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<jats:title>ABSTRACT</jats:title><jats:p>Braided rivers have accumulated a dominant fraction of the terrestrial sedimentary record, and yet their morphodynamics in proximal intermountain reaches are still not fully documented—a shortcoming that hampers a full understanding of sediment fluxes and stratigraphic preservation in proximal-basin tracts. Located in the eastern Canadian Cordillera near the continental divide, the Kicking Horse River is an iconic stream that has served as a model for proximal-braided rivers since the 1970s. Legacy work on the river was based solely on ground observations of small, in-channel bars; here we integrate field data at the scale of individual bars to the entire channel belt with time-lapse remote sensing and ground-penetrating-radar (GPR) imaging, in order to produce a more sophisticated morphodynamic model for the river.</jats:p><jats:p>Cyclical discharge fluctuations related to both diurnal and seasonal variations in melt-water influx control the planform evolution and corresponding stratigraphic signature of trunk channels, intermittently active anabranch channels, and both bank-attached and mid-channel bars. Three-dimensional GPR fence diagrams of compound-bar complexes are built based on the identification of distinct radar facies related to: i) accretion and migration of unit bars, ii) both downstream and lateral outbuilding of bar-slip foresets; iii) buildup of bedload sheets, iv) channel avulsion, and v) accretion of mounded bars around logs or outsized clasts. Trends observed downstream-ward include decreases in gradient and grain size decreases, trunk-channel shrinkage, intensified avulsion (with increase in abundance for anabranch channels), and a shift from high-relief to low-relief bar topography. The integration of ground sedimentology, time-lapse remote sensing, and GPR imaging demonstrates that proximal-braided streams such as the Kicking Horse River can be critically compared to larger systems located farther away from their source uplands despite obvious scale differences.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>There is a significant difference between the average sedimentation rate of a lengthy stratigraphic section spanning many millions of years, and the rate that can be calculated from any short segment within such a section, such segments typically yielding rates several orders of magnitude more rapid than the overall rate. Stratigraphic successions contain numerous surfaces of nondeposition and erosion representing time spans from minutes to many millions of years, which collectively may account for as much as 90% of the total elapsed time that the succession represents. The stratigraphic record is constructed by a range of geological processes that operate over all time scales from seconds to billions of years, and at rates that vary by ten orders of magnitude. The generation of the stratigraphic record can be conceptualized in the form of a mechanical device, which we term the “Stratigraphy Machine.”</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Lake-margin lacustrine carbonates of the Green River Formation, in the eastern Uinta basin of Colorado and Utah, occur interbedded with fluvial and shoreline-parallel sandstone and shale. Microbial bindstones were deposited in a saline-alkaline lake during and after the Early Eocene Climate Optimum (EECO) (52–50 million years ago) that is characterized by global hot-house conditions, elevated atmospheric CO2, and highly fluctuating climate conditions. The stratigraphic architecture, chemostratigraphy, and morphology of the microbialites and other associated carbonate beds can be related to these climatic conditions. Three facies associations are recognized in the carbonate units across the lake margin from upper littoral to lower sublittoral environments: facies association 1, delta proximal non-microbial carbonates, characterized by quartzose bioclastic, peloidal, intraclastic packstones and grainstones–rudstones, quartose peloid wackestones and sandy oil shale; facies association 2, microbialite associated non-microbial carbonates, composed of ostracod, ooilitic, peloidal packstones–grainstones and intraclastic packstones, grainstones and rudstones; and facies association 3, microbial carbonates, consisting of diverse forms of stromatolitic and thrombolitic lithofacies.</jats:p> <jats:p>Multiple scales of carbonate cyclicity are suggested by shifts of δ18O and δ13C stable isotopes and deepening-upward microbialite facies. High-frequency cycles, on the order of 1 to 5 m thickness, are characterized by positive shifts in stable isotopes and interpreted deepening trends from littoral to lower sublittoral conditions. Large-scale trends, on the order of tens to hundreds of meters thickness record long-term lake changes, including: 1) sparse microbialite deposition during initial fresh conditions in lake stage 1, with low macro-structure diversity and light δ18O and δ13C isotope values; 2) transitional lake stage 2 corresponding to moderate macro-structural diversity, large meter-scale biostromal and biohermal buildups, and a positive shift in δ18O and δ13C isotope values that suggest increasing saline and alkaline conditions; 3) a highly fluctuating lake stage 3 that contains the highest microbialite macro-structural diversity and marks the interval of heaviest δ18O and δ13C isotope values, suggesting the greatest lake restriction, and the highest salinity and alkalinity conditions; and 4) a rising lake stage 4 that marks the lowest microbialite macro-structure diversity and a reversal in trend of δ18O and δ13C isotope values, that indicate deepening and freshening conditions.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>Mixed siliciclastic–carbonate sediments in the distal settings of marine systems (i.e., offshore and basin areas) are the result of the complex interaction between production of benthic and pelagic biogenic carbonates and the exportation of terrigenous, and/or carbonate mud from shallow-marine settings. Thus, the origin of mud (particles &amp;lt; 63 mm) of different compositions and the processes responsible for mixing them play a key role in the final distal deposits of mixed systems. Although the understanding of these topics in shallow settings has made significant progress, one of the critical issues is to recognize them in the offshore and basinal settings for understanding the link between shallow-marine and deep-marine areas. In this study, a thick Lower Cretaceous succession (330–650 m) of the Neuquén Basin, composed mostly of mixed (siliciclastic–carbonate) fine-grained marine deposits, was studied through a high-resolution analysis of petrography, SEM analysis, and mineralogy, to define and characterize the origin of carbonate and terrigenous mud as well as to characterize the processes involved in the mixing of terrigenous and carbonate mud on a storm-dominated ramp. Contrary to previous suggestions, most of the carbonate recognized in the basinal setting is composed of silt- to sand-size skeletal remains and micrite (micarbs) and is likely derived from a pelagic biogenic factory combined with carbonate derived from the maceration of benthic organism. Furthermore, micarbs are possibly diagenetic in origin but with a distally produced carbonate precursor. In contrast, the siliciclastic fraction is entirely detrital, being silt-size quartz particles and clay minerals (mainly illite) the most important constituents. Most of the terrigenous mud delivered from shallow areas acts to dilute the distally produced carbonate mud. However, a bloom of carbonate production able to dilute terrigenous supply is recorded, and its origin is likely triggered by the input of waters charged with nutrients from the paleo–Pacific Ocean in addition to nutrients derived from proto-Andes volcanic activity. This demonstrates that the relation between the terrestrially derived siliciclastic components and the biogenically produced carbonates in mixed systems is not linear, but a complex interaction of climate, sea-level, origin of the components, and hydrography of the basin, among others.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>At the Castle Creek study area a superbly exposed continental-slope channel-complex set of the Isaac Formation termed ICC1 crops out. ICC1 is 220 m thick and exposed over 5 km parallel to bedding and consists of four vertically stacked channel complexes—lower channel complex (LC), and three upper channel complexes (termed UC1–UC3). Based on differences in lithological and textural makeup, and stratal trends, two styles of channel fill and stacking pattern are recognized—disorganized stack of bottom-up channel fills (LC, UC1, and UC2), and organized lateral-offset stack of laterally accreting channel fills (UC3). Bottom-up channel fills show an upward and axis-to-margin fining and thinning, and were filled by poorly sorted, density-stratified flows. In contrast, channel fills of UC3 exhibit negligible upward and lateral fining and thinning and were filled by flows enriched in coarse and very coarse sand and were only negligibly stratified in their lower part. Accordingly, the lower, depositionally important part of the flow had a plug-like density profile with limited overspill that caused circulation patterns in channel bends to resemble those in rivers. Notably, the grain-size makeup of late-stage channel fills of UC3 indicates a change in the makeup of the sediment supply, namely grain size and sorting. Note that this systematic upward change in sediment texture and channel type is observed in most (5 of 8) Isaac slope channel-complex sets at the Castle Creek study area. These changes reflect a change from hinterland- to shelf-dominated sediment supply interpreted to be associated with a long-term rise of relative sea level that progressively expanded continental-shelf accommodation and retention of coarse relict and palimpsest sediment. During short-term relative sea-level falls this increasingly voluminous source of coarse, moderately well-sorted siliciclastic and minor carbonate sediment eventually came to dominate the supply of coarse sediment to the shelf edge, and in turn, controlled the character of turbidity currents that remobilized sediment farther down the continental slope and possibly onto the basin floor.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>The Krkonoše Piedmont Basin, an early post-Variscan basin (c. 310–280 Ma) located in the NE Bohemian Massif (Czech Republic, central Europe), contains up to 300-m-thick non-marine Lower Permian (Asselian) deposits of the Vrchlabí Formation that crop out in its western part. The Early Permian Krkonoše Piedmont Basin exhibits striking similarities—in terms of tectonostratigraphic evolution, depositional patterns, and volcanism—to other early post-Variscan, near-equatorial intermontane basins. This work focuses on sedimentological analysis of the Vrchlabí Formation using outcrop data, combined with borehole and newly acquired field gamma spectrometry data. The formation consists predominantly of fluvial deposits in the southern part of the basin that pass laterally into deltaic and lacustrine deposits of the Rudník Member, located in the central part of the basin. Fluvial deposits are formed by sandstone and conglomeratic bodies, decimeters to several meters thick, interpreted as single-story and multi-story channel fills as well as various macroforms (e.g., bars) deposited by a low-sinuosity fluvial system. Channel fills intercalate with floodplain deposits centimeters to few meters thick. Vertically, the studied fluvial succession is divided into five intervals based on i) variable preservation ratio between channel fill and floodplain deposits and ii) external and internal geometries of sandstone and conglomerate channel bodies. In order to explain the observed vertical changes in fluvial style and to determine the main controlling factors, the interaction of the fluvial system with the contemporaneous lake was investigated by interpreting base-level changes of the fluvial system and their correlation with lake level changes. In the central part of the basin the transition from fluvio-deltaic to lacustrine deposits is represented by alternating beige to gray sandstones centimeters to few meters thick and by dark gray mudstones up to several meters thick that pass northwards into shales. At the outcrop scale, the new sedimentological data in combination with newly acquired gamma-ray logs enabled tracing the lateral extent of individual fluvial bodies. The integration of the new data with older borehole data leads to a substantially better understanding of lateral and vertical relationship between the fluvio-deltaic and the lacustrine facies at the basin scale. Tectonic subsidence played a substantial role during the initial deposition of the Vrchlabí Formation. However, the external geometries, the internal architecture of fluvial channel bodies, and the variable degree of floodplain preservation throughout the entire Vrchlabí Formation cannot be explained by tectonics only, but requires the consideration of climatic controls. The Early Permian fluvial system is interpreted to reflect seasonal discharge variability with dry and wet periods under long-term subhumid climatic conditions that shifted towards more arid conditions during the latest depositional stage of the Vrchlabí Formation.</jats:p>

<jats:title>ABSTRACT</jats:title> <jats:p>The lower Pennsylvanian Pottsville Formation, in the Appalachian foreland basin, constitutes a late Paleozoic clastic wedge formed close to the Appalachian orogenic belt. In this study, we analyzed Pottsville sandstone from the western bituminous and eastern anthracite fields in Pennsylvania to evaluate the detrital history of the sediments. Petrographic modal analyses show that sandstone in the western bituminous field ranges from quartzarenite to sublitharenite, with mean composition of Qt84F1L15; sampled sandstone from the eastern anthracite field is dominated by sublitharenite to litharenite with mean composition of Qt70F2L29. Heavy-mineral assemblages from both fields are dominated by ultrastable minerals (zircon, rutile, and tourmaline), apatite, sphene, spinel, siderite, and abundant opaques. Almost all the studied sandstone samples are garnet-depleted except one from the eastern anthracite field. The chemical composition of chromium- and zinc-rich spinel in samples from both fields might suggest exhumation of an arc terrane and ophiolitic belt with ultramafic igneous rocks. Particularly, the ternary plot of Fe3+–Cr3+–Al3+ end members for the chrome spinels possibly suggest a derivation from an alpine-type peridotite complex. Laser 40Ar/39Ar analyses of detrital muscovite from eastern anthracite fields and western bituminous fields record separate ages, with the former characterized by prominent Middle to Late Ordovician Taconic and Middle Devonian Acadian ages with two discrete modes at 463 and 369 Ma, and the latter dominated by Late Ordovician Taconic, Middle Devonian Acadian, and Late Devonian Neoacadian ages with discrete modes at 445, 397, 360, and 351 Ma. The new data suggest that early Pennsylvanian sedimentation in the Appalachian foreland basin was controlled by southward, southwestward, and westward drainage systems that originated in the Appalachian orogenic belt to the east and northeast.</jats:p>