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B. CHARLOTTE SCHREIBER GERALD M. FRIEDMAN† ARVEDO DECIMA‡ EDWARD SCHREIBER 《Sedimentology》1976,23(6):729-760
In Sicily, Messinian evaporitic sedimentary deposits are developed under a wide variety of hypersaline conditions and in environments ranging from continental margin (subaerial), to basin-margin supratidal, to intertidal, to subtidal and out into the hypersaline basin proper. The actual water depth at the time of deposition is indeterminate; however, relative terms such as ‘wave base’ and ‘photic zone’ are utilized. The inter-fingering relationships of specific evaporitic facies having clear and recognizable physical characteristics are presented. These include sub-aerial deposits of nodular calcium sulphate formed displacively within clastic sediments; gypsiferous rudites, arenites and arenitic marls, all of which are reworked sediments and are mixed in varying degrees with other clastic materials (subaerial, supratidal, and intertidal to deep basinal deposits). Laminated calcium sulphate alternating with very thin carbonate interlaminae and having two different aspects; one being even and continuous and the other of a wavy, irregular appearance (subtidal, intertidal, and supratidal deposits). Nodular calcium sulphate beds, usually associated with wavy, irregular laminated beds (supratidal, sabkha deposits); very coarsely crystalline gypsum beds (selenite), associated with more even, laminated beds (subaqueous, intertidal to subtidal deposits); wavy anastomozing gypsum beds, composed of very fine, often broken crystals (subaqueous, current-swept deposits); halite having hopper and chevron structures (supratidal to intertidal); and halite, potash salts, etc. having continuous laminated structure (subaqueous, possibly basinal). Evidence for diagenetic changes is observed in the calcium sulphate deposits which apparently formed by tectonic stress and also by migrating hypersaline waters. These observations suggest that the common, massive form of alabastrine gypsum (or anhydrite, in the subsurface) may not always be ascribed to original depositional features, to syndiagenesis or to early diagenesis but may be the result of late diagenesis. 相似文献
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Evolution of late Triassic rift basin evaporites (Passaic Formation): Newark Basin, Eastern North America 总被引：1，自引：0，他引：1
The Passaic Formation of the late Triassic Newark Supergroup is 2700 m thick and was deposited in series of wide, deep to shallow lacustrine environments in the Newark rift basin (eastern North America). The Passaic Formation can be divided into lower, middle, and upper sections based on depositional structures, composition and the distribution and morphology of its evaporites. Evaporites formed as a result of syndiagenetic cementation and/or displacive processes. Evaporitive minerals now include gypsum and anhydrite, although other mineral species, such as glauberite, may have originally existed. Most of the evaporites of the Passaic Formation occur within massive red mudstone and siltstone lithologies in the form of diffuse cements, void-fillings, euhedral crystals, crystal clusters and nodules. These evaporites grew displacively within the fine siliciclastic matrix as a result of changes in the hydrochemical regimes of the rift basin. A well-developed upward increase in the amount of evaporite material is present in the Passaic Formation. This resulted from: (1) long-term, progressive increase in aridity, and (2) significant increase in evaporation surface area of the basin during its tectonic evolution. A nonmarine source for the evaporites is evident from the isotopic data. Sulphate δ34S ranges from 11%. to 3.3%. CDT, while δ18O ranges from + 15.1%. to + 20.9%. SMOW, indicating derivation from early diagenetic oxidation of organic sulphur and pyrite within the organic-rich, lacustrine deposits. The 87Sr/86Sr ratios in sulphate are radiogenic (average 0.71211), showing the interaction of basin waters with detrital components and that the Newark Basin was isolated from the world ocean. Most of the original evaporites show evidence of diagenetic change to polycrystalline and polymineralic pseudomorphs now filled with recrystallized coarse-grained anhydrite (1–3 mm size) and low-temperature albite. Homogenization temperatures of fluid inclusions within the coarse-grained anhydrite indicate crystallization temperatures for anhydrite in the range of 150° to 280°C. Such elevated temperatures resulted from circulation of hot water in the basin. Later exhumation of these rocks caused partial to total replacement of anhydrite by gypsum in the upper part of the section. The resulting increase in volume due to hydration of anhydrite at shallow depths also emplaced non-evaporative satin-spar veins (fibrous gypsum) along bedding planes and in fractures. While the local geology of the Newark rift basin controlled the distribution of facies, the sedimentological development of the Passaic Formation evaporites resulted from the world-wide climatic aridity that prevailed during the late Triassic. because the Newark Basin sequence was only covered with about 3 km of sedimentary overburden that correspond to about 100°C and hence suggests that evaporites have experienced alteration by hot fluids. 5 As the Triassic marks the greatest evaporite formation world-wide and profound sense of parched continentality throughout the world existed before the final break-up of the Pangea, the Passaic Formation evaporites are an example of the influence of these palaeoclimatic conditions at the eastern margin of North America. 相似文献
3.
Laboratory experiments show that the propagation and sedimentation patterns of particle-laden gravity currents are strongly influenced by the size of suspended particles. The main series of experiments consisted of fixed-volume releases of dilute mixtures containing two sizes of silicon carbide particles (25 μm and 69 μm mean diameter) within a 6-m flume. Polydisperse experiments involved mixtures of five different particle sizes and variation of the amounts of the finest and coarsest particles. All variables apart from the initial relative proportions of particles were identical in the experiments. The effects of mixing different proportions of fine and coarse particles is markedly non-linear. Adding small amounts of fine sediment to a coarse-grained gravity current has a much larger influence on flow velocity, run-out distance and sedimentation patterns than adding a small amount of coarse sediment to a fine-grained gravity current. The experiments show that adding small amounts of fine particles to a coarse-grained current results in enhanced flow velocities because the fine sediment remains suspended and maintains an excess current density for a much longer time. Thus, the distance to which coarse particles are transported increases substantially as the proportion of fines in the flow is increased. Our experiments suggest that sandy turbidity currents containing suspended fines will be much more extensive than turbidity currents composed of clean sand. 相似文献
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CHARLOTTE FOG KROHN NICOLAJ KROG LARSEN CHRISTIAN KRONBORG OLE BJØRSLEV NIELSEN KAREN LUISE KNUDSEN 《Boreas: An International Journal of Quaternary Research》2009,38(4):811-833
Lithostratigraphy and chronostratigraphy of samples from 18 deep boreholes in Vendsyssel have resulted in new insight into the Late Weichselian glaciation history of northern Denmark. Prior to the Late Weichselian Main advance c. 23–21 kyr BP, Vendsyssel was part of an ice‐dammed lake where the Ribjerg Formation was deposited c. 27–23 kyr BP. The timing of the Late Weichselian deglaciation is well constrained by the Main advance and the Lateglacial marine inundation c. 18 kyr BP, and thus spans only a few millennia. Rapid deposition of more than 200 m of sediments took place mainly in a highly dynamic proglacial and ice‐marginal environment during the overall ice recession. Mean retreat rates have been estimated as 45–50 m/yr in Vendsyssel with significantly higher retreat rates between periods of standstill and re‐advance. The deglaciation commenced in Vendsyssel c. 20 kyr BP, and the Troldbjerg Formation was deposited c. 20–19 kyr BP in a large ice‐dammed lake in front of the receding ice sheet, partly as glaciolacustrine sediments and partly as rapid and focused sedimentation in prominent ice‐contact fans, which make up the Jyske Ås and Hammer Bakker moraines. In the northern part of central Vendsyssel, at least four generations of north–south orientated tunnel valleys are identified, each generation related to a recessional ice margin. This initial deglaciation was interrupted by a major re‐advance from the east c. 19 kyr BP, which covered most of Vendsyssel. An ice‐dammed lake formed in front of the ice sheet as it retreated towards the east; the Morild Formation was deposited here c. 19–18 kyr BP. Related to this stage of deglaciation, eight ice‐marginal positions have been identified based on the distribution of large tunnel‐valley systems and pronounced recessional moraines. The Morild Formation consists of glaciolacustrine sediments, including the sediment infill of more than 190 m deep tunnel valleys, as well as the sediments in recessional moraines, which were formed as ice‐contact sedimentary ridges, possibly in combination with glaciotectonic deformation. The character of the tunnel‐valley infill sediments was determined by proximity to the ice margin. During episodes of rapid retreat of the ice margin, tunnel valleys were quickly abandoned and filled with fine‐grained sediments in a distal setting. During slow retreat of the ice margin, tunnel valleys were filled in an ice‐proximal environment, and the infill consists of alternating layers of fine‐ to coarse‐grained sediments. At c. 18 kyr BP, Vendsyssel was inundated by the sea, when the Norwegian Channel Ice Stream broke up, and a succession of marine sediments (Vendsyssel Formation) was deposited during a forced regression. 相似文献
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NICOLAJ KROG LARSEN CHARLOTTE FOG KROHN CHRISTIAN KRONBORG OLE BJØRSLEV NIELSEN KAREN LUISE KNUDSEN 《Boreas: An International Journal of Quaternary Research》2009,38(4):762-786
The Quaternary sedimentary succession in Vendsyssel, northern Denmark, contains a unique, high‐resolution record of the last interglacial and glacial periods. There is still much debate, however, about the timing and ice extent in this southwestern part of the Scandinavian Ice Sheet, particularly during the Middle Weichselian. In this study, a detailed lithostratigraphical subdivision is established for the Late Saalian to Middle Weichselian Skærumhede Group on the basis of numerous, up to 250 m deep, boreholes in Vendsyssel. The sediments mainly consist of marine clays, glaciolacustrine sediments and tills, and the total thickness of the Skærumhede Group is up to 140 m. Marine intervals have been used as stratigraphical marker units to separate the formations indicative of ice‐sheet activity in Vendsyssel, and the timing of the events has been constrained by a large number of optically stimulated luminescence (OSL) and radiocarbon ages. The Skærumhede Group is subdivided into seven formations and two members, reflecting shifts between marine and terrestrial sedimentation caused by fluctuations of the Scandinavian Ice Sheet and changes in sea level. The lowermost Skærumhede Till Formation was deposited directly on top of the bedrock during the Warthe advance c. 160–140 kyr BP. Above, there are fine‐grained marine sediments, subdivided into the Lower, Middle and Upper Skærumhede Clay Formations. The marine formations are separated by the Brønderslev Formation related to the Sundsøre ice advance from the north c. 65–60 kyr BP, and the Åsted Formation, deposited during the Ristinge advance from an east–southeastern direction c. 55–50 kyr BP. The uppermost formation in the group is the Lønstrup Klint Formation, which is an upwards‐coarsening sequence of mainly glaciolacustrine sediments deposited prior to the Kattegat advance c. 30–29 kyr BP. The new evidence from Vendsyssel has shown that the Skærumhede Group covers a large area, and that it can be used as a regional stratigraphical marker horizon. Furthermore, it contributes to a better understanding of the timing and extent of glacial events during the Late Saalian to Middle Weichselian in southwest Scandinavia. 相似文献
6.
CHARLOTTE J. SPARRENBOM OLE BENNIKE SVANTE BJÖRCK KURT LAMBECK 《Boreas: An International Journal of Quaternary Research》2006,35(2):171-187
We present results from an investigation of relative sea-level changes in the Qaqortoq area in south Greenland from c. 11 000 cal. yr BP to the present. Isolation and transgression sequences from six lakes and two tidal basins have been identified using stratigraphical analyses, magnetic susceptibility, XRF and macrofossil analyses. Macrofossils and bulk sediments have been dated by AMS radiocarbon dating. Maximum and minimum altitudes for relative sea level are provided from two deglaciation and marine lagoon sequences. Initially, relative sea level fell rapidly and reached present-day level at ∼9000 cal. yr BP and continued falling until at least 8800 cal. yr BP. Between 8000 and 6000 cal. yr BP, sea level reached its lowest level of around 6-8 m below highest astronomical tide (h.a.t.). At around 3750 cal. yr BP, sea level has reached above 2.7 m below h.a.t. and continued to rise slowly, reaching the present-day level between ∼2000 cal. yr BP and the present. As in the Nanortalik area further south, initial isostatic rebound caused rapid isolation of low elevation basins in the Qaqortoq area. Distinct isolation contacts in the sediments are observed. The late Holocene transgression is less well defined and occurred over a longer time interval. The late Holocene sea-level rise implies reloading by advancing glaciers superimposed on the isostatic signal from the North American Ice Sheet. One consequence of this transgression is that settlements of Palaeo-Eskimo cultures from ∼4000 cal. yr BP may have been transgressed by the sea. 相似文献
7.
B. CHARLOTTE SCHREIBER 《Sedimentology》1974,21(2):329-331
Detrital particles were found as a sand-silt layer in a deep-sea Messinian Stage (Upper Miocene) salt deposit in the Mediterranean Basin (Balearic Sea). These particles include worn and limonite-coated quartz, feldspar, glauconite, volcanic glass, reworked Messinian foraminifera and some lutecites. The lutecites are not original to the salt and taken in their association with the other detritus, especially the foraminifera, suggest syndepositional reworking of exposed Messinian evaporites. 相似文献
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9.
The Upper Gypsum unit of the Caltanissetta Basin (Sicily) records the last phase of the Messinian salinity crisis comprising the so‐called ‘Lago Mare’ event. A new facies analysis study recognizes nine to ten depositional cycles consisting of seven rhythmically interbedded primary gypsum bodies, and two to three sandstone bodies separated by marly terrigenous horizons showing laterally persistent vertical organization. A basal thin gypsum bed is overlain by a cluster of five thicker gypsum bodies. A marly interval containing two distinct sandstone horizons separates this cluster from the overlying uppermost (seventh) gypsum body. The terrigenous Arenazzolo Formation, in turn followed by the lower Pliocene Trubi Formation, is considered here to form the uppermost part of the Upper Gypsum unit. The rhythmic alternation in the sandy marls and gypsum/sandstone bodies records the response of sediments from shelfal to deltaic systems to precession‐driven arid‐wet climate fluctuations causing cyclical changes of both base‐level and water concentration. During wet climate phases (at insolation maxima) marl and sandstone were deposited in a hypohaline environment as suggested by: (i) the typical Lago Mare faunal assemblage and (ii) the negative δ18O values. During arid phases (at insolation minima) the reduced meteoric supply, recorded by higher δ18O values in the carbonate, caused the development of a negative hydrological budget leading to evaporite precipitation. At a basinal scale the Upper Gypsum unit unconformably overlies a mainly clastic evaporite unit containing carbonate breccia (the so‐called ‘Calcare di Base’) and/or clastic gypsum. Towards the basin centres, where the basal contact becomes conformable, a primary gypsum cumulate horizon is present. This layer is interpreted as a possible lateral equivalent of the Halite unit present only in the deepest depocentres. Based on astronomical calibration of the depositional cycles, the Upper Gypsum unit, including the Arenazzolo Formation, spans the interval between 5·33 and 5·53 Ma. This new age calibration allows the deposition of the Halite unit to be dated between 5·6 Ma (top of the Lower Evaporites) and 5·55 Ma (base of the Upper Evaporites) corresponding to isotopic stages TG12 and/or TG14. 相似文献
10.
NICOLAJ KROG LARSEN KAREN LUISE KNUDSEN CHARLOTTE FOG KROHN CHRISTIAN KRONBORG REW S. MURRAY OLE BJØRSLEV NIELSEN 《Boreas: An International Journal of Quaternary Research》2009,38(4):732-761
Based on a large number of new boreholes in northern Denmark, and on the existing data, a revised event‐stratigraphy is presented for southwestern Scandinavia. Five significant Late Saalian to Late Weichselian glacial events, each separated by periods of interglacial or interstadial marine or glaciolacustrine conditions, are identified in northern Denmark. The first glacial event is attributed to the Late Saalian c. 160–140 kyr BP, when the Warthe Ice Sheet advanced from easterly and southeasterly directions through the Baltic depression into Germany and Denmark. This Baltic ice extended as far as northern Denmark, where it probably merged with the Norwegian Channel Ice Stream (NCIS) and contributed to a large discharge of icebergs into the Norwegian Sea. Following the break up, marine conditions were established that persisted from the Late Saalian until the end of the Early Weichselian. The next glaciation occurred c. 65–60 kyr BP, when the Sundsøre ice advanced from the north into Denmark and the North Sea, where the Scandinavian and British Ice Sheets merged. During the subsequent deglaciation, large ice‐dammed lakes formed before the ice disintegrated in the Norwegian Channel, and marine conditions were re‐established. The following Ristinge advance from the Baltic, initiated c. 55 kyr BP, also reached northern Denmark, where it probably merged with the NCIS. The deglaciation, c. 50 kyr BP, was followed by a long period of marine arctic conditions. Around 30 kyr BP, the Scandinavian Ice Sheet expanded from the north into the Norwegian Channel, where it dammed the Kattegat ice lake. Shortly after, c. 29 kyr BP, the Kattegat advance began, and once again the Scandinavian and British Ice Sheets merged in the North Sea. The subsequent retreat to the Norwegian Channel led to the formation of Ribjerg ice lake, which persisted from 27 to 23 kyr BP. The expansion of the last ice sheet started c. 23 kyr BP, when the main advance occurred from north–northeasterly directions into Denmark. An ice‐dammed lake was formed during deglaciation, while the NCIS was still active. During a re‐advance and subsequent retreat c. 19 kyr BP, a number of tunnel‐valley systems were formed in association with ice‐marginal positions. The NCIS finally began to break up in the Norwegian Sea 18.8 kyr BP, and the Younger Yoldia Sea inundated northern Denmark around 18 kyr BP. The extensive amount of new and existing data applied to this synthesis has provided a better understanding of the timing and dynamics of the Scandinavian Ice Sheet (SIS) during the last c. 160 kyr. Furthermore, our model contributes to the understanding of the timing of the occasional release of large quantities of meltwater from the southwestern part of the SIS that are likely to enter the North Atlantic and possibly affect the thermohaline circulation. 相似文献