OR/19/016 Introduction
| Palamakumbura, R, and Auton, C. 2019. New exposed section in the Ardersier Silts Formation; November 20th-21st, 2017. British Geological Survey Internal Report, OR/19/016. |
The superficial sediments in the Ardersier area provide a unique insight into the glacitectonic processes during Late Glacial Maximum (LGM) deglaciation (Merritt, Auton, & Firth, 1995[1]). The contorted silts, sands and clays of the Ardersier Silts Formation (Gordon & Merritt, 1993) in this area have been designated a site of special scientific interest (SSSI) since 1984. A new sewage pipeline by Scottish Water provided a unique opportunity to study previously unexposed sediments of the Ardersier Silts Formation in this area.
The study area is north of the small village of Ardersier (Figure 1), which is approximately 12 km to the east of Inverness. The route of the pipeline is shown in Figure 2. The pipeline runs north to south from the sewage works at the shore, towards Ardersier Village. The examined trench section corresponds with, the portion of the pipeline that takes a short uphill incursion up to the top of the degraded Lateglacial cliff at c. 15 m above OD (Ordnance Datum), to provide a head, for flow between the sewage works and the village.
The site is located on the Nairn Sandstone Formation of the Forres Sandstone Group of the Orcadian Old Red Sandstone Supergroup. The Nairn Sandstone Formation comprises a yellow-brown and grey sandstones with sporadic mudstone seams, interpreted as representing a fluvial environment during the Devonian.
The superficial sediments in the area are reflective of the Late Quaternary glacial history of the region, in particularly deglaciation after the Last Glacial Maximum (LGM). The mapped superficial sediments across the surrounding area include Holocene tidal and beach deposits, the Late Devensian Ardersier Silts Formation, raised marine deposits, Alturie Gravels Formation, Glacial till and glaciofluvial deposits. The pipeline route crosses the Holocene raised marine deposits and the Ardersier Silts Formation.
Two days of fieldwork were undertaken to study the newly exposed section prior to back filling of the trench. The aim was to document the sedimentology and secondary glacitectonic structures in the exposed trench section. The following report provides a description of the sediments and structures observed.
References
- ↑ MERRITT, J W, AUTON, C A, and FIRTH, C R. 1995. Ice-proximal glaciomarine sedimentation and sea-level change in the Inverness area, Scotland: a review of the deglaciation of a major ice stream of the British Late Devensian ice sheet. Quaternary Science Reviews, Vol. 14, 289–329.