Through densified surface sampling of foraminifera and accurate elevation measurement a-long three transect lines in open-coast tidal salt-marsh of Jianchuan, particular salt-marsh foraminifera assemblages were found....Through densified surface sampling of foraminifera and accurate elevation measurement a-long three transect lines in open-coast tidal salt-marsh of Jianchuan, particular salt-marsh foraminifera assemblages were found. The salt-marsh foraminifera assemblages are distributed in well-defined vertical zonations with respect to elevation and closely parallel marsh floral zonations. At the top of the vertical zonation all foraminifera disappear abruptly which are accurately located at the highest high water datum. This distribution pattern can be used to relocate former sea levels accurately (to an accuracy of within ±5 cm). A modern regional criterion of foraminifera for relocating the former sea levels in high resolution in our country is provided, and deficiencies of studying the vertical zonation only in sheltered coast salt-marsh abroad are filled up.展开更多
Significant progress has been achieved in the research of tide-dominated environments in the past two decades. These studies highlight both the importance and diversity of tidal flats in modern coastal environments. B...Significant progress has been achieved in the research of tide-dominated environments in the past two decades. These studies highlight both the importance and diversity of tidal flats in modern coastal environments. Based on their developing settings, tidal flats are subdivided into nine types, which are in turn grouped into sheltered or exposed spectrums according to the magnitude of exposure to waves. The ternary coastal classification model is revised with an embedded triangle to highlight non-open coast tidal flats as major second-order morphological elements to the first-order coastal environments including deltas, estuaries and lagoons. A new continuous spectrum of open coast depositional settings is proposed from muddy tidal flats of tide dominance with wave influence, through sandy tidal flats of mixed energy (tide-dominated), and tidal beaches of mixed energy (wave-dominated), to beaches of wave-dominance with tide influence. It is worth noting that no open coast setting is absolutely exempt from wave or tide influence. Three diagnostic criteria for the intertidal-flat deposits are proposed. Upon an upward-fining succession, (1) regular changes vertically from flaser bed-ding, through wavy bedding and to lenticular bedding are diagnostic of most of intertidal flats; (2) cyclical tidal rhythmites point to sheltered intertidal flats typically at the inner part of macrot-idal estuaries; (3) rhythmic alternations of storm and tidal deposition are diagnostic of exposed intertidal flats, especially the open coast types. Intertidal-flat deposits are generally topped by saltmarsh deposits, but underlain by different subtidal successions, like thick subtidal channel-fills, sand-bar complexes (sheltered coastal settings), and upwards coarsening successions of subtidal flats or thick subtidal sand ridge/bar complexes (exposed coastal environments).展开更多
基金This study was supported by the National Natural Science Foundation of China under contract No. 49671071.
文摘Through densified surface sampling of foraminifera and accurate elevation measurement a-long three transect lines in open-coast tidal salt-marsh of Jianchuan, particular salt-marsh foraminifera assemblages were found. The salt-marsh foraminifera assemblages are distributed in well-defined vertical zonations with respect to elevation and closely parallel marsh floral zonations. At the top of the vertical zonation all foraminifera disappear abruptly which are accurately located at the highest high water datum. This distribution pattern can be used to relocate former sea levels accurately (to an accuracy of within ±5 cm). A modern regional criterion of foraminifera for relocating the former sea levels in high resolution in our country is provided, and deficiencies of studying the vertical zonation only in sheltered coast salt-marsh abroad are filled up.
基金funded by the National Natural Science Foundation of China (Grant No.41076016,41276045)Program for New Century Excellent Talents in University (Grant No.NCET-07-0619)+1 种基金State Key Laboratory of Marine Geology (MG200907)the Fundamental Research Funds for the Central University
文摘Significant progress has been achieved in the research of tide-dominated environments in the past two decades. These studies highlight both the importance and diversity of tidal flats in modern coastal environments. Based on their developing settings, tidal flats are subdivided into nine types, which are in turn grouped into sheltered or exposed spectrums according to the magnitude of exposure to waves. The ternary coastal classification model is revised with an embedded triangle to highlight non-open coast tidal flats as major second-order morphological elements to the first-order coastal environments including deltas, estuaries and lagoons. A new continuous spectrum of open coast depositional settings is proposed from muddy tidal flats of tide dominance with wave influence, through sandy tidal flats of mixed energy (tide-dominated), and tidal beaches of mixed energy (wave-dominated), to beaches of wave-dominance with tide influence. It is worth noting that no open coast setting is absolutely exempt from wave or tide influence. Three diagnostic criteria for the intertidal-flat deposits are proposed. Upon an upward-fining succession, (1) regular changes vertically from flaser bed-ding, through wavy bedding and to lenticular bedding are diagnostic of most of intertidal flats; (2) cyclical tidal rhythmites point to sheltered intertidal flats typically at the inner part of macrot-idal estuaries; (3) rhythmic alternations of storm and tidal deposition are diagnostic of exposed intertidal flats, especially the open coast types. Intertidal-flat deposits are generally topped by saltmarsh deposits, but underlain by different subtidal successions, like thick subtidal channel-fills, sand-bar complexes (sheltered coastal settings), and upwards coarsening successions of subtidal flats or thick subtidal sand ridge/bar complexes (exposed coastal environments).
