Geochemistry and cyclostratigraphy of homogeneous deposits using high-resolution hand-held X-ray Fluorescence: Outcrop to subsurface correlation, sequence stratigraphy, and constraints on hiatuses (middle-Upper Eocene, Tunisia)

Abstract

This paper aims to determine the applicability of the handheld X-ray fluorescence (HH-XRF) for studying homogenous deposits, which finds essential applications in economic geology and paleoenvironmental studies. We tested using the HH-XRF in thick mudstone series to delineate the sequence stratigraphic framework and redox conditions in the deep-water section and for outcrop to well correlation in the shallow water deposits. Samples that exhibit maximum or minimum values for Si and Ti elements were chosen for the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis to help establish sequence boundaries. A comparison of HH-XRF and ICP-MS for measuring major and minor element concentrations was applied to validate the HH-XRF data. The data was normalized by Al and Ti to reveal the major trends. Si/Al and Si/Ti measurements have proven particularly useful for delignating sequences in homogeneous deep-water mudstones and cyclostratigraphy. Changes in Mo/Al, As/Al, V/Cr, V/(V + Ni) and isolated peaks in Sulphur during the Lutetian – Bartonian transition have been related to Maximum Flooding Surfaces (MFS) or Sequence Boundaries (SB). They are, therefore, associated with condensation or no deposition rather than a significant change in oxygenation conditions in the bottom waters of the outer ramp of our basin. Consequently, they do not truly reflect dysoxia but rather the peculiar chemical conditions associated with condensation.