Now that we’ve finally arrived in Seram, we can get to the fun research parts! One of the goals of this field season was to collect multiple sediment cores from mangrove swamps along the southeast tip of Seram. All the little speckles in the shallow water shown in the Google Earth image are acres and acres of mangrove swamps.
Mangroves are highly salt-tolerant species of trees that take up rain water isotopes in predictable ways (see post #1 for further details or a refresher).
The idea was, if we can get good sediment core samples, we could reconstruct past rainfall and create climate records. This is really useful data to have when evaluating why or how something changed in the archaeological record. In order to discover if climate was a factor in those cultural changes, it turns out that having an idea of what the climate was like when those changes happened is pretty useful. The really awesome part is that if we recovered good samples and were able to reconstruct the climate record, it would be the first of its kind for Seram, and one of only a handle of climate records that exist for the Southeast Asian region. So, kind of a big deal.
What could go wrong, right?
Turns out that crocodiles have been “reported” in the swamp we wanted to core. If you haven’t guessed yet, crocodiles are kind of a running joke for this group.
Since our paleoclimate colleagues weren’t able to come into the field with us, I had been trained back in Seattle to do the coring, so I was forced to go into said swamp and help coordinate the sample collection (after I made it very clear that if they continued to threaten sacrificing me to said swamp crocodiles that I would not show others how to collect the samples).
Sample collection involved selecting a nice thicket of mangroves where lots of sediment had built up. Our coring instrument is about 0.5 meters long, so we were looking for thickets with mud and sediment with a depth of 1 meter or more. Once an area was selected, we marked a spot, inserted the coring tool into the mud, and pulled up a half-cylinder shaped tube of sediment. We photographed, bagged, and tagged it, then collected modern day leaf samples from the trees surrounding the coring site. We also measured the modern day salinity levels of the swamp. Together with the modern leaf litter, this helps us have a modern reference or baseline against which to judge any salinity and isotope changes in the different layers of the sediment sample.
In addition to the cores we collected in Seram, Joss also collected a series of sediment cores from mangrove swamps in Ujir, a island to the southeast of Seram where he is doing his dissertation research. Both sets of samples were recently radiocarbon dated and turned up exciting results! The Seram samples go as far back as 1200 BP (Before Present, uncalibrated), and the Ujir samples are as old as 3500 BP (uncalibrated). That means we have a nearly 3500 year record of Indonesian climate and rainfall patterns!
We’re currently working with Julian and our other paleoclimate colleagues to get additional dates from different layers of the sediment samples so that we have a more refined idea of climate change through time.
Without collaboration with other disciplines, in this case paleoclimatologists, we as archaeologists would not be able to access data like rainfall records, or even participate in this kind of cross-disciplinary research. Collaboration, between different disciplines, and even between archaeologists from different countries, is extremely important. Scientific research moves slowly, and field research can be a tedious, tiring process with the ever present risk of not producing useful data. When we collaborate, we increase our chances of getting better results, we are able to create bigger and better informed interpretations of the past, and we have more fun in the field!
(Also, there’s more people to choose from when deciding on who to sacrifice to the crocodile gods…)