Data Publication

Stratigraphic and Multi Scanner Core Logging (MSCL) data plus supplementary luminescence dating material obtained from the scientific drilling QDR-RE-IfG and its drill site in the Aare Valley, Bern CH

GFZ Data Services

(2021)

Descriptions

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.

Keywords

Originally assigned keywords

scientific drilling

Quaternary

glacial sediments

overdeepening

stratigraphic sequence

luminescence dating

compound material > unconsolidated material > natural unconsolidated material > sediment > clastic sediment

EARTH SCIENCE > LAND SURFACE > SOILS > ORGANIC MATTER

EARTH SCIENCE > PALEOCLIMATE > LAND RECORDS > GLACIATION

EARTH SCIENCE > SOLID EARTH > ROCKS/MINERALS/CRYSTALS > SEDIMENTARY ROCKS > SEDIMENTARY ROCK PHYSICAL/OPTICAL PROPERTIES > LUMINESCENCE

In Situ/Laboratory Instruments > Corers > SEDIMENT CORERS

industrial process > drilling

methodology > dating

Phanerozoic > Cenozoic > Quaternary > Pleistocene

Corresponding MSL vocabulary keywords

Quaternary

MSL enriched keywords

Phanerozoic

Cenozoic

Quaternary

minerals

chemical elements

carbon

oxide mineral

ice

silicate minerals

phyllosilicates

clay

unconsolidated sediment

clastic sediment

clay

Measured property

mechanical strength

shear strength

elastic wave velocity

P-wave

Measured property

mechanical strength

shear strength

elastic wave velocity

P-wave

Pleistocene

Neogene

Miocene

Measured property

magnetic susceptibility

Equipment

borehole drilling

drill core

MSL enriched sub domains i

rock and melt physics

analogue modelling of geologic processes

paleomagnetism

geo-energy test beds

Source

https://dataservices.gfz-potsdam.de/panmetaworks/showshort.php?id=a7378048-c2d6-11eb-9603-497c92695674

Source publisher

GFZ Data Services