Ward Beach is a section of rugged coastline in the Marlborough Region of New Zealand that is known for unusual rock formations. The geological features include the exposed reef platforms that were uplifted by 2m or more during the 2016 Kaikōura earthquake, and the spherical concretions known as the Ward Beach boulders. Another formation known as the Chancet Rocks is located in a scientific reserve about 1.5km to the north of the Ward Beach roadend. They contain unusual trace fossils and provide amongst the best on-land evidence of the Cretaceous–Paleogene boundary in marine sediments in the Southern Hemisphere.
Ward Beach has been used as a launching site by a locally based commercial crayfishing company for more than 40 years. However, the uplift of the beach caused by the 2016 earthquake prevented the company from safely launching boats from the previous location. Over a period of several years, the company has sought options that would provide a safe place to launch from the beach. Most of these options have been opposed in environmental consent hearings because of the threat to endangered species. An exclusion zone has been established from just north of the Ward Beach road end to the Chancet Rocks, to protect the area from incursion by vehicles.
Introduction
Ward Beach is located on Marlborough's south east coastline, southeast of the town of Ward, and northwest of Kaikōura. The Flaxbourne River flows into the Pacific Ocean at the southern end of Ward Beach.
This section of the coast from The Needles in the south, to Chancet Rocks in the north, is known for its unusual limestone rock formations. The New Zealand Geopreservation Inventory includes three significant sites in the vicinity of Ward Beach: Flaxbourne River: folds and thrusts Ward Beach: concretions and wave-cut platforms Chancet Rocks: Cretaceous/Tertiary Boundary
There is road access to Ward Beach from the township of Ward. The Marlborough District Council has established a small reserve for day visitors, at the beach roadend.
The access road passes a lime quarry, close to the beach.
Uplift in 2016 Kaikōura earthquake
The Kaikoura earthquake of November 2016 created an uplift of around 2.5 to 3m at Ward Beach and Chancet Rocks.
Immediately following the earthquake, the uplifted rocks and reefs were covered with seaweed, crayfish, paua, sea snails and other marine life that was now exposed above the high tide mark.
The uplift of the beach caused the Flaxbourne River to change course away from its former estuary, cutting through the former bed of the estuary and beach gravels, and exposing more of the limestone rock beneath.
New surf break
The uplift caused by the earthquake changed the depth of water above the seabed offshore, and created a surf break that previously did not exist. The surf breaks to the left or right depending on swell angle, and is described as suitable for intermediate to expert surfers.
Ward Beach boulders
The large uplift of the seabed caused by the 2016 Kaikōura earthquake revealed spherical concretions on the raised rock platforms at Ward Beach. The concretions are similar to the Moeraki Boulders south of Oamaru.
The boulders are located about 800m north of the car park at the Ward Beach road end. These concretions were formed in the ocean floor in marine sediments from the late Cretaceous period (>65million years ago). They were formed over several million years in mudstone that was subsequently buried by overlying sediment. Concretions become harder and more dense than the mudstone that surrounds them, and this means they can remain even after the material surrounding them has been removed by erosion. The Ward Beach boulders are formed from dolomite – calcium magnesium carbonate.
Chancet Rocks
Formation
The Chancet Rocks are a limestone rock formation located about 1.5km north of the end of Ward Beach road. The area is designated as a scientific reserve. The outcrop is formed from a fine-grained white limestone known as the Amuri limestone. It originated as calcareous sediments deposited in the ocean on the continental shelf around 65 to 25 million years ago. The layers of limestone rock were originally laid down on the sea floor, but have been tilted upwards into an almost vertical position by deformation of the Earth's crust. Amongst the unusual features in this rock outcrop are large trace fossils, formed by animals that are currently unknown.