The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Shulmeister, James

doi:10.1016/j.quascirev.2016.07.024

Cited by 64 publications

(47 citation statements)

References 114 publications

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“…A vital component of such reconstructions is detailed, glacier-scale geomorphological mapping (Chandler et al, 2018;Clark et al, 2018;Evans & Orton, 2015). This provides spatial information that facilitates interpretations of palaeoglaciological behaviour and equips glacial geologists with an essential framework upon which to build robust chronologies (Chandler et al, 2018;Bendle et al, 2017a;Darvill et al, 2016). We thus present in this paper the first detailed glacial geomorphological map of three valleys in northeastern Patagonia (43.5°S), the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys (Figure 1b).…”

Section: Introductionmentioning

confidence: 99%

The glacial geomorphology of the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, northeastern Patagonia (43°S, 71°W)

et al. 2020

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This study presents the first detailed glacial geomorphological map of the sediment-landform assemblages formed by three eastern outlet glaciers of the former Patagonian Ice Sheet. These glaciers occupied the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, Chubut province, Argentina (43°S, 71°W). By combining remote sensing and field-mapping, we build on previous ice-sheet scale mapping and geological surveys to provide highresolution spatial information on local ice-contact glaciogenic, glaciofluvial, glaciolacustrine, and subglacial landforms. Twenty-five landform types, many of which are newly mapped in the region, were digitized as georeferenced shapefiles over a 5300 km 2 area. This map enables the identification of former ice-flow directions, relative ice-margin positions and glaciofluvial drainage pathways for each preserved Quaternary glaciation. It also elucidates the former areal extent, geolocation and spillways of glaciolacustrine bodies formed during the last deglaciation. The map delivers an essential framework on which to build robust glacier-scale geomorphological and geochronological reconstructions.

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Section: Introductionmentioning

confidence: 99%

The glacial geomorphology of the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, northeastern Patagonia (43°S, 71°W)

et al. 2020

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“…Indeed, it has been shown that glacial limits of the Bahía In util À San Sebasti an (BI-SSb) ice lobe that were previously thought to be pre-last glacial cycle were actually deposited more recently (Darvill et al, 2015b). This suggests that significant glacier advances during Marine Isotope Stage (MIS) 3 (and possibly MIS 4) are represented in the area, perhaps linked to wider glacial activity in the southern mid-latitudes at this time (Putnam et al, 2013;Kelley et al, 2014;Darvill et al, 2015b;Doughty et al, 2015;Schaefer et al, 2015;Darvill et al, 2016;Eaves et al, 2016). In this paper, we use a previously published map of the region, largely based on relatively high-resolution satellite imagery ($30-m resolution; Darvill et al, 2014), and apply glacial inversion methods to produce a new palaeoglaciological reconstruction of the dynamics of the ice sheet that is further constrained through analysis of published chronological data.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach

Darvill

Stokes

Bentley

et al. 2016

J Quaternary Science

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Reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing. This paper presents a new reconstruction of the glacial history of five ice lobes in southernmost South America: the Bahía Inutil À San Sebastian, Magellan, Otway, Skyring and Río Gallegos ice lobes. We use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes, demarcate flow-sets from the distribution of glacial lineations, and evaluate glacial landsystem signatures and their palaeoglaciological implications. Evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems, which may have switched to polythermal systems when periods of cold-based ice developed ephemerally. This complex landsystem signature implies that the ice lobes were sensitive to regional climate variability, with active re-advances during overall retreat of the ice margins. There is also evidence for periods of fast ice flow and possible surge-like activity in the region, followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes. Constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global Last Glacial Maximum (gLGM: ca. 26.5-19 ka) during the last glacial cycle. Our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed, and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate. As such, ice advances before the gLGM in the southernmost part of the Patagonian Ice Sheet are likely to indicate a wider climatic forcing at this time.

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“…Northwest Nelson saw expansion of conifer forest at around 14.5 ka (Jara et al, 2015), and at Okarito on the west coast, between 15 and 14.5 ka (Vandergoes et al, 2005); at Cass Basin in inland Canterbury, 15.7-14.5 ka and at Clarks Junction, eastern South Island, 15.5-13.5 ka (McGlone et al, 2003). A minor reversal of this warming trend occurred between 14.5 and 12.9 ka with glacial readvances in the Southern Alps (Darvill et al, 2016). By this time, dense tall conifer forest had occupied all but the driest eastern districts of the North Island and extensive stands were present in the lowland South Island throughout.…”

Section: Last Glacial Maximummentioning

confidence: 97%

“…A hemispheric warming and rapid retreat of glaciers began at about 17-18 ka following the last LGM advance at around 19 ka (Moreno et al, 2015;Darvill et al, 2016). Conifer-angiosperm forest spread in the central and northern North Island from 17 to 14 ka replacing previous forest-scrub-grassland mosaics (Figures 4-6).…”

Section: Last Glacial Maximummentioning

confidence: 99%

Palynology and the Ecology of the New Zealand Conifers

et al. 2017

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The New Zealand conifers (20 species of trees and shrubs in the Araucariaceae, Podocarpaceae, and Cupressaceae) are often regarded as ancient Gondwanan elements, but mostly originated much later. Often thought of as tall trees of humid, warm forests, they are present throughout in alpine shrublands, tree lines, bogs, swamps, and in dry, frost-prone regions. The tall conifers rarely form purely coniferous forest and mostly occur as an emergent stratum above evergreen angiosperm trees. During Maori settlement in the thirteenth century, fire-sensitive trees succumbed rapidly, most of the drier forests being lost. As these were also the more conifer-rich forests, ecological research has been skewed toward conifer dynamics of forests wetter and cooler than the pre-human norm. Conifers are well represented in the pollen record and we here we review their late Quaternary history in the light of what is known about their current ecology with the intention of countering this bias. During glacial episodes, all trees were scarce south of c. 40 • S, and extensive conifer-dominant forest was confined to the northern third of the North Island. Drought-and cold-resistant Halocarpus bidwillii and Phyllocladus alpinus formed widespread scrub in the south. During the deglacial, beginning 18,000 years ago, tall conifers underwent explosive spread to dominate the forest biomass throughout. Conifer dominance lessened in favor of angiosperms in the wetter western lowland forests over the Holocene but the dryland eastern forests persisted largely unchanged until settlement. Mid to late Holocene climate change favored the more rapidly growing Nothofagaceae which replaced the previous conifer-angiosperm low forest or shrubland in tree line ecotones and montane areas. The key to this dynamic conifer history appears to be their bimodal ability to withstand stress, and dominate on poor soils and in cool, dry regions but, in wetter, warmer locations, to slowly grow thorough competing broadleaves to occupy an exposed, emergent stratum where their inherent stress resistance ensures little effective angiosperm competition.

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The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

Cited by 64 publications

References 114 publications

The glacial geomorphology of the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, northeastern Patagonia (43°S, 71°W)

The glacial geomorphology of the Río Corcovado, Río Huemul and Lago Palena/General Vintter valleys, northeastern Patagonia (43°S, 71°W)

Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach

Palynology and the Ecology of the New Zealand Conifers

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