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Colin D Woodroffe - One of the best experts on this subject based on the ideXlab platform.
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punctuated Progradation of the seven mile beach holocene barrier system southeastern tasmania
Marine Geology, 2017Co-Authors: Thomas S N Oliver, Paul Donaldson, C Sharples, Michael Roach, Colin D WoodroffeAbstract:Abstract Prograded barriers are depositional coastal landforms which preserve past shoreline locations and have been studied in order to understand the fundamental drivers of barrier formation. This paper reconstructs the Holocene history of the Seven Mile Beach, prograded barrier in Tasmania, Australia using optically stimulated luminescence (OSL) dating, ground penetrating radar (GPR), light detection and ranging (LiDAR) elevation models and sedimentological analyses. Shoreline Progradation of the barrier commenced around 7300 years ago and continued to near present despite a ~ 3000 pause in deposition between 6700 and 3600 years ago indicative of substantial changes in sediment availability. GPR imaged subsurface structures contain a record of seaward dipping reflectors preserved as sediment supplied beaches and dunes leading to shoreline Progradation. In the past 500 years a large transgressive dune has formed, built from reworked barrier sands, and now dominates the eastern portion of the barrier implying that shoreline Progradation has ceased. This study reaffirms the notion that relict foredune ridges are strongly aligned with modal wave refraction patterns in planform and emphasises the importance of sediment delivery as a key driver of shoreline Progradation through beachface and dune accretion. The substantial pause in shoreline Progradation on this barrier system, as observed on others around the world, requires further explanation. Although changes in sediment delivery have been inferred, it may also be appropriate to reopen the debate on Holocene sea-level change in Tasmania.
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holocene emergence and evolution of the mcarthur river delta southwestern gulf of carpentaria australia
Sedimentary Geology, 1993Co-Authors: Colin D Woodroffe, John ChappellAbstract:Abstract The McArthur River drains from a semiarid, sandstone catchment into a shallow embayment behind the Sir Edward Pellew Group of islands in the southwestern Gulf of Carpentaria. It has built a broad Holocene delta, presently with two active distributaries and several abandoned, mangrove-lined, former distributaries. Augering indicates that much of the delta is underlain by shelly sands which contain distinct shell beds in their position of growth. These are interpreted as delta front deposits, and the elevation of the landwardmost beds above high tide level implies emergence of 1–2 m over the last 4000 years. This relative sea-level fall appears to have been a major cause of rapid mid-Holocene delta Progradation. The eastern margin of the delta has undergone little net Progradation over the last 2000 years, though there has been accretion of small mangrove-covered islands to the northwest of the delta. Distributaries have migrated across the upper deltaic plain by lateral migration, leaving nested sequences of fluvial ridges. In the lower deltaic plain, channel migration appears to have occurred mainly by avulsion; former distributaries have been infilled with fluvial sands and are now tidally dominated.
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estuarine infill and coastal Progradation southern van diemen gulf northern australia
Sedimentary Geology, 1993Co-Authors: Colin D Woodroffe, Monica E Mulrennan, John ChappellAbstract:Abstract There are several estuaries associated with the pronouncedly seasonal rivers which drain northwards from the Middle Proterozoic sandstone Arnhem Land plateau, and the Tertiary Koolpinyah land surface, into the macrotidal van Diemen Gulf, in the Northern Territory of Australia. The Holocene development of these, investigated in greatest detail for the South Alligator River with an upland catchment of > 10,000 km2. through drilling, palynology and radiocarbon dating, comprises both estuarine infill and coastal Progradation. Three phases of estuarine infill can be recognised: (i) a transgressive phase (8000-6800 years B.P.) of marine incursion; (ii) a big swamp phase (6800-5300 years B.P.) of widespread mangrove forest development; and (iii) a sinuous/cuspate phase of floodplain development since 5300 years B.P., during which the tidal river has meandered and reworked earlier estuarine sediments. Since 6000 years B.P., the South Alligator coastal plain has prograded at a decelerating rate, with two phases of chenier ridge formation. A similar pattern of estuarine infill, and decelerating coastal plain Progradation, is demonstrated for the Adelaide and Mary Rivers, both with catchments of > 6000 km2. The southern shore of van Diemem Gulf appears to have changed its overall position little during the last 2000 years. The major source for the clay, silt and fine sands which have infilled the estuary and coastal plain has been from seaward. Dispite the similarity of development, coastal sediment build up has had different effects on the morphology of each tidal river. The Adelaide has undergone a major diversion and no longer flows directly into van Diemen Gulf, but occupies a former fluvial course, and the Mary has been blocked entirely, and its former estuarine palaeochannels have been infilled with tide-transported sediment.
Marcus Wunsch - One of the best experts on this subject based on the ideXlab platform.
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High-resolution stratigraphic forward modeling of a Quaternary carbonate margin: Controls and dynamic of the Progradation
Sedimentary Geology, 2019Co-Authors: Jean Busson, Philippe Joseph, Vanessa Teles, Jean Borgomano, Didier Granjeon, Christian Betzler, E Poli, Thierry Mulder, Marcus WunschAbstract:The relationships between the margin sedimentary regime and the platform Progradation are studied using forward stratigraphic numerical simulations on the Leeward (Western) prograding margin of the Great Bahama Bank (GBB) during the Quaternary (1.7–0 Ma). The corresponding sedimentary regime in the slope and the platform is well known from the ODP leg 166 and Bahamas Drilling Project wells located along the “Western line” seismic transect. However the sedimentary regime on the margin is not well established: the coral reefal margin observed before between 1.7 and 0.8 Ma in the well Clino is not active anymore at present-day, and the Holocene sedimentary regime is geometrically unable to account alone for the Progradation. This study is based on three 2D high-resolution forward stratigraphic numerical modeling experiments with the software DionisosFlow that include the platform, margin and slope domains on the “Western Line Section” in the same sedimentary models. The results are compared to the six sedimentary cores and to the present day bathymetry in order to identify the more realistic scenario. The three experiments test different models of carbonate sediment production and transport. Experiment 1 shows that the highstand shedding of the fine-grained uncemented platform production is unable to reproduce the Progradation and the present-day profile. Experiments 2 and 3 incorporate cemented facies in the margin, with the best results obtained with the cemented marginal wedges produced in Experiment 2 during platform emersion. From these results a high-resolution interpretation of the margin seismic section is proposed. This study shows that the platform Progradation can be decoupled from the highstand shedding of the fine-grained platform production. It is dependent on the accumulation in front of the steep margin of coarse or cemented material. Before 0.8 Ma this corresponds to the coral reef identified in Clino. The transition after 0.45 Ma to 100-kyr large eustatic cycles with total platform flooding created two distinct marginal regimes: (1) during platform flooding aggrading accumulation of non-skeletal sands, and (2) during platform emersion prograding cemented marginal wedges produced in-situ.
M Van De Broek - One of the best experts on this subject based on the ideXlab platform.
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soil organic carbon stocks in a tidal marsh landscape are dominated by human marsh embankment and subsequent marsh Progradation
European Journal of Soil Science, 2019Co-Authors: M Van De Broek, L Baert, Stijn Temmerman, Gerard GoversAbstract:Tidal marshes are coastal and estuarine ecosystems that store large amounts of sedimentary organic carbon (OC). Despite the valuable ecosystem services they deliver, tidal marshes have been converted to other land‐use types over the past centuries. Although previous studies have reported large decreases in soil organic carbon (SOC) stocks after tidal marsh embankment, knowledge on the magnitude and rate of OC losses is still limited. Here, we studied the effect of stepwise embankments of brackish and salt marshes and subsequent marsh Progradation on SOC stocks in the Scheldt estuary (the Netherlands). We collected samples from soil profiles along tidal marsh–reclaimed tidal marsh chronosequences and determined total OC stocks and the stable carbon signature of the OC. Our results showed that large losses of previously sequestered SOC occur on a decadal timescale with the embankment of brackish (−8.7 ± 0.7 kg OC m⁻²) and salt marshes (−6.7 ± 0.8 kg OC m⁻²). The (incomplete) replacement of tidal marsh OC by agricultural OC is substantially faster in topsoils (ca. a century) compared with subsoils (multiple centuries). Simulations with a coupled land use–SOC model showed that large rates of marsh Progradation following embankment construction resulted in a substantial increase in landscape‐scale SOC storage, whereas large SOC losses occurred in landscapes dominated by embanked tidal marshes. The findings of our study might help to assess how these management practices affect regional SOC stocks. HIGHLIGHTS: We studied how OC stocks in tidal marsh sediments are affected by embankment construction OC stocks of both brackish and salt marsh sediments were reduced by ca. 60% with embankment Gains in landscape‐scale SOC storage occurred with marsh Progradation after embankment If no marsh Progradation occurs, embankments always lead to SOC loss at the landscape scale
Douglas W Burbank - One of the best experts on this subject based on the ideXlab platform.
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chronology and tectonic controls of late tertiary deposition in the southwestern tian shan foreland nw china
Basin Research, 2007Co-Authors: Richard V Heermance, Douglas W Burbank, Jie Chen, Changsheng WangAbstract:Magnetostratigraphy from the Kashi foreland basin along the southern margin of the Tian Shan in Western China defines the chronology of both sedimentation and the structural evolution of this collisional mountain belt. Eleven magnetostratigraphic sections representing 13 km of basin strata provide a two- and three-dimensional record of continuous deposition since 18Ma. The distinctive Xiyu conglomerate makes up the uppermost strata in eight of 11 magnetostratigraphic sections within the foreland and forms a wedge that thins southward. The basal age of the conglomerate varies from 15.5 0.5Ma at the northernmost part of the foreland, to 8.6 0.1Ma in the central (medial) part of the foreland and to 1.9 0.2, 1.04 and 0.7 0.1Ma along the southern deformation front of the foreland basin. These data indicate the Xiyu conglomerate is highly time-transgressive and has prograded south since just after the initial uplift of the Kashi Basin Thrust (KBT) at 18.9 3.3Ma. Southward Progradation occurred at an average rate of 3mm year 1 between 15.5 and 2Ma, before accelerating to 10mm year 1. Abrupt changes in sediment accumulation rates are observed at 16.3 and 13.5Ma in the northern part of the foreland and are interpreted to correspond to southward stepping deformation. A subtle decrease in the sedimentation rate above the Keketamu anticline is determined at 4.0Ma and was synchronous with an increase in sedimentation rate further south above the Atushi Anticline. Magnetostratigraphy also dates growth strata at <4.0, 1.4 0.1 and 1.4 0.2Ma on the southern flanks the Keketamu, Atushi and Kashi anticlines, respectively. Together, sedimentation rate changes and growth strata indicate stepped migration of deformation into the Kashi foreland at least at 16.3, 13.5, 4.0 and 1.4Ma. Progressive reconstruction of a seismically controlled cross- section through the foreland produces total shortening of 13-21km and migration of the deformation front at 2.1-3.4 mmyear 1 between 19 and 13.5Ma, 1.4-1.6mmyear1 between 13.5 and 4.0Ma and 10mm year 1 since 4.0Ma. Migration of deformation into the foreland generally causes (1) uplift and reworking of basin-capping conglomerate, (2) a local decrease of accommodation space above any active structure where uplift occurs, and hence a decrease in sedimentation rate and (3) an increase in accumulation on the margins of the structure due to increased subsidence and/or ponding of sediment behind the growing folds. Since 5-6 Ma, increased sediment-accumulation (0.8mm year -1) and gravel Progradation (10mm year-1) rates appear linked to higher deformation rates on theKeketamu, Atushi and Kashi anticlines and increased subsidence due to loading fromboth the Tian Shan and Pamir ranges, and possibly a change in climate causing accelerated erosion. Whereas the rapid (10mmyear1) Progradation of the Xiyu conglomerate after 4.0Ma may be promoted by global climate change, its overall Progradation since 15.5Ma is due to the progressive encroachment of deformation into the foreland.
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dynamic fluvial systems and gravel Progradation in the himalayan foreland
Geological Society of America Bulletin, 2000Co-Authors: Nicholas Brozovic, Douglas W BurbankAbstract:Although the large-scale stratigraphy of many terrestrial foreland basins is punctuated by major episodes of gravel Progradation, the relationships of such facies to hinterland tectonism and climate change are often unclear. Structural reentrants provide windows into older and more proximal parts of the foreland than are usually exposed, and thus provide key insights to earlier phases of foreland evolution. Our magnetostratigraphic studies show that, although the major lithofacies preserved within the Himachal Pradesh structural reentrant in northwestern India resemble Neogene facies in Pakistan, they have a much greater temporal and spatial variability. From 11.5 to 7 Ma, major facies boundaries in Himachal Pradesh vary by as much as 2–3 m.y. across distances of 20–30 km and are controlled by the interference between a major southeastward-flowing axial river and a major southwestward-flowing transverse river. A thick but highly confined middle to late Miocene conglomerate facies includes the oldest extensive Siwalik conglomerates yet dated (10 Ma) and implies the development of significant erosional topography along the Main Boundary thrust prior to 11 Ma. Our studies document extensive syntectonic gravel Progradation with conglomerates extending tens of kilometers into the undeformed foreland during a period of increased subsidence rate and within 1–2 m.y. of major thrust initiation. Overall, gravel Progradation is modulated by the interplay among subsidence, sediment supply, and the proportion of gravels in rivers entering the foreland.
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models of aggradation versus Progradation in the himalayan foreland
International Journal of Earth Sciences, 1991Co-Authors: Douglas W Burbank, Richard A BeckAbstract:A frequent goal of decompaction analysis is to reconstruct histories of basin subsidence and tectonic loading. In marine environments, eustatic and paleobathymetric uncertainties limit the resolution of these reconstructions. Whereas in the terrestrial basins, these ambiguities are absent, it is still necessary to account for depositional slopes between localities in order to analyze three-dimensional patterns of subsidence. We define two end-members for depositional surfaces: aggradation and Progradation. The relative importance of either end-member is a function of the interplay between the rate of net sediment accumulation and the rate of basin subsidence. The models predict the patterns of major drainages (transverse versus longitudinal) and the way in which provenance should be reflected within different portions of a basin. Consequently, paleocurrent and provenance data from the ancient stratigraphic record can be used to distinguish between these endmembers. The subhorizontal depositional surfaces that dominate during times of aggradation provide a well defined reference frame for regional analysis of decompacted stratigraphies and related subsidence. Depositional slopes during Progradation can not be as precisely specified, and consequently yield greater uncertainties in reconstructions of subsidence. These models are applied to the Mio-Pliocene foreland basin of the northwestern Himalaya, where sequences of isochronous strata have been analyzed throughout the basin. These time-controlled data delineate a distinctive evolution from largely aggradational to largely Progradational depositional geometries as deformation progressively encroaches on the foreland. Such a reconstruction of past depositional surfaces provides a well constrained reference frame for subsequent integration of subsidence histories from throughout the foreland.
Yoshiki Saito - One of the best experts on this subject based on the ideXlab platform.
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holocene delta evolution and sediment discharge of the mekong river southern vietnam
Quaternary Science Reviews, 2002Co-Authors: Van Lap Nguyen, Masaaki Tateishi, Iwao Kobayashi, Susumu Tanabe, Yoshiki SaitoAbstract:Abstract Evolutionary changes, delta Progradation, and sediment discharge of the Mekong River Delta, southern Vietnam, during the late Holocene are presented based on detailed analyses of samples from six boreholes on the lower delta plain. Sedimentological and chronostratigraphic analyses indicate clearly that the last 3 kyr were characterized by delta Progradation under increasing wave influence, southeastward sediment dispersal, decreasing Progradation rates, beach-ridge formation, and steepening of the face of the delta front. Estimated sediment discharge of the Mekong River for the last 3 kyr, based on sediment-volume analysis, was 144±36 million t yr −1 on average, or almost the same as the present level. The constant rate of delta front migration and stable sediment discharge during the last 3 kyr indicate that a dramatic increase in sediment discharge owing to human activities, as has been suggested for the Yellow River watershed, did not occur. Although Southeast Asian rivers have been considered candidates for such dramatic increases in discharge during the last 2 kyr, the Mekong River example, although it is a typical, large river of this region, does not support this hypothesis. Therefore, estimates of the millennial-scale global pristine sediment flux to the oceans must be revised.
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sedimentary facies and holocene Progradation rates of the changjiang yangtze delta china
Geomorphology, 2001Co-Authors: Kazuaki Hori, Yoshiki Saito, Yoshio Sato, Quanhong Zhao, Pinxian Wang, Xinrong Cheng, Congxian LiAbstract:Abstract The Changjiang (Yangtze) River, one of the largest rivers in the world, has formed a broad tide-dominated delta at its mouth during the Holocene sea-level highstand. Three boreholes (CM97, JS98, and HQ98) were obtained from the Changjiang delta plain in 1997–1998 to clarify the characteristics of tide-dominated delta sediments and architecture. Based on sediment composition and texture, and faunal content, core sediments were divided into six depositional units. In ascending order, they were interpreted as tidal sand ridge, prodelta, delta-front, subtidal to lower intertidal flat, upper intertidal flat, and surface soil deposits. The deltaic sequence from the prodelta deposits to the delta front deposits showed an upward-coarsening succession, overlain by an upward-fining succession from the uppermost part of the delta front deposits to the surface soil. Thinly interlaminated to thinly interbedded sand and mud (sand–mud couplets), and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of Changjiang deltaic facies. Sediment facies and their succession combined with AMS 14C dating revealed that isochron lines cross unit boundaries clearly, and delta Progradation has occurred since about 6000 to 7000 years BP, when the rising sea level neared or reached its present position. The average Progradation rate of the delta front was approximately 50 km/kyear over the last 5000 years. The Progradation rate, however, increased abruptly ca. 2000 years BP, going from 38 to 80 km/kyear. The possible causes for this active Progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and/or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid-Holocene.
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Progradation of the changjiang river delta since the mid holocene
Science China-chemistry, 2001Co-Authors: Kazuaki Hori, Yoshiki Saito, Quanhong Zhao, Pinxian WangAbstract:Subaqueous deltaic deposits with approximately 30 radiocarbon ages show that the Changjiang River delta was strongly affected by tides and that the delta Progradation rate after 2 kaBP was almost double the rate before 2 kaBP. This change in the Progradation rate correlates well with the active extension of the subaerial delta plain shown by previous work. Widespread human activities, such as farming, deforestation, and dike construction, probably resulted in an increase in sediment discharge to the river-mouth area.
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delta Progradation and chenier formation in the huanghe yellow river delta china
Journal of Asian Earth Sciences, 2000Co-Authors: Yoshiki Saito, Helong Wei, Yongqing Zhou, Akira Nishimura, Yoshio Sato, Setsuya YokotaAbstract:Abstract To clarify Holocene development of the Huanghe (Yellow River) delta and the relationship between delta Progradation and chenier formation, detailed sediment analyses and high-resolution radiocarbon dating were done on borehole samples taken from two sites on the present Huanghe; H9601 (Latitude 37°40.5′N and Longitude 118°28.7′E with an altitude of +5.5 m) and H9602 (Lat. 37°47.8′N and Long. 118°54.3′E, +4.8 m). Downcore changes of sediment facies and accumulation rate show that delta Progradation occurred at least twice during ca 2.6–1.2 C-14 yrBP and 1855–present at the two borehole sites. These phases of Progradation correlate with Superlobes 6 and 7 and Superlobe 10 respectively, of ten superlobes composing the Holocene Huanghe Delta shown by C. Xue (Historical changes in the Yellow River delta, China, Marine Geology 113, 321–329, 1993). The boundary of these sediments at H9602 is sharp and erosional, and correlates with cheniers located between borehole sites on the delta plain. The diastem period between these phases of Progradation almost coincides with the periods when the river mouth of the Huanghe was located in the northwestern part of the Bohai Sea during 1048–1128 AD (Superlobe 8), and the Jiangsu region facing the Yellow Sea during 1128–1855 (Superlobe 9). This suggests that chenier formation and delta Progradation are linked, and controlled by sediment supply and river course shifts of the lower reaches of the Huanghe.
