Quaternary Geology and Sedimentary Processes in the Vicinity of Six Mile Reef, Eastern Long Island Sound
Quaternary Geology and Sedimentary Processes in the Vicinity of Six Mile Reef, Eastern Long Island Sound
复制标题
东长岛海峡六哩礁附近的第四纪地质和沉积过程
DOI：
10.2112/06-0743.1
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发表时间：
2008
影响因子：
17.3
通讯作者：
E. F. Doran
中科院分区：
文献类型：
--
作者：
L. Poppe;S. Williams;M. S. Moser;N. Forfinski;Helen F. Stewart;E. F. Doran
摘要六里礁是一个东西走向的桑迪、高22 m的浅滩，位于康涅狄格州海岸外约7.8 km处，其核心是冰后期海洋三角洲沉积物，其上覆盖着潮汐改造的现代沉积物。沉积环境关闭东端的浅滩的特点是与长期侵蚀或nondeposition，流动沉积物有限的海底装甲砾石砂，和分散的细长领域的barchanoid沙波的过程。该barchanoid波达到20米的振幅，是凹向西，并在个别和合并的形式，逐渐变得更加复杂的西发生。浅滩及其附近海底的特点是与粗推移质输运有关的过程，主要覆盖着不对称的横向沙波。横波振幅超过8米，滑动面主要朝向西部和西南部，波峰直，稍弯曲。模仿沙波不对称性的巨波纹通常出现在风浪斜坡和波谷;海流波纹无处不在。大型底形的幅度和丰度在六里礁以西明显减小。那里的海底覆盖着小的、退化的波纹，反映了与海底沉积物的分类和改造有关的低能环境和过程。巨波纹和目前的沙波的波纹表明，运输是积极的，床型传播在目前的水力制度。净推移质输沙主要是向西，表层沉积物的纹理趋势，方向的barchanoid波，和不对称的横波和周围的基岩露头，巨石和沉船的冲刷痕迹证明。一个例外发生在浅滩的西端，沙波形态表明长期向东运输，这表明在这一地区的逆流塑造浅滩，是重要的维护。
Abstract Six Mile Reef, a sandy, 22-m-high shoal trending east–west and located about 7.8 km off the Connecticut coast, has a core of postglacial marine deltaic deposits mantled by tidally reworked modern sediments. Sedimentary environments off the eastern end of the shoal are characterized by processes associated with long-term erosion or nondeposition, a mobile-sediment-limited seafloor armored by gravelly sand, and scattered elongate fields of barchanoid sand waves. The barchanoid waves reach amplitudes of 20 m, are concave westward, and occur in individual and coalesced forms that become progressively more complex westward. The seafloor on and adjacent to the shoal is characterized by processes associated with coarse bedload transport and covered primarily with asymmetrical transverse sand waves. The transverse waves exceed 8 m in amplitude, have slip faces predominantly oriented to the west and southwest, and have straight, slightly sinuous, and curved crests. Megaripples, which mimic the asymmetry of the sand waves, are commonly present on stoss slopes and in troughs; current ripples are ubiquitous. The amplitude and abundance of large bedforms decrease markedly westward of Six Mile Reef. The seabed there is covered with small, degraded ripples, reflecting lower-energy environments and processes associated with sorting and reworking of sea-floor sediments. Megaripples and current ripples on the sand waves suggest that transport is active and that the bedforms are propagating under the present hydraulic regime. Net bedload sediment transport is primarily to the west, as evidenced by textural trends of surficial sediments, orientation of the barchanoid waves, and asymmetry of the transverse waves and of the scour marks around bedrock outcrops, boulders, and shipwrecks. One exception occurs at the western tip of the shoal, where sand-wave morphology indicates long-term eastward transport, suggesting that countercurrents in this area shape the shoal and are important to its maintenance.