Reduction of greywacke sediments on the the Canterbury Bight Coast, South Island, New Zealand Thesis
- Author
- Hemmingsen, M.A.
- Year
- 2004
- Publisher / Organisation
- Geology, University of Canterbury
- Keywords
- Published Thesis
- Summary
- The coastline of the Canterbury Bight between Timaru and the southern end of Kaitorete Barrier is in long term erosion. Paradoxically, alluvial cliffs and several large, braided rivers drain from the rapidly eroding Southern Alps into the Canterbury Bight, transporting indurated sandstone of the Torlesse Supergroup, or grey wacke, to the coast. Catchment specific sediment yields average 1856 ± 261 t krn-2 yr1 compared with the world average of 182 t krn-2 yr"1 and are among the highest known specific sediment yields in the world. The large sediment loads from these Canterbury rivers are comprised predominantly of fine sediments as suspended load (more than 90 %), with only a small proportion of coarse bedload (less than 10 %), which is reflected in the nature of the mixed sand and gravel beaches. The Canterbury coastline is apparently abundantly supplied with sediment, which is transported northward forming Kaitorete Barrier. However, since the 1950's there has been very little accumulation of sediment against Banks Peninsula at the downdrift end. Previous research suggested that sediment is lost from the beaches due to abrasion.