- Email: [email protected]
Glacial to glacial palaeoclimate and vegetation dynamics of the southern Beqaa valley, Lebanon
Abstracts / Quaternary International 279-280 (2012) 121–232
(2.7 Myr), and 390 m in total for the full glacial sequence (last 2.7 Myr). Likewise, calculations of mean erosion rates indicate 0.2 to 0.7 mm/yr of erosion for consecutive glacial cycles back to MIS 18, with a mean rate of 0.2 mm/yr for the period between MIS 18 and 2.7 Myr, and 0.3 mm/yr for the full glacial sequence. EFFECTS OF SUBSTRATUM LITHOLOGY AND BEDROCK STRUCTURES ON THE FORMATION OF GLACIAL TUNNEL VALLEYS: AN EXAMPLE FROM THE SOUTHERN NORTH SEA BASIN Adriaan Janszen. Delft University of Technology, Netherlands E-mail address: [email protected]
Deep and elongated incisions are a common feature of the northern European and North American lowlands. These so-called glacial tunnel valleys were formed under the Pleistocene ice-sheets by a combination of direct glacial erosion and meltwater. Previous workers have found that the formation of tunnel valleys is somehow controlled by bedrock structures and the substratum lithology in which they were carved. Until now however, many observations explaining how exactly the substratum influences geometry and orientation of the incisions appear to be wideranging and consequently a clear theory has not yet been formulated. The objective of this study is to investigate how tunnel valley genesis is controlled by the properties of the substratum and how it is influenced by salt diapirs as well as deep-seated faults and lineaments. A better understanding of this relationship would enhance our capability to predict the location and geometry of tunnel valleys in terms of width, depth and orientation. To these ends, high-resolution 3D seismic surveys and boreholes from the Dutch sector of the southern North Sea Basin were analysed. We found that the bases of tunnel valleys in the study area are often coinciding with reflectors that mark stratigraphic and lithological boundaries in the substratum. This effect can be so strong that the tunnel valley base slopes opposite to the flow direction. This study shows that the location and depth of tunnel valley incision varies as a function of the properties of the substratum as expressed by seismic facies and geophysical log variations. The geometry and orientation of tunnel valleys in the southern North Sea are therefore at least partially controlled by the occurrence of stratigraphic boundaries that coincide with important lithological contrasts. Moreover, faults and salt diapirs can have an additional effect on tunnel valley morphology as they significantly alter the geometry of stratigraphic boundaries and the hydraulic properties of the substratum. HISTORY FOR FUTURE: VEGETATION DYNAMICS OF AN ANDEAN BIODIVERSITY HOTSPOT IN SOUTHERN ECUADOR Nele Jantz. Georg-August-Univesity Göttingen, Department of Pa, Germany E-mail address: [email protected]
The region of the south Ecuadorian Andes has been world-renowned for its species richness since Humboldt first visited the country. Here, numerous ecosystems on an altitudinal gradient of more than 3000 m create a unique landscape pattern and enable an outstanding variety of vascular plant species to grow in this area. However, only little is known about the past environmental conditions of this hotspot of biodiversity. In the frame of the RU 816 of the Deutsche Forschungsgemeinschaft, vegetation, fire and landuse history have been studied in the Podocarpus National Park and its surroundings since 2003. A compilation and synthesis of these data can now give new insights into past and present vegetation changes in this region. Furthermore, multivariate analyses help to better understand the underlying causes of the landscape development and to see hidden relationships of vegetation and other environmental factors. Thus, a more reliable support can be given for the development of new and innovative conservation strategies for the protection of this unique ecosystem complex. CATASTROPHIC FANS FROM LOST MOUNTAIN CAVITIES IN THE ALPS - GROUNDTRUTHING AND RECONSTRUCTING "GADRIASPITZ", VINSCHGAU, ITALY David Jarman. Mountain Landform Research, United Kingdom E-mail address: [email protected]
221
A cluster of supposedly alluvial megafans exceeding 250 M m3 in volume in Vinschgau, South Tirol, Italian Alps, has been reattributed to catastrophic mountain collapses (Jarman, Agliardi and Crosta, in press); they show that the largest fan by area in the Alps at Malser Haide with a volume of w1650 M m3has a lost mountain source of comparable magnitude. Our model predicts a similar origin for the second largest fan at Allitz-Laas (Gadriamure). This is now groundtruthed, with abundant geomorphological evidence for a mega-collapse cavity. The lost mountain 'Gadriaspitz' can be reconstructed by well-constrained 'clonestamping' procedures and has a volume of w1800 M m3. This matches, with bulking-up, a fan volume recalculated from valley profiles of w2250 M m3, making it now possibly the largest in the Alps. With a substantial population of megafans and outsize fans in the Alps, this reinterpretation from incremental to catastrophic origins has implications for large-scale paraglacial mass movement causes, triggers and mechanisms. Fan cavities may be more prone to present debris-flow activity as they re-equilibrate. Future mega-hazard in similar morphological contexts cannot be dismissed. The apparent sparsity of such megafans in other deglaciated mountain ranges remains enigmatic. GLACIAL TO GLACIAL PALAEOCLIMATE AND VEGETATION DYNAMICS OF THE SOUTHERN BEQAA VALLEY, LEBANON Darren Jeffers. University of Oxford, United Kingdom E-mail address: [email protected]
A record of palaeoclimate and vegetation dynamics during MIS5e and its transition from MIS6 the Penultimate Glacial Maximum and into MIS5d the Last Glacial is presented for the Southern Beqaa Valley, Lebanon to answer the following questions: Is there correlation with AP/NAP phases identified in regional pollen records from Southern Europe or is AP present throughout the glacial to glacial cycle? Does the Southern Beqaa Valley act as a glacial refugia for Cedrus libani? Changes in d13C values, magnetic susceptibility and sediment type along with vegetation data are used to infer changes in climate at the boundaries from glacial to interglacial and to assess the level of climatic variability during the interglacial period. These data are used to assess whether the glacial and interglacial periods have high or low precipitation regimes and whether they are climatically stable. A chronology is provided by OSL dating of the quartz and feldspar fractions of the sediment matrix that enables comparison to other regional and global events. The fossil pollen record demonstrates significant fluctuations in the vegetation during this period. Tree taxa including Cedrus libani, Quercus spp. and Pinus spp. are present at the commencement of MIS5e and persist for the entire period together with significant levels of Gramineae and other non-arboreal pollen (NAP). The unique feature of this sequence is the absence of a shift from arboreal pollen (AP) to NAP at the start of this period, which is a common characteristic of the Eemian in Northern and Southern Europe. The continuous presence of Cedrus libani in this pollen record from the Penultimate Glacial Maximum through MIS5e and into the Last Glacial provides evidence of a glacial refugia for this species in the Southern Beqaa Valley. REGIONAL CORRELATION OF THE AD 1600 HUAYNAPUTINA TEPHRA: INTEGRATING ARCHAEOLOGICAL, ICE CORE AND LACUSTRINE RECORDS B.J.L. Jensen. University of Alberta, Canada E-mail address: [email protected]
The AD 1600 eruption of Huaynaputina is the largest historical eruption in the Andes. Documented by the Spanish, the eruption occurred over the months of February and March and consisted of several large eruptive phases that distributed ash-falls across southern Peru and northern Bolivia. Detailed geochemical analyses have been presented for proximal deposits of this eruption (e.g. Thouret et al. 2002), but there is little data available on the distal tephra record, despite its potential use as a stratigraphic marker for regional archaeological and paleoclimate studies. Here we present geochemical data from multiple distal tephra samples collected from ice cores, lake cores, exposures, and archaeological sites in Peru. Two ice-core samples from the Quelccaya and Corpuna glaciers appear to capture the entirety of the geochemical variation documented in proximal deposits. However, a higher SiO2 wt% population, attributable to
(2.7 Myr), and 390 m in total for the full glacial sequence (last 2.7 Myr). Likewise, calculations of mean erosion rates indicate 0.2 to 0.7 mm/yr of erosion for consecutive glacial cycles back to MIS 18, with a mean rate of 0.2 mm/yr for the period between MIS 18 and 2.7 Myr, and 0.3 mm/yr for the full glacial sequence. EFFECTS OF SUBSTRATUM LITHOLOGY AND BEDROCK STRUCTURES ON THE FORMATION OF GLACIAL TUNNEL VALLEYS: AN EXAMPLE FROM THE SOUTHERN NORTH SEA BASIN Adriaan Janszen. Delft University of Technology, Netherlands E-mail address: [email protected]
Deep and elongated incisions are a common feature of the northern European and North American lowlands. These so-called glacial tunnel valleys were formed under the Pleistocene ice-sheets by a combination of direct glacial erosion and meltwater. Previous workers have found that the formation of tunnel valleys is somehow controlled by bedrock structures and the substratum lithology in which they were carved. Until now however, many observations explaining how exactly the substratum influences geometry and orientation of the incisions appear to be wideranging and consequently a clear theory has not yet been formulated. The objective of this study is to investigate how tunnel valley genesis is controlled by the properties of the substratum and how it is influenced by salt diapirs as well as deep-seated faults and lineaments. A better understanding of this relationship would enhance our capability to predict the location and geometry of tunnel valleys in terms of width, depth and orientation. To these ends, high-resolution 3D seismic surveys and boreholes from the Dutch sector of the southern North Sea Basin were analysed. We found that the bases of tunnel valleys in the study area are often coinciding with reflectors that mark stratigraphic and lithological boundaries in the substratum. This effect can be so strong that the tunnel valley base slopes opposite to the flow direction. This study shows that the location and depth of tunnel valley incision varies as a function of the properties of the substratum as expressed by seismic facies and geophysical log variations. The geometry and orientation of tunnel valleys in the southern North Sea are therefore at least partially controlled by the occurrence of stratigraphic boundaries that coincide with important lithological contrasts. Moreover, faults and salt diapirs can have an additional effect on tunnel valley morphology as they significantly alter the geometry of stratigraphic boundaries and the hydraulic properties of the substratum. HISTORY FOR FUTURE: VEGETATION DYNAMICS OF AN ANDEAN BIODIVERSITY HOTSPOT IN SOUTHERN ECUADOR Nele Jantz. Georg-August-Univesity Göttingen, Department of Pa, Germany E-mail address: [email protected]
The region of the south Ecuadorian Andes has been world-renowned for its species richness since Humboldt first visited the country. Here, numerous ecosystems on an altitudinal gradient of more than 3000 m create a unique landscape pattern and enable an outstanding variety of vascular plant species to grow in this area. However, only little is known about the past environmental conditions of this hotspot of biodiversity. In the frame of the RU 816 of the Deutsche Forschungsgemeinschaft, vegetation, fire and landuse history have been studied in the Podocarpus National Park and its surroundings since 2003. A compilation and synthesis of these data can now give new insights into past and present vegetation changes in this region. Furthermore, multivariate analyses help to better understand the underlying causes of the landscape development and to see hidden relationships of vegetation and other environmental factors. Thus, a more reliable support can be given for the development of new and innovative conservation strategies for the protection of this unique ecosystem complex. CATASTROPHIC FANS FROM LOST MOUNTAIN CAVITIES IN THE ALPS - GROUNDTRUTHING AND RECONSTRUCTING "GADRIASPITZ", VINSCHGAU, ITALY David Jarman. Mountain Landform Research, United Kingdom E-mail address: [email protected]
221
A cluster of supposedly alluvial megafans exceeding 250 M m3 in volume in Vinschgau, South Tirol, Italian Alps, has been reattributed to catastrophic mountain collapses (Jarman, Agliardi and Crosta, in press); they show that the largest fan by area in the Alps at Malser Haide with a volume of w1650 M m3has a lost mountain source of comparable magnitude. Our model predicts a similar origin for the second largest fan at Allitz-Laas (Gadriamure). This is now groundtruthed, with abundant geomorphological evidence for a mega-collapse cavity. The lost mountain 'Gadriaspitz' can be reconstructed by well-constrained 'clonestamping' procedures and has a volume of w1800 M m3. This matches, with bulking-up, a fan volume recalculated from valley profiles of w2250 M m3, making it now possibly the largest in the Alps. With a substantial population of megafans and outsize fans in the Alps, this reinterpretation from incremental to catastrophic origins has implications for large-scale paraglacial mass movement causes, triggers and mechanisms. Fan cavities may be more prone to present debris-flow activity as they re-equilibrate. Future mega-hazard in similar morphological contexts cannot be dismissed. The apparent sparsity of such megafans in other deglaciated mountain ranges remains enigmatic. GLACIAL TO GLACIAL PALAEOCLIMATE AND VEGETATION DYNAMICS OF THE SOUTHERN BEQAA VALLEY, LEBANON Darren Jeffers. University of Oxford, United Kingdom E-mail address: [email protected]
A record of palaeoclimate and vegetation dynamics during MIS5e and its transition from MIS6 the Penultimate Glacial Maximum and into MIS5d the Last Glacial is presented for the Southern Beqaa Valley, Lebanon to answer the following questions: Is there correlation with AP/NAP phases identified in regional pollen records from Southern Europe or is AP present throughout the glacial to glacial cycle? Does the Southern Beqaa Valley act as a glacial refugia for Cedrus libani? Changes in d13C values, magnetic susceptibility and sediment type along with vegetation data are used to infer changes in climate at the boundaries from glacial to interglacial and to assess the level of climatic variability during the interglacial period. These data are used to assess whether the glacial and interglacial periods have high or low precipitation regimes and whether they are climatically stable. A chronology is provided by OSL dating of the quartz and feldspar fractions of the sediment matrix that enables comparison to other regional and global events. The fossil pollen record demonstrates significant fluctuations in the vegetation during this period. Tree taxa including Cedrus libani, Quercus spp. and Pinus spp. are present at the commencement of MIS5e and persist for the entire period together with significant levels of Gramineae and other non-arboreal pollen (NAP). The unique feature of this sequence is the absence of a shift from arboreal pollen (AP) to NAP at the start of this period, which is a common characteristic of the Eemian in Northern and Southern Europe. The continuous presence of Cedrus libani in this pollen record from the Penultimate Glacial Maximum through MIS5e and into the Last Glacial provides evidence of a glacial refugia for this species in the Southern Beqaa Valley. REGIONAL CORRELATION OF THE AD 1600 HUAYNAPUTINA TEPHRA: INTEGRATING ARCHAEOLOGICAL, ICE CORE AND LACUSTRINE RECORDS B.J.L. Jensen. University of Alberta, Canada E-mail address: [email protected]
The AD 1600 eruption of Huaynaputina is the largest historical eruption in the Andes. Documented by the Spanish, the eruption occurred over the months of February and March and consisted of several large eruptive phases that distributed ash-falls across southern Peru and northern Bolivia. Detailed geochemical analyses have been presented for proximal deposits of this eruption (e.g. Thouret et al. 2002), but there is little data available on the distal tephra record, despite its potential use as a stratigraphic marker for regional archaeological and paleoclimate studies. Here we present geochemical data from multiple distal tephra samples collected from ice cores, lake cores, exposures, and archaeological sites in Peru. Two ice-core samples from the Quelccaya and Corpuna glaciers appear to capture the entirety of the geochemical variation documented in proximal deposits. However, a higher SiO2 wt% population, attributable to