Fossils

Tracking Dinosaurs in NW Nelson

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Greg Browne. Image Julian Thomson @ GNS Science In New Zealand there is only one area (with six individual locations not far from each other) in which dinosaur footprints have been identified. This is in NW Nelson in the South Island. They were discovered and researched by Greg Browne, a sedimentologist at GNS Science who has spent many years doing geological fieldwork in the area. The first announcement of their discovery was in 2009 as shown in this video. Dinosaur footprints near Rovereto, Italy. Image J Thomson When compared to the easily recognisable dinosaur trails that are found in other parts of the world, the structures that have been classified as footprints in New Zealand are not initially obvious.  The photo shows an example from near Rovereto in northern Italy where each footprint is about 30 cm across. Image Julian Thomson @ GNS Science In comparison, the New Zealand examples are irregular in shape and position. It took a lot of research and a process of elimination to be certain that these structures are indeed trace fossils of dinosaurs, rather than originating from another biological or mechanical cause..  In order to be able to point at a dinosaur origin for these impressions, there are several factors that have to be considered. As a starting point we can look at horses on a modern beach: Image: Van der Lingen, G.J. & Andrews, P.B This photo was taken by researchers who investigated horse hoof marks that were imprinted on a beach sand in New Zealand (from van der Lingen, G.J. & Andrews, P.B. 1979, Journal of Sedimentary Petrology). They carefully cut a vertical slice through the imprint to study the details of how the horizontal layers of sand were deformed by the weight of the passing animal. The hand lens shows the scale: Base image: Van der Lingen, G.J. & Andrews, P.B There are essentially three ways in which the original sediment has been affected:(A) – Jumbled particles and blocks of sand have  fallen into the depression made by the footprint.(B) The footprint has a clear vertical margin on either side(C) The sediment underlying the footprint has been compressed downwards.   It is most likely that these horse footprints were soon eroded after their formation in the late seventies, due to tides, storms, wind or even the action of shore creatures such as crabs, worms or shellfish. On the other hand, there is a small possibility that they were  preserved quickly beneath a new layer of sand and are still intact beneath this protective covering. Base image: Van der Lingen, G.J. & Andrews, P.B Over geological time, sediments such as these can become buried deeply, compressed into solid rock and later revealed by uplift and erosion at the modern land surface. In the case of the horse footprint, its appearence on the surface (in 2 dimensions)  would then depend on the amount and angle of erosion. For example, if it is were eroded near to the top of the footprint (the level of line 1 in the photo) it would appear relatively large compared to if the erosion had removed most of the material, and only the lower part of the footprint were showing (line 2). Similarly if a vertical section of the footprint were to  be exposed, its size and appearance would differ depending on whether the section that was revealed represented the centre of the footprint (3) or its edge (4). Image Greg Browne @ GNS Science Here is an example of one of the footprints that Greg identified in the Upper Cretaceous rocks of Nelson. It shows similar features in cross section to the horse footprint (at approximately the same scale)- the infilling (A), the distinct margin (B) and the compressed underlying layers (C). Image Greg Browne @ GNS Science Here is another example of a vertical slice through a footprint, with the dotted line highlighting the distinct margin of the structure: Julian Thomson @ GNS Science This photo shows a footprint eroded horizontally. The heel has cut a sharp edge into the sediment at the back end of the feature (lower left), while the front has been compressed into ridges as the foot tipped forwards during locomotion (near finger).   Having confirmed these features as footprints being preserved in sediment from an intertidal environment, the question then arises as to whether animals other than dinosaurs could have made them. Having tackled this question over many years, Greg Browne worked through the following possible examples and discounted them for the reasons given:  Fish feeding or resting traces: depth of penetration and lack of deformed strata below. Amphibian foot prints: unlikely to have an amphibian large enough. Bird foot prints: bird would have to be large and heavy. Mammals: the only pre-Pleistocene mammals known from New Zealand are Early Miocene mouse-like fossils. Evidence throughout the world indicates that Cretaceous mammals were small, and did not develop into large animals until after the end of the Cretaceous extinction event and the demise of the dinosaurs. Reptile foot prints: dinosaurs: only dinosaurs would be of sufficient size and weight to have generated these deformed point source compression structures. Recently, with funding from the Unlocking Curious Minds Fund of the Ministry for Business, Innovation and Employment (MBIE), a team from GNS Science were assisted by teachers and students of Collingwood Area School, to clean up a large rock slab in the search for more dinosaur footprints. With a lot of hard work, involving cleaning mudoff the rocks with buckets of water, brooms and shovels, some hitherto unseen dinosaur footprints were revealed for the first time since the Cretaceous Period, about 70 million years ago. Here are some quotes from our assistants:“It was a wonderful once-in-a-lifetime opportunity to work with a team of scientists and look at a real dinosaur footprints.” “It was an honor and very humbling knowing that we were the first people to see these footprints in 70,000,000 years.” “It was an incredible opportunity. We were able to work alongside

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Global Catastophe in a thin rock layer

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K-Pg boundary layer – when the Earth changed forever The K-Pg Boundary (or Cretaceous Paleogene boundary, or K-T boundary as it is still sometimes called) is a layer in the Earth’s crust that marks a very dramatic moment in the history of life on earth about 65 million years ago. There is a huge change in the fossil communities of plants and animals across this boundary. Over half the species that are found in Cretaceous rocks are missing from the younger Paleogene rocks above them. Included amongst the creatures that vanished forever at this precise point in time are the ammonites, large marine reptiles (such as mosasaurs and plesiosaurs), large flying reptiles and of course the dinosaurs. New Zealand has a unique record of the K-Pg boundary. These eight localities in the northern South Island provide the only Southern Hemisphere record of how the catastrophe affected land plants (Moody Creek Mine) and marine life (Waipara River and six localities in near Blenheim).   An artists image of the impact by Don Davis of NASA The now well established explanation for this dramatic crisis in the history of life is that an asteroid, about 10 km across, struck the earth near Mexico, causing a huge tsunami and a global dust cloud that darkened the skies worldwide for months, thus killing plant and animal life. After a period of recovery that lasted several thousand years, the remaining plants and animals were able to diversify into the ecological niches made vacant by this mass extinction. Mammals were one of the groups that flourished and ultimately gave rise to humans.  The dark line of the K-Pg boundary at Chancet Rocks Recently I joined a group of scientists visiting several sites in Canterbury and Marlborough, where the K-Pg boundary is exposed. K-Pg boundary at Chancet Rocks centre left of photo At Chancet Rocks, just north of Ward Beach, the light coloured Cretaceous limestone contrasts with the darker grey Paleocene rocks on the right side of the photo. These rocks were laid down in several hundred metres of sea water, and the fossils found within them are mostly microscopic unicellular plants and animals. These have been studied in detail and are very different assemblages. This slab cut through a section of K-Pg boundary by John Simes and Chris Hollis was taken from the coast south of Chancet Rocks. If you click on the image to enlarge it you can see some of the features in more detail. You can see the thin layer of clay that precisely marks the boundary itself. This layer has been found at sites around the world, including drill cores from the ocean floor, and is remarkable for containing high levels of an element called iridium. Iridium is common in asteroids and its abundance at the boundary was a key part of the evidence that lead to the asteroid impact theory. We also visited Woodside Creek, the first K-Pg boundary locality in New Zealand that was found to be enriched in iridium. Here you can see that the river was quite high, making access a little bit difficult. This is the Woodside Creek section. It has been sampled a lot over the years so that quite a lot of the rock has been mined away. The drill holes you can see in the rock layers on either side of the boundary itself show where scientists took samples for the analyses that led to the discovery of iridium enrichment. The image at the top of this page was taken from here. This is a close up view of the very top surface of the Cretaceous at Woodside Creek, just beneath the iridium rich boundary clay. The masses of tiny pock marks in this surface are thought to have been caused by droplets of glassy impact ejecta raining down onto the sea floor from high in the atmosphere after the impact thousands of kilometres away. Chris Hollis at GNS Science has done very detailed studies of the Cretaceous and Paleogene rocks in New Zealand. He is a paleontologist who specialises in tiny microfossils called Radiolarians. Radiolarians are marine plankton that construct complex shells of glass (opaline silica); each species has a distinctly different shell. Radiolarians are one group of organism that didn’t go extinct at the K/Pg boundary. Instead, some species became very rare, while new species evolved and flourished.  These microfossil changes are clearly shown in rock samples from the K/Pg section at Flaxbourne River, where over the distance of a few millimetres one group of radiolarians (nassellarians) are almost completely replaced by another group (spumellarians). This change is thought be a consequence of rapid cooling of the ocean waters around New Zealand. In this video Chris tells us about the Woodside Creek K-Pg boundary section:

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Waihi Beach Taranaki

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The South Coast of Taranaki near Hawera has extensive rocky beaches lined by high crumbling cliffs. It is a great place for geology, but you should be wary of the potential for cliff falls, especially after rain. This is the view east from the Ohawe beach access point. A first look at the cliff from a safe distance shows that it is made of two main rock types; massive grey muddy sandstone at the bottom, with darker brown soft stratified layers above. The boundary between the two layers is very distinct and can be seen for many kilometres along the coastline. If you take a closer look at some of the muddy sandstone boulders lying on the beach, you can find some nice fossils such as this scallop. In places these rocks are very bioturbated. In other words they have been churned up by organisms that burrowed through them when they were part of the sea floor. For a close up look at the boundary between the two layers that form these cliffs, a good place to go is the beach access track 4.5 kilometres east at Waihi Beach (end of Denby Road see www.geotrips.org.nz/trip.html?id=55 for location and geological info). There, right before you reach the beach, is an easily accessible outcrop where you approach the boundary safely.   Here is a slightly closer view – you can see the change from the lower grey unit containing oysters and scallops with the shell rich layers above. The fossils in the lower unit indicate an environment of deposition about 20 to 50 metres deep. This layer is approximately 3.5 million years old. Here is another image where can see the incredibly abrupt change from the lower muddy sandstone to a much looser sandstone packed with shells. Just below the boundary there are some vertically positioned shells in a line. These have burrowed down into the sediment from above and have been preserved in life position. Although they are found within the 3.5 million year old sandstone, they are actually only as old as the overlying shelly layer, which is about 125 000 years old . This means that the 3.5 million year sea floor sediment has been uplifted, eroded down to sea level, and then covered with shelly beach or estuarine deposits of much younger age. Nearly three and a half million years are missing from the sequence. Interestingly the same unconformity is widespread across Taranaki. Here you can see it at Wai-iti Beach on the north coast. Here the time gap is even greater, as the underlying grey sediments are about 8 million years old and represent deposition at about 500 metres water depth. This shows that there has been greater uplift and erosion in the north compared to the south Taranaki coast.Here is a video of Kyle Bland explaining the Waihi outcrop and the story revealed by fossils:

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Airedale Reef

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Earlier this week I was up in Taranaki, exploring the geology of the area  with two GNS Science researchers Kyle Bland and Richard Levy. One of the sites we visited was Airedale Reef, a short walk east along the coast from the mouth of the Waitara River. There are spectacular remnants of an ancient forest on the shore platform at low tide, with tree stumps in growth position and large logs sitting in a black layer of peaty soil. The forest layer reappears at the base of the nearby sea cliffs, with the roots and tree stumps gradually being eroded out. Just below the dark layer is an olive green bed of dune sands. The carbon rich forest layer is thickest in the depressions between the dunes. This  is one of the tree stumps emerging  from the cliff. But how long ago was this forest still living? How did it die and why was it preserved like this? The answers are in the layer just above it. This overlying layer is made of an unsorted mixture of different boulders and less coarse particles of rock. You can also find chunks of carbonaceous material scattered within the layer that must have been ripped up into it as it was emplaced. This 4 metre  thick layer of material has been mapped  over a minimum area of 255 km2 around north Taranaki, and has a total volume of at least 3.6 km3. It is believed that Mount Egmont (Taranaki) volcano is the source of this layer. Like some of our other andesitic volcanoes, Mount Egmont is made up of layers of unconsolidated volcanic deposits interbedded with more massive lava flows. Because the slope angle of the volcano is very steep, the cone is inherently unstable, resulting in occasional enormous avalanches of debris launching down the mountainside, spreading across the surrounding countryside and out into the sea for distances of up to 40 km from the source. For this reason Egmont is a significant geological hazard that is monitored by GeoNet. On our visit up the  mountain the following day, amidst the lava flows and ash layers we could see deposits such as these – not too different from the bouldery layer at Airedale Reef, although likely to be much younger. Back at Airedale Reef this photo shows a good view of  the layer that buried and destroyed the fossil forest. It is known as the Okawa debris avalanche deposit and has been dated at about 100 000 years old. This means the forest was growing during the last interglacial period. Pollen analyses shows a dense podocarp forest, but lacking specifically coastal plants. It seems that when the forest was alive, the coast was further out than its present position. Rimu Pollen  (Dacrydium cupressum) 43 microns across There is a lot of pollen preserved in the Airedale Reef cliff section. Scientists found over 10,000 pollen grains per cm3 in places.They were analysed to study the plant communities from the period of time represented by these layers. Cyathea treefern spore, diameter 30 microns  This allows research into climate variations through time, as different species appear and disappear up through the cliff section from the base to the top. The Rimu and tree fern species in these two images indicate a lush podocarp forest that grew in warm, wet conditions. In the next layer above, the species found represent a sub-alpine shrubland community that grew in a cooler climate. In this photo you can see two pale coloured tephra (volcanic ash) layers near the top of the carbon rich layer, showing periodic eruptive activity from the volcano. In the last image you can see that another carbon rich layer formed in a depression at the top of the Okawa Formation (centre left). Above that the rest of the section is made up of orange and pale brown soils.

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Fossil Favourites from GNS Scientists

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GNS Science recently produced a new “Photographic Guide to Fossils of New Zealand”. It is a small, pocket sized booklet, packed with photos and information about many of our characteristic fossils. It also contains a very readable introduction to New Zealand geology, the fossilisation process and the geological history of New Zealand. You can find more information about the book, including how to get hold of a copy; here. It is published by New Holland Publishers. Here is the team that created the guide, from left to right: James Crampton, Marianna Terezow, Alan Beu, Liz Kennedy and Hamish Campbell. I asked each of them to choose their favourite image from the book and say a few words about it. Here are their comments: James Crampton: Cretaceous ammonite, scalebar is 1cm My favourite fossil is the small Cretaceous ammonite on the bottom of page 62.  Ammonites are very rare in New Zealand Cretaceous rocks, although they are extremely common in other parts of the world.  This one came from the coastline of Raukumara Peninsula, north of Gisborne, from a lovely, wind-swept, wild, and pohutakawa-lined rocky shore.  This specimen is well preserved and shows how some species deviated from the typical, simple, flat spiral shell form of most ammonites – in this case, as the animal grew, the shell became partially uncoiled to end up looking like a hook.  In life, the animal had many tentacles and extended out of an opening in the shell at the point where the label is fixed (this opening is now filled with rock).  This ammonite was found with many fossils of strange clams that were specialised to live on deep-sea seeps – places where methane was naturally bubbling out of the sea-floor during the Cretaceous Period.  These clams probably ate bacteria that, in turn, survived by using chemical reactions to ‘feed’ on the methane. Fossil shells from Hakateramea, New Zealand Marianna Terezow My favourite photo is the one that resides on the title page. It’s an image of a late Oligocene-Miocene limestone block from Hakateramea, South Canterbury. I love this photograph because it showcases some of the great variety of marine life-forms found throughout New Zealand’s fossil record. From small filter-feeders like the clam Limopsis to the large, carnivorous snails such as Magnatica, this image is a snap-shot of a once-living, thriving marine community. I find these life stories of community dynamics that fossils tell us very fascinating. Struthiolaria frazeri – scalebar is 1cm Alan Beu My favourite image is Struthiolaria frazeri, on page 122. This is the largest, most spectacular and most elaborately sculptured of the “ostrich foot shells”, family Struthiolariidae, which are almost entirely limited to New Zealand, and are one of the really characteristic elements of our fauna. They display a long, complicated history of evolution and extinction, with more than 35 species occurring as fossils over more than 40 million years, and yet only two species still live here now – Struthiolaria papulosa (top of p. 123) and Pelicaria vermis (p. 123, lower on the page). Struthiolaria frazeri provides a clear example of extinction, as it is a key fossil for identifying the end of the Nukumaruan Stage, becoming extinct suddenly 1.6 million years ago, at a cooling spell.  Presumably it was a warm-water species, as it is mainly found in shallow-water rocks in central and northern Hawke’s Bay, with a few specimens found near Whanganui. The very obvious sculpture of prominent, square-section spiral ribs, the tall spire, and the short, oval aperture with thick, smooth lips and a deep sinus in the top of the outer lip make it easy to identify. Cretaceous broadleaf – scalebar is 5cm Liz Kennedy My favourite image is of an undescribed Cretaceous broadleaf angiosperm leaf base and podocarp foliage on page 54. These beautiful leaf impressions, along with many other leaf specimens, came from very hard grey sandstone overlying a thick coal seam which was mined at the Strongman Mine opencast near Greymouth. They are a glimpse of the vegetation which made up New Zealand’s Late Cretaceous forests which were very different to those of today, a time when dinosaurs still wandered about, perhaps even eating this kind of angiosperm leaf. These leaf impressions are generally well-preserved, with the ridges of prominent veins providing texture to the impressions. An assemblage of leaves such as these can provide us with a fascinating picture of the past including what kinds of plants covered the Late Cretaceous New Zealand landscape, how diverse the vegetation was and what the climate was like when the plants were growing. Historic fossil locality in the Chatham Islands Hamish Campbell: “My favourite image is on p.25. It captures not only fossils but also a ‘fossil moment’. After all, photographs are fossils of a kind…preserving a record of things that happened long ago. This beach on the north coast of Chatham Island is famous because this locality, with fossil oysters that are 50 to 55 million years old, is the very first fossil locality to be formally recorded in the scientific literature from New Zealand. It was collected by Ernst Dieffenbach in 1839 and he sent the fossils to the Natural History Museum in London. Oddly enough, this locality was ‘lost’ for more than a century because it was buried beneath a sand dune. It was only rediscovered by us paleontologists at the time of this photograph in 1995.”

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Fossil Whale Hunting

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Last weekend I returned  to our fossil whale locality in Palliser Bay with John Simes, the paleontology collections manager at GNS Science. This is where I had found three large jaw bone fragments of a fossil baleen whale last November. We decided to have a good look through some of the loose debris in the area where I had already made some finds.After some time. John spotted another large piece of mandible, very similar to the ones that we had from the previous visit. I decided to try the direct route up the cliff, to get closer to the source of the bones. The ice axe proved to be quite useful for making progress up   the very crumbly mudstone. This got me about half way up the gully, to a point that I had reached last time and where I had found one of the three original bones. On this first re-inspection I didn’t come up with any more fossils. The next plan was to abseil down into the gully from the top, in order to have a very close look at the steep headwall which seems to be the actual source of the fossil whale. I had to take care not to dislodge any large rocks with the rope. Unfortunately this inspection of the cliff didn’t reveal anything even with careful scrutiny. Back in the bed of the gully, I dug around with my ice axe some more and did at last come up with three smaller pieces of bone. Here you can see one of them – we think it is the end of a jaw bone, although it is much thinner than the other pieces. Back in the macropaleontology lab at GNS Science, the thin layer of mudstone coating the bones was quite easily cleaned away with the help of a pneumatic air scribe. The 30 cm long piece shown here turns out to fit perfectly with the previously found  segments of the mandible, giving us a combined total length of 1.5 metres for it. The missing link puts it all together. The latest piece in the puzzle is second from right. The rest were found on the previous trip. Here are the smaller pieces after a bit of cleaning. It is tantalising to think that there must be a lot more of them waiting to be discovered in the mudstone of Palliser Bay.

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Titahi Bay Geology

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Titahi Bay is a great place to visit if you are interested to see some of the geology near Wellington. There are a number of very interesting features to look at and explore. The first thing to check out is the coastal landforms caused by a combination of the atmosphere and  the sea, as well as the variable resistance of the rock, and a history of earthquakes (uplift). The first image is taken from the Pa site, a few hundred metres north of Titahi Bay beach. If you are a teacher, this is an excellent place to encourage your students to observe some of these natural features, such as sea caves, sea stacks, arches, marine terraces and wave-cut platforms. There is more information about how these features form on coastlines generally on the GNS Science websiteYou can also have a look at this GeoTrips page for specific information if you would like to visit this area. This sea cave marks the line of weakness of a fault. It is no longer at sea level, having been uplifted out of range of the water by earthquakes. It is also a useful way through the rocks between two small embayments. A striking feature of some of the rocks at Titahi Bay is this type of weathering out of the spaces between joints to form distinctive criss cross box structures Having looked at the erosion and weathering features along the coast, the next thing to do is have a look at the structures and the rocks themselves. A good place for this is just south of the Pa site, accessed down a short very steep track from Terrace Road. www.geotrips.org.nz/trip.html?id=69 In this photo you can see that the rocks are made up of alternating bands of massive sandstone, with in-between layers of dark mudstone. These rocks were formed from sands and muds eroded from the margin of Gondwanaland, long before New Zealand existed. The material flowed down into the deep sea and settled over wide areas. The coarser sediment, at the base of each of these submarine landslides, is represented by the sandstone, whilst the mudstone gradually settled on top.After deposition, the sediments were squeezed and deformed by the bulldozing effect of plate collision along the edge of Gondwanaland. You can see how the originally horizontal layers are now  almost vertical at Titahi Bay. Many faults are easy to spot, as they displace the clearly defined rock layers.As well as faults there are also folds in the rocks such as the anticline (upfold) shown here. An interesting challenge is to look for sedimentary features such as graded bedding or cross bedding, in order to tell the direction of younging of the steeply tilted rocks.  In this photo you can see some cross bedding, showing where the rock above my finger cuts across some fine layers that must have been layed down first. If you have time whilst at Titahi Bay, and if the tide is out, you should have a look at the tree stumps of the fossil forest which are sometimes exposed, usually at the south end of the beach. It seems almost unbelievable that these wooden stumps date from a time before the last ice age, about 100 000 years ago. The fossil forest does actually extend right along the beach, but is mostly covered with sand. On rare occasions, about once a decade, storms clear the sand away to expose much more of the forest than you can see here.Look carefully and you can see the growth lines of these ancient tree stumps. Check out the GeoTrip location here: www.geotrips.org.nz/trip.html?id=32https://youtu.be/A2Jed7P-pQ0

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A dynamic landscape in Hawkes Bay

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Last week I was in Hawkes Bay with geologist Kyle Bland, who led a field trip for teachers, students and parents of Crownthorpe School. Hawkes Bay geology is a story of uplift along fault lines, combined with rapid erosion and deposition by rivers flowing from the inland mountain ranges. This story is etched into the geomorphology of the landscape. The Mohaka fault last ruptured between AD 1600 and 1850, and forms an amazingly straight scar across the landscape. Like many faults in New Zealand, it is an oblique strike slip fault, including both sideways and vertical movement.  If you click on the image to enlarge it you can see how streams crossing the fault have been offset by sideways movement from the last rupture. Combined sedimentation, uplift and erosion have produced stepped terraces alongside the Ngaruroro river flowing from the Ruahine range out towards the coast. There are many fossils to be found in the sedimentary rocks that have been uplifted and exposed. Fossil hunting Hawkes Bay style involves using a digger to get access to your specimens! Ancient greywacke sediments are exposed in the Ruahine Range, having been uplifted by tectonic movements of the North Island fault system (Mohaka and Ruahine faults). These rocks were deposited in a trough at the edge of Gondwanaland, long before New Zealand ever existed. In the video below, Kyle gives us a Hawkes Bay case study of landscape evolution.

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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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Cape Kidnappers

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Cape Kidnappers and the Clifton Cliffs make for a spectacular geological site in Hawkes Bay. The cliffs extend for several kilometres southwards from Clifton, on the coast near Hastings. They  are very high and consist of quite loose rocks, so it is important not to go too close where possible. It is also important to start your visit on a falling tide which will give enough time for a return trip without being cut off by high water. At the start, near Clifton, the cliffs are made up of thick river gravels, with thin layers of white pumice (volcanic ash) and occasional dark layers of plant material.  Initially the beds are about 300 000 years old. Because they are dipping gently down to the north, you will pass further and further down the sequence as you walk along the beach to the south.and east. Here you can see the fluted erosion of the unconsolidated gravels caused by rainwater. In this photo, a layer of light coloured volcanic ash separates overlying river gravels from marine mudstones below. Just above the ash is a very thin dark organic layer with plant remains in it. There are many pale coloured ash layers in the sequence. They have been erupted from the Taupo Volcanic Zone in  the Central North Island, at least 150 kms away. The thickness of the layers even at this distance, testifies to the magnitude and violence of these past rhyolitic eruptions. In this photo you can also see how a fault has dislocated the beds by several metres. Further along the beach, towards Black Reef, there is a distinct change in the bedding, seen in this image about half way up the cliff. The lower gently dipping beds have been eroded flat with much younger beds deposited on top of them. This unconformity represents a time gap of about two and a half million years. The lower unit is three and a half million years old – the upper one starts at about 1 million. An exciting find on our visit was this fossil whalebone. It extended through the boulder for about one metre. Out on the reef itself were some well preserved shell fossils as well as another orange coloured whalebone fossil slowly being eroded away. Last but not least I should mention the gannets, for which Cape Kidnappers is most famous. The young birds here will take their first flight soon, and without looking back or touching down will travel all the way to Australia. Cape Kidnappers features on our GeoTrips website where you can also find lots of other locations to explore geology and landforms: www.geotrips.org.nz/trip.html?id=182

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