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The marine record of the Triassic–Jurassic boundary interval has been studied extensively in shallow-marine successions deposited along the margins of Pangea, particularly its Tethyan margins. Several of these successions show a facies change from carbonate-rich to carbonate-poor strata attributed to the consequences of igneous activity in the Central Atlantic Magmatic Province (CAMP), which included a biocalcification crisis and the end-Triassic mass extinction. Evidence for a decline in calcareous and an increase in biosiliceous sedimentation across the Triassic–Jurassic boundary interval is currently limited to the continental margins of Pangea with no data from the open Panthalassan Ocean, the largest ocean basin. Here, we present a facies analysis of the McCarthy Formation (Grotto Creek, southcentral Alaska), which represents Norian to Hettangian deepwater sedimentation on Wrangellia, then an isolated oceanic plateau in the tropical eastern Panthalassan Ocean. The facies associations defined in this study represent changes in the composition and rate of biogenic sediment shedding from shallow water to the outer ramp. The uppermost Norian to lowermost Hettangian represent an ∼ 8.9-Myr-long interval of sediment starvation dominated by pelagic sedimentation. Sedimentation rates during the Rhaetian were anomalously low compared to sedimentation rates in a similar lowermost Hettangian facies. Thus, we infer the likelihood of several short hiatuses in the Rhaetian, a result of reduced input of biogenic sediment. In the Hettangian, the boundary between the lower and upper members of the McCarthy Formation represents a change in the composition of shallow-water skeletal grains shed to the outer ramp from calcareous to biosiliceous. This change also coincides with an order-of-magnitude increase in sedimentation rates and represents the transition from a siliceous carbonate-ramp to a glass ramp ∼ 400 kyr after the Triassic–Jurassic boundary. Sets of large-scale low-angle cross-stratification in the Hettangian are interpreted as a bottom current–induced sediment drift (contouritic sedimentation). The biosiliceous composition of densites (turbidites) and contourites in the Hettangian upper member reflects the Early Jurassic dominance of siliceous sponges over Late Triassic shallow-water carbonate environments. This dominance was brought about by the end-Triassic mass extinction and the collapse of the carbonate factory, as well as increased silica flux to the ocean as a response to the weathering of CAMP basalts. The presence of a glass ramp on Wrangellia supports the hypothesis that global increases in oceanic silica concentrations promoted widespread biosiliceous sedimentation on ramps across the Triassic to Jurassic transition.

Turbidity currents transport vast amounts of sediment through submarine channels onto deep-marine basin-floor fans. There is a lack of quantitative tools for the reconstruction of the sediment budget of these systems. The aim of this paper is to construct a simple and user-friendly model that can estimate turbidity-current structure and sediment budget based on observable submarine-channel dimensions and general characteristics of the system of interest. The requirements for the model were defined in the spirit of the source-to-sink perspective of sediment volume modeling: a simple, quantitative model that reflects natural variability and can be applied to ancient systems with sparse data availability. The model uses the input conditions to parameterize analytical formulations for the velocity and concentration profiles of turbidity currents. Channel cross section and temporal punctuation of turbidity-current activity in the channel are used to estimate sediment flux and sediment budget. The inherent uncertainties of geological sediment-budget estimates motivate a stochastic approach, which results in histograms of sediment-budget estimations, rather than discrete values. The model is validated against small-scale experimental turbidity currents and the 1929 Grand Banks turbidity current. The model performs within acceptable margins of error for sediment-flux predictions at these smallest and largest scales of turbidity currents possible on Earth. Finally, the model is applied to reconstruct the sediment budget related to Cretaceous slope-channel deposits (Tres Pasos Formation, Chile). The results give insight into the likely highly stratified concentration profile and the flow velocity of the Cretaceous turbidity currents that formed the deposits. They also yield estimates of the typical volume of sediment transported through the channels while they were active. These volumes are demonstrated to vary greatly depending on the geologic interpretation of the relation between observable deposit geometries and the dimensions of the flows that formed them. Finally, the shape of the probability density functions of predicted sediment budgets is shown to depend on the geological (un)certainty ranges. Correct geological interpretations of deep marine deposits are therefore indispensable for quantifications of sediment budgets in deep marine systems.

Seismic-scale continuous exposures of an Early Jurassic carbonate platform located in the southern High Atlas of Morocco provide detailed quantitative information about the lithofacies and stratal geometries of an aggrading, retrograding, and prograding steeply inclined slope system that evolved in an active intracratonic rift basin. Aggradational, backstepping, and progradational outer-platform to slope transects are each characterized by distinct lithological features and stratal patterns. A digital outcrop model was constructed using real-time kinematic global positioning system and lidar, storing information on recorded stratal surfaces including lithofacies information. From these data 3D models of the slope system could be built. In the study area, four stages of slope development are recognized. Stage 1 corresponds to a low-relief carbonate platform characterized by widespread sub-wave-base depositional conditions. Stage 2 developed as an aggrading to retrograding platform, during which the platform built considerable relief. In addition, a massive organically bound upper slope fringe formed, dominated by coral–sponge–microbial boundstone. The in situ boundstone consisted of irregular wedges that accreted on the upper slope down to ~ 140 m below the platform break. After a period of sediment starvation Stage 3 involved a major backstepping of sediment deposition. Seventy-meter-high clinoforms prograded from the center of the platform across the platform top until reaching the relict platform break (of Stage 2). Subsequently, progradation occurred basinward, as indicated by the spilling of lobes down the existing slope deposits of Stage 2. Limited progradation, along with the reestablishment of the in situ coral–sponge–microbial boundstone on the upper slope, led to the progressive steepening of the slope profile to dips of 23°. Clinoforms are planar in the upper part of the slope, and concave upwards in the lower part; with a total relief of over 460 m. Stage 4 is observed only in the lower slope and adjacent basin. Coarse detrital carbonate deposits form lens-shaped aprons that grade basinward into kilometer-scale lobes that alternate with thick wedges of basinal fallout sediments. Syndepositional extensional faults operating in the subsurface affected sedimentation along the lower slope profile throughout the four stages and are expressed in the stratal patterns through growth strata in monoclinal folds. Three-dimensional digital outcrop models reconstructing the architecture of the slope system allowed quantification of slope geometries and stratal relationships and spatial distribution of sedimentary bodies. The digital model enhanced the understanding of the depositional changes during slope evolution and also led to observations on, for example, angular relationships that would have been difficult to detect without the digital approach. The evolution from aggrading to retrograding, prograding, and retrograding was strongly influenced by synsedimentary tectonics within an intracratonic rift basin. The tectonics generated irregular distribution of accommodation space, variably interfering with eustatic sea-level movement. This in combination with the character of lithofacies types and style of sedimentary processes along the slope, such as in situ boundstone growth and gravity-driven resedimentation processes, directly controlled carbonate slope architecture and stratigraphy of the Djebel Bou Dahar and influenced stratal anatomy and lithofacies distribution.

Red-stained platform facies are a common feature of many carbonate settings throughout the geological record. Although the mechanisms involved in red staining of subaerially exposed or argillaceous, peri-platform limestones are reasonably well understood, the environmental and oceanographic significance of red carbonates often remains uncertain. Here, sedimentological, sequence stratigraphic, geochemical, paleontological, and quantitative bathymetric data from Pennsylvanian red intervals across a well exposed carbonate platform top and slope are documented and interpreted in a process-oriented context. On the upper slope (80–350 meters below the shelf break), red intervals alternate with gray, mainly microbial algal boundstones. On the lower slope (350–600 meters below the shelf break), redeposited red-stained mud builds matrix-supported breccia tongues interbedded with predominantly redeposited, clast-supported carbonate debris. The presence of large volumes of fibrous calcite biocementstones as well as firmgrounds point to low sedimentation rates or omission. In terms of sequence stratigraphy, red intervals occur within maximum flooding intervals and reflect near platform drowning. Elevated δ18O values (2–3‰) and an essentially cool-water, heterotrophic biotic association in red intervals on platform top and slope suggest deposition during sea-level highs, associated with colder water masses and high nutrient levels. The most likely drivers are an elevated thermocline and upwelling. The red staining is the result of iron oxidation which occurred during early diagenesis, likely by iron bacteria. These red intervals provide an important bathymetric benchmark against which other (mainly Paleozoic) red facies can be tested and calibrated.

Two main types of karst formation are commonly known: the surficial meteoric one and the subsurface (hypogenic) karst, which can be related to both carbonic (H2CO3) and sulfuric (H2S) acids. This paper documents evidence for a third, CO2-regime related, type of karst that is less commonly described. Petrographic and geochemical properties of exhumed Pleistocene phreatic cave deposits from the diapiric Jabal Madar dome in northern Oman are documented and discussed in a process-oriented context. These calcites form at the interface between two fundamentally different diagenetic and hydrogeological domains: the deep-seated, hydrothermal and the near-surficial, meteoric-vadose one. Four calcite phases are recognized: (i) acicular, (ii) blocky to stubby elongated, (iii) proto-palisade, and (iv) macro-columnar calcites. The macro-columnar calcites, forming the last stage of precipitation, are conspicuous due to their cyclical red zonation, and they form the main (geochemical) focus of this study. Fluid inclusion data point to fluid temperatures of between 30 to 50°C (monophase liquid inclusions) and elevated salinities (1.6 to 7.3 wt.% NaCl equivalent). Low carbon-isotope data (−8 to −9‰) are in agreement with the influx of soil-zone CO2 whereas decreasing δ18O (−15‰) values might point to mixing of saline hydrothermal and 18O depleted, meteoric freshwater, i.e., two fluid sources. Trace-element and stable-isotope data shift between the different cement phases and vary cyclically across the red zoning in macro-columnar calcites. With respect to the intra-crystal variability, these patterns are perhaps best explained in the context of redox potential. Two interpretations are presented; the one favored here suggests that the cyclical red zoning in macro-columnar calcites is controlled by Pleistocene monsoonal climate patterns.

The turn of the millenium is for many of us an occasion to pause and consult the crystal ball. Sedimentary geologists have added incentive to do so because the calendar event coincides with a profound change in what one may call our professional hinterland, the part of society that requires our expertise and offers jobs. Sedimentary geology and its sister, paleontology, originated as historical sciences, dedicated to the study of the sediment record as a history book of the evolution of life and the changing environments at the Earth's surface. To this day, deciphering earth history remains a principal task of sedimentary geology and a source of major scientific contributions. However, increased quantitative understanding of geologic systems and societal demand have established prediction besides description as an increasingly important part of the natural sciences. Earth scientists are expected to deliver predictions of two sorts—prediction in the space domain, notably the inaccessible subsurface, and prediction in the time domain, the future behavior of the solid earth and its fluid envelopes. Sedimentary geologists are involved in both types of prediction. Exploring for resources such as petroleum, metallic ores, or drinking water as well as determining the spread of underground pollution requires mainly prediction in space. Predicting oceanic and atmospheric climate constitutes the principal task in the time domain. Prediction in time also includes catastrophic changes related to "energy bursts" of the solid Earth, such as earthquakes, volcanic eruptions, or landslides. As is typical for the natural sciences, work in sedimentary geology spans the full range from pure, curiosity-driven research to applied research driven by the demand of economies. Both pure and applied research may be relevant for society and may make fundamental contributions to knowledge. I will first discuss major challenges in pure research and then make a tour of the horizon …

The Aptian to Albian interval of the vast Arabian Platform was studied in northern Oman (Nahr Umr Formation) for its paleoceanographic and sea-level record. The sections indicate seven transgressive-regressive cycles overprinted by small-scale sea-level fluctuations. The peak of regression lead to emergence and exposure of the sea floor and overprinted marine hardground surfaces. The subaerial overprint of marine hardgrounds is difficult to recognize in the field. However, four independent lines of evidence document emergence. These are: (1) Pronounced negative excursions in carbon and partly in oxygen isotope composition beneath hardbottoms. They are attributed to the influx of light, soil-derived carbon and light oxygen from meteoric water. (2) Sparite-filled rudists beneath hardbottoms contain primary brackish-water fluid inclusions of very low salinity interpreted as cement precipitation in the phreatic marine/meteoric mixing zone or "pollution" of meteoric freshwater by residual salt. (3) Symbiont-bearing and thus light-dependent orbitolinids display small, conical morphotypes in the shallow, well illuminated water prior to exposure and hardbottom formation. Large, flat morphotypes are characteristic of the transgressive shales above those surfaces and document deeper, less illuminated waters. (4) The presence of mycorrhiza (Microcodium). The exposure surfaces overlie facies-incomplete shallowing-upward successions or subtidal sediments, but unequivocal evidence for erosion before or during emergence is lacking. Correlation of transgressive-regressive events in Oman with other sea-level curves suggests the record of spasmodic regional tectonism combined with a strong eustatic component.