The geomorphic history of the Seal Rocks
Coastal landforms undergo changes based on the surrounding environment, notably the positions of the low and high tides and the movement and location of waves. The Holocene, which was colored by a rapid rise in sea level up to around 7000 years ago, changed many landforms due to marine sedimentation following the rise of sea level (Thom & Roy, 1985). However, this rapid rise was followed by a ‘standstill’ period, which lasts to this day. This has created an environment of stable temperature and other conditions for formation of coastal landforms.
A variety of factors affect the way coastal landforms are formed. These factors are both horizontal and vertical and need not occur within the immediate vicinity of the beachside to have an effect (Short & Wright, 1981). For example, deep-water wave climate and shallow water modification of waves play a significant part in the formation of coastal landforms. In Australia, these factors have coalesced in a dynamic and sensitive collection of beach systems, as well as bedrock, mud flats, and mangroves (Short, 2006). The stable period of the Holocene has contributed to the establishment of the necessary equilibrium for the formation of these landforms.
The site of this experiment is Seal Rocks Beach, located in the Mid North Coast region of New South Wales, Australia. It is characterised by a number of depositional landforms controlled by the distribution of bedrock composed of lower Carboniferous strata (Thom, 1992). Prior research points towards an interesting depositional history, which has led to the formation of Bridge Hill Dune, Lighthouse Beach, and Megaparabolic. These sights are especially interesting with respect to the Holocene, as they had begun to form after the beginning of the stable period.
The aim of this study is to investigate the formational processes of these landforms to establish any new changes from previous records. They will also be dated in relation to each-other.
Environmental Setting
Seal Rocks Beach is located in the South-Eastern Dune Fields area, characterized by dominant sand-moving winds from the South-East. It is a wave-heavy environment. Both of these factors have contributed to heavy topographical changes in regards to sand formations (Lees, 2006). There are five notable stages of deposition; of note are the latest two. Sediment accumulating in the Seal Rocks area over the course of the Holocene is primarily eolian in origin (Lees, 2006). Some of it was deposited prior to 6000 BP, likely in the early stages of the stable water level period (Lees, 2006). Many deposits started taking shape during that time but formed their current configuration much later, some as recently as 2000 BP (Lees, 2006). A more recent eolian instability has caused to sand movement and the formation of some of the youngest landmasses.
Experimental Design
The region was selected due to its narrowness in comparison to other regions, thus limiting the scope of study to a more manageable size. The sites specifically were chosen both for their ease of access and for the positioning in an area of heavy topographical changes. The sites are also relatively tourist-free, allowing for a lesser degree of effect from foot traffic and other side-effects of heavy human presence. The hope of this project is that the rapid changes to topography seen by the chosen sights will allow for easier gathering of data over a shorter period without the need to conduct an experiment for 17 years. It also increases the chances of seeing adaptational changes in local wildlife, including the rare fur seals that can be observed at Lighthouse Beach.
References
Lees, B. (2006). Timing and formation of coastal dunes in northern and eastern Australia. Journal of Coastal Research, 22(1), 78-89. West Palm Beach (Florida), ISSN 0749-0208.
Short, A, D (2006) Australian Beach Systems-Nature and Distribution. Journal of Coastal Research, 22, 1; 11.
Short, A. D. & Wright, L. D. (1981): Beach systems of the Sydney region. Australian Geographer, 15:1, 8-16.
Thom, B. G. (1992). Coastal Geomorphology and quaternary geology of the port stephens-myall lakes area. Australian National University, Dept. of Biogeography and Geomorphology.
Thom B. G. & Roy P. S. (1985). Relative sea levels and coastal sedimentation in southeast Australia in the Holocene. SEPM Journal of Sedimentary Research, Vol. 55.