Sunday, August 9, 2015

Summer adventures, part 2: return to Point Reyes

Before leaving New Zealand, I made sure to submit another permit application to the US National Park Service to continue fieldwork within Point Reyes National Seashore. Guilty admission: I remembered to start work on a permit application when I saw in the news that one hiker died and a second hiker was seriously injured in a cliff collapse at Arch Rock in southern Point Reyes. Sarah and I made it up to Point Reyes a few times - here's some photos from our fieldwork in May and early June, including the excavation of our most exciting find - a partial skeleton of a small dolphin or porpoise, including a complete skull.


Sarah and the NPS paleo intern Lillian Pearson walking along the shore of Drake's Estero.


One of exactly two sea cow fossils I've seen at Point Reyes - this is a huge concretion with some enormous ribs, clearly identifiable as a sea cow rather than a baleen whale by their oval, inflated cross section (cetacean ribs are typically flattened distally and quadrate or rhomboidal proximally) and their complete lack of a marrow cavity. The second specimen is a petrosal I collected nearby (fortunately, not in a concretion).


A stitched view of the broken concretion with the ribs sticking out.


Lillian (red) and Sarah (blue) walking along a hill at Point Reyes.


We had some adorable company.


Lillian was at Point Reyes all summer doing a pilot project as part of a GeoCorps internship with NPS, surveying fossil sites along the coast in order to assess which cliffs would be best to monitor for a paleontological monitoring project. As part of this, she found these three associated baleen whale vertebrae. These apparently all belong to the same individual, but weathered out in a low-energy setting and the bones weren't scattered by currents after being eroded out.


Lillian with her vertebrae.


All three vertebrae were also dorsoventrally flattened - rare for Purisima Formation marine mammals, given how sandy the unit typically is. At Point Reyes, it is typically more muddy than in Santa Cruz and Halfmoon Bay, but compaction of bones like this is still unusual. All three showed this, further supporting identification as the same specimen. However, no skull or mandible parts were found, so we decided to leave it. We were also really, really exhausted, and hungry. It was also like 7:30 at night. 

 

Sarah looking for fossils, Lillian and others in the background.


A couple of weeks before flying home from New Zealand, Lillian found and photographed an interesting specimen I thought could be a nearly complete (or nearly completely eroded) odontocete (dolphin) skull. After giving a talk at the visitor center, we headed out along with UCMP's own Erica Clites (yellow) and her volunteer Kathy Zoehfeld (black).


 Sarah, Lillian, and I starting the excavation of the dolphin. As it turned out, not only did it have a complete skull - oriented parallel with the cliff for once - it had a mandible, teeth, ribs, an atlas, a humerus, several other vertebrae, and to make matters even better it was exposed with perhaps less than 10" of overburden.

We started to dig a trench around the back - and fortunately, aside from a couple of damaged ribs, the skeleton didn't continue into the cliff. It's not evident in the photo, but the way this valley behind us is set up, it channels the wind so that at this spot, there were more or less continues 30 mph winds during the entire excavation - hence the glacier goggles (a lifesaver for windy coastlines). All of our eyes were sore and red the next day from getting sandblasted.

  

Within an hour, we got our hands dirty and put a plaster jacket.

Here's Sarah and Lillian with the prize - undercut, and flipped over.


Since the wind was so damn miserable, we didn't waste any time in moving the jacket into the dunes where the wind was less extreme. It was about 6pm now, so we decided to leave the open jacket back in the dunes, cover it with driftwood, and return for it the following week with more help since we didn't really have enough time, muscle, or energy to move it (let alone finish the jacket). That also meant that we were able to leave all the burlap out there (but not the plaster, since the fog - or rain - could've made it all set).


When we got back the following week, we wasted no time in finishing the jacket. We had a game cart (furnished with car tires!) - but couldn't get it any closer than 100 m away. The jacket was still probably about 75 pounds, and on solid ground I can bear-hug it and walk a short distance - but not on sand. So, we found this large, triangular piece of flat driftwood and lashed the jacket to it. Since the plaster was not yet set (even from the week before - the foggy, cold, humid coast slows plaster setting to taking weeks or more to cure, sometimes completely prevents it) we wrapped the remaining burlap around the jacket like a burrito, and then lashed it so that the rope wouldn't slide through the outer layer of soft, damp plaster.


As it turned out, dragging it like this was easier than lifting - but still a bit of a pain. Then I got the idea to use a couple of extra ropes - an idea I had gotten from a photo published in one of Jack Horner's books, where a rancher on horseback and several fieldworkers on foot have ropes in a diamond pattern with a jacket in some sort of a tarp sling, distributing the weight and sliding it across the prairie. Lillian's a sailor, so I asked her to take a 20-30' piece of nylon cord and tie a hand-size bowline at either end; we took the middle of the rope and stuck it under the jacket. It felt like Lillian and I were doing nothing, but NPS volunteer Kent Khitikian (middle) said he basically just had to keep the plank upright and struggle to walk backwards enough to keep up with us. So, moral of the story: if you need to get a medium sized jacket out of a remote (but flat and nonetheless inaccessible) locality (like a beach!), a plank and 100' of rope and a couple of friends is all you need.


We didn't even bother taking it off the plank in order to get it up over the obstacle - a rocky point. The water was too deep to walk it around...


 ...so we lifted it up and over. It wasn't very high, but it was pretty difficult owing to how much slippery algae was growing on the rocks.


 And once we got it up and over, we were able to get it onto the game cart. It was trivial to get the jacket down the beach from here, and within fifteen minutes the jacket was a half mile down the beach and in the trunk of our car.




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