Depositional Record最新文献

Injection of treated wastewater into the shallow subsurface on islands and along coastlines is a common practice in areas like the Florida Keys, yet little is known about the fate of contaminants after injection. The strong chemical contrast between typically well-aerated, nitrate-rich and low-density wastewater and anoxic, higher-density, low-nutrient, saline groundwater creates a dynamic environment demonstrably leading to buoyancy-driven flow and microbial transformation. Whether injected wastewater discharges to surface waters and leads to their impairment depends on the efficiency of mixing and biogeochemical reactions in the subsurface. This study demonstrates that nitrate concentrations are significantly reduced through these processes at a study site on Vaca Key (Marathon), FL, USA. However, wastewater tracers and wastewater-derived nutrient nitrogen are found at wells adjacent to Florida Bay. This study, together with previous work on the fate of wastewater phosphate, can inform decision-making about the need for alternative wastewater disposal methods in the Florida Keys and elsewhere, where considerations of whether shallow injection is the functional equivalent of direct discharge of treated wastewater to coastal waters is a pressing issue.

Emblematic of global coral-reef ecosystem decline, the coral ecosystem-engineer Acropora palmata is now rare throughout much of the western Atlantic. Understanding when and where this foundation species occurred during the past can provide information about the environmental limits defining its distribution through space and time. In this paper, the present, historical and newly dated geological records of A. palmata are compared to reveal novel insights into the environmental constraints on its occurrence in Dry Tortugas National Park, a subtropical reef system at the south-western terminus of the Florida reef tract. Although past geological investigation found little evidence of the species in the park, a single, moderately sized A. palmata reef existed throughout historical times (1881 Common Era [CE] to present day; ‘historical population’, termed herein). Over the last 140 years, repeated population declines occurred with little to no recovery, culminating in the extirpation of A. palmata from the area during the 2023–2024 CE global coral bleaching event. Reported here for the first time is a significant record of Late Holocene A. palmata populations that existed from ca 4500 to 375 years before present (‘Late Holocene population,’ termed herein) in three broadly distributed areas of the shallow Dry Tortugas platform. This discovery challenges previous assumptions regarding the species' limited contribution to reef development in the area by providing data that extend the known spatial and stratigraphic extent of Holocene populations in this location. It is posited that, although the Late Holocene climate largely suppressed regional reef development, the new records provide evidence for centennial-scale periods of more favourable and stable climate that allowed for short-term expansions of A. palmata populations in the Dry Tortugas. In conclusion, the species' prospects for future success in this and other subtropical locations is discussed given the observed global trends of increasing sea-surface temperatures.

The Joulters ooid sandbody of northern Great Bahama Bank is a vast expanse (on average, 4 m thick over ca 400 km²) of muddy ooid sands partly rimmed by clean ooid sands. Knowledge of the development of depositional and localised diagenetic patterns in the Joulters example has forwarded our general understanding of carbonate sedimentology, stratigraphy and diagenesis, and in so doing provides valuable insight into an interpretation of ancient accumulations. The strength of the Joulters example as an analogue for ancient carbonate sand accumulations comes from the combined view of satellite imagery, surface facies mapping, extensive sediment coring and rock coring of a key island. Ooids form in current-swept areas with dynamic morphology and can accumulate in conditions quite different from those in which they were generated, as is much better displayed in Joulters than in other modern examples from the Bahamas and elsewhere. Results summarised herein are a calibration of some of these modes of accumulation focussing on key sedimentologic characteristics. The importance of the sandbody as an analogue for outcrop and subsurface studies is considered in this review as Joulters illustrates the strike-elongated nature of carbonate sand deposits relative to the platform margin, lateral variability that is inherent in such depositional systems due to sand flats and tidal channels, and complexity that is added by beach/island complexes.

Earth observing satellites offer a way of viewing large-scale, high-volume transport events (storms) in global carbonate systems as well as monitoring the quiescent intervals between events. In particular, the processes leading to the facies transitions seen from bank top to deep slope are revealed in a way not seen before. In this paper we provide, for the first time, a comprehensive discussion on the large-scale transport processes dominating this interval in examples from the western Tropical Atlantic, the northern shelf of Australia and the carbonate plateaus of the Coral Sea. Our findings indicate that (a) tropical cyclones are the dominant transport mechanism that transports carbonate sediments to the deep sea, particularly fine-grained sediments; (b) the largest carbonate sediment transport events occur when tropical cyclones interact with shallow carbonate shelves; and (c) sufficient observations have taken place in this period to allow the compilation of preliminary regional climatologies to estimate storm impact and frequency. The recently achieved unprecedented current state of satellite remote sensing, combined with focused research efforts, can enable markedly improved quantification of this important aspect of oceanic carbonate production, deposition and dissolution.

A limestone cave filled with montmorillonite clay was found in a hill above the karst plateau on the north-eastern edge of the Adriatic Sea. The cave fill shows no correlation with sediments found in the surrounding caves or other known caves of the Classical Karst, where montmorillonite content is negligible. In other caves, the primary deposited sediments originate from weathered Eocene flysch and were transported into caves by sinking streams. Powder X-ray diffraction analyses indicate a pure montmorillonite composition with a few coarser quartz grains and heavy minerals. Based on these results and comparisons with tephras from volcanic centres in the wider region, we conclude that the geochemical characteristics of the montmorillonite clay (rare earth element distribution, enriched patterns of light rare earth elements, LaN/YbN ratios and significantly negative Eu/Eu* ratio) are similar to weathered volcanoclastic material of the Smrekovec Volcanic Complex (Oligocene to Miocene eruptions in north-eastern Slovenia) and transported to the depositional centre by north-eastern winds. Dating the clay using apatite fission-track thermochronology yielded 22 ± 7 Ma, while K-Ar dating gave 23.4 ± 1.7 Ma. Both ages are consistent with the activity of the Smrekovec Volcanic Centre, previously dated to 28–23 Ma. The presence of weathered volcanic ash in the studied cave indicates considerable explosive activity of the stratovolcano, previously interpreted only as a submarine edifice, and confirms the existence of a contemporary karst landscape at the time of volcanic activity where volcanic ash was deposited and subsequently in situ weathered in a levelled corrosion-tectonic plane. Consequently, it can be concluded that a karst landscape in the north-western Dinarides has existed since the Late Oligocene, with the studied cave being the only known remnant identified so far. This study presents a rare sedimentary record and highlights the role of karst landscapes as valuable archives of past geological events and environmental changes.

Lakes are sensitive indicators of the balance between accommodation and sediment supply, recording high-resolution changes in palaeoenvironmental conditions. Long-lived rift lake basins, however, are predominantly controlled by episodic accommodation changes and pronounced basinward facies shifts, complicating the generalisation of tectonic and climatic controls on rift lake successions. This study proposes a sequence framework and depositional pattern for asymmetric half-grabens in syn-rift lake basins by characterising the lacustrine fan-delta deposits of the Lower Cretaceous Shahezi Formation in the Songliao Basin. Detailed sedimentologic and petrographic analyses identified 24 lithofacies categorised into seven facies associations. A sequence stratigraphic framework was constructed to outline the tectono-stratigraphic evolution during the syn-rift phase. The results indicate that the syn-rift Lishu palaeo-lake is characterised by its relatively small size, steep slopes, poorly developed and siliciclastic-dominant shoreline strata and significant input of allochthonous biodetritus. The syn-rift deposits show a distinct threefold conglomerate–sandstone–mudstone motif, with a complete cycle comprising a prolonged retrogradational phase (LST and TST) and a brief progradational phase (HST). Basin-bounding faults accelerated hinterland erosion and increased sediment feeder system slopes by rotating hangingwall blocks; consequently, rapid sediment transport and localised gravitational collapse caused the common occurrence of soft-sediment deformation structures and sublacustrine fan conglomerates. The substantial increase in accommodation space, resulting from fault-generated subsidence, triggered lake expansion and further contributed to the development of transgressive system tracts and continuous mudstone deposition. These mudstones, rich in terrigenous organic matter and allochthonous fossils, correlate with carbonaceous mudstones, coals and conglomeratic sandstones in proximal overfilled sections, indicating a dynamic interplay between fan delta progradation and Lake Shoreline transgressions. This study proposes a depositional model within a sequence stratigraphic framework for non-marine sediment accumulation in asymmetric half-grabens bounded by active faults. The findings offer insights that complement existing models developed for marine rift systems.

We very much appreciate the comments of André; Pestilho and Agustin Mors on our paper discussing the early diagenesis of the Pre-salt carbonates (Barra Velha Formation, BVF) in the Santos Basin (Gomes et al., 2024). We welcome the opportunity to respond and to clarify our interpretations concerning dolomite formation, diagenetic timing and isotopic signatures supported by additional examples.

The Upper Permian Castile Formation of the Delaware Basin is a 515.3 m (1690.6 ft) thick deep-water laminated evaporitic sequence dominated by anhydrite and halite. This formation seals hydrocarbon reservoirs and produced-water injection targets, and holds potential for salt cavern development due to its halite-bearing intervals. This study presents a sedimentological characterisation of two cores from the basin's centre and margin, complemented by a suite of petrographic and geochemical analyses, including X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, inductively coupled plasma mass spectrometry for halides and X-ray fluorescence for sulphates. These analyses facilitated evaporite characterisation and helped to establish a threefold hierarchical scheme (laminite, cycle, member) and advanced understanding of halite precipitation dynamics in deep brines. Additionally, intense dolomitisation and pore-filling sulphates were examined along the older carbonate margin, linking these processes to deep-water brine reflux events of varying ages and salinities. Pre-Castile dolomitisation enhanced permeability along the marginal strata, allowing the reflux of hypersaline deep brines outside the basin. This reflux promoted sulphate precipitation in porous dolostones along the margins (anhydritisation), leading to prolonged sulphate precipitation stages within the basin. Once marginal porosity was occluded, brine confinement led to further salinity increases, driving episodic halite deposition and producing five anhydrite–halite members. Based on this study, it is possible to conclude that dynamic deep hypersaline brines significantly influence sedimentary and diagenetic processes in the basin and its margins. Dynamic deep hypersaline brines are key in influencing sedimentary and diagenetic processes in the basin and its margins.

The western Taiwan foreland basin (WTFB) is a classical peripheral foreland basin longitudinally bounded by the East China Sea (ECS) to the north and the South China Sea (SCS) to the south. Sediments spill longitudinally into the nearby marginal ocean basins, similar to the typical foreland basin setting. Due to oblique collision in the Taiwan region, the WTFB has evolved into two subbasins: a mature basin dominated by fluvial sediments in central-northern Taiwan and an immature one dominated by deep marine facies offshore south-western Taiwan, accompanied by two distinct sediment routing systems. In the north, the Choushui River drainage, narrow seaway of the Taiwan Strait, Huapingshu Channel/Mienhua Canyon System and southern Okinawa Trough (SOT) are integrated into a united sediment dispersal system, allowing sediments sourced by the mature basin to laterally overflow into the ECS and be deposited into the SOT. In southern Taiwan, the Kaoping River drainage, Kaoping submarine canyon, Penghu submarine canyon, deep-sea Penghu Channel and SCS basin interconnect, forming a longitudinal dispersal system for sediments mainly derived from the southern Taiwan orogen to be longitudinally transported to the northern SCS basin and the northernmost Manila Trench. The oblique collision between the Luzon Arc and the Chinese margin in the Taiwan region is the major factor in the development of two distinct sediment dispersal systems. Preferential sediment transport (axial vs. transverse), shelf width and sea-level change since the Last Glacial Maximum (~2 ka BP) are the other significant factors in the development of sediment routing systems in the WTFB. The two proposed distinct sediment dispersal systems in the WTFB clearly demonstrate how foreland basin sediments can be transferred longitudinally to adjacent marginal sea basins. Moreover, the sediment dispersal systems in the WTFB can be considered a modern analogue for interpreting ancient counterparts.