Tidal amplification and along-strike process variability in a mixed-energy paralic system prograding onto a low accommodation shelf, Edgeøya, Svalbard

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Basin Research published by International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd 1Department of Geosciences, University of Oslo, Oslo, Norway 2Faculty of Geosciences, Universität Bremen, Bremen, Germany 3Department of Arctic Geology, UNIS— The University Centre in Svalbard, Longyearbyen, Norway 4NORCE Norwegian Research Centre AS, Bergen, Norway 5Geography and Geology Omaha, University of Nebraska Omaha, Omaha, NE, USA 6Dipartimento di Scienze della Terra, dell'Ambiente e delle Risorse (DiSTAR), Università degli Studi di Napoli Federico II Ringgold standard institution, Napoli, Italy 7Department of Geoscience and Petroleum, NTNU, Trondheim, Norway


| INTRODUCTION
The processes forming clinoforms at various scales and the distribution of sediment within these different systems are fundamental aspects of sedimentology (e.g. Anell & Midtkandal 2017;Bullimore, Henriksen, Liestøl, & Helland-Hansen, 2005;Helland-Hansen & Hampson, 2009;Patruno, Hampson, Jackson, & Dreyer, 2015;Pirmez, Pratson, & Steckler, 1998;Plink-Björklund, 2008;Steel & Olsen, 2002), much of which remains to be fully understood. The study of extensive outcrops provides comprehensive and detailed overview of the lateral and vertical changes in a depositional system, the scale and architecture of sandbodies and the overall temporal and spatial variability of sedimentary facies and depositional environments.
The Triassic sedimentary succession on the Northern Barents Shelf reflects the progressive infill of accommodation by a vast deltaic system advancing from the southeast (Anell, Braathen, & Olaussen, 2014a;Fleming et al., 2016;Glørstad-Clark, Birkeland, Nystuen, Faleide, & Midtkandal, 2011;Høy & Lundschien, 2011;Riis, Lundschien, Høy, Mørk, & Mørk, 2008). In the east, the North and South Barents Sea Basins subsided under kilometres-thick Triassic westward thinning deposits. Across the western platform depositional geometries are characterized by north-westward prograding clinoforms. Seismic data offshore highlight a 600-800-m high, prograding, sigmoidal shelf-prism scale set of Triassic clinoforms (C-C'+, Figure 1; Anell, Braathen, & Olaussen, 2014;Anell, Faleide, & Braathen, 2016;Anell, Lecomte, Braathen, & Buckley, 2016). As this north-westward advancing system approached Edgeøya, which formed part of the Triassic Svalbard Platform, the geometries of the seismic reflectors change towards wedging, very low-angle linear reflectors (B-B', Figure 1), revealing a marked change in depositional character. The shelf-prism system consists of seismic-scale clinoforms built by sediment supplied by smaller-scale deltaic systems which advanced and retreated over the topset area, periodically forming shelf-edge deltas discharging sediment directly to the slope (Johannessen & Steel, 2005;Plink-Björklund, Mellere, & Steel, 2001). Meanwhile the system approaching Edgeøya is of a similar scale to the largest deltaic sized clinoforms . It is inferred that the shallower setting prevented the formation of shelf-prism clinoforms, which were instead replaced by a large delta-scale equivalent. The study area on Edgeøya (Figure 1a), provides a stunning kilometres-long outcrop that is optimally located to better understand depositional processes in a prograding delta system and changes in the process-regime, sedimentary transport and deposition as it advanced across a shallower platform region. The study provides insight on the northern Barents Shelf, as well as broad implications for structural influence on fluvio-marine processes in analogue settings.
Our study addresses how changes in shallow marine processes impact a prograding succession of clinoforms, merging from shelf-prism to deltaic scale across a structural high. We furthermore use our interpretations to characterize the types and quality of sandstone bodies in terms of reservoir characterization and discuss the depositional environment of the system in relation to the regional development of the Barents Sea.

| GEOLOGICAL SETTING
The Barents Shelf consists of numerous sub-platforms, highs and basins that record a long and diverse geological history comprising several major orogenic events and extended periods of rifting (Anell, Faleide, et al., 2016;Anell, Lecomte, et al., 2016;Faleide et al., 2008, Faleide et al., 2008Gernigon et al., 2014;Henriksen et al., 2011;Johansen et al., 1993;Nøttvedt et al., 1993;Skogseid et al., 2000). At present the Shelf forms a shallow platform whose western edge constitutes the sheared rift-margin to the spreading North Atlantic, and a marked rifted transition to the north into the Eurasian Basin. The southern and eastern limits are comprised by the Scandinavian landmasses and the island of Novaya Zemlya respectively. The Svalbard archipelago lies in the northwest corner, and represents a tilted and uplifted part of the Barents Shelf. This exhumation generates a regional monocline from cleaner sands. This study provides important insight into tidal amplification and sand redistribution during shallowing on a wide shelf, along with along-strike processregime variability resulting from variations in sediment influx.
collected during four field-seasons (2012)(2013)(2014)(2015). Out of these, 16 logs were selected to provide the main basis for correlation and interpretation, based on their quality, location and length (Figures 4 and 5). Photogrammetric 3D virtual outcrop models were constructed using georeferenced digital photographs taken from a boat sailing ca. 1-2 km from the outcrop. The photographs were processed using © Agisoft photoscan to provide a high-density 3D point cloud, which was then triangulated to create a continuous, textured surface model ( Figure 6; Buckley, Howell, Enge, & Kurz, 2008;Hodgetts, 2013;Rittersbacher, Howell, & Buckley, 2014). Since the photographs were taken from sea level, their resolution becomes poorer further upsection. Meanwhile, resolution of details in the lowermost cliff-sections can observed features down to 20 cm size. The model altogether covers a section length of ca. 45 km around Kvalpynten, Vogelberget, Øhmanfjellet, Tjuvfjorsdskarvet and Svartpynten ( Figure 1a). However, poorer outcrop exposure makes it very difficult to discern much detail outside the western study area (Figure 1c,d). Thus, the work is focused on the details around Kvalpynten and Vogelberget (Figure 1a,b). LIME software (Buckley et al., 2019) was used for interpretation of the photogrammetric model ( Figure 6) to digitize lines and subdivide the succession, make measurements of length and height of units and sand-bodies, observe small and large-scale geological features, infer sequence stratigraphic development and measure bedding orientations. Due to the gentle inclination, measurements were not corrected for the tilt of the whole succession, which creates minor errors in the lowest dipping measurements. The observations and measurements from LIME were then combined with the sedimentary facies associations interpreted from logged sections.

F I G U R E 6
Examples of the expression of sand-bodies in photogrammetric model (for details see Table 3). The N-S section at the bottom shows the location of the displayed features. (a) A trough cross-stratified Channel (6 in Table 3) in Unit 3 (b) Stacked offsets of fluvial channels in the uppermost part of the cliff-face (Channels 9 and 10) and below a tidally dominated channel (4a) which can be followed along the whole section (Channels 4 a-c, Table 3) (c) Details of tidally dominated channel 4a showing a trough cross-stratified base fining upward into IHS. (d) Located in Kvalpynten E (around the corner from the section shown along the base) Sandbody 1 shows coarsening upward and displays clear lateral accretion surfaces accreting NNE dipping ca 8˚. (e) Sandbody 3 is a convex up massive sandstone with well-expressed dipping flanks dipping NE-SW. (f) A large section of the photogrammetric model which shows the extent of Channel 1 (with details of the point bar in the enlarged image) and Channel 2 which has a strongly erosional base and fines upward to a very muddy point bar which accretes towards the NW, details in the enlargement. The small enlargement to the right displays details of Unit 2 with the two coarsening upward units near the base and a thick mud-dominated succession in the middle of the Unit. (g) Channel 3 which is strongly erosional and displays large IHS dipping ca 12˚ accreting NW. (h) Inclined 1 (Inc 1, Table 3), located around the corner of the section displayed at the base, shows a stacked succession of prograding coarsening upward units similar to those seen at Vogelberget interpreted to display more classic mouth bars. The two units prograde W/SW

Grain size Interpretation
A Laminated (platy) mudstone Laminated to undulating dark grey to grey mud-to siltstone. These sediments are heavily altered at the outcrop and break-up as chips. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 5 Md-Si Deposition from suspended load within a low-energy environment, weak bottom currents may occur locally, as testified by the discrete undulations and rare thin ripple cross-laminations occurring within the mudstone B Sandstone with soft sediment deformation Very fine-to fine-grained dark-to light grey sandstone beds featuring a sharp to erosive lower boundary, and bounteous soft sediment deformations, including dish-, flame-and loading structures, convolute bedding and internal folding. Individual disturbed bed reaches a thickness of ca. 0.5-1.5 m, and occurs either as individual bed, or as amalgamated succession measuring up to 5 m VF-F Soft sediment deformations can occur when an applied stress exceeds the normal yield strength of the sediments or when this yield strength is brutally reduced, notably by liquidisation, and require to be coupled with a deviatoric stress impacting layers of contrasting density, often reflecting water escape and gravitational (slump) processes (Owen, 1987) C Hummocky and swaley cross-stratification Very fine-to upper-fine-grained dark-to light grey sandstone, characterized by a sharp erosive basal contact, and displaying hummocky and swaley cross-stratification, occurring as isolated bed or arranged in cosets, locally upward coarsening, which maximum thickness reaches 1 m, while extending laterally over tens of metres. Superimposed scattered unidirectional-current ripple cross-stratification may occur, as well as plant fragments. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and

3, including Skolithos and Rhizocorallium
VF-uF Hummocky-(HCS) and swaley (SCS) cross-stratification are generally interpreted to reflect a shallow marine storm-induced oscillatory current (Cheel & Leckie, 1993). Superimposed scattered unidirectional-current ripples illustrate the presence of a weak unidirectional flow from when HCS processes wane. HCS is thought to occur mainly near the Storm-Weather-Wave-Base (SWWB) while SCS represents a shallower depositional setting, between the SWWB and the Fair-Weather-Wave-Base (FWWB; Dumas & Arnott, 2006). Plant fragments indicate a proximal location of the deposits within the system D Low-angle crossstratified sandstone Upper-very fine-to upper-fine-grained dark-to light grey sandstone, with gently dipping cross-stratification, with a sharp to erosive lower boundary, and which amalgamated wedges reach a maximum thickness of 5 m and an exceptional thickness of 12.60 m within a growth section. Scattered oscillation ripple cross-stratification as well a plant fragments occur sporadically Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 3, including notably Skolithos uVF-uF Low-angle cross-stratification can occur in various depositional setting as transitional bedform between dunes and upper plane beds as flow velocity increases or as sediment concentration in the water increases (Massari, 1996), or between upper plane beds and HCS, as strong oscillatory currents wax (Dumas & Arnott, 2006;Quin, 2011). The presence of scattered oscillation ripples illustrates the impact of minor wave activity over the area. Plant fragments indicate a proximal position of the deposits within the system E Tangential crossstratified sandstone Upper-very fine-to medium-grained dark-to light grey sandstone, with a sharp to erosive basal contact, locally upward finning, individual cross-stratified sets measure between 0.5 and 1 m, and can reach a stacked thickness of 7.5 m. Scattered rip-up clasts, unidirectional-and oscillation ripple cross-stratifications, plant remains and mud drapes occur locally. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 3, including notably Skolithos uVF-M Tangential cross-stratification results from trains of mature 3-D dunes migrating on top of each other under non-laminar unidirectional current (Allen, et al., 1982, Venditti, Church, & Bennett, 2005. Their internal complexity (troughs and reactivation surfaces) reflects the degree of the bedform-crest-sinuosity, as well as the sub-to supracritical angle at which the bedforms are climbing, which can then be classified as compound-dune (Allen, et al., 1982). Note that migration of isolated 3-D dunes can also generate a tangential cross-stratification with tabular lower and upper boundaries. Plant remains indicate a proximal position of the deposits within the system, while mud drapes testify to the impact of tidal processes (Continues) 10 | EAGE ANELL Et AL.

Grain size Interpretation
F Unidirectional-current ripple cross-stratified sandstone Very fine-to fine-grained dark-to light grey sandstone, displaying unidirectional-current ripple cross-stratification, climbing ripples occurring locally, commonly observed in upward thinning succession from Facies E. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 2 VF-F Unidirectional-current ripples are the product of downstream migrating bedforms within unidirectional non-laminar flow conditions, representing for a given grain size, a lower energy level than the one generating Facies E or Facies H (Allen, et al., 1982). They can occur in a multitude of depositional environments (Allen, et al., 1982). Unidirectional-current ripples show the same maturity trend as they morph from straight-crested bedforms into 3-D ripples with the flow conditions (Venditti et al., 2005). Climbing ripples reflect a sedimentation rate exceeding the bedform progradation speed (Ashley, Southard, & Boothroyd, 1982) resulting in a positive aggradation G Oscillation ripple crossstratified sandstone Very fine-to fine-grained dark-to light grey sandstone, dominated by oscillation ripple cross-stratification, characterized by a sharp to gradual lower boundary. Occasionally displaying false herringbone cross lamination. Sporadically displaying mud drapes, unidentified burrows and rare wood fragments, it occurs as isolated dmthick beds, or in intervals up to 5 m in thickness, locally upward coarsening. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 2 VF-F Oscillation ripples are a product of the waves propagation and are generally interpreted as upper shoreface deposits, although similar deposits have been documented in non-marine environments (Allen, et al., 1982, Basilici, 1997 H Plane parallel-stratified sandstone Very fine-to medium-grained dark-to light grey sandstone, featuring plane parallel-lamination (PPL) and plane parallel stratification (PPS), with a commonly sharp lower boundary, and occasional gradual transition from the underlying strata, scattered plant fragments, oscillation-and unidirectional-current ripples occurring sporadically Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 2 VF-M PPS is a characteristic sedimentary expression of burst-and-sweep traction flows undergoing laminar upper-flow regime conditions, although PPS can still form at lower flow intensities when the sediment concentration in the water column is high, and occur within a range of depositional environments (Cheel & Middleton 1993, PickeringStow, Watson, & Hiscott, 1986, Ashley, et al., 1990, Massari, 1996, Fielding, 2006. Plant fragments indicate a proximal location of the deposits within the system I Structureless sandstone Structureless very fine-to medium-grained, dark-to light grey sandstone VF-M The lack of stratification within a homogeneous sandstone can be linked to a very rapid deposition from suspended load or it can be due to an extremely high degree of bioturbation (Gingras, Pemberton, & Smith, 2015) J Heterolithic mudto siltstone with lenticular bedding Very fine-to fine grained grey sandstone lenses within a laminated to undulating muddy to silty dark grey matrix, commonly found in upward coarsening intervals from Facies A into Facies J. The sandstone lenses are often characterized by uni-and bidirectionalcurrent ripple cross-stratification. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 4 Md-F Heterolithic deposits produced by a rapid flow deceleration and/ or expansion within a mixed mud-sand-rich environment (Baas et al., 2016). Bidirectional-current ripples suggest a certain degree of tidal reworking. High bioturbation index indicate a well-oxygenated and life-prone sea-floor (Taylor & Goldring, 1993) T A B L E 1 (Continued) (Continues) | 11 EAGE ANELL Et AL.

Grain size Interpretation
K Heterolithic silt-and sandstone with wavy bedding Very fine-to fine-grained dark-to light grey sandstone beds interbedded with laminated to undulated siltstone strata, commonly found in upward coarsening intervals from Facies I into Facies K. The sandstone beds are characterized by uni-and bidirectional-current ripple cross-stratification and scattered rip-up clasts, wood and bivalve shell fragments. Occasional thickening -thinning rhythmicity of the beds. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 5, but at maximum becomes cryptobioturbated Si-F Heterolithic deposits produced by a rapid flow deceleration and/ or expansion within a mixed mud-sand-rich environment (Baas et al., 2016). Bidirectional-current ripples suggest a certain degree of tidal reworking. Rhythmic thickening and thinning interpreted as a response to cyclic waxing-waning tidal current over the area, such as neap-spring tidal cycles (Visser, 1980). High bioturbation index indicate a well-oxygenated and life-prone sea-floor (Taylor & Goldring, 1993) L Heterolithic sandstone with flaser bedding Very fine-to fine-grained dark-to light grey sandstone, dominated by uni-and bidirectional-current ripple cross-stratification, commonly found in upward coarsening intervals from Facies J. Scattered mud lenses, mud drapes, rip-up clasts, wood and bivalve shell fragments. Occasional thickening -thinning rhythmicity of the beds. Bioturbation index (Taylor & Goldring, 1993) varies between 1 and 5, including Skolithos VF-F Heterolithic deposits likely produced by waxing-waning tidal currents (Baas et al., 2016;Sato et al., 2011). Rhythmic thickening and thinning interpreted as a response to cyclic waxing-waning tidal current over the area, such as neap-spring tidal cycles (Visser, 1980). High bioturbation index indicate a well-oxygenated and life-prone sea-floor (Taylor & Goldring, 1993) M Coquina bed Matrix-to grain-supported grey to white limestone beds, with horizontally-to chaotically oriented bivalve shell fragments reaching 3 cm in length. Bed thickness varies from 10 to 20 cm Fl-RdSt In situ coquina beds are often found in high-energy environments, in which siliciclastics are washed out of the system and shell fragments display a bedding-parallel preferred orrientation (Teyssen, 1984) or shell fragments can be transported and rapidly redeposited into a adjacent depocentre by storm-related events (ex situ coquina beds; Ávila et al., 2015) N Paleosol Yellow to rusty brown silt-to upper very fine-grained sandstone, reaching a thickness of ca. 10 cm, in which rhizoliths commonly occur. Gradual colour change occurrs both bellow and above paleosol horizons due to chemical diffusion reactions S-uVF In situ biogeochemically altered strata associated with paedogenesis and subaerial exposures (Kraus, 1999), potentially encapsulating a nonnegligible period of time in comparison with other neighbouring facies (Bown & Kraus, 1993). The limited vertical connection between the different paleosols suggest non-steady sedimentation rates occurring at the time of deposition over the study area (Kraus, 1999) O Coal-rich horizon Organic-rich intervals and coal seams, which thickness varies between 5 and 30 cm, containing abundant plant and wood fragments. Coal-rich horizons are found in the direct vicinity of paleosols (Facies M)

Md-Si
The genesis of coal and other coal-rich horizons require anoxic conditions within the shallow and sediments-starving column in order to preserve the organic matter, and often indicate swamp conditions; lacustrine coal also occurs (Miall, 2016) 12 | EAGE ANELL Et AL.
In the western study area B and C, the photogrammetric model is used to subdivide the succession into three main sedimentary units. The first unit is delineated by the separation of faulted from non-faulted deposits with a thick sandstone interval marking the top (Figures 1b and 3). The second unit encompasses a very characteristic thick shalerich succession capped by a sandstone interval. The final unit comprises the remaining exposures. This subdivision allows tentative correlation towards Øhmanfjellet, Tjuvfjordskarvet and the eastern study area, where a coarsening upward unit of similar thickness is overlain by a thick shale-rich interval of similar thickness to Unit 2. The units are labelled 1-3 and their bounding horizons are distinguished with colour coding (orange and green) throughout to simplify identification (Figure 1b-d). The logs at Schneiderberget and Naereingstuva could not be directly correlated to the other logs or the photogrammetric model.
The observed lithofacies in the study area are detailed in Table 1. Distinct facies associations are defined in Table 2.
Observations from the photogrammetric model are shown in Table 3. The succession is interpreted based on facies associations and observations from the model, and then further discussed with respect to the different units, covering variations across the study area and relationship to the regional infill of the Barents Shelf.

FA 1.1 -Shelf and distal pro-delta slope deposits
Description. FA 1.1 is composed mainly of laminated mudstone with low sand content, grading upwards into sets of heterolithic mud-and siltstone, with scattered rippled sandstone lenses. These sediments are interbedded with deformed sandstone beds and lenses with dish-, flameand loading structures (e.g. load casts, ball-and-pillow), convolute bedding and internal folding. Thin sandstone beds (ca. 2-20 cm) characterized by plane-parallel stratification (PPS) and asymmetric, unidirectional-current ripple crossstratification occur either as individual layers or grading from PPS. Bioturbation, including Taenidium and Helminthopsis, commonly occurs with local intensity variation between 1 and 4 (after Taylor & Goldring, 1993), and increases as the succession coarsens upward into structureless sandstone.
Interpretation. The occasional planar parallel sandstone beds in FA 1.1 are river-driven hyperpycnites (Bhattacharya & MacEachern, 2009;Petter & Steel, 2006). The dominance of laminated mud-and siltstone, which settled from suspension, coupled with hyperpycnites and/ or unidirectional-current ripple cross-stratified sandstone beds, and the lack of oscillation-driven deposits indicate an offshore setting below the storm weather wave base (SWWB; Bhattacharya, 2006). This is supported by the variety of soft sediment deformation within some of the current rippled and PPS sandstone beds, interpreted as gravity-driven mass wasting deposits driven by floods and/or sediment failures (Bhattacharya, 2006;Bhattacharya & MacEachern, 2009;Moslow & Pemberton, 1988;Owen, 1987).

FA 1.2 -Wave-dominated lower delta front/offshore transition
Description. Facies association 1.2 is characterized by the occurrence of isolated, folded and deformed sandstone beds as well as hummocky (HCS) and swaley (SCS) crossstratified beds in a heterolithic mud-and silt-dominated background with both lenticular-and wavy bedding. HCS is more common than SCS. A few centimetre thick sandstone beds with unidirectional-current ripples occur locally. Low-angle and tangential cross-stratified sandstone beds are increasingly abundant towards the top. FA 1.2 displays a characteristic upward-coarsening trend, as low-angle stratified sandstone beds become more abundant, thicker and more laterally extensive before grading into the overlying deposits of FA 2.

FA 2.1 Tidally dominated delta front
Description. Gradually transitioning from the underlying FA 1, FA 2.1 features 10-20 m thick upward-coarsening packages from mud-to sandstone heterolithic deposits, with low-angle and tangential cross-stratified beds with interbedded unidirectional-current-and oscillation ripples. Cross-stratified sandstone strata are locally arranged in tidal bundles, or in rhythmic sand-mud couplets (Figure 7a,c) | 13 EAGE ANELL Et AL. and flaser bedding in fine-dominated heterolithic deposits (Figures 8d and 9h). Both oblique and sigmoidal cross-strata occur, and evidence of bi-directional currents is commonly observed as well as reactivation surfaces (Figure 8d,f). The base of these cross-stratified sandstone bedsets and lenses can be either erosive or sharp, and locally displays loading and convolute structures. Coal fragments together with mud-drapes and rip-up clasts occur along foresets within cross-stratified sandstone bedsets. The bioturbation index (Taylor & Goldring, 1993) varies between 1 and 3, and includes Skolithos. Laterally the deposits become thinner, displaying an overall coarsening upward trend and increased bioturbation and unidirectional-current indications. In the photogrammetric model, FA 2.1 forms laterally extensive bodies covering the entire outcrop (>9 km). Towards the uppermost part the sandstones becomes erosive and well sorted with large-scale trough cross-stratification.
Interpretation. The upward-coarsening cross-stratified sandstones of FA 2.1 are interpreted to be a tidally dominated delta front associated with intense reworking of mouth-bar deposits. The strong tidal indicators which include sigmoidal cross-bedding, bi-directional cross-strata, reactivation surfaces, rhythmic lamination and bundling, compound cross-bedding, are all indicative of a shallow marine tidal environment (Allen & Honewood, 1984;Dalrymple, Knight, & Lambiase, 1978;Plint & Wadsworth, 2003;Rossi & Steel, 2016;Wei et al., 2016). Reworking favoured extensively amalgamated bodies compared to more isolated mouth bars (Rossi & Steel, 2016). The presence of symmetrical ripples indicates that the system was locally impacted by waves. An increased terrestrial and fresh water influence is corroborated by the rising sand-to-mud ratio in the system, the abundance of coal and plant fragments and low levels of ichnofabric diversity (Ahmed, Bhattacharya, Garza, & Li, 2014).

FA 2.2 Mouth bars
Description. FA 2.2 shares many traits with FA 2.1, but is less well sorted, contains larger amounts of organic material (Figure 3c,d) and is associated with more slumped beds (Figure 3f,h). The succession overall coarsens upward but includes metre thick fining upward tangential cross-stratified sandstones with rip-up clasts ( Figure 3g) and reactivation surfaces (Figure 4). Grainsize is typically very fine to fine. Asymmetric ripples are prevalent in the lower successions whereas symmetric ones frequently occur up-section. Climbing ripples also occur. At Tjuvfjordskarvet, stacks of inclined strata indicate a dominant progradational direction (Figure 6h). Bioturbation is scarce and confined to single beds. Paleocurrent data from current ripples indicate an overall SW-directed influx at Vogelberget.
Interpretation. FA 2.2 represents unconfined mouth bars accumulating beyond the river mouth. The high degree of organic material, soft sediment deformation, climbing ripples and current ripples and poorly sorted heterolithic accumulations are associated with strong river influence (Olariu & Bhattacharya, 2006;Olariu, Steel, & Petter, 2010;Rossi & Steel, 2016;Tye & Coleman, 1989). A sharp base with local loading structures, an absence of subaerial exposure indicators (e.g. mottling, paleosols), low-angle cross-stratification and dominantly laterally accreting sand bodies are some of the diagnostic features of rapidly accreting mouth-bar deposits (Ahmed et al., 2014;Martini & Sandrelli, 2015;Schomacker, Kjemperud, Nystuen, & Jahren, 2010). The heterolithic nature and occasional minor reworking of sedimentary material, wave-ripples and flaser bedding reflect variations in discharge. The fining upward packages within the succession represent minor distributary channels forming atop the mouth bars during periods of high discharge.

FA 2.3 -Storm-dominated delta front
Description. FA 2.3 consists of 6-8 m thick, sharp-based evenly thick or coarsening upward sandstone packages. They commonly include HCS and grade into undular, wavy or low-angle cross-stratification towards the top, with planeparallel tops in places ( Figure 5). The tops of these units are capped by mudstones. Organic material appears absent and bioturbation is often moderate but ranges from 1 to 4. FA 2.3 develops in the east study area, stratigraphically equivalent to the transition from FA 1 to FA 3 in the west study area where FA 2.1 dominates. Interpretation. The dominance of HCS indicates deposition below fair weather wave base where oscillatory flow, associated with storms, is the most common hydrodynamic mechanism (Cheel and Leckie, 1993;Dumas & Arnott, 2006;Peters & Loss, 2012 association with tidally reworked deposits of FA 2.1 suggests FA 2.3 was also modulated by tides. The overall observed higher degree of bioturbation suggests a lower energy setting compared to the west. FA 2.3 is therefore interpreted to represent a storm-wave-dominated, tidally modulated delta front.  (Figure 9a), plane-parallel laminated sandstones, short wave-length HCS (Figure 9c,e) and shell gravel. The bioturbation index (Taylor & Goldring, 1993) ranges between 1 and 5 and is commonly intense, completely obliterating original features. Recognized burrows notably include Skolithos and occasional Ophiomorpha (Figure 8b). FA 3.1 is differentiated from FA 4.1 by lacking continental indicators such as coal intervals or paleosols.

| FA 3 Subaqueous platform
Interpretation. The intensity of identified bioturbation indicates a marine environment and, given the strength of tidal indicators, dominated by tidal processes. The presence of lenticular and wavy bedding and extensive bioturbation indicates a relatively lower energy in comparison with the delta front. The subaqueous portion of a compound clinoform system (Kuehl, Levy, Moore, & Allison, 1997;Pirmez et al., 1998;Roberts & Sydow, 2003; Swenson, Paola, Pratson, Voller, & Murray, 2005) is the relatively flat and shallow area between the lower delta plain and the rollover of the delta front. The wealth of tidal indicators grading into the delta plain deposits indicates that this FA represents tidal flats (Baas, Best, & Peakall, 2016;Sato, Taniguchi, Takagawa, & Masuda, 2011). Sand-flats are characterized by current and wave-rippled, cross-laminated very fine and fine-grained sandstone, with common muddrapes (Desjardins, Buatois, & Mangano, 2012). Muddrapes along foresets of 3D migrating dunes also indicates a bimodal flow velocity system, characteristic of tidal currents (Visser, 1980). Unidirectional-current rippled beds commonly display loading and water-escape structures which imply a rapid deposition from overbank spills. Hence, they are directly linked to the proximity to distributary channels, with which they interfinger, testifying that these tidal flats developed in interdistributary areas (Elliott, 1974, Kurcinka, Dalrymple, & Gugliotta, 2018. Tidal flats commonly display a high degree of bioturbation (Desjardins, Buatois, & Mangano, 2012;Fan, 2011;Hughes, 2012;Mángano & Buatois, 2008). The appreciable wave influence is suggested by the presence of wave-ripples, short wave-length HCS (Figure 9c,e) and shell gravel indicative of storm events (Figure 9d,g) acting in open coast tidal flats. Such environments have been described from several locations around the world and represent an intermediate member between tidal and wave-dominated systems (Fan, 2011;Yang, Dalrymple, & Chun, 2005). However, unlike Edgeøya, open coast tidal flats often predominantly preserve wave-dominated successions which are only subtly different from true shorefaces, consequently open coast tidal flats might easily be misinterpreted in the rock record, and typically display strong seasonality (Yang et al., 2005).

FA 3.2 Tidal creeks and tidally dominated channels
Description. FA 3.2 consists of 5-10-m thick sandstone bodies with a lower erosive concave to flat boundary. The sandbodies occur in Unit 3 and are characterized by a fining upward trend and typically consist of multiple tabular layers around 5-20 cm thick with dominant cross-bed direction and sub-parallel beds in between ( Figure 5). They can also be characterized by tangential cross-strata, fining upward into heterolithic deposits, often with symmetrical ripples as seen in the west study area (Figures 3a and 4). The sandbodies typically display very limited bioturbation in the lowermost parts (BI 0-1). Asymmetrical ripples are common, particularly in their upper parts, where the BI ranges from 1 to 3. Plant and wood fragments commonly occur throughout FA 3.2. On the photogrammetric model inferred depositional equivalents to FA 3.2 are observed in the form of inclined heterolithic stratification (IHS; Figure 6g). Two such bodies about 30 m up into Unit 3 are both ca 1,500 m long, 25 and 17 m thick respectively with IHS dipping 8-14 degrees westnorthwest (Table 3 -Channel 2,3; Figure 6f,g). Another succession of IHS is observed ca 120 m up in Unit 3 which has a basal sandstone body exposed along almost the whole cliff-face (ca. 6 km), but it is dissected by present day valleys and thus measured as three units (Channel 4 a-c, Table 3, Figure 6b,c). The packages are ca. 15-m thick, fining upward from massive and trough cross-stratified sandstone into inclined heterolithic strata dipping 8-13° west, northwest and north respectively, northward along the cliff-face (Table  3). The channel cuts down into very black mudstone on the southernmost point of Kvalpynten.
Interpretation. The erosive lower contact and tidal and minor wave reworking, of these multi-story sand-bodies indicate a channelized environment within a marginal marine system (Ahmed et al., 2014;Olariu & Bhattacharya, 2006). The presence of tidal indicators, as well as the abundance of unidirectional-current ripples suggest a mixed zone of tidal and fluvial influence in the lowermost encountered channels (Olariu & Bhattacharya, 2006) which is supported by the low levels of ichnofabric diversity and limited degree of bioturbation. The presence of plant material, occasionally as coalified wood fragments, suggests many of these channels were connected to fluvial distributary channels. On the photogrammetric model the tidal channels are observed as large-scale IHS (Figure 6), which attests to a highly meandering network of channels, at times reworking almost the whole area. Tidal point bars are commonly characterized by inclined heterolithic stratification resulting from changes in hydrodynamic regime characteristic of tidal settings (Dalrymple & Choi, 2007;Hughes, 2012). Since the tidal prism increases seaward, tidal channels also increase in width (Dalrymple & Choi, 2007). The wider channels with higher discharge curve less so the sharper meanders are typically found closer to the shore and represent the site of lowest hydraulic energy between the fluvially and tidally dominated parts. Tidal channels thus tend to coalesce into massive deep straight channels in the distal delta front, which individually reach widths up to several kilometres (Cummings, Dalrymple, Choi, & Jin, 2015). Similarly, tidal channels and creeks, which dissect tidal flats, are usually small to medium in the muddy, upper inter-tidal zone, forming deeper and wider channels in the lower sandy areas (Dalrymple, 2010).
All the successions of IHS share comparable dimensions and direction, with meanders migrating more or less north. The upper IHS, however, has a basal cross-stratified unit likely representing a channel lag unlike the two lower units, which display only the inclined strata. This suggests that the upper unit formed in the proximal part of the fluvial-tidal transition as the coarse-grained fluvial input decreases seaward (Dalrymple & Choi, 2007). Two thick sandstone bodies about 100 m above the Unit 1 -Unit 2 transition found at Grindane 1 and Årdalsnuten 2 (Figure 4), are characterized by sharpbased bedsets in heterolithic FA 3.1 These comprise thick or stacked trough cross stratified bodies with rip-up clasts, current ripples and minor organic material. They do not share many traits with FA 3.2 but are interpreted to represent basal deposits of subaqueous tidal channels similar to that observed in the photogrammetric model.

FA 3.3 -Wave-built sand-bars
Description. FA 3.3 consists of coarsening upward intervals up to 10 m thick with metre-sized low-angle crossstratified, occasionally trough cross-stratified sandstones towards the top (Figures 4 and 5). FA 3.3 commonly occurs at the interface between FA 2.2 and the overlying deposits of FA 3.1, becoming progressively scarcer upsection where coarsening upward bodies are generally thoroughly bioturbated and sandstone beds thinner. Tidal indicators are rare, although occasional mud-drapes and double mud-drapes are found in the more heterolithic lower parts. Current indicators are common but the tops are often marked by wave-ripple surfaces, red coloured layers with occasional organic drapes (Figure 8e) and, in one instance, a conglomeratic lag ( Figure 5). Bioturbation is often moderate. On Kvalpynten FA 3.3 occurs within the same horizon as a number of sand-lenses seen in the photogrammetric model (Table 3, Figure 6d,e). These lenses are convex up, massive or coarsening upward, 6-12 m thick and around 700 m long. The flanks of the sand-bodies dip around 3-5˚ southwest and northeast respectively. Internal surfaces observed in one body show accretion towards the northeast. The logged intervals and convex bodies in the photogrammetric models are of similar thickness and occur over the same narrow interval in Unit 3. They are therefore assumed to represent the same feature and the interpretation is based on combining observations from log and model.
Interpretation. Multiple interpretations for these features can be considered. The coarsening upward trend, waveindicators and bioturbation establish a marine setting and the observed association, being located at the interface between FA 2 and FA 4, suggests that these sand-bodies formed atop the subaqueous platform in a largely unconfined setting. The occurrence of traction-flow related bedforms, as well as the dominance of fair weather oscillatory flow 22 | EAGE ANELL Et AL. over unidirectional-and storm-related oscillatory currents places these deposits within an upper shoreface depositional setting (Jackson et al., 2009;Moslow & Pemberton, 1988;Niedoroda et al., 1984). The occurrence of the FA at the offshore to delta plain transition suggests a very proximal near-shore location. The lack of soft sediment deformation, climbing ripples and plane-parallel deposits (Rossi & Steel, 2016) commonly related to mouth bars, suggests they are likely wave-built features. Persistent low-angle cross stratification within the units suggest wave action was the dominant mobilization agent prior to sediment storage. The sand-bodies dominantly display internal north-eastward accretion as well as overlap of bodies on northern flanks of other bodies, suggesting that the units accreted northward, away from the general westward (even south-westward) infill of the delta front. They could therefore have developed in a way similar to ancient berms composed of swash-overwash deposits characterized by mostly landward accreting lowangle cross-beds (Otvos, 2000), or as inter-tidal swash bars developed at the terminus of longshore transport systems (Hine, 1979). Atop the subaqueous platform of the tidally dominated Han River, swash bars are common features (Cummings et al., 2015). Subtidal shoals are another possible candidate given their convex up geometries (McIlroy, Flint, Howell, & Timms, 2008). FA 3.3 are thus under some debate but are interpreted to represent wave-built sand-bars.

FA 4.1 Delta plain with frequent marine incursions
Description. FA 4.1 is characterized by a heterolithic assemblage of laminated mudstone and isolated sandstone beds with tangential cross-stratification and unidirectionalcurrent ripples (Figures 4 and 5). The difference between FA 4.1 and the underlying FA 3.1 deposits is a scarcity of tidal indicators and the occurrence of coquina beds (rudstone) displaying chaotic bedding, paleosols and thin (5-20 cm) coal seams (Figure 10f-h,p). Reddish, well cemented carbonate layers with development of cone-in-cone structures occur at several locations (Figure 10c-e). Sandstones are generally thin, organic material prevalent and oscillation ripples are common. Bioturbation generally decreases compared to FA 3.1 but is locally intense (Figure 10b,n). Preserved sedimentary structures include low-angle crossstrata to distorted sub-parallel and tabular cross-laminated unidirectional-current rippled rocks.
Interpretation. FA 4.1 is interpreted to represent a lower delta plain succession. The presence of coal seams and paleosols in the succession indicates a continental setting on which anoxic marshes developed (Bown & Kraus, 1993;Kraus,1999, Miall, 2016. The interbedded occurrence of chaotically arranged ex situ coquina beds testifies of episodic storm events transporting shell fragments from the coast (Ávila et al., 2015;Teyssen, 1984). Marine incursions as well as overbank spills are expressed as tangential-and unidirectional-current ripples in cross-stratified sandstone beds and wave-ripples (Shen et al., 2015). The very thin coal seams (5-20 cm) and repetitive marine incursions suggest an extensive delta plain which was regularly flooded. and has developed as a lateral offset stack. The medium to coarse sandstones form the coarsest deposits encountered in the study area. They occur exclusively up-section in Unit 3 and are always associated with FA 3.1-4.1. Two upwardfining inclined successions occur just below the massive sand-bodies. The upward-fining successions consist of laterally accreting beds 6-12 m thick, poorly resolved but dipping around 5-10 degrees in an overall north-northwest direction.
Interpretation. FA 4.2 are fluvial channels given the lack of marine influence or reworking, along with predominance of terrestrial material and the close association with FA 4.1. The up-section scarcity of tide-related bedforms advocates for a prograding coastline accompanied by dominance of fluvial processes with time (Kurcinka et al., 2018). The northwardaccreting point bars observed below the fluvial channels indicate a continued westward-directed influx. faulted succession. Around Kvalpynten 100-135 m of vertical thickness is exposed and towards Vogelberget, where the Blanknuten Member outcrops, the full unit thickness of ca. 175 m is exposed (Figure 3). The lowermost section of the unit is characteristic of pro-deltaic deposits (FA 1.1) in an unrestricted, open marine environment, given the amount of mud, bivalve fragments and a full marine trace-fossil suite. Occasional gravity-driven event beds and storm beds represent the main delivery of sand (Figures 4 and 5).

|
The delta front is represented by three to five stacked upward-coarsening units (CUs), 25-60 m thick (Smyrak-Sikora et al., 2019; Figure 6). Characteristic for the CUs within the fault blocks in the western part of the study area is a strong tidal influence (FA 2.1) in the form of double mud-drapes, tidal bundling of strata and decimetre thick heterolithic lamination showing sand-mud couplets, reflecting neap-spring tidal cycles (Figures 5 and 7). Although not unequivocal tidal signatures, the wealth of indicators and occurrence of all three types support a dominance of tidal influence on the deposits (Dalrymple, 2010;Davis, 2010;Nio & Yang, 1991;Wei et al., 2016). The delta front is interpreted to have consisted of a laterally extensive and amalgamated compound dune field. The heterolithic deposits grade upward into coarser, cleaner compound trough cross-stratified sandstones with mud-chips and reactivation surfaces which, given the lack of terrestrial influx and often gradual transition, likely comprise smaller amalgamated 3D dunes. The smaller size and cleaner sands are interpreted to reflect increased tidal energy conditions and higher degree of reworking resulting from vertical restriction as accommodation was filled (Cummings, Arnott, & Hart, 2006).
Growth-faulting significantly controlled variations in accommodation in the succession likely favoured by rapid loading atop pro-delta muds (Ogata et al., 2018;Smyrak-Sikora et al., 2019). Deposition was then focused in the accommodation created, which trapped significant mudstone accumulations between isolated sandstones compared to more continuous deposition in un-faulted deposits nearshore ( Figure 6). The unit merges into a more uniformly heterolithic succession at Vogelberget where CUs are more discrete (Figures 3,4). The area around Vogelberget coincides with an increased fluvial influence and development of more characteristic mouth-bar deposits (FA 2.2). The fluvially dominated mouth bars form stacked CUs commonly displaying gently inclined heterolithic strata dipping 2-5° south-westward (Table  3, Figures 3d,6h). The base of the inclined strata appears undular and slightly erosive, cutting into muddy heterolithics in places, creating an angular unconformity between underlying and overlying beds. The uppermost CU is generally capped by an erosive, clean trough cross-stratified sandstone interval, the base of which could mark a maximum regressive surface. Mud-rich deposits dominate east of Vogelberget at Øhmanfjellet (Figure 3), and tidally reworked sandstones are akin to isolated dunes (Olariu, Steel, Dalrymple, & Gingras, 2012) indicating a dominantly interdistributary area. Towards the eastern study area the delta-front deposits show a higher degree of storm influence (FA 2.3, Figure 5).
The joint occurrence of mouth bars, storm-dominated and extensive tidally dominated deposits, reflects a delta front with spatially and temporally variable sediment input. Parts of the delta system were not redistributed by tides, possibly during periods of high sedimentary discharge. The mouth bars are poorly sorted and mud-rich compared to the redistributed sediment, which was reworked into better sorted, laterally amalgamated sandstones. Unit 1 shows a strong wave-dominance in the delta front (FA 2.3) toward east ( Figure 5). This difference is interpreted to reflect lower sedimentation rates in the east, favouring winnowing and washing over by storms. Lower sedimentation could also result in a narrower platform and thus less dampening of the waves, further enhancing their impact on the deposits (Choi, Dalrymple, Chun, & Kim, 2004;Cummings et al., 2015;Feldman & Demko, 2015).

| Unit 2
The dominance of shelf and distal pro-delta slope deposits in Unit 2 indicates a deepening relative to underlying deposits, and is interpreted to represent a transgressional interval with a maximum flooding surface placed within the thickest shale interval (Figures 4,5). The characteristic interval is applied as a regionally traceable marker (Anell, Faleide, et al., 2016;Anell, Lecomte, et al., 2016;Osmundsen et al., 2014). The lowermost sandstones form retrograding parasequence stacks which become thinner and finer up-section, preceding a ca. 10 m thick, almost completely shaley interval, occurring prior to renewed progradation. The unit is 37-48 m thick around Kvalpynten. It generally consists of one or two basal coarsening upward successions totalling ca. 10 m. In the north part of western Kvalpynten this lowermost part is relatively sand-rich, with the basal interval consisting of two coarsening upward cycles, each 4 m thick (Figure 6f). The lowermost of these sandstones pinches out towards the south, indicating continued southwest directed influx, as indicated by the dip of the underlying mouth bars (Table 3).
Renewed progradation mirrors the respective underlying deposits with a tidal compound dune field (FA 2.1) in the west and a storm-dominated delta front (FA 2.3) toward the east. However, the strong storm influence in the eastern study area is replaced by a stronger tidal signal in the lowermost transgressive beds (Figure 5), testifying tidal amplification during transgression (Boyd, Dalrymple, & Zaitlin, 1992;Dalrymple, 2011). The lack of well-developed 2D dunes in the west suggests that accommodation remained limited, favouring compound 3D dunes characterized by clean, erosive-based and reworked sandstones. A single subaqueous channel is preserved in Kvalpynten where a fining upward IHS succession dipping 10 degrees northward merges with a massive down-cutting sandstone unit, 480 m long and 23 m thick (Table 2, Figure 6f). The northward propagation of the point bars suggests that the sedimentary influx following transgression was directed more westward, in line with the paleocurrents measured in the uppermost units ( Figure 11).

| Unit 3
Unit 3 covers the uppermost part of the section and is variably exposed across the study area with a thickness of ca. 100-200 m. At Vogelberget Unit 3 is entirely eroded and reappears at Øhmanfjellet. A shale interval atop the uppermost sandstone in Unit 2 marks the base (Figures 1,6).
Unit 3 is interpreted to record the highstand passage of the delta front (FA 2) across the subtidal flat (FA 3) and onto the delta plain (FA 4;Figures 4,5,12,13). It forms an overall progradational package, characterized by the upward increase and thickness of delta plain deposits as typified by the log at Naeringstuva (Figure 5). A highly aggradational component is reflected in the stacked parasequences and the high occurrence of oscillation ripples in sandstones interbedded between root-casts and coal seams (Figure 10f,h,j,p), together with the typical organic-rich overbank deposits. The rapid changes between a subaerial peat mire and shallow subtidal environments reflect a widespread lower delta plain aggradation, with frequent marine incursions. A similar development is seen in the De Geerdalen Formation on Hopen  and in the tidally influenced Jurassic deposits offshore Norway (van Cappelle, Ravnås, Hampson, & Johnson, 2017).
In Unit 3, previous laterally homogenous deposits are replaced, along-and up-section, by a range of different types of sandstone bodies. This Unit marks the transition from the delta front to the delta plain settings through a subtidal flat (FA 3.1). The subtidal flat was dissected by tidal creeks and tidally dominated channels (FA 3.2), and occasionally isolated wave-build sand-bodies developed atop the flat (FA 3.3; Figure 12). This subtidal flat is typified by highly bioturbated, commonly cryptobioturbated, heterolithic tidal deposits. Sandy flats are typically intensely bioturbated due to the high infaunal biomass, low-energy, limited subaerial exposure and low sedimentation rates (Dashtgard, 2011;Desjardins et al., 2012;Fan, 2011;Gingras, Pemberton, Saunders, & Clifton, 1999). These sites are commonly located at some distance from the river mouths, where brackish water and high sedimentation rates result in low bioturbation F I G U R E 1 1 Paleocurrent measurements from four areas on Edgeøya. Note that the measurements from Svartpynten record ripple crests and thus the displayed results are bimodal and represent the orientation of the coastline. The display accentuates the dominance of a SW-directed infill for Unit 1 (Vogelberget), towards a more W-NW directed influx in Unit 3, which is corroborated by the photogrammetric analysis 26 | EAGE ANELL Et AL. (MacEachern & Bann, 2008). Alternatively, the high intensity of bioturbation observed in many sandstones could also attest to low sedimentation rates in a channelized environment with stable salinities, and may record the infill of abandoned tidal channels and creeks (Legler et al., 2014), given the association with FA 3.2.
The thick fining upward IHS intervals at several levels are interpreted as point bars of tidal channels, or, if directly connected to the fluvial system, tidally dominated channels given their likeness to studied tidal channels elsewhere ( Figure 12). The scale of the IHS at Kvalpynten (25 m thick/ 8-15° dip and 15 m thick/12,5° dip) indicates very large channels, similar in dimensions to those of the Han River Delta (15-40 m deep), where IHS of near identical dimensions have been observed (25 m dipping 14°; Choi et al., 2004;Cummings et al., 2015). The size at Kvalpynten also matches those of the Aptian McMurray Formation in Alberta Canada (25 m/8-12°; Martinius et al., 2017) and the Mid-Cenomanian Dunvegan Formation in the western Canada Foreland Basin (15 m; Plint & Wadsworth, 2003). The dimensions of the channels indicate they all formed in the subtidal zone. The extensive lateral accretion attests to a highly sinuous network of channels. The two IHS intervals around 30 m up in the Unit are strongly erosive, whereas the interval around 120 m is more laterally extensive with a less erosive base. Both share similar dimensions and orientation, dipping more or less north. The upper IHS, however, has a basal cross-stratified interval interpreted as a basal channel lag, unlike the two lower units, which contain only inclined strata, suggesting the upper part developed in the more proximal part of the fluvial-tidal transition (Dalrymple & Choi, 2007).
In the eastern study area sandstone beds with tabular cross-bedding formed in energy conditions near the lower boundary for 2D dunes, typical for the lower to upper point bar in low-energy sandy meandering rivers (Martinius & van F I G U R E 1 2 A depositional model for the formation of the De Geerdalen deposits on Edgeøya around the Carnian time period featuring a large prograding delta plain advancing NW and increasingly W across the Barents Shelf. The close-up shows a cartoon of the inferred depositional system with a tidally dominated compound dune field making up the delta front which is de-coupled from the coastline separated by an extensive subaqueous platform dissected by tidal channels. Mouth bars develop near the coast and further from the main influx the platform is narrower and becomes storm-dominated. The 2D cartoon cross-section A-A' at the base shows a simple schematic of an advancing clinoform succession with large prism-scale clinoforms becoming less steep and less high across the Svalbard Platform and tidal amplification moving more sand greater distances from the shoreline | 27 EAGE ANELL Et AL. den Berg, 2011). The eastern study area was probably dissected by a number of smaller creeks draining into the larger channels, such as those observed at Kvalpynten (Figure 6). The channel infill in the east study area changes from the strongly tidally influenced tabular cross-bedded fining upward units, to the massive trough cross-stratified sandstones incising the delta plain (Figure 10i-l), a development similar to that seen on Kvalpynten (Figure 10a). The channel sandbodies in both east and west are characterized by limited lateral accretion, with high depth-to-width ratios ( Table 3). The symmetric orientation displayed in a north-south section indicates a westerly infill. They most likely represent fluvial distributary channels draining vegetated areas (Figure 12). The coarsest sands are confined to the fluvial channels, which appear narrower and straighter than the tidal/tidally dominated channels (Table 3). A flood-dominated tidal prism could confine coarse sediment up-river as the tidal wave becomes channelized and amplified upstream (Goodbred & Saito, 2012). The size of channels interpreted to be of fluvial origin is very similar to fluvial channels found on Hopen, which is dominated by fluvial channels (Lord, Solvi, Klausen, & Mørk, 2014). Analysis of channels in the Snadd Formation reveals that proximal fluvial influenced channels reach up to 20 km width, decreasing to a few hundred metres in the distal delta plain (Klausen, Laursen, Ryseth, Gawthorpe, & Helland-Hansen, 2014). In light of this, observed features are interpreted as proximal fluvial channels which in turn connect to distal tidally dominated channels that widen across the subaqueous platform.
Sediment delivery is dominantly south-westward in the lowermost deposits of Unit 1 and 2, transitioning to more westward and north-westward in Unit 3 (Figure 11), in line with the general infill across Barents Shelf Anell, Faleide, et al., 2016;Anell, Lecomte, et al., 2016;Glørstad-Clark et al., 2011). This complexity likely results from local infill patterns along an articulated coastline, accentuated by the low-stand, which promoted development of embayments and connected subsystems (Bhattacharya, 2006;Osmundsen et al., 2014). An overall westward-directed transport in Unit 3 probably also reflects F I G U R E 1 3 A summary figure showing the main logs across the whole study area (a transparent map underlays the logs to guide in relative horizontal location) with the interpreted facies associations shown in thick coloured stacks on the left of each log. The shaded background colour shows the overall transition from pro-delta through delta front across the subaqueous platform and into the delta plain. The cartoon-drawings of some of the main sandbody types found at various locations and sketched into the figure to show a generalized development of the type of sandbodies 28 | EAGE ANELL Et AL.
a new sediment provenance with the influx of a Northern Uraloid Sand, observed in zircon analysis of the De Geerdalen Formation and interpreted to be sourced from Taimyr and Severnaya Zemlya (Fleming et al., 2016). However, input from a more northerly Triassic source cannot be ruled out.

| DISCUSSION
Spectacular cliff exposures on Edgeøya, East Svalbard, offer a unique possibility to study the evolution of a delta front related to regional-scale progradation. The succession studied records a regression followed by a transgression and maximum flooding and then renewed highstand progradation. The Carnian age and prominence of the maximum flooding surface (MFS) suggests it is probably the equivalent of the Intra Carnian MFS observed in the seismic data in the SW Barents Sea (Klausen, Ryseth, Helland-Hansen, Gawthorpe, & Laursen, 2015).
The deltaic clinoforms on the Barents Shelf have been interpreted to be de-coupled from the coast (Klausen et al., 2015;Rossi et al., 2019). In the study area on Edgeøya, all indications also point towards a de-coupled system, with a sandy subaqueous delta front dominated by compound dunes separated from the coastline by an extensive subaqueous platform, in turn comprising subtidal deposits and occasional wave-build sandbodies. Even without such indices the degree of tidal influence alone would promote rapid subaqueous progradation physically separated from the shoreline Plink-Björklund, 2012), with waves and tidal currents limiting accommodation in the near-shore areas, similar to the Fly, Changjiang, Ganges-Brahmaputra and Amazon deltas (Cummings et al., 2015;Hori, Saito, Zhao, & Wang, 2002). Tidal currents are efficient agents in transporting sand long distances away from the shoreline . Typically small-scale, 10-15 m high and partly subaerial clinoforms develop which are detached from larger 40-150 m subaqueous clinoforms, which tend to be long and gentle (Plink-Björklund, 2012). The subaqueous platform can extend for many kilometres in both width and length (Goodbred & Kuehl, 1999;Roberts & Sydow, 2003;Rossi & Steel, 2016;Swenson et al., 2005).
Wave-and tide-dominated depositional environments are often considered as two end-members, with the distinct sheltered heterolithic tidal flat succession in stark contrast to the exposed wave and storm generated deposits (Yang et al., 2005). Meanwhile it is apparent that complex interactions between wave, tide and fluvial processes over time and space can produce very variable deposits within a single system (Rossi & Steel, 2016). In the Havert Formation, one of the earliest prograding Triassic deposits on the southwest Barents Shelf, a mixed-energy influence on the deposits is appreciable with the tidal signature seen dominantly in nearshore proximal facies (Rossi et al., 2019). It has therefore been inferred that the tidal influence was not as strong as in, for example, the Jurassic deposits of the mid-Norwegian shelf (van Cappelle et al., 2017).
The deposits on Edgeøya show a high degree of tidal influence, but along depositional strike, contemporaneous fluvial-, wave-and tide-dominated deposits are observed in the delta front (Figures 12,13). This variability is interpreted to reflect changes in sediment influx, where the highest sedimentation rates led to preserved mouth bars, whereas tides generally redistributed sediment to form a compound dune field as seen in most of the western study area. The eastern study area is interpreted to reflect a setting more distant from the main fluvio-deltaic influx, which was subject to a higher degree of reworking by storms and waves (Fan, 2011;van Cappelle et al., 2017;Yang et al., 2005), common in tide-dominated systems (Morgan, 1970;Van Andel, 1967). Lower sediment influx also generates a narrower subaqueous platform and more limited dampening of the waves. The transgression, meanwhile, preserves more typical tidal sand-bodies also in the east, probably reflecting the classical tidal amplification associated with increased coastline complexity and formation of embayments (Boyd et al., 1992;Dalrymple, 2011). This is in stark contrast to the increased wave influence interpreted during back-stepping in the Early Carnian in the western Barents Shelf (Klausen, Ryseth, Helland-Hansen, & Gjelberg, 2016).
The subaqueous platform and lower delta plain record a largely tide-dominated setting with wave influence (Tw, Sensu Ainsworth, Vakarelov, & Nanson, 2011). These deposits are mud-rich and form another fine-grained depo-centre in addition to the pro-delta area (Plink-Björklund, 2012). When accommodation increases slowly, meandering tidal channels effectively rework the coastal area leaving no preserved tidal flat deposits (McIlroy et al., 2008). During more rapid accommodation generation, meander belts will be narrower with less tendency to amalgamate. The extensive preservation of subtidal flat deposits and isolated tidal channel bodies suggests a rapidly prograding system advancing across the Svalbard Platform. Rapid progradation across Svalbard during the late Triassic has previously been inferred to result from more limited accommodation, which promotes | 29 EAGE ANELL Et AL. accelerated progradation (Anell, Faleide, et al., 2016;Anell, Lecomte, et al., 2016).
The energy of the tidal wave increases where it is structurally constricted, either vertically or laterally (Cummings et al., 2006), which means that the highest tides are often found within restricted bays, funnels and embayments (Archer & Hubbard, 2003). Due to vertical confinement, the wider the shelf, the higher the tidal energy and therefore coastal systems >75 km wide, which included the Triassic coastline across the northern Barents Shelf, have a tendency to be tidally dominated (Ainsworth et al., 2011;Heap, Bryce, & Ryan, 2004;Klein & Ryer, 1978;Longhitano, Mellere, Steel, & Ainsworth, 2012;Redfield, 1958;Vakarelov, Ainsworth, & MacEachern, 2012). The wide subaqueous platform additionally attenuates wave action due to enhanced basal friction (Choi et al., 2004;Cummings et al., 2015;Feldman & Demko, 2015). Whereas tidal amplification is inherently complex (Archer & Hubbard, 2003;Cummings et al., 2006;Klein & Ryer, 1978; and dependant on several factors, it stands to reason that the increased degree of tidal influence apparent at Edgeøya compared to the SW Barents Shelf, is the effect of a shallower setting, whereby wave energy was attenuated, and tidal energy was further amplified. Amplification is suggested to have increased sand-transport away from the coast, thus explaining the increased sand content in shallow marine deposits compared to the offshore Snadd Formation. Both the Snadd and De Geerdalen formations are, however, characterized by very limited sediment bypass to a deep marine setting, despite being classified as supply-dominated (Carvajal, Steel, & Petter, 2009;Klausen et al., 2015). The shallow angle of the prograding system likely inhibited gravity-driven processes, a setting which was also further enhanced across the structural high ( Figure 12). The increased tidal influence and extensive preservation of tidal flat and tidal channel deposits suggest that the platform was elongated, and that across the structural high the distance between the subaqueous delta front and subaerial coastline increased.
The typical subdivision of deltas into wave-, tide-or fluvial-dominated is considered now to represent rather unique end-members of the system, and that many delta systems are actually affected by all three factors (Ainsworth et al., 2011;Bhattacharya, 2006;Olariu & Bhattacharya, 2006;Plink-Björklund, 2008;Rossi & Steel, 2016;Tanavsuu-Milkeviciene & Plink-Bjorklund, 2009;Vakarelov et al., 2012). Additionally the coexistence of wave and tide signals in a sedimentary system has been used to differentiate between regressive and transgressive cycles, since tidal amplification tends to occur when incised valleys are drowned (Legler et al., 2014). The interplay of tide and wave processes inferred at Edgeøya suggests deposition in a mesotidal to macrotidal setting. In macrotidal systems sediments are often organized in sandy bars in the shallow environment and compound dune fields in the deeper areas (Longhitano et al., 2012). On the other hand, in mesotidal settings wave influence is much stronger, with formation of sand barriers intersected by tidal inlets, and ebb and tide deltas. With increasing tidal range barrier islands decrease in size and degenerate into scattered sand bank islands beyond a certain threshold (Davis & Flemming, 1995;Flemming, 2012;Oost & De Boer, 1994), and the deposits on Edgeøya likely reflect such a threshold setting in which scattered wave-built sand-bodies occur near the coastline (Figure 12).

| CONCLUSIONS
The study provides insight into the depositional environment and sandbody distribution in the Triassic De Geerdalen Formation on Edgeøya, Svalbard, documenting the effects of mixed-energy and tidal influence during shallowing on a wide shelf, and the effects of underlying topography on clinoform development.
The increased degree of tidal influence apparent in the deposits on Edgeøya is inferred to result from amplification due to vertical constriction as the system prograded across a shallow platform. Further tidal amplification is also apparent within growth-faults where the tidal energy was structurally confined, and during transgression as a result of assumed increased coastline roughness and formation of embayments.
During passage onto the shallower Svalbard Platform, the development of shelf-prism (seismic) scale clinoforms was inhibited, and smaller-scale (delta-scale) intra-shelf clinoforms comprising a detached compound clinoform system developed. The tidal amplification resulted in larger amounts of sand being transported to the subaqueous delta front. Tidal redistribution largely reworked mouth-bar deposits, which are only occasionally preserved. Areas with lower sediment input were subjected to increased amount of wave reworking, an effect which was likely increased due to the narrower shelf and less dampening of waves. In areas of higher sedimention rates, an extensive lengthy subaqueous platform developed where waves were dampened and the vertical restriction further amplified the tidal signature. The preserved successions reflect highly bioturbated heterolithic tidal flat deposits. The platform was intersected by highly meandering tidal channels and smaller tidal creeks. The delta plain was incised by sand-rich, straighter and narrower fluvial distributary channels, with the tidal prism likely confining coarser deposits up-river.