Hawkes Bay

NZ’s First Reptile Discoverer returns to Mangahouanga

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In 1958, Petroleum Geologist Don Haw was mapping the rocks in the Mohaka river catchment of Western Hawkes Bay. The project was part of a wide ranging exercise to evaluate the hydrocarbon potential of the East Coast basin at that time for BP, Shell and Todd.  His discovery of reptile bones in the Cretaceous sediments was recorded on Company maps which subsequently caught the eye of Joan Wiffen in the early seventies. She ventured into the region to take a closer look. Remarkably this led to her eventual unearthing of New Zealand’s first dinosaur fossils, as well as many other new species of exciting Cretaceous reptiles. For her significant effort Joan became known as the “Dinosaur Lady”.  For his essential initial work, Don was awarded the Wellman Prize in 2001. On March 24th 2012, 54 years after his initial explorations,  Don returned to Mangahouanga along with the teachers and school children who were participants of our GNS Science “Dinosaurs and Disasters Geocamp“. This was a historic day as it was his first return to the valley in all that time. In the photo, Don (centre) is with Robyn Adams, one of Joan Wiffen’s long term fossil hunting assistants who still leads trips into the valley. In the following transcript, Don describes his experiences from all that time ago:   “We were mapping outcropping sediments in the Upper Mohaka river tributaries, observing for the first time, what might be there. Nobody had really mapped that steep isolated terrain before. We were keen to find what was present between the greywacke basement rocks and the overlapping Upper Tertiary sandstone section. Perhaps nothing – we just didn’t know – maybe the Upper Tertiary rested directly on basement.   Was there any Cretaceous section exposed?  This was so important to the assessment of the hydrocarbon prospectivity of the region.”   “It was high summer, February 1958 I think, and we were scrambling up this really difficult stream bed, huge boulders, and totally bush covered. We recognised we were stepping on boulders and outcrops of massive concretionary sandstones which we had not seen before. These appeared to be of marine origin, and had fine shell debris in them which was triggering off alert signals to me – There might be other important fossils here!  We should look carefully! I was with field assistant Ken Fink Jensen to whom I owe much for his support and encouragement in those days, Together we began to examine some odd protuberances on the surface of certain boulders, which I quickly recognised, because of their shape and texture, had to be organic and which were almost certainly bone remains from some marine creature.  I think my initial reaction was that they were fish remains. The rock was hard, very hard, and we extracted several and brought them back to Gisborne.“ “They were sent off to Jack Marwick, a retired NZGS chief palaeotologist,  who identified them as reptilean bones. Eventually they were recognised to be Mosasaur fossils, a type of  marine Plesiosaur.  It was a first for New Zealand.”   “This region became the hunting ground of Mrs Joan Wiffen who followed up our fossil discovery, with many years of hard work there, excavating numerous other finds from the same stream bed.  She, with her husband and family team, found many new fossils, some really exciting, including some terrestrial dinosaur remains which must have been washed into those early primeval seas. It has now become one of the most prolific fossil sites in New Zealand.”The final image shows a mosasaur skull that was found by Joan and her team and is now kept at GNS Science in Lower Hutt.

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Lake Tutira – tectonic uplift, ice ages, landslides and cyclones

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Lake Tutira is a scenic spot on the route between Napier and Wairoa in northern Hawkes Bay. It is in a very rural setting, surrounded by steep hillsides and farmland. The landscape around the lake contains several powerful geological stories. The first is that the hills themselves, made up of rocks that are about 1.8 million years old, reach a height of up to 800 metres above sea level. Before being uplifted and exposed by erosion, the rocks may have been buried to depths of 500 to 1000 metres. This means that they have been rising at an average rate of about a metre every 1000 years. When you look at this steep hillside, you can see lines of cliffs running almost horizontally across the slopes. These bluffs are made of relatively hard limestone, with softer muds and sandstones hidden beneath the grassy slopes separating the cliffs.The top limestone band that you can see correlates with the one on the top of Waipatiki Beach that I showed in a recent post. These cliff lines therefore represent the cycles of global change that repeated every 40000 years. The hard limestones were deposited as sea levels were slowly rising, while ice caps melted at the end of each glacial period, as shown also in my previous posts from Waipatiki and Darkeys Spur. The next landscape feature of interest is this area of grassy hummocks just beyond the pine plantation. These are the debris pile from a massive landslide that slid down from the nearby hills about 7200 years ago. It blocked the stream that flowed down the valley, thus forming the present day Lake Tutira.  Similar huge rock slides occurred in other parts of the region at the same time. Scientists believe that they may have all been triggered by a single massive earthquake. One of our activities on the recent ‘Dinosaurs and Disasters Geocamp” with Hawkes Bay schools was to drill a sediment core from Lake Tutira. Kyle and Richard used a PVC drainpipe which they pushed into a shallow part of the lake bed. Although only about half a metre in length of core was extracted, you can clearly see a number of layers. The top of the core is to the left of the photo, with several organic rich layers visible. The lower half consists of varying amounts of pumice that will have been washed into the lake from where they accumulated after the Taupo eruption 1800 years ago. The lakefloor sediment has in fact been studied in detail by researchers from GNS Science and other institutions . In 2003 a drill rig was set up that retrieved a 27 metre core right through to the base of the sediments. It revealed a detailed history of the environment around Lake Tutira over the last 7200 years: Almost 1400 storms were intense enough to leave their traces in the form of layers of mud washed down from the surrounding hills. Periods when storms were more common started abruptly and could last for several decades. Volcanic eruptions from the Taupo Volcanic Zone (including the well known ‘Taupo Eruption’ of 1800 years ago)  have left layers of ash that can be dated. Changes in land use from native forest to pasture due to human occupation, have increased the sedimentation rates tenfold.. During Cyclone Bola which passed over Hawkes Bay in 1988, over 750 mm of rain fell over four days.  A huge number of mudslides came off the hillsides over the whole region. In this photo, Richard Levy and I have exposed a buried soil layer next to Lake Tutira. It is beneath about metre of pale brown ‘Cyclone Bola Mud’  (top half of image). The dark soil layer below contained branches of wood. Further down there was another pale coloured mud layer from an earlier rainstorm.

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Darkeys Spur’s rock record of sea level change

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Along with Waipatiki, another excellent Hawkes Bay locality for looking at rocks laid down over a cycle of sea level change is Darkeys Spur, about twenty minutes by car west of Lake Tutira. The road is very narrow and care should be exercised to park safely and watch out for vehicles. Fortunately the road is not a busy one. The road winds up a hill and the rocks are well exposed in the cutting on the uphill side. Kyle Bland of GNS Science has mapped the geology of Hawkes Bay in detail. He showed me what there is to see at Darkeys Spur, and also led our recent Geocamp visit there. As at Waipatiki Beach (see previous blog post) the deepest water deposits are grey muds with occasional oyster shells. Not far up the sequence, the colour changes, the particle size increases and a wide variety of fossils starts to appear in rocks which now indicate decreasing water depth. In this close up image, you can also see that the shallower water sediments are cross bedded, indicating strong water currents. The bivalve shells are also facing concave side down which is what happens to them when washed along by moving water. This indicates very shallow water just below or within wave depth. A little further up the road, the rock type (lithology) changes to gravels, indicating a beach environment as sea levels decreased further. In this image you can see the marked transition between the nearshore sediments and these gravels. Finally, river gravels can be found mixed in with the beach gravels. They can be distinguished because the stones on a pebble beach tend to be flat whereas in a river bed they are more rounded or blocky shaped, such as the ones that Kyle is showing here.. Above the gravel deposits (seen in the lower cliff in the centre left of this photo),  there are lime rich sands (upper cliff), indicating that sea levels were  rising again. At the time when these deposits were laid down, these sea level cycles were about 40000 years long, related to the variation in the tilt of the earth’s rotational axis. Rock records that show cycles of sea level change are also found along the Wanganui coast for example at Ototoka Beach. They offer a globally significant geological insight into the way polar ice sheets have expanded and retreated during repeated ice ages.

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Dinosaurs and Disasters Geocamp 2012

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Over the last two weeks, GNS Science, with support from the Todd Foundation, The Royal Society and the National Aquarium in Napier, has been running a ‘Dinosaurs and Disasters Geocamp’ for a group of Hawkes Bay Intermediate level students and teachers. The participants investigated many landforms and cliff sections around Hawkes Bay. GNS Science geologists Kyle Bland and Richard Levy also helped to organise and lead the Geocamp. In this photo they are encouraging the participants to look closely at a cliff section with fossils and structures above Lake Tutira that help explain the formation of the lake by a giant landslide. One of the participants Michael Young is showing a section of sediment core that we drilled out of the bed of Lake Tutira using a length of drainpipe, and then wrapped in clingfilm for transport back to our base at the Napier Aquarium. Kyle Bland is seen here, showing participants how sediment from Waipatiki Beach is washed and sieved so that it can be checked for microfossils. The two week geology immersion experience was created to open the eyes of young people, their schools and the local community to the wonders of the natural environment in their local area. It culminated in a two day expo created and run by the students to show their discoveries to the public. In the photo Phoenix Hancox-Thompson is introducing visitors to some of the activities. Here are a couple of videos that capture some of the activities and the enthusiasm of the participants. The first looks at some of the locations we visited: The second is a chance to learn geology from some very bright young geoscientists:

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Tyre Tubing the Mangahouanga Stream

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On our second day in the Maungataniwha Forest, some of us explored the lower Mangahouanga Stream using the well established kiwi river transport method of tyre tubes. This allowed us to visit parts of the river that would otherwise be very difficult to reach. Initial access to the river was via bush bashing through pine and then native forest, and down a steep climb to the water’s edge. In the second photo I am following Ben towards our next fossil hunting stop off. James Crampton gets speedy on one of the faster sections of the stream. Where possible we stopped to closely inspect each boulder for the tell tale signs of fossil bones, wood or shells. Here is an example of fossil reptile bone (centre of photo). Because of the hard surrounding rock, these bones are not removable except using painstaking laboratory methods over many months. Although we found several interesting fossils, we were surprised that they did not seem to be as abundant as they were in 2009. This will have been due to the higher river levels, and the random redistribution of boulders during occasional flood events. Pete Shaw, forestry conservation manager, about to launch down some rapids. Finally we arrived at the Rockhounds Huts, – built by Joan Wiffen and her team in the seventies as a base for their summer explorations of the Mangahouanga Stream.

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Reptile Fossils from an Unexplored Valley.

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The first barrier to accessing Mangahouanga Stream Three years ago I visited Mangahouanga Stream in Hawkes Bay  along with a group of GNS Scientists. This is the area where Joan Wiffen, New Zealand’s famous “Dragon Lady” found the only known bones of dinosaurs from New Zealand, as well as various marine reptiles, prior to her retirement from fieldwork about ten years ago. I described this visit in my blog at the time. What I didn’t mention in my blog was the existence of a remote valley that we believe might have only been visited once by a geologist prior to 2009.  The valley is a tributary of the Mangahouanga Stream. Pete Shaw with marine reptile bones from Wiffen Valley As well as being protected behind a large privately owned forestry block, this hidden valley is made particularly inaccessible by a high waterfall and densely forested ridge. Along with the forest manager Pete Shaw, I had managed to enter the valley via very steep and rugged bush in 2009. We spent several unforgettable hours travelling down the un-named stream (now called Wiffen Stream), finding several Cretaceous reptile bones in large concretions. The photo shows Pete in 2009 with the prize find of the day moments after he pulled it out of the stream. It is a cluster of several reptile vertebrae, subsequently identified as belonging to an elasmosaur. Although heavy, Pete managed to carry it out, whereas most of the fossils we found that day had to be left in place. Last week I returned to the area with a team of GNS palaeontologists along with Victoria University student Ben Hines. One of our aims was to explore the hidden Wiffen Valley to  have a closer look at its geology and fossils, This photo shows GNS palaeontologists James Crampton and John Simes in the upper section of Wiffen Stream. There were log jams, tree trunks and waterfalls to negotiate as we travelled down the stream. We took our time to throughly check out the boulders for fossils as we moved slowly along. The reptile bones are typically found in very hard concretions like this one. We were unable to identify this particular bone, or remove it from the concretion, so it was left in situ along with several others that we saw. In this photo  Marianna Terezow of GNS Science can be seen tackling the dense bush that must be traversed to access and return from the hidden valley.

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Te Mata Peak

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Last week, following my visit to Castlepoint I also headed further north to Hawkes Bay. State Highway 2 runs parallel to the central North Island mountain ranges, which had just received fresh snow from a recent southerly blast, to provide a classic New Zealand pastoral scene… Te Mata Peak near Havelock North is a popular spot for runners, hikers and paragliders. On a clear day there are  spectacular views across the landscape from the coast all the way to the volcanic peaks of Ruapehu in the centre of the North Island. The buttresses of Te Mata Peak are made of Awapapa Limestone. This formation, which is about three and a half million years old, is also found to underly other nearby coastal hills in the Hawkes Bay area. It was formed along a string of offshore shallow water shoals and tidal banks. At that time the coastline was about 40 kilometres to the west, along the present edge of the central mountain ranges. In between, the sediments of the same age are mudstones that represent much deeper water than the Awapapa limestone. Armed with my Kiwi Fossil Hunter’s Guide, I located a way to climb down on the eastern side of the peak to have a close up look at the cliff section just north of a radio mast, a few hundred metres down from the summit car park.  Although there isn’t a wide variety of fossils in these rocks, there were some vary well preserved specimens such as these examples of a scallop called Phialopecten marwicki, as well as barnacles, oysters, brachiopods (lamp shells) and coral-like bryozoans. In places, thinly bedded layers of shell fragments show that water currents were strong, indicating shallow water conditions when the limestone was deposited. Careful research by scientists has found that the alternating bands of hard, strongly cemented grey limestone and softer, orange sandy layers represent cycles of sea level change during the Pliocene Epoch. The harder layers formed because at shallower depths there were more water currents, which allowed more calcium carbonate rich water to flow through the sediments. This would have been during the ice ages, when huge amounts of sea water were locked up in polar ice caps, thus lowering the sea level. The warm period (interglacial) deposits have less carbonate cement to strengthen them and are therefore etched out more easily by erosion. These deeper water sediments are now underneath overhangs of the harder layers. The example here had clusters of large oyster shells scattered within it.

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Cretaceous Reptiles in Hawke’s Bay

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Over the last few days I have been with a GNS Science team exploring the remote Mangahouanga Stream in inland Hawkes Bay. This is the area that is famous for the discoveries of dinosaur and other reptile remains by Joan Wiffen (who died in June last year) and her team. It is on private land, deep in the forest and therefore rarely visited. Bones of marine reptiles seem to be relatively common in the hard concretions in the stream bed, but land dwelling dinosaur remains are very rare as they were washed some distance into the sea and separated before being buried in the sediments . An example of a therapod dinosaur toe bone, discovered by Joan Wiffen can be seen as a 3D image here On the way to explore the river we passed the two expedition huts used by Joan’s team . In the picture are Mike Wylde and Tunis Keenan, two Royal Society Primary Teacher Fellows being hosted by GNS Science this year.   After following a rough track through the bush, we reached the Mangahouanga Stream. In several of the large boulders we could see bone remnants. In this picture there is a large vertebra (backbone segment) of an unknown species of reptile. If you look carefully at the top of the rock in the right foreground you might see an oval shaped brown lump which is another similar vertebra. Here John Simes (GNS Science palaeontology collections manager) and Pete Shaw (forestry manager) check out a rock slab containing shells, sharks teeth and fish bones. Have a look at our video of fossil hunting in Mangahouanga Stream:

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