Continental
carbonates are distinct from their marine cousins, but like them, contain
numerous proxies for the environment in which they formed. Yet, continental
carbonates can be of two general types: those formed ambient temperature from
calcium bicarbonate–enriched waters and those associated with hyperalkaline
thermal springs, from fluids commonly depleted in dissolved inorganic carbon. Both
are favored under distinct conditions, yet how closely they each reflect their
environment is unclear. To better understand these complexities, Leleu and others examined
travertine forming at DIC-depleted hyper-alkaline springs with pH up to 12.
Their multi-disciplinary approach ranged from macroscopic to microscopic scale,
analyzing travertine samples to assess the relationship between the petrologic
features and fabrics and the geochemical and isotopic signatures. The results
illustrate the potential of these deposits as proxies of past climatic record
and atmospheric CO2 sequestration.
In
providing clues of since-leveled landscapes, the stratigraphic record records
tectonic evolution. In this study, Uddin et al. integrate
petrographic, detrital-geochronologic, and mineral-chemistry analyses of
detrital minerals and lithic clasts of the Pennsylvanian Pottsville Formation,
part of a clastic wedge in the foreland basin in Alabama and Mississippi.
This manuscript illustrates that this part of the foreland basins received
detritus mostly from the Appalachians, rather than the Oucahitas, and draws an
analogy to the modern Himalayan-Bengal system. The mineralogy and dates
suggest an initial Blue Ridge Piedmont source, followed by a migrating steep
erosional front that buried previously eroded terrains; alternatively, some of
the variations may result from along-strike transport of detrital material in
the foreland basin.
Porten and others show how reservoir quality of deep-marine
sandstones is controlled by sediment composition, transport, and depositional
histories in a range of sediment-gravity-flow deposits in a Maastrichtian
submarine-fan in the Vøring Basin (Norwegian Sea, Norwegian continental shelf).
In these strata, porosity increases with decreasing clay content, and
permeability increases with increasing grain size, decreasing clay volume, and
increasing porosity. Porosities of the different depositional bed types are
similar, whereas permeabilities are distinct, with high-density turbidites
having permeabilities approximately two orders of magnitude higher than
clay-rich hybrid event beds. The results of this study emphasize the importance
of the transport and depositional processes responsible for producing different
bed types with characteristic composition and texture. This step is
essential in reservoir evaluation, necessary for predicting most likely
porosity and permeability evolution with sediment burial and for understanding
reservoir quality distribution in potential deep-marine siliciclastic
hydrocarbon reservoir targets.
To expl're the genesis of the Gosp'rt Sand, an
Eocene greensand deposit from the U.S. Gulf coastal plain, Pietsch and
co-auth’rs integrateth sedimentology, the min'ralogy, taxonomic and
ecological analysis, and taphonomic hist'ry o’ the mollusk fauna. The results
bewray yond this glauconite-rich sand enwheels hyp'r-div'rse mollusk fauna,
int'rpret'd to representeth deltaic inn'r shallow shelf to ope soundeth
environments. Although glauconite-rich shell beds art int'rpret'd to beest
fav'r'd by transgression, the ov'rall stratigraphy wast influenc'd by delta
progradation, subsidence, and shifting sea-level. This w'rk may representeth
analogs to oth'r glauconitic and fossil bearing h'rizons throughout the
paleogene gulf and atlantic coastal plain, and oth'r greensand h'rizons
throughout the geologic rec'rd.
Alluvial
architecture includes describing stacking patterns, spatial density of fluvial
channel-belt sandstone bodies, and connectivity, aspects shaped by influences
of autogenic and allogenic processes. This study by Benhallam et al. attempts
to understand the relative roles of allogenic and autogenic factors on the
fluvial John Henry Member of the Straight Cliffs Formation (Cretaceous) of the
southwestern Kaiparowits Plateau of Utah. To attempt to discriminate between
local and regional controls, this study uses a suite of spatial algorithms to
quantify and statistically discriminate clustered, uniform, or random
channel-belt bodies in several outcrops. By comparison with predictions from
various experimental and numerical models of alluvial architecture, the
existence of different patterns at different spatial scales implicates avulsion
reoccupation at the small scale, and avulsion-driven compensational stacking at
a larger scale. This study suggests that specific types of channel stacking
patterns provide insights into the underlying controls and depositional
processes, such as compensational stacking and avulsion reoccupation.
Although
that dastardly diagenesis plays a role, many of the same depositional factors
that control sequence stratigraphy also influence the composition of sandy sediment
within those sequences. Taking this concept as a starting point, Tentori and others unravel
relationships between siliciclastic sediment composition (petrofacies) and
sequence stratigraphic systems tracts of the Quaternary sedimentary succession
of the Roman Basin. The results document different quartz/feldspar and
quartz/lithic ratios, and textural changes, among systems tracts. These
changes are interpreted to represent the influences of hydraulic sorting (by
various processes among systems tracts) and post-depositional in situ weathering,
and are linked to tectonics, volcanism, and relative changes in sea
level. The data show how a sedimentary petrographic approach can be used
to derive information on the stage evolution of a sedimentary succession
through time. These results might be directly applicable to petroleum
exploration and production in wave-dominated deltaic succession.
Although recently some have lamented the “demise” of carbonate
geology, practictioners in the field are not ones to let it die. Instead of
re-hashing what he considers to be more mundane aspects of carbonate
depositional systems, or argumentative aspects of cyclostratigraphy, Bruce Wilkinson starts from the
premise that “so much of carbonate sedimentology is crap” to develop the
concepts and applications of the future of carbonate geology—peloids and
pelotherapy. The Medical Subject Headings (MeSH) database of
the MEDLINE/PubMed defines pelotherapy as “The therapeutic use
of mud in packs or baths taking advantage of the absorptive qualities of the
mud. It has been used for rheumatism and skin problems.” Building on efforts of clay mineralogists, Wilkinson
argues that pelotherapy can take three approaches: 1) Geophagy, which utilizes the healing power of
the calcium carbonate-organic mix, but which can become addictive; 2) Psammotherapy (sand baths) useful for muscular-skeletal
diseases; and 3) Cosmetics, providing for a strong skrabiruyuschy effect. The
manuscript notes a niche (but growing) peloid travel destination,
clear relevance for modeling, and a strong and growing market –
after all, who doesn’t love a good peloidal mud bath?
