Carbonate Mud Deposition Research Articles

Hydrological and climate changes in southeast Siberia over the last 33 kyr

Abstract Paleoenvironmental and paleoclimate changes in intracontinental Siberia were reconstructed by continuous, high-resolution records (biogenic silica, U, total organic carbon and N, total S, and grain size) from a sediment core retrieved from the Buguldeika Saddle, Lake Baikal, dating back to the last 33 cal. ka BP. The Holocene climate was wet relative to the last glacial period. The climate became gradually warm and wet from the early to middle Holocene, followed by a shift at ca. 6.5 cal. ka BP toward warm and dry, possibly because of evapotranspiration. This suggests that the climate system transition from the glacial to interglacial state occurred at that time. In the last glacial, the deposition of carbonate mud from the Primorsky Range was associated with Heinrich events (H3 and H1) and the Selenga River inflow during the Last Glacial Maximum was caused by meltwater of mountain glaciers in the Khamar–Daban Range. The anoxic bottom-water during the Allerod-Younger Dryas was probably a result of weakened ventilation associated with reduced Selenga River inflow and microbial decomposition of organic matters originating from moderate input of nutrients from the Primorsky Range. The rapid decline in precipitation during the early Holocene may have been a response to the 8.2 ka cooling event.

Brachiopods and rugose corals in an upper Serpukhovian (Mississippian) biostrome: preliminary results from the Djebel Arhlal (Béchar Basin, Algeria)

The Djebel Arhlal is the southernmost outcrop of upper Serpukhovian strata in the Béchar Basin. Here the Djenien member of the Djenien Formation is three-folded and it contains a 10 m-thick coral biostrome in its middle unit formed by Siphonodendron, Diphyphyllum and Lithostrotion. Distances between in situ colonies are in the order of several decimetres and the space between them is filled with bioclastic limestone containing coral rubble. Few brachiopods and solitary corals are found as dwellers within the biostrome, but these groups are much more common in the strata below and above the coral biostrome. This is especially true for the brachiopods, which reach diversities of more than a dozen species in specific horizons. They mainly belong to the orders Productida, Spiriferida and Athyridida. Agitated open-marine platform interior or platform margin settings are the general facies encountered in the Djenien member at the Djebel Arhlal. The field data, including brachiopod coquinas and many fragmented brachiopods and corals, are confirmed by microfacies analysis. However, the coral biostrome records a quieter setting at the interface of middle and outer ramp settings, as seen in the co-existence of in situ coral growth, input of reworked material, deposition of carbonate mud, and sparitic textures. This autoparabiostrome at Djebel Arhlal is compared to other rather thick and of exceptional horizontal extension upper Serpukhovian biostromes (few kilometres).

Composition and Genesis of Temperate, Shallow-Marine Carbonate Muds: Spencer Gulf, South Australia

Abstract The origin of carbonate muds (grain sizes < 63 µm) in shallow, nontropical marine environments is poorly documented. Coarse-grained carbonates often characterize coastal temperate seafloors, but many such deposits also have abundant carbonate muds. Spencer Gulf, a large, shallow embayment along the southern Australian margin (< 60 m water depth), contains mixtures of carbonate gravels, sands, and muds, with muds constituting up to 84% volumetrically. Benthic environments include dense seagrass meadows, sand barrens, and rhodolith pavements where bivalves, benthic foraminifera, coralline algae, and bryozoans dominate heterozoan carbonate assemblages. Mud grain morphologies were investigated using scanning electron microscopy, leading to the conclusion that muds are predominantly composed of skeletal fragments (bivalves, benthic foraminifera, ascidians, echinoderms, and coralline algae), interpreted to have formed due to breakdown of rigid material via maceration. X-ray diffraction analysis confirms that these muds contain combinations of intermediate-Mg calcite, low-Mg calcite, and aragonite; with concentrations varying among locations according to skeletal grain types. Spencer Gulf muds differ in mineralogy and composition from those of classic models of tropical and deep-water carbonate mud deposition. Unlike shallow-water, tropical carbonate muds, these temperate muds are not dominated by aragonite and there is no evidence of carbonate precipitation from seawater. Pelagic organisms contribute only trivial amounts to these deposits, in contrast to deep-water muds.

Experimental Deposition of Carbonate Mud From Moving Suspensions: Importance of Flocculation and Implications For Modern and Ancient Carbonate Mud Deposition

Abstract Flume experiments with fine-grained carbonate particles (< 62.5 µm) show that they form floccules that travel in bedload, form current ripples, and deposit laminated sediments. In order to compare our flume experiments to work on sand transport, we ran flume experiments with medium sand and observed that the velocities at which sand grains started to move and form ripples were in the same range as those where floccules move and form ripples. These ripples are in essence identical to those formed by clay-mineral floccules or sand grains under similar conditions. In light of previous experiments with clay minerals, these results indicate that, of the key controls on mud deposition, flocculation and suspended-sediment concentration are more important than particle mineralogy or water chemistry, and are about as important as bottom shear stress for deposition. Suspensions of carbonate mud show the same pattern of flocculation, ripple formation, and bed accretion as observed previously in experiments with clay-mineral suspensions. The resulting carbonate mud deposits show internal low-angle (2–5 degrees) laminae, and in plan view a pattern of ripple foresets that is identical to rib-and-furrow structure in sandstones. Just as previously assumed for terrigenous muds, there has been a long-standing notion that accumulation of abundant carbonate mud reflects quiescent conditions of offshore and deeper-water environments. These experiments demonstrate unequivocally that carbonate muds can also accumulate in energetic settings. In the sedimentary record of carbonate rocks, interbedded grainstones and lime mudstones may thus not necessarily reflect shifts in depositional energy (or water depth), but alternatively may imply a shift in supplied sediment type. The observations we report suggest that published interpretations of ancient lime muds and derived paleoceanographic conditions may need to be reevaluated.

East Asia summer and winter monsoon evolution during the past 50 ka inferred from size-specific flux of mineral particles of the Lake Biwa sediment

Paleoenvironmental and paleoclimate changes in intracontinental Siberia were reconstructed by continuous, high-resolution records (biogenic silica, U, total organic carbon and N, total S, and grain size) from a sediment core retrieved from the Buguldeika Saddle, Lake Baikal, dating back to the last 33 cal. ka BP. The Holocene climate was wet relative to the last glacial period. The climate became gradually warm and wet from the early to middle Holocene, followed by a shift at ca. 6.5 cal. ka BP toward warm and dry, possibly because of evapotranspiration. This suggests that the climate system transition from the glacial to interglacial state occurred at that time. In the last glacial, the deposition of carbonate mud from the Primorsky Range was associated with Heinrich events (H3 and H1) and the Selenga River inflow during the Last Glacial Maximum was caused by meltwater of mountain glaciers in the Khamar–Daban Range. The anoxic bottom-water during the Allerød-Younger Dryas was probably a result of weakened ventilation associated with reduced Selenga River inflow and microbial decomposition of organic matters originating from moderate input of nutrients from the Primorsky Range. The rapid decline in precipitation during the early Holocene may have been a response to the 8.2 ka cooling event.

Hurricanes and climate in the Caribbean during the past 3700 years BP

A multiproxy analysis of lacustrine sediments cored in Grand-Case Pond at Saint-Martin, north of the Lesser Antilles archipelago, reveals three distinct climatic periods for the last 3700 years. From 3700 to ~2500 yr cal. BP and from 1150 yr cal. BP to the present, carbonate mud deposition occurred in connection with pond lowstands. These periods were also punctuated by severe drought events, marked by gypsum laminae, and hurricane landfalls, leading to marine sand inputs into the pond. The intermediate time interval, from 2500 to 1150 yr cal. BP, is typified by black organic mud deposition, suggesting that hypoxic to anoxic conditions prevailed at the pond bottom. These were probably linked with a perennial pond highstand and reflect more uniform and wetter climatic conditions than today. The carbon isotopic composition of the ostracod Perissocytheridea bisulcata shows that the lowest δ13C values are recorded during the hypoxic periods, as a consequence of bacterial recycling of isotopically depleted organic matter. Such a climatic history agrees closely with that documented from other records in the Caribbean area, such as the Cariaco Basin, central coast of Belize or Barbados. By constrast, discrepancies seem to emerge from the comparison between hurricane activity recorded at Saint-Martin on the one hand and Vieques (Puerto Rico) on the other hand. We explain this apparent contradiction by a balance between two distinct storm paths in response to latitudinal shifts of the Intertropical Convergence Zone (ITCZ). Stronger storm activity over the Gulf coast and the inner Caribbean Sea is favoured by a southern position of the ITCZ in connection with dry climatic conditions. Plausible links with the North Atlantic Oscillation (NAO) are also suggested.

Surficial Sediments of the Great Australian Bight: Facies Dynamics and Oceanography on a Vast Cool-Water Carbonate Shelf

ABSTRACT The Great Australian Bight (GAB), the largest sector of the southern Australia continental margin, is a site of cool-water carbonate sedimentation throughout, ranging from locally warm-temperate inboard to cool-temperate outboard. Surficial sediments are a mixture of calcareous Pleistocene skeletal and lithic intraclasts (relict grains), and Holocene biofragments, with minor amounts of quartz inboard. The inner is an area of abundant macrophytes and seagrasses, active carbonate sediment production and accumulation, and little relict sediment. The huge middle portion is a shaved shelf with active sediment winnowing and mostly relict sediment. The outer and upper slope is a variably productive sediment factory characterized by prolific calcareous epibenthic growth on hard substrate subaqueous islands shedding particles into surrounding sands and muds. Patterns of Holocene sedimentation are linked to modern oceanographic parameters in this high-energy setting characterized by overall downwelling. Prolific rhodoliths occur on the NW inner shelf, where shallow summer waters are the warmest in the GAB. These warm, saline, nutrient-depleted waters then drift eastward across the shelf, suppressing heterozoan carbonate production on the central and eastern mid-shelf. This arrested production in the eastern GAB is countered locally by summer coastal upwelling along western Eyre Peninsula, with bryozoan-rich sediment extending well inboard onto the mid-shelf. The outer and upper slope is an area of prolific bryozoan growth, likely linked to upwelling, except in the central GAB, a region of year-round downwelling, where the area is one of off-shelf fine sediment transport and carbonate mud deposition. These patterns, in the central GAB at least, are present in the underlying Holocene and Pleistocene, suggesting that the general modern oceanographic dynamics and resultant carbonate sedimentation have persisted throughout the Quaternary.

Subaerial exposure and deposition of shallowing upward sequences: evidence from stable isotopes of Purbeckian peritidal carbonates (basal Cretaceous), Swiss and French Jura Mountains

ABSTRACTPurbeckian (lowermost Cretaceous) peritidal carbonates are characterized by open marine, lagoonal, intertidal and lacustrine facies arranged in Milankovitch‐type shallowing upward sequences. Shallowing upward sequences typically consist of 2–6 individual beds. The sequences may be (i) complete, (ii) incomplete or (ii) pedogenetically overprinted, reflecting the duration of subaerial exposure and/or the extent of erosion and pedogenetic modification at the cycle tops.The stable isotopic composition of the peritidal micrites reveals homogenous δ18O values attributed to diagenetic stabilization in a meteoric, water‐buffered system. Carbon isotopes show three distinctly different carbon isotope patterns dependent on the completeness of the shallowing upward sequences. Complete shallowing upward sequences consist of 4–6 individual carbonate beds. The carbon isotope values show a facies‐dependent pattern: open marine carbonate muds record enriched δ13C values of +0·28‰ while lagoonal (−0·82‰), intertidal (−2·46‰) and lacustrine micrites (−2·96‰) are increasingly depleted. This distinct pattern is explained by carbonate mud deposition in environments of differing salinity and marine influence. Incomplete sequences (2–5 carbonate beds) are characterized by depleted δ13C values below subaerial exposure surfaces that become progressively enriched in 13C with increasing depth. Pedogenetically overprinted sequences (1–3 carbonate beds) show strong 13C depletion throughout the sequence with little variation in the carbon isotopic composition. The depleted values (−4·5‰) of the pedogenetically altered micrites suggest that modification during subaerial exposure was associated with equilibration with meteoric solutions enriched in isotopically light soil gas CO2.The duration of subaerial exposure is the most crucial factor determining the extent of pedogenetic alterations, the completeness of the shallowing upward sequences and the carbon isotope pattern. The recorded patterns clearly illustrate that micrites have a good potential for the preservation of their primary carbon isotopic composition if the duration of subaerial exposure is rather brief. Otherwise, the recorded carbon isotope patterns may support sequence stratigraphic analysis by providing a refinement of the time‐stratigraphic interpretation.

Origin of fine‐grained carbonate and siliciclastic sediments in an Early Palaeozoic slope sequence, Cow Head Group, western Newfoundland

ABSTRACTThe Cow Head Group is an Early Palaeozoic base‐of‐slope sediment apron composed of carbonate and shale. Whereas coarse‐grained conglomerate and calcarenite are readily interpreted as debris‐flow and turbidite deposits, calcilutite (lime mudstone), calcisiltite, and shale combine to form three distinct lithofacies whose present attributes are a function of both sedimentation and early diagenesis. Shale is the most common lithology. Black, green, and red shale colour variations reflect the abundance of organic matter in the source area and oxygenation conditions of the sea bottom. In black and green shale, millimetre‐ to centimetre‐thick, alternating dark and light laminations represent terrigenous mud turbidites and hemipelagites, respectively. The calcisiltite/shale facies is uncommon and is composed of numerous graded carbonate‐shale sequences (GCSS) deposited from waning carbonate turbidites and fall‐out of terrigenous muds. Some of the characteristics of ribbon and parted lime mudstones in the calcilutite/shale facies can be explained by deposition of carbonate mud from dilute turbidity currents or hemipelagic settling. Other features are diagenetic in origin.The lack of micrite in GCSS and in the interbedded shales of the calcilutite/shale facies is interpreted to reflect early dissolution of the finer carbonate from these sediments. This remobilized carbonate was precipitated locally to: lithify lime mudstone turbidites or hemipelagites; form diagenetic lime mudstone beds and nodules; cement calcisiltites; and form dolomite. Many of the calcisiltites and calcilutites were, therefore, carbonate enriched at the expense of adjacent argillaceous sediments.These attributes characterize not only fine‐grained sediments of the Cow Head Group but many other Early Palaeozoic slope carbonates as well, suggesting that the model proposed here for depositionl diagenesis has wider application.

Slope Sedimentation Associated with a Vertically Building Shelf, Bone Spring Formation, Mescalero Escarpe Field, Southeast New Mexico: ABSTRACT

Mescalero Escarpe field contains slope strata in the Bone Spring formation which provide insight into development of the Northwestern shelf to the north and the Delaware basin to the south. During the Leonardian (Permian), the Northwestern shelf grew vertically due to regional subsidence and cyclic sedimentation. Slope facies include (1) dolomitized peloid-bioclast packstone, (2) dolomite megabreccia, (3) laminated dolomitic mudstone, and (4) very fine-grained sandstone. Oil is produced from peloid-bioclast packstones and megabreccias. Stratigraphic relationships indicate carbonate sedimentation in slope and basinal environments contemporaneous with carbonate sedimentation on the shelf. Peloid-bioclast packstones overlain by megabreccias are present at the toe-of-slope, and dolomitic mudstones occur higher on the slope and deeper in the basin. Basinal sandstones are present between those carbonate strata. Seismic data show erosion and backstepping of the shelf margin correlative with megabreccia deposition at the toe-of-slope. Lithologic and stable isotope data suggest that erosion of the shelf took place in sea water. Depositional cycles are related to sea level cycles. (1) During rapid sea level rises, the shelf was flooded and carbonate sedimentation initiated. Sediment swept off the shelf formed peloid-bioclast packstones at the toe-of-slope and dolomitic mudstones in other slope and basinal environments. (2) As sea levelmore » rise slowed or stopped, the shelf approached sea level. The shelf margin was eroded, and debris flows transported eroded detritus to the toe-of-slope, and megabreccias formed. Deposition of carbonate mud continued in adjacent environments. (3) When sea level stayed still or dropped, the shelf was at sea level or emergent, and terrigenous sand was transported into the basin.« less

Ellenburger Group, Delaware Basin, West Texas: ABSTRACT

The Ellenburger Group in central and west Texas is part of a vast sheet of Lower Ordovician carbonate sediments deposited on the southern edge of the North American craton. In the west Texas area the Ellenburger, a 1,000 to 2,000-ft (300 to 600 m) section of dolomite, is extremely important as an oil and gas reservoir. Since the first discovery in 1928, the Ellenburger has produced more than 500 million bbl of oil in the Permian basin and, more recently, huge gas reserves have been established in the deep Delaware basin. During deposition of the Ellenburger carbonate sequence, the predominant environment was probably similar to the area of carbonate mud and pelletal carbonate mud deposition on the Great Bahama Bank. Today the Delaware basin section is largely microcrystalline to coarsely crystalline dolomite with many sedimentary structures indicative of shallow-water to supratidal deposition. On the basis of textures, fabrics, and insoluble residues, the Ellenburger Group in the Delaware basin may be divided into three units. Generally, porosity is confined to the middle and lower units and is related to subaerial solution and associated brecciation. Tectonic fracturing, related to late Paleozoic deformation, apparently is responsible for greatly increasing permeability. Several Ellenburger fields produce up to 50% carbon dioxide with methane. The carbon dioxide content increases in the west and south toward low-salinity formation water. Ellenburger hydrocarbons probably were derived from the overlying Simpson (Middle Ordovician) shale. End_of_Article - Last_Page 530------------

Stratigraphy of Sierra de Picachos and Vicinity, Nuevo Leon, Mexico

The section exposed in the Sierra de Picachos is approximately 4,900 ft (1,490 m) thick and is divisible into seven formations, which range in age from Neocomian to Campanian and possibly to Maestrichtian (Early to Late Cretaceous). These formations are, from oldest to youngest, Cupido, La Pena, Tamaulipas, Sombreretillo, Cuesta del Cura, San Felipe, and Mendez. The Sombreretillo is newly named, and the San Felipe has been redefined to include beds formerly assigned to the Agua Nueva Formation. The section is composed mainly of limestone with lesser amounts of dolomite (confined to the Cupido Limestone), chert, and terrigenous clay. The limestone is of one type, lithified carbonate mud (micrite). The micrite is classified into types based on the contained organic constituents, which consist principally of pelagic forms: foraminifers, calcispheres, tintinnids, and radiolarians. With the exception of the Cupido Limestone, the micrite is interpreted as representing basinal deposits. The depth of the water during deposition is unknown but may have been relatively shallow. The nature of the micrite in the Sierra de Picachos indicates that the sea floor was below wave base throughout deposition. The sea floor in the Sierra de Papagayos was above wave base during part of Tamaulipas deposition. Some of the carbonate mud may have been precipitated in the shallower shelf waters on the west, and then winnowed into the lower energy basinal environment. Intermittent rains of the calcareous tests of pelagic microorganisms contributed substantially to the mud. Chert occurs as lenses, stringers, and irregular nodules in the Cupido, La Pena, Tamaulipas, and Cuesta del Cura formations. The chert formed during diagenesis and the silica is thought to have come from siliceous organisms. The deposition of carbonate mud was interrupted several times (La Pena, Sombreretillo, San Felipe, and Mendez) by the influx of terrigenous clay resulting from climatic changes and/or tectonism in the source area. The final flood of terrigenous sediment (Mendez Shale), brought about by the Laramide orogeny, terminated carbonate deposition.

Sedimentary Facies in Area of Mixed Terrigenous-Carbonate Deposition, Arlington Reef Complex and Adjacent Areas, Northern Great Barrier Reef: ABSTRACT

The northern Great Barrier shelf can be divided into 3 major bathymetric zones: (1) the nearshore zone, extending to depths of 5 fm; (2) the inner shelf, extending to depths of 20 fm; and (3) the marginal shelf extending to the shelf edge at 40-50 fm. In the area studied, reef development is concentrated on the inner two thirds of the marginal shelf. Sedimentary facies in this area reflect three major influences: (1) source (terrigenous and carbonate); (2) hydrography; and (3) relic facies. On the inner shelf, nearshore terrigenous sand is succeeded seaward by dominantly terrigenous mud which transgresses two pre-Recent facies: (1) terrigenous sand in the north and (2) shell gravel in the south. Mixing of pre-Recent sediments, terrigenous mud, and modern carbonates (molluscan and foraminiferal) complicates the basic pattern. Both pre-Recent facies extend to within 1 mi of the reef with no significant dilution by modern reef-derived debris. Major interreef channels are floored by fine-grained, mixed terrigenous-carbonate sediment. The terrigenous material (30-50 percent) is dominantly silt and clay size. The identifiable, carbonate fraction is composed mainly of planktonic and benthonic Foraminifera, juvenile and larval mollusks, and skeletal debris. Most of this channel-floor sediment apparently is derived either from the inner shelf or from the open ocean; little appears indigenous. The main reef complex is built on a 16-fm platform, and encloses a central area of about 64 sq mi. Much of the interior platform is covered by low coral growth or by dead coral with a thin cover of worn, broken, and stained skeletal grains, mainly large Foraminifera, Halimeda, and coralline algae. Major sediment accumulation occurs only in the lee of the main reef where quiet-water conditions allow the deposition of carbonate mud with up to 18 percent fine terrigenous detritus. The sparse coarse fraction is molluscan, Foraminifera increasing in abundance near the reef. Reef-derived sediment is abundant only on and directly adjacent to the reefs. End_of_Article - Last_Page 551------------

Depositional Environment of the Devonian Tully Limestone of Central New York: ABSTRACT

Recent investigation of the Tully Limestone has resulted in the recognition of several general facies. Certain key beds appear to be relatively synchronous units that permit environmental reconstruction of several phases of deposition. In general, Tully deposition occurred in a carbonate mud-depositing sea with an eastern clastic source that exerted decreasing influence through time. The lower part of the Tully Limestone consists of arenaceous deltaic beds of limited areal extent. On the east, abundant Chonetes aurora and occasional Leptostrophia represent the restricted fauna of the brackish nearshore environment. Westward, the addition of other brachiopods, notably Hypothyridina, Atrypa, and Schizophoria, characterizes the more marine facies. Above the lower part of the formation, sandy limestone overlies the beveled eastern end of the delta and grades eastward into an iron-rich oolite which contains pebbles of dark siltstone. Deposition was extended also to the west, where purer carbonate mudstone is developed. The upper part of the Tully Limestone consists of carbonate mudstone characterized by the presence of metriophyllid and auloporid corals, styliolines, trilobites, and pelmatozoans. Toward the middle of this part, and representing normal marine conditions, is a diverse fauna developed to the east in dark calcareous shale and to the west in limestone. Erosion surfaces with burrows, channels, local carbonate-pebble conglomerates and filled mud cracks are evidence for the intermittent nature of carbonate mud deposition and are observed especially in the central and western regions. In the upper part of the formation near the town of Borodino, two elongate mounds of pure carbonate mudstone, about 15 feet high, contain structures similar to stromatactis and grade laterally into much thinner pelmatozoan calcarenites. These mounds are overlain by similar calcarenites which locally contain pebbles of carbonate mudstone. Whereas the lower mound contains a network of auloporid corals that could have been responsible for its development, the upper mound lacks auloporids. The position of the upper mound on the western flank, and quite possibly in the lee, of the lower mound suggests a current-controlled origin. Tully deposition was ended by the reducing environment of the Geneseo Black Shale, which encroached progressively from the west. Local lingering of the carbonate environment is shown by dark argillaceous limestone at the top of the section which contain only scattered remnants of the Tully fauna. End_of_Article - Last_Page 360------------