Coastal Fans Research Articles

Facies analysis and paleoenvironmental reconstruction of Upper Cretaceous sequences in the eastern Para-Tethys Basin, NW Iran

Upper Cretaceous mixed carbonate-siliciclastic sequences are among the most important targets for hydrocarbon exploration in the Moghan area, located in the eastern Para-Tethys Basin. Despite of their significance, little is known about their facies characteristics and depositional environments. Detailed facies analysis and paleoenvironmental reconstruction of these sequences have been carried out in eight surface sections. Accordingly, four siliciclastic facies, eight carbonate facies and one volcanic facies have been recognized. Detailed facies descriptions and interpretations, together with the results of facies frequency analysis, standard facies models and Upper Cretaceous depositional models of Para-Tethys Basin, have been integrated and a non-rimmed carbonate platform is presented. This platform was affected by siliciclastic influx, in the form of coastal fan delta and submarine fans in the shallow- to deep-marine parts, respectively. This model is interpreted to be shallower in the central and northeastern parts of the Moghan area. Toward the southeast and southwest, this shallow platform turns into deep marine settings along steep slopes without remarkable marginal barriers.

Geo-archaeology of the Roman palaeosurface of Sena Gallica (Senigallia, Italy)

ABSTRACTSena Gallica (Senigallia), in the northern Marche region, was the first Roman colony on the Adriatic coast founded at the beginning of the third century BC. This research adopted an integrated approach to different information sources that combines old and new data, archaeological excavations, topographic and geophysical surveys, and geological and geomorphological analyses. The data are managed within a GIS and supported by 3D modelling. One of the results of this work is a map which represents the geomorphological setting of the Roman colony, close to the mouth of the Misa river. The settlement exploited the top-surface of the uppermost Pleistocene–early Holocene coastal fan of the Misa river, now only preserved at the apex sector truncated seaward by wave erosion. The top-surface of the fan apex, in turn, was partly re-incised by stream erosion producing a series of slight topographic mounds, which were selected for the earliest human settlement (V-IV c. BC). Some of the mounds resulted in a protected, slightly elevated, area enclosed by the meandering course of the Misa River and the Sant'Angelo/Penna streams, where the Romans decided to found their colony (284 BC). The tight interaction between human activities and the natural environment has always influenced the development of the town, from the earliest phases to the modern age. This map focuses on the time when the Roman colony was founded, but the combined study in progress allows understanding of the main transformations that occurred during the following centuries.

The formation and evolution of a coastal alluvial fan in eastern Taiwan caused by rainfall-induced landslides

The formation and evolution of a coastal fan in eastern Taiwan associated with a sequence of rainfall-induced landslides during the 2009–2013 period are explored in this study. The evolution of these landslides is mainly attributed to the head-cutting process initiated by Typhoon Parma in October 2009. During the attack of Typhoon Megi in October, 2010, a subaerial coastal fan with a surface slope of 8.9° was formed after the mobilization of the rainfall-induced landslides. The geomorphic features both in the steep gully and on the coastal fan were categorized as the sequence of granular debris flows and sheet floods. Severe fan toe erosion occurred thereafter due to the wind-wave forcing. Even if the variations of both the cumulative rainfalls and the drainage areas are one or two orders of magnitude among devastating fan-forming landslides worldwide, the mean annual precipitation and the basin ruggedness index (Melton ratio) are effective indicators to normalize the rainfall threshold and to characterize the fan surface slope, respectively. Severe catastrophic landslides generally occur when the normalized cumulative rainfalls with respect to mean annual precipitation are greater than 0.1. The fan slope generally increases with the increasing Melton ratio for the catchment. Uchiogi’s empirical model is applicable for predicting the rainfall-induced area ratio of newly generated landslides. In this case study, the relationship of the fan area to the total landslide area follows a linear regressive curve when the ratio of landslide area with respect to the drainage area exceeds 0.0056.

Sedimentology and stratigraphy of Cenozoic deposits in the Kağızman-Tuzluca Basin, northeastern Turkey

The Kagizman-Tuzluca Basin is located in the northeastern Anatolia, to the east of the intersection point (near Karliova) of the major North and East Anatolian Fault systems. This intermontane basin displays a thick sequence (over 2000 m) of mostly terrestrial deposits represented by repetitive alternations of the lake and fluvial environments ranging from ?Late Eocene/Oligocene to Middle/? Late Miocene. A marine incursion only mappable in the southeastern margin of the basin deposited limestones and sandy limestones rich in marine mollusks and nummulites, in particular N. fichteli that constrain an Early Oligocene age for this marine unit (Kagan Fm). The terrestrial basin-fill deposits show different thicknesses throughout the basin due to irregular bottom topography and tectonic configuration of the basin margins. The thickest deposits were accumulated along the different margins of the basin, which received high quantities of siliciclastics from meandering river, alluvial and coastal fans, fan delta/Gilbert-type delta and wave-worked fluvial delta. Climate changes have also driven the development of lake environments during distinct depositional periods. Siliciclastic-dominated overfilled lakes (Halikislak and Kizilkaya formations) and chemical-dominated underfilled lakes (Turabi and Tuzluca formations) were formed. They have been also classified as “Newark-type” and “Fundy-type” lakes, respectively. Fluvial systems evolved from high-energy meandering rivers deposited under humid climate (Gungoren Formation) to low-energy meandering rivers resulted from arid and semiarid climates (Cincavat Formation). The transitional intervals from ephemeral river-dry mudflat (Cincavat Formation) to saline pan/lake (Tuzluca Formation) indicate wadi-sand flat-playa fluvial systems. The chronostratigraphic constrains of the entire sequence remain poor and so far solely based on vertebrate fossil assemblages. The evaporitic Tuzluca Formation would be Middle Miocene in age due to its stratigraphic position over the Cincavat Formation.

Geomorphological response of fluvial and coastal terraces to Quaternary tectonics and climate as revealed by geostatistical topographic analysis

Geostatistical topographic analysis is widely recognized as a useful tool for the statistical reconstruction of planar geomorphic markers from relict surfaces. This work is aimed at improving the geostatistical approach used in previous works and developing a method for evaluating the incision rates of rivers in their lower catchments during the Late Quaternary. We chose the major valleys of the Adriatic foothills (central Italy), affected since Late Miocene by a differential tectonic uplift which is still active. In particular, (i) we applied the geostatistical analysis to reconstruct the original top-surfaces of fluvial-to-coastal terrace bodies at the Metauro River and Cesano River mouths; (ii) we performed correlations between the height distribution of the alluvial terrace sequences and the Quaternary climatic curve to estimate the average long-term fluvial incision rates in the lowermost reaches of the Metauro, Cesano, Misa and Esino Rivers. The obtained averaged incision rates have been interpreted also in the light of the Stream-Length Gradient Index (SL Index), Steepness Index (Ks), and Concavity Index (θ) as proxies of the stream-power per unit length. Results confirm that geostatistical and terrain analysis of topographic and geometric arrangements of fluvial and coastal terraces is an effective tool in detecting geomorphic and tectonic factors inducing perturbations on planar geomorphic markers. In particular, we better delineated the surface geometry and boundaries of well-developed coastal fans at the mouths of the Metauro and Cesano Rivers, already recognized in previous works through sedimentological, morphostratigraphic, and chronological data. Moreover, we found evidence for cut-and-fill phases that took place during and immediately after the river aggradation of the late Quaternary glacial periods. Despite the Slope–Area analysis evidenced a widespread influence of the regional differential uplift on single river basin configuration, we observed some space and time variability of averaged incision rates for adjacent valleys, mainly explained by physiographic configuration and dynamics of drainage network. Copyright © 2011 John Wiley & Sons, Ltd.

Recurrent Submergence and Uplift in the Area of Ancient Helike, Gulf of Corinth, Greece: Microfaunal and Archaeological Evidence

In 2001, Helike Project archaeologists found traces of the coastal site of Classical Helike, a city destroyed and submerged by an earthquake and tsunami in 373 BC. Nearby they also found remains of its prehistoric predecessor, an Early Bronze Age (EBA) settlement dating from ca. 2500–2300 BC. Both sites are on land, 3 to 5 m below the surface of a coastal fan delta southeast of Aigion, on the Gulf of Corinth in Greece. To investigate the environmental history of the delta and the ancient sites, we analyzed microfossils, mainly ostracods and foraminifers, in sediments from boreholes and archaeological trenches. Although the area is now dry land, microfossil assemblages indicate ancient coastal aquatic environments over a wide range of salinity at the time and place of sediment deposition. The EBA site is covered by clay and sandy clay containing freshwater, brackish, and marine microfossils. The Classical site is covered by silty sand and silty clay containing mostly freshwater and brackish microfossils. The EBA site was apparently submerged in a coastal lagoon, perhaps due to an earthquake. The site was subsequently silted over and uplifted. Some two thousand years after the EBA destruction, the historical earthquake and tsunami destroyed Classical Helike and submerged its ruins in a lagoon. Continued uplift and sedimentation then led to the emergence of the present delta. The occurrence of severely abraded or fragmented shells of marine and brackish microfossils in a broad stratum of possible Classical age suggests the action of a tsunami.

Climatic controls on alluvial-fan activity, Coastal Cordillera, northern Chile

Abstract A description of the distribution, drainage basin characteristics, surface morphology, depositional process and age of 64 alluvial fan systems from both flanks of the hyper-arid Coastal Cordillera of northern Chile between 22°15′S and 23°40′S is presented. The coastal fans on the western flank of the Coastal Cordillera are dominated by debris-flow deposits fed from steep catchments. Two drainage basin types are recognized: type A drainage basins are small (10–30 km 2 ) and do not cut back beyond the main coastal watershed; and type B drainage basins are large (up to 400 km 2 ) and cut inland beyond the coastal watershed. The western Central Depression fans on the eastern flank of the Coastal Cordillera are characterized by sheetflood deposition fed from relatively shallow catchments in small drainage basins (10–50 km 2 ). The surface morphology, sedimentation rates, a luminescence date and regional cosmogenic radionucleide data suggest that these fans have been inactive for at least the last 230 000 years and probably for much of the Neogene. The principal control on fan activity in the study area is climate. The Coastal Cordillera forms an orographic barrier to recent El Niño-related precipitation events that are restricted to the western flank of the Coastal Cordillera. These events did not penetrate into the Central Depression as indicated by the inactive nature of the western Central Depression fans located 25 km east of the active coastal-fan catchments. This scenario is considered to have prevailed for much of the Neogene. Climate also controls rates of weathering on alluvial-fan surfaces. The coastal fog results in rapid salt weathering of clasts on coastal fans resulting in the production of fines, but does not penetrate into the Central Depression. Fault activity is important in controlling drainage basin size. The larger (type B) drainage basins are commonly focused on active faults that cut the coastal watershed, facilitating drainage basin expansion. Source-area lithology is not important in controlling depositional processes. Fans on both sides of the cordillera have the same basaltic andesite and granodiorite source lithologies, yet coastal fans are dominated by debris-flow and western Central Depression fans by sheetflood deposition. A combination of chemical weathering and stream power related to gradient are considered to account for the differences in process.

Deposits from dome-collapse and fountain-collapse pyroclastic flows at Soufrière Hills Volcano, Montserrat

abstract Pyroclastic flows were formed at Soufrière Hills Volcano by lava-dome collapse and by fountain collapse associated with Vulcanian explosions. Major episodes of dome collapse, lasting tens of minutes to a few hours, followed escalating patterns of progressively larger flows with longer runouts. Block-and-ash flow deposit volumes range from <0.1 to 25 x 10 6 m 3 with runouts of 1-7 km. The flows formed coarse-grained block-and-ash flow deposits, with associated fine-grained pyroclastic surge deposits and ashfall deposits. Small flows commonly formed lobate channelized deposits. Large block-and-ash flows in unconfined areas produced sheet-like deposits with tapering margins. the development of pyroclastic surges was variable depending on topography and dome pore pressure. Pyroclastic surge deposits commonly had a lower layer poor in fine ash that was formed at the current front and an upper layer rich in fine ash. Block-and-ash flows were erosive, producing striated and scoured bedrock surfaces and forming channels, many metres deep, in earlier deposits. Abundant accidental material was incorporated. Pyroclastic flow deposits formed by fountain collapse were pumiceous, with narrow sinuous, lobate morphologies and well developed levees and snouts. Two coastal fans formed where pyroclastic flows entered the sea. Their seaward extent was limited by a submarine slope break.

Quaternary environmental change in Cyrenaica evidenced by U-Th, ESR and OSL dating of coastal alluvial fan sequences

AbstractThe coastal alluvial fan sequences of Cyrenaica are important archives of environmental change data, but hitherto relatively little has been known about their formative processes and rates. The Wadi Zewana coastal fan near Tolmeita was studied and a range of dating techniques (U-Th, ESR and OSL) applied to selected components of the stratigraphy. The sequence spans the last two global glacial periods separated by an Interglacial. Cemented alluvial fan gravel units yielded U-Th leachate-residue ages of 201 ± 18 ka, 179 ± 15 ka and 138 ± 8 ka respectively. The fan toe units are interdigitated with bioclastic beach rock deposits dated to 150 ± 10.9 ka corresponding to an Interglacial high stand in sea level and marine recession sequence featuring transgressive lag gravels, beach sand and cemented aeolian dunes dated to 121 ± 8 ka. Within the Wadi Zewana catchment a complex cut and fill history is evidenced. Aggradation phases dated to 76 ± 4 ka, 42.1 ± 5.1 ka and 12.5 ± 1.5 ka are broadly coincident with global glacials and stadials, whilst during the Last Interglacial and successive interstadials the drainage system underwent entrenchment, manifested on the coastal plain as telescopic fan segmentation and associated fan head trenching.

Combining AIRSAR data of Huon peninsula and Hawaii MR1 data of Huon Gulf, Papua New Guinea, for studies of tectonic and sedimentary processes

Two swaths of airborne synthetic aperture radar (AIRSAR) imagery, acquired over the southern Huon Peninsula, Papua New Guinea, have been digitally merged with aerial photogrammetric topography and with Hawaii MR] acoustic side‐scan imagery and bathymetry of the adjacent seabed of Huon Gulf. This example of land‐sea integration provides a means of examining relationships between tectonic lineaments and sediment transport pathways on land and on the subjacent seabed. Imaging methods and geometries dictate both the regions covered and the information content of the data. The principal limitations in merging the two data sets arise because the coastal and inner shelf zone, in water depths less than 500 m, is inaccessible to the imaging techniques that were used. Indirect methods allow some inferences to be made about the geomorphology of this zone, using surface sound channel data and sea surface imagery. The area examined is part of an active tectonic collision zone in which the northern margin of the Australian plate is being subducted beneath the South Bismarck plate. The edge of the South Bismarck plate has been uplifted 4,000 m since the late Pliocene, forming the Finisterre Range on Huon Peninsula. The record of relative emergence and submergence is seen in subaerially exposed Quaternary marine sediments and in drowned carbonate reefs. The merged radar and sonar imagery clearly indicate rapid erosion and deformation, both on land and under water. The imagery shows details of sediment transport and depositional systems, which are generating large terrestrial fluvial/alluvial plains, coastal fan deltas, and submarine channel deposystems. Fault structures and outcrops of bedrock units are clearly delineated both on land and on the seabed. These observations help explain patterns of onshore and submarine outcrops in terms of interactions between modern offshore sedimentation patterns and progressive deformation.

Evolution of Lower Jurassic coastal plain and fan delta sediments in the Beryl Embayment, North Sea

Coastal plain and fan delta sediments accumulated throughout the Sinemurian to late Pliensbachian in the Beryl Embayment area, North Sea. These sediments represent a marginal, clastic fringe along the southern extension of the Boreal Ocean into the northern North Sea. Two informal formations are recognized in these predominantly sandy deposits. The lower formation comprises interbedded sandstones, siltstones and coals of minor fluvial channel and associated coastal floodbasin marsh, lake and sheetflood origin. The overlying formation represents a fan delta system, possibly generated as a result of footwall uplift and associated erosion. This formation is dominated by probable channel sandstones, with marine-influenced debris flow deposits developed at a number of levels indicating an active, coastal fan setting. Fan sediments are capped by a marine sandstone, beds of which interfinger with the overlying offshore siltstones. Thickness variations are related to major normal faults, suggesting at least a limited fault control on the deposition and distribution of facies during a time conventionally regarded as tectonically quiescent in the northern North Sea. There is no clear evidence for a eustatic control on sedimentation, although deposition of post-fan delta shallow marine siltstones may have been principally controlled by eustatic sea level rise recording the acme of the early Jurassic expansion of Boreal waters into the Viking Graben.

An Illustration of a Sea Level Control Model from a Subsiding Coastal Fan System: Pleistocene Ogasayama Formation, Central Japan

The sea level control model is a framework to explain coastal alluvial fan processes controlled by relative sea level changes and the resulting stratigraphic sequences. The model generally predicts three types of stratigraphic units, namely: (1) open fan deposits with tripartite organization for each relative sea level rise beyond the previous high stand, and subsequent sea level fall (A-type); (2) fan valley fill deposits, constructed during sea level rise up to the previous high stand (B-type); and (3) dissection-fill deposits consisting predominantly of overflow deposits (C-type). Combination of the model with a eustatic fluctuation curve suggested from an oxygen isotope record, modified for tectonic subsidence, allows a semi-quantitative estimation of numbers and dimensions of respective stratigraphic units. Estimations for the time interval recorded by the Ogasayama Formation, which shows all the depositional units predicted by the model, compare favorably with the field observations. Thicknesses predicted are directly related to the suggested amounts of relative sea level changes, which are mostly around for all types of stratigraphic units. The average recurrence period for A-type bodies is and for B-type bodies , time intervals generally assumed to be in the order of eustatic sea level fluctuations. The general agreement between model and observations in terms of both stratigraphic architecture and semi-quantitative analysis illustrates the direct control of relative sea level fluctuations on the construction of coastal fan deposits. Alternate occurrences of humid and dry climatic conditions associated with the eustatic cycle may be responsible for progradation of Gilbert-type deltas within the fan valleys, which show finer grain size than the coarsest open fan deposits.

Fan-Delta and Interdeltaic Shoreline Sediments of Middle Devonian Granite Wash and Keg River Clastics, Red Earth Field, North Alberta Basin, Canada: ABSTRACT

A detailed sedimentological investigation of over 4000 ft of core and 500 well logs of the Middle Devonian granite wash and Keg River clastics in the Red Earth field, North Alberta basin, Canada, has led to the recognition of a granite wash subaerial fan-delta system that is laterally continuous with a Keg River subaqueous delta component along an eastern shoreline of the ancestral Peace River arch. The subaerial fan delta includes alluvial fan facies, sheet wash and mud flows, and playa lakes. The subaqueous delta component includes lower shoreface, upper shoreface, beach-foreshore, eolian sand dunes, lagoon, washover sands, tidal channels and flats, and supratidal carbonates and anhydrites. Within this system, six mappable units are defined. A conceptual depositional model for the sequence depicts four main events. (1) Erosion of Peach River arch uplifted fault blocks, which produced coarse-grained fan-delta sediments in an adjacent fault-bounded margin. Subsequent fluvial reworking resulted in the deposition of thick, lenticular, wedge-shaped alluvial fans of granite wash. (2) Progradation of alluvial fans seaward into the Keg River Sea. (3) Transgression by Middle Devonian seas from the east, which reworked alluvial fans and led to deposition of discontinuous linear sand bodies represented by the Keg River regressivemore » shoreline sediments. (4) Restriction of the sea by the Presqu'ile barrier reef to the north, which deposited evaporites of the Muskeg Formation over the whole sequence. Modern analog to this fan-delta system is the coastal fans of the Gulf of Aqaba, Red Sea. Red Earth field contains over 27 million bbl of recoverable oil, related to a combination structural-stratigraphic trap.« less

Neogene coralline-algal growth-forms and their palaeoenvironments in the Almanzora river valley (Almeria, S.E. Spain)

The Almanzora river valley is an elongate E-W depression containing mainly Neogene sediments. During the Late Tortonian several horizons of crustose coralline algae developed in three distinct sedimentary contexts: (a) on coastal platforms and talus slopes, (b) on fan deltas and (c) associated with corals in patch-reefs growing at the furthermost extremes of coastal fan deltas. In the former two cases the predominant growths are as rhodoliths associated with mobile substrates. In the coastal systems an increase in depth results in a change in both the morphology and the composition of the rhodoliths. With depth there is a significant increase in the diversity of algal species and a concomitant increase in the size of the algal covering compared to the nucleus and thus the morphology of the rhodolith depends less and less on the shape of the nucleus itself. The massive crusts and columns, which mark the limit of development of the shallow-water rhodoliths, in the deeper examples are covered by branching and thin, leafy (laminar) growths. In the fan deltas the development of the rhodoliths is similar to that of the deeper coastal zones. In the patch-reefs the specific composition of the algal associations changes somewhat and the growths, developed on a stable substrate under low-energy conditions, are mainly vertical branches arising from thin crusts.

Coastal Fan Processes Controlled by Sea Level Changes: A Quaternary Example from the Tenryugawa Fan System, Pacific Coast of Central Japan

A new hypothesis for dynamic processes in coastal fans is presented, based on the concepts of temporal changes in morphology and associated sediment bodies in phased and cyclic mode. These changes, which are marked by overflows from a fan valley before its complete burial as well as after the initiation of its entrenchment, are entirely related to relative sea level changes. The hypothesis is exemplified by the Middle Pleistocene to Holocene Tenryugawa system, Pacific coast of central Japan.

K-Ar Ages Confirm Pliocene Age for Oldest Neogene Marine Strata near Loreto, Baja California Sur, Mexico: ABSTRACT

Beds of pumiceous tuff interbedded with mollusk-rich sedimentary rocks provide new age constraints on the timing of the late Neogene subsidence and marine transgression a few kilometers north of Loreto, Baja California Sur, Mexico. The lower part of the Neogene section consists of approximately 1500 m of early to middle Miocene nonmarine volcanic-derived sandstone, breccia, and porphyritic andesite and dacite lavas, called the Comondu Formation or Comondu Group by previous workers. The Miocene rocks are unconformably overlain by nearly 1000 m of predominantly marine sandstone, siltstone, conglomerate, coquina, and tuff of Pliocene age. This 1000-m section grades upward from unfossiliferous fanglomerate, sandstone, and pelitic red beds that are interpreted to be nonmarine into mollusk-rich marine strata; this sequence indicates that marine transgression occurred within the Pliocene section. Plagioclase and hornblende from three pumiceous tuff beds stratigraphically located near the base, middle, and top of the marine section yield K-Ar ages of 3.2, 1.9, and 1.8 Ma, respectively; these ages are similar to Pliocene ages indicated by reconnaissance studies of ostracods, diatoms, and foraminifers. The diatoms indicate open-ocean waters and the foraminifers indicate outer shelf depth. Ostracods, oysters, pectens, and other fossil bivalves seem to indicate a shallow-water embayment. Lateral distribution more » of nonmarine and marine facies suggests a paleoenvironment in which alluvial fans fed coarse debris into a series of coastal fan deltas. The Pliocene basin may have been a largely landlocked embayment similar to the modern Bahia Concepcion, located 70 km north of Loreto. Marine and volcanic rocks are assumed to be associated with the opening of the Gulf of California. If this assumption is correct, the beds near Loreto suggest that the opening occurred during the Pliocene. « less

SEDIMENTATION, SEA‐LEVEL RISE AND TECTONICS AT THE TRIASSIC‐JURASSIC BOUNDARY (STATFJORD FORMATION), TAMPEN SPUR, NORTHERN NORTH SEA

Statfiord Formation reservoir rocks (Rhaetian‐Sinemurian) of the Tampen Spur area, Northern North Sea consist of coarse‐ and fine‐grained units in alternation, in a succession up to 300‐m thick in places. The formation is interpreted in terms of coastal fans and fan deltas on a low‐energy coastline.Four broad facies associations are distinguished: subaerial fan and distal fan (partly subaqueous) deposits make up the coarse‐grained units, while the fine‐grained units consist of lagoon‐bay and floodbasin‐bay sediments. The deposits interpreted as subaerial fan‐plain and braided‐stream channels are dominantly cross‐stratified and plane‐bedded, coarse‐grained sandstones and fine‐conglomerates. The distal fan deposits, mainly massive or bioturbated finel/medium‐grained sandstones tend to occur at the base or top of the coarse units.The deposits interpreted in terms of a lagoon‐bay setting consist of wave‐rippled, flaser/lenticular bedded siltstone and fine‐grained sandstone in a “background”of dark grey mudstone with occasional coal beds. This association is thought to have originated largely in front of the fans. The floodbasin‐bay association, consisting mainly of red‐and green‐coloured, massive and bioturbated mudstone and silty sandstone is believed to have accumulated in ephemeral floodbasin lakes or in the inner regions of coastal embayments, between fans. In addition to the main associations, there are also marine reworked sandstones at the top of the formation in some areas.Sedimentation time trends within the coarse‐grained units reflect fan shifting and progradation. On the formation scale, the coarse units become coarser and more laterally‐continuous upward, whereas the fine units become dominated by the lagoon‐bay facies at younger stratigraphic levels.It is argued that the former was a response mainly to tectonics, while eustatic sea level rise accounts for the increase in marine deposits through time. The marine sandstone at the top of the formation suggests a transition from a low energy, protected shoreline to a higher energy, more open one; a change that is related to basin enlargement and increased rate of relative sea level rise at the Statfjord‐Dunlin Formation transition.

Structure of Coastal Washover Fans and Their Role in Internal Structure of Holocene Transgressive Sand Barriers: ABSTRACT

Structure of Coastal Washover Fans and Their Role in Internal Structure of Holocene Transgressive Sand Barriers: ABSTRACT

Baselevel, Grade and Peneplain

Baselevel, Grade and Peneplain