11 Our Dynamic Coasts: Monitoring Coastal Evolution and Deformation Processes

Tuesday, 29 March 2011
10:30 AM - 12:00 PM
D.H. Holmes A & B

INTERPRETATION OF COASTAL PROCESSES BASED ON GEOCHEMICAL AND TEXTURAL ANALYSIS OF SEDIMENTS, CONRADS BEACH, NOVA SCOTIA

Paper number: 11-5
Program: Symposia Sessions
Time: 11:30 AM – 11:45 AM

Authors

Abstract

Coastal processes sort sediment based on its grain size and density, these textural properties can be used to interpret the depositional environment, transport processes and parent material of a deposit. The mineralogy of sediment is also affected by these sorting processes, for example higher concentrations of quartz grains are found in higher energy environments compared to low energy environments where feldspar or mica are more common (for example the swash zone compared to dunes). While the mineralogy of sediments can be relatively easily determined with an ocular microscope, it is time consuming to compare sediments from numerous samples and results are dependant on the interpreter’s skill and experience. Geochemical analysis is comparatively rapid and provides repeatable, quantifiable comparison between sediments. To test the efficacy of using geochemistry to measure sediment maturity on a sandy beach, two transects of samples from the backshore to the lower foreshore were collected and geochemical analysis completed on the unsorted samples. Sedimentary textures were also determined using sieves and scales.

The site selected for the study was Conrads Beach, on the eastern shore of Nova Scotia, is a sandy, low angle dissipative beach on the Atlantic Coast. Bedrock in the area is meta-sandstones (greywacke), and the beach is flanked by drumlins composed of distally sourced igneous clasts within a matrix derived from red (iron stained) sandstones. Iron is a useful element for sample comparison because it is found in high concentrations in erodible minerals such as biotite, and in low concentrations in quartz. From the results iron values show low concentrations in the swash zone where quartz grains are the dominant material. In the dune, composed of coarser, softer fragments with a shorter transportation history, the concentration of iron is the highest of each transect. Overwash deposits in the backshore are in between these values, likely reflecting transport in higher energy environments, but for shorter periods of time than the swash zone.