Original paper
Astronomical calibration of the Early Jurassic Sinemurian Stage based on cyclostratigraphic studies of downhole logging data in the Prees 2 borehole (Cheshire Basin, UK)
Leu, Katharina; Zeeden, Christian; Ulfers, Arne; Abadi, Mehrdad Sardar; Vinnepand, Mathias; Ruhl, Micha; Hesselbo, Stephen; Wonik, Thomas
Newsletters on Stratigraphy Volume 57 Number 3 (2024), p. 257 - 282
102 references
published: Jul 11, 2024
published online: Mar 26, 2024
manuscript accepted: Feb 14, 2024
final revised version received: Feb 11, 2024
manuscript revision requested: Dec 20, 2023
manuscript received: Aug 28, 2023
Open Access (paper may be downloaded free of charge)
Abstract
The duration of the Early Jurassic Sinemurian Stage is presently poorly constrained; it is however of importance to develop an accurate and precise timescale for the Early Jurassic period. Borehole data from the new Prees 2 site in the Cheshire Basin (England, UK) were investigated to construct an astronomically based timescale for this stage. The drilled succession is ~650 m in length and comprises sediments of Rhaetian (Late Triassic) to early Pliensbachian (Early Jurassic) age (~202–190 Ma), which comprise a predominant mudstone lithology with varying limestone and silt content. Cyclostratigraphic methods are applied to the Sinemurian section of the sum gamma ray downhole logging data, as well as to potassium-, thorium- and porosity-logs, to derive a timespan for deposition of the studied succession. Two analytical approaches were applied to the data, including visual and statistical techniques, yielding different duration estimates, of ~6.8 Myr and ~6.2 Myr, respectively. Sedimentation rates for the largely argillaceous Sinemurian sediments are estimated to range from ~3.6–6.7 cm/kyr. Collectively, our results provide new insights into the absolute duration of the Sinemurian Stage, improving and reducing the hitherto only broadly constrained duration estimates of ~6.2–7.6 Myr.
Keywords
Geological Timescale, Astronomical Tuning, Geophysical Logging Data, Early Jurassic, Sinemurian