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Location Map-Outcrops in Red (#1-#7-North to South) Scale: 1 cm = 200 m Source: USGS-Salamanca Quadrangle (2016)

Location Map-Outcrops in Red (#1-#7-North to South) Scale: 1 cm = 200 m Source: USGS-Salamanca Quadrangle (2016)

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The orthoquartzitic Salamanca conglomerate records a high-energy Upper Devonian seacoast, with at least meso-tidal range, as indicated by a pebbly shoreface and beach, a tide-dominated delta prograding over marine wave-rippled fine sands, and a sub-aqueous large-scale (4m-6m foresets) dune field formed by strong flood tides. Most of the sequence re...

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... "iron ore" (hematite) seams of Hall (1843) are red to black in color, 1-3 cm thick, usually sub- horizontal but often smoothly contorted and commonly crosscut bedding. The seams appear most common higher in the sequence and in close association with fluvial/deltaic channels/redbeds and plant remains ( Fig. 2 -outcrop #1). In the dune field (outcrop #7), iron seams cover several vertical joint surfaces (Fig. 3). And rare cylindrical shapes (10-20 cm in diameter) are suggestive of hollow ...
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... (1963; Fig. 16) portrayed a coarsening-upward Cattaraugus formation with about six alternating repetitions of lithofacies (gray siltstones -buff sandstones -conglomerates). While generalized, his lithofacies curve suggests small-scale oscillations in relative sea level (T-R cycles) that are more pronounced and frequent than in underlying formations. ...
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... with some trough (sinuously crested = 3D type) evident in channel deposits and upper shoreface/lower foreshore depsoits. Smaller forms may display bi-directional foresets in places (Fig. 8) but are more commonly organized in stacked co-sets ( Fig. 9 ; cosets are ~ 0.75 m thick and show wave influence at the tops, e.g., centered on the 3' tape; Fig. 10 shows fine sand drapes, possible tidal influence and at the interface, wave ripples occur, then a 1 m thick cross-strata with angular toesets; small and large x-strata align shoreward; outcrop #1 ). The largest cross-strata (0.50 -5 m) increase in size and abundance from north to south across the outcrop belt. At the southernmost ...
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... outcrop #1 ). The largest cross-strata (0.50 -5 m) increase in size and abundance from north to south across the outcrop belt. At the southernmost outcrops at "Little Rock City", large foresets may comprise ~ 75% of the outcrop exposures with dips of 20 o -30 o , no obvious or major reactivation surfaces, and most toesets are tangential ( Fig. 11; largest foresets ~ 5.5 m). Some foresets are traceable for +150 m across several blocks and a planar truncation surface at the top of the dunes shows wave influence (e.g., wave ripples with crests parallel to the paleo-shore). About 1 m of low-angle stratification overlies this interface followed by about 2+ meters of gray and red ...
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... are traceable for +150 m across several blocks and a planar truncation surface at the top of the dunes shows wave influence (e.g., wave ripples with crests parallel to the paleo-shore). About 1 m of low-angle stratification overlies this interface followed by about 2+ meters of gray and red low-angle strata and channels to cap the sequence ( Fig. 12; dune foresets at base, rest as above; note iron seams in ...
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... intact 2-3 m dune bedform (a "form-set" with foreset, topset, and stoss beds preserved) is unusual at this scale ( Figs. 13-15; note the connected stoss & foresets just above 6' tape in Fig. 14). This form-set informs dune genesis: a medium ebb dune forms the base with directionally-opposed cross-strata aggrading vertically until one flow direction (100 o -apparent flood tides, downcurrent from the deltaic" sequence) prevailed about halfway up and coincident ...
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... intact 2-3 m dune bedform (a "form-set" with foreset, topset, and stoss beds preserved) is unusual at this scale ( Figs. 13-15; note the connected stoss & foresets just above 6' tape in Fig. 14). This form-set informs dune genesis: a medium ebb dune forms the base with directionally-opposed cross-strata aggrading vertically until one flow direction (100 o -apparent flood tides, downcurrent from the deltaic" sequence) prevailed about halfway up and coincident with a 15 cm dune (18 cm yellow ruler in Fig. 15- core"photo) which ...
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... foresets just above 6' tape in Fig. 14). This form-set informs dune genesis: a medium ebb dune forms the base with directionally-opposed cross-strata aggrading vertically until one flow direction (100 o -apparent flood tides, downcurrent from the deltaic" sequence) prevailed about halfway up and coincident with a 15 cm dune (18 cm yellow ruler in Fig. 15- core"photo) which formed the crest of the avalanche face at that point. The uppermost stoss beds are continuous with the topset beds; some topset beds (bedload sheets) flow continuously into foreset beds in places. A small dune is also present in the topset beds but most of its 15-20 cm thick strata appear horizontal in this ...
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... large foresets on large "simple" dunes suggest strong very asymmetric tides. Allen (1980,1982) depicted four general variants of "sandwaves" (what geologists now call "dunes" per Ashley, 1990) based on tidal current symmetry. Allen's conceptual "sandwave"/dune generated by the most asymmetric tides ( Fig. 16; large simple foresets in bottom frame; note the velocity asymmetry of U* critical, the threshold velocity to move sediment) conforms with the large dunes at LRC. Allen (1982) also depicted superimposed smaller dunes supplying sediment to the large foresets of a larger host dune. The "genesis" dune at the LRC dune field contains a ...
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... the threshold velocity to move sediment) conforms with the large dunes at LRC. Allen (1982) also depicted superimposed smaller dunes supplying sediment to the large foresets of a larger host dune. The "genesis" dune at the LRC dune field contains a small dune that appears to have "stalled" at the crest and reformed/"sharpened" it (center of Fig. 15; above 18 cm ruler); deposition continued along the aligned stoss and lee of both dunes (cf. Bridge and Demicco, 2008). Superimposed dunes pre-sort and transport sediment to and over large host dunes often in concert with bedload sheets. Pre-sorted wedges of sediment, as formed by smaller dunes ("trains") advancing over the crest ...
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... as oversteepened areas which slump in places and slide down the lee slope as long "tongues". A slight scour or channelelized grainflow may form which then "debouches" with a slight positive lobe at the basal portion of the foreset. Some foresets and "grain stripes" at LRC nicely display these subtle structures in dip cross-section ( Fig. 17) and the small granule "piles" on a dune backside noted above are interpreted as "grainflows" along the strike of dune ...
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... shown in Figures 13-15, a medium ebb-dune formed at the base and small competing dunes aggraded vertically (or slightly in the ebb direction) until the flood (shoreward) tides began to dominate about where the small dune is perched in the middle of the bed. With an abundant up-current sediment supply, the flood tidal current began to dominate and the ~ 2-3 m dune began to migrate. ...
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... final 2+ m of outcrop in the dune field contains robust channels and lateral-accretion w/some well- oxidized redbed deposits (Fig. 12) and some seaward-directed paleocurrents which are interpreted as fluvial meandering stream channels and point bars (Slingerland and Loule, 1988) noted a similar transition). This upper sequence appears to have shallowed upward probably from both lowered relative sea level (the beheading appears unique and the dunes never recovered) and ...
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... fairly thick beach sequence and a coarse shoreface have been suggested as indicators of significant tidal range/influence). Figure 18 is interpreted from the top (red lines ~ 3 m): Fluvial (deltaic?) channels/bars, foreshore (beach), foreshore (wave deposits). ...
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... foreshore (beach), foreshore (wave deposits). Figure 19 is interpreted as amalgamated shoreface deposits. Figure 20 is interpreted as mainly foreshore/beach deposits (all photos from outcrop #2). ...
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... Cross-bedded strata of various dimensions (~ 0.05 m to +1 m) commonly arranged in cosets, some bidirectional (Fig. ...
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... and point bar deposits are well exposed in places. Channel cross-sections are common at outcrops #4 and #5 as displayed on strike-joint (paleo-shore parallel) surfaces. The sense of flow direction is less clear but bi-directional cross-beds are present ( Fig. 21). At outcrop #2 and #6, some channels weather out and overhang dramatically with steep (> 45 o ) sides; some joint surface exposures are much less obvious. Developing criteria to distinguish tidal vs. distributary vs. fluvial channels would be useful especially for exposures on the western side of the hill yet to be ...

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