Reconstruct a site from materials, chronology, map and subsurface evidence

Integrate evidence without erasing its origin

The original cumulative packet geo-site-defense@1 describes a fictional site with granite basement B, sandstone S containing granite clasts, an ash A within the top of the sandstone sequence, tilted strata T, an erosional surface E and horizontal gravel G. These supplied observations require B before S before A before T before E before G. A fault F cuts the ash, but its relation to tilt and erosion has not been observed. All drawings, ages and observations are invented; earlier actual USGS records retain their own locations and are not measurements of this site.

Exact supplied ages are basement 120 Ma, ash 20 Ma and gravel 10 Ma. Granite clasts support an older source than the host sandstone; an ash age dates that event rather than every grain or the entire formation. The tilted layers truncated beneath horizontal gravel establish deformation and erosion before the gravel. An observation table must distinguish these relationships from assumptions such as closed isotope behavior or correct marker correlation.

The original ash plane before the unknown fault offset is z=100−0.5x, with x east and z elevation in meters. Strike is north–south; true dip is arctan(0.5)≈26.565° east. At horizontal ground elevation 60 m its contact is x=80 m. A north–south section follows strike and has zero apparent dip, even though true dip is not zero. These map constraints connect orientation to a testable borehole prediction rather than treating a diagram as decoration.

If gravel seals F, three event orders remain because F may occur after ash, after tilt or after erosion, provided it remains before gravel. If F offsets gravel, it must follow G and only one supplied order remains. An unobserved contact permits all four. Sealing brackets the fault between 20 and 10 Ma but does not date it exactly; offset of 10 Ma gravel says younger than 10 Ma, not active today. An independent correlation or new exposure could revise the model.

Reconstruct the worked packet

With sealing observed and the candidate fault placed after tilt, B→S→A→T→F→E→G is compatible, but not uniquely established. The other compatible positions are after A and after E. At x=20 m, the pre-offset ash plane predicts z=90 m; at x=60 m it predicts z=70 m. These are calculated predictions from an invented plane, not measured cores.

Predict, investigate and retain

Predict first: What new relationship would distinguish faulting before gravel from faulting after gravel without claiming a precise earthquake date?

Retain the original seven-event observation table, annotated coordinate map and all allowed orders before selecting one. Change sealing to offset and then to unknown; identify which exclusions disappear. Verify one apparent-dip calculation and explain what a failed borehole prediction would challenge.

Mechanism context, checked 30 October 2026. All numerical and site-history packets here are original invented cases.