The Waipara Greensand is a middle to late Paleocene glauconitic muddy sandstone, which contains the earliest fossil examples of penguins (Aves: Sphenisciformes) and other Paleocene marine birds in the world. Three main outcrops of the Waipara Greensand in the mid-Waipara River, Broomfield, Canterbury are known for their abundance of vertebrate fossils, Site 1, Site 2 and Site 3. Sampling has been undertaken at Site 3 by Morgans et al (2005), and the geochemistry was studied by Hollis et al. (2012) and Hollis et al. (2014), with a particular focus on organic geochemical proxies. However, the focus of these studies was on the top of the formation in what is known as the Waipawa organofacies, with less detail in the lower part of the formation. Additionally, the most productive site for vertebrate fossils is at Site 2, which has not been sampled or measured, leaving early marine bird fossils without context stratigraphically, and therefore without understanding of palaeoenvironments during the time of deposition.

Here, a detailed description of the sediments from Site 2 and Site 3 are presented. Using proxies from pXRF and biomarker data (including Glycerol Dialkyl Glycerol Tetraethers (GDGT’s), hopanes, n-alkanes, Total Organic Carbon (TOC) and bulk organic carbon δ13C), as well as field sedimentary descriptions and petrography, changes in palaeoenvironment through the mid-late Paleocene in the mid-Waipara Section at Site 2 are described. With the data collected from petrography and pXRF analysis, it is interpreted that elemental concentrations are primarily controlled by low sediment accumulation resulting in optimal conditions for glauconite diagenesis. Nutrient like elements showed a relationship to increased TOC values and productivity in the Waipawa organofacies. Increasing TOC values through stratigraphy correlate to higher BIT values and more positive δ13C values, indicate increased erosion of 13C terrestrial carbon into the marine basin during the deposition of the Waipawa organofacies. TEX86 sea surface temperature trends show warming during the deposition of the lower Waipara Greensand, followed by a trend of cooling, and then warming again in the Waipawa organofacies.

Low sediment accumulation and moderate organic content resulted in seafloor diagenetic environments that are destructive to calcareous components such as invertebrate fossils but are constructive for the formation of glauconite, dolomite, and pyrite at the seawater/sediment sub-oxic transition zone. These diagenetic conditions are also conducive for the phosphatisation of vertebrate fossils resulting in their preservation. Cooler climate, and thus calmer weather patterns, during the mid Paleocene likely contributed to the accumulation of 13C enriched organic carbon in the terrestrial setting. Increased erosion of terrestrial organic matter is correlated with an increase in SSTs in the Waipawa organofacies, suggesting increase storm intensity may be a mechanism for the deposition of the Waipawa organofacies. Nutrients adsorbed onto this terrestrial organic matter may have increased productivity, which could influence evolution of marine vertebrates in the late Paleocene.