Sedimentological Cycles Research Articles

Gulf of Nuna: Astrochronologic correlation of a Mesoproterozoic oceanic euxinic event

AbstractThe ca. 1.4 Ga Velkerri and Xiamaling Formations, in Australia and the north China craton, respectively, are both carbonaceous shale deposits that record a prominent euxinic interval and were intruded by ca. 1.3 Ga dolerite sills. These similarities raise the possibility that these two units correlate, which would suggest the occurrence of widespread euxinia, organic carbon burial, and source rock deposition. Paleomagnetic data are consistent with Australia and the north China craton being neighbors in the supercontinent Nuna and thus permit deposition in a single large basin, and the putative stratigraphic correlation. However, lack of geochronological data has precluded definitive testing. The Xiamaling Formation has been shown to exhibit depositional control by orbital cycles. Here, we tested the putative correlation with the Velkerri Formation by cyclostratigraphic analysis. The Velkerri Formation exhibits sedimentological cycles that can be interpreted to represent the entire hierarchy of orbital cycles, according to a sedimentation rate that is consistent with Re-Os ages. Comparison of the inferred durations of the euxinic intervals preserved in both the Xiamaling and Velkerri Formations reveals a nearly identical ∼10-m.y.-long oceanic euxinic event. This permits the interpretation that the two hydrocarbon-rich units were deposited and matured in the same basin of Nuna, similar to the Gulf of Mexico during the breakup of Pangea.

Spatio-temporal variations of hydrochemistry and modern sedimentation processes in the Nam Co basin, Tibetan Plateau: Implications for carbonate precipitation

Lake monitoring studies are essential for understanding the modern biogeochemical and sedimentological cycles to enable and support the interpretation of paleolimnological records. However, such studies remain scarce for high-altitude lakes in general and specifically for lakes on the Tibetan Plateau. We investigated the hydro-chemical and physical properties of lake Nam Co and its twenty-one major inflowing rivers from 2011 to 2013. The modern sediment flux and sediment properties were determined for samples collected by sediment traps deployed for the same study period at different water depths at three sites in Nam Co. Carbonate weathering in the catchment, especially pronounced during the monsoon season, was identified as the predominant origin of dissolved riverine hydrochemical components. The sediment budget shows remarkable temporal variation, with trends of intensified sediment fluxes during the non-monsoon season and small variations within the monsoon season. Spatially, considerably higher sedimentation fluxes were detected in nearshore sites (T1 and T3) and attributed to wind-induced resuspension. Vertically, resuspension is also an important factor that influences the sedimentation process, which leads to an exponential increase of the budget from the surface to the bottom layer. Autochthonous carbonate deposition rates presented a similar seasonal pattern, with the total sedimentation rates under the influence of the water balance. Low values occurred during the monsoon season due to dilution while deposition rapidly increased during the early post-monsoon season when the lake level decreased. Intensive carbonate deposition also occurred during the non-monsoon season, which dominated the lake hydrochemistry dynamics.

Sequence stratigraphy of deep-water systems

Abstract Stratigraphic cyclicity in the deep-water setting reflects the interplay of accommodation and sedimentation on the shelf, which controls shoreline trajectories, sediment supply to the shelf edge, and the timing of all elements of the sequence stratigraphic framework. Stratigraphic trends defined by changes in the types, volume, and composition of gravity flows during the shoreline transit cycles on the shelf provide the diagnostic criteria for the identification of deep-water systems tracts and bounding surfaces. Non-diagnostic variability in the sedimentological makeup of systems tracts reflects the unique tectonic and depositional settings of each sedimentary basin, and needs to be rationalized on a case-by-case basis. Contour currents may further modify the sedimentological makeup of deep-water sequences, but do not provide diagnostic elements for the definition of systems tracts and bounding surfaces. The application of sequence stratigraphy to the deep-water setting relies on the construction of composite profiles that illustrate the relative chronology of the different types of gravity-driven processes at regional scales. The cyclicity relevant to the definition of sequences is described by the composite rather than local profiles. The place of accumulation of depositional elements depends on the location of sediment entry points along the shelf edge, the types of gravity-driven processes, and the seafloor morphology. The allocyclic and/or autocyclic lateral shifts of deep-water depositional elements further enhance the offset between local trends and the regional composite profile in terms of timing and frequency of cycles, timing of coarsening- and fining-upward trends, and timing of the coarsest sediment. The sedimentological cycles defined by local trends must not be confused with the stratigraphic cycles defined by regional composite profiles.

Scale in sequence stratigraphy

Abstract Stratigraphic cyclicity can be observed at different scales. At each scale of observation (i.e., hierarchical level), the building blocks of the sequence stratigraphic framework are represented by sequences and their component systems tracts and depositional systems. At the smallest stratigraphic scales, systems tracts and component depositional systems consist solely of sedimentological cycles (i.e., beds and bedsets). At any larger scales, systems tracts and depositional systems consist of lower rank stratigraphic cycles (i.e., sequences). The stacking pattern of sedimentological cycles defines the lowest rank systems tracts, which are the smallest stratigraphic units of a sequence stratigraphic framework. The scale of the lowest rank systems tracts at any location defines the highest stratigraphic resolution that can be achieved, and the limit between sedimentology and stratigraphy sensu stricto. The formation of depositional systems, and implicitly of systems tracts, requires typically minimum timescales of 102 yrs, and it may be sustained for as long as the defining environments are maintained as dominant sediment fairways. Within the transit area of a shoreline, where changes in depositional environment are most frequent, only the lowest rank depositional systems consist strictly of process-related facies accumulated in specific environments; these depositional systems sensu stricto develop commonly at scales below the resolution of seismic stratigraphy. At larger scales (higher hierarchical ranks), depositional systems sensu lato reflect dominant depositional trends, but may record higher frequency changes in depositional environment. The distinction between depositional systems sensu stricto and sensu lato becomes less meaningful outside of the shoreline transit area, where stratigraphic cyclicity may develop without changes in depositional environment. High-frequency sequences are commonly observed at scales of 100–101 m and 102–105 yrs, which defines the scope of high-resolution sequence stratigraphy. The stacking pattern of high-frequency sequences defines depositional systems and systems tracts of higher hierarchical ranks in lower resolution studies.

Discrimination between wave‐ravinement surfaces and bedset boundaries in Pliocene shallow‐marine deposits, Crotone Basin, southern Italy: An integrated sedimentological, micropalaeontological and mineralogical approach

AbstractThe lower Pliocene Belvedere Formation, cropping out in the Crotone Basin, southern Italy, exhibits a metre‐scale to decametre‐scale shallow‐marine cyclicity that shares features of both high‐frequency sequences linked to shoreline shifts and controlled by minor relative sea‐level and/or sediment supply changes, and sedimentological cycles unrelated to shoreline shifts. In order to better understand the high‐frequency sequence stratigraphic framework of this succession, an integration of sedimentological, micropalaeontological (micro‐foraminifera assemblages) and mineralogical (heavy mineral abundance) data is used. From a sedimentological/stratigraphic point of view, wave‐ravinement surfaces bounding high‐frequency sequences, and associated substrate‐controlled ichnofacies, are prominent in outcrop and document environmental and water‐depth changes, whereas bedset boundaries separating sedimentological cycles have a more subtle field appearance and are only associated with changes of environmental energy. Moreover, condensed deposits are present only above wave‐ravinement surfaces, and the high‐frequency sequences bounded by these surfaces have a thickness that is an order of magnitude greater than that of the bedsets. Micro‐foraminifera assemblages may change, and the content of heavy minerals usually increases, across wave‐ravinement surfaces, whereas both parameters do not change significantly across bedset boundaries. The abundance of heavy minerals is systematically higher, with respect to the underlying and overlying deposits, in the condensed shell beds that overlie wave‐ravinement surfaces. An integrated sedimentological, micropalaeontological and mineralogical approach represents a powerful tool to discriminate between wave‐ravinement surfaces bounding high‐frequency sequences and bedset boundaries, and in general to investigate at the intra high‐frequency sequence scale. This integrated approach is expected to be very useful in the study of potentially all shallow‐marine successions composed of small‐scale cycles, in order to delineate a detailed sequence stratigraphic framework and understand the factors that controlled the cyclicity.

The link between tectonics and sedimentation in asymmetric extensional basins: Inferences from the study of the Sarajevo-Zenica Basin

The coupled tectonic and depositional history of extensional basins is usually described in terms of stratigraphic sequences linked with the activity of normal faults. This depositional-kinematic interplay is less understood in basins bounded by major extensional detachments or normal fault systems associated with significant exhumation of footwalls. Of particular interest is the link between tectonics and sedimentation during the migration of normal faulting in time and space across the basin. One area where such coupled depositional-kinematic history can be optimally studied is the Late Oligocene - Miocene Sarajevo-Zenica Basin, located in the Dinarides Mountains of Bosnia and Herzegovina. This intra-montane basin recorded Oligocene – Pliocene sedimentation in an endemic and isolated lake environment. We use field kinematic and sedimentological mapping in outcrops correlated with existing local and regional studies to derive a high-resolution evolutionary model of the basin. The novel results demonstrate a close correlation between moments of normal faulting and high-order sedimentological cycles, while the overall extensional basin was filled by a largely uni-directional sediment supply from the neighbouring mountain chain. The migration in time and space of listric NE-dipping normal faults was associated with a gradual shift of the sedimentological environment. Transgressive-regressive cycles reflect sequential displacements on normal faults and their footwall exhumation, defining a new sedimentological model for such basins. This Early - Middle Miocene extension affected the central part of the Dinarides and was associated with the larger opening of the neighbouring Pannonian Basin. The extension was preceded and followed by two phases of contraction. The Oligocene - Early Miocene thrusting took place during the final stages of the Dinarides collision, while the post-Middle Miocene contraction is correlated with the regional indentation of the Adriatic continental unit. This latter phase inverted the extensional basin by reactivating the inherited basal listric detachment.

Sedimentological and Paleoclimate Modeling Evidence for Preservation of Jurassic Annual Cycles in Sedimentation, Western Gondwana

Abstract The Lajas Formation in the Neuquén Basin, Argentina, consists of a succession of mainly deltaic deposits. In the Middle Jurassic (170 million years ago), the basin was in western Gondwana roughly at the same paleolatitude as its present location (32°–40°S). Decimeter-scale, interbedded, coarser-grained and finer-grained beds in channelized and nonchannelized deltaic deposits have been interpreted as a product of variability in river discharge. The coarser-grained sandstone beds have erosional bases and contain mudstone clasts; internal cross bedding is commonly directed paleoseawards. These beds are interpreted as deposition during river-flood conditions. In contrast, the finer-grained beds are composed of interlaminated sandstone and mudstone, deposited during interflood periods. Bidirectional ripples and millimeter-scale sand–mud laminae suggest the influence of tides. This sedimentological evidence raises the question of whether these cycles represent annual variability in fluvial input. To answer this question, a simulation using the Fast Ocean Atmosphere Model for the Middle Jurassic was run to equilibrium. The model shows that the paleoclimate of the Neuquén Basin was characterized by a strong seasonal cycle, with a wet winter and a dry summer. Model runs suggest that February mean temperatures were 28°C with 4-mm precipitation (±4 mm standard deviation) per month, whereas August mean temperatures were 8°C with 34-mm precipitation (±17 mm standard deviation) per month. The strong seasonal cycles in the simulation, representing 24% of the variance in the precipitation time series, suggest that the sedimentological cycles represent annual variations. The simulation also suggests a Middle Jurassic climate where increased seasonality of precipitation occurred farther poleward than previously thought.

Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: The state of the art

AbstractTraditionally, fresh water carbonate research has focused on the sedimentology and palaeontology of ancient lacustrine deposits. Lithofacies in such low‐energy deposits are typically fine‐grained, developed uniformly in a generally concentric distribution (‘bulls‐eye’ pattern) and are predictable even when preserved imperfectly. In contrast, because of their local lithofacies and palaeontological complexities, fluvial carbonates were either delegated to a status of ‘minor geomorphological features’ or barely considered prior to the 1970s. This viewpoint was based on the depositional record of fluvial and spring‐fed fresh water carbonates, which were considered to be restricted generally to localized karstic areas. Such deposits are often preserved as scattered patches of ambient temperature tufa. Occasionally, however, in active tectonic areas, localized travertine deposits are also developed from deeply circulating hydrothermal waters. With a few exceptions (for example, basins with high subsidence rates or in arid climate zones), these fresh water carbonates are prone to erosion from continuing river incision and thus may not be preserved in the geological record. A partial record of fluvial and spring‐deposited carbonates is often preserved in Quaternary deposits, but the record in older deposits is typically fragmentary and often diagenetically modified. Yet once their unique facies architecture (and specialized nomenclature) is understood, these carbonates provide an important record of past sedimentological cycles of great value in palaeoenvironmental landscape modelling. The emphasis of modern research is to acquire information that explains how active systems function. In this respect, tufas reveal much of how carbonate precipitation is a shared product of physico‐chemical and microbiological biomediation processes. Likewise, travertines not only show an intimate interrelation with active tectonism but also hold great potential as monitors of past volcanic carbon dioxide emissions. In addition, both tufas and travertines contain palynological records that can be used as proxy indicators of climate change. Perhaps no other field of sedimentology has witnessed more developments and applications over such a brief period of study.

Stratigraphy, paleogeography and paleoclimates of the Pleistocene in the north of European Russia

The research of the Quaternary in the north of European Russia has been made by using lithological methods for studying composition of deposits and also paleobotanical and paleozoological remains. It allowed to reconstruct landscapes and climates during the Neopleistocene and to establish the stages of environmental history which correspond to sedimentological cycles in the Quaternary sequence. Glaciation centers are identified for different Pleistocene epochs based on lithological criteria. The general tendencies in spatial and temporal variability of the glacial beds composition of different ages were revealed. This allows correlating the glacial deposits. Paleogeography and climatic conditions during interglacial epochs of the Middle–Late Pleistocene and Holocene were reconstructed. Variations in vegetation development, temperature and humidity were found for the first time in Timan-Pechora-Vychegda, Arkhangel’sk and Vologda regions. A conclusion is made about the tendency of climate cooling in the north of European Russia during the Pleistocene.

Carboniferous and Lower Permian sedimentological cycles and biotic events of South China

Abstract The sedimentary successions and four fossil groups, including rugose corals, brachiopods, fusulinaceans and conodonts, from the Carboniferous and Lower Permian of South China have been studied in order to reveal the sedimentary characteristics and evolutionary pattern of main biological groups in the East Tethyan region during the Late Palaeozoic Ice Age. The Lower Carboniferous lithology of South China is diverse, ranging from basinal and shelf carbonate rocks to coal measures and continental clastics, while the Upper Carboniferous and Lower Permian are composed mostly of shallow-marine carbonates. From uppermost Devonian to Lower Carboniferous, five major regression events are recognized at the topmost Devonian, middle and upper Tournaisian boundary, Tournasian–Viséan boundary, uppermost Viséan and the Mid-Carboniferous boundary in South China, separately. The Upper Carboniferous and Lower Permian shallow-water carbonate rocks consist of remarkable, high-frequency cyclothems. Moreover, another major sea-level fall is recognized and characterized by an extensive sedimentary hiatus at the Sakmarian–Artinskian boundary throughout South China. All of the sedimentary basins of South China were formed in extensional tectonic settings during this time; thus, multiple regressive events that occurred throughout South China should be primarily induced by glacio-eustatic drawdown. In addition, two biotic events characterized by a remarkable decline in the diversity of benthic biota and a turnover in the composition of fossil assemblages occurred, respectively, at the Mid-Carboniferous and Sakmarian–Artinskian boundaries, consistent with two major regressions, and were probably caused by the glaciations in Gondwana.

High-resolution record of tectonic and sedimentary processes in growth strata

Growth strata are used to determine the kinematics of synsedimentary structures such as faults. Classical methods of analysis such as thickness versus throw plot consider that the available space created by fault slip in the hanging wall of faults is instantaneously filled up by sediments. This has lead many previous works to identify a cyclic activity for growth faults. Here we perform a careful analysis of the variation of strata thicknesses on each side of a very well documented normal growth fault in the Niger delta. We show that these thickness variations are induced by the alternation of sedimentary processes during continuous fault slip. Suspended-load processes induce either uniform or slightly variable thickness of a large majority of mudstone layers. Bedload processes result in a preferential thickening of sand layers in the hanging wall. These high quality data thus provide strong grounds for doubting the polycyclic growth diagnosed for some faults at the scale of sedimentary cycles and supports the notion that fault displacement rates can be very well behaved. Our study emphasizes the important conclusion that stable fault growth, and related displacement rates, can appear to be punctuated when viewed at the scale of sedimentary cycles. It follows that care should be taken when attempting to derive displacement rates on temporal scales equivalent to those of alternating sedimentological cycles.

Late Quaternary geohistory of Sárrét Basin, based on studies on core Sárrét-2, Hungary

The Sárrét marshland is situated along the northeastern foothills of the Bakony Mountains, along a NE-SW-trending neotectonic zone. Investigation of the marshland and the reconstruction of its evolution are especially interesting to compare to the present and the expected future stage of Lakes Balaton and Velence. Based on the sedimentological characteristics of the core sequence and the geochemical, physical, and mineralogical composition of the layers, three sedimentological cycles could be separated. The three cycles represent the most important evolutionary phases of lake formation: flourishing and progressive aging. First, a nutrient-poor, open-water lake existed, where clastic sediments (sand and silty clay) were deposited. During the second phase, phytoplankton-produced autogenic lime mud was deposited in the progressively more eutrophic water. Peat accumulation during the third stage indicates the marsh phase of the lake.The results suggest that the studied sequence developed from Late Glacial to Middle Holocene. According to radiocarbon dating the accumulation rate in Sárrét (Sümegi, this volume) corresponds to the sedimentation rates in the Tapolca Basin and Lake Balaton.

South Kavala Gas Field - Taphrogenetic Prinos Basin

The South Kavala gas field located at the southwest edge of the Prinos basin was discovered at the turn of 1972 -73. The basin formation started in the middle Miocene with continental deposits. Later on the sea transgressed all over the basin until the south Kavala ridge at the southern limit lifted up and transformed it to a lagoon, leading to the formation of Evaporites in upper Miocene time. At Pliocene the sea dominated again covering even the previous mentioned ridge. An unconformity exists between Miocene and Pliocene visible mainly on the basin flanks. The trapping mechanism is a combination of a roll-over anticline in front of a northeast - southwest syngenetic fault and a pinch - out of the sediment deposits to the southwest towards the South Kavala ridge. The basement itself forms an erosional high. The gas reservoir is found between two evaporitic horizons and consists mainly of sandstone, microconglomeratic alternating with shale and marl. It is of turbiditic origin forming sedimentological cycles. Individual facies A4/B2, C and E representative of the turbidite facies classification of Walker and Mutti (1973) have been recognised. The net pay thickness is small and amounts up to eleven meters. The gas consists 83% of methan, 7.5% of ethan, 1.5% of propan and around 1.5% of butan. It is free of H2S and contains condensate. As source rocks are considered the under continental and marine conditions deposited preevaporitic shales. The coal beds are also considered to be potential source rocks. The gas is of low maturity and its generation started during latest Miocene and continued through the Pliocene. The main migrations paths apparently were along the faults that cross the basin. The in place reserves are close to 1.109m3 αερίου. The field is on production from 1981 and 80% of the recoverable reserves have been already produced.

Ludlow (late Silurian) oceanic episodes and events

Biotic and sedimentological cycles in the late Silurian are closely similar to those recognized in the early Silurian. They are explained here by alternations between primo and secundo conditions, the former being characterized by cold dense oceanic bottom waters and high nutrient supply, and the latter by salinity-dense bottom waters and diminished nutrient supply. The lithological pattern, together with the turnover of conodont faunas and of other fossil groups, permits the identification of a sequence of episodes and events in the Ludlow following the Klinte Secundo Episode, which developed in the latest Wenlock: The Sproge Primo Episode, the Linde Event, the Etelhem Secundo Episode, the Havdhem Primo Episode, the Lau Event, the Hoburgen Secundo Episode and the Klev Secundo–Primo Event, continuing into the earliest Přídolí. Testing of this model against others that invoke a primary sea-level control is marred by the current imprecisions of biostratigraphical correlation.

Wenlock (Silurian) oceanic episodes and events

Biotic and sedimentological cycles in the Wenlock are related to episodic changes in oceanic state. These may be explained by alternations between primo and secundo conditions, the former being characterized by cold oceanic bottom waters and high nutrient supply, and the latter by salinity-dense bottom waters and diminished nutrient supply. The lithological pattern, together with the turnover of conodont faunas and of other fossil groups, permits the identification of a sequence of episodes and events in the Wenlock, following the extinctions associated with the earliest Wenlock Ireviken Event: the Vattenfallet Secundo Episode, the Sanda Primo Episode, the Boge Event, the Lansa Secundo Episode, the Allekvia Primo Episode, the Valleviken Event, the Hellvi Secundo Episode, the Mulde Event and the Klinte Secundo Episode. The Mulde Event differs from others in separating two secundo episodes, and may represent an interval when deep waters remained saline and vertical circulation virtually ceased. The effects of the events and episodes were stronger in the early and late Wenlock than in the middle part of the epoch.

C-Isotope stratigraphy, a monitor of paleoenvironmental change: A case study from the early cretaceous

Today's disturbance of the global carbon cycle induced by anthropogenic processes has raised new interest in the history of the global carbon cycle and its relationship to climate and other geochemical cycles. Carbon-isotope stratigraphy proves to be most useful as a monitor of the history of the carbon-cycle during the last 200 million years. In the introductory paragraphs of this review the mode of functioning of the global carbon-cycle is summarized and the connection between carbon-cycle and carbon isotope geochemistry is documented. A case study on the disturbance of the global carbon cycle during the Aptian-Albian is presented. The disturbance of the carbon cycle lasting up to millions of years is recorded in the carbon-isotope stratigraphy of pelagic sediments. It is superimposed on high frequency sedimentological cycles, related to climate and oceanographic cycles of 20, 40 or 100 ky duration. The data reviewed suggest that the change in the global carbon system was linked to a global acceleration of geochemical cycles triggered by a long-term change in atmospheric CO2 controlled by the rate of sea-floor formation and by volcanic activity. Increased accumulation rates of terrestrial material and terrestrial organic matter in marine sediments may be used as an indicator of an intensified hydrological cycling resulting in higher water-discharge rates. An intensification of the Aptian-Albian water cycle is further reflected in continental sediments monitoring a period of elevated humidity. An increase in water discharge rates should have affected the transfer rate of dissolved nutrients from continents to oceans. Elevated concentrations of phosphorus may have led to an increase in Aptian-Albian oceanic productivity enhancing the transfer of marine organic matter from the oceanic into the sedimentary reservoir. Increased productivity, increased bulk sedimentation rates and poorly oxygenated deep-water led to increased preservation of marine and terrestrial organic matter in marine sediments. The accelerated output of marine organic carbon from the oceanic reservoir is ultimately registered in the positive carbon-isotope excursion of the marine carbonate carbon-isotope stratigraphy.