Highlights—Tufas and Paleoclimate

As rapidly precipitating freshwater carbonate accumulations that form in equilibrium with ambient water, tufas represent potential sources of high-resolution paleoenvironmental records.  To critically examine the use of tufa isotopic records in such reconstructions,  Osácar et al. examine a 12-year record of a modern tufa system, comparing water δ18O with δ13C and δ18O signatures in the precipitates.  The data illustrate that these tufas mimic seasonal temperature changes, but that the pattern is complicated by changes in the isotope record of precipitation.  These results are interpreted to illuminate the complex interaction of factors operative at several different type scales (seasonal and annual) that must be evaluated to accurately understand the isotopic record of ancient tufa systems.

Environmental Factors Controlling the δ13C and δ18O Variations of Recent Fluvial Tufas: A 12-Year Record from the Monasterio de Piedra Natural Park (NE Iberian Peninsula) by M. Cinta Osácar, Concha Arenas, Marta Vázquez-Urbez, Carlos Sancho, Luis F. Auqué, and Gonzalo Pardo

Highlights—Hydrographs and Hyperpycnites

Hyperpycnites are deposits of a distinct style of flow that represents a mix of sediment and water that is denser than the water into which the mix flows; these types of deposits commonly are interpreted in the context of fluvial discharge into standing bodies of water.  Here, Saitoh and Masuda test conceptual and experimental models of hyperpycnal flow deposits by exploring spatial variability in subaqueous flood deposits in cores from a lake in Japan with limited wave or tide reworking.  The results clearly indicate that a single flood event can produce multiple eposides of waxing and waning flow, and the nature and controls on spatial variability in the sedimentology of the resultant deposits.  The results suggest the absence of a direct correlation between paleo-flood frequency or intensity and the sedimentary record.

Spatial Change of Grading Pattern of Subaqueous Flood Deposits in Lake Shinji, Japan by Yu Saitoh and Fujio Masuda

Highlights—SEPM Medalists

Each year, SEPM honors a group of medalists for their outstanding contributions to sedimentary geology.  This week, we start a series to honor some of the recipients by providing “Highlights” of their contributions to JSR. 

The 2013 awardees include:

Twenhofel Medalist: Paul Enos. The highest award of SEPM Society for Sedimentary Geology. This award is in recognition of "Outstanding Contributions to Sedimentary Geology."

Shepard Medalist: J. Casey Moore. The Francis P. Shepard Medal for Marine Geology is awarded in recognition of "Excellence in Marine Geology."

Pettijohn Medalist: J.A.D. (Tony) Dickson. The Francis J. Pettijohn Medal for Sedimentology is awarded in recognition of "Excellence in Sedimentology."

Moore Medalist: Kenton Stewart Wall Campbell. The Raymond C. Moore Paleontology Medal is awarded in recognition of "Excellence in Paleontology."

James Lee Wilson Award: Kyle M. Straub. The James Lee Wilson Award is bestowed in recognition of "Excellence in Sedimentary Geology by a Young Scientist."

Honorary Member: Dale Leckie.  Honorary Membership in the SEPM Society for Sedimentary Geology acknowledges excellence in professional achievements and extraordinary service to the Society.

Medals and awards will be presented to the awardees at the 2013 President's Reception and Awards Ceremony, during the SEPM Annual Meeting held in Pittsburgh, PA on Tuesday, May 21, 2013 in the Omni William Penn hotel.

To all recipients, congratulations on your honor!

Highlights—Paleosols and Paleoclimate

To evaluate climatic conditions through the geologic past, the stable isotopes of carbon and oxygen in paleosols have been evaluated to assess ancient atmospheric CO₂ concentrations and paleo-atmospheric circulation patterns.  Yet, these records may be compromised if they do not precipitate in equilibrium with soil CO₂ and soil water.  Michel et al. assess this possibility by examining the isotopic record of modern Vertisols (a soil class) that include a range of material incorporated from underlying marine limestone, a potential contaminant.  The results indicate the roles that soil development, weathering, and topographic position can play in compromising the soil signal.  They suggest that inheritance (contamination) from precursor substrates can alter a “climate” signal in some cases, and should be assessed in application of geological soils for paleoclimate studies.

Stable-Isotope Geochemistry of Vertisols Formed On Marine Limestone and Implications for Deep-Time Paleoenvironmental Reconstructions by Lauren A. Michel, Steven G. Driese, Lee C. Nordt, Daniel O. Breecker, Dana M. Labotka, and Stephen I. Dworkin

Highlights—Brrrr…The Cold Facts about Cryogenic Cave Pearls

Cave pearls are a distinct form of loose, spherical mineral deposit precipitated in caves (speleothems).  This paper by Žák et al. describes a genetically distinct type of cave pearls found in seasonally frozen ice caves of Carpathian Mountains, termed “cryogenic cave pearls.”  Integrating petrographic, SEM, U-series and radiocarbon dating, and stable carbon and oxygen isotope analyses, they illustrate the essential role of seasonal freezing and frost action in the formation of cryogenic cave pearls.  The results provide unique insights into the genesis of these features, and into conditions necessary for cave pearls in general.

Cryogenic Cave Pearls In the Periglacial Zones of Ice Caves by Karel Žák, Monika Orvošová, Michal Filippi, Lukáš Vlček, Bogdan P. Onac, Aurel Perşoiu, Jan Rohovec, and Ivo Světlík

Highlights—Microbes Pumping Iron(stone)

Oolitic ironstones occur quite frequently in condensed sections in the stratigraphic record and can serve as important iron resources. In this paper, Barale et al. use a Cretaceous condensed section to explore the conditions in which mixed Fe-oxide / Ca-phosphate ooids form, why they usually show an ellipsoidal shape in spite of a sub-equidimensional nucleus, and why Fe-oxide cortical layers intimately alternate with Ca-phosphate layers. Their results, which integrate cathodoluminescence, EDS microprobe, backscattered electron imaging, epifluorescence, XRD, and micro Raman spectroscopy, reveal a complex history of prolonged alterations of oxic and post-oxic conditions, interpreted to be related to alternating accumulation and winnowing, and related stop-and-start microbial activity. Collectively, the results provide new insights into the sedimentological and paleoenvironmental conditions in which oolitic ironstones form, detailing the sedimentation, shallow burial, reworking and sea-floor exposure of sediment that ultimately is composed almost exclusively of authigenic grains. 

The Role of Microbial Activity In the Generation of Lower Cretaceous Mixed Fe-Oxide–Phosphate Ooids from the Provençal Domain, French Maritime Alps by Luca Barale, Anna D'atri, and Luca Martire

Highlights—Small Carbonate Platform Evolution—No Bull!

Small reefal platforms that form in response to both tectonic and sea level changes are features ubiquitous through the Phanerozoic.  Commonly, however, these small platforms are buried and limited data are available on spatial and temporal lithofacies heterogeneity.  This paper by McNeill et al. documents the formation and timing of a ~90 km² Pliocene-Pleistocene platform as it evolved in a tropical, convergent tectonic setting (backarc) from a siliciclastic foundation to a mixed system dominated by reefal carbonates.  The results reveal three depositional sequences defined using field relations and refined depositional ages using strontium-isotope stratigraphy, magnetostratigraphy, and coral stratigraphy. The spatial sedimentological patterns of the three sequences provide a near-modern analog that illustrates lithofacies variability that may be present in buried reefal platforms.

Depositional Sequences and Stratigraphy of the Colón Carbonate Platform: Bocas Del Toro Archipelago, Panama by Donald F. McNeill, James S. Klaus, Laura G. O'Connell, Anthony G. Coates, and William A. Morgan

Highlights—Marine Mudstone: Neither Homogeneous nor Isotropic

Mudstone-dominated marine successions are common in the geological record, but a full understanding of their depositional processes commonly is hampered by a lack of generally accepted diagnostic criteria to distinguish between hemipelagic settling and deposition from a flowing medium.  In this paper, Dall’olio et al. integrate sedimentologic observations with analyses of the anisotropy of magnetic susceptibility (AMS) in the Miocene Marnoso Arenacea Formation of Italy to explore the utility of this technique for evaluating depositional processes.  The results reveal that maximum susceptibility axes clustered within the depositional plane along the average palaeoflow direction inferred from flute casts at the base of the nearest turbidite beds. This fabric is interpreted as largely sedimentary in origin, due to the alignment within the bedding plane of paramagnetic/ferromagnetic grains; this result contrasts with the hemipelagic settling interpretation that is commonly invoked for this unit.  Collectively, the results illustrate the value of AMS analysis in study of depositional processes.

Magnetic-Fabric Analysis as a Tool to Constrain Mechanisms of Deep-Water Mudstone Deposition In the Marnoso Arenacea Formation (Miocene, Italy) by Eleonora Dall'olio, Fabrizio Felletti, and Giovanni Muttoni

Highlights—Random Rivers Stack in Stratigraphy

The two end-member models of the facies architecture of alluvial-coastal plain systems suggest that patterns are either predictable within unconformity-bounded sequences or that they are substantively overprinted by autogenic processes.   In this paper, Hampson et al. critically appraise these end-member models of fluvial stratigraphy using detailed architectural analysis of sandbodies developed at different positions within a regressive alluvial-to-coastal plain wedge in the Upper Cretaceous Blackhawk Formation of Utah. The results illustrate variations in the size and internal organization of fluvial sandbodies, and the relationship between these parameters and stratigraphic context; trends are broadly interpreted to reflect decreasing tectonic subsidence through time, with random distribution of sandbodies that represent large-scale avulsion (e.g., autogenic) processes.  These results can be applied to enhanced characterization of hydrocarbon reservoirs deposited in fluvial environments.

Modest Change In Fluvial Style With Varying Accommodation In Regressive Alluvial-To-Coastal-Plain Wedge: Upper Cretaceous Blackhawk Formation, Wasatch Plateau, Central Utah, U.S.A. by Gary J. Hampson, Thomas O. Jewell, Nawazish Irfan, M. Royhan Gani, and Bryan Bracken

Highlights—Dynamic Inlets

Barrier-island landforms are common on many wave-dominated shoreline systems around the world, and ancient analogs form important petroleum reservoirs.  In this study, Seminack and Buynevich use ground-penetrating radar (GPR), sediment cores and dating to understand the facies architecture and evolution of shoreline and inlet systems of Assateague Island, MD, and to test the notion that it is related to the historical Green Run Inlet, located approximately 3 km to the south.  The authors suggest that a ‘traditional’ survey of relict inlets would have overlooked the study site due, to its lack of surficial evidence of inlet existence, and that the results illustrate the value of a multi-technique approach to study of inlet dynamics.  These results illustrate how reconstructing the facies architecture and evolutionary pathways of inlet-barrier island systems provide enhanced understanding of their geological evolution and stratigraphic framework, as well as their possible influence on coastal hazards.

Sedimentological and Geophysical Signatures of A Relict Tidal Inlet Complex Along A Wave-Dominated Barrier: Assateague Island, Maryland, U.S.A. by Christopher T. Seminack and Ilya V. Buynevich

A Look Back…5 years—Paleozoic Subtropical Carbonates

Carbonate sediments can be subdivided into two end-member realms, heterozoan and photozoan, that in many cases relate to “cool water” and “warm water” conditions respectively.  Between these end members are “subtropical” carbonates that can include a mix of both realms.  In this paper, Bensing et al. describe Lower Permian strata from Arctic Canada that include a temporally changing, sedimentologically mixed assemblage.  The sediments suggest a gradual cooling and decrease in seawater temperature, but that changes in sea level and oceanographic conditions complicated trends.  The results represented a refinement of criteria for recognizing and interpreting heterozoan carbonates in Paleozoic strata.

Carbonate Deposition During a Time of Mid-Latitude Ocean Cooling: Early Permian Subtropical Sedimentation in the Sverdrup Basin, Arctic Canada by Joel P. Bensing, Noel P. James, and Benoit Beauchamp 

Highlights - The Poop on Shoreline Change

Recent studies have shown that many shorelines around the world, especially in densely populated areas, are eroding, in many cases due to the impact of humans.  In this new study, Seigguh examines the role of some non-bio-degradable materials on mitigating shoreline erosion.  By examining the transport thresholds and coefficients for a series of materials, the results illustrate that dirty diapers represent largely immobile elements, are abundant anyway, and actually provide a protective barrier against shoreline erosion.  The authors suggest that many beaches, especially those in populated regions, should be armored with diapers to prevent coastal erosion.

Transport and deposition of non-biodegradable materials protect shorelines: A case study by B.M. Seigguh

Highlights—Alluvial Plain Architecture on the Stage

Modern stratigraphic analysis utilizes unconformity-bounded, genetically related units to subdivide and then interpret stratigraphic successions.  In alluvial plain deposits, an important challenge represents means to subdivide and date the complex internal stratigraphy.  Here, De Santis et al. use physical sedimentologic characterization, coupled with amino acid racemization (AAR) and ¹⁴C dating, to recognize and date Quaternary units in an Italian alluvial plain to the scale of marine isotope stages.  Detailing and dating stratigraphy to this level reveals the influences of subsidence events, climate variability, and sea-level change on the region.  This level of resolution is interpreted to represent an important advance, compared to other Quaternary alluvial fan successions that are subdivided and dated using their relative stratigraphic position alone.

Unconformity-bounded stratigraphic units (UBSUs) in an Italian alluvial-plain area: recognizing and dating by Vincenzo De Santis, Massimo Caldara, Luigi Pennetta, Trinidad Torres, and José Eugenio Ortiz

Highlights—Tropical Storms Shape Deltas

Deltas represent generally lobate sediment accumulations formed by sediment from rivers that empty into standing bodies of water.  In these settings, storms and tropical cyclones can represent events of high energy.  To assess the role storms in formation of deltas, Garrison et al. compare the timing of the deposition of stratigraphic units, constrained by 137Cs geochronology and historical aerial photographs, and the historical record of storms in the Holocene Gum Hollow Delta (Nueces Bay, Texas Gulf of Mexico).  Results indicate that broadly coarsening- then fining-upward bedsets, interpreted to represent waxing- and waning-flow phases interpreted to represent hyperpycnal deposits.  Comparison with historical records and aerial photos reveal that these deposits are associated with tropical cyclone landfalls throughout the 80-year historical record.  These results suggest that such deposits can be used as a tool to investigate climate records in sedimentary successions in small estuarine and lagoonal deltas.

Record of historical Gulf of Mexico storms preserved in the stratigraphy of Gum Hollow Delta, Nueces Bay, Texas, U.S.A.: an example of tropical-cyclone-induced hyperpycnal deposition by James R. Garrison, Jr., Sara Potter Miller, Alberto M. Mestas-Nuñez, and Joshua Williams

Highlights—Persistent Fractures and Diagenesis

Syndepositional deformation features can impact depositional geometries, but can they also represent fluid conduits active throughout a strata's entire history? In this paper, Budd et al. address this question using petrographic, geomechanical, and clumped-isotope analysis of diagenetic products in syndepositional fractures (Permian, Guadalupe Mountains, New Mexico, USA).  Results show that the complex diagenetic fills in the fractures are multigenerational, and represent numerous, repeated fracture openings, fills, and reactivation over ~260 Ma since deposition.  The results highlight the potential for re-activated syndepositional fractures in a carbonate platform to dominate fluid flow in that platform and to drive the diagenetic history of adjacent host rocks.

Syndepositional deformation features in high-relief carbonate platforms: long-lived conduits for diagenetic fluids by David A. Budd, Edmund L. Frost, III, Katharine W. Huntington, and Patricia F. Allwardt

Highlights—Grain Shape in Antarctica: the Cold, Hard Truth

The shapes of sedimentary particles can be useful for elucidating many aspects of their history, from origin to deposition to diagenesis.  Livsey et al. examine the utility of grain shape as a depositional proxy for glacially influenced sediment within the James Ross Basin and Joinville Plateau of the Antarctic Peninsula from the Eocene to the present.  The results from Fourier shape analyses of more than 6,000 quartz grains reveal changes through time, associated with climate shifts.  It shows that grain roughness increases with the onset of increased glaciation from the Late Oligocene to Middle Miocene, after an Early Pliocene warm period, and from the Pliocene to Pleistocene; in contrast, grain roughness decreases from the Middle Miocene through an Early Pliocene warm period. This study highlights the utility of Fourier grain-shape analysis for understanding the history of grains, and its potential application in polar studies.

Fourier grain-shape analysis of Antarctic marine core: the relative influence of provenance and glacial activity on grain shape by Daniel N. Livsey,  Alexander R. Simms, Warren G.  Clary, Julia S. Wellner, John B. Anderson, and John P. Chandler

Highlights—Biomineralization

Recently, numerous studies have examined the possible role of bacterially induced mineral precipitation (organomineralization).  Laboratory studies represent an important means to explore these processes, but Gallagher et al. reveal how the presence of phosphate in media (needed for microbial growth) may affect rate, morphology and mineralogy of precipitated minerals.  The results of this study reveal potential pitfalls that could cause misinterpretation of laboratory biomineralization experiments.

Phosphate-related artifacts in carbonate mineralization experiments by Kimberley L. Gallagher, Olivier Braissant, Tristan J. Kading, Christophe Dupraz, and Pieter T. Visscher

Highlights—Unraveling Sediment Mixing

Mixed carbonate-siliciclastic sediments can provide unique interpretive challenges, as the two types of sediments are controlled by different parameters.  In this paper, Chiarella and Longhitano describe the application of a new technique for describing and interpreting sediments of mixed systems.  The application of this method to a succession of Plio-Pleistocene deposits facilitated the reconstruction of the depositional framework and stratigraphic evolution, revealing otherwise ambiguous patterns.  These techniques and results illustrate a new means to evaluate mixed carbonate-siliciclastic systems and their dynamics.  

Distinguishing depositional environments in shallow-water mixed, bio-siliciclastic deposits on the basis of the degree of heterolithic segregation (Gelasian, southern Italy) by Domenico Chiarella and Sergio G. Longhitano

Highlights—Dolomite: It’s the Fault’s Fault

A unique aspect of carbonate platforms is their ability to develop flanks with gradients that exceed the angle of repose due to early cementation and binding.  Frost et al. document a Permian example of an oversteepened carbonate platform margin that was impacted by early syndepositional deformation.  A suite of field, petrographic, and stable isotopic data reveal that these early fractures and faults also facilitated the flow of early dolomitizing fluids.  These results are interpreted to reveal a spatially and temporally complex alteration of host limestone that led to bed-scale heterogeneity in dolomite patterns and petrophysical properties.

Syndepositional deformation in a high-relief carbonate platform and its effect on early fluid flow as revealed by dolomite patterns by Edmund L. Frost, III, David A. Budd, and Charles Kerans

Highlights—Don’t Underestimate Perms (with apologies to Charles Nessler)

Predicting the permeability of subsurface sandstone bodies is a major challenge for petroleum production and ground water management. In this study, Walderhaug et al. test several methods of permeability prediction using almost 1900 samples from the Norwegian continental shelf and the Fontainebleau Sandstone.  The data indicate that for clay-free and very clay-poor sandstone, permeability can be calculated with the Kozeny equation.  In contrast, for sandstones containing more than ~ 3% clay, a modified Kozeny equation that accounts for pore system geometry provides more accurate results for sandstone with higher clay contents.  These results emphasize the hazards of predicting permeability from grain size and porosity alone, and illustrate the complexity of permeability-porosity relations in sandstones with clays.

Prediction of permeability in quartz-rich sandstones: examples from the Norwegian continental shelf and the Fontainebleau Sandstone by Olav Walderhaug, Arild Eliassen, and Nils Einar Aase