• Val Gardena Sandstone:

•Alluvial fan facies Val Gardena Sandstone: Facies 4:The coarser units of this facies may represent the deposits of highly concentrated dispersion related to powerful sheet-floods with no approach to an organized system of banks, bars or channels, whereas the finer-grained units reflect the tractional reworking of mass-flows deposits during waning or fluctuating stages of a major flood, or the nuclei of low longitudinal bars within shallow distributaries, later modified in the falling stage limited lateral accretion or incision by minor channels. The finer grained varieties may have been emplaced by supercritical bedload flows, related to shallow, ephemeral, braided streams crossing the more distal areas of the fans. Outsize clasts may represent the coarser bed load abandoned as a result of loss of competence due to expansion of the flow at the transition point from the main channels of the fan to a network of very shallow, braided channels an low, longitudinal bars.

•Facies 5:This facies may have been deposited by more or less concentrated sheet flows, lenticular geometries may reflect shallow scouring due to local turbulence.

•Facies 6: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.This facies may reflect either late stage reworking of inner-fan mass-flow units by shallow braided river streams in the late flood stage, or deposition without outer-fan shallow ephemeral distributaries. The involved process may represent the development of avalanche faces at the margins of broad gravel sheets or low-amplitude longitudinal bars in the declining stage of flood events.

•Terminal fan facies :Rivers probably underwent a definite decrease in depth downstream and a sharp fall-off in their average discharge in the lower part of their courses, due to a number of factors including:

•A) Loss of water by evapo-transpiration and lower precipitation.

•B) Infiltration into a permeable alluvium.

•The rivers were probably exotic, and reduced to a network of low-gradient, shallow, ephemeral wadi distributaries plugged during repetive flash-flooding events and subject to frequent avulsions.

•Mouth bar.

•Bellerophron Formation:Coastal sabkha facies :Lagoon.

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• Val Gardena Sandstone:

•Alluvial fan facies Val Gardena Sandstone: Facies 4: Crudely to distinctly parallel stratified gravel and gravely sand. This facies ranges from clast-supported gravel, in which a crude stratification is shown by variations in clast size and concentration, to gravely sand in which an internal stratification is highlighted by the interbedding, on a centimetre or decimetre scale, of medium to coarse sandstone bands and rows of granules or pebbles and rarely cobbles, or less commonly by the alternation of fine gravel bands and pebble rows. Average thickness 55 cm, range 10-200 cm. Clasts in conglomerates may show a distinct imbrication and may be in mutual contact or supported by a sand matrix. Outside clasts in the pebblecobble size range and mudstone clasts locally occur. Grading is generally absent, but fining upwards trends have been observed.

•Facies 5: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.

•Facies 6:Planar laminated to low angle cross-bedded fine to coarse sandstone, sometimes with rows of granules. Isolated sets of planar cross-bedded sandstone or conglomerate. This is quite a rare facies, with thicknesses averaging 45 cm and ranging 10-100 cm. The sorting is quite good and the fabric moderately to strongly preferred. Grain size ranges from coarse sandstone to pebble conglomerate. The facies may occur at the top of or laterally to structureless or graded gravel units. Planar cross-bedded gravels are locally observed as single sets lateral to and erosively truncating planar-laminated gravel units.

•Terminal fan facies :Generally single-storey ribbons and sheet like composite channelized bodies, generally of mixed load type, showing on average an upward increasing reduction in thickness and river bedload content; these are encased in an increasingly overbank of sediments, leading to low channel interconnections. This evolution is typically absent or very poorly developed in the marginal parts of the basin and in the less subsiding areas characterized by reduced thickness of sedimentary succession. Simple single-storey ribbons range from 0.9 to 4.3 m in thickness. The sediments involved range coarse sands, locally bearing granules and small pebbles, to fine sands and mudstone. Channel fills exhibit a sharp, fairly incised, irregular erosional base, sometimes with a remarkedly stepped appearance, floored by mudstone clasts and sometimes-reworked calcrete nodules. Vertically accreted ribbons commonly display a crudely developed fining-upward textural sequence, with trough cross bedding of upward decreasing scale, locally accompanied by planar lamination; small ribbons of this type may have been deposited by single flood events. Other ribbons show an inclined heterolithic stratification suggesting limited lateral migration, with muddy members of the couplets usually reaching the base of the channel.

•Thick muddy intercalations, sometimes pedogenically modified, may occur in the lateral accretionary units indicating that the fill was highly episodic in some channels. Burrow networks are relatively common in the upper part of the channel fills.

•Internal scouring surfaces, in place floored by mudstone clasts, are quite common, and several stages of scour and fill are characteristic, especially in channelized bodies of the inner more proximal zone of the system, and suggests highly fluctuating hydrodynamic conditions.

•Sheet like sandstones, mostsly resulting from lateral and to a limited extend also vertical amalgation of ribbons and small-storey internal organization can be found.

•Channel fills are interbedded with a great variety of interchannel sand and silt units deposited during flooding. Splay sandstones and commonly form a volumetrical large proportion of the total sand framework, especially near the transition into inferred sabkha sediments and may extend far into the interchannel areas, reflecting the extremely flashy and ephemeral nature of the associated streams. Splay deposits include both sheet sand layers showing virtual non-erosional basal contacts with the underlying sediments, and more discontinous and lenticular beds with broadly erosional bases. Sheet sandstone layers partly appear to be wings tapering away from channel sandstone bodies and sometimes coalescing to form extensive sheet-splays. The may be rich in vegetal debris and show small-scale flood sequences. Wave ripples draped by mud laminae are also locally observed.

•The upper surface of some play sandstone layers show evidence of a local shallow scouring. Splay sandstones and associated mudstones in places show root traces and or invertebrate burrows and are occasionally interbedded with dolomite and gypsum layers. Horizons with mud cracks in the mudstones.

•Spaly sandstones may appear organized into thickening and coarsening-upward sequences 6-10 m thick, displaying a clear upward increase in the sand/mud ratio. These consists of basal mudstone intervals with sparse, thin, sandstone interbeds passing up into thicker-bedded sheet-sandstones and eventually single channel fills.

•Mouth bar :Small-scale upward thickening and coarsening sequences 3-6 m thick are generally observed at the transition from lagoonal/marine to continental facies associations. Muddy layers alternate with thin-bedded sandstones in the lower part, and progressively disseappear, to grade upwards into a amalgated package of sandstone layers generally displaying unidirectional structures such as ripple-drift cross-lamination, trough cross bedding and planar-lamination; the sequence may be capped by erosive based channel sandstones. The facies association is thought to represents small mouth-bars encroaching on a shallow-water basin.

•Bellerophron Formation:The Bellerophon Formation is charcterized by a complex array of facies and facies associations, all deposited in coastal to shallow shelf settings. The whole sedimentary body is typically zoned both laterally and vertically. Lateral zoning is highly by the eastward transition from thinner successions with marginal evaporites and repeated evidence of subaerial exposure into thicker successions characterized by fully marine facies associations and basinal evaporites.

•Vertical zoning is controlled by the overall transgressive trend affecting the VGS-Bellerophon Formation lithosome, and results in the VGS red beds grading upwards into a sulphate-evaporite/dolomite unit in turn overlain by a marine carbonate unit, usually very rich in fossils.

•A the whole succession is punctuated by a number of presumably third-order transgressive-regressive cycles ( depositional areas ), the vertical stacking of the facies associations does not actually follow a simple transgressive trend. Generally speaking, each depositional sequence records a more pronounced seaward shift of the entire system with respect to the underlying sequence.

•Coastal sabkha facies :The sabkha cycle consists of four main facies.

•A) Thin-bedded grey, fine-grained dolomite commonly with minor terrigenous content. Cm-thick dark grey to blackish peletic or marly interbeds generally occur. The depositional textures, partially obliterated by dolomitization, include: aphanitic dolomite and dolomitized wackestone with eurytopic microfossils, foraminifers, a few algae. In some cases microfossils have been replaced by gypsum. Macrofossils are quite rare. Environment: shallow subtidal setting, mud dominated lithologies suggest low hydrodynamic energy, while the poorly diversified faunas indicate some sort of ecological restriction.

•B) Bedded to massive grey to black marly-silty dolomite with displacive sulphate nodules; the microfacies recognized within the dolomite are mainly represented by former wackestone-packstone with skeletal components and silt- to sand-size terrigenous grains. The gypsum nodules range in size and abundance; they are typically displacive, deforming the surrounding sediment. Widespread bioturbation.

•C) Densely packed, layered, nodular gypsum, commonly with enterolithic folds, deriving from facies b through further increase in size and abundance of gypsum nodules; these begin the coalesce, but are still separated by significant amounts of marly dolomite.

•D) Chicken-wire gypsum: the dark mainly dolomitic partings between gypsum nodules are reduced to stylolitic undulate seams; the bulk of the rock consists of a mosaic of rounded to flattened cm-size sulphate nodules, commonly with compenetrating bouderies. The depositional environment of facies c en d is that of supratidal sabkha, where massive intrasediment growth of sulphate nodules occurs, continuously fed by solutions moving upward by capillarity from the water table through evaporative pumping. The whole facies sequence records progradation of the supratidal sabkha on the marginal lagoon setting.

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