Palliser Bay

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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Fossil Whale

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Last week I visited Palliser Bay in the Wairarapa. Along the coastline there are many exposures of mudstone from the Hurupi Formation, about 11 to 8 million years old. These mudstones contain abundant marine shell fossils, but are also known for occasional whale bones.  After some time searching, as luck would have it, I found a large piece of bone sticking out of the mud near the base of one of the cliffs. The bone was embedded in soft sediment and was easy to remove with a bit of digging. Nearby I found two other large pieces. Back at GNS, Craig Jones identified them as fragments of mandible (jawbone) from a large baleen whale species. Two of the pieces matched together to give a combined length of 75 cms. Initially we thought that these are part of the left mandible, whilst the other single piece is part of the right mandible.    John Simes is the manager of the fossil collection at GNS Science. He  helped me to give them an initial clean to remove some of the mud that coated the bones. Here you can see the typical mottled texture and brown colour of fossil bone. This is the largest  piece, half a metre long and about 25 cms across. There is an epifauna of bivalve and barnacle fossils attached to the bones. This tells us that they would have been lying in calm, relatively shallow water before they were buried by sediment. There are also several wood fragments in the surrounding clay, which suggests that the whale died not far from land. After many hours of cleaning, some interesting grooves appeared in the bones. These show where blood vessels were embedded alongside the bone. For an update on additional whale bone discoveries from this locality check out this blog post.

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Palliser Bay

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Palliser Bay is an isolated sweep of coastline about 2 hours drive from Wellington. It is separated from New Zealand’s busy capital city by the Rimutaka Range. Yesterday I visited the area with a group of Lower Hutt school children as part of their Year Seven geology camp. Fully armed with the “Kiwi Fossils Hunter’s Guide” as well as another excellent book by Lloyd Homer and Phil Moore that describes the geological features of the Wairarapa Coast called “Reading the Rocks“, we visited several great geology hotspots along the coastline. A striking feature that we noticed straight away was the flat topped escarpment that runs along much of the coast. This is a raised marine terrace that was at sea level about 80 000 years ago. It indicates that the whole area has been undergoing an enormous amount of uplift which continues to this day. First stop was Hurupi Stream. (This is described in detail in the “Kiwi Fossils Hunter’s Guide“). The soft mudstones at the sides of the stream were deposited under the sea in the Miocene Epoch (sometime between 11 and 7 million years ago) , when the Aorangi Range just to the North was an island, separated from other parts of the North Island by a shallow sea. We found quite a few marine molluscs that are very well preserved and easily spotted. Not far along the coast road are the Putangirua Pinnacles. These spectacular features have been eroded out of a thick sequence of conglomerate. Hard layers or large individual boulders within the conglomerate form a protective cap at the tip of each pinnacle. The ground is strewn with loose rubble – testament to the fact that the erosion here is still very active. This might not be the best place to visit in a rainstorm! A few kilometers along the coast road, there is a dramatic example of coastal erosion where a whole section of the original road itself has disappeared! We followed the coast past the small settlement of Ngawi, and a huge tilted slab of fossiliferous sandsone called Kupe’s Sail, to the Cape Palliser lighthouse. This is built on a cliff of volcanic rock that was erupted under the sea as pillow lavas about 100 million years ago. The long staircase up to the lighthouse leads up to a great viewpoint. This is the Southeastern tip of the North Island of New Zealand, with nothing but ocean between here and Antarctica or South America. Just a few kilometres out to sea is the Hikurangi Trench, the collision boundary between the Pacific and Australian tectonic plates. The connection between uplifted terraces, fossils, erosion, earthquakes and volcanoes gave us all something to think about to round off our geological excursion.

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