Title: Tracing sand provenance – lessons from extant systems and resilience of provenance signals in the subsurface
Researchers: Dr Seb Zimmermann and Prof. Peter Haughton
Conventional bulk rock analyses, heavy mineral studies and single grain geochronology are powerful and well-established tools in provenance and sediment tracking studies. However, these methods still struggle with apportioning volumes from different sources and unravelling possible grain recycling. Recent developments in analytical techniques (particularly LA-ICPMS) have facilitated the rapid acquisition of increasingly large datasets and more sensitive data. Reconstructing paleo-drainage is restricted by difficulties in recognising sedimentary recycling and mixing. K-feldspar is likely to be preserved over long transport distances and its common Pb-isotope composition can be linked to immediate sources. It can therefore provide additional insight alongside other provenance tools in terms of the ultimate source of the sand fraction and relative contributions from different parts of the drainage basin.
To understand deep sea sedimentation, burial history and provenance offshore Ireland, analogue studies are essential. 1) Plio-Pleistocene sediments in the Gulf of Mexico are analogues for deep-water systems in the Irish offshore. 2) Further analogues to investigate the impact of burial and diagenesis are found in the Central North Sea. Jurassic arkosic sandstones are buried between three and six kilometres and represent an excellent example to address open questions about recycling processes in combination with the impact of selective burial dissolution of feldspar grain populations. 2,3) Project hypothesis and objectives: Central North Sea This research conducts analyses of single K-feldspars from the Jurassic Fulmar Formation to investigate possible bias of the provenance signal due to burial and diagenesis. The formation is a well-studied arkosic sandstone with excellent reservoir properties. Thick successions of commonly highly bioturbated shallow-marine sands were buried to a range of depths between 3.2 and 6 km. Parsons et al. (2005) and Wilkinson et al. (2014) have shown that framework composition strongly depends on depth. These features are ideal to carry out the study on this formation prior further application offshore Ireland. Gulf of Mexico This research focuses on the recent evolution of modern systems and establishing new single grain isotopic proxies. Previous feldspar Pb-isotope and zircon geochronology work demonstrated the potential of the K-Feldspar Pb-isotope technique in tributaries and hinterland development of the Mississippi River (Blowick et al., 2015). The offshore Mississippi Fan preserves continental-scale sediment fluxes related to millennial-scale climate change, driven by increased glacial erosion and high discharge meltwater during ice retreats (Fildani et al.,2016). Combining these features creates great potential of understanding the sedimentary record and investigating supply during deglaciation down-dip in the Gulf of Mexico analysing IODP, DSDP and ODP samples.