bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sedimentology and budget of a Recent carbonate mound, Florida Keys
Authors: BOSENCE DANIEL W. J. , ROWLANDS ROYSTON J. , QUINE MARK L. 
Published: June 2006

ABSTRACTThe sedimentology of a Recent carbonate mound is investigated to further our understanding of mound building communities, surface and subsurface mound sediments, and the overall sediment budget of mounds. Nine sedimentary facies of the surface of Tavernier mound, Florida Keys are described. These sediments are composed of Neogoniolithon, Halimeda, Porites, mollusc and foraminiferal grains, and lime mud. Muds rich in aragonite and high magnesian calcite show little mineralogical variation over the mound surface. Geochemical evidence suggests that the mud is mainly formed from breakdown of codiacean algae and Thalassia blade epibionts. Production rates of the facies are established from in situ growth rate experiments and standing‐crop surveys. Annual calcium carbonate production is c. 500gm‐2, intermediate between reef and other bay and lagoonal environment production rates in the Caribbean. The internal structure of the mound, studied from piston cores and sediment probes, indicates that seven facies can be identified. Five of these can be related to the present‐day facies, and occur in the upper part of the mound (gravel‐mound stage). The remaining two facies, characterized by molluscs and aragonite‐rich muds, occur in the lower part of the mound (mud‐mound stage), and are most similar to facies from typical Florida Bay mud mounds. Mangrove peats within the mound indicate former intertidal areas and C14 dates from these peats provide a time framework for mound sedimentation. The mound appears to have formed because of an initial valley in the Pleistocene surface which accumulated mud in a shallow embayment during the Holocene transgression.A sediment budget for the mound is presented which compares production rates from present‐day facies with subsurface sediment masses. During the mud mound stage production rates were similar to accumulation rates and the mound was similar to the present‐day mounds of Florida Bay. During the gravel mound stage (3400 yr BP‐present day), conditions were more normal marine and the establishment of Porites and Neogoniolithon on the mound increased production rates 10% over accumulation rates. This excess sediment is thought to be transported off the mound to the surrounding seabed. Models are proposed which divide carbonate mounds on the basis of internal versus external sediment supply. Comparisons are made with other Recent and ancient mounds. Similarities exist between the roles of the biotic components of late Palaeozoic mounds but major differences are found when structures and early diagenesis are compared.
Botryoidal aragonite and its diagenesis
Authors: AISSAOUI DJAFAR M. 
Published: June 2006

ABSTRACTBotryoidal aragonite is a spectacular growth‐form occurring as mamelons, up to 100 mm in diameter. Three examples of this particular carbonate cement have been discovered in two distinct areas: in New Caledonia, small‐scale mamelons have been recognized within Pleistocene reefal terraces at Ouvea, an Island of the Loyalty archipelago, and in the Red Sea, large‐scale mamelons of botryoidal aragonite exist within Pleistocene reefal terraces along the Um Gheig region of the Egyptian Coast. In addition, a similar botryoidal cement, partly dolomitized but exhibiting aragonite relics, occurs within a Miocene reef in the same region.Mamelons of botryoidal aragonite are isolated and/or coalescent but grow only on fixed substrates. They occur within cavities of varied origin. Their fabrics are characterized by fans of elongate euhedral crystals of aragonite fibres. Botryoidal aragonite can be preceded or followed by other types of cements or internal sediment.Despite similar mineralogy, petrography and ultrastructure, there are differences between the fabrics of the Pleistocene botryoids from the Red Sea and Ouvea and the Miocene botryoids from the Red Sea. The former are of submarine origin as confirmed by the strontium content (8500–10,500 ppm) and isotopic composition (δ18O between ‐0.10 and +0.19% PDB). The latter, related to a Miocene karst, are rich in strontium (average 13,600 ppm), and have an isotopic composition (average δ18O ‐10.50% PDB) indicative of non‐marine precipitation.Diagenesis of these botryoidal aragonites consists of slight dissolution for Pleistocene botryoids and mineralogical transformation for the Miocene botryoids. The latter exhibit the diagenetic sequence aragonite → calcite → dolomite. The aragonite to calcite transformation is a dissolution‐reprecipitation process, the void distribution and size influencing the distribution and the size of the replacement calcite crystals.
Mixed siliciclastic and carbonate sediments: a proposed first‐order textural and compositional classification
Authors: MOUNT JEFFREY 
Published: June 2006

ABSTRACTSediments that are composed of mixtures of siliciclastic and carbonate material occur in both the modern and the ancient. To date, there is no commonly‐used classification of this type of sediment. A descriptive, first‐order classification system is proposed here that is applicable to most mixed sediments and their lithified equivalents. The sediments are composed of four components: (1) siliciclastic sand (sand‐sized quartz, feldspar, etc.), (2) mud (mixtures of silt and clay), (3) allochems (carbonate grains such as peloids, ooids, bioclasts and intraclasts > 20 μm in size), and carbonate mud or micrite (< 20 μm in size). These components define a tetrahedra whose subdivision produces eight general classes of mixed sediment. The name of a class reflects both the dominant grain type and the most abundant antithetic component. For example, a rock that contains greater than 50% siliciclastic material, of which most is sand‐sized, and subordinate allochems is termed an allochemic sandstone. Other rock names include micritic sandstone, allochemic and micritic mudstone, sandy or muddy allochem limestone and sandy or muddy micrite. Prefixes and adjectives can be added to these terms to include dolomitic sediments, conglomeratic textures, and biogenic constituents.
Isolated stationary carbonate platforms: the Middle Triassic (Ladinian) of the Marmolada area, Dolomites, Italy
Authors: BLENDINGER WOLFGANG 
Published: June 2006

ABSTRACTAs a result of a phase of extensional tectonics in the western Tethyan region, a horst and graben topography formed during the Middle Triassic (Ladinian) in northern Italy. Horsts were sites of shallow water carbonate sedimentation, while pelagic and volcaniclastic sediments were deposited in the grabens. Two carbonate platforms approximately 500 m thick can be distinguished in the Marmolada area of the Dolomites: the Marmolada platform proper, which covered an area of 6 km2, and the Costabella platform, which extended for about 12 km in a NW‐SE direction and was about 3 km across.The facies of these isolated platforms reflect the influence of storms from the SW. Windward platform margins were characterized by a marine sand belt of skeletal and aggregate grainstones with a dominant platform directed cross‐stratification. The central portions of the platforms were occupied by supratidal sand cays which are made up of storm washovers. Leeward parts of the platforms are composed of shallow subtidal sand flat deposits. Laterally discontinuous reefs chiefly composed of various calcareous algae are developed at the outer margins of the platforms. Along windward margins, reefs may form a belt several hundred metres wide; along leeward margins their width is commonly reduced to some tens of metres. Foreslope talus breccias surround the platforms. Clinoform bedding showing basinward dips of 30°‐40° is typical of this facies belt, which is approximately 2 km wide. Basinal sediments, only some tens of metres thick, are radiolarian micrites. Abundant sediment‐gravity‐flow deposits expand the basinal sequence at the toes of windward margins and were probably triggered by storm return flows.Synsedimentary faults striking both NNE‐SSW and NW‐SE separate the bedded platform limestones from flank deposits and reefs. They account for the stationary nature of the platforms. Neptunian dykes show preferred NNE‐SSW and E‐W trends. Sinistral displacements are associated with NW‐SE trending faults. Depressions in the basins, filled with red, turbiditic pelagic sediments, show N‐S trends and are probably compressional in origin. The structural pattern may have resulted from oblique, NW‐SE oriented extension of the E‐W trending Middle Triassic graben zone of the Dolomites.In the Ladinian of the Dolomites, the stationary platform type can be distinguished from a retrograding type, whereas continuously prograding platforms apparently did not develop.
Sedimentation during carbonate ramp‐to‐slope evolution in a tectonically active area: Bowland Basin (Dinantian), northern England
Authors: GAWTHORPE ROB L. 
Published: June 2006

ABSTRACTThe Bowland Basin (northern England) contains a series of carbonates and terrigenous mudstones deposited during the Ivorian to early Brigantian. Two regional depositional environments are indicated by facies and facies associations. Wackestone/packstone and calcarenite facies indicate deposition in a carbonate ramp environment, while lime mudstone/wackestone, calcarenite and limestone breccia/conglomerate facies, often extensively slumped, represent a carbonate slope environment. Stratigraphic relations suggest that the depositional environment evolved from a ramp into a slope through the Dinantian.Two main sediment sources are indicated by the sequence; an extra‐basinal terrigenous mud source and a supply of carbonate from the margins of the basin. Deposition from suspension and from sediment gravity flows, in situ production and remobilization of sediment during sedimentary sliding were important processes operating within the basin.Periods of enhanced tectonic activity in the late Chadian to early Arundian and late Asbian to early Brigantian are indicated by basin‐wide horizons of sedimentary slide and mass flow deposits. Both intervals were marked by a decline in carbonate production resulting from inundation and uplift/emergence. The first of these intervals separates deposition on a seafloor with gentle topography (carbonate ramp) from a situation where major lateral thickness and facies variations were present and deposition took place in a carbonate slope environment. The second interval marks the end of major carbonate deposition within the Bowland Basin and the onset of regional terrigenous sedimentation.
Burial dolomitization of the Woo Dale Limestones Formation (Lower Carboniferous), Derbyshire, England
Authors: SCHOFIELD KEVIN , ADAMS ANTHONY E. 
Published: June 2006

ABSTRACTDolomite occurs in open‐shelf packstones and grainstones of the Vincent House Member of the Woo Dale Limestones Formation (Lower Carboniferous) in the Wye Valley area, east of Buxton, Derbyshire, Central England. Two stages of dolomitization can be recognized. Stage 1 consists of limpid, non‐luminescent dolomite lacking detectable iron and manganese. Stage 2 comprises cloudy, inclusion‐rich, orange‐red luminescing dolomite with significant iron and manganese. The contact between the two stages is irregular and suggests a hiatus between dolomite growth stages. Dolostones lacking any unreplaced limestone may contain up to 35% calcite cement rilling intercrystal porosity. This cement shows a characteristic zonal sequence and is normally in optical continuity with the surrounding dolomite crystals. In some cases, precementation compaction of the dolomite mosaic caused fracturing of the crystals. Sherds of dolomite on the floors of pore‐spaces then provided the nucleus for growth of calcite cement.The petrographic character and stratigraphic distribution of the dolomite suggest that dolomitization occurred at depth, during burial of the Woo Dale Limestones in the Late Carboniferous. Dolomitizing solutions, expelled from basinal shales, moved up‐dip along permeable limestones or along the sub‐Carboniferous unconformity. Fluids responsible for the generation of stage 2 dolomite may have been contaminated by ions such as iron and manganese released from the alteration of volcanic rocks which occur beneath the Carboniferous Limestone in the Wye Valley area.
Facies sequences on a carbonate ramp: the Carboniferous Limestone of South Wales
Authors: WRIGHT V. PAUL 
Published: June 2006

ABSTRACTDuring early Carboniferous times a major sea‐level rise led to the development of an extensive carbonate ramp over what is now South Wales. Differential subsidence and sea‐level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho‐tectonic settings; inner, mid‐ and outer ramp. The inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence. The sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments. The peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing‐up cycles. The sequence contains many subaerial breaks and tectonic uplift resulted in base‐level changes and fluvial incision. The mid‐ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base. Sedimentation periodically exceeded sea‐level rise and subsidence, and regressive (progradational) oolitic sand bodies developed, the thickest of which are stacked units with up to four individual sand bodies. Storm processes were of major importance in this setting. The outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major Waulsortian reef‐mounds also developed. None of the shallowing phases seen in the other ramp zones can be detected in this sequence. Subsidence and eustatic sea‐level rise seem to have been the major controls on deposition but the recognition of eustatic sea‐level falls is difficult. The detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record.
A storm and tidally‐influenced prograding shoreline—Upper Cretaceous Milk River Formation of Southern Alberta, Canada
Authors: McCRORY VERNON L. C. , WALKER ROGER G. 
Published: June 2006

ABSTRACTThe Santonian‐Campanian Milk River Formation of Southern Alberta represents the transition from an open shelf, through a storm‐dominated shoreface into a non‐marine sequence of shales and sandstones, with coal. The open shelf deposits consist of interbedded bioturbated mudstones with sharp‐based hummocky cross‐stratified sandstones. There are no indications of fairweather reworking of the sandstones, which are therefore interpreted as having been deposited below fairweather wavebase. The shoreface sequence consists of a 28 m thick sandstone. It has a very sharp, loaded base, and is dominated by swaley cross‐stratification, a close relative of hummocky cross‐stratification. Angle of repose cross‐bedding is preserved in scattered patches only in the top 5 m of the sand body. Channels up to 180 m wide and 7 m deep are cut into this sand body, with channel margins characterized by lateral accretion surfaces. Regional dispersal trends, as well as local palaeocurrent readings suggest flow toward the NW. Within the channels there is some herringbone cross‐bedding and at least two examples of neap‐spring bundle cycles, suggesting that the channels are tidally‐influenced. Above the channels there is a sequence of carbonaceous shales with in situ root casts and lignitic coal seams. No marine, brackish or lagoonal fauna was identified, and the sequence appears to represent a distal floodplain.The sequence from interbedded hummocky cross‐stratified sandstones and bioturbated mudstones into a 10–20 m thick, sharp‐based shoreface sandstone characterized by swaley cross‐stratification is uncommon. The scarcity or absence of angle of repose cross‐bedding in the shoreface, and the dominance of swaley cross‐stratification suggests that the shoreface was so storm‐dominated that almost no fairweather record was preserved. Other examples of swaley cross‐stratified shorefaces are reviewed in the paper.
Facies sequences of a semi‐arid closed basin: the Lower Jurassic East Berlin Formation of the Hartford Basin, New England, U.S.A.
Authors: DEMICCO ROBERT V. , KORDESCH ELIZABETH GIERLOWSKI 
Published: June 2006

ABSTRACTThe Lower Jurassic East Berlin Formation exposed in the centre of the Hartford Basin can be divided into six facies: (1) laminated black mudstone is composed of very finely‐laminated, organic‐bearing clay‐stone with common millimetre‐scale lenses of dolomitic siltstone; (2) planar laminated mudstone is commonly mudcracked and composed of thickly‐laminated, red, green or grey mudstone with common centimetre‐scale lenses of sandstones; (3) disrupted mudstone has a complex, desiccation‐cracked fabric; (4) planar‐ and large‐scale trough cross‐stratified sandstones are composed of moderately well‐sorted medium‐ to coarse‐grained arkoses; (5) small‐scale, cross‐stratified silty sandstones with common climbing‐ripple structure; and (6) interbedded sandstones and mudstones which commonly carry desiccation cracks.Mudstone facies are organized into repetitive, metre‐scale facies sequences which change gradationally upwards from laminated black mudstones to planar‐laminated mudstones to disrupted mudstones. Facies sequences have sharp tops and bottoms and record increasing desiccation upwards. There are 15 such cycles in the upper 100 m of the formation in central Connecticut. They record long periods of dry playa mudflat aggradation punctuated by the rapid expansion and contraction of perennial lakes.The sandy facies occur as single, decimetre‐scale sedimentation units or as two or more stacked sedimentation units up to 1 m thick. These record sheet floods across ephemeral floodplains.
A sedimentation pattern in Anglian marginal meltwater channels from Suffolk, England
Authors: MATHERS S. J. , ZALASIEWICZ J. A. 
Published: June 2006

ABSTRACTSeveral infilled glacial meltwater channels of Anglian age are described from SE Suffolk, U.K. These channels are up to 4km long, 150m wide and 8m deep. They possess a consistent pattern of infill comprising glacifluvial sands and gravels overlain by subglacial water‐lain fine sands and silts; these pass conformably upwards through thinly interstratified tills and sands into basal tills. The channels were formed at the ice‐margin. Their sedimentary infill indicates overriding by the ice‐sheet and subsequent subglacial deposition.
Ooids in Purbeck limestones (lowermost Cretaceous) of the Swiss and French Jura
Authors: STRASSER ANDRÉ 
Published: June 2006

ABSTRACT Ooids occurring in the shallow‐water Purbeckian carbonate sediments of the Jura mountains can be grouped into six types. Gradations from one type to another and coexistence of the various types are common.Type 1 ooids are small and well rounded. They display fine concentric micritic laminae. In many cases their cortices are dissolved and replaced by void‐filling spar. Microsparitic neomorphic replacement occurs locally. Type 2 ooids are large and have irregular shapes. They show fine micritic laminae and occasional layers of fine‐radial crystals. They commonly evolve into oncoids. Ooids of type 3 display many fine‐radial cortical laminae and are patchily micritized. They are medium in size and mostly well rounded. This type of ooid may pass into large, irregularly shaped coated grains. Type 4 ooids have 1 to 4 cortical laminae with a fine‐radial structure and patchy micritization. They are medium in size and well rounded. Type 5 ooids have only one lamina with a coarse‐radial structure. They are small and well rounded. Associated are spherical grains containing bundles of elongate crystals. Ooids of type 6 show superpositions of two or more different, radial and or fine micritic laminae. The cortical structure may also change laterally in the same lamina.The preferential dissolution of type 1 ooid cortices to form oomoulds indicates a primary composition of unstable carbonate. Sedimentological features and comparison with modern ooid occurrences point to formation on high‐energy sandbars in normal‐marine waters. Type 2 ooids grew in marine‐lagoonal environments with quiet water and abundant cyanobacteria. The radially structured ooid cortices of types 3, 4 and 5 show no dissolution features. This implies that they were originally composed of stable carbonates, or that an unstable carbonate phase was transformed into a stable one at an early stage of diagenesis. Type 3 ooids occur together with marine faunas and indicate high water energy. Ooids of type 4 and type 5 originated probably from relatively quiet water of variable salinity.Coexistence of different ooid types and mixed forms of type 6 implies gradual or rapid changes in hydrodynamic, geochemical and microbiological conditions which were a feature of the Purbeckian depositional environments.
Patterns of sediment composition of Jamaican fringing reef facies
Authors: BOSS STEPHEN K. , LIDDELL W. DAVID 
Published: June 2006

ABSTRACTRecent carbonate sediments from Jamaican north coast fringing reefs were collected along three parallel traverses in the vicinity of Discovery Bay. Each traverse extended from near shore across the back reef, reef crest, and fore reef to a depth of 75 m. Relative abundances of the biotic constituents vary between sites, reflecting general patterns of reef community composition. The sediment is dominated by highly comminuted coral fragments (27·1% to 63·1%), plates of the calcareous green alga Halimeda (0·4% to 38·7%), coralline algae (4·7% to 16·2%) and the encrusting foraminiferan Homotrema rubrum (0·7% to 9·5%), with lesser amounts of other taxonomic groups (non‐encrusting foraminifera 1·3–5·5%; molluscs 1·4–7·0%; echinoderms 0·9–5·0%). Coral fragments, coralline algae and particles of Homotrema rubrum dominate the sediments of the shallow portions of the fore reef (5–15 m), whereas plates of Halimeda are most abundant in sediments from the back reef and deeper portions of the fore reef ( 24 m). Q‐mode cluster analysis, using sediment constituent data, resulted in the delineation of four reef biofacies over the depth range of this study (1–75 m).