T112 Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation (Posters)

Monday, 16 October 2023
8:00 AM - 5:30 PM
Hall B

PREPARATION OF MARINE SURFACE SEDIMENTS AROUND TE PATAKA O RAKAIHAUTU (BANKS PENINSULA) FOR PROVENANCE ANALYSIS USING PXRF

Paper number: T112-20
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

In modern sedimentary environments such as the marine areas around Te Pataka o Rakaihautu (Banks Peninsula), New Zealand, provenance research can clarify sediment dynamics. Understanding the sediment transport dynamics of this location is of particular importance because of the impact of sedimentation on the ecology and the cultural significance of local marine biota. Potential sources of sediment include local basaltic volcanic deposits and loess deposits. The northern Waimakariri River and southern Rakaia River may also supply sediment that is deposited around the peninsula via longshore transport.

The aim of this research is to develop a methodology for treating marine surface sediments for provenance analysis using pXRF. Currently, there is no standardised procedure for removing carbonates and organic materials from marine surface sediments prior to pXRF analysis. Here we show that common treatments (HCl, H2O2, and Loss on Ignition) affect unintended elements, thus biassing the results. We found that drying the sample in a 60 ℃ oven for ~12 hours and then handpicking carbonates >2 mm in size produced the most stable results. Following this procedure, we prepared a preliminary set of marine surface sediment samples, on which we performed pXRF analysis. Our preliminary results show that some samples have geochemical signatures that overlap with the geochemical signature of Lyttelton Loess, while few samples overlap the geochemical signature of local volcanic deposits. Additionally, most samples overlap with the geochemical signature of southern beaches and the Rakaia River sources, and fewer samples reflect the geochemical signature of northern sources and the Waimakariri River. This is consistent with existing research which suggests a strong overall northward current. Our findings demonstrate the potential for provenance studies to address the issue of sedimentation around Te Pataka o Rakaihautu and also provide a methodology for future pXRF analysis of samples.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395990

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