De Parangueo Research Articles

Geomicrobiology of the Rincon de Parangueo maar crater: Exploring the link between an evolving extreme environment and its potential metabolic diversity

Abstract Rincon de Parangueo (RP) is a Quaternary maar crater located in the Michoacan‐Guanajuato Volcanic Field in central Mexico. Like other volcanic craters in the region, the central part was occupied by an endorheic lacustrine system. As a consequence of extensive groundwater extraction, the perennial lake started a gradual desiccation process and now the remnant ponds host a highly saline–alkaline ecosystem. The stratigraphic record indicates an exceptional and long‐term sedimentation of carbonate microbialites. Previous studies based on the 16S rRNA gene have shown that microbial communities have a widespread presence in the crater at the microbialites, the remaining saline ponds, superficial soils and below the surface. To understand the possible role of the microbial communities that generate these biogeological structures, novel analytical methods to resolve the amplicon datasets and their microbial metabolic potential were used. We describe in detail the relationship between the microbial communities, the evolution of physicochemical parameters, and carbonate morphology, in four micro‐environments. A 16S rRNA gene sequencing dataset from previous publications was re‐analysed using an ASV‐based bioinformatic pipeline to identify new insights into the microbial assemblage. Finally, a taxon‐based metabolic profile was used to predict the potential metabolic contribution of the prokaryotic community. Results indicated a refinement in terms of community composition using the ASV‐based bioinformatic methods. Functional profiling through 16S rRNA gene‐based analysis suggested metabolisms associated with carbonate precipitation, indicating a broad potential for microbially mediated carbonate precipitation (e.g., carbon fixation and photosynthesis). The possibility of biogenic methane gas production by methanogenic microorganisms was recognised, supporting the estimated flow of methane on the surface soils. The lacustrine evolution over the last years and the extreme physicochemical characteristics of RP have an impact on the microbial community structure. Prokaryotic community and metabolic potential results from RP coincide with the diversity and abundance of microbial communities and functional metabolisms reported from other microbialite‐forming lakes along the Trans Mexican Volcanic Belt. The identification of important possible phylotypes involved in carbonate precipitation might be an important factor in considering RP microbialites as active calcifying entities. These findings provide novel insights into the potential key role of metabolic pathways driving the process of carbonate precipitation inside RP and evidence of its importance as a microbial biodiversity hotspot in Mexico.

Planktonic microbial communities from microbialite-bearing lakes sampled along a salinity-alkalinity gradient.

Continental freshwater systems are particularly vulnerable to environmental variation. Climate change-induced desertification and the anthropogenic exploitation of hydric resources result in the progressive evaporation and salinization of inland water bodies in many areas of the globe. However, how this process impacts microbial communities and their activities in biogeochemical cycles is poorly known. Here, we take a space-for-time substitution approach and characterize the prokaryotic and eukaryotic microbial communities of two planktonic cell-size fractions (0.2-5μm and 5-30 μm) from lakes of diverse trophic levels sampled along a salinity-alkalinity gradient located in the Trans-Mexican Volcanic Belt (TMVB). We applied a 16S/18S rRNA gene metabarcoding strategy to determine the microbial community composition of 54 samples from 12 different lakes, from the low-salinity lake Zirahuén to the hypersaline residual ponds of Rincón de Parangueo. Except for systems at both extremes of the salinity gradient, most lakes along the evaporation trend bear actively forming microbialites, which harbor microbial communities clearly distinct from those of plankton. Several lakes were sampled in winter and late spring and the crater lakes Alchichica and Atexcac were sampled across the water column. Physicochemical parameters related to salinity-alkalinity were the most influential drivers of microbial community structure whereas trophic status, depth, or season were less important. Our results suggest that climate change and anthropogenic-induced hydric deficit could significantly affect microbial communities, potentially altering ecosystem functioning.

Mobile mud layer underneath the desiccated maar lake of Rincón de Parangueo and insights into its microbial fingerprints

We surveyed a subsurface layer of saturated mobile mud and its microbial fingerprints below the desiccated bottom of a maar lake at Rincón de Parangueo (RP), Mexico. A multi-scale approach was followed using geological fieldwork, coring of the sediments, ground penetrating radar survey, physico-chemical characterization including X-ray diffraction and scanning electron microscope, and high-throughput DNA sequencing methods. The mobile mud is an organic-rich silty clay, with high values of alkalinity, volumetric water content and conductivity. Mud mobility has been attributed to overpressure caused by disequilibrium compaction of sediments related to active subsidence and pore overpressure produced by an input of groundwater and gas content in the sediments and resulted in a diverse set of structures related to mud tectonics such as injection domes and fluid seeps through fractures. Extraction and sequencing of sedimentary environmental DNA in the mud layer were performed for Bacteria and Archaea. Despite the small number of samples obtained, the microbial fingerprint from the sedimentary environmental DNA at subsurface shares similarities with the microbial communities identified on the crater surface. Additionally, we identify the DNA of specific methanogenic microorganisms in the mud, such as Bathyarchaeia, Methanomassiliicoccales, and Methanobacteriales, and we speculate on their probable role in gas production and pore overpressure in the mud layer. The underground mud at Rincón de Parangueo represents a geologically dynamic environment with conditions that are favorable for the thriving of microbial communities.

Bioprospecting of haloalkaliphilic microorganisms isolated from a dried-out maar in the volcano “Hoya Rincón de Parangueo”

Halophiles can be found in hypersaline environments and they can synthesize products of industrial interest. Method: In this work, 37 bacterial strains were isolated from the sediment of a dried-out maar of the “Hoya Rincón de Parangueo” (Mexico) on different culture media with 20% NaCl and pH 9, while potential industrial extracellular enzymes were determined. Results: Eight genera Salsuginibacillus, Alkalibacillus, Bacillus, Staphylococcus, Oceanobacillus, Halomonas and Nesterenkonia besides 15 distinct species belonging to Actinobacteria, Firmicutes and Proteobacteria were identified. The L371, LTA7 and SU3 isolates produced proteases, M20, L5, L7, L8, Y1, Y2, M3, M9 and RA lipases, LTA4 and SU3 amylases, while LTA7, Y2, M5, M9 and RA caseinases with enzymatic activity at pH 9. Production of siderophore was found in 17 isolates. Discussion or Conclusion: It is reported for the first experimental evidence of siderophores production by N. alba, Alkalibacillus and Oceanobacillus at 6% NaCl (w/v). Isolates RE, RG1, RG2, RH1, RA and I11 showed 2.8% to 4.1% genetic distance with Nesterenkonia species and might represent new species.

Total CO2 output and carbon origin discharged from Rincón de Parangueo Maar (México)

A geochemical survey was carried out (May 2016) in the Rincón de Parangueo maar in Valle de Santiago, México. The challenge was to measure CO2 and CH4 fluxes discharged from soil and to investigate the chemical and isotopic compositions of interstitial soil gases and remaining vents at the bottom of maars system subjected to critical and high rate drawdown aquifer. Total CO2 flux calculated by sequential Gaussian simulation is 10.6 ton d−1 (±2.1 ton d−1) over the entire crater maar area. Two degassing groups were recognized: Group A (background degassing) with values lower than 10 g m−2 d−1 (40% of the total measurements) and Group B with values ranging between 10 and 347.1 g m−2 d−1 (60% of the total amount of measurements). CH4 flux ranges from 2.1 to 1577 g m−2 d−1. CH4/CO2 flux mean ratio is ~20.51 while CH4/CO2 concentration ratios are 78 and 119 for bubbling gases and 8.4 for interstitial gases. The δ13C-CH4 values are ~65 per mil vs V-PDB indicating a biogenic origin of methane in bubbling and interstitial gases. The δ13C-CO2 values, ranging from −10.6 to −27.6 and −1.9 per mil vs V-PDB for bubbling gases and the interstitial gases, respectively, suggest secondary CO2 consumption within the soil.

Floristic composition in deciduous tropical forest to west of Irapuato, Guanajuato

The flora of Irapuato has been poorly explored, because it is an area dedicated to agriculture and there are few strains of tropical deciduous forest and subtropical scrubland. The objectives of the study were to know the floristic composition in Cerro del Veinte, compare the richness of species with other locations that have the same type of vegetation and determine the conservation status of the species according to NOM-059 SEMARNAT-2010. The sampling was through free transects of approximately 1 km in the Barrancas La Escondida and El Paiste. A total of 59 families, 137 genera, 171 species and four varieties were obtained. The best represented families are Asteraceae, Fabaceae and Pteridaceae. According to the Chao 2 estimator, the sampling effort in the study area was 87%. Floristic affinity in Cerro del Veinte was greater with the Hoya de Rincón de Parangueo (38%) and Sierra de Pénjamo (32%). In addition, there are three new species reported for Guanajuato, Govenia lagenophora and Sacoila lanceolata (Orchidaceae) and Solanum edmundoi (Solanaceae). The taxa Cedrela odorata and Erythrina coralloides are included in NOM-059-SEMARNAT-2010.

The microbial community in an alkaline saline sediment of a former maar lake bed

The “Hoya del Rincon de Parangueo (HRP)” is a maar that contained a perennial alkaline lake that drained in the 1980s so that a sediment with high pH and extreme salinity remained. The aim of this work was to determine how the bacterial and archaeal community was controlled by these extreme conditions. Sediment samples were collected from the 0–20-cm layer along a crater-wide transect. Physicochemical characteristics and the archaeal and bacterial community were determined by analysis of the 16S rRNA through Illumina sequencing. The sediment samples had a pH 10 and an electrolytic conductivity (EC) that ranged from 29.8 to 74.4 dS m−1. Three archaeal and 37 bacterial phyla were detected with Euryarchaeota (relative abundance 62.7 ± 17.6%) dominating the Archaea, and Proteobacteria (28.2 ± 10.7%) and Actinobacteria (21.1 ± 6.4%) the Bacteria. The most abundant archaeal genus was Candidatus Nitrososphaera while Euzebya, Halomonas, KSA1 and Planctomycetes dominated the bacterial gene. Thaumarchaeota were enriched in sediment samples with a higher Pb content and Euryarchaeota in sediment with a higher Mg content, while Crenarchaeota and Candidatus Nitrososphaera were enriched in sediment with a higher sand, total N and organic C content. Proteobacteria were enriched in sediment with a higher organic C and total N, Si and sand content, while Bacteroidetes and Planctomycetes in sediment with a higher water holding capacity and clay and Mg content. Members of KSA1 and Euzebya were enriched in sediment with a lower EC, organic C and total N content. Although a large number of bacterial and archaeal groups were correlated significantly with a range of sediment characteristics, the sediment characteristics explained the variation of only two bacterial groups > 50% (TM6 and Desulfonatronospira) using the machine learning tool randomForest and none of the archaeal groups. Archaeal and bacterial functional guilds were dominated by ammonium oxidation and nitrite reduction. Although the different sediment samples were dominated often by similar bacterial and archaeal groups, the measured sediment characteristics explained little of the variation found between the sampling points. The high bacterial and archaeal diversity indicated that the site might be a source of unclassified species and phylotypes with specific metabolic capacities involved in the N and S cycles.

Extant microbial communities in the partially desiccated Rincon de Parangueo maar crater lake in Mexico.

Rincon de Parangueo is a maar where a perennial lake was present until the 1980s. A conspicuous feature of the lake's sediments is the presence of bioherms and organo-sedimentary deposits produced by microbial communities. The gradual lake desiccation during the last 40 years has produced dramatic environmental changes inside the maar basin, which resulted in the formation of a highly saline-alkaline system with extant microorganisms. In this paper we succinctly describe the geologic setting where the microbial communities have developed inside of the maar crater and the results obtained from high-throughput sequencing methods to characterize the microbial component (Bacteria, Eukarya and Archaea) in endolithic mats of calcareous sediments, and microbial mats and free-living microorganisms in the soda ponds. The studied sites displayed different microbial communities with a diverse number of phylotypes belonging to Bacteria and Eukarya, contrasting with a much less diverse component in Archaea. The sequences here detected were related to environmental sequences from sites with extreme life conditions such as high alkalinity (alkaliphiles), high salinity (halophiles) and high temperature (thermophiles). Moreover, our results indicate an important unexplored endemic microbial biodiversity in the vestiges of the former lake that need to be studied.

Changes in vegetation structure during the Pleistocene–Holocene transition in Guanajuato, central Mexico

To investigate the changes in the structure and composition of the vegetation during the Pleistocene–Holocene transition, pollen and macrocharcoal analyses were carried out on samples of sediments taken from a 14.5 m core from Hoya Rincon de Parangueo, a crater lake (maar) in Guanajuato, Mexico. Fossil pollen data from the core suggest that during the last glacial maximum (LGM) the climate in central Mexico was very wet and cold, and the vegetation was open cloud forest, and fires did not occur. During the Pleistocene–Holocene transition, vegetation diversity was high in the study area, but disturbance to vegetation was observed, indicating an open habitat with fewer trees. There was an abrupt change in the composition of the vegetation during the later Holocene, likely signalling a strong change in climate. During the early Holocene the area remained wet, but there was a trend toward drier conditions that became well established at the end of the middle Holocene and into the late Holocene. As a consequence, the structure of the vegetation changed, with more taxa suggesting dryer environments, lasting until the late Holocene, when human disturbance became an important factor affecting vegetation in the area.

Biohermal thrombolites of the crater lake Rincón de Parangeo in Central México

This work describes the distribution, macro and microstructures of modern microbialites deposited in the marginal facies of a Quaternary paleo-lake at Rincon de Parangueo, within the central trans-mexican volcanic belt. This paleo-lake formed after the volcanic eruption and maar formation that provided suitable conditions at its margins for substrate colonization and microbial proliferation. Vesicular thrombolites, grouped into domical and irregular clusters, were mapped, measured and analyzed. These microbialites are characterized by a 2 cm-thick stromatolitic crust and a thrombolitic matrix that accreted by carbonate precipitation. The stromatolitic crusts represent the last accretion stages at intertidal conditions before the complete evaporation of the paleo-lake. The asymmetrical distribution and preservation of these microbial deposits suggest that the rapid subsidence and tectonic deformation began before the lake completely dried out. The maar at Rincon de Parangeo represents not only an important record of recent geological processes in dynamic interaction with microbial processes under increasingly extreme alkaline conditions (pH between 10 and 10.6), but also a possible analogue for some Precambrian sequences. It provides an example of a rapidly transforming environment where macro and micro geobiological interactions directly influence biological succession.

The combined influence of Pacific decadal oscillation and Atlantic multidecadal oscillation on central Mexico since the early 1600s

Periodic droughts have been one of the most serious environmental issues in central Mexico since the earliest times. The impacts of future droughts are likely to become even more severe as the current global warming trend increases potential evaporation and moisture deficits. A full understanding of the mechanism underlying climate variability is imperative to narrow the uncertainty about future droughts and predict water availability. The climatic complexity generated by the combined influence of both Atlantic and Pacific forcings, however, causes considerable difficulty in interpreting central Mexican climate records. Also, the lack of high-resolution information regarding the climate in the recent past makes it difficult to clearly understand current drought mechanisms. Our new high-resolution δ18O record from Hoya Rincon de Parangueo in central Mexico provides useful information on climate variations since the early 1600s. According to our results, the central Mexican climate has been predominantly controlled by the combined influence of the 20-year Pacific Decadal Oscillation (PDO) and the 70-year Atlantic Multidecadal Oscillation (AMO). However, the AMO probably lost much of its influence in central Mexico in the early 20th century and the PDO has mostly driven climate change since. Marked dryness was mostly associated with co-occurrence of highly positive PDO and negative AMO between ∼1600 and 1900.

Structural evidence of enhanced active subsidence at the bottom of a maar: Rincón de Parangueo, México

Abstract Rincón de Parangueo is a Quaternary maar that has been recently desiccated. The crater was partially occupied by a soda lake, and near the shoreline microbialites have formed. Evaporites (mainly trona and halite) precipitated as the water level dropped. Active subsidence of the lake floor ( c. 24 m since 1980) produced countless structures close to the lakeshore, where deformation is extensional. Closer to the depocentre, in the western half of the basin, gliding/spreading produced folds and mud-injection domes. The most remarkable structure throughout the basin is a monocline that forms a ring-like, nearly continuous scarp, approximately 15 m high, which in the eastern half of the basin was produced as a fault-propagation fold developed above the buried diatreme–country rock boundary. A more diffuse (wider) monocline, locally associated with compressive structures, occurs in the western half of the basin. These structures are interpreted as having developed above a gently inclined, irregular lake sediment–country rock (andesite) interphase. The monocline was modified by high-angle extensional faults/fractures with large heaves/apertures. In the eastern half of the basin, there is a second (outer) scarp, approximately 13 m high, formed by a high-angle, listric, normal fault. Rollover antiforms occur in the hanging wall of this structure. Rincón is an example of centripetal gravitational gliding/spreading.

Active sinking at the bottom of the Rincón de Parangueo Maar (Guanajuato, México) and its probable relation with subsidence faults at Salamanca and Celaya

Rincon de Parangueo is a Quaternary maar that had a perennial lake until the 1980s. The lake was gradually desiccated as a consequence of drawdown in the Salamanca-Valle de Santiago regional aquifer and now functions as a playa-lake. In contrast with the features observed in other crater-lakes in the region (La Alberca, Cintora, and San Nicolas), which also dried up at the same time, the bottom of the Rincon crater displays clear evidence of active deformation associated with mass movement of lake sediments towards the depocenter inside the crater. The most conspicuous topographic feature is a 10 – 12 m high scarp parallel to the former lake coast. The scarp is produced by an annular shaped normal fault system, down towards the depocenter. Evidence of active mass movement is observed along the topographic scarp. Rotational slides associated with rollover anticlines and local grabens produced by antithetic faults are common on the eastern and northern parts of the scarp. Planar slides with open folds at their base occur at western part of the lake basin. Evaporites (trona, thermonatrite, eitelite, halite, and silvite) are abundant in the playa-lake sediments. Their presence makes us believe that a mass removal process is acting as a consequence of salt dissolution and infiltration of the brine towards the aquifer. This process, probably in conjunction with lake sediment compaction and/or diatreme subsidence, may explain the significantly higher fault displacement rate observed inside the crater ( ≈ 50 cm/year ) in comparison with active faults elsewhere in the Salamanca-Valle de Santiago aquifer ( ≈ 6 cm/year ).

Holocene climate change and human impact, central Mexico: a record based on maar lake pollen and sediment chemistry

This paper presents multiproxy (pollen, magnetic susceptibility, sediment chemistry) records from two maar crater lakes in the Valle de Santiago of Guanajuato, Mexico: Hoya San Nicolás and Hoya Rincon de Parangueo. Sediment cores from the two sites have basal dates of ca 11,600 and 9600 cal yr BP, respectively. The San Nicolás results show that the lake desiccated several times during the Holocene, and this resulted in the selective destruction of the less resistant pollen types. A comparative analysis of data from both sites indicates that during the earliest Holocene (ca 11,600–9000 cal yr BP) there were short term oscillations of wetter and drier climate; during the early Holocene (ca 9000–5700 cal yr BP) it was on average wetter; during the middle Holocene (ca 5700–3800 cal yr BP) drier; and during the middle to late Holocene (ca 3800–2200 cal yr BP) wetter. Increasing human disturbance during the late Holocene of environment obscures the climatic record. Agricultural activities in the area began as early as ca 5700 cal yr BP and intensified around 2400 cal yr BP.

First lacustrine varve chronologies from Mexico: impact of droughts, ENSO and human activity since AD 1840 as recorded in maar sediments from Valle de Santiago

We present varve chronologies for sediments from two maar lakes in the Valle de Santiago region (Central Mexico): Hoya La Alberca (AD 1852–1973) and Hoya Rincon de Parangueo (AD 1839–1943). These are the first varve chronologies for Mexican lakes. The varved sections were anchored with tephras from Colima (1913) and Paricutin (1943/1944) and 210Pb ages. We compare the sequences using the thickness of seasonal laminae and element counts (Al, Si, S, Cl, K, Ti, Mn, Fe, and Sr) determined by micro X-ray fluorescence spectrometry. The formation of the varve sublaminae is attributed to the strongly seasonal climate regime. Limited rainfall and high evaporation rates in winter and spring induce precipitation of carbonates (high Ca, Sr) enriched in 13C and 18O, whereas rainfall in summer increases organic and clastic input (plagioclase, quartz) with high counts of lithogenic elements (K, Al, Ti, and Si). Eolian input of Ti occurs also in the dry season. Moving correlations (5-yr windows) of the Ca and Ti counts show similar development in both sequences until the 1930s. Positive correlations indicate mixing of allochthonous Ti and autochthonous Ca, while negative correlations indicate their separation in sublaminae. Negative excursions in the correlations correspond with historic and reconstructed droughts, El Nino events, and positive SST anomalies. Based on our data, droughts (3–7 year duration) were severe and centred around the following years: the early 1850s, 1865, 1880, 1895, 1905, 1915 and the late 1920s with continuation into the 1930s. The latter dry period brought both lake systems into a critical state making them susceptible to further drying. Groundwater overexploitation due to the expansion of irrigation agriculture in the region after 1940 induced the transition from calcite to aragonite precipitation in Alberca and halite infiltration in Rincon. The proxy data indicate a faster response to increased evaporation for Rincon, the lake with the larger maar dimensions, solar radiation receipt and higher conductivity, whereas the smaller, steeper Alberca maar responded rapidly to increased precipitation.

Lower-Crustal Xenoliths from the Valle de Santiago Maar Field, Michoacan-Guanajuato Volcanic Field, Central Mexico

We report on a recent finding of granulitic and gabbroic xenoliths in the Rincon de Parangueo and La Cintura maars, within the Valle de Santiago volcanic field. The field is formed by several maars, cinder cones, and shield volcanoes and is located at the northern sector of the extensive Michoacan-Guanajuato volcanic field, characterized by abundant Neogene cinder cones and medium-sized shield volcanoes. The maars are distributed along a belt elongated NW-SE, apparently related to a regional fault system that has been documented in the west-central sector of the Trans-Mexican volcanic belt (TMVB). Two types of xenoliths have been distinguished—i.e., hypersthene-diopside granulites and gabbroic xenoliths—which are present in the Rincon de Parangueo and La Cintura maars, respectively. The silica content in the granulites has a narrow range between 46.9 and 50.9 wt%, plagioclase crystals are fractured and display reaction borders, and crystals appear to have grown slowly and show no compositional zoning. Silica in the gabbroic xenoliths ranges from 45.7 to 47.5 wt%. Chemical composition is similar to mafic and intermediate orthogneiss xenoliths from the San Luis Potosi maars of the Central Mexican Altiplano. An Sm/Nd model age for the granulitic xenoliths from Rincon de Parangueo maar of 1.5 Ga supports the presence of a Precambrian lower crust. This finding challenges current models of crustal structure in central and western Mexico. The Valle de Santiago field represents the westernmost lower-crustal xenolith locality reported thus far. It lies within the Guerrero terrane that has been considered as a collage of island arcs built on oceanic lithosphere and accreted to the North American plate during late Mesozoic time. Our results support a composite nature for the Guerrero terrane and extend the limit of possible granulitic lower continental crust farther to the west of the Central Altiplano province, beneath the TMVB, than currently considered (i.e., to the east of the Guerrero terrane).

Late holocene human impact on lake basins in central mexico

AbstractPalaeolimnological investigations in the volcanic highlands of Central Mexico (19°N) have yielded clear evidence of environmental degradation associated with episodes of forest clearance and agricultural expansion during the last 3500 years. Preliminary results are presented from five lake basins situated at altitudes of 1700 to 2575 m a.s.l., along a gradient of decreasing aridity and temperature from north to south: Hoya San Nicolás de Parangueo (Guanajuato); La Piscina de Yuriria (Guanajuato); Pátzcuaro (Michoacán); Zacapu (Michoacán) and Upper Lerma (Estado de México). Samples from sediment cores and pits are being analyzed for loss‐on‐ignition, magnetic susceptibility (X and Xfd), major cations, total P, C/N, carbonate content, δ13C, δ18O, diatoms, pollen, and charcoal content. Evidence for disturbance is provided by increases in non‐arboreal pollen types, especially maize (Zea mays), peaks of X, Xfd and charcoal; increased concentrations of elements associated with soil material such as Al, Fe, Ti, and P, and diatoms indicative of cultural eutrophication.Pátzcuaro, Hoya San Nicolás, Zacapu, and Upper Lerma show an initial phase of disturbance dating from ca. 3500 to 1400 yr B.P., reflecting the widespread adoption of maize cultivation during the Preclassic. A later, more intense phase is recorded in all the basins. In Hoya San Nicolás, La Piscina de Yuriria, Zacapu, and Pátzcuaro, which lay within, or on the margins of the Tarascan state, this episode dates from Postclassic to Hispanic times (<1100 yr B.P.). In contrast, disturbance in the Matlatzincan area (the Upper Lerma Basin) was apparently more continuous, culminating during the late Classic to early Postclassic (ca. 1400‐700 yr B.P.).