Lacustrine Archives Research Articles

Branched GDGT-based temperature calibrations from Central European lakes

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are common in lake sediments, where they are frequently employed to infer mean annual air temperatures (MAAT) or air temperatures of months above freezing (MAF) using the MBT'5Me lipid paleothermometer. The reliable reconstruction of such temperatures, however, requires robust calibration functions. Here, we investigated brGDGT distributions in surface sediments from 41 freshwater lakes located along an altitudinal gradient across the Alps (Central Europe) and spanning a MAAT range from 1.3 to 12.9 °C. Linear regression analysis demonstrates that fractional abundances of brGDGTs are strongly correlated with MAAT and MAF allowing to establish regional MBT'5Me-based transfer functions: MAAT (°C) = −2.19 + 31.91 × MBT'5Me (r2 = 0.72; RMSE = 1.51 °C) and MAF (°C) = 4.81 + 15.64 × MBT'5Me (r2 = 0.64, RMSE = 0.92 °C). Stepwise forward selection yielded the following, alternate temperature calibrations: MAAT (°C) = 7.11 + 67.66 × Ib – 13.54 × IIIa (r2 = 0.72; RMSE = 1.47 °C) and MAF (°C) = 5.19 + 16.22 × Ia (r2 = 0.66; RMSE = 0.98 °C). Our results demonstrate that the above calibration functions allow precise temperature reconstructions using lacustrine sediment records. However, our data also show that high-altitude lakes are more prone to warm bias and that lakes characterized by comparatively high abundances of 6-methyl brGDGTs show aberrant behaviors with temperature offsets up to ∼7 °C. Determining the IR6Me, as an independent control complementary to the MBT'5Me, is thus essential to validate the robustness of brGDGT-based temperature reconstructions of past climates. A cut-off value of 0.50 for the IR6Me is here proposed, after which MBT'5Me-reconstructed MAATs from lacustrine archives should be regarded as unreliable.

Holocene Hydroclimatic Changes in Northern Peloponnese (Greece) Inferred from the Multiproxy Record of Lake Lousoi

This research presents the paleoenvironmental evolution of a drained lake at the Lousoi plateau (northern Peloponnese), for the last 10,000 years, through the study of a 7 m depth core. Analyses conducted on the core include grain size, TOC, TN, pH, EC, total carbonates (%), magnetic susceptibility measurements, XRF analysis, and radiocarbon dating. Our paleoenvironmental reconstruction was based on geochemical proxies’ distribution in the core, combined with sediment physical and textural characteristics and later comparison between additional lacustrine archives from northern Peloponnese. From 10,900 to 7700 cal BP lacustrine, organic-rich deposits were recognized, reflecting increased lake water levels. Wet climatic conditions seem to have prevailed during this phase, interrupted by a dry pulse at 9400 cal BP. Transition to more shallow waters was marked at 8200 cal BP due to increased sediment deposition in the lake, with the environmental status shifting to a more oxygenated phase. Overall, wet conditions prevailed in this period and are in good agreement with regional records. In the Late Holocene period, the lake seems to have been highly affected by pedogenic processes, and thus, it was difficult to distinguish paleoclimatic/paleoenvironmental signals.

Middle Pleistocene environments, landscapes and tephrostratigraphy of the Armenian Highlands: evidence from Bird Farm 1, Hrazdan Valley

ABSTRACTThe significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto‐tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale.

The reconstruction of an abandoned historical reservoir network in a continental temperate climate region using a multi-method approach

Reservoirs represent a specific environmental component in many parts of the Earth, especially where water supply is limited. As is the case of the Moldavian hilly area, due to its dryness, the inhabitants created an extensive network of reservoirs since the medieval period, in the proximity of the settlement network. Over time, many dams were abandoned, while others have been relocated with impressive dynamics at a historical scale. In this paper, by analyzing old maps, LiDAR high-res DEMs, ERT surveys, and sediments, we have reconstructed the reservoir network's expansion in the last century at a regional scale and investigated the main geomorphologic characteristics of dams and associated landforms. In Jijia catchment (3386 km2) we found a total number of 1351 dams, of which 832 abandoned. 495 reservoirs were recognized on different topo maps dating from the 20th century, while 337 have been identified on DEMs. Two reservoirs were investigated in detail by field surveys, ERT surveys, profile digging, sediment analysis, and micro-sedimentological study, confirming lacustrine deposits according to the topographic reconstructions based on high-resolution LiDAR DEMs. These sedimentary lacustrine archives can substantially contribute to detailed paleoclimatic, paleohydrologic, and paleovegetation reconstruction in the study area.

Alluvial records of the African Humid Period from the NW African highlands (Moulouya basin, NE Morocco)

This paper presents Early to Late-Holocene sedimentary deposits from the Moulouya catchment, the main Mediterranean river basin of Morocco. Within this region, recent studies have focused particularly on marine or lacustrine archives. Studies on fluvial archives are thus important for improving our understanding of palaeoenvironmental responses to Holocene climatic changes at regional and supra-regional scales. Here, we studied alluvial archives from two basins 300 km apart in the mid-Moulouya basin and High Plateaus region located in the rarely studied NW African highlands, which are currently defined by arid and cold climatic conditions. Strong similarities between these deposits in terms of morpho-pedosedimentary and chronostratigraphical evolution demonstrate a regional morphogenic pattern controlled by Holocene climatic changes. Using a multi-proxy approach, we document rapid palaeoenvironmental changes and orbital-scale morphogenic changes. Four particular phases of regional geomorphic stability have been dated to ca. 10800–10500, 10200–9900, 9300, and 8900 cal. BP. Enhanced flooding periods that reflect times of climatic aridification may correlate with Early and Mid-Holocene Rapid Climatic Changes, especially during the 9.2 ka event. Furthermore, the Moulouya alluvial archives record the development of an extensive wetland formation and tufa sedimentation within the alluvial plains between ca. 10.8 to 6-5 cal ka BP. This formation is recognised at a regional scale across the upper and mid-Moulouya catchments, whereas it is missing from other Moroccan fluvial archives. These lasting humid climatic conditions (ca. 10.8–6/5 ka cal. BP.) are consistent with those recorded in the sub-Saharan records during the last African Humid Period (AHP), and suggest a potential linkage between the NW African highlands and the Saharan domain. Hence, we assume that this fluvio-palustrine wetland formation located at 32°–34°N is consistent with the northern archives recording AHP wet conditions.

A 700-year multiproxy reconstruction on the Argentinian Pampas inferred from the sediments of Laguna Blanca Grande

The Pampean region is a crucial area to obtain sensitive paleoclimatic lacustrine archives due to the presence of shallow environments in a territory non impacted by humans until the last centuries. In this study, we provide a paleoecological reconstruction for the last ca. 700 years based on a multiproxy lacustrine record from Laguna Blanca Grande, in Olavarría (Buenos Aires, Argentina). Our inferences, which were based on sedimentary properties, diatom, cladoceran and ostracod assemblages, offered interesting information about hydroclimatic variability and nutrient increase. Changes in relative abundances on diatoms, specifically on Aulacoseira granulata and Aulacoseira granulata var. angustissima and fragilariods, were used to infer shifts in nutrient conditions. The remainder proxies together indicated small lake level changes. Reconstructed hydroclimatic conditions in Laguna Blanca Grande are consistent with previous paleoecological inferences indicating a humid phase around ca. AD 1450 and progressive drier conditions ca. AD 1530–1900. A flood gate construction and an increase of nutrients in the lake revealed a higher human pressure due to population increase and land-use changes during the last century. Further studies on taxonomy and autecology of microcrustaceans are needed to effectively unlock the information contained in biological proxies from Sudamerican records.

Reconstruction of palaeoenvironmental variability based on an inter-comparison of four lacustrine archives on the Peloponnese (Greece) for the last 5000 years

Abstract. A high quantity of well-dated, high-resolution, continuous geoarchives is needed to connect palaeoenvironmental reconstructions with socio-environmental and cultural transformations in a geographically heterogeneous region such as southern Greece. However, detailed and continuous palaeoclimatic and palaeoenvironmental archives from the NE Peloponnese are still sparse. Here, we present two new palaeolake archives of Pheneos and Kaisari covering the last 10 500 and 6500 years, respectively. For the last 5000 years, we compare them with sediment records from adjacent Lake Stymphalia and the Asea valley by applying the same set of sedimentological, geochemical, and statistical analyses to all four lacustrine archives. Continuous geochemical X-ray fluorescence (XRF) core scanning records provide evidence for hydrological variations and environmental changes since the Early Helladic period (5050 BP), the beginning of the Bronze Age in Greece. We hereby focus on different spatial scales to estimate the validity range of the proxy signals. Ten elements were selected (Al, Si, K, Ca, Ti, Mn, Fe, Rb, Sr, Zr) for a principal component analysis. The clr(Ca∕Ti) was chosen as the most meaningful proxy, reflecting varying input of carbonaceous vs. clastic input, which may be linked to changes in the hydrological conditions. Our results show phases when permanent lake water bodies existed (ca. 5000–3600 cal BP) as well as phases with periodic desiccation of the lakes during younger times. While Pheneos and Kaisari show a drying trend during the transition phase from the Late Helladic period to the Proto-Geometric period (ca. 3200–2800 cal BP), Stymphalia and Asea show a rather short dry peak around 3200 cal BP followed by a wetter phase. Although all our geoarchives show evidence for drier phases, their timing and duration display considerable site-to-site differences which may be explained by site-specific responses in individual ecosystems. Age uncertainties, however, may likewise explain some deviations, as the dating is based on bulk sediment samples including potential unknown reservoir effects. The high regional geographical diversity within the Peloponnese combined with the dating challenges in the limestone-rich area and the variation in our data testify that any hypothetical mono-causal connection between palaeoenvironmental changes in a single geoarchive and contemporaneous societal transformations across the Peloponnese would be an oversimplification.

Magnetostratigraphy and magnetic susceptibility of the best developed Pleistocene loess-palaeosol sequences of Ukraine: implications for correlation and proposed chronostratigraphic models

We provide a revised magnetostratigraphy and magnetic susceptibility stratigraphy of the most complete and thickest (to nearly 60 m) loess-palaeosol sequences in Ukraine spanning the past 1 My: the Roksolany (Black Sea Lowland) and Vyazivok (Dnieper Lowland) sections. The Matuyama–Brunhes boundary has been detected in both sequences in stratigraphically different palaeosol units according to current regional chronostratigraphic schemes. Hypotheses of a large magnetic lock-in depth at Vyazivok and lithostratigraphic incompleteness at Roksolany do not resolve this inconsistency. Instead, new chronostratigraphic models following the Chinese loess designation system, which are supported by correlation of the magnetic susceptibility records with the marine isotope record and established magnetostratigraphic control points, are proposed. We conclude that the Matuyama–Brunhes reversal in the Roksolany and Vyazivok sections belongs to the same palaeosol unit, the Shyrokyne (according to our nomenclature, the U-S7), which corresponds to MIS 19. This novel interpretation resolves the inconsistency of the stratigraphic position of the Matuyama–Brunhes boundary in Ukrainian loess, ends long-standing debate regarding the chronostratigraphy of the Roksolany section, and allows precise correlation of the most representative loess-palaeosol sequences of Ukraine with those in the Danube Basin and the Chinese Loess Plateau. It is considered that the Roksolany Tephra in MIS 6 loess unit can be related to the L2 Tephra which is widely distributed in southeastern European loess records and lacustrine archives. In the light of our results, the Roksolany sequence may serve as a national lectostratotype of the Middle Zavadivka (U-L4) loess unit corresponding to MIS 10. Additionally, a generalized pedostratigraphic column of the past 1 My for central and southern Ukraine has been constructed and correlated with the Hungarian, Serbian and Chinese loess stratigraphies, as well as with the marine isotope record down to MIS 25.

Subaerially preserved remains of pine stemwood as indicators of late Holocene timberline fluctuations in Fennoscandia, with comparisons of tree-ring and 14C dated depositional histories of subfossil trees from dry and wet sites

Collections of subfossil wood provide useful evidence of past vegetation and climatic variability. Here, 172 samples of Pinus sylvestris stemwood found either as standing (snags) or fallen tree trunks (coarse woody debris) from forested and treeline (ecotone) sites in northwest Finnish Lapland was compared with living tree data representing 1071 P. sylvestris trees growing in the region. The number of subfossil samples was found to increase in both the ecotone and forested sites since AD 1000. Divergent courses of de positional histories were evident with the reversal of the trend in subfossil number circa AD 1600 in the ecotone sites and circa AD 1800 in the forested sites. Comparisons with subfossil P. sylvestris trees from lacustrine archives in the same region showed synchronous accumulation pulses around AD 1100, AD 1300, AD 1500 and AD 1700. Moreover, the percentage of ecotone samples showed a long-term decline since AD 1000, in agreement with previously published records of pine pollen influx and subfossil P. sylvestris trees from lacustrine archives. Two major phases of increased pine recruitment across the dryland sites in Finnish Lapland, Scandes Mountains and Kola Peninsula were evident for AD 1000–1200 and AD 1400–1600 periods. This suggests that the pine recruitment was generally increased during the Medieval Climate Anomaly (MCA) and during the fifteenth and sixteenth centuries AD, and impaired during the cold phases of the two-stage Little Ice Age. Living tree data demonstrated latitudinal and altitudinal advances and intensified regeneration of treeline P. sylvestris since AD 1930s.

Pastoralism increased vulnerability of a subalpine catchment to flood hazard through changing soil properties

Soil erosion is strongly linked to both precipitation patterns and land-use. We examine the effects of erosion and its drivers (i.e. human or/and climate) on soil evolution from the study of lacustrine archives in the northern French Alps. Multi-proxy analyses of the Lake Gers sediment sequence combined with the study of soils and rocks of its catchment allowed to reconstruct its evolution over the past 4.6 kyr. This included 14C dating, short-lived radionuclides, geochemistry, loss on ignition, grain-size analyses, as well as plant and mammal DNA analyses. A total of 127 instantaneous deposits were identified among the continuous sedimentation in the lake and 93 were interpreted as flood deposits. Erosion was quantified for the whole catchment considering both the continuous sedimentation and the flood deposit thicknesses.The catchment is mainly formed by andesitic sandstones over which Andosols and Podzols can develop. However, low weathered materials from colluviation constitute the main input to the lake.Four main phases of changes in soil weathering were recorded by increases in K2O/TiO2 ratios, associated with an increase in both erosion and flood-frequency. Two phases were associated with climate cooling in the Western Alps, from 2.65 to 2.5 and from 1.45 to 1.3 cal kyr BP. The two others (1.9–1.75 and 0.9–0.4 cal kyr BP) were triggered with deforestation, with cow grazing during the Roman period, and with grazing of cows, sheep and goats during the Medieval period, amplified by the onset of the Little Ice Age. The increase in erosion and flood frequency after 950 cal yr BP indicates substantial damages to soils of the catchment including increase of their erodibility over the last millennia.

Multi-Substrate Radiocarbon Data Constrain Detrital and Reservoir Effects in Holocene Sediments of the Great Salt Lake, Utah

ABSTRACTThe radiocarbon (14C) content of simultaneously deposited substrates in lacustrine archives may differ due to reservoir and detrital effects, complicating the development of age models and interpretation of proxy records. Multi-substrate14C studies quantifying these effects remain rare, however, particularly for large, terminal lake systems, which are excellent recorders of regional hydroclimate change. We report14C ages of carbonates, brine shrimp cysts, algal mat biomass, total organic carbon (TOC), terrestrial macrofossils, andn-alkane biomarkers from Holocene sediments of the Great Salt Lake (GSL), Utah.14C ages for co-deposited aquatic organic substrates are generally consistent, with small offsets that may reflect variable terrestrial organic matter inputs to the system. Carbonates and long-chainn-alkanes derived from vascular plants, however, are ∼1000–400014C years older than other substrates, reflecting deposition of pre-aged detrital materials. All lacustrine substrates are14C-depleted compared to terrestrial macrofossils, suggesting that the reservoir age of the GSL was > 1200 years throughout most of the Holocene, far greater than the modern reservoir age of the lake (∼300 years). These results suggest good potential for multi-substrate paleoenvironmental reconstruction from Holocene GSL sediments but point to limitations including reservoir-induced uncertainty in14C chronologies and attenuation and time-shifting of some proxy signals due to detrital effects.

Tentative integration of paleoseismic data from lake sediments and from nearby trenches: the central section of the Boconó Fault (northern Venezuela)

The right-lateral strike slip Boconó Fault (Mérida Andes, northern Venezuela) accommodates an important part of the South-American Plate northern transform boundary. Along its central portion, preserved post-LMG lake fills are intersected by two surface-reaching active traces which could be trenched just beside. Outcropping and cored lacustrine sedimentary archives are combined with trench data in order to achieve a Holocene paleoseismicity record for a 7 km-long segment. For lakes sediments, several types of sedimentary “events” were taken into account as co-seismic: mass wasting on deltaic foreset, liquefaction and slumping, reflected tsunami effects, re-suspension, abrupt change in sedimentary dynamics and sources, abrupt emptying and lake surface changes. Time coincidences between two lacustrine archives and two trenches can be proposed for the last 10 kyr BP. Among a total of 24 events, 13 events are detected in two sites, 3 events in 3 sites. 9 possible correlations concern separate traces while 4 concern the same trace; a relay between the activity of the two traces is also deduced. This combination of surveys both reinforces and completes the trenches results, leading to a better knowledge of local to regional seismic hazard. Nevertheless, the total information results probably incomplete and/or biased. The co-seismic origin of lacustrine fills disturbances evidenced but the associated archive is incomplete and/or biased due to: changing recording potential through time, possible impacts by strong distant earthquakes. Trenches data appear to fill lacustrine “gaps” but with a number of events possibly overestimated if all ruptures and associated 14C data are considered as representing separated earthquakes.

Holocene land cover change in south-western Amazonia inferred from paleoflood archives

This study provides new data on the evolution of the landscape in south-western Amazonia during the Holocene and the impact of climate change and fluvial dynamics on the region's ecosystems. South-western Amazonia is covered by an extensive seasonally flooded savannah, known as the Llanos de Moxos. Severe drought during the southern hemisphere winter, followed by months of permanent waterlogging, means that forests only grow on the most elevated parts of the landscape, mostly river and paleoriver levees and crevasse splays. Paleoclimate reconstructions from surrounding areas show that a shift to wetter conditions at around 4 kyr BP caused an increase in forest cover. However, the impact that this change in climate had on the landscape of the Llanos de Moxos is unknown. Published lacustrine archives from the area only cover the last 2 kyr. Here we present new data from the analysis of paleosols located along a 300 km transect across the central Llanos. The analyses of stable carbon isotopes, from 36 paleosols, and biogenic silica, from 29 paleosols, show that the patchwork of forests and savannahs that we see today was established after the 4 kyr BP climate change. During the dry period between 8 and 4 kyr BP, most of the central Llanos de Moxos, nowadays covered with seasonally flooded savannah, were covered by Cerrado-like savannah in the west and by forest in the east. However, results also suggest that, at both regional and local scales, vegetation cover has been influenced by changes in topography resulting from the region's river dynamics.

Aspects of late Quaternary geomorphological development in the Khangai Mountains and the Gobi Altai Mountains (Mongolia)

The reconstruction of geomorphological processes as a result of environmental change is approached by investigating and dating some fluvial, aeolian and lacustrine archives at specific locations that form a N-S basin and range transect across the Khangai Mountains south to the eastern Gobi Altai mountains in Mongolia. Geomorphological processes varied a) spatially with different climatic conditions and vegetation cover in relation to different elevation and latitude and b) temporally due to climatic shifts during the late Quaternary. In total, 15 sections from three distinct sub-regions along that transect were dated by 22 OSL ages. The Khangai Mountain sub-region exhibits mainly late Glacial to Holocene aeolian silty to sandy cover sediments mainly in the upper catchment reaches (>1800 m a.s.l.). Sections in the northern and central Gobi represent river terraces and alluvial fans in basin areas as well as aeolian sediments in the mountains above 2200 m a.s.l. The oldest terrace surface found in this study (T2; NGa1) dates to the penultimate Glacial cycle. The T1 terrace surfaces, on the northern Khangai Mountain front and in the central Gobi sub-region yield a maximum accumulation during the global Last Glacial Maximum (gLGM) and late Glacial time. During the gLGM phase represents rather sheetflow dominated transport built the alluvial fans and in late Glacial times the sediments exhibit more debrisflow controlled accumulation. Incision, forming the T1-terrace edges is therefore, supposed for the Pleistocene-Holocene transition and subsequent early Holocene. The geomorphic evidence is interpreted as stronger fluvial morphodynamics induced by enhanced humidity under beginning interglacial conditions. These processes coincided with the development of aeolian mantles at higher altitudes in the Khangai and Gobi Altai mountains where higher temperatures and humidities supported the formation of a vegetation cover, that served as a dust trap at least since late Glacial times and reduced the sediment supply on the alluvial fans.

Late Glacial erosion and pedogenesis dynamics: Evidence from high-resolution lacustrine archives and paleosols in south Bohemia (Czech Republic)

Sediments from three paleolakes and two paleosol horizons in south Bohemia, Czech Republic, provide evidence of climate change and landscape evolution in central-eastern Europe on millennial to centennial timescales over the Late Glacial (~16–11.5ky). Based on a combination of geochemical, sedimentological and geophysical proxy indicators, along with the pollen record and soil micromorphology, we propose a relationship between vegetation cover, soil development, and erosional processes. Four major and two minor environmental stages, identified in all investigated paleo-lakes, were broadly correlated with the Late Glacial climatostratigraphy. Short-term (decadal to centennial) climatic deteriorations between the Bølling and Allerød, and within the Allerød, have been correlated with the Older Dryas and the Intra-Allerød Cold Period (IACP) respectively. B horizons of two (gleyic) podzols discovered under aeolian sand dunes in the lake catchments were dated to the Allerød interstadial and were parallelized with Usselo soils – pedostratigraphical marker horizons of west- and northern-central Europe. The upper parts of these soils have signs of colluvial processes. According to the radiocarbon dating, the erosion occurred at 13,155±150cal. yr BP and can be associated with the IACP event, which is marked by a significant input of allogenic material into the lake basins. We attribute the significant increase in the iron and consequent phosphorus content in the lake sediments during the Allerød to the podzolization that occurred with the humid interstadial conditions.

Modern pollen vegetation relationships in a dry deciduous monsoon forest: A case study from Lonar Crater Lake, central India

As part of ongoing research on Holocene lacustrine sediments of Lonar Crater Lake (central India), pollen assemblages in lake surface sediment and soil samples were studied to unravel pollen–vegetation relationships, including pollen transport processes in tropical dry deciduous forest vegetation. Furthermore, palynological results were compared with geochemical proxies and spatial features of the lake sediments and the vegetation. The obtained data reveal strong differences in pollen assemblages and pollen concentrations between and within the studied trapping media. Local arboreal vegetation is adequately represented in the soil samples, but is less represented in the lake surface sediment samples. The composition of the lacustrine pollen assemblages is mainly influenced by patterns of transport through surface and channel runoff. Besides the relevance of our new data for reliable interpretation of fossil pollen spectra extracted from Lonar sediment cores, the results of this study are of general importance for the understanding of Quaternary pollen assemblages from tropical lacustrine archives, as well as for the implementation and selection of suitable approaches for quantitative pollen based environmental reconstructions in south Asia and beyond.

Synchronizing Holocene lacustrine and marine sediment records using paleomagnetic secular variation

High sediment accumulation rates in lacustrine and shallow-marine archives around Iceland offer the potential to compare high-resolution paleoclimatic reconstructions from terrestrial and marine archives; however, direct comparisons are hampered by difficulties in stratigraphic correlation and in deriving accurate age models for lacustrine archives. Icelandic paleomagnetic secular variation (PSV) has the potential to synchronize these records. Here we compare Holocene PSV from a well-dated marine core on the North Iceland shelf with PSV from two lacustrine archives with comparable sediment-accumulation rates, HVT03–1A, a glacier-dominated lake, and HAK03–1B, in a nonglacial catchment. Geochemically characterized tephra layers combined with unique high-amplitude structures in the PSV records provide secure tie points every ∼200 yr. Once the records are synchronized, the chronology from the marine core can be reliably transferred to the two lacustrine records. The resultant lacustrine age models reveal large changes in sediment accumulation rate at submillennial scales that escape detection in conventional age models with independent dates every ∼1 k.y. Sediment accumulation rate changes occur at similar times in both lakes, despite very different catchment properties. Low and regular accumulation rates during the Holocene thermal maximum suggest regionally stable, vegetated catchments, followed by a stepped landscape destabilization during the transition into neoglaciation, culminating with maximum sedimentation rates during the Little Ice Age. PSV allows synchronization between multiple records from nearby marine and lacustrine archives, providing improved age models and a means of assessing leads and lags between marine and terrestrial environments.

The potential of combining of lacustrine, palaeopedological and other palaeo-environmental archives – general idea and examples from the Late Pleistocene in the Mediterranean

The potential of combining of lacustrine, palaeopedological and other palaeo-environmental archives – general idea and examples from the Late Pleistocene in the Mediterranean

Tracking glacial and high altitude Holocene alpine environments fluctuations from clastic and organic markers in proglacial lacustrine archives (Lake Blanc Huez, Grandes Rousses Massif, France)

Tracking glacial and high altitude Holocene alpine environments fluctuations from clastic and organic markers in proglacial lacustrine archives (Lake Blanc Huez, Grandes Rousses Massif, France)

Response of the Truckee River to lowering base level at Pyramid Lake, Nevada, based on historical air photos and LiDAR data

The Truckee River in western Nevada has severely incised in response to a net 20 m of lake-level lowering of Pyramid Lake over the past 120 yr, leaving a suite of cut terraces that extend ~15 km upstream from the lake where incision was arrested by bedrock in the channel. Channel planform changes and terrace development were mapped over a 70 yr period using rectified aerial imagery and light detection and ranging (LiDAR) data in ArcGIS. Discrete point elevations were extracted from the LiDAR data for channel remnants on each of the different-aged terraces and combined with channel distance measurements derived from the appropriate aerial imagery to derive true channel gradients for each of the photo years. These same point elevation measurements were also resolved to a common valley distance (CVD), as is often done when studying prehistorical terrace sequences. Comparison of the true channel distance (TCD) profiles to the CVD profiles demonstrates that the TCD profiles are longer and less steep than the CVD profiles. These differences exist because resolving terrace elevations to a CVD does not account for decreasing sinuosities and straighter channel planforms through time. As base level fell to its historical low elevation, the channel became steeper, straighter, and smoother, which increased the rate of sediment transport and delivery to Pyramid Lake. Over the past 120 yr, ~60,000,000 m 3 of sediment have been removed from the bed and banks of the lower river and redeposited in the lake, temporarily increasing the sedimentation rate. Larger trenches through deltaic and lacustrine deposits occupied by rivers and streams flowing into Pyramid Lake and other closed basins may reflect similar rapid responses to lowering base levels at times in the past. Therefore, lowering lake levels at Pyramid Lake and elsewhere during relatively dry times may be at least partly responsible for transient increases in sedimentation rates in lacustrine archives.