金塘水道地形、底质与沉积环境

TOPOGRAPHY AND RECENT SEDIMENT IN THE JINTANG CHANNEL

全塘水道是一个典型的潮汐通道,南部有水深小于30m的北仑浅滩区,北部主要为水深大于50m的深水槽,呈S型贯通水道东西,深水槽底地形复杂,最大水深达110m,水下孤丘暗礁高达50多m,顶部距水面不足20m。水道底质分六类,粘土质粉砂占水道总面积约3/5,主要分布于水深小于40m的浅水区。砂类沉积物主要占居水深大于50m的深水槽。水道全新世以来的沉积物来源主要有三方面,其内部调整物质是重要的物质来源之一。而且对水道沉积物类型的分布格局起主导作用。多种特征表明,深水槽至今还受强潮流的侵蚀、塑造。北仑浅滩区的动力环境、地形条件均有利于细粒物质沉积。

The Jintang Channel is a typical tidal inlet,with a shoal area less than 30m deep along the southern bank and a S-shaped deep trough winding from east to west through the northern side of the channel.The trough possesses an irregular topographic feature,with the deepest spot measuring 110m below water surface while some shoal rocks rising 50m from bottom with some peaks beneath water surface less than 20m.The sediment samples reflect the presentation of six types.Clayey silt,a main sediment type distributed over shoal area,accounting for 3/5 of the whole area of the channel.Sandy sediment occupies the deeper part of the trough.The data suggests that the local reworked matter be one of the three main sediment sources for Holo-cene series which dominates over the distribution pattern of surface sediment.Up to now erosion and transportation by strong tidal current are still presented on the trough bottom,while fine sediment is accumulated in the shoal area owing to its alien topographic and dinamic conditions.