Adhesion Ripples Research Articles

The wet desert system of the Upper Jurassic of the Parnaiba Basin, in the region between Formosa da Serra Negra and Montes Altos, Maranhão State, Brazil

O Mesozoico foi marcado por mudanças geológicas significativas decorrentes da Orogenia Gonduanide, que possibilitou a implantação de sistemas desérticos concomitantemente com expressivos eventos magmáticos. No Brasil, o registro desses eventos é observado na porção central da Bacia do Parnaíba, representados pelos depósitos siliciclásticos da Formação Corda, de idade jurássica, que sobrepõem derrames basálticos da Formação Mosquito. O estudo de fácies e estratigráfico de afloramentos dessa unidade, realizado na região entre Formosa da Serra Negra e Montes Altos, estado do Maranhão, possibilitou reconstituir o paleoambiente e inferir condições paleoclimáticas para essa região da Bacia Parnaíba durante o Jurássico. Foram identificadas quinze fácies sedimentares agrupadas em três associações de fácies (AF), representativas de um sistema desértico: 1) canal fluvial entrelaçado (AF1), caracterizado por conglomerados e arenitos finos a grossos, com grãos e seixos de rochas vulcânicas, com estratificações plano-paralela e cruzada acanalada; 2) lençóis arenosos (AF2), constituídos por arenitos finos a grossos e pelitos subordinados com laminação plano-paralela, laminação cruzada cavalgante, marcas de adesão e gutter casts; 3) campo de dunas (AF3), arenitos finos a médios, com grãos arredondados e estratificações cruzadas tabular e tangencial. Fluxos fluviais efêmeros (AF1), adjacentes ao campo de dunas (AF3), frequentemente retrabalhavam o topo das planícies vulcânicas e, esporadicamente, invadiam os lençóis arenosos (AF2). Comparado aos ergs do Permo-Triássico, o sistema desértico Corda foi mais úmido e menos extenso, precedendo os sistemas fluviais e costeiros de clima mais ameno do Cretáceo da Bacia do Parnaíba

Sediment characteristics and microfacies analysis of Jizan supratidal sabkha, Red Sea coast, Saudi Arabia

Jizan sabkha extends along the southeastern coastal plain of the Red Sea, Saudi Arabia, and is considered as one of the main problems that has a negative impact on infrastructure of buildings. Field examination of the surface of the wet sabkha area indicated the presence of sedimentary surface structures produced by physical forces such as adhesion ripples, tepee polygonal ridges, efflorescent halite pods, and structures produced by microbial activities such as petees and blisters. Microfacies analysis of the siliciclastic and evaporite lithofacies types has been done for sediment samples from the surface, trenches, and cores. The siliciclastic lithofacies type represents the host sediments in Jizan sabkha and consists of sand and mud. The evaporite lithofacies type is distinguished into three microfacies types of gypsum, anhydrite, and halite. The gypsum microfacies types are represented by diagenetic growth of individual lenticular, twinned lenticular, twinned complex lenticular, rosettes, nodular, poikilotopic, porphyroblastic, alabastrine, and clastic gypsum. The anhydrite microfacies types are represented by nodular and enterolithic anhydrite. The halite microfacies types are represented by primary rafts, cumulates, chevrons and cornets, and diagenetic overgrowth and mosaic halite cement. The structural and textural characteristics of the evaporite sediments indicated the formation of primary halite crystals at the brine surface and floor of saline pans, and the diagenetic formation of gypsum and anhydrite below the sediment surface as intrasediment displacive, inclusive, and replacive growth in the wet sandflat and mudflat areas. Recognition of such structural and textural features of the evaporite sediments helps in solving engineering geological problems in Jizan area and allowed also for interpreting the similar sabkha sediments in the rock record.

Neoarchaean ( c . 2.58 Ga) halite casts: implications for palaeoceanic chemistry

Possibly the most extensive and best-preserved Archaean halite casts yet discovered occur in the c . 2.58 Ga upper Black Reef and basal Oaktree formations, Transvaal Supergroup, in Mpumalanga Province, South Africa. Halite casts are isolated on bedding planes, range in size from c . 1 mm to 20 mm, and have cubic, dumbbell and triangular shapes, as well as hopper-like pyramidal hollows on cube faces. Some of the casts display distinct hopper shapes characteristic of halite crystals. The halite cast-bearing pavements are developed within silicified mudstone interbedded with siltstone or stromatolitic dolomite. Associated sedimentary structures pointing to subaerial exposure include adhesion ripples and warts, desiccation and prism cracks, rill marks and tepee structures. Halite cast-bearing beds are interpreted as supratidal flat or sabkha deposits. The presence of isolated casts and hopper-shaped crystals suggests that halite resulted from displacive growth within the sediment from supersaturated residual brines after mudstone deposition. Absence of any indication of the former presence of gypsum or anhydrite supports previous contentions that the Neoarchaean ocean was deficient in sulphate or contained a high bicarbonate to calcium ratio such that with progressive evaporation, most calcium was consumed before the gypsum stability field was reached. The association of halite and carbonate in the upper Black Reef and basal Oaktree formations constrains the palaeolatitude of the Transvaal Basin at 2.58 Ga to subequatorial (10–30°).

First steps on land: Arthropod trackways in Cambrian-Ordovician eolian sandstone, southeastern Ontario, Canada

Basal terrestrial deposits in the Cambrian-Ordovician Nepean Formation (Potsdam Group) near Kingston, Ontario, contain arthropod-produced trackways that extend the record of the first arthropod landfall back by as much as 40 m.y. The presence of large, simple cross-beds and of wind-produced structures, including adhesion ripples and wind-ripple lamination, indicates that the host strata were deposited in an eolian dune field, probably in a marginal-marine setting. The trackways were preserved mainly as undertracks and record the activities of large, amphibious arthropods, possibly euthycarcinoids.

Tectonic Event Stratigraphy in a Fluvio-Lacustrine, Strike-Slip Setting: The Boss Point Formation (Westphalian A), Cumberland Basin, Maritime Canada

ABSTRACT The Boss Point Formation (Westphalian A) was deposited in a rapidly subsiding strike-slip basin. The formation, about 800 m thick, comprises alternate braidplain and lacustrine associations. Sixteen megacycles, defined by sharp but nonerosive lacustrine flooding surfaces, each comprise a lower lacustrine and an upper braidplain package. Braidplain deposits invariably scour deeply into lacustrine strata. The lacustrine association consists of very fine sandstone, mudstone, claystone, coal, and limestone deposited in shallow, hydrologically open freshwater lakes. Lakes were filled by small, elongate, river-dominated deltas, and by suspended and biogenic sediment. Sand-rich deltaic represent mouth bar, subaqueous levee, crevasse channel and splay, and straight and sinuous distributary-channel subenvironments. Evidence of wave reworking is very scarce. Interdeltaic areas accumulated platy gray mudstone. As interdistributary bays aggraded to water level they were subject to oxidation and pedogenic modification, forming bright colors, prismatic (desiccation) fabrics, pseudo-anticlines, and calcretes. Thin but laterally extensive (possibly up to 40 km) abandonment facies comprising black, organic-rich mudstones, coals, and ostracod limestones suggest periods of clastic starvation. Dunes, current ripples, and rarely adhesion ripples are common on the top surfaces of braidplain sandstone packages, preserved beneath a blanket of lacustrine mudstone. Rare oscillation ripples attest to localized reworking of the fluvial sand during or soon after flooding. Flooding surfaces can be traced for 12 km, and possibly up to 40 km, and are attributed to instantaneous subsidence along the northwest margin of the basin during major earthquakes. One locality preserves evidence of abrupt, 180° paleoflow reversals above and below a lacustrine unit. This is interpreted to record abrupt basin tilting, first to the northwest, forming a lake that filled from the southeast, followed by tilting to the southeast. We interpret Boss Point megacycles to reflect the interaction of episo ic tectonic subsidence with longer-term changes in sediment supply controlled by cyclical climatic variation in the Milankovitch band. During periods of pronounced wet-dry seasonality when clastic supply was high, sandy and gravelly braidplain deposits prevailed, and any lakes that formed by earthquake-related subsidence were rapidly filled. During more humid periods, higher vegetative cover greatly reduced clastic supply, and lakes persisted for many thousands of years. Hydrologic changes accompanying the transition from relatively humid to strongly seasonal wet-dry periods might have resulted in the deep fluvial erosion observed at the base of each braidplain package.

Palaeowind: geological criteria for direction and strength

The practical geological indicators of palaeowind are several scalar properties (bed thickness, grain size and sorting, mineral proportions) and directional structures (dune forms, yardangs and wind furrows, dune cross-bedding, windblow n trees, wind ripples, adhesion ripples, flutes and grooves). These indicators ideally should be sampled so as to minimize geographical bias, and the data assessed so as to afford smoothed paths of sand and dust flow. Because most geological wind-related processes involve a threshold wind speed and proceed nonlinearly, inferred patterns of sand and dust flow may not exactly match patterns of the time-averaged wind direction. The use and potential of palaeowind indicators are well illustrated by w indblown trees (mid Flandrian, southwest Britain) and by dune cross-bedding (Palaeozoic-Mesozoic, U.S.A.).

Depositional Environment of the Yates Formation in Kermit Field, Winkler County, Texas: ABSTRACT

The Yates Formation (Permian Guadalupian) is a series of alternating clastic and carbonate units deposited on a shallow marine shelf in repetitive cycles: (1) a mottled, anhydritic dolomite at the base, (2) an overlying oxidized wind-blown very fine-grained sand and silt, (3) a bioturbated, but otherwise massive, sandstone, and (4) an uppermost massive dolomite containing oolites or skeletal material. A typical cycle is 10-20 ft thick. Deposition of the Yates was controlled by fluctuations in sea level governed by glacial activity and local tectonics. During sea level low stands, carbonates were dolomitized and displaced by anhydrite. This was followed by deposition of wind-blown sediments creating planar horizontal laminae and exposure features (desiccation cracks, tepee structures, and adhesion ripples). During sea level high stands, dunes an the platform were deposited as sheet sands. Lastly, a carbonate layer was deposited before sea level dropped and another cycle began. Sands were transported to the Central Basin platform as eolian dunes from the Pedernal highlands of central New Mexico. Wind direction for the Permian is documented as south-southeast based on mapping of sand dunes in the southwestern US. Quartz size in the clastics ranges from 0.03-0.11 mm, averaging 0.07 mm. The sandstones are homogeneous,more » well sorted, and most quartz grains are frosted. Except for planar wind laminae, these units contain only indistinct primary sedimentary structures, constrained by small grain size and grain size uniformity within beds. The clastics are 52% monocrystalline quartz, 17% feldspar, 4% rock fragments, 5% other minerals, and 22% matrix (dolomite in the carbonates and authigenic clays in the clastics).« less

Morphology and genesis of asymmetric adhesion warts—a new adhesion surface structure

Adhesion surface structures have been studied during their formation on a fluvial bar in East Greenland. Two main types occurred: adhesion ripples and asymmetric adhesion warts. Adhesion ripples formed on moist surfaces; their crests lay transverse to the wind direction and they migrated by trapping dry wind-blown sand on their steep fronts. Asymmetric adhesion warts (new structure) formed because of falling moisture content by preferred upwind migration of small protuberances on the adhesion ripples. The protuberances were apparently inherited from an initial rain sculpturing of the bar surface. The asymmetric adhesion warts, here described for the first time, were elongate parallel to the wind, associated with steep upwind-facing fronts and commonly displayed sand-shadow tails tapering in a downwind direction. A study of Devonian flood-basin deposits (Hornelen Basin, Norway) revealed the existence of adhesion surface structures very similar to their modern analogues. The Devonian examples were associated with rain-sculptured surfaces which are believed to have controlled the morphology of the adhesion surface structures as in the modern example. The orientation of the ancient adhesion surface structures is here used for determination of the palaeowind, which blew from the ENE.

Late Palaeozoic cold-climate aeolianites, southern Cooper Basin, South Australia

Summary Core facies analysis of the Permo-Carboniferous Gidgealpa Group of the southern Cooper Basin, South Australia has revealed sandstones of aeolian origin within the glacigenic Merrimelia Formation. The aeolianites comprise exclusively porous, poorly cemented, medium- and fine-grained sandstones dominated by parallel lamination. Sharp, planar truncation surfaces divide the suite into units composed mainly of translatent windripple lamination and minor amounts of sandflow bedding with primary depositional dip (post-compaction) varying between 0° and 25°. Distinctive compressional, tensional and dissipation structures are preserved in deformed lee-slope deposits and the inclusion of low-angle cross-strata and wedge-bedded units locally indicate deposition on the basal aprons of dunes or in contiguous sand sheets. Wet interdune sediments with adhesion ripples are also exhibited in the cores. The aeolianites, up to 232 m thick, have been traced subsurface by integrating core facies, wireline logs and seismic reflection analysis. A low-interval transit time on sonic logs is characteristic of the porous aeolianite sand and has facilitated mapping of the dune field using seismic data. The sandstone body trends SE-NW, is 6 to 8 km wide and passes laterally into outwash fan and fluvioglacial, braidplain deposits. Potential hydrocarbon traps may occur at the top of the aeolianites, or within them beneath intraformational seals formed by possible muddy interdune facies. The overall high-latitude, cold-climate nature of the Merrimelia Formation, deposited during the extensive Gondwanaland glaciation, is well known but this discovery not only records the first Gondwanan aeolianite suite but may also detail the first pre-Quaternary example of paraglacial aeolianites.

Major Discoveries in Eolian Sandstone: Facies Distribution and Stratigraphy of Jurassic Norphlet Sandstone, Mobile Bay, Alabama: ABSTRACT

Recent exploratory and development drilling in Mobile Bay, southwest Alabama, has proven prolific gas production from the Norphlet sandstone at depths greater than 20,000 ft with individual well tests of 10-27 MMCFGD. Excellent reservoir qualities are a function of preserved primary porosity and permeability developed in an eolian setting. In Mobile Bay, thick eolian sediments (200-600 ft) lie directly on Pine Hill or Louann evaporites. Three facies of the Norphlet have been recognized: (1) a thin (20-30 ft) basal wet sand flat or sabkha facies, (2) a massive dune facies, and (3) a thin (30-40 ft) upper marine reworked facies. The wet sand flat or sabkha facies is characterized by irregular to wavy horizontally bedded sandstone associated with adhesion ripples. It is probably sporadically developed in response to localized wet lows during earliest Norphlet deposition. The majority of the Norphlet section is characterized by massive wedge-planar and tabular-planar cross-stratified sandstone, interpreted to be stacked dune and dry interdune deposits. Individual dune sets range in height from a few feet to 90 ft. Cross-bed sets exhibit internal stratification patterns similar to large- and small-scale dunes described by G. Kocurek and R. Dott, Jr. The marine reworked facies is characterized by structureless to diffuse or wavy laminated sandstone that reflects a reworking of the dune deposits by the ensuing Smackover transgression. Reservoir quality is affected by textural properties determined by depositional processes associated with these various facies. Diagenetic patterns further reducing reservoir quality occur in the depositionally less-porous sediments. Dune facies sediments exhibit the best reservoir qualities. Variations of reservoir quality within the dune facies are related to dune height and dune versus interdune accumulations. End_of_Article - Last_Page 278------------

Permian White Rim Sandstone Member of Cutler Formation: Coastal Dune Field, Utah: ABSTRACT

The White Rim Sandstone Member of the Permian Cutler Formation in Canyonlands National Park, Utah, was deposited in a coastal eolian environment. This conclusion is based on sedimentary structures, petrologic features, and stratigraphic relations. The White Rim consists of two major genetic units. These units may represent a coastal dune field and related interdune ponds. Distinctive sedimentary structures of the coastal dune unit include large to medium-scale, unidirectional, tabular planar cross-bedding; high-index ripples paralleling dip direction of the foresets; raindrop impressions; slump marks; and coarse-grained lag layers. Also, a predominant northwest to southeast orientation of the cross-bedding agrees with the paleowind direction proposed in this area for Perm an time. Distinctive sedimentary structures of the interdune pond unit include wavy, horizontally laminated bedding, adhesion ripples, and desiccation(?) polygons. These features may have been produced by water-table fluctuations. Petrologic characteristics of the White Rim help to define the depositional environment as coastal. A crinoid fragment was identified at one location; heavy minerals are present in both units; and small amounts of well rounded, reworked glauconite are present throughout the study area. The White Rim Sandstone Member was deposited during a period of changing sea level and migrating strandlines. Continental sedimentation was dominant in eastern Utah, along the ancestral Uncompahgre Mountains; and marine deposition was prevalent in western Utah. Rocks deposited in the two environments interfinger in the Canyonlands area. Previous authors have proposed that the White Rim represents either a shallow-marine or eolian facies equivalent to both the upper part of the Toroweap Formation and the Gamma Member of the Kaibab Limestone. Results from this study suggest that the White Rim more likely represents eolian deposition on a prograding shoreline characterized by a semiarid climate and predominantly onshore winds. End_of_Article - Last_Page 570------------

Quasi-Planar Adhesion Stratification--An Eolian Structure Formed in Wet Sand

ABSTRACT Quasi-planar adhesion stratification is formed by the deposition of windblown sand on dune, beach, and other sandy surfaces that are wet but unmarked by adhesion ripples. The absence of adhesion ripples may result either from the insufficient wetness of the surface or from the tendency for raindrop impacts to inhibit ripple growth. The stratification is characterized by its indistinctness and by small-scale crenulations that result from the slight roughness of the depositional surface.

Rain-Impact Ripples

ABSTRACT The oblique impact of wind-driven rain on relatively fine-grained sand produces small, asymmetric rippleforms spaced about a centimeter apart and 2-3 mm high. Rain-impact ripples physically resemble adhesion ripples; the asymmetry, however, of rain-impact ripples relative to the formative winds directly opposes that of adhesion ripples.

Pseudo-Crosslamination Formed by Climbing Adhesion Ripples

ABSTRACT Adhesion ripples, which are formed when saltating dry sand adheres to a wet sand surface, migrate upwind during deposition of the sand. The internal structure of climbing adhesion ripples resembles crosslamination, because stratification defining successive positions of the depositional surface is typically absent or very poorly defined. Deposits formed by these ripples are likely to be preserved, and, if well exposed, this structure may be distinguishable from crosslamination.