Armstrong Bay Maritime Archaeology Project

The so-called Mahogany Ship remains on of Victoria’s and Australia’s most perplexing maritime mysteries. There have been numerous searches for the wreck, reportedly first seen in the coastal dunes of Armstrong Bay in south-western Victoria in 1836. ShipShapeSearchers utilised geoarchaeological methods to test an historical account of the wrecks first sighting, in which its location is described in terms of prominent geological features, lines of sight and measured distances. The approach taken extracted geological and positional data from the historical account and translated them into graphical results using GIS. One key piece of information used in the study, which previous searchers either have ignored or failed to recognise, is a cross bearing. The study provided a possible explanation for the wreck’s position in the dune, a proposes and an provided a possible explanation for the wreck’s position in the dunes, and proposed an area measuring only 500 m x 100 m wherein the shipwreck is likely to be found.

Our most recent findings are described in our article published in Australasian Journal of Maritime Archaeology: 41, 2017 entitled ‘Locating the ‘Mahogany Ship’: Using Geoarchaeological Methods to Test Historical Sources’,We showed how a geoarchaeological approach, using modern software tools and remote sensing data, can be applied to testing historical sources. We are arranging two separate but related projects. The first is a remote sensing search of the seabed around Helen Rock and towards the lagoon opening. The finding of underwater artefacts by this survey may support the theory that the ship entered the lagoon. Our second project is a detailed investigation of the identified search site zone described in our publication. Such a finding of artefacts would then lead us to prioritise our land search.

Lieutenant Stanley’s Admiralty Chart, 1872. Arrow indicates position of Helen Rock.

Armstrong Bay is part of the Australian Coastline known as The Shipwreck Coast. In this area, history, oral traditions and archaeology all give testament to many voyages that ended before reaching their destinations. Such endings as wrecks are the result of encounter of a vessel with the shore or seabed. This bay has numerous accounts of sightings of wrecks, with some records going back over a hundred years and some believe vessel remains have been covered by encroaching sands, in the dunes or just offshore by tidal action.

Detail of Lieutenant Stanley’s Admiralty Chart, 1872. Indicates Helen Rock at one fathom.

Detail of Lieutenant Stanley’s Admiralty Chart, 1872. Indicates Helen Rock at one fathom.

Within Armstrong Bay, about one mile (one and a half kilometres) offshore lies the probable culprit for one or more such wrecking events. ‘The culprit’ appears on old maps, as well as new charts as Helen Rock. This submerged outcropping rears up from twenty to thirty metres off the seabed, to lie in wait just below the surface of the sea. One old map from the late 19th century map shows Helen Rock to be just ‘one fathom’ below the waterline (see figures 2 and 3 ). Another witness describes the rock as sometimes breaking the surface. Helen Rock is a hazard to sea traffic, as such it is part of a ‘ship trap’, that is formed by a combination of hazards. It is marked as being so on charts now, and has been in the past. In the event of a large vessel colliding with ‘the Rock’, the distressed vessel may have had to jettison fittings and/or equipment such as anchors and cannons to lighten its weight to help its chances of gaining the shore. Heavy material such as iron, would have sunk straight to the seabed and if of sturdy enough or resistant material would remain in place today. This jettisoned material may be found and give us information about what lies in and around Armstrong Bay.

Profile of Helen Rock processed from Bathymetric Lidar. Sea level from time of scan indicated.

Profile of Helen Rock processed from Bathymetric Lidar. Sea level from time of scan indicated.

Multibeam sonar survey results of Helen Rock and surroundings, superimposed over satellite imagery.

Multibeam sonar survey results of Helen Rock and surroundings, superimposed over satellite imagery.

Detail of multibeam sonar survey of Helen Rock.

Detail of multibeam sonar survey of Helen Rock.

We at ShipShapeSearchers are the only research paper authors to identify the key role likely played by Helen Rock in the ‘Mahogany Ship’ wrecking event. We proposed this idea in 2013.  To this end, Armstrong Bay M.A.P (Armstrong Bay Maritime Archaeology Project) was conceived in 2012 and is now being carried out (Our original proposal can be found here). Bathymetric Lidar data from the Victorian Government has provided high-resolution contour mapping of the Armstrong Bay seabed. At our personal request on behalf of ShipShapeSearchers in 2013 Daniel Ierodiaconou, Oceanographer under the auspices of Deakin University, performed a multibeam sonar scan of Helen Rock and its surroundings. This showed the nature of the seabed as well as the contours of Helen Rock. The results showing open sand areas, and rugged, rocky patches are promising for artefact preservation. Heavy, ferrous (iron) materials lying on the seabed are likely to be detected using a seaborne magnetometer; by detecting changes caused in the Earth’s magnetic field due to the presence of iron objects, it is possible to pick these out, even if buried under sand or covered by sea grasses. By detecting the presence of these historically relevant artefacts we can invoke the ‘ship trap’, backing up our lagoon access theory.