A multi-dating approach to age-modelling long continental records: The 135 ka El Cañizar de Villarquemado sequence (NE Spain)

Under embargo until: 2021-06-23We present a multidisciplinary dating approach - including radiocarbon, Uranium/Thorium series (U/Th), paleomagnetism, single-grain optically stimulated luminescence (OSL), polymineral fine-grain infrared stimulated luminescence (IRSL) and tephrochronology - used for the development of an age model for the Cañizar de Villarquemado sequence (VIL) for the last ca. 135 ka. We describe the protocols used for each technique and discuss the positive and negative results, as well as their implications for interpreting the VIL sequence and for dating similar terrestrial records. In spite of the negative results of some techniques, particularly due to the absence of adequate sample material or insufficient analytical precision, the multi-technique strategy employed here is essential to maximize the chances of obtaining robust age models in terrestrial sequences. The final Bayesian age model for VIL sequence includes 16 AMS 14C ages, 9 single-grain quartz OSL ages and 5 previously published polymineral fine-grain IRSL ages, and the accuracy and resolution of the model are improved by incorporating information related to changes in accumulation rate, as revealed by detailed sedimentological analyses. The main paleohydrological and vegetation changes in the sequence are coherent with global Marine Isotope Stage (MIS) 6 to 1 transitions since the penultimate Termination, although some regional idiosyncrasies are evident, such as higher moisture variability than expected, an abrupt inception of the last glacial cycle and a resilient response of vegetation in Mediterranean continental Iberia in both Terminations.acceptedVersio

Volcanism and climate change as drivers in Holocene depositional dynamic of Laguna del Maule (Andes of central Chile – 36° S)

Late Quaternary volcanic basins are active landscapes from which detailed archives of past climate and seismic and volcanic activity can be obtained. A multidisciplinary study performed on a transect of sediment cores was used to reconstruct the depositional evolution of the high-elevation Laguna del Maule (LdM) (36∘ S, 2180 m a.s.l., Chilean Andes). The recovered 5 m composite sediment sequence includes two thick turbidite units (LT1 and LT2) and numerous tephra layers (23 ash and 6 lapilli). We produced an age model based on nine new 14C AMS dates, existing 210Pb and 137Cs data, and the Quizapú ash horizon (1932 CE). According to this age model, the relatively drier Early Holocene was followed by a phase of increased productivity during the mid-Holocene and higher lake levels after 4.0 ka cal BP. Major hydroclimate transitions occurred at ca. 11, 8.0, 4.0 and 0.5 ka cal BP. Decreased summer insolation and winter precipitation due to a southward shift in the southern westerly winds and a strengthened Pacific Subtropical High could explain Early Holocene lower lake levels. Increased biological productivity during the mid-Holocene (∼8.0 to 6.0 ka cal BP) is coeval with a warm–dry phase described for much of southern South America. Periods of higher lake productivity are synchronous to a higher frequency of volcanic events. During the Late Holocene, the tephra layers show compositional changes suggesting a transition from silica-rich to silica-poor magmas at around 4.0 ka cal BP. This transition was synchronous with increased variability of sedimentary facies and geochemical proxies, indicating higher lake levels and increased moisture at LdM after 4.0 ka cal BP, most likely caused by the inception of current El Niño–Southern Oscillation and Pacific Decadal Oscillation (ENSO–PDO) dynamics in central Chile.Postprin

Biogeochemical sedimentology of the Pleistocene-Holocene transition of the TaguaTagua 3 record in central Chile (~34ºS)

Oral presentada en el XI Congreso Geológico de España, Ávila (España), 2-6 de julio de 2024Este estudio examina los cambios biogeoquímicos en el sitio geoarqueológico Tagua-Tagua durante la transición Pleistoceno-Holoceno en el centro de Chile (~34°S), mediante un análisis detallado de la secuencia TT19-3A a lo largo de los últimos 20 mil años. Se realizaron análisis de tamaño de grano, microfósiles, análisis isotópicos en carbonatos, y se estudiaron biomarcadores lipídicos como n-alcanos, n-alcanoles, ácidos grasos y esteroles para investigar los procesos sedimentarios y cambios ambientales pasados. Los resultados indican cambios significativos en el transporte y deposición de sedimentos, así como en la vegetación y temperatura hacia la transición Pleistoceno-Holoceno. Se produjeron cambios importantes en ~20.5-18, ~15-12.8, ~12,5-12, ~11,5-11 y ~10,5-10 ka cal BP caracterizados por cambios a condiciones más húmedas y temperatura. Detectamos un pulso humedo entre ~12,8 y 12,5 ka cal BP. El registro ATTL sugieren cambios importantes en la intensidad del Anticiclón del Pacífico Sur, sincronizados con cambios atmosféricos a gran escala durante la Terminación 1 y el inicio del Holoceno.[EN] This study examines the biogeochemical changes at the Tagua-Tagua geoarchaeological site during the Pleistocene-Holocene transition in central Chile (~34°S), through a detailed analysis of the TT19-3A sequence over the last 20,000 years. Analyses of grain size, microfossils, isotopic analyses on carbonates, and lipid biomarkers such as n-alkanes, n-alkanols, fatty acids, and sterols were conducted to investigate sedimentary processes and past environmental changes. The results indicate significant changes in sediment transport and deposition, as well as in vegetation and temperature towards the Pleistocene- Holocene transition. Major changes occurred at ~20.5-18, ~15-12.8, ~12.5-12, ~11.5-11, and ~10.5-10 ka cal BP, characterized by shifts to wetter conditions and temperature. We detected a wet pulse between ~12.8 and 12.5 ka cal BP. The ATTL record suggests significant changes in the intensity of the South Pacific Anticyclone, synchronized with large-scale atmospheric changes during Termination 1 and the beginning of the Holocene

Hydroclimate variations over the last 17,000 years as estimated by leaf waxes in rodent middens from the south-central Atacama Desert, Chile

Leaf cuticular waxes are one of the most important environment-plant interaction structural systems that enable desert plants to withstand extreme climatic conditions. We present a long chain n-alkyl lipids study in fresh plant leaves and rodent palaeomiddens collected along an elevational gradient in the south-central Atacama Desert of Chile, covering six different vegetation belts: Steppe (4500-4000 m asl), Puna (4000-3300 m asl), pre-Puna (3300-2400 m asl), Absolute Desert (2400-1000 m asl) and Coastal Desert (1000-0 m asl). The 28 rodent palaeomiddens analyzed from Quebrada Incahuasi (25.6 °S, 3600 m asl) span the last 17,000 years. Modern-day distribution of long-chain n-alkanes and n-alkanoic acids varies among the dominant plant associations of the Atacama Desert. These plants show a species-specific chemotaxonomy linked to the climatic conditions. Furthermore, differences in average chain length (ACL) and carbon preference index (CPI) suggest that these plant communities are highly adapted to extreme environmental conditions. The sum of leaf wax n-alkanes was highest under wet conditions, while n-alkanoic acids (between n-C and n-C) increased with hyperaridity. Similarly, analysis of n-alkane time series from palaeomiddens showed that the greatest changes in leaf wax n-alkane distributions (ACL and CPI) corresponded to the greatest increases in moisture during the Central Andean Pluvial Event (CAPE; between 18 and 9 ka cal BP) and the Late Holocene. The shift in the palaeomidden n-alkane distributions is corroborated by the relative abundance of rainfall-dependent extra-local taxa. This is the first study to report leaf wax content obtained from ancient rodent middens, and shows promising results as a robust hydroclimate proxy for the Atacama Desert region.This research was supported by the ANID - FONDECYT (grants 1190398 , 1191568 , 11220930 , 3180368 ), Chile. Additional support was provided by the ANID – Millennium Science Initiative Program Nucleus AFOREST ( NCS2022_24 ) and the Millennium Science Initiative Nucleus UPWELL ( NCN19-153 ) and IEB (through ANID FB210006 ), Chile

Unprecedented recent regional increase in organic carbon and lithogenic fluxes in high altitude Pyrenean lakes

We have conducted a monitoring survey and paleolimnological study of a W-E transect of six high altitude lakes (1870-2630 m asl) in the western and central Pyrenees (Spain) to evaluate the regional response to current global change in high altitude Mediterranean mountains. The reconstructed Total Organic Carbon (TOC) and lithogenic (L) fluxes during the last 1200 years show the expected variability as lakes differ in altitude, geological and climate settings, limnological properties and human impact history. However, all show unique patterns after 1850 CE, particularly during the Great Acceleration (after 1950 CE). Recent L increase could be related to higher erodibility by rainfall and run-off during the longer snow-free season in the Pyrenees. In all sites, higher TOC and geochemical (lower δ 13 C, lower C/N) and biological (diatom assemblages) signatures since 1950 CE suggest an increase in algal productivity, likely favored by warmer temperatures and higher nutrient deposition. These recent, unprecedented L and TOC increases, in spite of their diverse history and limnological properties of the lakes, demonstrate the regional impact of the Great Acceleration not only in the ecological dynamics of alpine lakes but also in the hydrological cycle in high altitude mountain watersheds

sj-docx-2-hol-10.1177_09596836231225722 – Supplemental material for Population dynamics and cultural niche construction during the Late Holocene in a mediterranean ecosystem (central Chile, 32°S−36°S)

Supplemental material, sj-docx-2-hol-10.1177_09596836231225722 for Population dynamics and cultural niche construction during the Late Holocene in a mediterranean ecosystem (central Chile, 32°S−36°S) by Carolina Godoy-Aguirre, Matías Frugone-Álvarez, Eugenia M. Gayo, Roberto Campbell, Mauricio Lima, Antonio Maldonado and Claudio Latorre in The Holocene</p

sj-xlsx-1-hol-10.1177_09596836231225722 – Supplemental material for Population dynamics and cultural niche construction during the Late Holocene in a mediterranean ecosystem (central Chile, 32°S−36°S)

Supplemental material, sj-xlsx-1-hol-10.1177_09596836231225722 for Population dynamics and cultural niche construction during the Late Holocene in a mediterranean ecosystem (central Chile, 32°S−36°S) by Carolina Godoy-Aguirre, Matías Frugone-Álvarez, Eugenia M. Gayo, Roberto Campbell, Mauricio Lima, Antonio Maldonado and Claudio Latorre in The Holocene</p

A combined approach to establishing the timing and magnitude of anthropogenic nutrient alteration in a mediterranean coastal lake- watershed system

Human activities have profoundly altered the global nutrient cycle through Land Use and Cover Changes (LUCCs) since the industrial revolution and especially during the Great Acceleration (1950 CE). Yet, the impact of such activities on terrestrial and aquatic ecosystems above their ecological baselines are not well known, especially when considering the response of these systems to the intensity of LUCCs on nutrient cycles. Here, we used a multiproxy approach (sedimentological, geochemical and isotopic analyses, historical records, climate data, and satellite images) to evaluate the role that LUCCs have on Nitrogen (N) cycling in a coastal mediterranean watershed system of central Chile over the last two centuries. Despite long-term anthropogenic use (agriculture, cattle grazing) in the Matanzas watershed– lake system, these LUCC appear to have had little impact on nutrient and organic matter transfer since the Spanish Colonial period. In contrast, the largest changes in N dynamics occurred in the mid-1970s, driven by the replacement of native forests and grasslands by government-subsidized tree plantations of introduced Monterey pine (Pinus radiata) and eucalyptus (Eucalyptus globulus). These LUCC had major impacts on the transfer of organic matter (which increased by 9.4%) and nutrients (as revealed by an increase in total N) to Laguna Matanzas. Our study shows that the presence of anthropogenic land use/cover changes do not necessarily alter nutrient supply and N availability per se but rather it is the magnitude and intensity of such changes that produce major impact on these processes in these mediterranean watersheds.Postprin

Unprecedented recent regional increase in organic carbon and lithogenic fluxes in high altitude Pyrenean lakes

Abstract We have conducted a monitoring survey and paleolimnological study of a W-E transect of six high altitude lakes (1870–2630 m asl) in the western and central Pyrenees (Spain) to evaluate the regional response to current global change in high altitude Mediterranean mountains. The reconstructed Total Organic Carbon (TOCflux) and lithogenic (Lflux) fluxes during the last 1200 years show the expected variability as lakes differ in altitude, geological and climate settings, limnological properties and human impact history. However, all show unique patterns after 1850 CE, particularly during the Great Acceleration (after 1950 CE). Recent Lflux increase could be related to higher erodibility by rainfall and run-off during the longer snow-free season in the Pyrenees. In all sites, higher TOCflux and geochemical (lower δ13COM, lower C/N) and biological (diatom assemblages) signatures since 1950 CE suggest an increase in algal productivity, likely favored by warmer temperatures and higher nutrient deposition. These recent, unprecedented Lflux and TOCflux increases, in spite of their diverse history and limnological properties of the lakes, demonstrate the regional impact of the Great Acceleration not only in the ecological dynamics of alpine lakes but also in the hydrological cycle in high altitude mountain watersheds

A multi-dating approach to age-modelling long continental records: The 135 ka El Cañizar de Villarquemado sequence (NE Spain)

We present a multidisciplinary dating approach - including radiocarbon, Uranium/Thorium series (U/Th), paleomagnetism, single-grain optically stimulated luminescence (OSL), polymineral fine-grain infrared stimulated luminescence (IRSL) and tephrochronology - used for the development of an age model for the Cañizar de Villarquemado sequence (VIL) for the last ca. 135 ka. We describe the protocols used for each technique and discuss the positive and negative results, as well as their implications for interpreting the VIL sequence and for dating similar terrestrial records. In spite of the negative results of some techniques, particularly due to the absence of adequate sample material or insufficient analytical precision, the multi-technique strategy employed here is essential to maximize the chances of obtaining robust age models in terrestrial sequences. The final Bayesian age model for VIL sequence includes 16 AMS 14C ages, 9 single-grain quartz OSL ages and 5 previously published polymineral fine-grain IRSL ages, and the accuracy and resolution of the model are improved by incorporating information related to changes in accumulation rate, as revealed by detailed sedimentological analyses. The main paleohydrological and vegetation changes in the sequence are coherent with global Marine Isotope Stage (MIS) 6 to 1 transitions since the penultimate Termination, although some regional idiosyncrasies are evident, such as higher moisture variability than expected, an abrupt inception of the last glacial cycle and a resilient response of vegetation in Mediterranean continental Iberia in both Terminations