Springer Science and Business Media LLC

We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by 210Pb measurement and AMS 14C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years.

The stratigraphic, geochemical, and organic matter study of the late Holocene San Nicolás succession of the Cauca paleolake (Santa Fé–Sopetrán pull-apart basin) in the middle Cauca Valley, northern Colombia, suggests that it was deposited in a ria lake environment, at sedimentary accumulation rates in excess of 600 cm ky−1 between ~3500 and ~500 yr BP. Laminated deposition occurred, first under igapo (black-water), and then under varzea (white-water) conditions. The transition occurred ca. 3000 yr BP, a time of major change in El Niño/Southern Oscillation (ENSO) behavior in the Cariaco Basin, thus reflecting the southern migration of the intertropical convergence zone and intensified rain upstream the Cauca Valley. A second, but less conspicuous change occurred ca. 2000 yr BP, which apparently corresponds to the intensified and/or more frequent ENSO activity in the Galapagos Islands. Our contribution describes, for the first time, a ria lake sedimentary succession from the northern Andes and demonstrates the high potential of these hitherto undervalued deposits for the reconstruction of the paleohydrological history of the northern Andes.

Faecal stanols in lake sediments have been used as a proxy for human populations in the past in a variety of contexts, with the assumption that variability in faecal stanol concentration or ratios is a reliable proxy for relative catchment-scale human populations. Despite that, the specific controls on faecal stanol concentrations and ratios in lake sediments remain poorly understood. In this study we analyse faecal stanol concentrations in lake surface sediments across Guatemala and the Yucatán Peninsula of Mexico in order to constrain geographical and biogeochemical variables controlling stanol concentrations and ratios in lake sediments in this region. We propose and test the hypothesis that the stanol ratios coprostanol:(coprostanol + stigmastanol) and coprostanol:(coprostanol + cholestanol) scale according to the proximity to and size of nearby population centres. The key controls on stanol concentrations that we identify are the proximity to human population centres and the human population within 5 km of the sampling point. Based on a transect across Lake Petén Itzá, the ratio coprostanol:(coprostanol + cholestanol) does not appear to be an accurate proxy for proximity to human population centres, nor does it correlate with catchment human population. We suggest that normalising stanol concentrations to TOC is an appropriate way to take into account the effects of mineral dilution as well as the potential effects of organic matter deposition and preservation, and that the ratio coprostanol:(coprostanol + stigmastanol) does not scale with human population but may be an effective approach to determine the relative contribution of coprostanol-producing mammals and herbivores. Further, we discuss the current limitations of the proxy as well as its future directions, including the implications of our results for sediment core siting, the use of stanol ratios in palaeolimnology, as well as the storage, transport, and diagenesis of stanols.

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lake-water pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9% and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r2 = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r2 = 0.75, RMSEP = 0.96 °C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent cross-validation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the ice-free seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.

Wetland carbon storage is an important and environmentally sensitive ecosystem service. Carbon burial in the floodplain lakes of the Pantanal (tropical South America) appears to have varied during the late Quaternary, but several paleolimnological studies have recorded unusually high sediment organic carbon content from ~ 7.3 to 6.0 cal kyr BP in lakes connected to the Upper Paraguay River. We conducted a multi-indicator (phytoliths, sponge spicules, and geochemistry) study of a sediment core from Lake Cáceres (Bolivia), and found evidence for enhanced organic carbon burial during the middle Holocene that provides insights into the flooding history of the Upper Paraguay River. δ13Corg and C/N data suggest that organic matter deposited at that time in Lake Cáceres was from macrophytes. Similar datasets from three other floodplain lakes are consistent with this finding. We suggest that enhanced carbon burial occurred when lake levels declined under relatively dry climate conditions, which increased the littoral area at the expense of open water and captured floating macrophyte islands. This study sheds new light on hydroclimate controls on carbon cycling in the Pantanal wetlands, and improves interpretations of geochemical measures on bulk organic matter in floodplain lake cores.

The water level of the Lake Michigan basin is currently 177 m above sea level. Around 9,800 14C years B.P., the lake level in the Lake Michigan basin had dropped to its lowest level in prehistory, about 70 m above sea level. This low level (Lake Chippewa) had profound effects on the rivers flowing directly into the basin. Recent studies of the St. Joseph River indicate that the extreme low lake level rejuvenated the river, causing massive incision of up to 43 m in a valley no more than 1.6 km wide. The incision is seen 25 km upstream of the present shoreline. As lake level rose from the Chippewa low, the St. Joseph River lost competence and its estuary migrated back upstream. Floodplain and channel sediments partially refilled the recently excavated valley leaving a distinctly non-classical morphology of steep sides with a broad, flat bottom. The valley walls of the lower St. Joseph River are 12–18 m tall and borings reveal up to 30 m of infill sediment below the modern floodplain. About 3 × 108 m3 of sediment was removed from the St. Joseph River valley during the Chippewa phase lowstand, a massive volume, some of which likely resides in a lowstand delta approximately 30 km off-shore in Lake Michigan. The active floodplain below Niles, Michigan, is inset into an upper terrace and delta graded to the Calumet level (189 m) of Lake Chicago. In the lower portion of the terrace stratigraphy a 1.5–2.0 m thick section of clast-supported gravel marks the entry of the main St. Joseph River drainage above South Bend, Indiana, into the Lake Michigan basin. This gravel layer represents the consolidation of drainage that probably occurred during final melting out of ice-marginal kettle chains allowing stream piracy to proceed between Niles and South Bend. It is unlikely that the St. Joseph River is palimpsest upon a bedrock valley. The landform it cuts across is a glaciofluvial-deltaic feature rather than a classic unsorted moraine that would drape over pre-glacial topography.

Paleoclimatic records from the East Asian summer monsoon (EASM) margin are regarded as a direct reflection of the intensity and northern extent of the EASM. Here, we focus on reconstructing climatic evolution over the past 1800 years from two alkaline lakes, Chagan Nuur and Sangin Dalai Nuur, in southern Inner Mongolia. With age control provided by 13 Accelerator Mass Spectrometry radiocarbon ages and 210Pb/137Cs dating, analyses of grain size, X-ray diffraction, magnetic susceptibility, carbonate content, total nitrogen, total organic carbon and the stable isotopic composition of carbon (δ13C) and nitrogen (δ15N) in sedimentary organic matter and calculation of organic carbon to nitrogen atomic ratios have been performed to investigate hydrodynamic processes, ecological conditions and corresponding lake-level fluctuations, in response to climate change. Our results show that the lake level of Changan Nuur frequently fluctuated since 546 CE, with four centennial-scale intervals of lake expansion at around 755, 1178, 1350 CE, and after 1950 CE, and one interval of lake recession from 1593 to 1782 CE. Sangin Dalai Nuur experienced mainly low-amplitude lake-level fluctuations since 212 CE, except for severe lake shrinkage from 1417 to 1872 CE. A regional comparison shows that three warm and humid intervals (640–800 CE, 1088–1288 CE, and after 1950 CE) and one cold and dry interval (1417–1872 CE) recognized from our records could correspond to the Sui-Tang Warm Period, the Medieval Climate Anomaly, the Current Warm Period and the Little Ice Age, respectively. Moreover, our results are roughly synchronous with moisture conditions revealed by proxy records from monsoonal northern China, demonstrating that the highly variable lake levels and climatic conditions in southern Inner Mongolia were controlled by centennial-scale variations in EASM over the past 1800 years.

Milltown Lake is located in the Irish drumlin belt where small lakes are interspersed amongst rolling hills. Because of poor drainage characteristics of soils in this region, grassland agriculture dominates, with beef rearing and dairying as the main agricultural enterprises. We used paleolimnological techniques in conjunction with export coefficients to investigate the relationship between historical development of eutrophication in the lake and changes in nutrient loading from the watershed. Sediment cores representing the period ~1970 to 2008 were analysed for fossil pigments using high performance liquid chromatography to provide proxies for changes in abundance of the main algal groups. Geochemical variables, including total phosphorus, were also analysed, and nutrient loading was estimated using historical data. Concentrations of all major pigments increased up-core, as did nutrient loading from the watershed, between ~1970 and 2008. Export coefficient estimates showed that, on average, 82.2 % of P loads were attributable to two sources, cattle and grassland. More specifically, the P load from cattle was strongly correlated to overall algal abundance, whereas the P load from people was negatively related to algal abundance indicators. Results also suggested that artificial fertilisers were less important drivers of algal abundance than organic manure from cattle. These results highlight the potential problems associated with farming practices that generate large amounts of organic manure, especially when located on poorly drained and steeply sloping lands. The findings contribute to the management of such small lakes, particularly given the potential conflict between increasing agricultural output and the implementation of the European Union Water Framework Directive on a national scale.