Hyperpycnal Rivers and Prodeltaic Shelves in the Cretaceous Seaway of North America

Bhattacharya, Janok P.; MacEachern, James A.

doi:10.2110/jsr.2009.026

Cited by 367 publications

(354 citation statements)

References 141 publications

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“…Palaeohydraulic calculations are routinely used in interpreting ancient fluvial deposits [20][21][22][23][24][25][26][27] , despite some critical challenges 28,29 , which are rather generic to quantitative understanding of complex earth surface processes.…”

Section: Methodsmentioning

confidence: 99%

“…In particular, recent advancements in palaeohydraulics [24][25][26][27]29 allowed us to calculate palaeochannel dimensions and their palaeo discharges from channelized sandstones deposited at 4.4 Myr at Aramis, Ethiopia. We targeted two channelized sandstone intervals just below (henceforth called lower channel) and above (henceforth called upper channel) the DABT (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Given that a channel cross-section is not rectangular and rather curved, the actual A is approximately 0.65(w×d m ) (Supplementary Table S2) 27 . Channelized sandstones of the studied successions are predominantly fine-grained sands (0.13-0.25 mm), containing mainly dune-scale cross-strata.…”

Section: Methodsmentioning

confidence: 99%

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River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago

Gani

2011

Nat Commun

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The nature and type of landscape that hominins (early humans) frequented has been of considerable interest. The recent works on Ardipithecus ramidus, a 4.4 million years old hominin found at middle Awash, Ethiopia, provided critical information about the early part of human evolution. However, habitat characterization of this basal hominin has been highly contested. Here we present new sedimentological and stable isotopic (carbon and oxygen) data from Aramis, where the in situ, partial skeleton of Ar. ramidus (nicknamed 'Ardi') was excavated. These data are interpreted to indicate the presence of major rivers and associated mixed vegetations (grasses and trees) in adjacent floodplains. our finding suggests that, in contrast to a woodland habitat far from a river, Ar. ramidus lived in a river-margin forest in an otherwise savanna (wooded grassland) landscape at Aramis, Ethiopia. Correct interpretation of habitat of Ar. ramidus is crucial for proper assessment of causes and mechanisms of early hominin evolution, including the development of bipedalism.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago

Gani

2011

Nat Commun

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“…Many shales exhibit mm/cm-scale cross-and parallel-laminations, scour surfaces, particle alignment parallel to bedding planes, and burrows [2][3][4][5][6][7] (Figure 1). Some shales reveal a systematic finingupward or coarsening-upward, followed by fining-upward grain-size pattern [8] while others display a systematic stacking pattern of lithofacies that indicate tempo- Thin section photomicrograph of a graded, spiculite mudstone from lamination shown in A. C. Laminations within cored interval.…”

Section: Shale Depositional Processesmentioning

confidence: 99%

“…From these and other studies, a list of potential transport, deposition, and reworking processes include (in addition to hemipelagic rain): (1) hyperpycnal flows [5,8,11,12], (2) turbidity current flows, (3) tempestites (storm deposits) and wave-reworked deposits [6]; and (4) contourites (bottomhugging slope, oceanic currents) [2]. In order for claysized particles to move along the sea floor by tractive processes, as evidenced by the sedimentary structures, they must behave in a hydraulically similar manner to coarser grains.…”

Section: Shale Depositional Processesmentioning

confidence: 99%

Important geological properties of unconventional resource shales

Slatt

2011

Open Geosciences

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Abstract:The revelation of vast global quantities of potentially productive gas and oil-prone shales has led to advancements in understanding important geological properties which impact reservoir performance. Based upon research on a variety of shales, several geological properties have been recognized as being common and important to hydrocarbon production.(1) transport/depositional processes include hemipelagic 'rain', hyperpycnal flows, turbidity current flows, tempestites , wave-reworking, and contour currents in both shallow and deep water settings. (2) Common shale minerals include clays, quartz, calcite, dolomite, apatite, and pyrite; organic constituents include spores (Tasmanites), plant remains, biogenic quartz and calcite, and arenaceous foraminifera. (3) Porosity and permeability are characteristically low with pore sizes ranging down to the nanoscale. Main pore types include intergranular (including pores within clay floccules), porous organic matter, porous fecal pellets, and microfractures. (4) Important geochemical characteristics include organic richness (>3%), maturity (>1.1%Ro for shale gas and 0.6-0.9% for shale oil) and type (I-IV), in addition to certain biomarkers which are indicators of bottom water oxicity during deposition. Remaining hydrocarbon potential [RHP = (S1 + S2)/TOC] also reflects temporal environmental changes. 'Isotopic reversals' can be used to detect best producing areas in shale-gas plays. (5) Lithofacies stacking patterns and sequence stratigraphy are the result of eustatic depositional history. A general sequence stratigraphic model is presented here that highlights this commonality. (6) Geomechanical properties are key to drilling, fracturing and production of hydrocarbons. Brittle-ductile couplets at several scales occur in shale sequences. (7) Geophysical properties, when calibrated to rock properties, provide a means of regionally to locally mapping the aforementioned properties. (8) Economic and societal considerations in the exploration and development of resource shales are garnering attention. Many potentially economic shale-gas and shale-oil plays are being identified globally. Risks and uncertainties associated with gas-and oil-rich shales include the lack of long-term production histories, environmental concerns related to hydraulic fracturing, uncertainty in calculating hydrocarbons-in-place, and fluctuations in supply, demand, and price.

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Identifying autogenic sedimentation in fluvial‐deltaic stratigraphy: Evaluating the effect of outcrop‐quality data on the compensation statistic

et al. 2017

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Stratigraphy preserves an extensive record of Earth‐surface dynamics acting over a range of scales in a variety of environments. To take advantage of this record, we first must distinguish depositional patterns that arise due to intrinsic (i.e., autogenic) landscape dynamics from sedimentation that results from changes in climate, tectonic, or eustatic boundary conditions. The compensation statistic is a quantitative tool that has been used to estimate scales and patterns of autogenic sedimentation in experimental deposits; it has been applied to a few outcrop studies, but its sensitivity to data limitations common in natural deposits remains unconstrained. To explore how the compensation statistic may be applied to outcrop data, we evaluate the sensitivity of the tool to stratigraphic data sets limited in extent and resolution by subsampling an autogenic experimental deposit to create pseudo‐outcrop‐scale data sets. Results show that for data sets more than 3 times thicker than a characteristic depositional element (e.g., channel or lobe), the compensation statistics that can be used reliably constrain the maximum scale of autogenic sedimentation even for low‐resolution data sets. Additionally, we show that autogenic sedimentation patterns may be characterized as persistent, random, or compensational using the compensation statistic when data sets are high resolution. We demonstrate how these measurements can be applied to natural data sets with comparative case studies of two fluvial and two deltaic outcrops. These case studies show how the compensation statistic can provide insight into what controls the maximum scale of autogenic sedimentation in different systems and how landscape dynamics can produce organized sedimentation patterns over long time scales.

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Hyperpycnal Rivers and Prodeltaic Shelves in the Cretaceous Seaway of North America

Cited by 367 publications

References 141 publications

River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago

River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago

Important geological properties of unconventional resource shales

Identifying autogenic sedimentation in fluvial‐deltaic stratigraphy: Evaluating the effect of outcrop‐quality data on the compensation statistic

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