Constraining the age and formation of stone runs in the Falkland Islands using Optically Stimulated Luminescence

Hansom, James D.; Evans, David J. A.; Sanderson, David; Bingham, Robert G.; Bentley, Michael J.

doi:10.1016/j.geomorph.2007.05.006

Cited by 28 publications

(13 citation statements)

References 23 publications

(27 reference statements)

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“…However, Miller (1990) has alternatively suggested that the larger blocks within the so-called 'upper head' were rafted downslope on the main body of head and hence are not separated significantly in time; this argument may be purely semantic as Waters (1964) did infer that the sequence represented an inversion of the pre-existing granite weathering profile through progressive mass wasting. This is very similar to the exposures through ancient stone runs such as those on the Falkland Islands (Hansom et al, 2008) and hence would not be unusual in valley floor settings in ancient periglacial landscapes. However, the age of these deposits and hence the mapped slope forms on Bodmin Moor is unknown and whether they record numerous periods of cold climate conditions or merely the intensive periglacial processes of just the last glacial cycle is yet to be determined.…”

Section: Periglacial Slope Depositssupporting

confidence: 68%

“…Hence the landsystem signature may have been generated over the last glacial cycle or longer. Nevertheless, landforms that indicate extreme periglacial landscape maturity elsewhere, for example the stone runs of the Falkland Islands (Hansom et al, 2008;Wilson et al, 2008), are not well developed around the lower slopes of the Bodmin Moor tor summits. Their occurrence in surrounding valleys, beyond the mapping areas presented in this paper, could potentially verify extreme periglacial landsystem age.…”

Section: The Periglacial Landsystem Of Bodmin Moor and Its Implicatiomentioning

confidence: 99%

“…It is surprising, therefore, that little systematic mapping of periglacial landforms has ever been undertaken on the granite uplands, an important exception being the assessment of Cox Tor and its environs by te Punga (1956Punga ( , 1957, Gerrard (1988) and Miller (1990), where altiplanation terraces and spectacular examples of 'clitter' (blockfield) landforms such as boulder lobes and boulder runs were identified and used as exemplars of periglacial landscape maturity. Boulder runs and castellated tors in particular are definitively indicative of mature periglaciation in settings that have never been glaciated, such as the Falkland Islands for example (Clapperton, 1975;Clark, 1972;Hansom, Evans, Sanderson, Bingham, & Bentley, 2008;Joyce, 1950;Wilson, Bentley, Schnabel, Clark, & Xu, 2008). More recently Evans et al (2012aEvans et al ( , 2012b and Harrison and Evans (2014) have highlighted that the Cox Tor and neighbouring Staple Tor area, with its castellated tors, altiplanation terraces and mature boulder lobes and runs, contrasts markedly with the core of the north Dartmoor landscape where such apparently mature periglacial landforms are not as well developed; instead, this core area, the highest terrain of the Dartmoor uplands, is characterized predominantly by summits with subdued or no tors and a sparsity of mature boulder lobes and appears to have been formerly glaciated.…”

Section: Introductionmentioning

confidence: 99%

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Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

2017

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Section: Periglacial Slope Depositssupporting

confidence: 68%

Section: The Periglacial Landsystem Of Bodmin Moor and Its Implicatiomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

2017

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“…Recently, Hansom et al (2008) have applied optically stimulated luminescence (OSL) dating to the fine-grained material underlying stone runs at two sites in East Falkland. The samples yielded ages from >54k to 16k yr BP but the saturation of the luminescence signal meant that they were unable to place an upper limit on the ages of the oldest samples.…”

Section: Introductionmentioning

confidence: 99%

Stone run (block stream) formation in the Falkland Islands over several cold stages, deduced from cosmogenic isotope (¹⁰Be and ²⁶Al) surface exposure dating

Wilson

Bentley

Schnabel

et al. 2008

J Quaternary Science

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S. 2008. Stone run (block stream) formation in the Falkland Islands over several cold stages, deduced from cosmogenic isotope ( 10 Be and 26 Al) surface exposure dating.ABSTRACT: Cosmogenic isotope ( 10 Be and 26 Al) surface exposure dating has been applied to valley-axis and hillslope stone runs (relict periglacial block streams) and their source outcrops in the Falkland Islands, South Atlantic. The data indicate that stone runs are considerably older landforms than previously envisaged and afford no evidence that they are a product of the Last Glacial Maximum; the samples range in apparent 10 Be age from 42k to 731k yr BP, but some of these are minima. The results indicate that valley-axis stone runs may be up to 700-800k yr old, have simple exposure histories and are composite landforms that developed over several cold stages. Analyses of some hillslope and outcrop samples also demonstrate simple exposure histories with 10 Be ages from 42k to 658k yr BP. In contrast, isotopic ratios from other hillslope and outcrop samples reveal they have had a complex exposure history involving periods of burial or shielding; the samples range in 10 Be age from 59k to 569k yr BP and these are regarded as minimum age estimates. Larger stone runs may be older than smaller runs and there is a possibility that stone runs older than 800k yr exist in other parts of the Falklands. The assertion that glaciation in the Falklands was restricted to the highest uplands is supported by the data, and the potential for age determination of other boulder-strewn and bedrock landforms, using cosmogenic isotope analysis, in order to extend the geochronology of Quaternary events and processes is noted.

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“…The widespread evidence for clay weathering products and rounded nature of boulders associated with some block deposits, do suggest that block deposits in part owe their formation to chemical weathering (Caine 1983, Rea et al 1997. The principle driver of formation of block deposits has been debated particularly in the Falkland Islands (Andrè et al 2008, Hansom et al 2008, Wilson et al 2008, however studies of the deposits in the Falklands and similar studies from Scandinavia which present evidence for chemical weathering still acknowledge the role Late Quaternary periglacial conditions have played on block deposit development (Rea et al 1997, Whalley 1997, Van Steijn et al 2002, Andrè et al 2008, Goodfellow et al 2009). Block deposits with obvious headwall sources are clearly products of mechanical weathering with chemical weathering playing a secondary role in formation.…”

Section: Block Depositsmentioning

confidence: 99%

The distribution and paleoclimate implications of periglacial landforms in eastern Australia

Slee¹

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It is widely recognised that during the Late Quaternary, glaciation was limited in Australia, especially away from Tasmania. This contrasts with the widely recognised occurrence of periglacial landforms in SE Australia, particularly in Australian Alps and Tasmania.However, very little research has been undertaken into these landforms. The aim of this thesis is to investigate the extent and timing of Late Quaternary periglacial conditions in south-eastern Australia and to understand the geomorphic processes and environments associated with these landforms. This thesis presents an updated understanding of the distribution, morphology and climatic significance of periglacial landforms in eastern Australia. The thesis is divided into two sections. The first section is focused on modern 'active' periglacial landforms found primarily in the mountainous areas of Tasmania and focuses on two studies of modern freeze-thaw processes in western Tasmania. At higher elevations (1000 m) notable freeze-thaw features are active at the present time including stone banked lobes on Mt Rufus. Freeze-thaw features were identified to only 150 m above sea-level near Queenstown. However, these low elevation freeze-thaw landforms are small scale features associated with short periods where shallow ground ice forms.The second section of the thesis focuses on relict periglacial landforms that display no evidence of modern activity and most likely relate to late Quaternary cold climate conditions. It primarily focuses on the block deposits of eastern Australia, their morphology, distribution and climatic significance. Block deposits and associated landslide deposits from northern New South Wales to Tasmania were mapped. Four sites were studied in more detail and dated using surface exposure dating (SED). They yielded ages ranging from early Holocene to OIS 5 which are internally consistent within sites but vary widely between sites. These data provide evidence for repeated phases of periglacial activity during the last glacial cycle. At Guyra, several phases of mass movement were recognised with large scale landslides associated with a much earlier warm and humid climate dominating the landscape. Freeze-thaw landforms of the late Quaternary are superimposed on these older forms. The scale of last glaciation cooling is indicated by evidence for a possible nivation hollow bounded by a pronival rampart located near the town of Guyra (29°30'S). From this site a cooling range of 8-11°C is inferred, but additionally, relatively moist conditions are required for the nivation feature to form.The concept of a relatively humid glaciation also emerges from the mapping of the freezethaw landforms on a regional basis. In particular the occurrence of block deposits and screes in northern New England in patterns matching the modern precipitation gradient indicates that freeze-thaw was preferentially concentrated in a zone parallel to the coast. It is inferred that this zone represented an area of intermediate moisture landward of the divide separa...

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Constraining the age and formation of stone runs in the Falkland Islands using Optically Stimulated Luminescence

Cited by 28 publications

References 23 publications

Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

Stone run (block stream) formation in the Falkland Islands over several cold stages, deduced from cosmogenic isotope (¹⁰Be and ²⁶Al) surface exposure dating

The distribution and paleoclimate implications of periglacial landforms in eastern Australia

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Constraining the age and formation of stone runs in the Falkland Islands using Optically Stimulated Luminescence

Cited by 28 publications

References 23 publications

Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

Periglacial geomorphology of summit tors on Bodmin Moor, Cornwall, SW England

Stone run (block stream) formation in the Falkland Islands over several cold stages, deduced from cosmogenic isotope (10Be and 26Al) surface exposure dating

The distribution and paleoclimate implications of periglacial landforms in eastern Australia

Contact Info

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Stone run (block stream) formation in the Falkland Islands over several cold stages, deduced from cosmogenic isotope (¹⁰Be and ²⁶Al) surface exposure dating