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Marine Geology
Elsevier Science B.V.
Marine Geology

Elsevier Science B.V.

0025-3227

Marine Geology/Journal Marine GeologySCIISTPAHCIEI
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    Relationships between volcanism and plate tectonics: A case-study from the Canterbury Basin, New Zealand

    Barrier, A.Bischoff, A.Nicol, A.Browne, G. H....
    20页
    查看更多>>摘要：Buried volcanoes and igneous intrusions of Cretaceous to Pleistocene age are widespread in the Canterbury Basin, New Zealand. Interpretation of 2D and 3D seismic reflection lines correlated to petroleum exploration wells reveal over 185 buried volcanic systems formed in association with tectonic activity since the separation of Zealandia from Eastern Gondwana. We characterise these volcanoes according to their size, age and spatial distribution. Small-volume scattered monogenetic (<10 km(3)) and polygenetic vents (>10 km(3)) erupted during similar to 105-85, similar to 65-13 and similar to 5-1 Ma time intervals. In contrast, large polygenetic volcanic complexes (>100 km3 of erupted magma) formed from similar to 85-66 and similar to 13-5 Ma. Magmatic intrusions are widespread in the basin, where they are commonly emplaced into Cretaceous to Eocene sedimentary strata. The eruption rates within the offshore Canterbury Basin varied through time, reaching maximum values of similar to 58-127 km(3)/Myr immediately after the onset of Late Cretaceous Gondwana break-up (similar to 85-66 Ma) and in the Mid-Late Miocene (similar to 15-5 Ma). Late Cretaceous volcanism may reflect the far-field (>600 km) manifestation of volcanism along the Antarctica-Zealandia spreading centre. Vents and intrusions are located near Cretaceous rift faults which, in some cases act as conduits for magma to ascend to the surface.
      原文链接:
    • NSTL
    • Elsevier

    Regime shifts in the Changjiang (Yangtze River) Estuary: The role of concentrated benthic suspensions

    Lin, Jianliangvan Prooijen, Bram C.Guo, LeichengZhu, Chunyan...
    18页
    查看更多>>摘要：Channel deepening often triggers positive feedback between tidal deformation, sediment import and drag reduction, which leads to the regime shift in estuaries from low-turbid to hyper-turbid state. In this study, a transition in profiles of suspended sediment concentration (SSC) is hypothesised by including a positive feedback loop of vertical mixing and settling. Such a hypothesis is validated by the historical observations in the North Passage of Changjiang (Yangtze River) Estuary, with decreasing SSC in mid-lower layers and increasing SSC near the bed after the deepening. A mobile pool of concentrated benthic suspensions (CBS) develops in the North Passage, with a tidally averaged length of similar to 20 km and a mean thickness of similar to 4 m. The width of the CBS pool is limited (<1 km) as the CBS is concentrated in the Deepwater Navigational Channel. The movements of the CBS pool, combined with tidal asymmetry (e.g., slack-water asymmetry and lateral flow asymmetry), results in sediment trapping in the middle reaches and on the south flank of the channel. Observations by a bottom tripod system show the response of friction/drag coefficient to sediment concentration: (1) nearly linear decrease within low SSC (<10 kg/m(3)); (2) constant and minimum coefficient (with drag reduction up to 60-80%) in the presence of CBS (10-80 kg/m(3)). An empirical relationship was derived, which can be used to predict the friction coefficient and the magnitude of drag reduction for sediment transport studies, particularly for modelling regime shifts in estuaries.
      原文链接:
    • NSTL
    • Elsevier

    Coastal chalk cliff retreat rates during the Holocene, inferred from submarine platform morphology and cosmogenic exposure along the Normandy coast (NW France)

    Duguet, TimotheeDuperret, AnneCosta, StephaneRegard, Vincent...
    23页
    查看更多>>摘要：Submerged marine terraces potentially provide crucial information on past sea-level variations and paleo-coastline locations that may be used to estimate long-term coastal erosion rates. The Normandy coastline has recently been surveyed using a shallow water high-resolution mapping system. We identified a new continuous submarine platform, called the inner platform, limited by a shore parallel edge located between -9 m and -10 m (NGF) along the Normandy chalk coastline. A lower rock platform, called the outer platform, ranging from about -14 m to -17 m (NGF) appears locally. This corresponds to inherited preserved submarine terraces created during a past sea level highstand. The high cosmogenic Be-10 concentration measured at the end of Mesnil-Val inner shore platform (including intertidal and subtidal shore platforms) is attributed to the last glacial cliff location at 6.5 ky +/- 1 ky. From the spatial edge location of the inner platform in Normandy, we estimated cliff retreat rates since 6.5 ky +/- 1 ky ranging from 0.051 +/- 0.008 m/y to 0.090 +/- 0.014 m/y from place to place. Comparisons with the current coastal chalk cliffs indicate a mean retreat rate estimated over the contemporary period suggesting such long-term retreat rates are 33% to 57% lower than the contemporary ones (0.10 m/y to 0.18 m/y). This confirms a contemporary acceleration of chalk cliff system retreat rates.
      原文链接:
    • NSTL
    • Elsevier

    Latest Pleistocene to Holocene stratigraphic record and evolution of the Paleo-Mekong incised valley, Vietnam

    Thi Kim Oanh TaVan Lap NguyenSaito, YoshikiGugliotta, Marcello...
    16页
    查看更多>>摘要：Recent 200+ km progradation of the Mekong River delta over the last 6000 years has provided a sequence of incised-valley fills with insights into the sedimentary response of a large river system to sea-level changes since the Last Glacial Maximum (LGM). This study provides an analysis of comprehensive synthesis of the incised-valley and successive progradational deposits of the paleo-Mekong River across a regional area spanning from the Cambodian lowland to the Vietnamese shelf. The study is based on the analysis of the depositional facies, diatom and foraminiferal assemblages, and radiocarbon ages of three new cores and previously published cores. The depositional succession observed in these cores is divided into the lower and upper units representing Pleistocene weathered sediment and incised valley fills and delta sediment since the LGM, respectively. The upper unit shows an upward-deepening succession from the fluvial channel to estuary and subtidal deposits, followed by an upward-shallowing succession consisting of progradational deltaic deposits. This unit can be divided into four phases: the fluvial channel sedimentation (before similar to 13.4 ka); retrogradational and aggradational estuarine system (similar to 13 to ca. 8 ka), aggradational and progradational delta system (ca. 8 to 6 ka), progradational delta system (6 ka to present). Tides were dominant from 13 to similar to 3.5 ka, followed by wave- and tide-dominated environments until present at its river-mouth and coast.
      原文链接:
    • NSTL
    • Elsevier

    A chronology of post-glacial mass-transport deposits on the Canadian Beaufort Slope

    Riedel, M.King, E. L.Cameron, G. D. M.Blasco, S....
    18页
    查看更多>>摘要：Extent and chronology of 24 buried and seabed-exposed mass transport deposits (MTDs) on the continental slope of the Canadian Beaufort Sea were compiled towards a regional geo-hazard assessment of the Beaufort region. A total of 2220 lines of 3.5 kHz sub-bottom profiler (SBP) data (similar to 40,000-line kilometres) covering an area of 9740 km(2) were analyzed to allow a new understanding of slope instability in the region. Several sediment cores acquired across the region allow dating of the sediment cover. A regionally representative seismic-stratigraphy (type section, ca. 60 m thick) of the stratified sediments mantling the slope was defined. The MTDs all occur above a marked change in sedimentation style from a deeper-situated slope fan that varies substantially laterally to the above-lying stratified layers that host the MTDs. The type section comprises three sedimentary units bound by two prominent markers. Relative ages for the MTDs were defined by measuring the thickness of sediments overlying each MTD and linking that sediment package to the type section. Two 3-D seismic data volumes across the study region verified interpretations from 2D data by imaging internal deposit character and down-slope continuity of the MTDs. Seismic amplitude and similarity attributes enabled identification of further MTD events, incompletely imaged by the SBP data. A composite chronostratigraphy based on C-14 dating of foraminifera and shells was assembled despite the fact that the type section is far thicker than sediment coring limits. Sub-unit thickness varies up- and down-slope such that a selection of cores across the study region enabled its compilation. The marked change in sedimentation style at the base of the type section required substantial extrapolation to date. Simple (quadratic function) age models project that the base of the type section signals the end of the last glacial maximum (Wisconsinan, or marine isotope stage 2 glaciation) and initiation of pro-glacial plume sedimentation (the deglacial), and finally post-glacial (marine) ultimately from the Mackenzie River. The MTD abundance above this contact defines an average theoretical recurrence rate of one MTD per similar to 1000 yrs.; however, MTDs are clustered temporally with the highest number of events occurring just prior to the onset of the Younger Dryas at around 13 ka BP (cal.).
      原文链接:
    • NSTL
    • Elsevier

    Stratigraphic framework and sediment wave fields associated with canyon-levee systems in the Huatung Basin offshore Taiwan Orogen

    Hsu, Ho-HanLiu, Char-ShineChen, Tzu-TingHung, Hau-Ting...
    16页
    查看更多>>摘要：Newly compiled bathymetry, sub-bottom profiling and seismic data are used to illustrate seafloor morphology, submarine canyon networks and stratigraphic framework in Huatung Basin (HB) and an adjacent sub-basin, named as East Luzon Arc Basin offshore east Taiwan. Based on seismic facies characteristics and isopach maps, three major stratigraphic sequences are recognized and we suggest that they could be resulted from pre- and syn-Taiwan arc-continent collision. Based on the sediment thickness and sedimentation rates, ages of the HB strata could be estimated. Pelagic sediments formed the lower HB sequence which follows the HB basement reliefs since 50-102 Ma. Then, the initiation of Taiwan orogen and Luzon Arc volcanic activities changed the deposition pattern after 5 Ma, and mass transport deposits developed in middle HB sequence. After rapid uplift of the Taiwan mountain belt since about 1.5 Ma, complex canyon-levee systems and thick strata formed the upper sequence in the northern HB. In contrast, sediment thickness is thin and no submarine canyon developed in southern HB. The seafloor in South Huatung Basin is flat, except in its eastern part where couple basement ridges appeared. In North Huatung Basin, canyon-levee complex and sediment waves are the most distinct morphological features in the drainages of two submarine canyons. We propose a three-stage process for sediment wave development: (1) sediment gravity flow can initiate a base of sediment wave; (2) wavy geometry begins to develop; (3) sediment waves continuously aggrade due to overbank sediments in the canyon-levee system. This study presents the evolution of sedimentary processes in a deep-sea basin and how the deposition patterns were affected by the convergent tectonics.
      原文链接:
    • NSTL
    • Elsevier

    Sedimentary evolution of a delta-margin mangrove in Can Gio, northeastern Mekong River delta, Vietnam

    Collins, D. S.Nguyen, V. L.Ta, T. K. O.Mao, L....
    16页
    查看更多>>摘要：Mangroves can deliver important socio-economic benefits and store significant volumes of carbon along tropical to temperate coastlines, but the distribution is controlled by complex geomorphologic, hydrodynamic and salinity conditions, as well as human-related pressures. In the Mekong delta, the interaction of tide, wave and riverine hydrodynamic processes clearly impacts sedimentation and mangrove distribution. Extensive mangroves presently occur along the northeastern delta margin (Can Gio, located 40 km southeast of Ho Chi Minh City), in an embayed, back-barrier environment subject to the highest tidal range (c. 4 m) and away from major fluvial distributary channels. However, the development of the Can Gio mangrove system during the Holocene evolution of the Mekong delta is not fully understood. This study aims to constrain the sedimentary evolution of the back-barrier mangrove in Can Gio based on stratigraphic, palynological and geochronological analyses of sediment cores. Two deep borehole cores (15 and 30 m deep) and four short auger cores (up to 4 m deep) were taken at the modern mangrove to characterize a 20-km-long shore-normal cross section dated with radiocarbon and optically-stimulated luminescence (OSL) ages. The cores consist of a thick (> 20 m) subtidal mud from the base of the Holocene unit to the level of 3-4 m deep below the ground level, overlain by carbonaceous, intertidal mud. Chronological data reveal major episode of subtidal mud aggradation from 6 to 3.5 ka, forming the topography for mangrove development. Radiocarbon ages in the overlying intertidal mud range from 4 ka to modern and show some inconsistencies with the stratigraphy, suggesting mangrove root penetration and sediment mixing. The beach-ridge structure and OSL ages of the Can Gio barrier indicate that barrier formation initiated just before 3.2 ka. The transition from subtidal to intertidal mud aggradation and initiation of barrier formation, are broadly correlated with the onset of the subaqueous delta progradation and shift to a wave-dominated regime in the central delta. However, after 3.5 ka, the Can Gio shoreline had negligible sediment accretion while the central delta prograded up to 50 km seawards. Reduced sediment supply to Can Gio is consistent with more asymmetric, southwestward-dominated longshore drift after 3.5 ka. The negligible progradation at Can Gio also indicates minor sediment supply from the nearby Dong Nai River, which prevented upper intertidal accretion and translation of mangroves into a flood plain.
      原文链接:
    • NSTL
    • Elsevier

    Extreme floods of the Changjiang River over the past two millennia: Contributions of climate change and human activity

    Guo, YongqiangShi, BenweiGao, ShuZhou, Liang...
    16页
    查看更多>>摘要：Climate change and human activity have exerted significant influences on the sediment load and channel morphology of the Changjiang River system, China. However, our knowledge of their influence on flood regime on the centennial to millennial timescales remains limited, and this is mainly because of the difficulty in directly determining the long-term hydrological variability of the Changjiang River over the period before hydrological gauges were established. Based on multiproxy analysis that combines chronological, sedimentological, and geochemical analysis of a 4.8-m-long sediment core retrieved from the subaqueous delta of the Changjiang River, this study establishes a flood history for the Changjiang River during the late Holocene. Our palaeoflood reconstruction revealed 14 multi-decadal periods of extreme floods (19-66 BCE, 25-80, 255-350, 415-475, 550-710, 740-835, 970-990, 1080-1130, 1170-1235, 1275-1390, 1440-1500, 1560-1730, 1810-1830, and 1950-2011 CE). These flood units match well with the observed large floods, documentary records of floods, and sedimentary flood deposits, confirming that the coarse units in the sequence are flood-derived and are regionally representative. Comparing with regional and global palaeoclimate records indicates that major flood events of the Changjiang are strongly modulated by the Asian summer monsoon and the El Nino-Southern Oscillation (ENSO), but that anthropogenic impacts (e.g. artificial channelization and land clearance) have also greatly amplified the flooding frequency over the past 600 yr.
      原文链接:
    • NSTL
    • Elsevier

    Fault-controlled contourite drifts in the southern South China Sea: Tectonic, oceanographic, and conceptual implications

    Javier Hernandez-Molina, F.Lei, ZhenyuDuarte, DeboraChen, Hui...
    14页
    查看更多>>摘要：Over the past decades, contourite drifts have been widely identified in the deep ocean with their classification constantly being improved. Some contourite drift types, however, are not yet well constrained. The present study investigates contourite drifts in the southern South China Sea for the first time based on high-resolution reflection seismic profiles and bathymetric data, thereby determining the common occurrence of a lesser-known type: the fault-controlled drift. In this area, normal fault movements have been active during the Quaternary, associated with the formation of sea-floor irregularities and highs that represented obstacles to Deep Water circulation. Six fault-controlled drifts are generated in the study area due to interactions between regional faulting/fault-generated topography and bottom currents. They are divided into two major types depending on their shapes, locations, and relative faulting movements: Type-1) drifts deposited coeval to the fault movement and are situated over the footwall block top or along the fault scarp, and Type-2) drifts deposited after the fault movement and are located along the fault scarp base. Spatial distribution of these drifts is a result of variations on bottom currents dynamics associated with the South China Sea Deep Water. The South China Sea Deep Water settling depth, 200-300 m shallower than that of the northern South China Sea, tentatively indicates upwelling which may have, in turn, contributed to the South China Sea meridional overturning circulation. The present study demonstrates new types of contourite drifts that are not well-constrained in the literature and require more detailed studies. The types of fault-controlled drift are described based on the relative movement of normal faults. However, future research should be conducted in other active tectonic settings for evaluating fault effects on the sedimentary stacking patterns, geometries, and evolution of contourite drifts.
      原文链接:
    • NSTL
    • Elsevier