Abstract. High-altitude peatlands of the Andes still remain relatively unexploited although they offer an excellent opportunity for well-dated palaeoenvironmental records.To improve knowledge about climatic and environmental changes in the western Andes of southern Peru, we present a high-resolution record of the Cerro Llamoca peatland for the last 8600 years. The 10.5 m long core consists of peat and intercalated sediment layers and was examined for all kinds of microfossils. We chose homogeneous peat sections for pollen analysis at decadal to centennial resolution. The inorganic geochemistry was analysed in 2 mm resolution (corresponding > 2 years) using an ITRAX X-ray fluorescence core scanner.We interpret phases of relatively high abundances of Poaceae pollen in our record as an expansion of Andean grasslands during humid phases. Drier conditions are indicated by a significant decrease of Poaceae pollen and higher abundances of Asteraceae pollen. The results are substantiated by changes in arsenic contents and manganese/iron ratios, which turned out to be applicable proxies for in situ palaeoredox conditions.The mid-Holocene period of 8.6-5.6 ka is characterised by a series of episodic dry spells alternating with spells that are more humid. After a pronounced dry period at 4.6-4.2 ka, conditions generally shifted towards a more humid climate. We stress a humid/relatively stable interval between 1.8 and 1.2 ka, which coincides with the florescence of the Nasca culture in the Andean foothills. An abrupt turn to a sustained dry period occurs at 1.2 ka, which is contemporaneous with the demise of the Nasca/Wari society in the Palpa lowlands. Markedly drier conditions prevail until 0.75 ka, providing evidence of the presence of a Medieval Climate Anomaly. Moister but hydrologically highly variable conditions prevailed again after 0.75 ka, which allowed re-expansion of tussock grasses in the highlands, increased discharge into the Andean foreland and resettling of the lowlands during this so-called late Intermediate Period (LIP).On a supraregional scale, our findings can ideally be linked to and proved by the archaeological chronology of the Nasca-Palpa region as well as other high-resolution marine and terrestrial palaeoenvironmental records. Our findings show that hydrological fluctuations, triggered by the changing intensity of the monsoonal tropical summer rains emerging from the Amazon Basin in the north-east, have controlled the climate in the study area.
Cushion peatlands are typical features of the high altitude Andes in South America. Due to the adaptation to difficult environmental conditions, they are very fragile ecosystems and therefore vulnerable to environmental and climate changes. Peatland erosion has severe effects on their ecological functions, such as water storage capacity. Thus, erosion monitoring is highly advisable. Erosion quantification and monitoring can be supported by high-resolution terrestrial Light Detection and Ranging (LiDAR). In this study, a novel Geographic Information System (GIS)-based method for the automatic delineation and geomorphometric description of gullies in cushion peatlands is presented. The approach is a multi-step workflow based on a gully edge extraction and a sink filling algorithm applied to a conditioned digital terrain model. Our method enables the creation of GIS-ready polygons of the gullies and the derivation of geomorphometric parameters along the entire channel course. Automatically derived boundaries and gully area values correspond to a high degree (93%) with manually digitized reference polygons. The set of methods developed in this study offers a suitable tool for the monitoring and scientific analysis of fluvial morphology in cushion peatlands.
Abstract. Within palaeoenvironmental studies, high-altitude peatlands of the Andes still remain relatively unexploited, although they offer an excellent opportunity for high-resolution chronologies, on account of their high accumulation rates and abundant carbon for dating. Especially in the central Andes, additional high-quality proxy records are still needed due to the lack of continuous and well-dated records, which show a significant variability on sub-centennial to decadal precision scales. To widen the current knowledge on climatic and environmental changes in the western Andes of southern Peru, we present a new, high-resolution 8600 year-long record from Cerro Llamoca peatland, a high-altitude Juncaceous cushion peatland in the headwaters of Río Viscas, a tributary to Río Grande de Nasca. A 10.5 m core of peat with intercalated sediment layers was examined for all kinds of microfossils, including fossil charred particles. We chose homogeneous peat sections for pollen analysis at a high temporal resolution. The inorganic geochemistry was analysed in 2 mm resolution using an ITRAX X-ray fluorescence (XRF) core scanner. We interpret the increase of Poaceae pollen in our record as an expansion of Andean grasslands during humid phases. Drier conditions are indicated by a significant decrease of Poaceae pollen and higher abundances of Asteraceae pollen. The results are substantiated by changes in arsenic contents and manganese/iron ratios, which turned out as applicable proxies for in situ palaeo-redox conditions. The mid-Holocene period of 8.6–5.6 ka is characterized by a series of episodic dry spells alternating with spells that are more humid. After a pronounced dry period at 4.6–4.2 ka, conditions generally shifted towards a more humid climate. We stress a humid/relatively stable interval between 1.8–1.2 ka, which coincides with the florescence of the Nasca culture in the Andean foreland. An abrupt turnover to a sustained dry period occurs at 1.2 ka, which coincides with the collapse of the Nasca/Wari society in the Palpa lowlands. Markedly drier conditions prevail until 0.75 ka, providing evidence for the presence of a Medieval Climate Anomaly. Moister but hydrologically highly variable conditions prevailed again after 0.75 ka, which allowed the re-expansion of tussock grasses in the highlands, increased discharge into the Andean foreland and the re-occupation of the settlements in the lowlands during this so-called Late Intermediate Period. On a supraregional scale, our findings can ideally be linked to and proofed by the archaeological chronology of the Nasca-Palpa region as well as other high-resolution marine and terrestrial palaeoenvironmental records. Our findings show that hydrological fluctuations, triggered by the changing intensity of the monsoonal tropical summer rains emerging from the Amazon Basin in the north-east, have controlled the climate in the study area.
A multi‐method research design based on terrestrial laser scanning, GIS, geophysical prospecting (electrical resistivity tomography, refraction seismics) and sedimentology is applied for the first time to investigate enclosed karst depressions in an integrated way. Fusing multi‐resolution surface and subsurface geodata provides profound insights into the formation, geometry and geomorphologic processes of dolines. The studied landforms, which are located in the Dikti Mountains of East Crete, are shown to be filled by loose sediments of thicknesses of up to 30 m that mainly consist of fine‐grained material overlying solid bedrock at depths below 35 to 45 m. By combining subsurface observations with geomorphometric calculations, local doline genesis can be traced back to initial collapse of fractured bedrock followed by subsequent infilling with colluvials. In order to define crucial methodological requirements and guidelines for data fusion, both the impact of different elevation models and the influence of data resolution are assessed. Surface volumes of depressions derived by the digital surface model are 7–21% higher than the results obtained from the terrain model due to vegetation. Similarly, estimates of infill volume calculated on the basis of geophysical outcomes and elevation data differ by up to 13%. Calculations of the landforms' current volumes (i.e. total surface and subsurface volume), however, are fairly insensitive to raster resolution. Hence, the distinct geomorphologic properties of landforms (e.g. shape, terrain roughness, slope inclination) substantially determine the geomorphometric analysis of both surface and subsurface data. As shown by the findings, data fusion to integrate digital terrain, geophysical and sedimentological datasets of varied resolutions benefits geomorphologic studies and helps provide a comprehensive image of landforms. Copyright © 2013 John Wiley & Sons, Ltd.
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