Discoveries in Curio Bay

Tuesday, December 2, 2014
Lauren Michel

Curio Bay
Before we even set off for Antarctica, 4 of us (Erik Gulbranson, Rudy Serbet, Ignacio Escapa and myself) made a reconnaissance trip to Curio Bay, New Zealand. Curio Bay is close to the southernmost part of the south island of New Zealand and is famous for the preservation of a 180 million year old fossil forest. Because what we are studying in Antarctica is roughly time equivalent, and Antarctica and New Zealand were close together in the southern part of Pangaea during this time, we thought it would be interestingto go study the forest of Curio Bay. Then we can compare what we are seeing in Curio Bay to what we are seeing in Antarctica.

What we found was quite interesting and a great start to the field season. Many papers have described forests at Curio Bay as being in situ with some of the logs may having been transported on a river. What we realized was that the forest of Curio Bay is actually 2 or 3 separate forests, with tree stumps now preserved in silica (or chert). Imagine a tree being dunked in epoxy and solidifying: this is the type of preservation process, except in stead of epoxy it is silica (quartz) that provides the cementing agent. 

Lauren taking notes.All of the knobs sticking up are fossilized tree stump casts. This area is a preserved area by the New Zealand government, which is similar to Petrified Forest National Park in the US; you can’t take any of the tree stumps casts, but you can study them! Erik is interested in what fossil trees record and can tell us about past climate changes. One of the ways he does this is through very carefully studying the tree rings that are now preserved in silica. He can take careful measurements of the widths of the tree rings using calipers and high-resolution digital images to a number of things: (1) cross date the trees to figure out which of the trees were growing together at the same time, (2) create a long (100 years or more) timeline of wood growth year-by-year for these trees that are ~180 million years old, and (3) interpret the variation in ring width over that long timescale (100 years or more) to interpret paleoclimate. Rudy and Ignacio (Nacho) are paleobotanists and are experts in plants of this time period and the evolution of plants over geologic time; they are also excellent field geologists/paleontologists. Lauren’s specialty is the study of fossil soils (paleosols) throughout geologic time.

Since Curio Bay is tidally influenced, time was an issue. We divided up the tasks with Rudy doing reconnaissance to find the best preserved stumps. Nacho would take careful photographs that Erik can study later, Erik would measure the rings he could get to with his calipers and I would take notes. We ended the day with the best discovery of all, a rare yellow-eyed penguin. A great end to the start of our field season! - Lauren Michel and Erik Gulbranson