An Examination into the Impact of Diagenesis on Biogenic Silica δ³⁰Si Isotope Signals

Description

Biogenic silica isotopic (δ³⁰Si) values are an important paleoenvironmental proxy in environmental change research within the paleoclimate community. Silica is a key component in global biogeochemical cycles, coupling to other elemental systems and helping to regulate the Earth’s climatic progression across geological history. Biogenic silica δ30Si signals are commonly used to help reconstruct past changes in biogeochemical cycling. This is based on the general assumption that δ³⁰Si signal preservation of amorphous biogenic silica (opal-A) remains resilient to dissolution and early diagenetic overprinting following burial. Following deposition, however, opal-A is predisposed to physical and chemical transformations towards a more ordered crystalline structure, known as opal-CT. We lack a proper understanding of how post depositional phase transformations and structural re-mineralization, can affect δ³⁰Si values. Thus, understanding the mechanisms behind late digenetic processes is crucial for the interpretation of past δ³⁰Si signatures. To better constrain the diagenetic transition between opal-A and opal-CT, we use a suite of both qualitative and quantitative (i.e., XRD, SIMS, MC-ICPMS, SEM and Raman Spectroscopy) techniques to examine natural unaltered sponge spicule opal-A parallel to cretaceous samples exhibiting late diagenetic transformation. This study provides new insights into the impact of diagenetic transformations on δ³⁰Si isotopic signatures and offers a prediction on the reliability of the continual use of opal-CT as a paleoenvironmental proxy for the interpretation of climatic development and geochemical balance of our oceans.

Period	1 Mar 2022
Event title	Ocean Sciences Meeting: OSM 2022
Event type	Conference
Conference number	OSM2022
Location	VirtualShow on map
Degree of Recognition	International