Based on data presented in this study, the E-W–trending Alima anticline in the Metlaoui region of the southern Tunisian Atlas Mountains formed due to far-foreland, brittle deformation. The Alima anticline is one in a series of en echelon folds in the Atlas fold-and-thrust belt of North Africa. Geologic mapping indicates that the Alima anticline has a steep southern limb, a gently dipping northern limb, and pervasive normal fault sets. Fracture orientations suggest that fracturing occurred early in the fold history as a synfolding process, not as a pre- or postdeformational process. Gravity data show positive Bouguer anomalies near fold crests, not the negative anomalies that would be expected if the anticline were salt cored. Seismic data, collected along lines in basins surrounding the Alima anticline, suggest the presence of several high-angle reverse faults. Based on surface and subsurface studies, we attribute the development of the Alima anticline to far-foreland deformation associated with late Cenozoic contraction. N-S–directed elongation in the Triassic reoriented to NW-SE–directed shortening in the Miocene, causing Triassic normal faults to be reactivated as oblique-slip reverse faults. A comparison of the Alima anticline to other anticlines in the region suggests that several different styles of folding are present, each representing a different time of initiation.

Groundwater resources in deltaic aquifers are essential in the Mediterranean region to sustain the socioeconomic development of coastal communities and shallow-water ecosystems. Understanding the geological connection between coastal aquifers and the offshore sedimentary record is important to better predict consequences in terms of water management. In spite of this, most approaches to Postglacial and Pleistocene deltaic sedimentation focus either on the offshore or the delta plain; few studies correlate and integrate the entire system. In the Llobregat delta (south of Barcelona, Spain), onshore-offshore correlation is achieved by integrating data from sediment cores acquired on the deltaic plain with seismic profiles from offshore. Data integration enables the reconstruction of the entire deltaic system, providing a more well-defined picture and a better understanding of the onshore-offshore stratigraphic framework in a Late Quaternary, tectonically active narrow shelf in the western Mediterranean Basin.The late Quaternary record in the Llobregat delta shows an unusual well preserved transgressive-regressive cyclic stacking pattern, which displays peculiarities compared with most Mediterranean Quaternary deltaic shelves given that the transgressive and highstand intervals appear to be significantly preserved both onshore and offshore. The preservation of these deposits is attributed to the high subsidence rate on the continental margin controlled by Quaternary faults and the structure of the basement, and by sediment supply fluctuations. Depositional sequences also reveal contrasting patterns between the northeastern and southwestern Llobregat shelves, and show significant variability in the dip direction. The results are compared with diverse stratigraphic architectures reported elsewhere, and provide information to the ancient delta deposits about the distinct types of deltaic geometries generated under different sea-level trends, helping to improve sequence stratigraphic models, where deltaic geometries generated during specific intervals of the sea-level curve are poorly constrained and/or documented. (c) 2009 Elsevier B.V. All rights reserved.

Current building of civil Engineering infrastructures in the Barcelona plain and Llobregat delta (mainly metro and airport extension and high speed train) is providing new geological subsurface data to build better geologic models and understand the basin evolution. This work focuses on the pre-Quaternary units observed in cores. Based on petrographic analyses combined when it was possible with paleontological studies, we identified the lower Triassic Buntsandstein sandstone facies and Miocene continental and marine facies which appear compartmentalized due to extensive deformation. After this extensive episode, Pliocene and Quaternary sediments, which were deposited after the development of successive erosive surfaces, overlay the Triassic and Miocene units. The identification of these units enabled one to improve the interpretation of the tectonic and paleogeographic evolution of the Barcelona plain.

Groundwater flow in low matrix-permeability carbonate rocks is largely controlled by fracture networks. The stratigraphic features that control fracture initiation and termination within a sequence of sedimentary rock strata define the mechanical stratigraphy of the sequence. We investigate the effectiveness of various types of stratigraphic horizons in terminating opening-mode fractures in two different carbonate rock sequences: a relatively homogeneous dolomite sequence, in Door County, WI and an interbedded chalk and marl sequence within the Austin Chalk, TX. Additionally, we present analog and numerical modeling results that delineate the specific mechanisms that facilitate fracture termination. The combination of model results and empirical relationships between observed sedimentary features and mechanical stratigraphy shows: (1) fractures terminate at weak contacts (e.g. thin organic layers), shallowly buried contacts or thick fine-grained units adjacent to thin fractured beds, (2) fractures propagate across strong contacts (e.g. intracycle contacts between different lithology) and thin fine-grained units adjacent to thick fractured beds and (3) fractures step-over at moderate strength contacts. We use these guidelines to predict fracture network from sedimentary stratigraphy by qualitatively assessing the mechanical stratigraphy of a portion of the relatively complex Cretaceous shelf-margin sequence at Sant Corneli, Spain. This predictive demonstration illustrates the utility of assessing the mechanical stratigraphy of subsurface strata within which fractures are not directly observable. We conclude that for a variety of carbonate mechanical stratigraphic sequences, dominant fluid flow characteristics, such as horizontal high flow zones and flow compartmentalization, can be evaluated using fracture spacing and connectivity within fracture networks that is predicted from sedimentary stratigraphy. Although the resulting heterogeneous flow networks do not rely on every fracture present, they are highly dependent on the mechanical stratigraphy.

The Neogene succession recovered during ODP Leg 182 from the Great Australian Bight comprises unconformity-bounded, cool-water carbonates. A total of 15 hiatuses, each lasting ∼0.5 Myr or more, are identified or inferred primarily on the basis of planktonic foraminifer biostratigraphy from the basal Miocene to early Pleistocene. They are interpreted as local manifestations of major third-order boundaries at about 23.8 (H1), 22.3 (H2), 20.5 (H3), 18.7 (H4), 16.4 (H5), 14.8 (H6), 13.5 (H7), 11.5 (H8), 9.3 (H9), 7.0 (H10), 6.0 (H11), 4.5 (H12), 3.5 (H13), 2.5 (H14), and 1. 5 Ma (H15). The coincidence of these hiatuses with third-order global sequence boundaries suggests a eustatic control complicated by local tectonics. Three mega-hiatuses at about 15–16 Ma, 8–9 Ma and 1.5–2.5 Ma, each lasting >5 Myr at selected sites, are interpreted as being caused by large-scale slope failure during times of differential uplift/subsidence and sudden changes in relative sea level. These results provide evidence that the evolution of the southern Australian margin during the Neogene occurred in steps, controlled by a W–E stress field in the course of Australia’s northward drift and by changes in relative sea level that triggered sedimentation as well as sediment packaging by unconformities.

The La Luna Formation was deposited under anoxic/dysoxic conditions in a tropical epicontinental sea on the northwest South America margin. Sedimentological, micropaleontological and geochemical evidence provides insights into factors that influenced the sedimentation and controlled the accumulation of organic-rich deposits at decimeter and meter scales during the youngest of the Cretaceous oceanic anoxic events (OAE).The La Luna Formation consists of an alternation of black marlstones interbedded with black limestones and black marly limestones. The benthic foraminifera assemblages indicate sedimentation in the upper neritic to upper bathyal environment. These rocks contain large amounts of organic matter. It is interpreted that a combination of warm global and rainy climate and the presence of bathymetric barriers caused poor circulation and low rates of water column ventilation during a high sea level in the early Santonian leading to the preservation of carbon-rich deposits in this region. During the late Santonian, a cooling-trend in global climate increased wind strength and upwelling; this change probably reduced runoff causing a weakening of the pycnocline and destabilized the stratification in the water column providing a progressive increase in oxygen in the water column and on the sea floor and a decrease in total organic carbon preservation in a shallower basin. These changes and the establishment of full mid- and deep-water exchange in response to the deepening and widening of the Equatorial Atlantic Gateway could have been important mechanisms for ending the epeiric sea anoxia. Changes through time in the vanadium-nickel fraction, planktonic and benthic foraminifera assemblages, productivity proxy elements, and lithological characteristics support this model.Superimposed on the general trend, variations in calcium carbonate and total organic carbon percentages at the scale of tens of centimeters reveal high frequency cyclic variations, which apparently correspond to the main frequencies of orbital forcing. This cyclicity is interpreted as a primary depositional signal and is the result of orbital-controlled fluctuations in terrigenous dilution and variations in oxygen concentration at the base of the water column. Variations in the intensity of upwelling can be observed, but they did not control the cyclicity. (C) 2004 Elsevier B.V. All rights reserved.

Arsenic concentrations up to 12,000 μg/l have been measured in ground water from a sandstone aquifer in the Fox River valley in eastern Wisconsin, USA. In addition to a sulfide-bearing secondary cement horizon (SCH), which is present at the top of the aquifer, sulfide mineralization is also present throughout the aquifer. Within the SCH, arsenic occurs in pyrite and marcasite, and in iron hydroxides, but not as a separate arsenopyrite phase. Geologic, hydrogeologic, and geochemical data were used to characterize the arsenic source and the predominant geochemical process that controls its release to ground water. Several lines of evidence suggest that oxidation of sulfides is the cause of high (>100 μg/l) concentrations of arsenic in ground water, including 1) the presence of the arsenic-bearing sulfides in the aquifer; 2) water chemistry data that show a positive correlation between arsenic, iron, and sulfate and negative correlation between arsenic and pH; and 3) similar sulfur isotopic signatures in sulfides of the SCH and dissolved sulfate in ground water. We propose that atmospheric oxygen, introduced to the SCH through well boreholes, provides an oxidant to the system. This hypothesis is supported by the occurrence of high arsenic concentrations where water levels within the well intersect the SCH. However, the data do not unequivocally show sulfide oxidation to be the cause of the moderate (10−100 μg/l) and low (<10 μg/l) arsenic concentrations measured in ground water in the study area. The variability in thickness of the SCH and the concentration of arsenic within the sulfides, as well as the local availability of oxygen to the SCH, likely contribute to the spatial variability of ground water arsenic concentrations.

Vertical opening-mode fractures are mapped on quarry walls to assess the stratigraphic controls on fracture patterns in the relatively undeformed Silurian dolomite of northeastern Wisconsin. Our two-stage study uses maps of vertical fractures to assess the effectiveness of various types of stratigraphic horizons (e.g., organic partings or cycle-bounding mud horizons) in terminating opening-mode fractures. First, the mechanical stratigraphy of the exposures is interpreted from the observed fracture pattern. Both visual inspection and a newly developed quantitative method are employed to identify effective mechanical interfaces. The two methods show similar results, confirming the validity of qualitative visual inspection. The second stage of our study stochastically predicts mechanical stratigraphy and subsequent fracture pattern from empirical relationships between the observed sedimentary stratigraphy and the interpreted mechanical stratigraphy. For example, 63% of cycle-bounding mud horizons within the inner-middle and middle shelf facies associations serve as mechanical interfaces. These empirical percentages are input to a Monte Carlo analysis of 50 stochastic realizations of mechanical stratigraphy. Comparisons of the stochastically predicted and interpreted mechanical stratigraphy yield errors ranging from 13 to 33%. This method yields far better results than assuming that all stratigraphic horizons act as mechanical interfaces. The methodology presented in this article demonstrates an improved prediction of fracture pattern within relatively undeformed strata from both complete characterization of sedimentary stratigraphy and understanding mechanical controls on fracturing.

This data report presents sedimentological data obtained from Site 1130 in the Great Australian Bight (southern Australia) during Leg 182, a setting that is dominated today by strong ocean currents, downwelling, and water temperatures rarely above 20°C. The purpose is to characterize lithofacies and cyclicity. The different lithofacies reflect different texture, grain composition, grain size, and sorting as seen in thin section. Cyclicity is shown by repetition of coarsening-upward wackestone to packstone packages with an upward increase in neritic components. The cyclicity is corroborated by grain counts, point counts, and X-ray diffraction mineralogy. The cyclicity is interrupted by the deposition of nannofossil-rich wackestones. These data can be used to more effectively interpret processes affecting cool-water carbonate margins. INTRODUCTION Studies in the Great Australian Bight (GAB) are revealing intriguing insights into the understanding of the sedimentology, paleoceanography, and paleoecology of cold-water carbonate environments (James, 1997; Li et al., 1996; Boreen and James, 1993; James and von der Borch, 1991; James and Bone, 1994; Feary, Hine, Malone, et al., 2000). The GAB forms a prominent reentrant in the southern margin of the Austra1Simo, J.A., and Slatter, N.M., 2002. Data report: Sedimentology of a Pleistocene middle slope cool-water carbonate platform, Great Australian Bight, ODP Leg 182. In Hine, A.C., Feary, D.A., and Malone, M.J. (Eds.), Proc. ODP, Sci. Results, 182, 1–15 [Online]. Available from World Wide Web: . [Cited YYYYMM-DD] 2Department of Geology and Geophysics, University of Wisconsin, 1215 West Dayton Street, Madison WI 53706, USA. Correspondence author: simo@Geology.wisc.edu Initial receipt: 2 November 2001 Acceptance: 2 July 2002 Web publication: 6 September 2002 Ms 182SR-016 J.A. SIMO AND N.M. SLATTER DATA REPORT: SEDIMENTOLOGY OF A COOL-WATER CARBONATE PLATFORM 2 lian continent and is located between 123° and 134°E longitude and 32° and 37°S latitude (Feary and James, 1998). Modern sediments on the shelf are a mixture of relict calcareous grains and Holocene skeletal grains and are affected by seasonal downwelling, upwelling, and longperiod waves and swells (James et al., 2001). During Ocean Drilling Program (ODP) Leg 182 (Feary, Hine, Malone, et al., 2000), we drilled a thick (~550 m) Pleistocene slope succession in the GAB (Fig. F1). The drilling has extended previous shelf observations onto the slope and basin as well as provided a temporal framework to understand the margin evolution and processes. This study focuses on the thick middle–upper Pleistocene slope sequence recovered from Site 1130 drilled at a water depths of 488 m, an upper bathyal setting (Fig. F1). The site is located on the Eyre Terrace, a region dominated by coastal downwelling during most of the year and oligotrophic waters (James et al., 2001). Landward of Site 1130 are bryozoan mounds (Site 1132) and seaward are pelagic oozes (Sites 1126 and 1134) (Feary, Hine, Malone, et al., 2000). Thus, sediments at Site 1130 reflect the mixing of upper-slope and shelf-derived sediments and those derived from the water column and midslope. The goal of this report is to investigate the interaction between shelf and slope processes based on a high-resolution study of the sedimentological and faunal trends at Site 1130. PLEISTOCENE SEDIMENTS AND SITE 1130 Pleistocene sediments recovered during Leg 182 correspond to spiculitic skeletal packstone and fine-grained spiculitic foraminifer wackestone. The section is punctuated by thin intervals of nannofossil ooze. One of these intervals is the objective of this report. The color of the sediments ranges from a buff light gray to a pale olive-green. They represent continuous sedimentation at rates that sometimes exceeded 40 cm/k.y., which is equivalent to many shallow-water tropical carbonates (Eberli, Swart, Malone, et al., 1997; Feary, Hine, Malone, et al., 2000). Site 1130 intersected an almost complete Pleistocene succession with some exceptions (Feary, Hine, Malone, et al., 2000). Sedimentation rates were as high as 24–26 cm/k.y. in the middle and late Pleistocene, but much slower, 1.5–2 cm/k.y., in the early Pleistocene. Physical properties suggest strong cyclicity on a 100-k.y. frequency from 43 to 175 meters below seafloor (mbsf) and a higher 41-k.y. frequency between 175 and 254 mbsf (Feary, Hine, Malone, et al., 2000). An interval containing a cyclic succession of packstone and finegrained packstone-wackestone interrupted by a thin nannofossil ooze was selected for this study. The hypothesis is that the cyclicity resulted from changes in shelf processes and the deposition of nannofossil ooze is the outcome of a short-lived major reorganization of the slope and shelf processes. The studied interval (~123–151 mbsf) corresponds to the transition between Subunits IA and IB described on board (Feary, Hine, Malone, et al., 2000). These two subunits contain cyclic bioclastic packstones and wackestones and are separated by the white nannofossil ooze with bioclasts (~133.6 mbsf), which is the object of this report. The interval is part of the expanded middle–upper Pleistocene succession showing cyclicity in the color reflectance (700–400 range) and in the natural gamma ray (Feary, Hine, Malone, et al., 2000). The age of the studied interval is around the boundaries between the NN19 and NN21–NN20 nannofossil zones and the PT1b and PT1a planktonic fora4000 300

Cenomanian through Coniacian strata near the town of Sopeira in the south-central Pyrenees (northern Spain) are composed of a variety of autochthonous and allochthonous carbonate slope lithologies that are divided into six depositional sequences based on facies distribution patterns and stratal relationships. The sequences record three major phases of platform margin evolution: rifting, burial, and exhumation. During the first phase (sequences UK-1, UK-2, UK-3, UK-4, and lower UK-5), deposition occurred on the edge of a wrench basin, and a normal fault located beneath the platform margin strongly influenced slope evolution. Background hemipelagic sediments on the slope were commonly redeposited by submarine slumps and slides. More intense reworking resulted in matrix-supported, slope-derived megaconglomerates (debrites). During the Cenomanian and Turonian, seismically triggered debris flows originated at the platform margin, bypassed the upper slope, and were deposited on the lower slope as polymictic, clast-supported, matrix-rich megabreccias. The megabreccias form channelized and sheet-like bodies with erosional basal surfaces. Shallow carbonate environments backstepped during the Late Turonian and Coniacian, but displacement along the fault at this time resulted in the development of a steep submarine scarp and the exposure of Cenomanian and Lower Turonian strata to submarine erosion. Matrix-poor, margin-derived megabreccias form a thick talus pile at the base of the scarp. Some of the breccias were transported into the basin as debris falls, forming sheet-like beds. Marl eventually buried the Coniacian scarp in sequence UK-5, resulting in the second major phase of platform slope evolution. The slope profile at this time was relatively gentle, and redeposited material is less common. In the third phase (sequence UK-6), tectonically induced bankward erosion during the Santonian resulted in a high (greater than 800 in) erosional scarp with a regional east-west trend that was subsequently onlapped by siliciclastic turbidites. Rejuvenation of erosion in the same vicinity suggests that long-term tectonism controlled the position of the slope, rates of erosion, and sediment type on the slope. Sediment gravity flow processes are laterally and temporally related. Submarine slide and slump deposits commonly grade laterally downslope into slope-derived megaconglomerates. Debris flows that originated at the platform margin appear to have initiated slumps, slides, and other debris flows on the slope. Debris fall deposits are commonly capped by coarse, graded, lithoclastic packstones that may represent turbidites generated by the debris falls. Sediment fabric exerted a profound impact on depositional processes, distribution of facies, and morphology of the slope. Fine-grained, mud-rich, lower slope deposits were unstable at even moderate slope angles, and have been extensively redeposited. Redeposition of grain-rich, upper slope facies was triggered by syndepositional seismic activity and upslope migration of instability and erosion. In the presence of mud, the transport mechanisms are typically cohesive debris flows, which were able to carry material onto the lower slope and into the basin. When no mud was available, rock falls and debris falls were the dominant sediment gravity flows, and their deposits are restricted to a position on the hanging wall proximal to the fault. (C) 2002 Elsevier Science B.V. All rights reserved.

The Middle Ordovician St. Peter Sandstone and Glenwood Formation (Ancell Group) represent a significant target for gas exploration at the base of the Tippecanoe sequence in the Michigan basin. Core and well log data show that the St. Peter-Glenwood interval contains numerous carbonate units that provide the basis for both regional correlation and subdivision of the section into at least 20 high-frequency sequences. The temporal resolution afforded by these sequences allows a detailed analysis of sediment partitioning as the basin evolved. The spatial distribution of the basal sequences illustrates the pronounced east-to-west onlap of the Wisconsin arch. An abrupt increase in sequence thickness upsection indicates that a major episode of basin-centered subsidence began during middle St. Peter deposition and continued through the deposition of the Glenwood Formation. The upper sequences show a significant beveling of the Glenwood Formation and the top of the St. Peter Sandstone in the north, south, and southeast areas of the basin prior to deposition of the overlying Black River carbonates. Although eustatic sea level changes were undoubtedly operating at several scales, the facies distribution of this mixed clastic/carbonate system also documents significant changes of local and regional tectonics.

Calcite cements in the Silurian (Ludlovian) Pipe Creek Jr, Reef, north-central Indiana, are compositionally zoned with characteristic minor-element concentrations and stable isotope signatures, and were precipitated in different diagenetic environments. Superposition and crosscutting relationships allow us to group cement zones and to relate them to the sequence stratigraphic evolution of the reef.Pipe Creek Jr, Reef grew in normal marine waters, with the reef top high (greater than 50 m) above the platform floor. Flank facies are volumetrically important and are preserved largely as limestone, in contrast to most dolomitized Silurian reefs in the midcontinent, Syndepositional marine cements fill primary porosity and synsedimentary fractures and are interlayered with marine internal sediment. Now low magnesium calcite, their isotopic compositions are similar to those of depositional grains and cements estimated to have precipitated from Ludlovian sea waters. Depositional porosity was reduced by 75% by the precipitation of these syndepositional cements, which stabilized the steeply dipping flank slope.Postdepositional, clear calcite cements are interpreted as shallow-phreatic and burial cements on the basis of their relationship to periods of karstification and fracturing, Shallow-phreatic cements, with concentric cathodoluminescent (CL) zonation, precipitated in primary pores and are postdated by fractures and caves filled with Middle Devonian sandstone. CL zonal boundaries are sharp, and some, near a major stratigraphic unconformity, show evidence of dissolution. The volumetric abundance of the individual CL zones varies in the reef, indicating a complex superposition of waters of varying chemistry and rock-water interaction that are probably related to relative sea level changes. This important aspect of the reef stratigraphy is recorded only by the diagenetic succession, because evidence of earlier sea-level changes is removed by a major later regional unconformity.Burial cements are the youngest diagenetic feature recognized, and they rest conformably or unconformably over older cements. They exhibit both concentric CL zonation acid sectoral zoning, they are ferroan to nonferroan, and they contain thin sulfide zones along growth-band boundaries, Their isotopic compositions do not overlap with shallow-phreatic or marine cement values. Degraded oil postdates burial cements, and is composed of the same sterane class as the Devonian-age Antrim Shale, the probable source rock, This source contrasts with that of reef reservoirs in the Michigan Basin, where Silurian strata are commonly the hydrocarbon source.

Cenomanian–Turonian strata of the south‐central Pyrenees in northern Spain contain three prograding carbonate sequences that record interactions among tectonics, sea level, environment and sediment fabric in controlling sequence development. Sequence UK‐1 (Lower to Upper Cenomanian) contains distinct lagoonal, back‐margin, margin, slope and basin facies, and was deposited on a broad, flat shelf adjacent to a deep basin. The lack of reef‐constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. Sequence UK‐2 (Upper Cenomanian) contains similar shallow‐water facies belts, but syndepositional tectonic modification of the margin resulted in a steep slope and deposition of carbonate megabreccias. Sequence UK‐3 (Lower to Middle Turonian) records a shift from benthic to pelagic deposition, as the shallow platform was drowned in response to a eustatic sea‐level rise, coupled with increased organic productivity. Sequences UK‐1 to UK‐3 are subdivided into lowstand, transgressive and highstand systems tracts based on stratal geometries and facies distribution patterns. The same lithologies (e.g. megabreccias) commonly occur in more than one systems tract, indicating that: (1) the depositional system responded to more than just sea‐level fluctuations; and (2) similar processes occurred during different times throughout sequence development. These sequences illustrate the complexity of carbonate platform dynamics that influence sequence architecture. Rift tectonics and flexural subsidence played a major role in controlling the location of the platform margin, maintaining a steep slope gradient through syndepositional faulting, enhancing slope instability and erosion, and influencing depositional processes, stratal relationships and lithofacies distribution on the slope. Sea‐level variations (eustatic and relative) strongly influenced the timing of sequence and parasequence boundary formation, controlled changes in accommodation and promoted platform drowning (in conjunction with other factors). Physico‐chemical and climatic conditions were responsible for reducing carbonate production rates and inducing platform drowning. Finally, a mud‐rich sediment fabric affected platform morphology, growth geometries (aggradation vs. progradation) and facies distribution patterns.