Textural and compositional controls on modern beach and dune sands, New Zealand

Abstract

Textural, compositional, physical and geophysical determinations were carried out on 111 beach and dune sand samples from two areas in New Zealand: the Kapiti-Foxton coast sourced by terranes of andesite and greywackes and the Farewell Spit-Wharariki coast sourced by a wide variety of Paleozoic terranes. Our aim is to understand how long-shore drift, beach width and source rock control the sedimentological and petrographic characteristics of beach and dune sands. Furthermore, this study shows the usefulness of specific minerals (quartz, plagioclase with magnetite inclusions, monomineralic opaque grains) to interpret the physical processes (fluvial discharges, long-shore currents, winds) that distribute beach and dune sands in narrow and wide coastal plains. This was done by means of direct (grain size and modal analyses) and indirect (specific gravity, magnetic/non-magnetic separations M/NM, magnetic susceptibility measurements, hysteresis loops) methods. Results are compared with beach sands from Hawaii, Oregon, the Spanish Mediterranean, Elba Island and Southern California.Compositionally, the Kapiti-Foxton sands are similar to first-order immature sands, which retain their fluvial signature. This results from the high discharge of rivers and the narrow beaches that control the composition of the Kapiti-Foxton sands. The abundance of feldspar with magnetite inclusions controls the specific gravity of the Kapiti-Foxton sands due to their low content of opaque minerals and coarse grain size. Magnetic susceptibility of the sands is related mainly to the abundance of feldspars with Fe oxides, volcanic lithics and free-opaque minerals.The Farewell Spit-Wharariki sands are slightly more mature than the Kapiti-Foxton sands. The composition of the Farewell Spit-Wharariki sands does not reflect accurately their provenance due to the prevalence of long-shore drift, waves, little river input and a wide beach. Low abundance of feldspar with magnetite inclusions and free opaque grains produces poor correlations between specific gravity (Sg) and Fe oxide bearing minerals. The small correlation between opaque grains and M/NM may be related to grain size. The magnetic susceptibility of Farewell Spit-Wharariki sands is low due to the low content of grains with magnetite inclusions. Hysteresis and isothermal remnant magnetization (IRM) agree with the magnetic susceptibility values.

The geomorphology and evolution of a large barrier spit: Farewell Spit, New Zealand

“…The spit is composed of fi ne, very well to wellsorted sand. Dune sand is composed of 31% quartz (29% for the beach), 24% feldspar (beach 30%) and 45% lithic fragments (beach 41%) all derived from littoral drift along the west coast of the South Island (Kasper-Zubillaga et al, 2006).…”

Determinants of sediment properties and organic matter in beach and dune environments based on boosted regression trees

“…Textural properties of the beach and dune sands are assumed to be interdependent (Folk & Ward, ) and to be controlled by geomorphological processes and sediment source in a uniform manner (Gerrard, ; Pye & Tsoar, ; Kasper Zubillaga et al ., ). Increasing sediment movement – often estimated as wind speed, inverse of distance from the shoreline, disturbance or fetch – is generally expected to lead to larger mean grain size, poorer sorting and coarse skewed grain size distributions (Friedman, ; Pye & Tsoar, ; Arens et al ., ; Kasper Zubillaga et al ., ; Poizot et al ., ).…”

“…Textural properties of the beach and dune sands are assumed to be interdependent (Folk & Ward, ) and to be controlled by geomorphological processes and sediment source in a uniform manner (Gerrard, ; Pye & Tsoar, ; Kasper Zubillaga et al ., ). Increasing sediment movement – often estimated as wind speed, inverse of distance from the shoreline, disturbance or fetch – is generally expected to lead to larger mean grain size, poorer sorting and coarse skewed grain size distributions (Friedman, ; Pye & Tsoar, ; Arens et al ., ; Kasper Zubillaga et al ., ; Poizot et al ., ). However, other studies have found grain size to increase with growing distance from the shoreline (Kim & Yu, ), better sorting to be associated with increasing energy (Bryant, ), the grain size distribution to change from fine to coarse skewed with growing distance from the shoreline (Fox et al ., ) or no obvious textural trends along disturbance gradients (Livingstone et al ., ; Abuodha, ).…”

“…Several studies have revealed that the suggested relationships are highly dependent on the availability and textural quality of the sediment source (e.g. Bigarella et al ., ; Alestalo, ; Heikkinen & Tikkanen, ; Pye, ; Kasper Zubillaga et al ., ; Kasper Zubillaga et al ., ): grain size distributions may largely reflect parent material and, when well sorted and fine‐grained sediments are abundantly available, textural trends from e.g. beach to dune may not occur.…”

Grain size and geochemical study of the surface deposits of the sand dunes in the Mu Us desert, northern China

“…Analyses of grain size and geochemistry are the basic and most effective methods for understanding the modern processes of the Earth's surface and past environmental changes in the arid and semi‐arid regions of northern China (Liu et al, ; Chen et al, , , ; Yang et al, ; Dong et al, ; Xu et al, ; Zhu and Yu, ; Hu and Yang, ; Lin et al, ). Previous results demonstrated that the grain size and geochemical parameters can discern the sedimentary environment, mechanisms and processes, and possibly the material provenance of the different deposits (Pye, ; Pye and Zhou, ; Nesbitt and Young, ; Taylor and McLennan, ; Fedo et al, ; Kasper‐Zubillaga et al ., , b; Armstrong‐Altrin et al, ). For modern desert sediments across the monsoon marginal zone in northern China, grain size components and geochemical behaviours are mainly controlled by the desertification owing to their sensitive physical and geochemical properties and related environmental condition (Shen et al, ; Li et al, ; Liu et al, ; Yang et al, ; Dong et al, ); nevertheless, relevant research reports are still scarce.…”