS Lexicon of Named Rock Units - Result Details"</a>. bgs.ac.uk<span class="reference-accessdate">. Retrieved <span class="nowrap">16 March</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=BGS+Lexicon+of+Named+Rock+Units+-+Result+Details&rft.pub=bgs.ac.uk&rft.au=British+Geological+Survey+1998%E2%80%932014+%28c%29NERC&rft_id=http%3A%2F%2Fwww.bgs.ac.uk%2FLexicon%2Flexicon.cfm%3Fpub%3DMMG&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: numeric names: authors list (<a href="/wiki/Category:CS1_maint:_numeric_names:_authors_list" title="Category:CS1 maint: numeric names: authors list">link</a>)</span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">Howard, A. S., Warrington, G., Ambrose, K. and Rees, J. G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04.</span> </li> <li id="cite_note-FW-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-FW_3-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://paleobiodb.org/classic/displayStrata?geological_group=Mercia%20Mudstone&group_formation_member=Mercia%20Mudstone">Mercia Mudstone Group</a> at <a href="/wiki/Fossilworks" title="Fossilworks">Fossilworks</a>.org</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">Howard, A. S., Warrington, G., Ambrose, K. and Rees, J. G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04. map on page 23</span> </li> <li id="cite_note-bgs-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-bgs_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=AS">"BGS Lexicon of Named Rock Units - Result Details"</a>. bgs.ac.uk<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-03-16</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=BGS+Lexicon+of+Named+Rock+Units+-+Result+Details&rft.pub=bgs.ac.uk&rft_id=http%3A%2F%2Fwww.bgs.ac.uk%2Flexicon%2Flexicon.cfm%3Fpub%3DAS&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.bgs.ac.uk/downloads/start.cfm?id=1619">"Strategic Stone Study: A Building Stone Atlas of Somerset and Exmoor"</a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/English_Heritage" title="English Heritage">English Heritage</a>. p. 10<span class="reference-accessdate">. Retrieved <span class="nowrap">11 October</span> 2011</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Strategic+Stone+Study%3A+A+Building+Stone+Atlas+of+Somerset+and+Exmoor&rft.pages=10&rft.pub=English+Heritage&rft_id=http%3A%2F%2Fwww.bgs.ac.uk%2Fdownloads%2Fstart.cfm%3Fid%3D1619&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-bgs2-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-bgs2_7-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=SIM">"BGS Lexicon of Named Rock Units - Result Details"</a>. bgs.ac.uk<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-03-16</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=BGS+Lexicon+of+Named+Rock+Units+-+Result+Details&rft.pub=bgs.ac.uk&rft_id=http%3A%2F%2Fwww.bgs.ac.uk%2Flexicon%2Flexicon.cfm%3Fpub%3DSIM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><i>Geological Survey of Great Britain (England and Wales) Barrow-in-Furness Sheet 58 1:50,000 Series, Solid and Drift Edition</i>. Institute of Geological Sciences. 1976.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Geological+Survey+of+Great+Britain+%28England+and+Wales%29+Barrow-in-Furness+Sheet+58+1%3A50%2C000+Series%2C+Solid+and+Drift+Edition&rft.pub=Institute+of+Geological+Sciences&rft.date=1976&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://mapapps.bgs.ac.uk/geologyofbritain/home.html?">"British Geological Survey"</a>. <i>Geology of Britain viewer</i><span class="reference-accessdate">. Retrieved <span class="nowrap">19 January</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Geology+of+Britain+viewer&rft.atitle=British+Geological+Survey&rft_id=http%3A%2F%2Fmapapps.bgs.ac.uk%2Fgeologyofbritain%2Fhome.html%3F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-bgs3-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-bgs3_10-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=TPSF">"BGS Lexicon of Named Rock Units - Result Details"</a>. bgs.ac.uk<span class="reference-accessdate">. Retrieved <span class="nowrap">2014-03-16</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=BGS+Lexicon+of+Named+Rock+Units+-+Result+Details&rft.pub=bgs.ac.uk&rft_id=http%3A%2F%2Fwww.bgs.ac.uk%2FLexicon%2Flexicon.cfm%3Fpub%3DTPSF&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMercia+Mudstone+Group" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text">British Geological Survey 1:50,000 scale geological map sheets (England and Wales series) 97 <i>Runcorn</i> and 109 <i>Chester</i></span> </li> </ol></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" 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