Glacial Field Trip Notes
Site 1: North-West Pennines
The glacial history of the site is interesting, and landscape physiography was important for ice movement.
The area sees increases in elevation from Durham to the Alston Block. This feeds distinctive valleys from high altitude down to the East Coast (e.g., the Wear/Tees).
Distinctive high elevation area with a fluvial imprint. Limited evidence of long-term glaciation.
The Tyne Gap (North), Eden Valley (South), and Stainmore Gap surround high plateau areas (Alston Block).
Highland areas appear fluvial, and lowland areas appear glacial.
History of ice accumulation in the area.
High elevation areas like the Alston Block encourage ice and snow accumulation.
Moisture approaching from the West created a rain shadow.
High elevation areas like the Alston Block developed ice caps, whilst lowland areas harboured ice streams.
Coalescence between lowland ice streams and local ice caps.
Wind direction and summit breadth/elevation are important in this.
Temperate regime of ice.
High elevation areas encouraging ice accumulation were likely cold-based ice. This explains the apparent fluvial signature - minimal glacial erosion occurred here. True over the Alston block where blockfields can be seen. These are periglacial features which occur due to frost-shattering in cold-based regions. Cold-based ice also suggests thin ice at high elevations - as temperature increases with ice column depth (thicker ice is usually warm-based).
Low elevation areas which demonstrate strong evidence of glaciation probably had warm-based ice. More streamlined at the beds (which could also suggest sliding).
Manley theory of summit breadth - suggests that broader summit = more snow accumulation (becomes firn, leads to ice cap formation).
The Alston Block is referred to as a 'horst' - raised block bounded by faults on either side. Uplifted to the East, which facilitates fluvial processes. Drainage direction is determined by underlying topography (whin sill).
Erratics in this region are important indicators of ice flow direction and the location of dispersal centres. The Tyne Gap and Eden system have lots of exotic erratics. Ice flow is predominantly to the East.
Largely carboniferous as a result of long-term geomorphic tectonics.
Area is a zone of ice coalescence between Lake District ice and Stainmore Gap ice. Regional ice from Scotland is also seen.
Equivalent of 1.8m SL stored in the BIIS 23kya.
Timings of ice retreat and advance.
Much ice flowed to the east until approximately 23 kya.
The BIIS merged with the Fennoscandian Ice Sheet 23 kya - triggered rapid onset deglaciation and flow reversal in the Eden.
Rapid retreat of marine margins began around 22kya (linked to Saddle collapse in the North Sea).
Ice flow direction changed to the west.
Timing of ice advance/retreat (and of the LGM) is asynchronous.
Maximum ice build-up is between 23 - 27 kya.
Local ice centres merged with ice from Scotland (23 - 27 kya ice flow went from west to east).
Stop 2 within site one - meltwater channel just above Lunedale (Lonton stage).
Meltwater channel in the north-west Pennines; the visible slope is crisscrossed by interconnected, oblique meltwater channels. Channels move downwards in lateral steps - these are likely ice marginal channels reflecting retreat (not subglacial drainage). These are really good for reconstruction, determination of ice flow direction, and observations of thinning.
Meltwater would have been trapped in lateral channels due to cold-based ice (frozen to the bed) at the edge of the Ice Sheet as it retreated. Ice thinning causes a transition to cold-based ice - could suggest that ice may have been polythermal.
Interconnection implies ice may have been crenular at the margins.
Tees ice and Stainmore ice beginning to decouple.
Site 2: Stack Holme (upper Lunedale) at Hargill Beck
Data was collected on the clast fabric, sediment, and landscape profile. At this site, there is sequence of tills overlapped with one another and interbedded with canal fills. Till facies indicate changes from ice flow by bed deformation to ice flow by sliding. Direction of ice flow is from the Stainmore Gap. Sediment profile can be found in Notes booklet (predominantly diamicton), and Erin has notes on clast measurements.
Clast measurements.
Show the direction of ice flow and the stress field.
The weight of ice transfers shear stress to the sediment (causes lateral shearing). The stones in the till experience overburden pressure and lateral shear stress. Theoretically, the long axis of the stones aligns with lateral shear stress - typically causes clasts to orientate slightly upwards in ice flow direction (especially in ice marginal/lateral regions).
Data shows ice travelling south-east as the stones are dipping towards the north-west.
Far-travelled erratics, unsorted nature, sub-angular to sub-rounded clast, striations, facets on rocks - all show evidence of glaciation at this site. Strong fabrics, unconsolidated till, and diamicton suggest subglacial sediment.
Sediment deformation has been a key mode of ice transport.
Other key structures in the area.
Fine material (potentially clay) with minimal clasts - likely transported by water, potential evidence of sliding and canal infilling.
Site 3: Eden Valley Drumlins
A large drumlin field; series of low amplitude hills. These are large features, and many are superimposed with other landforms.
Till stratigraphy reveals major reversal of ice flow in the Eden valley:
Lower till contains Scottish erratics which record southerly advance up the Eden valley and through the Stainmore Gap; and
Upper till contains Lake District and Pennine erratics which record ice advance down the Eden valley and into the Solway Lowlands.
^^ Ice sheet reorganisation. Some drumlins are made of these two till types - suggests flow reversal. Drumlin superimposition with younger landforms also suggests that ice flow pattern and direction was changing over time.
Likely warm-based ice as drumlins are streamlined. Blockfields on top of nearby high-elevation areas suggests that these regions had cold-based ice.
There are several theories of drumlin formation.
Erodent bed hypothesis, meltwater theory, Boulton hypothesis, and instability theory (look into these).
The drumlins in the Eden valley could have been formed through any of these theories except for the meltwater theory (unlikely as there are no mega-scale landforms in the Eden valley).
Shaw and Eyles hypothesis is important (look into this).
Drumlins are important for a number of reasons.
Flow direction indicators, suggest base dynamics of ice streams (not seen in modern streams due to accessibility issues - it is difficult to see under the ice to bed dynamics).
Ice recession in the Eden occurred after the end of the LGM, and the area was deglaciated approximately 18 - 20 kya.
Stainmore Gap became ice free approximately 19.8 cal ka BP.
Site 4: Brampton Kame Belt and Talkin Tarn