Coarse Estuary Mouth Ballast Gravel Deposits: A Sourcing Case History
详细信息 查看全文
文摘
Pebbles and cobbles along the channel margin of the Tayport-Tentsmuir tidal flats rest on eroded surfaces of layered sands. Their origin and source have been hitherto unexplained, although they are evidently relatively local. The compositional assemblage of the well-rounded clasts is compared with those of pebbles in the tills and fluvio-glacial deposits of Fife and Tayside, in the River Earn and in the River Tay at Perth. The closest similarity is with the latter site. It is suggested that the material was transported to Tayport as ballast for lighters prior to trans-shipping of cargoes for Perth from larger vessels moored off Tayport. A sloop or brig of 100 tons would have carried about 20 tons of ballast. Trading by one vessel per week over a time period of a century could have accounted for the transport of 100000 tons of the material concerned. Removal of the ballast by barge from Tayport enabled the building of Lucky Scalp island. Attempts to improve the underfoot conditions for salmon fishing are believed to have been responsible for the spreading of ballast along the outer margin of the tidal flats.