Altar Stone diagnostic toggle map

Leave-one-out instrument. A place survives if it fails no ON layer. Untested is not a fail. Published evidence, field prioritisation, and open criteria are shown separately.

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Measured matches

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Open ground

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Named sites still failed

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Clusters already passed the published Ba ≥ 1025 ppm and Ba/Rb P95 screen. L1/L2 ON therefore keeps the cluster universe; OFF brings in named localities that never made a cluster. L7 ON fails the Sarclet local Ro 3.1–4.7% site and Hillier & Marshall 1992 points (Fig 4 type-sections); it does not 0-score other candidates from those points. RELAXED spreads high-Ro points 20 km — that is the over-generalisation test. L9 starts OFF because the Altar Stone has no published Lower/Middle assignment. L10 (Sr ceiling) and L11 (Sr/Ca) start OFF. They score only places where rock Sr has been measured; blue-ringed dots are the measured-Sr reference localities (Castletown, Dounreay BH1, Stenness/Brodgar). Cluster 18, Sarclet, Braemore, Latheron and Tarbat have no Sr data and stay untested. U1 and U2 apply the chrome-spinel (CZi) and illite/smectite-expandability results of Pirrie et al. (2026, J. Geol. Soc. 183, jgs2026-090). They start off, like L10 and L11, so the baseline screen stays comparable with earlier versions; switch them on to add those exclusions. Not scored, because the paper leaves them open or gives no comparison data: the Lanark Basin (a Ba-anomaly area with no chrome-spinel, zircon or clay data); the ORS between the Midland Valley and the Welsh Borders (no modern heavy-mineral or zircon data); Carboniferous sandstones such as the chrome-spinel-rich Clifton Rock (zircon and Sr–Nd differ, not excluded outright); and the Sr–Nd result itself (MS1/MS2 ⁸⁷Sr/⁸⁶Sr 0.7163–0.7169, ¹⁴³Nd/¹⁴⁴Nd 0.5119–0.5121; ORS Nd overlaps, but no ORS Sr data exist). The paper excludes the Southern Uplands on kaolinite (no low-grade metamorphism); the map has no Southern Uplands entry. The orange underlay is BGS Geology 625k Old Red Sandstone (GB + NI), plus the continental Devonian red-bed groups that BGS 625k names by group rather than as ORS (Fintona, Shanmullagh, Cross Slieve; Stratheden, Arbuthnott–Garvock, Strathmore, Dunnottar–Crawton), and sandstone/conglomerate units of the undifferentiated Lower/Upper Devonian and Pridoli in Wales and the Welsh Borders. SW England and Devon marine Devonian is not included; Republic basins (Dingle, Munster, Curlew, Clew Bay) are dashed schematic. The purple dashed ribbon is the Hillier & Marshall 1992 Latheron–Niandt cool sliver: schematic, not a cluster, not a source claim.