This dataset resulted from a parallel monitoring at two lakes, Lake Tiefer See (near Klocksin, TSK; 53° 35.5’ N, 12° 31.8’ E; 62 masl; N Germany) and Lake Czechowskie (Jezioro Czechowskie, JC; 53° 52.4’ N, 18° 14.3’ E; 108 masl; N Poland), and includes four different type of data for both locations: (i) sediment cores microfacies data, (ii) sediment fluxes and composition, (iii) selected water column data, and (iv) selected meteorological information obtained on site. This dual lake monitoring set-up was established in 2012 with the aim to investigate seasonal sedimentation and varve forming processes in detail. The datasets are provided in individual *.csv files, per type of data and per lake. The thin section data from surface sediment cores comprises the thicknesses of the most recent calcite varves’ sub-layers: spring diatom sub-layer, summer calcite sub-layer, and autumn/winter re-suspension sub-layer. The sediment flux data was obtained from sediment traps located in different water depths (epi- and hypolimnion), and the sediment composition is given by the fluxes of total organic carbon (TOC), calcium carbonate (as calculated from total inorganic carbon; TIC), and diatoms & inorganic matter. The water column data comprises water temperature from stationary loggers, and dissolved oxygen measured in ~ 1 meter depth-resolution. The meteorological data includes daily averages of air temperature and mean wind-speed, and summed daily rainfall. Further details about the sampling and analytical methods, data acquisition, and processing are given in Roeser et al. (2021; http://doi.org/10.1111/bor.12506).
The data collection presented here is the data inventory of the VARved sediments DAtabase (VARDA) in version 1.3. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. All data were collected as raw data from freely available online sources, either from online data repositories (Pangaea, NOAA, and Neotoma) or data archives within the supplementary materials section of online publications. The current data collection consists of meta information and datasets from 95 lake archives. The data is stored in JSON and CSV format. All datasets are stored as individual files (JSON and CSV). Each dataset consists of samples for either i) chronologies; ii) radiocarbon data; iii) tephra layer; or iv) varve thickness data. Meta-information for each dataset is summarized in one csv and seven JSON files. Additional paleoclimate proxy data will be provided in forthcoming updates of VARDA.
The data collection of VARDA Version 1.3 is provided as an archive (.tar.gz) with the following files/folders. Overview lists with categories, cores, countries, datasets, lakes and publications included in VARDA. Each item in the lists is cross-referenced with the other files via its $ref property which includes the corresponding list index or the dataset's UUID (from the VARDA database). The data points themselves are provided in the "records" folder and named with each dataset's UUID respectively. For more information on the data structure please read the "index.html" file included in the archive and available on the DOI landing page.
VERSION HISTORY:
26 July 2020: release of Version 1.3:
1. Fix issues with chronologies in the export
2. Provide recalculated machine readable error estimates
3. Correct some metadata values (e.g. core labels)
5 March 2020: release of Version 1.1
1. Added fields:
"distributor" - Field containing name of data distributor
"url" - Field containing DOIs and URLs, which lead to the original data publications
2. Correction of publication DOIs in 9 cases
The version 1.0 is available in the "previous-versions" subfolder via the Data Download link. The index file is unchanged.
The Quaternary Drilling at the Rehhag under the supervision of members of the Institut für Geologie (QDR-RE-IfG) was interested in the unconsolidated sediment infill of a bedrock trough in the Northern Alpine Foreland (NAF). Such bedrock troughs, now hidden beneath their sediment infill and/or in lakes, occur in formerly and currently glaciated areas, and are linked to increased glacial erosion. The base of these bedrock troughs is located beneath today's base level, which puts them beyond fluvial erosion, and this is why they are referred to as over-deepenings. Such overdeepenings can be found in the vicinity of the Alps which includes the NAF. After the formation or re-occupation of such overdeepenings by glacier ice these troughs provide accommodation space for the deposition of sediments. Hence, overdeepenings are likely to preserve sediments through glacial-interglacial cycles. As erosive agents, glaciers re-shape landscapes, and excavate and re-use sediments of previous glaciations which makes the preservation of intact sedimentary sequences through multiple glacial cycles unlikely. These repeated cut-and-fill cycles limit the Quaternary sedimentary record and make the investigation of the number and chronology of Quaternary glacial-interglacial cycles difficult. Overdeepenings, however, can preserve fractionated and probably intact sedimentary sequences throughout multiple glaciations. Hence, accessing the sediment infill of overdeepened bedrock troughs through core drillings provides insight into phases of the Quaternary at locations where formerly little information was available.
To gain new insight into the Mid- to Late-Pleistocene sedimentary record in the Bern area (Switzerland) the drilling QDR-RE-IfG was conducted in Bern-Bümpliz, where a minor branch of the Aare Valley overdeepening is located in which Quaternary sediments at least 150 ka in age were expected. In Bern-Bümpliz, at the Rehhag, the uppermost 30 m of the sedimentary succession are accessible in an abandoned clay pit. The drilling reached 211.5 m driller's depth, recovering 208.5 m of unconsolidated sediment and, below a sharp contact, 3 m of Miocene Molasse bedrock. The recovery of intact core from unconsolidated sediment is challenging. Nevertheless, 92.3% of the core material was recovered in 1 m-long plastic liners in pristine condition. As the drilling reached the bedrock it is the first scientific drilling that recovered the full sedimentary suite in a part of the Aare Valley overdeepening. Within the sedimentary succession two sequences (A = lower, B = upper) were identified. Each of the sequences is initiated by the deposition of glacial till that is overlain by lacustrine or glacio-lacustrine sediments. First luminescence ages indicate a depositional age between 250 and 340 ka for sequence B.
The drill core was transported from the drill site to the Institute of Geological Sciences, University of Bern, where it was analyzed and sampled. The first step in the analysis was scanning the whole core contained in the liners on a Multi Sensor Core Logger (MSCL; Geotek Ltd.) which provided measurements of the core (γ-)density, p-wave velocity and magnetic susceptibility. The liners were then opened under light sensitive conditions, the cores split in half to allow their macroscopic description, and one half was sealed from light and other alterating influences. After the description, the core was documented with a digital line scanner on the MSCL. After the documentation, a vane meter was used to determine the shear strength of the material and samples for pollen analysis, analysis of the carbon content, provenance analysis, and the measurement of cosmogenic nuclides 10Be and 26Al were extracted.
This report provides limited information about the drilling operation, describes the available datasets form scanning and sample analysis, and the results of the first data processing as well as the tools used in the data analysis.