Palmer, J., C. Turney, A. Hogg, N. Hilliam, M. Watson, E. van Sebille, W. Cowie, R. Jones, and F. Petchey, 2014, The discovery of New Zealand’s oldest shipwreck- possible evidence of further Dutch exploration of the South Pacific, Journal of Archaeological Science, doi: 10.1016/j.jas.2013.11.024
The historical time line of South Pacific Ocean exploration and mapping of Tasmania, east coast Australia, and New Zealand begins in 1520 when Portuguese explorer Ferdinand Magellan discovered the passage from the Atlantic Ocean to the South Pacific Ocean via the Magellan straight. More than a century later in 1642-43 Dutch explorer Abel Tasman visited the area, followed by British Captain James Cook in 1768-71. However, there is speculation that there were additional explorative voyages by the Dutch between Tasman and Cook centered on Dieppe Maps which contained the north east Australian coast with Portuguese names. It is even suggested that Captain James Cook used the maps during his 1768 voyage. Further support is written in Cook’s notes when he documents Maori (native people of New Zealand) tales of ships that had been wrecked and the crew eaten, and the eventual acknowledgement by Cook that he had been preceded by another vessel. Debris from a ship wreck found in Midge Bay near Kaipara Harbor on the west coast of Northland in Northern New Zealand (Latitude 36° 22’ 27” South, Longitude 174° 10’ 20” East; Figure 1) may be the first physical evidence of this voyage, making it the oldest shipwreck of New Zealand.
The debris, including parts of the hull like a teak plank, rib sections, iron nails, and copper sheeting were recovered in 1982 before the remainder of the wreck was reburied by tidal and wave action. The wrecks location was identified for this study using a high resolution magnetometer to narrow down an approximate position. Then researches took a higher resolution survey of a 40 x 40 meter area using a walking gradiometer at .5 m grid spacing to identify a definitive location (Figure 2). From the data collected the ship is identified as a dipole anomaly. Scientists were looking for a signal that was an appropriate size for a ship wreck and that had the magnetic intensity concurrent with an object with minimal iron content. Two limitations to their wreck-locating approach are the high background in the magnetics data because of iron-sand deposits and deep geologic structure across the area, and that the surveys could only be done during low tide.
Polished samples of the ships wood types, Teak and Lagerstroemia spp., were analyzed to try and reconstruct the original trees’ sizes. Analysts used information on the number of rings and the ring thickness’, and accounted for sapwood and heartwood that wasn’t used for the construction to make their estimations. The teak samples had variable ring thicknesses, an indicator the tree origin is from a moist climate. Comparison with modern trees from a similar environment, and estimates of growth rate and size based on tree rings, were used to estimate how old the tree was when cut down.
Radiocarbon dating by accelerator mass spectrometry was used to determine the 14C age of the wood. The ages were calibrated using the Northern Hemisphere radiocarbon calibration dataset IntCal13 by wiggle matching (fitting several unknown data points in a constrained sequence to a calibration curve) to obtain an accurate and precise calendar age of the sample. The varied ring thickness of the teak gave it a wide range of 14C age between1670-1944. In contrast, the Lagerstroemia spp. has clearer rings, and a smaller 14C age range between 1663 and 1672 was determined.
The time the vessel was constructed was estimated by assuming time for the wood to have been seasoned and transported. The high demand for building materials in that point in history and traditional curing methods of teak yield an estimated construction time to be 1705 A.D. give or take 9 years, placing it in the right time period to have visited the region after Tasman and before Cook.
To resolve the question of whether the investigated wreck was a local event or if it was transported to where it was found records of ship wrecks and data of regional ocean circulation were considered. Wrecks are not uncommon in the 6 km wide opening of Kaipara Harbour which is subject to strong westerly winds and tides, and hosts several shifting sandbars near (.5 meters) the water’s surface but far (2-5 km) from the coast. The entrance to the harbor has reports of 43 ship wrecks, the first from 1840, while the Kaipara coastline region has 113 shipwrecks, all of which were vessels sailing nearby, as oppose to the debris being transported by currents. In addition, drift data available by the Global Drifter Program suggests the local currents are too weak and variable to have transported the wreck.
The ships origin is analyzed based on the wood type. Teak is a tropical timber that is native to India, Indonesia, Malaysia, Myanmar, Northern Thailand, and Northwestern Laos. Properties like natural durability and stability make it a highly demanded supply for shipbuilding. Lagerstroemia spp. is native to Southeast Asia and would have been available in Java (then Batavia) and India during the estimated time of construction. An additional finding supporting a temperate origin is evidence of the bivalve Teredo navailis, a naval shipworm, which shortens the life span of wooden ships in the temperate and tropical waters. The presence of shipworm could explain the copper sheeting on the hull recovered in 1982. It is known that the Dutch often used copper to protect vessels from shipworm as early as 1670, compared to the English who didn’t start using it until the mid-late eighteenth century; clues like these help puzzle together where the ship came from.
Evidence from wood type, age reconstruction, materials, and ocean circulation have led investigators to conclude that the wreck is likely of Dutch origin, took place between the visits of Tasman and Cook, and is the oldest wreck known in New Zealand. Further works including an extension excavation of the wreck is needed to confirm the preliminary findings of this research.
The information obtained from this research and the like helps reconstruct a more complete picture of world history. The techniques used in the investigation demonstrate the valuable information available with just a little digging and some math.
Happy Pi day!