Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland
<p>Planorbis to Turneri Zone sedimentary rocks were studied at outcrops on Skye, Raasay, Applecross, Ardnamurchan, Morvern and Mull. A proposed lithostratigraphy includes two Groups, four Formations and seventeen Members. Increased faunal diversity in Mull and Skye reflects environmental stab...
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| Format: | Thesis |
| Language: | English |
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1978
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| _version_ | 1797096015412592640 |
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| author | Amiri-Garroussi, K Amiri-Garroussi, Kourosh |
| author2 | Hallam, A |
| author_facet | Hallam, A Amiri-Garroussi, K Amiri-Garroussi, Kourosh |
| author_sort | Amiri-Garroussi, K |
| collection | OXFORD |
| description | <p>Planorbis to Turneri Zone sedimentary rocks were studied at outcrops on Skye, Raasay, Applecross, Ardnamurchan, Morvern and Mull. A proposed lithostratigraphy includes two Groups, four Formations and seventeen Members. Increased faunal diversity in Mull and Skye reflects environmental stability during the Angulata and Semicostatum Zones; low diversity in the Bucklandi and Turneri Zones signifies lower stability. Species abundance in Mull and their decrease in Skye during Angulata-Bucklandi Zone times signifies a northward increase in environmental instability.</p> <p>Smectites are present in the Planorbis-Bucklandi Zone shales. The Semicostatum-Turneri Zones are composed of non expanding clays; the smectite formed by erosion of previously exposed alkaline igneous rocks under warm, alkaline, low rainfall conditions. Progressive transgression covered the source area and a change to more acidic conditions with higher rainfall also promoted the formation of "ironstones" and chlorites.</p> <p>The Angulata and Bucklandi Zones comprise bioclastic, oolitic, carbonate and siliciclastic sediments signifying shallow marginal marine semi-enclosed basins. Thin laterally impersistent beds of coarse,poorly sorted pebbles signify an unstable hinterland; during the Semicostatum and Turneri Zones fully marine conditions were established.</p> <p>Ferruginous beds are oolitic in Skye. They probably formed as "mud balls" and due to acid leaching of feldspars. Phosphatic nodules are calciumhydroxyapatite.</p> <p>The limestone/shale "rhythms" are explained by a combined primary and diagenetic origin. The limestones consist of low-Mg calcite Both ferroan and non ferroan calcite are present. Tectonic stresses and diagenesis deformed crystals and formed veins.</p> <p>Sr<sup>+2</sup> values show a decline as the carbonate fraction increases. Three different ranges are distinguished for three facies and ages. Sr concentration is bimodal and probably inherited from the original sediments.</p> <p>The northern and southern basins evolved separately, sedimentation was controlled by differential tilting, uplift and subsidence. Palaeoslopes were gentle, to the west-northwest and south-southwest. Local topography (e.g. Central Strath High) modified the slopes; no movement occurred along the main faults of the area. Sedimentation relates to the "taphrogenic rifting stage" proposed for the North Sea Mesozoic.</p> |
| first_indexed | 2024-03-07T04:36:06Z |
| format | Thesis |
| id | oxford-uuid:cff8f820-9b8b-4f95-ac09-7e99039b5fd1 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T04:36:06Z |
| publishDate | 1978 |
| record_format | dspace |
| spelling | oxford-uuid:cff8f820-9b8b-4f95-ac09-7e99039b5fd12022-03-27T07:46:34ZSedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west ScotlandThesishttp://purl.org/coar/resource_type/c_db06uuid:cff8f820-9b8b-4f95-ac09-7e99039b5fd1Sedimentary rocksScotlandSedimentologyBroadford (Scotland)Sediments (Geology)Geology, StratigraphicEnglishPolonsky Theses Digitisation Project1978Amiri-Garroussi, KAmiri-Garroussi, KouroshHallam, AHallam, A<p>Planorbis to Turneri Zone sedimentary rocks were studied at outcrops on Skye, Raasay, Applecross, Ardnamurchan, Morvern and Mull. A proposed lithostratigraphy includes two Groups, four Formations and seventeen Members. Increased faunal diversity in Mull and Skye reflects environmental stability during the Angulata and Semicostatum Zones; low diversity in the Bucklandi and Turneri Zones signifies lower stability. Species abundance in Mull and their decrease in Skye during Angulata-Bucklandi Zone times signifies a northward increase in environmental instability.</p> <p>Smectites are present in the Planorbis-Bucklandi Zone shales. The Semicostatum-Turneri Zones are composed of non expanding clays; the smectite formed by erosion of previously exposed alkaline igneous rocks under warm, alkaline, low rainfall conditions. Progressive transgression covered the source area and a change to more acidic conditions with higher rainfall also promoted the formation of "ironstones" and chlorites.</p> <p>The Angulata and Bucklandi Zones comprise bioclastic, oolitic, carbonate and siliciclastic sediments signifying shallow marginal marine semi-enclosed basins. Thin laterally impersistent beds of coarse,poorly sorted pebbles signify an unstable hinterland; during the Semicostatum and Turneri Zones fully marine conditions were established.</p> <p>Ferruginous beds are oolitic in Skye. They probably formed as "mud balls" and due to acid leaching of feldspars. Phosphatic nodules are calciumhydroxyapatite.</p> <p>The limestone/shale "rhythms" are explained by a combined primary and diagenetic origin. The limestones consist of low-Mg calcite Both ferroan and non ferroan calcite are present. Tectonic stresses and diagenesis deformed crystals and formed veins.</p> <p>Sr<sup>+2</sup> values show a decline as the carbonate fraction increases. Three different ranges are distinguished for three facies and ages. Sr concentration is bimodal and probably inherited from the original sediments.</p> <p>The northern and southern basins evolved separately, sedimentation was controlled by differential tilting, uplift and subsidence. Palaeoslopes were gentle, to the west-northwest and south-southwest. Local topography (e.g. Central Strath High) modified the slopes; no movement occurred along the main faults of the area. Sedimentation relates to the "taphrogenic rifting stage" proposed for the North Sea Mesozoic.</p> |
| spellingShingle | Sedimentary rocks Scotland Sedimentology Broadford (Scotland) Sediments (Geology) Geology, Stratigraphic Amiri-Garroussi, K Amiri-Garroussi, Kourosh Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title | Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title_full | Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title_fullStr | Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title_full_unstemmed | Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title_short | Sedimentological and palaeoenvironmental studies in the Broadford Beds (Hettangian-Sinemurian) of north-west Scotland |
| title_sort | sedimentological and palaeoenvironmental studies in the broadford beds hettangian sinemurian of north west scotland |
| topic | Sedimentary rocks Scotland Sedimentology Broadford (Scotland) Sediments (Geology) Geology, Stratigraphic |
| work_keys_str_mv | AT amirigarroussik sedimentologicalandpalaeoenvironmentalstudiesinthebroadfordbedshettangiansinemurianofnorthwestscotland AT amirigarroussikourosh sedimentologicalandpalaeoenvironmentalstudiesinthebroadfordbedshettangiansinemurianofnorthwestscotland |