We arrived at this first locality - a lime quarry - to meet up with 3rd year student (and part time fossil preparator) Nichole Moerhouse, who was collecting data for a research project on the depositional environment of the Kokoamu Greensand and the Otekaike Limestone. The Kokoamu Greensand is early Late Oligocene in age (~30-26 Ma), and is a relatively thin richly glauconitic sandstone overlying a temporally significant unconformity, which is angular in places. It gradually transitions to the latest Oligocene-earliest Miocene Otekaike Limestone (~25 Ma), which can be 'sandy' in places, and basally contains glauconite. The Kokoamu-Otekaike section represents an overall shallowing - glauconite can only form in relatively deep environments (at least deeper than 'middle' shelf) during very slow sedimentation), and a gradual transition from slow offshore glauconite-rich deposition to inner shelf/shoreface calcareous deposition with abundantly preserved invertebrates. For those less familiar with stratigraphy and sedimentology - this is a fairly straightforward and commonly encountered type of depositional 'sequence' in marine strata, and generally represents an initial deepening of the shelf (possibly due to the continental shelf being down-dropped due to tectonic subsidence, or an increase in sea level) and subsequent filling of the basin and sediment marching out onto the shelf from the shoreline. Understanding concepts like this is crucial to paleontology, as these processes are going to affect the preservation, abundance, and three dimensional distribution of fossils within a body of rock.
Nicole and I looking at a fossil dolphin in the Otekaike Limestone - it's below Tsai's feet, who took the picture. Ewan had spotted this years before, and sent Tsai and I up to locate it. It was exposed when the original road bed to the quarry was dug out (what we're standing in), and in the time since, a lower road was dug (the trench can be seen to the upper right).
Next up: pictures from a hike into native New Zealand forest.