Saturday, August 29, 2015

Summer adventures, part 3: a visit to Santa Cruz

In June Sarah and I visited Santa Cruz two days in a row, and found quite a bit down there - here's  brief "slideshow" of some of what we saw, paleontological and otherwise.


Carcharodon hastalis tooth collected by Sarah from the lower Purisima Formation; teeth from this spot are often missing the root.


Pigeon guillemots roosting in exposures of the Santa Cruz Mudstone near Natural Bridges State Beach - one of the best sightings I've had of these guys!

 
Pigeon guillemot coming in for a landing over Monterey Bay.

 
Pigeon guillemots are members of the family Alcidae, the group including murres, auks, and puffins.


A medium-sized sperm whale tooth from the Purisima Formation! I was particularly happy about this find.


A skull of "Balaenoptera" portisi, from the Purisima Formation and on display below the mounted blue whale at the Long Marine Lab in Santa Cruz.

 
The remains of the middle of a balaenopterid (rorqual) skull destroyed when somebody inadvertently chopped through it cutting surfer's stairs into the cliffs.

 
Beautiful view of the Santa Cruz coastline.

 
Bonebed 5 from my master's thesis/PLoS One article, showing fissure fill in a large burrow likely formed by a large boring pholad clam.


In Capitola there is an entire retaining wall constructed from blocks of concretions from the beach (mostly bonebed 6 of my PLoS One paper), but in one spot a caudal vertebra of a baleen whale was carefully chosen to be placed as a building stone...
 
 
At Capitola, beautiful invertebrates are exposed - hundreds of thousands of shells - including these large cockles, Clinocardium meekianum.

 
Here's a smaller nodule containing a collection of partially associated/articulated Clinocardium meekianum.

 
Elsewhere shellbeds are not quite so concreted - here sandy bottom bivalves (Anadara, Macoma) form beautiful lenses, pavements, and stringers within beautifully colored "blue sandstones".

 
But vertebrates are what I really care about! Here's a nice lumbar vertebra of a dolphin, in a large chunk of concretion that makes it not worth the effort to haul it off the beach.


I first spotted this skull in 2009, and after three years of erosion while living in New Zealand I can finally identify it as the tip of a baleen whale palate - possibly Herpetocetus.


And here's a small balaenopterid whale skull which I first spotted back in 2002. We're looking at the bottom of the skull...


...and here's a closeup of the auditory bones, in particular the curly looking orange element, which is the tympanic bulla. It's possible that this is an early gray whale, but unless the impossibly hard matrix was cleaned off (after removal of the impossibly heavy block, of course) we'll probably never know.


This is for certain a new Herpetocetus skull - mostly embedded in impossibly hard concretionary matrix.


And this is also a Herpetocetus braincase, one which I first came across back in 2008 or so while on a visit with Sarah (girlfriend at the time).

 
Ten years later, and she's still sleeping on the job.

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.




Sunday, July 26, 2015

Summer adventures, part 1: Halfmoon Bay field recon

 I've got quite a bit to catch up on from this summer - I've been busy (too busy, in fact). So, here's a selection of photos from the first part of our vacation back in the USA. We didn't waste much time heading back out to some choice localities in Halfmoon Bay. However, the drought and lack of erosion/storms has really taken its toll on local fossil sites, and as a result the beaches are high and the fossils hidden under a year's worth of dust and grime.


Sarah had a bit of a spill on the way down to the beach - in one gulley there was a thin layer of sand overlying (and hiding) a thicker layer of mud, which she jumped down onto from a log.


A Clinocardium cockle peeking out from the sand.


A pretty fragment of bull kelp sitting on the beach.


Several years ago I spotted this huge thing weathering out of the cliff about 25 feet above the beach. I got a better photograph of it in the field, and finally figured out what it is. I always knew it was some sort of a huge cetacean skull, probably baleen whale, but couldn't make heads or tails out of its shape.


Here's a marked up version of the photo. This clearly shows that it's the posterior end of an upside-down baleen whale braincase- likely a balaenopterid whale - poking out, with some of the left braincase broken away and missing. The condyles, foramen magnum, right exoccipital, and even a tympanic bulla are evident. Judging from how far up this is, the skull is well over a meter wide, putting it somewhere in the size range of a Sei whale (Balaenoptera borealis). This specimen is a bit of a heartbreaker, because it would be impractical - if not impossible - to safely collect. People have seen this photo and suggested ropes, scaffolding, jackhammers, and all sorts of wild ideas but the simple truth is 1) digging that far in would likely trigger a cliff collapse and 2) far more easily collectable specimens are waiting to be collected on other beaches, without the need of all sorts of equipment I don't have the training or funding to operate.


This hole was dug five years ago by my field assistant/fossil buddy Chris Pirrone (attorney at law), and yielded a beautiful little "river" dolphin skull with a partial rostrum, mandible, and left and right tympanoperiotics which I referred to Parapontoporia sternbergi in my 2013 Geodiversitas paper.


Gooseneck barnacles and a single mussel poking out.


A piddock clam whose rocky home is being eroded more quickly than it can bore, beautifully showing how it forms boreholes.


A large green anemone lightly dusted with sand from the last high tide, within a shallow sandy tidepool.
 

View of the dramatic cliffs of Purisima Formation at the northern side of Tunitas Beach - one of the most scenic beaches in Halfmoon Bay, if not also one of the dirtiest; it's difficult to get to, and most people who go there to have barbecues and drink leave all of their trash in kind of a big heap at the bottom of the trail.


Stay classy, Halfmoon Bay.


Vertebrate fossils here are rare - this was my first discovery - a couple of associated dolphin vertebrae. The rock was far too hard to even think about removing them.


Invertebrates are not rare, however, and clusters of the slipper shell Crepidula princeps are quite common, such as this rather nice example.


The Purisima Formation here reflects deeper shelf sedimentation, and the traces can be quite large; here's a medium-sized Teichichnus trace. Elsewhere in the Purisima Formation Teichichnus traces can exceed 1 meter diameter (!) and approach 2 meters (!!!).


Here's a thalassinidean shrimp claw, complete with the dactyl and chela.


My wife hard on the search for fossils.