Characterising the heterogeneous nature of tufa mounds by integrating petrographic, petrophysical, acoustic and electromagnetic measurements

Abstract Determination of the physical properties of subsurface geological bodies is essential for georesource management and geotechnical applications. In the absence of direct measurements, this usually passes via geophysical methods such as seismic and ground‐penetrating radar. These require conversion to physical properties, and measurements at different scales to test for consistency. This approach is non‐trivial in geobodies with heterogeneous patterns of properties. Tufa mounds—in‐situ terrestrial carbonate buildups precipitating from geothermal waters—are characterised by high contrasts in facies and petrophysical properties from microscale to macroscale, and are therefore ideally suited to test the ability of non‐invasive geophysical methods to estimate such contrasts, and to develop petrophysical models based on geophysical properties. Here, a laboratory‐based study of a Pleistocene tufa mound in Spain is presented that combines (1) petrography, (2) digital 2D pore network analysis, (3) gas porosity and permeability measurements, (4) acoustic velocity measurements and (5) electromagnetic wave velocity and porosity determination from ground‐penetrating radar, to develop empirical petrophysical models. These results show the consistency of petrophysical properties determined with different methods across various observational scales. Electromagnetically derived porosity positively correlates with gas porosity. Petrophysical properties depend on measurable rock fabric parameters and the degree of cementation, which provide predictive tools for subsurface geobodies. Strongly cemented peloidal‐thrombolitic fabrics with intergranular and intercrystalline pores, and a dominance of small complex pores best transmit acoustic waves. Weak cementation and a significant fraction of large simple pores (framework, vegetation moulds) increase porosity and permeability of shrubby fabrics, while causing lower acoustic velocity. This study demonstrates that ground‐penetrating radar models can be used in combination with direct measurements of physical subsurface properties to capture highly contrasting physical properties associated with different sedimentary facies that would not be achievable with other methods, thus improving the understanding of formational processes

Reconstructing Paleoflood Occurrence and Magnitude from Lake Sediments

Lake sediments are a valuable archive to document past flood occurrence and magnitude, and their evolution over centuries to millennia. This information has the potential to greatly improve current flood design and risk assessment approaches, which are hampered by the shortness and scarcity of gauge records. For this reason, paleoflood hydrology from lake sediments received fast-growing attention over the last decade. This allowed an extensive development of experience and methodologies and, thereby, the reconstruction of paleoflood series with increasingly higher accuracy. In this review, we provide up-to-date knowledge on flood sedimentary processes and systems, as well as on state-of-the-art methods for reconstructing and interpreting paleoflood records. We also discuss possible perspectives in the field of paleoflood hydrology from lake sediments by highlighting the remaining challenges. This review intends to guide the research interest in documenting past floods from lake sediments. In particular, we offer here guidance supported by the literature in how: to choose the most appropriate lake in a given region, to find the best suited sedimentary environments to take the cores, to identify flood deposits in the sedimentary sequence, to distinguish them from other instantaneous deposits, and finally, to rigorously interpret the flood chronicle thus produced.publishedVersio

Regional precipitation trends since 1500 CE reconstructed from calcite sublayers of a varved Mediterranean lake record (Central Pyrenees)

The Mediterranean region is expected to be highly impacted by global warming, although the uncertainty of future scenarios, particularly about precipitation patterns remains quite large. To better predict shifts in its current climate system and to test models, more regional climate records are needed spanning longer than the instrumental period. Here we provide a high-resolution reconstruction of autumn precipitation for the Central Pyrenees since 1500 CE based on annual calcite sublayer widths from Montcortès Lake (Central southern Pyrenees) varved sediments. The 500-yr calcite data series were detrended and calibrated with instrumental climate records by applying correlations and cross-correlations to regional precipitation anomalies. The highest relationships were obtained between a composite calcite series and autumn precipitation anomalies for the complete calibration period (1900-2002) and for the two halves of the full period. Applied statistical tests were significant, evidencing that the climatic signal could be reconstructed. The reconstructed precipitation anomalies show interdecadal shifts, and rainfall decrease within the coldest period of the LIA and during the second half of the 20th century, probably associated to current Global Warming. Neither increasing nor decreasing linear trends or periods of extreme precipitation events were identified. Our results are coherent with other palaeohydrological reconstructions for the northern Iberian Peninsula. Correlations between the predicted autumn precipitation and the main teleconnections -NAO, ENSO, and WEMO- were weak, although a potential relationship with the Atlantic Multidecadal Oscillation (AMO) pattern is suggested. The obtained reconstruction provides the first estimations of regional autumn precipitation shifts in the Central Pyrenees and is one of the few reconstructions that cover annual-to-century scale climate variability of precipitation in the Mediterranean region from the end of the Litte Ice Age (LIA) to the current period of Global Warming

Grazing activities in the southern central Pyrenees during the last millenium as deduced from the non-pollen palynomorphs (NPP) record of lake Montcortès

Human activities during the last millennium have shaped most of the present-day landscapes. During this time, in the southern central Pyrenees several climate periods and phases of variable human disturbance have driven varied landscape responses. In previous studies of the sediment deposits in Lake Montcortès (southern central Pyrenees) several climatic shifts (including the Medieval Climate Anomaly and the Little Ice Age), as well as forest clearance by fire, agriculture and cattle raising as the main human impacts were recorded since Medieval times. In this work we use non-pollen palynomorphs (NPP) on the same sequence to reconstruct the different human activities, with a special focus on grazing, at an average resolution of around 30 years per sample. Independent NPP proxies for fire and forest clearance were found, supporting former studies. Moreover, the NPP record shows four periods of high abundance of coprophilous fungi: 1) 830-865 CE; 2) 1120-1290 CE; 3) 1530-1795 CE; and 4) 1865-1880 CE. These four periods correspond to phases of increased livestock farming, as reported in historical documents. Comparison of pollen, historical documents, and NPP records show that the impact on landscape dynamics during the last millennium have been mostly related to variable human population density controlled by historical, political and cultural changes in the Pyrenean mountains. Moreover, the use and comparison of several independent proxies have highlighted the strength of the indicator value obtained

High-resolution (sub-decadal) pollen analysis of varved sediments from lake Montcortès (South-central pre-Pyrenees): a fine-tuned record of landscape dynamics and human impact during the last 500 years.

A high-resolution (average 6 years/sampling interval) palaeoenvironmental reconstruction using pollen, charcoal and non-pollen palynomorphs was carried out on annually laminated sediments of Lake Montcortès (southern Pyrenean flank). The results were combined with historical data to better understand landscape evolution and human interaction during the last 500 years. Our results show that human activities (cropping, livestock breeding and hemp cultivation and retting) have been the most important factors responsible for vegetation changes with highest intensity between 1530 and 1900 CE. By means of a sub-decadal study we have been able to evaluate short-lasting events at local and regional scales related to climate (heavy rainfall events and, high-land forest fluctuations) or to historical and well-dated and documented socio-economic events (i.e., crop promotions (hemp) or land abandonment-population emigration). The temporal extent (400 years) and continuity of Cannabis pollen peak have been confirmed, and new evidence of water quality changes, likely as a consequence of hemp retting practices between the mid-17th to late 19th century, are provided. This is the first high-resolution palaeoenvironmental study carried out in a varved lake on the Iberian Peninsula so far. With these data we hope to contribute to filling the gap in high-resolution palaeoenvironmental data

Finely laminated facies within the Montcortés lake sedimentary sequence (Lleida) during the last 6.000 years

The different sedimentological, geochemical and geophysical analysis performed in the Montcortés lake sedimentary record (Pre-Pyrenees, Lleida) helps to interpret the sedimentary evolution of this karstic lake during the last 6.000 years. The deposition of lacustrine varves is continuous during, at least, the last 3.500 Cal. yr BP. This fine lamination is punctuated by massive clastic facies corresponding to turbidite events. A total of 9 litostratigraphic units were recognized corresponding to three different depositional environments that alternate throughout the record; i) a shallow, meromictic lake with very high bioproductivity (unit VI: 6.000- 3.500 Cal. yr BP), ii) a deep, meromictic lake with high bioproductivity (units V, III and I; 3.500-1.250, 500-180 Cal. yr BP and last decades) and iii) deep, meromictic lake with higher clastic inputs (units IV and II; 1.250-500 and 180 Cal. yr BP- last decades). Several slumps deposits have been recognized within the sequence (units A, B and C

Pain intensity and sensory perception of Tender Points in female patients with fibromyalgia: A pilot study

Fibromyalgia syndrome (FMS) is a condition that courses with chronic pain, fatigue, sleep disturbance, impaired quality of life and daily function. Due to the lack of blood, imaging or histological confirmatory tests, the diagnosis of FMS is based on the presence of widespread pain and presence of tender points (TPs). Our aim was to assess the pain pressure thresholds (PPTs) and subjective pain perception (SPP) of all 18 TPs while applying a normalized pressure in female patients with fibromyalgia. An exploratory descriptive pilot study was conducted in 30 female patients with FMS. Sociodemographic data (e.g., age, height, weight, and body mass index), clinical characteristics (e.g., years with diagnosis and severity of FMS), PPTs (assessed with an algometer), and SPP (assessed with a visual analogue scale) of all 18 TPs were collected. A comparative analysis side-to-side (same TP, left and right sides) and between TPs was conducted. No side-to-side differences were found (p < 0.05). Significant differences between all 18 TPs were found for PPTs (p < 0.0001), and SPP (p < 0.005) scores were found. The most mechanosensitive points were located in the second costochondral junction, the occiput, the trochanteric prominence; the most painful while applying a normalized pressure considering the TP and side were those located in the gluteus, trochanteric prominence, and supraspinatus. The current study describes PPTs and SPP, as assessed with algometry and visual analogue scale, respectively, of all 18 TPs in female patients with FMS. TPs exhibited significant PPTs and SPP differences between TP locations with no side-to-side differences

Holocene atmospheric iodine evolution over the North Atlantic

Atmospheric iodine chemistry has a large influence on the oxidizing capacity and associated radiative impacts in the troposphere. However, information on the evolution of past atmospheric iodine levels is restricted to the industrial period while its long-term natural variability remains unknown. The current levels of iodine in the atmosphere are controlled by anthropogenic ozone deposition to the ocean surface. Here, using high-resolution geochemical measurements from coastal eastern Greenland ReCAP (REnland ice CAP project) ice core, we report the first record of atmospheric iodine variability in the North Atlantic during the Holocene (i.e., the last 11 700 years). Surprisingly, our results reveal that the highest iodine concentrations in the record were found during the Holocene Thermal Maximum (HTM; ∼ 11 500-5500 years before-present). These high iodine levels could be driven by marine primary productivity resulting in an Early Holocene "biological iodine explosion". The high and stable iodine levels during this past warm period are a useful observational constraint on projections of future changes in Arctic atmospheric composition and climate resulting from global warming

Was there a common hydrological pattern in the Iberian Peninsula region during the Medieval Climate Anomaly?

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Was there a common hydrological pattern in the Iberian Peninsula region during the medieval Climate anomaly?

Climate variability reconstructions for the last millennium from several Iberian lake and marine records shed light on the spatial and temporal hydroclimate and associated climate mechanisms during the Medieval Climate Anomaly