https://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&feed=atom&action=historyChemostratigraphy of the Upper Carboniferous Schooner Formation, southern North Sea - Revision history2024-03-29T13:50:29ZRevision history for this page on the wikiMediaWiki 1.41.0https://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=45615&oldid=prevDbk at 10:15, 11 May 20202020-05-11T10:15:57Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Stone, G. & A. Moscariello 1999. Integrated modelling of the southern North Sea Carboniferous Barren Red Measures using production data, geochemistry, and pedofacies cyclicity. Paper (56898) presented at the SPE Offshore Europe 99 conference, Aberdeen, September 1999, 1–8.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Stone, G. & A. Moscariello 1999. Integrated modelling of the southern North Sea Carboniferous Barren Red Measures using production data, geochemistry, and pedofacies cyclicity. Paper (56898) presented at the SPE Offshore Europe 99 conference, Aberdeen, September 1999, 1–8.</div></td></tr>
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</table>Dbkhttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42079&oldid=prevScotfot at 14:07, 14 August 20192019-08-14T14:07:14Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:YGS_CHR_10_CHEM_FIG_01.jpg|thumbnail|Figure 1 Location of wells 44/21-3, 44/21-7 and 44/26c-6. The asterisk (*) indicates the location of other UK sector wells that have penetrated the Schooner Formation and which have been the subjects of proprietary chemostratigraphical studies.]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:YGS_CHR_10_CHEM_FIG_01.jpg|thumbnail|Figure 1 Location of wells 44/21-3, 44/21-7 and 44/26c-6. The asterisk (*) indicates the location of other UK sector wells that have penetrated the Schooner Formation and which have been the subjects of proprietary chemostratigraphical studies.]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:YGS_CHR_10_CHEM_FIG_02.jpg|thumbnail|Figure 2 Study interval of well 44/21-3. Lithostratigraphy from Cameron(1993).]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:YGS_CHR_10_CHEM_FIG_02.jpg|thumbnail|Figure 2 Study interval of well 44/21-3. Lithostratigraphy from Cameron(1993).]]</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42078&oldid=prevScotfot: /* Summary */2019-08-14T10:41:07Z<p><span dir="auto"><span class="autocomment">Summary</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Summary ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== Summary ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The virtually barren, mainly redbed sequences of the Schooner Formation (Upper Carboniferous) of the southern North Sea are an important gas reservoir, although well placement and reservoir development are hampered by the lack of a reliable strati-graphical framework. Chemostratigraphy has enabled the Schooner Formation encountered in well 44/21-3 to be divided into three chemostratigraphical units (S1, S2 and S3) and eleven sub-units (S1a–f, S2a–b and S3a–c), based on variations in mud-stone and sandstone geochemical data acquired from core samples and cuttings. The geochemical characteristics of the units can be related to variations in mineralogy, depositional environment, climate and provenance. The units are correlated sub-regionally and the correlation is used to corroborate seismic correlations. A high-resolution chemostratigraphical zonation and correlation based on sub-units redefines models of reservoir architecture and enhances reservoir development in the nearby Schooner field.== Introduction ==</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The virtually barren, mainly redbed sequences of the Schooner Formation (Upper Carboniferous) of the southern North Sea are an important gas reservoir, although well placement and reservoir development are hampered by the lack of a reliable strati-graphical framework. Chemostratigraphy has enabled the Schooner Formation encountered in well 44/21-3 to be divided into three chemostratigraphical units (S1, S2 and S3) and eleven sub-units (S1a–f, S2a–b and S3a–c), based on variations in mud-stone and sandstone geochemical data acquired from core samples and cuttings. The geochemical characteristics of the units can be related to variations in mineralogy, depositional environment, climate and provenance. The units are correlated sub-regionally and the correlation is used to corroborate seismic correlations. A high-resolution chemostratigraphical zonation and correlation based on sub-units redefines models of reservoir architecture and enhances reservoir development in the nearby Schooner field.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>== Introduction ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Traditionally, interwell correlation for most reservoir sequences is achieved by using a combination of seismic, wireline log, biostratigraphical and sedimentological data. However, these techniques cannot always produce the required resolution for detailed stratigraphical modelling, particularly when dealing with barren fluvial sequences. Furthermore, the occurrence of thick monotonous successions of sandstones and mudstones, with repetitive wireline log characteristics and no prominent seismic reflectors, often makes correlating such sequences difficult. To refine the stratigraphy of such successions, palaeomagnetism (Hauger et al. 1994), heavy-mineral analysis (Morton 1985, 1991, Morton & Hallsworth 1994, Mange-Rajetzky 1995, Morton & Hurst 1995) and isotopic techniques (Mearns 1988, 1989) are often utilized, although their success is often hampered by poor sample quality, insufficient sample volume, or dependency upon a specific lithology. Consequently, a method is needed that can generate independent stratigraphical frameworks for barren well sections (and fossiliferous successions) and is not restricted by sample type. Such a method is chemical stratigraphy, or as it is more commonly known, chemostratigraphy.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Traditionally, interwell correlation for most reservoir sequences is achieved by using a combination of seismic, wireline log, biostratigraphical and sedimentological data. However, these techniques cannot always produce the required resolution for detailed stratigraphical modelling, particularly when dealing with barren fluvial sequences. Furthermore, the occurrence of thick monotonous successions of sandstones and mudstones, with repetitive wireline log characteristics and no prominent seismic reflectors, often makes correlating such sequences difficult. To refine the stratigraphy of such successions, palaeomagnetism (Hauger et al. 1994), heavy-mineral analysis (Morton 1985, 1991, Morton & Hallsworth 1994, Mange-Rajetzky 1995, Morton & Hurst 1995) and isotopic techniques (Mearns 1988, 1989) are often utilized, although their success is often hampered by poor sample quality, insufficient sample volume, or dependency upon a specific lithology. Consequently, a method is needed that can generate independent stratigraphical frameworks for barren well sections (and fossiliferous successions) and is not restricted by sample type. Such a method is chemical stratigraphy, or as it is more commonly known, chemostratigraphy.</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42077&oldid=prevScotfot: /* References */2019-08-14T10:40:18Z<p><span dir="auto"><span class="autocomment">References</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M. 2002. Late Carboniferous redbeds of the UK southern North Sea viewed in a regional context [abstract: pp. 17–20]. This volume: 225–226.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M. 2002. Late Carboniferous redbeds of the UK southern North Sea viewed in a regional context [abstract: pp. 17–20]. This volume: 225–226.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M. & C. J. Cleal 1997. Upper Carboniferous stratigraphy of the West Midlands (UK) revised in the light of borehole geophysical logs and detrital compositional suites. ''Geological Journal ''32, <del style="font-weight: bold; text-decoration: none;">85– 118</del>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M. & C. J. Cleal 1997. Upper Carboniferous stratigraphy of the West Midlands (UK) revised in the light of borehole geophysical logs and detrital compositional suites. ''Geological Journal ''32, <ins style="font-weight: bold; text-decoration: none;">85–118</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M., S. D. Burley, P. Turner 1993. The late Carboniferous “Barren Red Bed” play of the Silver Pit area, southern North Sea. In ''Petroleum geology of northwest Europe: proceedings of the 4th conference'', J. R. Parker (ed.), 727–40. London: Geological Society. Blatt, H., G. Middleton, R. Murray 1972. ''Origin of sedimentary rocks''. Englewood Cliffs, New Jersey: Prentice-Hall.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Besly, B. M., S. D. Burley, P. Turner 1993. The late Carboniferous “Barren Red Bed” play of the Silver Pit area, southern North Sea. In ''Petroleum geology of northwest Europe: proceedings of the 4th conference'', J. R. Parker (ed.), 727–40. London: Geological Society. Blatt, H., G. Middleton, R. Murray 1972. ''Origin of sedimentary rocks''. Englewood Cliffs, New Jersey: Prentice-Hall.</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42076&oldid=prevScotfot: /* 4.2 Binary diagrams */2019-08-14T10:39:03Z<p><span dir="auto"><span class="autocomment">4.2 Binary diagrams</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[:File:YGS_CHR_10_CHEM_FIG_07.jpg|Figure 7]] shows Rb, Cs and Na<sub>2</sub>O all have a close affinity with K<sub>2</sub>O. Correlation coefficients for Rb: K<sub>2</sub>O (0.77) and for Rb:Cs (0.67; [[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]c) indicate that Rb and Cs levels are governed chiefly by variations in clay-mineral abundance. Apart from S3b, the plots of the S3 samples form a well defined linear trend on the Rb vs Cs binary diagram ([[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]d); the S3b samples do not plot on this trend, as they have high Cs levels. Cs levels increase at the base of S3b and coincide with the first appearance of chlorite (Pearce et al. 2005).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[:File:YGS_CHR_10_CHEM_FIG_07.jpg|Figure 7]] shows Rb, Cs and Na<sub>2</sub>O all have a close affinity with K<sub>2</sub>O. Correlation coefficients for Rb: K<sub>2</sub>O (0.77) and for Rb:Cs (0.67; [[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]c) indicate that Rb and Cs levels are governed chiefly by variations in clay-mineral abundance. Apart from S3b, the plots of the S3 samples form a well defined linear trend on the Rb vs Cs binary diagram ([[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]d); the S3b samples do not plot on this trend, as they have high Cs levels. Cs levels increase at the base of S3b and coincide with the first appearance of chlorite (Pearce et al. 2005).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Na<sub>2</sub>O usually has affinities with clay minerals, feldspar and evaporite minerals. Halite and anhydrite cements occur locally in the sandstones near the top of the Ketch Member (Cameron 1993) and traces of anhydrite cement are recorded from the S3 sandstones in well 44/21-3 (Pearce et al. 2005). Nevertheless,</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Na<sub>2</sub>O usually has affinities with clay minerals, feldspar and evaporite minerals. Halite and anhydrite cements occur locally in the sandstones near the top of the Ketch Member (Cameron 1993) and traces of anhydrite cement are recorded from the S3 sandstones in well 44/21-3 (Pearce et al. 2005). Nevertheless, Na<sub>2</sub>O data from cuttings can be unreliable if drilling fluids have contaminated the samples. Moreover, most of the geochemical data included in this study come from cuttings, and whether or not drilling fluids have contaminated these samples is unknown, so the Na<sub>2</sub>O data are ignored.</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div> </div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Na<sub>2</sub>O data from cuttings can be unreliable if drilling fluids have contaminated the samples. Moreover, most of the geochemical data included in this study come from cuttings, and whether or not drilling fluids have contaminated these samples is unknown, so the Na<sub>2</sub>O data are ignored.</div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>CaO and MgO are usually associated with calcite, dolomite and ferroan carbonates, with the relatively high CaO levels (5– 6%) in S3 and S2b probably being related to dolomitized caliche horizons that formed during pedogenesis together with occasional freshwater limestones (Besly et al. 1993). High CaO and MgO levels together reflect the presence of carbonate minerals, whereas low concentrations are linked to clay minerals. These conclusions are supported by the positive linear trend defined by the S1 and S2 sample plots on [[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]e. Only MgO levels are relatively high in S3, with sub-unit 3b having the highest levels of all ([[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]f); so here, MgO is probably associated with clay minerals, these high levels coinciding with an increase in chlorite (?corrensite)/smectite (Pearce et al. 2005).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>CaO and MgO are usually associated with calcite, dolomite and ferroan carbonates, with the relatively high CaO levels (5– 6%) in S3 and S2b probably being related to dolomitized caliche horizons that formed during pedogenesis together with occasional freshwater limestones (Besly et al. 1993). High CaO and MgO levels together reflect the presence of carbonate minerals, whereas low concentrations are linked to clay minerals. These conclusions are supported by the positive linear trend defined by the S1 and S2 sample plots on [[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]e. Only MgO levels are relatively high in S3, with sub-unit 3b having the highest levels of all ([[:File:YGS_CHR_10_CHEM_FIG_08.jpg|Figure 8]]f); so here, MgO is probably associated with clay minerals, these high levels coinciding with an increase in chlorite (?corrensite)/smectite (Pearce et al. 2005).</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l172">Line 172:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]d shows that Nb has a positive relationship with TiO<sub>2</sub> (Nb: TiO<sub>2</sub> correlation coefficient of 0.73), thus rutile abundance may well govern Nb levels. Ta also has a positive relationship with Nb ([[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]e) and, like Nb, Ta is associated with the distribution of rutile. Cr plots with a loose positive relationship (especially in samples from S1 and S3) with TiO<sub>2</sub> and with Zr ([[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]f–h), indicating that Cr is associated with the distribution of heavy minerals, particularly Cr-spinel, which is common in the Ketch Member (Morton et al. 2005).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]d shows that Nb has a positive relationship with TiO<sub>2</sub> (Nb: TiO<sub>2</sub> correlation coefficient of 0.73), thus rutile abundance may well govern Nb levels. Ta also has a positive relationship with Nb ([[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]e) and, like Nb, Ta is associated with the distribution of rutile. Cr plots with a loose positive relationship (especially in samples from S1 and S3) with TiO<sub>2</sub> and with Zr ([[:File:YGS_CHR_10_CHEM_FIG_09.jpg|Figure 9]]f–h), indicating that Cr is associated with the distribution of heavy minerals, particularly Cr-spinel, which is common in the Ketch Member (Morton et al. 2005).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Zr is linked to zircon, which is more common in S1 than in S3. The positive relationship between Hf and Zr (Zr:Hf correlation coefficient of 0.97) implies that Hf levels are controlled by zircon distribution and abundance.== 5. Sandstone chemostratigraphy and mineralogy ==</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Zr is linked to zircon, which is more common in S1 than in S3. The positive relationship between Hf and Zr (Zr:Hf correlation coefficient of 0.97) implies that Hf levels are controlled by zircon distribution and abundance.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>== 5. Sandstone chemostratigraphy and mineralogy ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The sandstone dataset for well 44/21-3 relates to the uppermost part of the Lower Ketch Unit and the Upper Ketch Unit. Added to the dataset are sandstone data acquired from the Lower Ketch Unit encountered in well 44/21-7. Although the well 44/21-3 dataset is too small to establish a chemostratigraphical zonation, the main geochemical characteristics of the sandstones can be summarized, certain element–mineral affinities can be established, and comments can be made regarding provenance.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The sandstone dataset for well 44/21-3 relates to the uppermost part of the Lower Ketch Unit and the Upper Ketch Unit. Added to the dataset are sandstone data acquired from the Lower Ketch Unit encountered in well 44/21-7. Although the well 44/21-3 dataset is too small to establish a chemostratigraphical zonation, the main geochemical characteristics of the sandstones can be summarized, certain element–mineral affinities can be established, and comments can be made regarding provenance.</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42075&oldid=prevScotfot: /* 3.2 Mudstone chemostratigraphy */2019-08-14T10:33:12Z<p><span dir="auto"><span class="autocomment">3.2 Mudstone chemostratigraphy</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:33, 14 August 2019</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l84">Line 84:</td>
<td colspan="2" class="diff-lineno">Line 84:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>One of the best ways to present the mudstone geochemical data is as geochemical profiles ([[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]], [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]], which are constructed by plotting element concentrations against sample depth. In [[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], the Al<sub>2</sub>O<sub>3</sub> profile is based on absolute concentrations, whereas the other profiles and those in [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]] relate to Al<sub>2</sub>O<sub>3</sub>-normalized ratios for selected elements. Normalizing the data in this way nullifies any changes in geochemistry attributable to grain-size variations in the individual samples. The profile format enables element enrichments, depletions and significant strati-graphical geochemical trends to be recognized quite easily, from which a chemostratigraphical zonation can be developed. In addition, geochemical profiles based on other element ratios (e.g. Cr/Cs, Ta/U, etc.), are depicted in [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]] to highlight specific mineralogical trends.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>One of the best ways to present the mudstone geochemical data is as geochemical profiles ([[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]], [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]], which are constructed by plotting element concentrations against sample depth. In [[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], the Al<sub>2</sub>O<sub>3</sub> profile is based on absolute concentrations, whereas the other profiles and those in [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]] relate to Al<sub>2</sub>O<sub>3</sub>-normalized ratios for selected elements. Normalizing the data in this way nullifies any changes in geochemistry attributable to grain-size variations in the individual samples. The profile format enables element enrichments, depletions and significant strati-graphical geochemical trends to be recognized quite easily, from which a chemostratigraphical zonation can be developed. In addition, geochemical profiles based on other element ratios (e.g. Cr/Cs, Ta/U, etc.), are depicted in [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]] to highlight specific mineralogical trends.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The chemostratigraphical zonation of the Schooner Formation in well 44/21-3 is based on the data for the major elements Al<sub>2</sub>O<sub>3</sub>, <del style="font-weight: bold; text-decoration: none;">{{anchor|DdeLink16942778352691}} </del>TiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>, MgO, CaO, K<sub>2</sub>O and P<sub>2</sub>O<sub>5</sub>, the trace elements Cr, Cs, Hf, Nb, Ni, Rb, Ta, Th, Y and Zr, and the REEs La and Ce, these elements being referred to as chemostratigraphical index elements.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The chemostratigraphical zonation of the Schooner Formation in well 44/21-3 is based on the data for the major elements Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub>, MgO, CaO, K<sub>2</sub>O and P<sub>2</sub>O<sub>5</sub>, the trace elements Cr, Cs, Hf, Nb, Ni, Rb, Ta, Th, Y and Zr, and the REEs La and Ce, these elements being referred to as chemostratigraphical index elements.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Interpretation of the geochemical profiles for the index elements, most of which are illustrated in [[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]], [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]], allows the well 44/21-3 study interval to be divided into units W, S1, S2, S3 and P. Their geochemical characteristics are described below. (Units and Sub-units may be referred to by their numbers alone hereinafter, e.g. Unit S1 as “S1” and Sub-unit S3a as “S3a”.)</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Interpretation of the geochemical profiles for the index elements, most of which are illustrated in [[:File:YGS_CHR_10_CHEM_FIG_03.jpg|Figure 3]], [[:File:YGS_CHR_10_CHEM_FIG_04.jpg|Figure 4]], [[:File:YGS_CHR_10_CHEM_FIG_05.jpg|Figure 5]], allows the well 44/21-3 study interval to be divided into units W, S1, S2, S3 and P. Their geochemical characteristics are described below. (Units and Sub-units may be referred to by their numbers alone hereinafter, e.g. Unit S1 as “S1” and Sub-unit S3a as “S3a”.)</div></td></tr>
</table>Scotfothttps://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42074&oldid=prevScotfot: Created page with "File:YGS_CHR_10_CHEM_FIG_01.jpg|thumbnail|Figure 1 Location of wells 44/21-3, 44/21-7 and 44/26c-6. The asterisk (*) indicates the location of other UK sector wells that hav..."2019-08-14T10:31:59Z<p>Created page with "File:YGS_CHR_10_CHEM_FIG_01.jpg|thumbnail|Figure 1 Location of wells 44/21-3, 44/21-7 and 44/26c-6. The asterisk (*) indicates the location of other UK sector wells that hav..."</p>
<a href="https://earthwise.bgs.ac.uk/index.php?title=Chemostratigraphy_of_the_Upper_Carboniferous_Schooner_Formation,_southern_North_Sea&diff=42074">Show changes</a>Scotfot