The beach that I call Seadown Beach lies on a 20 kilometres stretch of North Otago coast between the mouth of the Waianakarua River and the headland of Cape Wanbrow just south of the city of Oamaru (see the two maps above on the left). This coast has been subject to active erosion for a number of years (see photo above, second from right). “Between 1957 and 2002, the average rate of erosion along Beach Road was about 50 cm per year, and a 2002 consultancy report estimated that this part of the coast had been eroded by up to 29 metres over 28 years in some places” (see Section 5.3 of “Planning on a Retreating Coastline: Oamaru, North Otago, New Zealand”, a 2009 GNS Report). One of the implications of this is that at high tides, care needs to be taken by fossickers to avoid being caught between powerful waves and the cliff at the back of the beach.
I have visited a number of points along this coast, finding that Seadown Beach best suits my fossicking purposes. On page 116 in her book, “The New Zealand Rockhound” (1981), Natalie Fernandez lists three places in this area as good for fossicking: All Day Bay, Kakanui River, and Waianakarua River (see photo above, far right). The Waianakarua River mouth lies at the southern end of this stretch of coast (see photos below). I visited there in March 2022, as described towards the end of this Post. There are lots of stones at the river mouth although a little bit north is a large rock shelf and further on are long stretches of sandy beach. My brief fossick here revealed a range of stones – some jasper and porphyry interested me. But there were not the smooth jaspers and quartzites that can be found at Seadown Beach. I have not ventured up the Waianakarua River itself. (An interesting general introduction to the river can be found in the Otago Regional Council 2018 report “Waianakarua River Morphology and Riparian Management Strategy”. A 1993 article on fossils found in the river has been published in the “Journal of the Royal Society of New Zealand”.)
I have been told by local fossickers that beach agates can be found along this part of the coast, and I have found a couple on the three brief visits I have made here.
Between the Waianakarua River mouth and All Day Bay, a stretch of about five kilometres, the beach is a mix of stones and sand, often with the stones towards the back of the beach, near the low cliffs. Some stretches of primarily sandy beach are also here. A handful of parking areas on the side of the road can be found, though making one’s way down the cliff can be tricky. Recently I was told by a friend that a fossick along this stretch one day had resulted in a number of agates, but another fossick not long after had not been productive. Freedom camping is allowed at All Day Bay, at the Orore Point end, where public toilets are also located (see here for a camper’s account of the camping area). Because of fossils found in the area, it is part of the Vanished World trail. Fernandez stated in 1981 that “agate, chert and plasma” can be found at All Day Bay (see photo on far right at top of this Page). The Otago Rock and Mineral Club has photos of agates and prase (limonite prase) found at All Day Bay (see two photos below, second row, far right).
I stopped to have a fossick at All Day Bay in March 2022. I parked at the camping area and walked out onto a very sandy beach. I then moved southwards to the rocky cliff of Orore Point – there I found some small pockets of stones in the rocks, but nothing worth collecting. The Bay beach seems to stretch for about five kilometres, plenty of room for stones to be found.
Just north of All Day Bay is the Kakanui River mouth, located inbetween Kakanui’s South Head and North Head (see the two maps below, left). The river splits the village in two, with a one-way bridge across the river about a kilometre from the coastline. This YouTube video provides drone footage of the river mouth area, including what is referred to on Google Maps as “Kakanui Beach”.
Kakanui Beach runs from the river mouth northwards to Kakanui North Head, also known as Cats-Eye Point. This YouTube video starts at the Point and shows the whole beach plus the Kakanui River estuary. White-baiters can be seen at the river mouth. Cars are able to drive from the Kakanui village store along Cobblestone Road to the river mouth and park on the narrow strip between the estuary and the sea, part of the shingle bar. There are lots of stones here, many well-worn by the river. It is worth a fossick, though my preference remains with Seadown Beach, which has a greater variety and more of the kind of stones I am interested in.
During my visit, I saw a wooden pole sticking up out of the sea, just seawards of the river mouth (see photo below, left). It turns out that the Kakanui area was a bustling one in the 1860s and 1870s with, among other industries, a meat preserving company, the largest in New Zealand at the time, and flax works. In the late 1860s, steps were taken to build a port here, and a substantial wharf was built (see photo below, second from left). Between then and the early 1880s, much produce moved in and out, with up to 80 ships calling per year. But Oamaru port proved a strong competitor as did the railways. The meat works closed in the 1880s, and Kakanui port ceased to operate in 1886.
Before leaving this area, a note on the Kakanui mineral breccia that can be found just to the north. I have sometimes found stones of this breccia on the beach and it looks interesting but does not polish.
Cats-Eye Point, at the north end of Kakanui Beach, has a sign pointing towards it for “Kakanui Mineral Breccia”, but there is no information provided about it despite, it seems, being of much interest to geologists, in New Zealand and internationally.
A guide for a self-drive tour of East and Central Otago geology directs you to Cats-Eye Point at Kakanui as the key site for Kakanui mineral breccia (see photo above, second from left). “The Kakanui Mineral Breccia is a mineral-rich fragmental rock which formed from the contact of an intruding magma with water about 31.6 million years ago (Early Oligocene). The resulting violent eruption totally disrupted the magma components into angular fragments… The site of the explosive eruption is in the centre of the bay immediately south of this point” (page 11). The guide goes on to provide a technical description of the constituents of the breccia on page 12. In 2017, a presentation about electron probe microanalysis referred to the use of Kakanui mineral breccia to develop probe standards, noting a number of geological aspects of the breccia. The presentation included a map of the breccia’s distribution along the coast (see photo above, centre). The Kakanui School Centennial History included a short chapter “Geology of the Kakanui District” which gave prominence to the mineral breccia (see below).
North of Cats-Eye Point (Kakanui North Head), rocky cliffs dominate the coast for about three kilometres, until the start of Seadown Beach. A sweeping stretch of beach runs from there for about five kilometres up to Cape Wanbrow, with the Beach Road Reserve located about three kilometres along (see map, below left). After parking near the start of Seadown Beach, you have to negotiate a steep descent of about 10 metres down to the sand. Once there, to the right (south) is the end of the rocky cliffs that define the southern edge of Seadown Beach. At low tide, it often pays to fossick for up to 200 metres or so along the bottom of those cliffs as piles of stones can be swept up to lie there. But watch out for the incoming tide, as well as for the occasional seal!
Walking northwards from the start of Seadown Beach (see photos below), the cliffs at the back of the beach are only four or five metres high, occasionally with large boulders having been dumped along them to minimise erosion. The beach is subject to daily change, with stones lying on top of the sand at times, under the sand at others. Often the best time for fossicking along this stretch is from mid to high tide when the waves lap the stones lying on the upper half of the beach.
Kakanui Beach Road Reserve lies three kilometres from the southern end of Seadown Beach. I stopped there for a fossick in June 2020. At that time, the stones were much more scattered on the beach than at Seadown Beach, though I spotted some interesting jaspers.
I have not visited the beach north of the Kakanui Beach Road Reserve.
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Hello! I’m a geology student and I’m visiting Kakanui this week to look at the mineral breccia. I came across your site from a google search and I found the guides you’ve posted to be very helpful. Looks like I’ll have to pay a visit to Seadown Beach too while I’m in the area – your tumbled stones are very beautiful!
Hi Janice. Thank you for your Comment. I am pleased my site was useful. I hope your visit to Kakanui goes well.