Madrid Basin Research Articles

Description of newly discovered cranial remains of Decennatherium rex juveniles from Batallones-10 (Late Miocene, Iberian Peninsula)

ABSTRACT The identification of additional Late Miocene (MN10, Late Vallesian) Decennatherium rex cranial remains at Batallones-10 (Torrejón de Velasco, Madrid Basin, Spain) provides valuable insights into the ontogenetic variability of this extinct giraffe. Most recovered specimens are adults, making the discovery of calves significant. The 2022 excavation yielded two juvenile hemimandibles, a maxilla, and a juvenile ossicone, likely from different individuals. The dental material represents one of the youngest specimens in the Batallones complex, with an estimated age of 4 months to 4.5 years, based on molar eruption stages seen in modern giraffes. The ossicone, resembling that of an adult male in shape but much smaller, mirrors the growth patterns in extant giraffes, where juvenile ossicones share adult proportions but are smaller. This ossicone was detached from the skull, typical for juveniles, as ossicones do not fuse with the cranial roof until later. This discovery broadens our understanding of giraffe ontogeny and includes the first giraffe calf ossicone found in the Iberian fossil record.

Underground Gas Storage Monitoring Using Free and Open Source InSAR Data: A Case Study from Yela (Spain)

Gas consumption is subject to large seasonal fluctuations between the summer season (period with lower request) and the winter season (time with increased consumer demand). Underground gas storage applications (UGS) help to ensure a steady and reliable supply of natural gas, even during periods of peak demand, smoothing price fluctuations and providing a means of balancing the supply and demand of natural gas on a daily, weekly, or seasonal basis. However, UGS activities can induce vertical ground displacement, which is usually strictly associated with the injection and withdrawal of gas into/from the reservoir. It is necessary to carefully monitor and manage the potential impact of UGS activities on the subsurface and surface to ensure the stability and safety of the local environment. The Interferometric Synthetic Aperture Radar (InSAR) technique can provide a wide range of high-precision information on seasonal surface deformation associated with UGS activities useful for increasing the amount of information on ground deformation monitoring. This study introduces a unique and replicable approach to investigating freely available ground movement data for a fractured aquifer reservoir located in the Madrid Basin (Guadalajara, Spain), which is currently employed for seasonal underground gas storage applications. Notably, this study gives a comprehensive comparison of InSAR results of UGS activity in a deep aquifer, leveraging data that are entirely open-source and easily accessible. The Yela UGS project exploits a carbonate reservoir (dolomite) managed, since 2012, by Enagás, the Spanish main Transmission System Operator (TSO). InSAR data from 2015 to 2021 provided a full and coherent ground deformation pattern of the area. Based on this data, a fully integrated volumetric variation model was developed, elucidating the effects of gas storage activity. A significant correlation between the periodic injection/withdrawal rates of natural gas and InSAR ground deformation over time was identified.

Correlation of Boreholes through Well Logs: Application to the Western Sector of Madrid

This study correlates the results obtained from the resistivity and spontaneous potential well logs in six boreholes for water extraction, located in the multilayer siliciclastic basin in the Madrid region, in the center of the Iberian Peninsula. Given the small lateral continuity that the layers considered in isolation show in this type of multilayer aquifer, geophysical stretches, with their corresponding average lithological assignments, have been established to achieve this objective from the well logs. These stretches allow for mapping the internal lithology in the studied area, obtaining a correlation of greater geological scope than that provided by the correlation between layers. Subsequently, the possible correlation of the lithological stretches selected in each of the boreholes was analyzed, verifying their lateral continuity and establishing an NNW-SSE section in the study area. In this work, the transcendence of the correlation of wells up to great distances (about 8 km in total, and average distance of 1.5 km between wells) is focused on the fact that, if there is a presence of pollutant in certain aquifer stretches in a part of the studied area, overexploitation in the Madrid basin will cause the mobilization of this pollutant to the whole basin, with a possible impact on non-polluted areas.

Anterior ossicone variability in Decennatherium rex Ríos, et al. 2017 (Late Miocene, Iberian Peninsula)

ABSTRACTThe recovery of a new partial cranium of Decennatherium rex Ríos et al. 2017 bearing two anterior and two posterior ossicones from the Late Miocene deposits of the site Batallones-10 (MN-10, Cerro de los Batallones, Madrid Basin) sheds light on the complex variability of the cranial appendages of these extinct giraffids. The special features of the anterior ossicones of BAT10’18-C6-40, each formed by two bosses and separated by a septum increase the range of morphological variability found in the anterior ossicones of giraffids. Posterior ossicone variability has already been described in several sivatherine taxa as Sivatherium maurusium (Harris, 1974) but anterior ossicone variability has never been discussed for four-ossicone taxa. This new specimen accounts for the third morphotype found in D. rex anterior ossicones. BAT10’18-C6-40 is identified as an adult D. rex male on the basis of the development of the posterior ossicones. These are large and already show the first large bump which in this taxon is always located on the middle of the dorsal surface at a similar height on the right and left ossicones which agrees with Solounias (1988) who stated that these small irregular protuberances have a somewhat fixed position, suggesting a genetic basis. This new specimen represents a new example of cranial variability in D. rex, and makes it the extinct giraffid with the largest anterior ossicone variability found so far.

Sepiolite and Other Authigenic Mg-Clay Minerals Formation in Different Palustrine Environments (Madrid Basin, Spain)

Lithofacies belonging to mud-flat and palustrine deposits (lake margin) in the Miocene of the Madrid Basin (Spain) have been studied. Four lithofacies corresponding to mud flat (1 and 3) and palustrine (2 and 4) deposits have been differentiated. Units 1 and 3 consist mainly of mudstones and carbonates (calcretes and diolocretes). The clay fraction is dominated by trioctahedral smectite (up to 79%) with illite and kaolinite as minor components. The d(060) spacing value shows reflections at 1.52 and 1.50 Å indicating also the presence of dioctahedral phyllosilicates. Unit 2 consists predominantly of lutites (claystones), locally with carbonate and chert nodules. The clay fraction is dominated by sepiolite (up to 96%) with variable contents of smectite and subordinate illite. The d(060) spacing value shows reflections at 1.51 and 1.52 Å indicating trioctahedral clay minerals. Unit 4 consists mostly of carbonates (limestones) with mudstone and lutite inserts. The clay fraction shows different contents of sepiolite, palygorskite and dioctahedral smectite. The analysis of a selection of trace elements (Cr, Co, Th, La, Sc) has allowed us to determine the characteristics of the source area as dioritic, somewhat different from those of the nearby materials from the Batallones sector. Sepiolite shows FWHM values ranging between 0.68 and 1.10 (2θ), indicating “low crystallinity sepiolite”. Differences in the conditions of formation of magnesian smectite and palygorskite have been observed in the mud-flat and palustrine deposits. The formation of sepiolite mainly by neoformation in palustrine deposits with different hydrochemistry is remarkable, leading to differences in fibre size and crystallinity of the fibrous clay mineral. Authigenic transformation processes from previous Al-rich phases would be responsible for the formation of saponite and palygorskite in mud flat and palustrine environments, with different pH conditions.

Seismites in Miocene gypsum microbialites: Multiproxy tools for paleoenvironmental reconstruction of saline lakes

This work provides the first evidence of seismites within Miocene gypsum microbialites deposited in inland lakes. Seismites are observed on good quality outcrops in two separated successions of the Madrid and Duero basins (central Spain) that are sited nearby strike-slip faults. The successions consist of sandy gypsum facies interbedded with gypsiferous mudstone and marlstone. The association of microbial induced sedimentary structures (MISS) with mineralogical biosignatures such as intrasediment-grown lenticular gypsum, dolomite with inner biomolds and other biological induced minerals, supports that gypsum beds represent microbialites. Gypsum microbialites are characterized by parallel-lamination, cross-bedding and laminated leveling structures. The rapid mineralization of the microbial mats and biostabilization processes may play a role in the preservation of the depositional structures in sulfates. In addition to MISS, several categories of large-scale soft-sediment deformation structures (SSDSs) reflecting ductile and brittle behavior repeat vertically through the successions. These are classified as load casts, pillows, dish structures, convolute bedding and lamination, plastic intrusions, fluid escape tubes, mud/sand volcanoes, Neptunian dikes and fractures. The deformation structures in crystalline sediments are interpreted to be caused by seismic shocks of magnitude over 5 related with syndepositional fault movements. Micromorphological analysis of gypsum beds reveals distinctive features such as cracked crystals, oriented crystals filling dikes and horizontal microstylolites that also indicate seismic shocks. Comparison between the two basins shows some differences in the type and vertical distribution of structures, and this suggests that earthquakes were less frequent and of higher magnitude in the Madrid Basin. The results confirm that microbial gypsum deposits have both high susceptibility to earthquakes and high potential to preserve a wide range of information of the sedimentary environment, including paleoecology, paleogeochemistry, paleohydrodynamics, and seismogenic behavior of microbial sediments and faults.

Advances in the hydraulic interpretation of water wells using flowmeter logs

Abstract. This paper reports on the methodology developed for a new hydraulic interpretation of flowmeter logs, allowing a better characterization of continental hydrological basins. In the course of a flowmeter log, different flow stretches are established, mostly corresponding to permeable layers (aquifers), among which there are other stretches mainly corresponding to less permeable layers (aquitards). In such hydrological basins of sufficient thickness, these flow stretches may not have the same hydraulic head. This fact brings about the need for a new hydraulic interpretation that provides the actual distribution of horizontal permeability throughout the aquifer at depth. The modified hydraulic interpretation developed in this study focuses on the differences of the effective pressure gradient (considered the difference between the hydraulic head in the well and the hydraulic head of each stretch) experienced by the different flow stretches along the well, due to the existence of different hydraulic heads. The methodology has been developed starting from a water well located in a multilayered aquifer within the so-called Madrid basin (the north-western part of the continental basin of the Tagus River), located in the centre of the Iberian Peninsula. In this well, a step-drawdown pumping test was conducted, in which the pumping rate versus drawdown and the specific capacity versus drawdown showed discrepancies with Darcian behaviour and an exponent of the Jacob equation of less than 1. Flowmeter logs were then recorded for different discharge rates and pump depths; the resulting water input from deeper permeable layers did not appear to show the expected relation with respect to drawdown. With the proposed methodology the results comply with the expected linearity and the cited discrepancies are solved.

Petrophysics and sediment variability in a mixed alluvial to lacustrine carbonate system (Miocene, Madrid Basin, Central Spain)

AbstractThis study evaluates variations in petrophysical properties within a mixed alluvial to lacustrine carbonate system (Miocene, Madrid Basin, Central Spain). The transition from alluvial environments to lake margins settings displays a shift from alluvial, siliciclastic red sandstones and mudstones to palustrine–lacustrine mudstones to packstones. Fluctuations in lake‐water level enabled land plants to occupy the lake margins during periods of low lake levels. The palustrine carbonates include features like pseudo‐microkarst, nodular and mottled limestones; the lacustrine deposits include enlarged root cavities, desiccation cracks and channel bodies. Scarce fresh water biota comprises charophytes, gastropods and ostracods. The sediments possess high natural, irregular varying, gamma‐ray values at the alluvial–lacustrine transition, and low, but constant values at full lacustrine sites. Acoustic properties agree with lithological variations within individual facies. Porosity is the most important parameter influencing P‐wave and S‐wave velocities. The scatter in the velocity–porosity relationship links to the porosity type; macro‐porosity or microporosity. The wide range of pore types and pore sizes results in a weak porosity to permeability relationship for the carbonate‐dominated rocks with low permeability for microporous and high permeability for macro‐porous carbonates. The sandstones (probably only inhibiting interparticle porosity), and to a lesser extent the sandy wackestones to packstones, show quite a strong relationship between porosity and permeability. Elastic properties of mixed alluvial–lacustrine deposits (this study) and marine deposits (literature data) overlap as variations in pore structures and porosity values are similar. Only 16% of the marine and lacustrine carbonate sediments display Equivalent Pore Aspect Ratio values above 0.2. In travertine deposits, 83% of the samples exceed Equivalent Pore Aspect Ratio values above 0.2, which highlights that travertine deposits are dominated by larger Equivalent Pore Aspect Ratios compared to lacustrine and marine carbonate deposits. Travertines display other rock frameworks with different pore types, pore distribution and amount of porosity.

Recurring taphonomic processes in the carnivoran‐dominated Late Miocene assemblages of Batallones‐3, Madrid Basin, Spain

Carnivoran-dominated fossil sites are scarce in the fossil record but provide precious information on the diversity and ecology of past carnivoran guilds. The Cerro de los Batallones sites host the oldest carnivoran-dominated assemblages, with the highest carnivoran abundances observed in the fossil record. Batallones-3 (Late Miocene, Madrid Basin, Spain) hosts three discrete, carnivoran-dominated fossiliferous levels deposited in a 15m-diameter, 4m-high pseudokarstic cavity with 1m-high talus cone located beneath the mouth of the cavity on the roof. Levels I, II and III are multitaxic multidominant assemblages, with the sabretooth cats Promegantereon ogygia and Machairodus aphanistus and the ursid Indarctos arctoides being the most abundant species. These carnivoran-dominated assemblages are autochthonous and show diagenetically fractured but well-preserved remains (complete, little to no weathering or abrasion). Root marks and manganese oxide precipitation are common and more abundant in Level III, due to modern pedogenic processes. There are also a few allochthonous, badly preserved (weathered and abraded) herbivore remains that were washed into the cavity. The taphonomic homogeneity of all three levels suggests recurring taphonomic and geologic processes throughout the accumulation of infill in the cave. The trap-like nature of the cave, unbroken and largely unweathered carnivoran bones suggest these predators intentionally jumped into the cave but were unable to escape.

Early evidence of continental aridity and open-habitat grasslands in Europe as revealed by the Middle Miocene microflora of the Madrid Basin

In this study we present a new, extensive palaeobotanical and palaeoclimatic record from 85 microfloral assemblages of Middle Miocene (late Langhian–early Serravallian) age recovered from ten localities in the Madrid Basin. A large, shallow, slightly saline lacustrine system developed in the study area, promoting the occurrence of salt-tolerant plant communities on the lake margin. The regional landscape of the basin was characterised by grass-dominated, savannah-like vegetation under a warm (MAT: 13.8–18.8 °C) and semi-arid (MPwet: 151–71 mm, MPdry: 45–4 mm) climatic regime with marked seasonality of temperature and precipitation. These data re-open the debate on the origin of grasslands linked to dry conditions in Europe. Overall increased cooling and aridity through the Miocene led to the onset of grass-dominated habitats at the expense of forests, a process that in eastern Europe has been shown to occur from the Late Miocene. Our results, together with previous palaeobotanical and fossil mammal data from southern and central Spain, strongly indicate that open habitats were already prevalent in the Iberian Peninsula in the Middle Miocene, suggesting an earlier establishment here than in eastern Europe, possibly following a temporal pattern like the Anatolian Peninsula. The taxonomic diversity yielded by the samples from the Madrid Basin contributes to the understanding of the floristic composition of these early open habitats which were dominated by Poaceae, Amaranthaceae and Asteraceae with scattered shrubby and arboreal plants adapted to dry conditions such as Ricinus, Ephedra, Olea, Quercus, Acacia and Pinus. The age of the studied samples, coincident with the Middle Miocene Climatic Transition, indicates that this climatic episode marked an important step towards the establishment of open vegetation.

Taphonomic analysis of Batallones-10, a Late Miocene drought-induced mammalian assemblage (Madrid basin, Spain) within the Cerro de los Batallones complex

The Late Miocene Batallones-10 site (Madrid Basin, Spain) contains several authochthonous multitaxic assemblages. A total of 15 large-mammal species are documented, including hipparionine horses (Hipparion sp.), giraffes (Decennatherium rex) and moschids. Three discrete fossiliferous levels have been identified with the aid of artificial intelligence systems. Although there are some statistical differences in the faunal composition of each level, paleontological, geologic and taphonomic data from all three Batallones-10 levels point to similar taphonomic histories. Mortality data, with abundant young individuals and the presence of pregnant females, indicates a catastrophic process of bone accumulation mainly driven by prolonged drought. Relatively high proportions of partially preserved or fully-articulated skeletons, and absence of carnivore feeding marks on bones, suggest that carcasses were undisturbed by predation. Rapid desiccation of soft tissues kept many of the joints intact, resulting in a high proportion of articulated remains. During drought episodes, large mammalian herbivores congregated around a shrinking water-hole, depleting the local vegetation, such that weakened individuals died of starvation and miring rather than dehydration. When rainfall resumed, the lack of vegetation and presence of low-permeability surficial sepiolite-rich marls, resulted in rapid run-off. This buried most of the unweathered, unabraded remains, whilst slightly orienting or completely removing others. After burial, faulting and slickensides produced diagenetic fractures, which favoured the precipitation of manganese oxides on bone surfaces and the diagenetic corrosion of remains, which is more pronounced in the uppermost Level III. This work, which focuses on the taphonomy of a herbivore-dominated site, improves our overall knowledge of the formation of the Cerro de los Batallones palaeontological complex.

Tectono-Sedimentary Evolution of the Madrid Basin (Spain) during the Late Miocene: Data from Paleokarst Profiles in Diagenetically-Complex Continental Carbonates

An intra-Vallesian (Upper Miocene) paleokarst developed at the top of the Intermediate Miocene Unit in the continental intracratonic Madrid Basin is recognized. This paleokarst is an early shallow, tabular-shaped karst that shows a marked control by the depositional facies pattern and lithologies. By integrating morphological, petrological, and geochemical data, three hydrogeological zones were established throughout the paleokarstic profiles: (i) a paleo-vadose zone, characterized by vertically elongated caves and vadose cementation; (ii) a 3–7 m thick paleo-epiphreatic zone (paleo-water table fringe), with development of stratiform breccia bodies, the superimposition of both vadose and phreatic features, and the lowest Fe and Mn contents in host-rock carbonates; and (iii) a paleo-phreatic zone characterized by an increase in δ13C values and the predominance of phreatic cementation. The paleogeographic reconstruction for the intra-Vallesian paleokarst using profiles revealed relative topographic highs to the north and topographic lows to the south, drawing the paleokarst landscape. Immediately overlaying the paleokarst surface are fluvio-lacustrine facies belonging to the Miocene Upper Unit (Late Vallesian to Late Turolian). Their lowermost deposits consist of fluvial terrigenous facies deposited by approximately N–S fluvial streams, and pass upward into fluvio-lacustrine fresh-water limestones. This paleokarstic surface represents a major change in the evolution of sedimentary patterns of basin, from endorheic to exorheic conditions, as the result of a change from compressive to extensional conditions in the tectonic regime.

Stream mouth deposits in the palaeontological site of Somosaguas, Middle Miocene, Madrid Basin

The Middle Miocene sediments exposed in Somosaguas contain an excellent record of mammal fossil remains preserved in debris and mudflow deposits. In the sedimentary sequence of Somosaguas three facies associations are distinguished, representing alluvial fan and shallow lake margin environments. Alluvial fans are composed of mud and debris flow deposits. The whole of the lacustrine deposits are interbedded between debris and mud flow deposits. The shallow lake deposits are devoid of fossil remains, and they consist of well-sorted micaceous sandstone bodies with water flow structures, interbedded with thin mudstone beds. These sandstone bodies are interpreted as stream mouth lobes. Three integrated stratigraphic sections show that the lacustrine bedset overlain an erosion surface, probably scoured by flood waters. Palaeocurrent measurements indicate that the sediment filling the shallow lake came from the west and the north

Pliocene endorheic-exhoreic drainage transition of the Cenozoic Madrid Basin (Central Spain)

Abstract Late Cenozoic landscape evolution in intracratonic basins represents an illustrative example of the interaction between surface processes, climate, lithologic and tectonics factors. Here, we model the transition from endorheic to exorheic conditions for the intracratonic Madrid Basin (Tagus Basin, Central Spain). During the Late Cenozoic, this basin appears to have been the result of a prolonged period of ~4.0 Ma of headward erosion by the Atlantic external drainage system, local erosion and climatic oscillations. Determining the timing of this transition is crucial to understanding the principal mechanisms of the transition course of the intracratonic basins in or associated with pop-up ridges. We present a detailed geomorphic map of the north of the Tertiary Madrid basin and new age determinations of well-preserved pediments, alluvial fans, alluvial plains and strath terraces. By combining cosmogenic ˡ0Be-26Al-21Ne with magnetostratigraphic data, the sediments associated with the last endorheic phase yield an age of ~6.4 Ma. The earliest exorheic alluvial levels of the Madrid Cenozoic basin, explained here as the first fluvial terraces, have been dated through cosmogenic nuclides depth profiles (ˡ0Be-26Al) at 2.42 Ma and 2.36 Ma respectively.

New data on the mammalian systematics and biostratigraphy of the middle Miocene from Húmera (Pozuelo de Alarcón, Madrid)

Thanks to the new micromammal fossil material obtained during the 2010 and 2011 field campaigns from the palaeontological site at Húmera (Madrid Basin, central Spain), we have been able to revise the taxonomic arrangement and increase the number of micromammal taxa recorded and described by Menéndez Gamella et al. (2010). During the last campaigns 182 identifiable remains were recovered, in various states of preservation, belonging to 10 different species of micromammals: Megacricetodon collongensisgersii, Democricetodon larteti, Armantomys tricristatus, Microdyromys aff. monspeliensis, Microdyromys koenigswaldi, Heteroxerus rubricati, Heteroxerus grivensis, Heteroxerus sp., Lagopsis sp. and Galerix sp. This fossil association is correlated with biozone E (MN5), and provides new information in relation to the end of the Middle Aragonian from the Madrid basin

Turtles from the middle Miocene (MN5) of Somosaguas (Pozuelo de Alarcón, Madrid, Spain)

The systematic study of the vertebrate taxa found in the Middle Aragonian fossil sites of Somosaguas (Madrid, Spain) has provided important information on one of the most diverse vertebrate assemblages recognized in the Middle Miocene of the Madrid Basin. Although the mammals are the most abundant and diverse taxa recognized in Somosaguas, other vertebrate groups are also represented there. Several elements assigned to turtles, hitherto unpublished, are recognized. Their analyses allow to identify them as belonging to two terrestrial taxa, both assigned to Testudinidae. One of them is attributed cf. Cheirogaster, taxon very common in the Spanish Aragonian sites, and specifically in the Madrid Basin. The other taxon is identified as cf. Paleotestudo, a genus not previously cited in this basin

Basal middle Miocene Listriodontinae (Suidae, Artiodactyla) from Madrid, Spain

Excavations in basal middle Miocene deposits in the Madrid Basin (Old Mahou Brewery, Los Nogales, La Hidroeléctrica, Guadarrama I, Barajas) have yielded interesting assemblages of fossils, among which the listriodont suid Listriodon retamaensis Pickford & Morales, 2003, is well represented. Much of the material is juvenile, and several of the permanent teeth are unworn, permitting detailed observations to be made of the fine structures of the crowns, which was not possible with the original hypodigm of the species from Retama due to the heavy wear on most of the teeth in that sample. Refinement of the definition of the species is thus possible. Los Nogales also yielded two teeth of the small tetraconodont suid Retroporcus complutensis

DigApp and TaphonomApp: Two new open-access palaeontological and archaeological mobile apps

Two new paleontological and archaeological Android applications, DigApp and TaphonomApp, are presented in this manuscript. DigApp is intended to aid data collection, storage and management in archaeological and palaeontological excavations. DigApp allows easily recording of common field information such as spatial data and fossil identification data. Online and offline versions of DigApp were developed to fit all needs, and they can be modified according to the excavation particularities. TaphonomApp was created in order to assist taphonomists while carrying out detailed taphonomical evaluations both in the field and in the laboratory, making data collection quicker, homogeneous and overall, more efficient. DigApp and TaphonomApp are free, open-access and flexible software, that can be easily modified by any user (without the need of expertise in computing or coding) as explained in this paper. An in-depth guide on how to modify the apps is provided within this paper. DigApp and TaphonomApp have been used during palaeontological excavations carried out at one of the Batallones Butte vertebrate sites (Batallones-10, Middle Miocene) in the Madrid basin (Spain).

Microwave assisted acid treatment of kerolitic clays from the Neogene Madrid Basin (Spain) and its use in CO2 capture processes

Abstract The effect of the microwave assisted acid treatment on five kerolite-Mg-stevensite samples from the Neogene Madrid Basin was studied. Samples with lower amount of kerolite are more prone to suffer chemical modifications thought the microwave assisted acid treatment than the kerolite-rich clay ones by the partial leaching of Mg2+-species located in the octahedral sheet. This fact supposes that two structures with similar chemical compositions (kerolite and stevensite) display a different response to the microwave assisted acid treatment. Thus, Mg-smectite with interlayer cations, such as stevensite, are more labile to the acid treatment than kerolite, which does not have interlayer cations in such a way that acid digestion of stevensite occurs simultaneously at the edges of particles and within the interlayer space, whereas in the case of kerolite, it occurs exclusively at the particle edges. The acid treatment implies an increase of the specific surface area in all cases, reaching a highest SBET value of 435 m2/g. In the case of samples with higher stevensite content, the increase in the SBET is mainly due to increases of the microporosity, whereas in the sample with higher kerolite content the increase in the SBET is mainly ascribed to increase of the external surface area of the particles. Then, these materials were evaluated in CO2 capture processes reaching a maximum value of 1.98 mmol/g at 65 °C and 760 mm Hg.

Origins and genesis of loess deposits in central Spain, as indicated by heavy mineral compositions and grain‐size variability

AbstractThe formation of loess deposits strongly depends on the availability of deflatable dust‐sized material. Identification of source areas and mechanisms of dust production is essential for an appropriate characterization of related palaeoenvironmental conditions. So far, little research has been done on loess deposits in the Mediterranean region and information about mechanisms of dust production is very rare. In this context, it is not clear from where the loess deposits from the upper Tagus Basin in central Spain originated. The main objective of this study was to find out whether these loess deposits were formed primarily by mountain processes and fluvial comminution, or whether they have their origin in the weathering of Tertiary marls in the centre of the Madrid Basin. A further concern was to link the determined source areas with loess formation mechanisms and concomitant environmental contexts. Following a comprehensive approach using heavy minerals and grain‐size data, together with information on stratigraphic features and geomorphic positions, different local loess sources could be identified. This study shows that during the last 35 kyr a major proportion of the Tagus loess deposits was deflated from river floodplains, while the mountain region of the Iberian Range was identified as a significant source of respective floodplain sediments. Based on heavy mineral compositions and dating results, it was found that during Heinrich Stadial 3, sediment supply from the Iberian Range strongly increased, suggesting an environmental shift from initially warmer towards colder temperatures in late Marine Isotope Stage 3. Furthermore, it was found that grain‐size patterns clearly indicate maximum wind strengths during Heinrich Stadial 3, followed by Heinrich Stadial 2 and Heinrich Stadial 1. These results demonstrate that the formation of dust‐sized particles in this part of the Mediterranean operated similar to many other places in temperate and continental regions, and that weathering processes linked to hot and dry environments were only of minor importance.