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Dohm’s Mystery Area

Dohm’s Mystery Area. James Dohm. Stratigraphy.

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Dohm’s Mystery Area

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  1. Dohm’s Mystery Area James Dohm

  2. Stratigraphy • Unit Ch – Channel material: (1) Elongate polygons (geometric shape), (2) networking polygons, (3) occurs within and dissected by drainages/channels (spatial relation with drainages/channels), (4) streamlined bedforms, (5) stratigraphic relations (onlaps and/or cuts other map units), (6) buried and/or inferred structures, (7) topography, (8) light to medium albedo (color). Interpretation: Fluvial deposits (10). • Unit Chp – Channel plains material: (1) Elongate polygons (geometric shape), (2) occurs within and dissected by drainages/channels and along the margins of Unit Ch (spatial relation with drainages/channels), (3) streamlined bedforms, (4) stratigraphic relations (onlaps and/or cuts other map units), (5) buried and/or inferred structures, (6) topography, (7) light to medium albedo (color). Interpretation: Fluvial deposits (10).

  3. Stratigraphy • Unit Pb – Bright plains-forming materials: (1) relatively flat, (2) topographic basin, (3) spatial relation with drainges, (4) structurally-controlled basin (paleohydrology), (5) distinct inward sloping contact/margin (e.g., scarp), (6) bright/light albedo (color). Interpretation: Lake deposits and/or evaporites (10). • Unit Pdc – Dark plains-forming materials—member c: (1) relatively flat, (2) occurs on the margin of hypothesized lacustrine deposits (spatial association), (3) topographic low, (4) buried and/or inferred structures, (5) dark materials. Interpretation: Lacustrine deposits and/or evaporites mantled by volcanic materials and eolian deposits (7), Fluvial deposits mantled by volcanic materials and eolian deposits (5), Colluvial deposits mantled by volcanic materials and eolian deposits (5), igneous materials associated with Units Mla-f (5) and/or sedimentary materials associated with Units Mla-f (3). • Unit Pdb – Dark plains-forming materials—member b: (1) relatively flat, (2) transected and/or embayed by channel deposits, (3) dissected by drainages, (4) buried and/or inferred structures, (5) topographically low with respect to other parts of the map region, (6) dark materials. Interpretation: (1) alluvial deposits (7); fluvial deposits (7).

  4. Stratigraphy • Unit Pda – Dark plains-forming materials—member a: (1) textured, plains-forming, (2) dissected materials, (3) buried and/or inferred structures, (4) transected and embayed by channel plains and alluvial deposits, and (5) mottled. Interpretation: Ancient alluvial deposits (7), igneous materials associated with Units Mla-f (5), and/or sedimentary materials associated with Units Mla-f (3). • Unit Fd – Flow materials—member d: (1) Fan-like morphology (fanning outward downslope), (2) flow fronts, (3) dissected by small, sinuous valleys that trend downslope from topographic highs (layered, mesa-forming materials—Unit Ml), (4) networking, (5) embays dark plains-forming materials (Unit Pda), (6) reddish-gray. Interpretation. Alluvial deposits (10). • Unit Fc – Flow materials—member d: (1) Fan-like morphology (fanning outward downslope), (2) flow fronts, (3) dissected by small, sinuous valleys that trend downslope from topographic highs (layered, mesa-forming materials—Unit Ml), (4) networking, (5) buried and/or inferred structures, (6) embays dark plains-forming materials (Unit Pda), (7) light and dark albedo materials. Interpretation: Alluvial deposits (7), In places, could include layered, mesa-forming materials (5) and/or flow materials—member a (5).

  5. Stratigraphy • Unit v – Vent materials: (1) topographic highs with often associated summit depressions, (2) spatial association with flow materials interpreted to be lava flows, (3) feature alignment (structural control), (4) ridges radial about summits (e.g., dikes), (5) spatial association with other alignments and tectonic structures with similar trends (e.g., marker of basement structural control), and (6) red (color). Interpretation: Magmatic-driven vent structures, which includes cinder cones and Maar (7) or mud volcanism (3). • Unit Fb – Flow materials—member b: (1) Fan-like morphology (fanning outward downslope), (2) flow occurs on the flanks of vent structures, (3) lobate flow fronts, (4) digitate flow fronts, and (5) black. Interpretation: Lava flow (10). • Unit Fa – Flow materials—member a: (1) Occurs among vent structures, several of which appear to be structurally controlled, (2) lobate flow fronts, (3) digitate flow fronts, (4) some individual flows appear to source from vent structrues, (5) fan-like deposits on some of the flanks of the vent structures, (6) buried and unburied structures, (7) reddish black. Interpretation: Igneous materials—mostly volcanic (7); parts could include layered, mesa-forming materials (5).

  6. Stratigraphy • Unit Ml/Mla-f — Layered, mesa-forming materials—members a-f: (1) forms highly degraded promontories/mesas, (2) layered materials, (3) spatially associated with vent structures (Unit v) and flow materials (Unit Fa), (4) differentially eroded, (5) density of tectonic structures appears to be an order of magnitude greater than younger materials, (6) irregular topography, (7) diverse colors. Interpretation: Igneous materials—mostly volcanic (7); sedimentary deposits (3) {{don’t see triangular faceted beds}}.

  7. Tectonic Structures • Solid line – linaments: (1) linear features, which cut rock materials, (2) forms linear scarps, (3) forms linear contacts, (4) en echelon systems, (5) trends similar to other structures, (6) systems of structures, (7) some transfer into vent aligments. Interpretation: Tectonic structures (7): faults (7)—extensional (7), strike-slip (7), contractional (5); erosional scarps (3). • Dotted line – buried and/or inferred: (1) subdued linear features, (2) linear drainages, (3) forms subdued linear scarps, (3) forms linear contacts, (4) en echelon systems, (5) trends similar to other structures, (6) systems of structures, (7) some transfer into vent aligments. Interpretation: Buried tectonic structures (7): faults (7)—extensional (7), strike-slip (7), contractional (5); drainages not structurally controlled (3); erosional scarps (3). • White line – Vent-related scarps: (1) curvilinear scarps, (2) associated with vent structures (Unit v) and flow materials (Unit Fa), (3) some associated with vent structures. Interpretation: Scarps resulting from magmatic-driven activity (e.g., venting to form cinder cones and Maar) and subsequent erosion (7), features associated with mud volcanism (3), features associated with collapse not necessarily related to magmatic-driven activity (3). • Red line – Vent aligments: (1) alignment of 3 or more vent structures, (2) some transfer into tectonic structures, (3) trends similar to tectonic structures. Interpretation: Structurally-controlled vents associated with magmatism (7); Structurally-controlled mud volcanism (3)

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