Harold Lovell

A glacial geomorphological map of the southernmost ice lobes of Patagonia:the Bahía Inútil – San Sebastián, Magellan, Otway, Skyring and Río Gallegos lobes

This paper presents a glacial geomorphological map of the landforms created by five large ice lobes that extended eastwards from the southernmost reaches of the Patagonian Ice Sheet during the Quaternary period. The study is focussed on Tierra del Fuego, but also updates previous mapping of the Skyring and Otway lobes, and the resulting level of detail and extent is a significant advance on previous work in the region. The map has been created as the necessary precursor for an improved understanding of the glacial history of the region, and to underpin a programme of dating glacial limits in the region. It was produced using Landsat ETM+ and ASTER satellite imagery and vertical aerial photography, supplemented by Google Earth™ imagery and field-checking. Eleven landform types were mapped: moraine ridges, subdued moraine topography, kettle-kame topography, glacial lineations, irregular and regular hummocky terrain, irregular dissected ridges, eskers, meltwater channels, former shorelines and outwash plains. The map reveals three important characteristics of the glacial geomorphology. First, the geomorphic systems are largely dominated by landforms associated with meltwater (channels, outwash plains and kettle-kame topography). Second, there is a difference in the nature of landforms associated with the northern three ice lobes, where limits are generally marked by numerous clear moraine ridges, compared to those to the south, where hummocky terrain and drift limits prevail. Finally, cross-cutting landforms offer evidence of multiple advances, in places, which has implications for the timing of limit deposition, and thus for the design and interpretation of a dating programme.

Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

Mapped topographic features are important for understanding processes that sculpt the Earths surface. This paper presents maps that are the primary product of an exercise that brought together 27 researchers with an interest in landform mapping wherein the efficacy and causes of variation in mapping were tested using novel synthetic DEMs containing drumlins. The variation between interpreters (e.g. mapping philosophy, experience) and across the study region (e.g. woodland prevalence) opens these factors up to assessment. A priori known answers in the synthetics increase the number and strength of conclusions that may be drawn with respect to a traditional comparative study. Initial results suggest that overall detection rates are relatively low (34–40%), but reliability of mapping is higher (72–86%). The maps form a reference dataset.

A glacial geomorphological map of the Seno Skyring-Seno Otway-Strait of Magellan region, southernmost Patagonia

Abstract Please click here to download the map associated with this article. This paper presents a detailed glacial geomorphological map covering over 16,000 km of the Seno Skyring-Seno Otway-Strait of Magellan region in southernmost Patagonia. It builds on previously published maps produced at a variety of scales and is re-mapped in detail for the purposes of reconstructing the pre-Last Glacial Maximum (LGM) glacial dynamics of the region, with particular focus on deciphering the glacial landsystem north east of Seno Otway, which has been postulated as a zone of ice streaming. Additional areas of interest include the reconstruction of proglacial lakes dammed by the Skyring and Otway lobes; their drainage during various stages of retreat; and a landsystems approach to the overall reconstruction of the combined Skyring-Otway-Magellan ice lobes. Mapping was conducted using a combination of Landsat ETM+ and ASTER satellite imagery and oblique and vertical aerial photographs, and is centred on approximately 53_S, 71_W. Seven main landform types have been mapped: glacial lineations, moraines, meltwater channels, irregular dissected ridges, eskers, outwash plains and former shorelines. The map records several episodes of ice flow, as revealed by glacial lineations, with the area around Laguna Cabeza del Mar exhibiting spectacular elongate drumlins. Drumlin fields are associated with three major ice lobes whose extent is marked by a series of moraine ridges and lateral meltwater channels. Large parts of the area were also subjected to proglacial meltwater erosion and deposition, as recorded by large tracts of outwash and associated channels.

Debris entrainment and landform genesis during tidewater glacier surges

The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.

Glacitectonic composite ridge systems and surge-type glaciers: an updated correlation based on Svalbard, Norway

Glacitectonic composite ridge systems are found at the margins of a number of surge-type glaciers globally. On the High-Arctic archipelago of Svalbard, the pioneering work of Croot (Glaciotectonics: forms and processes. Balkema, Amsterdam, 1988) highlighted the coincidence between composite ridge systems and surge-type glaciers on the island of Spitsbergen. These observations have contributed significantly to our understanding of the links between glacier surges and the landforms they produce. We update this work and expand it to the whole archipelago using the Norwegian Polar Institute’s TopoSvalbard aerial photograph archive to identify 50 composite ridge systems. These are found on all four of the largest islands: Spitsbergen, Nordaustlandet, Edgeøya and Barentsøya, and at the margins of both tidewater and land-terminating glaciers. Of the 50 composite ridge systems, 49 are associated with glaciers that have either been documented as surge-type or contain indicative geomorphological evidence of surging in the form of crevasse-squeeze ridge (CSR) networks. This provides further support for the established link between composite ridge systems and surging. Based on the proportion of glaciers that are documented as being of surge-type and those that display indicative evidence of surging (but have not been observed to surge), we conclude that at least 32.6% of all glaciers in Svalbard surge or are likely to have surged. This study contributes to the understanding of the links between glacier surging and specific landforms/landform assemblages (composite ridge systems and CSR networks), which has applications in other modern glacial environments and at the margins of former ice masses in palaeoglaciological settings.

Dendritic Subglacial Drainage Systems in Cold Glaciers Formed by Cut-and-Closure Processes

Abstract The routing and storage of meltwater and the configuration of drainage systems in glaciers exert a profound influence on glacier behaviour. However, little is known about the hydrological systems of cold glaciers, which form a significant proportion of the total glacier population in the climate sensitive region of the igh rctic. Using glacio‐speleological techniques, we obtained direct access to explore and survey three conduit systems and one moulin within the tongue area of Tellbreen, a small cold‐based valley glacier in central pitsbergen. More than 600 m of conduits were surveyed and mapped in plan, profile and cross‐section view to analyse the configuration of the drainage system. The investigations revealed that cold‐based glaciers can exhibit a dendritic drainage network with supra‐, en‐ and subglacial components formed most likely by cut‐and‐closure processes as well as surface‐to‐bed drainage via moulins. Furthermore, we observed that water is stored within the glacier and released gradually via subglacial conduits during the winter months, forming a large and active icing in the proglacial area. The presence of supra‐, en‐ and subglacial components, the surface‐to‐bed moulin and the dendritic subglacial drainage network suggest that existing models and understanding of the hydrology of cold glaciers needs to be re‐evaluated, mostly concerning the different possible pathways and processes that form the hydrological system.

Chapter 2 The Quaternary

Abstract The Quaternary is the youngest geological period, beginning 2.58 Ma ago and including the present day; it is therefore the only geological period that is continuously growing. During the first epoch of the Quaternary, the Pleistocene, extremely cold and warm conditions alternated, frequently over short periods of time. This resulted in processes currently only operating in cold (polar and high-mountain) environments extending to and affecting the mid-latitudes, including the currently densely populated areas of North America and Europe. In Britain every region has been affected by cold-region processes, which have produced unique sedimentary and geomorphological signatures. Hence, an intimate knowledge of these processes is of direct relevance to engineering geologists and anyone working with natural materials. This chapter reviews the state of the art of (a) the stratigraphic (nomenclatorial) framework of the Quaternary, (b) prominent concepts that are of direct relevance to understanding the detailed overviews in Chapters 3–5; and (c) key findings on the dynamics of these processes and their implications for engineering-geological questions and problems.

The glacial landsystem of a tropical glacier: Charquini Sur, Bolivian Andes: The glacial landsystem of a tropical glacier

The geomorphological signature of tropical glaciers has the potential to provide important information on the response of ice masses in high-mountain environments to climate warming. This study investigates the glacial geomorphology of Charquini Sur, Bolivia. Detailed geomorphological mapping was conducted both in the field and from satellite imagery in order to produce a 1:4000 scale geomorphological map of the glacier foreland. Sedimentological analyses (description of physical characteristics, clast shape and roundness, particle-size distribution) provided additional insight into the landform–sediment assemblage. Glacial landforms are well preserved and include up to 11moraine ridge suites, seven of which are cross-valley frontal moraine arcs. These can be linked to an existing lichenometric chronology from previous work and record glacier recession since the local Little Ice Age (LIA) maximum in the late-1600s. Lateral moraine ridges also record continuous thinning of the glacier over this time period. Smaller groups of parallel ridges are interpreted as annual moraines formed during recession. Intermorainic areas consist of flutings and a typically thin sediment cover of subglacial, supraglacial and glaciofluvial origin, with prominent ice-moulded bedrock protuberances in places. Analysis of the landform–sediment assemblage provides an insight into the main controls on landform genesis in the basin and implies there have been temporal changes in ice-marginal dynamics since the LIA. We present the first landsystem model for a tropical cirque glacier, documenting its behaviour since the LIA and providing an indication of glacier response in rapidly-warming high-mountain environments. Copyright