Day 9: Tuesday, June 14, 2005
September 21, 2005
The usual group of Al, Neil, Pam, Sarah, Whitney, Kelsey (girl) and I all set out after breakfast to check out some serpulid mounds and wrap up some final measurements at Canada Honda. We quickly finished everything we need at Canada Honda and drove to the Los Clavellinas site, arriving around lunch time. Al and Neil scouted ahead down the water cut channel while the rest of us ate lunch. After an hour of waiting for their return Sarah and I decided to go looking for them. We took our time, examining the sedimentary structures and pinching out of cervicornis while the mud beds thickened. Pam soon caught up with us. The beds were deposited in such a way, and the channel was cut in such a way so as we walked further proximal to deposition we were walking further back in time. The massive mud layers gradated into crossbedded muds, under which we found crossbedded stones. We found numerous bivalves in life position and in exceptionally good condition. Beneath our feet lay redeposited rocks from up the channel, much of which was lithified carbonate deposits.
As we continued walking up the channel there was a rapid increase in grain size. When we began walking small stones (<5cm) littered the channel bottom, while further up large stones (>15cm) were the norm, and further still we encountered boulders >1m wide. Meanwhile channel walls revealed very different bedding types than anything we had seen before, and must be from earlier events than what we are studying. Eventually lithified mud deposits with very different strike and dip were found, clearly indicating deposition during a much earlier period. We stumbled across pieces of massive coral both recent and ancient, which must have peeked Al and Neilís interest. As we continued we found an in situ ancient lithified massive reef that the channel cut right through. It was quite an experience to walk right trough these structures and see that kind of facies change.
We had been walking for over half an hour and before we caught up with Al and Neil. They had spotted serpulid worm mounds way up on a hill nearby and Neil went up to gather a GPS reading and a sample. We were clearly in an area outside the scope of the project in this channel cut and we decided to go back to our equipment and start sampling up the channel as far as we could. Neil speculated at the existence of a fault in the area producing accommodation space resulting in the huge sediment deposits.
When we got back to our equipment we found Whitney and Kelsey playing around with four young local boys. We got pictures with the boys and they got very excited being able to see their pictures on the screens of the digital cameras. We began moving up the channel cut to gather soil samples to examine for microfossil content. Whitney and Kelsey stayed behind to take soil samples of sections where coral was sampled by other group members, so the results can be compared.
That night I found out that we would be traveling to Boca Chica to go snorkelling at a living reef and learn about modern reef environments. We would leave Thursday and stay two nights.