• The coarser varieties may represent viscous subaerial debris flows, locally reworked in the late flood stage by dilute tractional flows. The finer-grained varieties , consisting of very poorly sorted mixtures of sand, silt and clay, may have been generated by rapid deposition from mud-laden sheet-flows of short duration, or graphy with little erosion, or spilled out of channels and spread over relatively flat surfaces. The finely conglomeratic top was probably deposited from waning aqueous “tail” following the debris flow slurry.

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•Structureless or normally graded coarse to medium sandstone. Thickness averages 50 cm and ranges 6-160 cm. Normally graded varieties may grade upwards into finely sandy siltstone. The matrix of coarser varieties may contain a certain amount of silt. Clay chips locally present. Beds may be distinguished on the basis of geometry into sheet-like or lenticular, the latter with erosional base and planar top.

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•This facies may have been deposited by more or less concentrated sheet flows, lenticular geometries may reflect shallow scouring due to local turbulence

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•Probably deposited by supercritical flows. Iregular upper profile may reflect the tendency of flows to branch into very shallow channels separated by low bars in the late flood stage.

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•Subfacies may be due to migration of linguoid megaripples or dunes, probably not higher than 20 cm, and may either represent late tractional reworking by shallow channelled flows in the late flood stage at the expense of mass flow deposits in the relatively proximal areas of the fans, or the record of small, shallow, ephemeral braided river channels active in the distal fan. In most cases the smaller units may represent the record of migration of bedform trains during a single flood, whereas the large lenticular composite units, locally with mud drapes on the troughs, reflect a number of depositional events occurring in shallow, ephemeral channel.

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•Multi-channel bedload rivers :The cross-cutting channels forms represent a network of shallow broad channels cut in the early flood stage followed by infilling, essentially by vertical accretion, under supercritical flow conditions. The abundance of planar-laminated sands and the rarity of high-angle cross-lamination in the fills suggest high stage shallow flows, with little low-stage modification of bedforms. The facies association suggest the activity of an ephemeral braided river system, consisting of a network of shallow, interlacing, poorly defined channels.

•Local mud lenses indicate formation of temporary ponds within abandoned channel segments.

•This facies association may be considered typical of distal parts of major alluvial fans and mainly occurs in the Northern parts of the Dolomites.

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•Deeper fluvial channels, probably already represented trunk rivers.

•The rarely observed sets of planar cross-strata may represent deposition in transverse bars.

•The waning stage of flood flows is apparently recorded only by linguoid ripples migrating in the troughs of larger bedforms after crest emergence, mud drapes on floodstage bedforms, and mud lenses infilling abandoned channels. The latter were commonly removed by flood erosions as indicated by the abundance of mudstone clasts. The evidence for episodic flood-stage deposition followed by rapid withdrawel of floodwaters and subaerial emergence of bedforms with depositional of mud drapes strongly suggests flashy discharge conditions.

•The facies association may represent the record of flashy bedload fluvial system with a regime characterized by rapid variations in discharge, as suggested the virtual lack of late stage modification of flood-related bedforms. The scale of bedforms suggests relatively deep channels, perhaps due to the confining influence of paleovalley flanks.

•In the northwestern areas, where both facies associations are represented, the respective deposits occur in vertical succession with a clear trend fining upward, suggesting that they are the record of proximal and distal bedload fluvial systems. Paleocurrent directions in both are similar to those of overlying point bar sequences, but significantly diverge from paleocurrents of underlying alluvial fan facies associations, suggesting that sediment related to lateral influx were replaced by trunk river deposits.

• Val Gardena Sandstone:Alluvial fan facies Val Gardena Sandstone

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•Very poorly sorted and structureless sandy-gravelly red brown mudstone. Shows diamitic like textures, in which a variable amounts of granules and small pebbles, and rarely sparse sub angular to sub rounded pebbles or cobbles, float in a matrix of very poorly sorted mixture of sand, silt and clay. Bed thickness averages 100 cm and ranges 25-210 cm. Internal bedding and clast imbrication are lacking. Normal grading sometimes occurs in the coarser-grained varieties. Individual beds usually have flat, non-erosional basal contacts. Beds are locally capped by fine clast-supported conglomerates, either one clast thick or displaying a crude planar lamination in the finer grained varieties.

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•Planar laminated to low angle cross-bedded fine to coarse sandstone, sometimes with rows of granules.

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•Trough cross-bedded sandstone, gravely sandstone and fine-grained conglomerate. It commonly shows lenticular geometry and an erosional base. In most cases it consists of medium to coarse-grained sandstone, occasionally with sparse granules and small pebbles; trough cross-bedded conglomerates were only observed in section 18. Thickness of through cross-bedded units average 65 cm and ranges 20-180 cm. Set height is usually less than 20 cm. Isolated units typically occur as shallow lenticular bodies fining upwards from coarse to medium or fine sandstone, and usually encased within siltstone or sandy/gravely mudstone; they commonly occur as composite units consisting of a number of mutually erosive sets, locally with mud drapes on the troughs, associated in places with planar lamination. Liquefraction pockets are locally observed.

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•Multi-channel bedload rivers :Composite sandstone bodies resulting from stacking and cross-cutting of broad lenses 0.5-1.5 m thick with low relief erosional bases commonly floored by mudstone clasts. Broad lenses are associated with apparently unchannelized, planar-laminated intervals. Lithologies are coarse to microconglomeratic sandstone displaying planar lamination, low angle and possible antidune cross-lamination, locally with rows of small pebbles and or mud clasts. Major lenses, a few tens of metres wide with composite infill, may be identified as shallow channels, whereas small lenses are scour-and-fill structures, commonly consisting of low-angle cross-beds. These units are locally interbedded with mud lenses and are occasionally reworked at the top by small scour-and-fill structures or decimetre-scale trough cross bedding. No consistent vertical trends of grain size or physical structures occur.

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•Trough cross-bedded sandstones bodies, resulting from the lateral and vertical amalgamation of channel units, less commonly by isolated lenticular channelized units up to 3 m thickness, mostly represent the second facies association. The dominant structure is trough cross bedding, in sets up to 1 m thick, associated with planar low-angle lamination. Planar cross-stratification, notably rare, occurs within lenticular channelized bodies as isolated sets up to 2 m high, resting upon a limited thickness of trough cross-strata confined in the lowest part of the channel. Cosets of troughs are bounded at the base by erosion surfaces locally overlain by pebbles lag of extra-and intraformational material. A few trough cosets show a decrease in scale and grainsize upwards, grading into planar-laminated or rippled fine-grained sandstone and locally mudstone. The dominant lithology is medium to coarse sandstone, locally microconglomeratic, clay chips and pebble rows are common both in the planar-laminated facies and the base of trough cross-bedded sets. Mud veneers locally drape the foresets or troughs of cross-bedded sands, and impersistant mud lenses with locally abundant plant debris many separate adjacent cosets. The sand-mud contact is locally loaded. The erosional upper contact of mudstone lenses and the abundance of mud clasts suggest that the mud was originally more abundant than preserved amounts suggest. Linguoid ripples migrating in the troughs of cross-bedded sands at about right angles to the dip direction of the foresets of trough cross-bedded sands are locally observed.

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