The First Holocene Varve Chronology for the UK: based on the integration of varve counting, radiocarbon dating and tephrostratigraphy from Diss Mere (UK).

Abstract

<p>This paper reports the first Holocene varved chronology for the lacustrine sediment record of Diss Mere in the UK. The record of Diss Mere is 15 m long, and shows 4.2 m of finely-laminated sediments, which are present between ca. 9 and 13 m of core depth. The microfacies analysis identified three major seasonal patterns of deposition, which corroborate the annual nature of sedimentation throughout the whole interval. The sediments are diatomaceous organic and carbonate varves with an average thickness of 0.45 mm. A total of 8473 varves were counted with maximum counting error of up to  40 varves by the bottom of the varved sequence. To tie the resulting floating varve chronology to the IntCal 2020 radiocarbon timescale, we used a Bayesian Deposition model (P_Sequencewith outlier detection) on all available chronological data from the core. The data included five radiocarbon dates, two known tephra layers (Glen Garry and OMH-185) with calendar ages based on Bayesian modelling of sequences of radiocarbon ages, and the relative varve counts between dated points. The resulting age-depth model (DISSV-2020) dates the varved sequence between ca. 2100 and 10,300 cal BP and age uncertainties are decadal in scale (95% confidence). </p>

Holocene climate evolution and human activity as recorded by the sediment record of lake Diss Mere, England

“…A typical varve in the record is composed of a light endogenic calcite layer, and a darker organic layer formed of chrysophyceae cysts, organic matter, planktonic centric diatoms and occasional micrite (Peglar et al, 1984). Whilst the varves are consistently classified as biogenic-calcite, variability in the couplet described above are observedsuch as extremely thin or missing calcite layers or additional monospecific diatom bloomsand described in detail in Martin-Puertas et al (2021). The average sedimentation rate (i.e.…”

“…In addition, it is currently the only published lake record in the UK with a continuous varved sequence through much of the Holocene. The Holocene varves extend from 10 290 to 2069 years before present (before 1950 CE, cal a BP hereafter; Martin-Puertas et al, 2021). Combining microfacies analysis and XRF core scanning data allows us to explore sedimentological and compositional variations on seasonal to annual timescales.…”

“…The first sediment sequence from Diss Mere was studied in the 1980s with a particular focus on landscape evolution and land use history, described briefly above (Peglar, 1993;Peglar et al, 1984Peglar et al, , 1989. In 2016, a new sediment profile for the lake (DISS16) was collected and described in Martin-Puertas et al (2021). This sediment profile identified three distinct units (Fig.…”

“…The transition between Unit 2 and 1 is diffuse with the varved laminations gradually fading out over the last few varves. The Holocene sequence is continuous, with no hiatus identified (Martin-Puertas et al, 2021). The basal sediments of the DISS16 core (represented by Unit 3) are formed of reworked chalky till material and were impenetrable with the coring system, and thus the origin of the lake remains uncertain (Martin-Puertas et al, 2021).…”

“…Most of the research conducted to date on the DISS16 sediments has focused on the varved sediments (Unit 2) (Martin-Puertas et al, 2021Walsh et al, 2021;Harding et al, 2022;Walsh et al, 2023). A typical varve in the record is composed of a light endogenic calcite layer, and a darker organic layer formed of chrysophyceae cysts, organic matter, planktonic centric diatoms and occasional micrite (Peglar et al, 1984).…”