Highlights—Spatial Patterns of Fluvial Sandbodies

Distinguishing allogenic and autogenic processes on the distribution and patterns of channel belts of fluvial systems is challenging because both can control avulsions across a range of time scales and because of incomplete preservation. In this paper, Flood and Hampson present a quantitative analysis of the distribution of channelized fluvial sandbodies within the widely studied Blackhawk Formation of the Wasatch Plateau, central Utah. The results indicate that: 1) spatial patterns of sandbody distribution can be attributed to avulsion of deltaic distributary channels in locations downstream of long-lived avulsion nodes in the lower part of the Blackhawk Formation, or by compensational stacking of sandbodies in the upper part of the Blackhawk Formation, and 2) tectonic subsidence rate varied markedly during deposition (c. 80-700 m/Myr), but any potential variation in its relationship to avulsion frequency had little influence on avulsion style. This study demonstrates the importance of collecting large outcrop datasets, which enable quantitative characterization of sandbody distributions and related stratigraphic architectures using spatial statistical methods.

Quantitative analysis of the dimensions and distribution of channelized fluvial sandbodies within a large outcrop dataset: Upper Cretaceous Blackhawk Formation, Wasatch Plateau, central Utah, U.S.A. by Yvette S. Flood and Gary J. Hampson

A Look Back…50 Years: South Florida Sediment

A lasting paradigm in carbonate sedimentology is that “carbonates are born, not made,” a truism that distinguishes them from the siliciclastic relatives. Fifty years ago, a classic contribution by Swinchatt emphasized the impact of their distinct origins and characteristics of early alteration on composition and texture of sediment of the South Florida reef tract. The results illustrated the complex influences of seagrass, physical process, biological breakdown, and how they vary across this shelf margin. Swinchatt suggested that “interrelationships between various rates of production and breakdown may be extremely complex and their effect on the sediment difficult to evaluate…and that further investigation is needed.”

Significance of constituent composition, texture, and skeletal breakdown in some Recent carbonate sediments by Jonathan P. Swinchatt

Highlights—Crevasse Subdeltas: Small but Important

The geomorphology, stratal architecture, and sedimentologic attributes of a range of deltas have been interpreted in the context of fluvial, tidal, and wave processes and sea-level change. Most studies focus on delta-front regions, whereas finer (and typically less well exposed) delta plain deposits have received less attention. Here, Gugliotta et al. focus on defining and describing tide-influenced crevasse subdelta deposits, an important component of lower delta plain stratigraphy of a river-dominated delta in the Lajas Formation of the Neuquén Basin of Argentina. The study emphasizes the importance of understanding the relative importance of tide and river processes in facies distribution and architecture, and the applications to characterization of interdistributary deposits. The data suggest that some “tidal” deposits interpreted from the rock record may instead be river-dominated, tide-influenced crevasse subdeltas, and that this distinction has important implications for understanding paleogeography and predicting reservoir geometries.

Stratigraphic record of river-dominated crevasse subdeltas with tidal influence (Lajas Formation, Argentina) by Marcello Gugliotta, Stephen S. Flint, David M. Hodgson, and Gonzalo D. Veiga

Highlights—Minibasin Dynamics

Although typically < 10 km wide, intraslope minibasins such as those in the Gulf of Mexico can include rapid subsidence, accumulate thick sediment pile, and ultimately host large hydrocarbon accumulations. Differential sediment loading on a mobile substrate (e.g., salt) can drive accommodation and stratigraphic architectures in intraslope minibasins, but sedimentologic and tectonic processes commonly are evaluated separately. This contribution by Kopriva and Kim experimentally integrates depositional and tectonic processes to investigate the relations of substrate movement and minibasin sedimentation. A silicone polymer model of a viscous mobile substrate provided the basis for a series of 2D experiments to explore the effects of variation in 1) sediment supply rate, 2) depositional style (intermittent sediment supply), and 3) the thickness of the deformable substrate on subsidence patterns and minibasin stratigraphic development. The results highlight the possible role of autogenic processes on minibasin dynamics and fill-and-spill stratigraphy.

Coevolution of mini basin subsidence and sedimentation: experiments by Bryant T. Kopriva and Wonsuck Kim

Highlights—Mudstone Description Tools

Much of the sedimentary record comprises mudstone, and recent interest is driven by recognition of hydrocarbon sources, reservoirs, and seals in deposits of mudstone. Beyond this importance, they also influence groundwater dynamics and provide important perspectives on the global carbon cycle and climate and oceanography through geologic time. Yet, traditional mudstone descriptors neither capture the variability in their physical, biogenic, and chemical attributes, nor facilitate appropriate characterization and interpretation of controlling processes on their formation. Here, Lazar et al. discuss the utility of existing mudstone nomenclature, provide context for the information required to fully characterize mudstone, and recommend guidelines that facilitate consistent, repeatable, and efficient capture of key attributes to evaluate and compare fine-grained rocks. The application of their simple, integrated descriptive scheme to the Cretaceous Eagle Ford Shale demonstrates the utility of the technique for assessing and predicting rock properties.

Capturing keyattributes of fine-grained sedimentary rocks in outcrops, cores, and thinsections: nomenclature and description guidelines by O. Remus Lazar, Kevin M. Bohacs, Joe H.S. Macquaker, Juergen Schieber, and Timothy M. Demko