scholarly journals A new stratigraphic framework and constraints for the position of the Paleocene–Eocene boundary in the rapidly subsiding Hanna Basin, Wyoming

Geosphere ◽  
2020 ◽  
Vol 16 (2) ◽  
pp. 594-618
Author(s):  
Marieke Dechesne ◽  
Ellen D. Currano ◽  
Regan E. Dunn ◽  
Pennilyn Higgins ◽  
Joseph H. Hartman ◽  
...  
Keyword(s):  
Sediment Accumulation ◽  
Stratigraphic Framework ◽  
Thermal Maximum ◽  
Laramide Orogeny ◽  
Carbonaceous Shales ◽  
Bulk Organic Matter ◽  
Climatic Event ◽  
Hanna Basin ◽  
Depositional Setting ◽  
High Sediment

Abstract The Paleocene–Eocene strata of the rapidly subsiding Hanna Basin give insights in sedimentation patterns and regional paleogeography during the Laramide orogeny and across the climatic event at the Paleocene–Eocene Thermal Maximum (PETM). Abundant coalbeds and carbonaceous shales of the fluvial, paludal, and lacustrine strata of the Hanna Formation offer a different depositional setting than PETM sections described in the nearby Piceance and Bighorn Basins, and the uniquely high sediment accumulation rates give an expanded and near-complete record across this interval. Stratigraphic sections were measured for an ∼1250 m interval spanning the Paleocene–Eocene boundary across the northeastern syncline of the basin, documenting depositional changes between axial fluvial sandstones, basin margin, paludal, floodplain, and lacustrine deposits. Leaf macrofossils, palynology, mollusks, δ13C isotopes of bulk organic matter, and zircon sample locations were integrated within the stratigraphic framework and refined the position of the PETM. As observed in other basins of the same age, an interval of coarse, amalgamated sandstones occurs as a response to the PETM. Although this pulse of relatively coarser sediment appears related to climate change at the PETM, it must be noted that several very similar sandstone bodies occur with the Hanna Formation. These sandstones occur in regular intervals and have an apparent cyclic pattern; however, age control is not sufficient yet to address the origin of the cyclicity. Signs of increased ponding and lake expansion upward in the section appear to be a response to basin isolation by emerging Laramide uplifts.

Sequence stratigraphy of the late Carboniferous Clifton Formation, New Brunswick

2020 ◽  
Vol 57 (11) ◽  
pp. 1289-1304
Author(s):  
Brandon M. Keough ◽  
Olivia A. King ◽  
Matthew R. Stimson ◽  
Page C. Quinton ◽  
Michael C. Rygel
Keyword(s):  
New Brunswick ◽  
Sediment Supply ◽  
Sequence Stratigraphic ◽  
Marine Strata ◽  
Stratigraphic Framework ◽  
Carbonaceous Shales ◽  
Study Interval ◽  
Maritimes Basin ◽  
Sequence Boundaries ◽  
Maximum Flooding Surface

The Maritimes Basin of Atlantic Canada contains a rich record of Pennsylvanian cyclothems. Previous studies have focused on rapidly subsiding depocenters in the central part of the basin where Carboniferous successions feature cyclic alternations between terrestrial and marginal marine strata. In contrast, the Pennsylvanian Clifton Formation was deposited on the relatively stable New Brunswick platform and contains almost entirely terrestrial strata. Although early studies of the Clifton Formation noted a cyclic architecture, particularly within Member B, this unit has remained understudied. We provide a sedimentological and sequence stratigraphic framework for the lower 85 m of Member B and interpret our results relative to a broader regional framework. Near the base of the study interval, the highstand systems tract is composed of red floodplain mudrocks; overlying sequence boundaries are composed of calcretes and (or) channels. The transgressive systems tract and maximum flooding surface are represented by coals and aquatic bivalve-bearing mudrocks. Moving upward through the section, the architecture of the highstand systems tract remains largely unchanged while sequence-bounding paleosols become less well developed, the transgressive systems tract becomes thinner and eventually not preserved, and the maximum flooding surface is only occasionally preserved, possibly represented by carbonaceous shales. These changes in cyclic architecture may be attributed to changes in the magnitude of glacioeustatic fluctuations, climate, and (or) the accommodation/sediment supply ratio. The results of this study show that the Clifton Formation represents the terrestrial/proximal endmember for cyclicity in the Maritimes Basin and provide new insight into paleotopography as a possible control on cyclothem architecture.

Mapping sediment carbon in a large tropical reservoir: burial of terrestrial and aquatic organic carbon, and occurrence of potential methane ebullition hot spots

2020 ◽  
Author(s):  
Sebastian Sobek ◽  
Raquel Mendonça ◽  
Anastasija Isidorova ◽  
Charlotte Grasset
Keyword(s):  
Organic Carbon ◽  
Spatial Variability ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Sediment Flux ◽  
Lipid Biomarkers ◽  
Gas Bubble ◽  
Tropical Reservoir ◽  
Global Average ◽  
High Sediment

<p>Reservoirs efficiently trap the riverine sediment flux, and therefore rapidly accumulate sediment. Since the sediments contain organic carbon (OC), reservoirs globally store significant amounts of OC in their sediments. The source of the OC buried in reservoir sediments is currently not well-known, but has important implications for the accounting of reservoir C burial as a new anthropogenic C sink. On the other hand, sediment OC can be degraded to the greenhouse gas methane (CH4) in anoxic sediment layers, and at high sediment accumulation rates, CH4 reaches oversaturation and forms gas bubbles which efficiently transport CH4 to the atmosphere. Accordingly, CH4 ebullition (bubble emission) is the main pathway of the globally significant CH4 emission by reservoirs. Both sediment OC accumulation and CH4 production is spatially extremely heterogeneous in reservoirs, and we currently lack understanding of the drivers of this spatial variability. We therefore mapped the spatial variability of sediment OC accumulation and of gas bubble-rich, CH4-oversaturated sediments in a large (1300 km2) tropical reservoir in Brazil, using both seismic sub-bottom profiling and sediment coring. In addition, we performed analyses of the sediment stable isotopic signature (13C and 15N) and lipid biomarkers (alkanes, alkanols, and acids) in order to discern the origin of the buried OC. We found that the OC accumulation rate was strongly dependent on the sedimentation rate, which in turn varied with water depth, bottom slope and proximity to river inflows. The spatially-resolved mean OC burial rate was 44 g C m-2 yr-1, twice as high as the global average for natural lakes, but lower than the global average for reservoirs. Gas bubble-containing sediment was detected in 30% of the sub-bottom survey length and occurred along the whole reservoir, but was most abundant in areas of high primary productivity, high sediment accumulation rate, and < 25 m water column depth. Evidence from stable isotopes and lipid biomarkers indicates that a significant share of the OC accumulating in the reservoir sediment is of aquatic origin, and therefore is accountable as a new C sink that results from reservoir construction. These results indicate that the spatial variability of both the burial of OC from terrestrial and aquatic origin, and of gas bubble-rich sediments prone for CH4 ebullition can be understood from the reservoir characteristics.</p>

scholarly journals Alluvial response to the Paleocene–Eocene Thermal Maximum climatic event, Polecat Bench, Wyoming (U.S.A.)

2015 ◽  
Vol 435 ◽  
pp. 177-192 ◽  
Author(s):  
Mary J. Kraus ◽  
Daniel T. Woody ◽  
Jon J. Smith ◽  
Vanja Dukic
Keyword(s):  
Thermal Maximum ◽  
Climatic Event

scholarly journals Late Pleistocene-Holocene sedimentary fluxes of organic carbon and biogenic silica in the northwestern Ross Sea, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 697-703 ◽  
Author(s):  
M. Frignani ◽  
F. Giglio ◽  
L. Langone ◽  
M. Ravaioli ◽  
A. Mangini
Keyword(s):  
Late Pleistocene ◽  
Biogenic Silica ◽  
Ross Sea ◽  
Sediment Accumulation ◽  
Stratigraphic Correlation ◽  
Radiocarbon Dates ◽  
Marine Sedimentation ◽  
Core Logging ◽  
Bulk Organic Matter ◽  
Biogenic Components

Eight sediment gravity cores, collected from the joides and Drygalski basins, were analysed in order to understand late Pleistocene-Holocene biogenic flux changes in the Ross Sea, driven by paleoenvironmental changes. Core lithologies and magnetic-susceptibility depth profiles were used for core logging and stratigraphic correlation. Nineteen AMS radiocarbon dates of bulk organic matter were used to set chronological constraints and calculate sediment accumulation rates. These rates, which vary from 1.4-38 cm ka−1. were used to obtain the burial fluxes of biogenic components. The highest fluxes occur in the deepest parts of the basins (TOC, 0.05-0.2 g cm−2ka−1; biogenic silica, 1.5-5 g cm−1ka−1), where as topographic highs show the lowest values (TOC, 0.01-0.1 g cm−2ka−1; biogenic silica, 0.1-1.4 g cm−2ka−1). Dramatic changes in both physical properties and fluxes record the establishment of open marine-sedimentation conditions which occurred first in the joides basin and then, with a delay of ca. 6000 years, in the Drygalski basin. Both TOC and biogenic-silica fluxes increase through the Holocene, though slightly differently. The high fluxes of both10Be and biogenic Ba suggest that sediment accumulation at basin sites is strongly influenced by lateral transport.

scholarly journals Ecological assessment using diatom community in Avarga Toson Lake (Mongolia)

2021 ◽  
Vol 20 (1) ◽  
pp. 526-530
Author(s):  
Ts. Bukhchuluun
Keyword(s):  
Species Composition ◽  
Human Activities ◽  
Dominant Species ◽  
Sediment Accumulation ◽  
Ecological Assessment ◽  
Livestock Grazing ◽  
Diatom Species ◽  
Diatom Community ◽  
Diatom Communities ◽  
High Sediment

A total of 32 diatom species were recorded in Avarga Toson Lake. Motile diatom species are dominatingin diatom communities. The species composition of two coexisted lakes is markedly different. Diatom richness, speciescomposition, and dominant species indicate that Burd lake is polluted by livestock grazing or domestic pollution, andToson Lake is polluted by human activities with high sediment accumulation at the bottom.

Quaternary Tephrochronology and Deposition in the Subsurface Sacramento–San Joaquin Delta, California, U.S.A.

2015 ◽  
Vol 83 (2) ◽  
pp. 378-393 ◽  
Author(s):  
Katherine L. Maier ◽  
Emma Gatti ◽  
Elmira Wan ◽  
Daniel J. Ponti ◽  
Mark Pagenkopp ◽  
...  
Keyword(s):  
Hazard Assessment ◽  
Volcanic Eruption ◽  
Volcanic Ash ◽  
Sediment Accumulation ◽  
Middle Pleistocene ◽  
Accumulation Rates ◽  
Flood Events ◽  
Quaternary Deposits ◽  
Stratigraphic Framework ◽  
Age Constraints

We document characteristics of tephra, including facies and geochemistry, from 27 subsurface sites in the Sacramento–San Joaquin Delta, California, to obtain stratigraphic constraints in a complex setting. Analyzed tephra deposits correlate with: 1) an unnamed tephra from the Carlotta Formation near Ferndale, California, herein informally named the ash of Wildcat Grade (<~1.450 to >~ 0.780 Ma), 2) the Rockland ash bed (~ 0.575 Ma), 3) the Loleta ash bed (~ 0.390 Ma), and 4) middle Pleistocene volcanic ash deposits at Tulelake, California, and Pringle Falls, Bend, and Summer Lake, Oregon, herein informally named the dacitic ash of Hood (<~0.211 to >~ 0.180 Ma). All four tephra are derived from Cascades volcanic sources. The Rockland ash bed erupted from the southern Cascades and occurs in up to > 7-m-thick deposits in cores from ~ 40 m subsurface in the Sacramento–San Joaquin Delta. Tephra facies and tephra age constraints suggest rapid tephra deposition within fluvial channel and overbank settings, likely related to flood events shortly following volcanic eruption. Such rapidly deposited tephra are important chronostratigraphic markers that suggest varying sediment accumulation rates in Quaternary deposits below the modern Sacramento–San Joaquin Delta. This study provides the first steps in a subsurface Quaternary stratigraphic framework necessary for future hazard assessment.

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