Crinkle cracks are sand-filled cracks up to 5 mm wide in plan view that pinch at their ends. In cross section, they are canted and crinkled. They cut mudstone beds that underlie hummocky cross-laminated sandstone lenses. They are here described from the Piegan Group, Proterozoic Belt Supergroup, but they are widespread in Proterozoic and Phanerozoic marine and lacustrine rocks. However, they represent a distinctive, descriptive style of mudcracks, not attributed to inferred syneresis processes, although they have been commonly attributed to syneresis. In plan view, crinkle cracks closely resemble cracks formed where oscillatory waves striking viscous mud banks are transformed into fluid solitary-like waves that open surface cracks on their trailing limbs and close the cracks on their leading limbs as they pass through the viscous mud. Crinkle cracks preserved in rocks are hypothetically attributed to oscillatory waves moving sand over viscous mud. The oscillatory waves are transformed into solitary-like waves as they pass down into the mud, forming the cracks. The surface sand falls down into the cracks, preserving them. With burial, the water escapes, and the viscous mud compacts, crinkling the sand-filled cracks.

Abstract A phenomenon unique to fine-grained sediment is its ability to alter the physical characteristics of the overlying water column. Although the present state of research recognizes many aspects of fine-grained seabed and water column interactions, this study documents how an energetic sandy, shallow marine system can autogenically transition to a system capable of accumulating fine-grained bedforms to clinoforms. To understand these transitional processes this study examines the lithostratigraphy and depositional history of the Suriname portion of the Guiana Coast (French Guiana, Suriname, and Guyana). Four major lithologic facies (Pre-Holocene silty clay; peat-rich silty clay; sandy mud; silty clay with cheniers) were derived from the Late Holocene sea level rise and influx of sediments emitted from the Amazon River. Since approximately 6000 BP, ~10 to 20% of Amazon-derived sediments bypass the Amazon shelf and are transported northwestward toward the study area. Along the Suriname coast (~900 km from the Amazon), however, significant mud accumulation did not commence until 3000 to 3500 BP. Suspended sediments can travel this distance in less than 1 month. A migrating (1.5 km/yr) mud bank could travel the 900 km from the Amazon mouth in 600 years or, after formation of a 400-km-wide subaqueous Amazon delta (by 1200 BP), migrate the remaining 500 km by 4500 BP, still 1000 to 1500 years prior to the time period during which radiocarbon dates indicate significant mud accumulation began. Consequently, either there was a major hiatus in sediment transport and accumulation between 6000 BP to 3000 BP or some other transport process other than suspension or mud-bank migration-controlled initial mud accumulation. Assuming steady-state conditions, lateral accretion rates from 6000 BP to 3000 BP equate to 0.3 to 0.4 km/yr. These rates, which are similar to migration rates cited by previous studies for the trailing edges of mud banks in French Guiana, may reflect postmigration erosion of the initial mud banks. Whether there is an erosional overprint or some other process, this lateral accretion rate is an indicator of the amount of fluid mud necessary for ‘mud to beget mud.’ More general prerequisites necessary for a shallow marine setting to autogenically form fine-grained clinoform-scale accumulations are, first, a single large source of muddy sediments (a major river) and, secondly, unidirectional transport processes to concentrate and continuously supply mud sediments to the system.

Laguna Mar Chiquita (central Argentina; ~latitude 31°S, longitude 63°W) provides an outstanding opportunity to examine organic facies development and petroleum source-rock potential in a modern thick-skinned foreland basin lake. In this case study, we define profundal, paleodelta, and lake-margin depositional environments based on trends in bathymetry and lake-floor sediment particle size. Sedimentary geochemical analyses indicate that organic carbon–rich muds accumulate in profundal environments during the extant lake-level highstand. The lateral variability of organic facies is minimal. The quality of organic facies is controlled by lake level and depositional environment, both of which dictate patterns of algal productivity, siliciclastic dilution, and early diagenesis. We present conceptual models of lacustrine source rocks in both thick-skinned and thin-skinned foreland basins based on modern analog data from both Laguna Mar Chiquita and other lakes in the central Andean foreland. Over relatively short time intervals (10 2 –10 4 yr), climatically driven water-level fluctuations influence the source-rock potential of these basins. Over time intervals >10 5 yr, contraction and lateral migration of the basin flexural profile control stratal stacking patterns and the potential for hydrocarbon play development.

Abstract Recent discoveries in offshore Tanzania and Mozambique highlight East Africa as an emerging world-class petroleum province. Estimates for this province total 12.5 BBO and 250 TCF of gas ( Brownfield et al. , 2012 ) as yet undiscovered hydrocarbons. Play-opening reservoir systems have been verified in Paleocene, Eocene, and at least two Oligocene deep water submarine fan and intra-slope channel complexes ( Law, 2011 ). Evidence continues to mount suggesting that the Late Cretaceous section may also contain deposits from similar depositional settings ( TPDC, 2003 ). There are indications that the petroleum system may contain oil as well as the established gas, and investigations are underway to determine if liquids are also present in the deep water areas. In short, the petroleum system components are all verified, what remains is the need to rapidly high grade what constitutes an enormous play area (> 0.5 million square kilometers) by establishing the extent and distribution of the deep-water reservoir systems. Therefore a strong impetus exists to develop techniques for high grading the area which can be performed on 2D regional (seismic-) data. One such technique is presented in this paper. It involves generating high-resolution horizon interpretations from the 2D seismic data. It enables not only the transforming of 2D seismic data into Wheeler (chronostratigraphic) domain ( Ligtenberg et al. , 2006 ; de Groot et al. , 2010 ; Qayyum et al. , 2012 ) but also helps in mapping depositional shifts and reservoir distribution.

Abstract Across the west Nile Delta, channel complex, channelized lobe, and channel-levee turbidite reservoir systems were deposited throughout the Pliocene following the Messinian salinity crisis and the reestablishment of a muddy depositional slope on the Nile Delta cone. Commercial gas discoveries driven by seismic amplitude anomalies in all of these different turbidite reservoir architectures (Ruby, Fayoum, and Giza fields) are dispersed around the modern day Rosetta Canyon, in water depths ranging from 300m to 900m. Structurally, the west Nile Delta (WND) is characterized by steep, fault-bounded margins which exerted a fundamental control on the stratigraphic position and fill of slope canyon and channel systems in the Pliocene play fairway. Syndepositional slope collapse has had a significant impact on the development of these slope reservoir systems. The Giza Field gas accumulation is an upper-slope channel complex set characterized by a 160m erosional confinement within a 2.5km wide fairway draping a 20 X 10 km wide plunging anticline, setting up a combination structural-stratigraphic trap. Down slope, the Giza channel complex set can be tracked for a distance of >100 km into a constructional levee confined system on the lower slope. Visualization of the internal geometry of the Giza channel complex set is based on 3D multiazimuth (MAZ) seismic data tied to extensive conventional core data recovered from both the exploration discovery well and a subsequent appraisal well. The high resolution seismic, combined with log- and corescale observations, provide spectacular insights into the gross seismic architecture, internal geometry, and stacking patterns of the Giza channel complex set. This paper will demonstrate the facies change and channel geometry variation with the Giza channel reservoir fairway, from incision and bypass, to the initial backfill within a low sinuosity aggradational stacked channel phase, to a more sinuous constructional channel levee fill style having ‘levee lobes,’ to ultimate channel abandonment. Fundamental controls on sedimentation patterns are controlled by a combination of a basin-bounding tectonic control on sediment input points, mass transport processes on the slope generated (generation of accommodation space for precursor lobes), and a deep seated intrabasinal tectonic control that has episodically generated subtle, emergent topography, which has, in part, controlled channel element sinuosity and net to gross.

Abstract The Danube River Basin and the Black Sea represent a unique natural laboratory for studying source to sink and global change. We will address information on the “active sink” of the system, which represents the area of active deposition: sea level variation, sediment balance, and neotectonics. Also, we will discuss the evolution and quantification of climate, tectonics, and eustasy on the sedimentation in the western Black Sea basin, along both southern and northern margins, obtained from understanding the Danube deep-sea fan processes and sedimentation. In the last decade, many of the geosciences studies carried out in the Black Sea have focused on the Holocene marine transgression. This topic has been fully discussed and is still a matter of debate. Since the DSDP drillings, the lithology and mineralogy of deep sediments from the Black Sea have been well studied. However, only few recent studies have focused on the deep-sea morphology and turbidite sedimentation in the western Black Sea basin, in which the main depositional feature is the Danube submarine fan. Oceanographic surveys in the Black Sea in 1998, 2002, and 2004 carried out in the framework of French-Romanian joint project and the European ASSEM-BLAGE (EVK3-CT-2002-00090) project have collected a large amount of data (Multibeam echo sounder data, CHIRP seismic, as well as Kullenberg and Calypso cores). This paper presents insights from recent coring and seismic data recovered at the boundary of influence of both the distal part of the Danube turbiditic system and the Turkish margin. This data set provides a good record of changes in the sedimentary supply and climatic changes in the surrounding Black Sea since the last 25 ka. Based on this study, we demonstrate that the deep basin deposits bear the record of the late Quaternary paleoenvironmental changes. Finally, the western Black Sea basin constitutes an asymmetric subsident basin bordered by a northern passive margin containing confined mid-size, mud-rich turbiditic systems, and a tectonically active southern turbiditic ramp margin.

Abstract Organo-clay fabric and physico-chemistry of marine mud play important roles in early sediment diagenesis including the development of mass physical properties, consolidation behavior, and sequestration of organic matter (OM) in sediments over geologic time. Transmission electron microscopy (TEM) images of nano- and microfabric reveal that organic matter is sequestered following enzymatic digestion despite the pervasive openness of pore-fluid pathways observed in 3D rotated images. The locations of sequestered organic matter correspond to those predicted by modeling of the potential energy of interaction. Initial flume experiments on high porosity clay-mineral-rich mud deposited under dynamic flow and static (vertical settlement) conditions demonstrate differences in clay fabric and the distribution of organic matter (we define the term organo-clay fabric as the contiguous association and arrangement of organic matter and clay domains). These differences in organo-clay fabric impact the preservation-degradation mechanisms and dynamics during depositional and burial processes. Organo-clay fabric and physico-chemical modeling of potential energy fields coupled with direct observations of organo-clay fabric, three-dimensional (3-D) clay fabric reconstructions, sediment static and dynamic properties, and controlled flume experiments are providing new insight into the developmental history of sedimentary sequences, nano- to macroscale environmental processes, and diagenesis from unconsolidated mud to shale.

Abstract The Ceduna subbasin forms part of the under-explored but highly prospective frontier Bight Basin located on the southern margin of South Australia. Structural mapping of the Ceduna subbasin reveals two separate delta lobes/systems deposited in the late Albian-Santonian and late Santonian-Maastrichtian. Each system is comprised of an updip delta top linked via a shale detachment to a down-dip delta toe or deep-water fold-thrust belt. These delta lobes are separated by a transgressive sequence of Turonian-Santonian age that deposited a thick marine mud, up to 2000 m in places. Like the Niger Delta, this marine mud forms the detachment for the overlying Santonian-Maastrichtian delta—deep-water fold-thrust belt system and is also a proposed source rock. An Albian marine mud forms the detachment for the older Cenomanian system and is also thought to exhibit source rock potential. We examine the differences in structural style between the western and eastern parts of the basin, the west being dominated by the Cenomanian lobe and the east by the Santonian-Maastrichtian lobe. Recent work on the sedimentary provenance of the basin suggests two different mechanisms were responsible for deposition of the delta lobes in the west and east, as well as significant changes in regional tectonics dominating the basin fill history. This has resulted in the deposition of two delta—deep-water fold-thrust belt systems rather than a continuous system as is commonly observed elsewhere in Cenozoic analogues such as the Niger Delta. Evidence from the drilling of Gnarlyknots-1A on the delta-top suggests excellent reservoir quality in the Santonian-Maastrichtian system; the potential for seal and source development increases farther offshore toward the deep-water fold-thrust belts. The abundant availability of deep-water contractional targets, combined with modeled increase in source and sealing potential farther offshore, results in a highly prospective system in both the Cenomanian and Santonian-Maastrichtian deep-water fold-thrust belts.

Bear Lake sediments were predominantly aragonite for most of the Holocene, reflecting a hydrologically closed lake fed by groundwater and small streams. During the late Pleistocene, the Bear River flowed into Bear Lake and the lake waters spilled back into the Bear River drainage. At that time, sediment deposition was dominated by siliciclastic sediment and calcite. Lake-level fluctuation during the Holocene and late Pleistocene produced three types of aragonite deposits in the central lake area that are differentiated primarily by grain size, sorting, and diatom assemblage. Lake- margin deposits during this period consisted of sandy deposits including well-developed shoreface deposits on margins adjacent to relatively steep gradient lake floors and thin, graded shell gravel on margins adjacent to very low gradient lakefloor areas. Throughout the period of aragonite deposition, episodic drops in lake level resulted in erosion of shallow-water deposits, which were redeposited into the deeper lake. These sediment-focusing episodes are recognized by mixing of different mineralogies and crystal habits and mixing of a range of diatom fauna into poorly sorted mud layers. Lake-level drops are also indicated by erosional gaps in the shallow-water records and the occurrence of shoreline deposits in areas now covered by as much as 30 m of water. Calcite precipitation occurred for a short interval of time during the Holocene in response to an influx of Bear River water ca. 8 ka. The Pleistocene sedimentary record of Bear Lake until ca. 18 ka is dominated by siliciclastic glacial flour derived from glaciers in the Uinta Mountains. The Bear Lake deep-water siliciclastic deposits are thoroughly bioturbated, whereas shallow-water deposits transitional to deltas in the northern part of the basin are upward-coarsening sequences of laminated mud, silt, and sand. A major drop in lake level occurred ca. 18 ka, resulting in subaerial exposure of the lake floor in areas now covered by over 40 m of water. The subaerial surfaces are indicated by root casts and gypsum-rich soil features. Bear Lake remained at this low state with a minor transgression until ca. 15 ka. A new influx of Bear River water produced a major lake transgression and deposited a thin calcite deposit. Bear Lake quickly dropped to a shallow-water state, accumulating a mixture of calcite and siliciclastic sediment that contains at least two intervals of root-disrupted horizons indicating lake-level drops to more than 40 m below the modern highstand. About 11,500 yr B.P., the lake level rose again through an influx of Bear River water producing another thin calcite layer. The Bear River ceased to flow into the basin and the lake salinity increased, resulting in the aragonite deposition that persisted until modern human activity. The climatic record of Bear Lake sediment is difficult to ascertain by using standard chemical and biological techniques because of variations in the inflow hydrology and the significant amount of erosion and redeposition of chemical and biological sediment components.