Correlating chemical and physical signatures through the Mid-Miocene Global Cooling event in New Jersey Shallow Shelf cores (IODP Expedition 313)

The New Jersey margin is an ideal location to study the history of late Cenozoic sea level change due to a combination of rapid depositional rates, tectonic stability and a well-preserved fossil record. This project focuses on a 70 m interval of cores recovered from the New Jersey margin during IODP Expedition 313, which took place in 2009. The interval is from the most landward (M0027A) of the 3 holes cored during the Expedition and is populated by siliciclastic sediments deposited during the early- to mid-Miocene ("Unit II"). These sediments are dominated by clays and silts, although some sands are also present. Within Unit II, changes in petrophysical parameters are clear from both the downhole and core logger data. However, these changes are not apparently related to the sedimentological characteristics. Acquisition of geochemical data will be undertaken to investigate the nature and cause of these variations. Given the available information on age for Unit II, it is evident that the mid-Miocene climate transition (14.2-13.8 Ma (Shevenell et al., 2004)) occurred while sediments in this interval were being deposited. This event is one of the most significant in the Cenozoic and marks a change from the early-Miocene climate optimum between 16 and 14.5 Ma to the growth of the Antarctic ice sheet. In this study we will be conducting XRF scanning (verified by XRF measurement of discrete samples) on the Unit II cores from Hole M0027A with the objective of linking a chemical signature to the changes in the cores' physical properties. Ultimately the scope of the project will be extended to include the two other holes cored during IODP Expedition 313 (Holes M0028A and M0029A). It is anticipated that characterisation of the shelf sedimentation during the mid-Miocene global cooling event will be possible from these data and we will endeavour to tie chemical variations (notably, but by no means exclusively, Mg/Ca, Fe, Ca/Sr and Ca/K) to both physical properties data and other datasets from the cores. Preliminary data from this study will be presented at the meeting.