Aeolian Dune Facies Research Articles

Development of large‐scale sand bodies in a fault‐bounded lake basin: Pleistocene-Holocene Poyang Lake, Southern China

In fault-bounded lacustrine basins, the lake basement may be exposed due to tilting of crustal blocks, forming islands of varying size. Such islands are commonly associated with sandy facies that may serve as important reservoirs for oil and gas accumulation. The present study investigated large sand bodies of Pleistocene-Holocene age on Songmenshan Island in the center of Poyang Lake, Jiangxi Province, southern China. The relationship of sedimentation on Songmenshan Island to its formation history was analyzed by means of Google satellite observations and field studies combined with scanning electron microscope, grain size, and 14 C dating analyses. The area of Songmenshan Island (39 km2) represents 8% of the total lake area (500 km2), and its height (81 m) is several times greater than that of the depth of the surrounding lake (13 m). The island has been uplifted since ~ 5 Ma at a rate of ~ 16 m Myr− 1 as a consequence of intrabasinal block faulting. The surficial deposits of the island consist of wave-controlled beach-bars in the lower part (< 36 m elevation) and wind-controlled eolian dunes in the upper part. Sedimentary characteristics were different between beach bars and sand dunes in terms of bedding, sedimentary structures, and grain size and texture. The beach bars are characterized by low-angle cross-bedding, fan-shaped conchoidal, and disciform fractures, and small V-shaped impact craters on quartz grain surfaces. The eolian dunes are characterized by large-scale high-angle cross-bedding, dish-, crescent-, and V-shaped impact craters on quartz grain surfaces. Whereas sand movement in the beach-bar facies was dominantly through traction, saltation was the major process in the eolian dune environment. The depositional history of Songmenshan Island can be divided into 3 stages: (1) deltaic sedimentation from the Ganjiang and Xiushui rivers, which are connected to the Yangtze River via a channel; (2) wave reworking of deltaic sediments in shoreline beach-bar facies after initial uplift; and (3) wind reworking of sands in eolian dune facies following further uplift. Later in its history, Songmenshan Island was reduced through wind and wave erosion into two subequal parts (19.6 km2 and 19.8 km2), producing its present configuration. The large sand bodies comprising this island may eventually be buried in a cocoon of organic-rich lacustrine muds, yielding an exploration target. Songmenshan Island may thus serve as a model for development of sand-rich reservoir facies in fault-bounded lacustrine basins.

Pleistocene terrace deposition related to tectonically controlled surface uplift: An example of the Kyrenia Range lineament in the northern part of Cyprus

In this study, we consider how surface uplift of a narrow mountain range has interacted with glacial-related sea-level cyclicity and climatic change to produce a series of marine and non-marine terrace systems. The terrace deposits of the Kyrenia Range record rapid surface uplift of a long-lived tectonic lineament during the early Pleistocene, followed by continued surface uplift at a reduced rate during mid-late Pleistocene. Six terrace depositional systems are distinguished and correlated along the northern and southern flanks of the range, termed K0 to K5. The oldest and highest (K0 terrace system) is present only within the central part of the range. The K2–K5 terrace systems formed later, at sequentially lower levels away from the range. The earliest stage of surface uplift (K0 terrace system) comprises lacustrine carbonates interbedded with mass-flow facies (early Pleistocene?). The subsequent terrace system (K1) is made up of colluvial conglomerate and aeolian dune facies on both flanks of the range. The later terrace systems (K2 to K5) each begin with a basal marine deposit, interpreted as a marine transgression. Deltaic conglomerates prograded during inferred global interglacial stages. Overlying aeolian dune facies represent marine regressions, probably related to global glacial stages. Each terrace depositional system was uplifted and preserved, followed by subsequent deposits at progressively lower topographic levels. Climatic variation during interglacial–glacial cycles and autocyclic processes also exerted an influence on deposition, particularly on short-period fluvial and aeolian deposition.

Late Miocene ground sloth footprints and their paleoenvironment: Megatherichnum oportoi revisited

Fossil footprints of ground sloths are mostly restricted to the late Miocene to Pleistocene of South America. This study is focused on the oldest known ground sloth trackways, Megatherichnum oportoi Casamiquela, 1974 from the late Miocene Río Negro Formation of northern Patagonia. The section logged at the study site, near Carmen de Patagones (Buenos Aires province), includes the uppermost part of the middle member (marine) and the upper member (aeolian) of the Río Negro Formation. Identified sedimentary facies can be grouped into four facies associations: tidal flat, aeolian dune, dry/damp interdune and wet interdune (shallow lacustrine). M. oportoi trackways are preserved in an upper intertidal mixed flat. Associated trace fossils belong to a wet aeolian system developed close to the sea coast and were mostly preserved in interdune facies. These include Poaceae root and stem traces and Nagtuichnus meuleni (Chlamyphorinae burrow) in dry interdune facies, indeterminate tetrapod footprints in damp interdune facies, Lockeia siliquaria and chevron-like trace fossils (bivalve resting and horizontal locomotion traces) in wet interdune facies (shallow lakes), and Palaeophycus tubularis in aeolian dune facies. The most likely trackmaker of M. oportoi is Pyramiodontherium sp. (Megatheriinae), recorded from the same stratigraphic unit at Chubut province, with a body mass ranging from 2.5 to 3.6t. M. oportoi is interpreted as a quadrupedal trackway of a late Miocene ground sloth without overlap of the pes on the manus. The previously proposed bipedal interpretation for the trackway requires angles of gait in excess of those permitted for such a large and heavy animal. Pleistocene ground sloth trackways are distinctive because of the much smaller size of the fore footprint. For the latter examples, a quadrupedal locomotion with overlap of the pes on the manus may be applied.

Trace Fossils in Eolian Facies of the Upper Triassic-Lower Jurassic Dinosaur Canyon Member, Moenave Formation, Northern Arizona

The Dinosaur Canyon Member of the Moenave Formation, of Late Triassic to Early Jurassic (Rhaetian-Hettangian) age, consists predominantly of sandstones and mudstones deposited by sheet and channelized flow and by eolian processes. We document several previously undescribed biogenic structures in these strata. At one location, eolian dune sandstone hosts the lined, smooth-walled burrow Palaeophycus heberti (Saporta); these may be the nesting burrows of small sand wasps, or alternatively, the burrows of sand-treader camel crickets. Eolian dune facies that host abundant rhizoliths also are typically bioturbated. Circular markings that are convex in epirelief are assigned to Pustulichnus gregarious Ekdale and Picard. Unlined, non-ornamented burrows are unassigned. We speculate that both of these also were formed by the burrowing activity of one of the many species of sand wasp. Rhizoliths are particularly prominent at the tops of eolian dune sandstone beds and locally may host termite nests. Stabilization of the landscape by plants permitted pedogenic alteration of the sediments.

Sedimentary cycles and facies architecture of aeolian–fluvial strata of the Upper Jurassic Guará Formation, southern Brazil

AbstractThe Upper Jurassic Guará Formation comprises an 80–200 m thick continental succession exposed in the western portion of the Rio Grande do Sul State (Brazil). It comprises four distinct facies associations: (i) simple to locally composite crescentic aeolian dune sets, (ii) aeolian sand sheets, (iii) distal floodflows, and (iv) fluvial channels. The vertical stacking of the facies associations defines several 5–14 m thick wetting‐upward cycles. Each cycle starts with aeolian dune sets followed by aeolian sand sheets deposits and culminating in either fluvial channels or distal flood strata. Within some cycles, aeolian sand sheets are absent and fluvial deposits rest directly above aeolian dune facies. The transitions from one facies association to another are abrupt and marked by erosive surfaces that delineate distinct episodes of sediment accumulation. The origin of both the wetting‐upward cycles and the erosive surfaces was controlled by the ground‐water table level, dry sand availability and aeolian and fluvial sediment transport capacity variations, related to climatic fluctuations between relatively arid and humid conditions. Preservation of the fluvial–aeolian deposits reflects an overall relative water table rise driven by subsidence.

Stratigraphic Trap in the Permian Unayzah Formation, Central Saudi Arabia

ABSTRACT The recent discovery in Central Saudi Arabia of Arabian Super Light oil in 'Usaylah-1 confirms stratigraphic trap potential of the Permian Unayzah Formation. The trap is an updip pinch-out of an upper Unayzah sandstone along the eastern flank of the north-south trending Hawtah anticline. The seal is the basal shales and siltstones of the Khuff and Unayzah formations and the source rock is the Lower Silurian Qusaiba Shale. The well encountered an oil column of 31 feet in an upper Unayzah eolian dune facies. The areal distribution of the prospect was mapped with a 3-D seismic survey. Seismic horizon slices and relative amplitude maps at the target reflection clearly delineate the trap. The oil-productive Unayzah sandstone is imaged as a high-amplitude reflection in an isolated area of approximately 8 square kilometers. Seismic isochron maps are proving effective in focusing future exploration to areas of similar stratigraphic trap potential in the region.

The West Sole Field, Block 48/6, UK North Sea

Abstract West Sole is located in the Sole Pit area of the Southern North Sea Permian Basin in UK Block 48/6. The field was discovered in 1965 and was the first commercial discovery in the UK Continental Shelf. Gas Production commenced in 1967. Initial reserves are 1.873 TCF of which 1.335 TCF had been produced by the end of 1989. Gas is trapped in aeolian sandstones of the Permian Lower Leman Sandstone Formation. Three depositional facies are recognized, comprising aeolian dune, fluvial and sabkha. The aeolian dune facies form the principal reservoir sandstones, in units up to 40 m (131 ft) thick. However, permeability is reduced due to pervasive illite cementation, such that it averages 3 md in the dune sandstones. Productivity is enhanced in the southern part of the field by 'open' gas-filled fractures, generated during the Alpine inversion. The trap was also amplified at this stage and comprises a faulted inversion anticline trending NW-SE. The source rock is the Westphalian Coal Measures, lying directly beneath the reservoir.

Sedimentary environment and facies of St Lucia Estuary Mouth, Zululand, South Africa

The St. Lucia Estuary is situated on the subtropical, predominantly microtidal Zululand coast. Modern sedimentary environments within the estuary fall into three categories: (1) barrier environments; (2) abandoned channel environments; and (3) estuarine/lagoonal environments. The barrier-associated environment includes tidal inlet channel, inlet beach face, flood-tidal delta, ebb-tidal delta, spit, backspit and aeolian dune facies. The abandoned channel environment comprises washover fan, tidal creek tidal creek delta and back-barrier lagoon facies. The estuarine/lagoonal environment includes subtidal estuarine channel, side-attached bar, channel margin, mangrove fringe and channel island facies. Each sedimentary facies is characterised by sedimentary and biogenic structures, grain-size and sedimentary processes. Vertical facies sequences produced by inlet channel migration and lagoonal infilling are sufficiently distinct to be recognized in the geological record and are typical of a prograding shoreline.

Quaternary Sedimentation and Diagenesis in a High-Latitude Reef, Houtman Abrolhos Islands, Western Australia: ABSTRACT

The Houtman Abrolhos reefs are located 80 km off the west coast of Australia between latitudes 28 and 29{degree} south. The islands are situated on three Pleistocene carbonate reef platforms which rise above the surrounding shelf. The modern coral reefs are close to the geographic limit for coral growth in the southern hemisphere and survive due to the presence of the Leeuwin current (a poleward-flowing warm stream). Two major shallow-water benthic communities coexist in the Abrolhos: a macroalgal-dominated community on the windward platform margins and a coral-dominated community on the leeward margins. These communities overlap-particularly in the platform lagoons, where competition between macroalgae and corals is intense. This interaction has been suggested as a major factor controlling the growth of cord reefs at high latitudes. The Holocene carbonate sediments lack nonskeletal components and are dominated by coral and coralline algal fragments with subordinate molluskan and echinoderm debris. The accumulations can be grouped into the following major facies: (1) coral framestone and coralline algal/serpulid boundstone, (2) submarine sand sheets, (3) subaerial coral storm ridges, (4-) peritidal to subtidal shingle and rubble veneers composed of dominantly coral debris, and (5) eolian dunes and beach sand. The Holocene sediment is a thin (<more » 2 m) veneer on the Pleistocene reef platform, which is emergent as small islands. The Pleistocene platform is composed of reef facies that can be directly related to the Holocene sediments. The platform is composed of framestone and boundstone facies (corals and coralline algal/serpulid facies), rudstones (submarine coral rubble facies), planar-bedded skeletal grainstones dipping 12-13{degree} (submarine sand sheet and peritidal shingle facies), and large 15-m-high eolianite dunes (eolian dune facies).« less

Erg margin of the Permian White Rim Sandstone, SE Utah

ABSTRACTThe Permian White Rim Sandstone of the Canyonlands National Park, Utah, contains a wide variety of sedimentary structures and features that largely result from stages in erg migration and marine influence on an erg margin. Three spatially distinct lithological and depositional facies are recognized and can be distinguished as informal units within the formation. The aeolian dune facies is composed predominantly of fine‐grained cross‐stratified sandstone of the White Rim erg. This facies is the most widespread and comprises the bulk of the formation. Within the aeolian dune facies are small subfacies that represent interdune deposits. A sheet sand facies, composed of parallel‐bedded sandstone, makes up a significant part of the lowest part of the White Rim Formation. This facies appears to have been the precursor or leading (progradational) edge to the main erg system. The final facies is a reworked or veneer facies of rippled to disturbed sandstone that is localized in its extent. It is restricted to the upper few metres of the formation and is transitional in some places to the Triassic Moenkopi Formation. This veneer facies contains many structures which indicate marine reworking as well as periods of desiccation or subaerial exposure.Some previous interpretations of the White Rim Sandstone have tended to classify the whole formation as one depositional setting. It is clear that at the margin of a sand sea, as shown in the White Rim Sandstone, there are transitional facies due to the interactions with other environments. Additionally, variation in the stratigraphic relationships of facies can be related to stages of erg migration. Erg margin deposits preceded central erg development. Erg initiation occurred during a probable relative sea level low. Sea level influence is recorded at the top of the formation because erg termination accompanied a relative sea level high with cut‐off of sand supply. Transgression of the Permian Kaibab Sea over the White Rim erg was probably the main process in preservation of original dune topographic relief. Sea level fluctuations also may have affected distribution of facies and the complexities of structures at the erg margin. Subsequent fluvial reworking of the veneer facies may have obliterated Late Permian features during lowest Triassic Moenkopi deposition.

Stratigraphic development, mineral sources and preservation of marine placers from Pleistocene terraces in Southern Oregon, U.S.A.

Marine placers containing economic minerals (chromite, ilmenite, magnetite and zircon) have been extensively studied in Pleistocene coastal deposits of southwest Oregon. The two largest placers occur on adjacent, uplifted terraces south of a prominent headland, Cape Arago, and include the older Seven Devils placer, covering 11 km 2 and containing 1.1 × 10 7 m 3 placer sand (heavy minerals > 50% weight abundance) and the younger Pioneer placer, covering about 0.9 km 2 and containing 9 × 10 5 m 3 placer sand. The most highly enriched beds of placer ore, containing at least 6% chromite by weight, are generally concentrated in the bottom 1–4 m of terrace stratigraphic sections. Upsection sequences of nearshore to inner-shelf facies in the Seven Devils deposit, and beach to eolian dune facies in the Pioneer deposit, respectively, indicate placer formation during (1) marine transgression, and (2) sea-level high stand with beachface progradation. Microprobe analyses of opaque minerals establish local river sources of placer minerals for both Seven Devils and Pioneer deposits. In contrast, younger terrace and modern beach deposits are supplied by distant river sources, 100–150 km south, as well as local rivers, indicating increasing net northward littoral drift during successive marine transgressions. Placer thickness in the Seven Devils and Pioneer deposits are controlled in part by platform gradient and paleo-tidal range, respectively. Placer development and preservation in this high wave-energy active-margin setting are strongly controlled by paleo-shoreline orientation and littoral cell bounding headlands.

Aeolian dune and wet interdune sedimentation in the Middle Proterozoic Dala sandstone, Sweden

The Middle Proterozoic Dala sandstone covers an extensive area in west-central Sweden and the adjacent parts of Norway, but it is poorly exposed. However, a series of quarries in the lower part of the sandstone provides good exposures that allow an interpretation of the environment of deposition in this part of the unit.Only two facies have been distinguished: Facies A, an aeolian dune facies, and Facies B, a wet interdune facies. Facies A consists of large-scale cross-stratified sandstone in which cross-stratified sets are up to almost 4 m thick, while the maximum foreset dip is 25°. Sandflow and subcritically climbing translatent strata have been recognized in this facies, but the identification of grainfall strata is uncertain. Penecontemporaneous folding and brecciation of cross-strata has taken place locally. Facies B, which was deposited simultaneously with Facies A, consists of sandstone with thin mud laminae, an irregular wavy structure, and numerous wave-rippled and mud-cracked surfaces. The increasing proportion of Facies B relative to Facies A passing up the stratigraphic section may herald an approaching coastline.Lack of recognition, rather than preservational bias, is thought to be the reason for the apparent scarcity of aeolianites in the Precambrian.

Petrology of Pennsylvanian Tensleep Sandstone, Lost Soldier Field, Wyoming: ABSTRACT

The Pennsylvanian Tensleep Sandstone in the Lost Soldier field of Sweetwater County, Wyoming, is composed of texturally homogeneous, fine-grained sandstones and interbedded dolomite beds. Geologic setting and sedimentary features indicate that the Tensleep was deposited in supratidal-eolian environments. Detailed, petrographic, cathodoluminescence, and SEM analyses of core samples show nine diagenetic events in the Tensleep: (1) early calcium sulfate cementation; (2) precipitation of feldspar overgrowths; (3) poikilotopic nodular calcite cementation; (4) nodular anhydrite cementation; (5) late anhydrite cementation; (6) precipitation of silica overgrowths and silicification of carbonates; (7) alteration of feldspar; (8) dolomite cementation and dolomitization; and (9) hyd ocarbon migration and accumulation. Four diagenetic facies with specific patterns of alterations have been identified: (1) early carbonate-precipitation facies; (2) early anhydrite-cementation facies; (3) primary carbonate-grain facies; and (4) nodular-cementation facies. Diagenetic alterations in each diagenetic facies were primarily controlled by lithologic characteristics within the original depositional environments. The carbonate-rich diagenetic facies are closely associated with the supratidal sabkha depositional facies. The anhydrite-rich facies is related to the interdune sabkha depositional facies, and the nodular-cementation facies is present within rocks deposited in the eolian-dune facies. Reservoir qualities (porosity and permeability) of the Tensleep Sandstone in the Lost Soldier field vary considerably and, with the mineral composition of the Tensleep, were modified significantly by diagenetic alterations. They can be estimated from knowledge about the distributions and associations of depositional and diagenetic facies. End_of_Article - Last_Page 565------------