Use of sediments and soils (paleosols) in construction fills of La Joya archaeological site, Veracruz, Mexico: micromorphological evidence (original) (raw)
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Sedimentological characterization of palaeo-soils in the northern part of the Basin of Mexico
Quaternary International, 1997
Superficial or buried soils arc important palaeostratigraphic indicators that have been poorly studied in the Basin of Mexico. This paper summarizes soil genesis and evolution based on the study of 15 soil profiles with palaeosol layers. An environmental morphogenetic and pedological sequence was established, based on granulometric, micromorphological, geochemical and field soil studies to identify the properties and characteristics of the pedogenetic environments in which they were formed. Results indicate two continuous and recurrent phenomena which altered the genesis of the soils, they are: (a) Torrential erosive processes under tectonic influences and arid conditions, and (b) Volcanic deposits that buried and fossilized soils. Both processes interrupt the evolution and sequence of soil profiles. Consequently, from the upper talus slopes to the lower portions stretching the length of the central lowest plains there are many palaeosoil discontinuities, that have not been considered into stratigraphic studies of the lacustrine plains.
Boletín de la Sociedad Geológica Mexicana, 2019
The activities carried out by preindustrial agricultural societies, are not usually considered as important factors of soil degradation. Nonetheless, repetitive human daily activities for hundreds of years can substantially transform the natural properties of the soils. At the site of La Playa, Mexico, the activities of early farmers modified the landscape and had an important role in the physical transformations of the natural soil features. This paper depicts the characteristics of La Playa paleosols, which was the living surface of the Early Agriculture Period community (40001800 cal. years BP) and we discuss the influence of daily subsistence activities on the soil. The soil features (structuring, differentiation of horizons, texture--in field and laboratory, color, porosity, stoniness, magnetic properties, organic carbon content, carbonation, presence of cutans, nodules and / or concretions, among other pedological features) of three profiles with pedosediments (paleosols interbedded with sediments) formed during late Holocene are discussed. Our study suggest that La Playa Fluvisols are poorly developed and were formed with alluvial deposits (largely composed of reworked soils). The pedogenic properties indicate an overlapping developed during short time periods of stability, under arid conditions of the last 4000 years. The uniformity of the features in all the studied profiles indicate similar pedogenetic conditions across the site area. The micromorphological and magnetic properties clearly show that the soil was deeply disturbed by human activities, mainly by roasting features to process food, crematories and grave digging to bury the death and removing soil for several agricultural activities.
Quaternary International 365 (2015):135-149
In the state of Sonora, Northwest Mexico we have recognized the existence of paleosol units of Late Pleistocene/Early Holocene age (13,000 to 10,500 Cal years BP) at several archaeological sites with Paleo-indian occupation (e.g. La Playa, Fin del Mundo, El Bajio, El Aigame and El Arenoso). The few paleoenviromental reconstructions from the region indicate that the end of the Pleistocene was dominated by temperate climate that promoted the establishment of the first people in coexistence and interaction with the Pleistocene megafauna (later extinct). The study of the spatial distribution of various soil units developed during late Pleistocene in the region provides information about local environmental settings of the initial peopling of Sonora. Several pedosedimentary sequences were analyzed in the different parts of the Sonora state, the age control in which was provided by archaeological and paleontological findings and/or by the radiocarbon dating of carbonates and paleosol humus. So far two trends of the Late Pleistocene pedogenesis have been identified. The profiles located in the south, center and north of the state are dominated by red soils (earlier referred as Big Red in the archaeological literature) whose characteristics are represented by the Red San Rafael Paleosol (SRP) –identified at the archaeological site of La Playa. The properties of SRP in the lower part of the profile (e.g. rubification, accumulation of clay, higher values of magnetic susceptibility, illuvial carbonates, and redoximorphic features) are indicative of a more humid environment. Above them is a late Holocene polycyclic sequence of soils with morphological characteristics display a more incipient development. In contrast with the sequence described above at El Arenoso, north of Caborca, were identified sequence of gray soils. Two paleo-soil were formed in an alluvial sediments. At the Cantera profile (CTP) and El Arenoso profile (ARP) paleosols are represented by Bgk horizons and evidence of weathering and neoformation of clay and amorphous silica, redoximorphic processes and illuvial accumulation of carbonates. We explain the differences of north-western profiles by specific geomorphic conditions which imply limited soil drainage and possibility of overmoisturing. These processes indicate alternating a humid environment (indicated by the mineral weathering, rubification, clay formation and reductomorphic processes); and dry periods (with possible accumulation of carbonates). Despite regional differences of the late Pleistocene paleosols, the comparison with the Holocene soils demonstrate clear trend towards desertification in the region. The first people that inhabit Sonora during late Pleistocene times found a more tempered and better weather that they encounter in the north, but the next generations saw a rapid aridity of the region with the formation of the Sonoran Desert in early Holocene times.
Late Holocene paleopedological records contained in tephra from El Chichón volcano, Chiapas, Mexico
Catena, 2007
High rates of pedogenesis on unconsolidated volcanic materials imply the accelerated generation of the soil memory. The purpose of this research was to extract the high resolution (centennial scale) paleopedological records from the Late Holocene paleosols of the El Chichón volcano formed during the last 2000 years. We studied buried monogenetic Andosols on the dated tephras and a pedocomplex formed from a set of thin ash layers deposited on older Acrisol derived from shales. Particle size distribution, DCB-extractable Fe, oxalate-extractable Fe, Al and Si, sand and clay mineralogy, organic carbon content and stable C isotope composition in humus were evaluated and interpreted as the elements of the soil memory. However, some differences were found in properties of two buried soils, especially in the kind of A horizons. We attribute such differences of individual Andosols to be caused by ancient human impact because it has been demonstrated that humid conditions persisted during the last 1300 years. Thus the drought that was supposed to provoke the collapse of the Maya civilization at the end of I millennium A.D., should have been a short-term event, below the resolution of this paleopedological record. The Andic Acrisol pedocomplex demonstrated the domination of the humid tropical climate over longer time intervals (probably major part of the Holocene) with possible minor dry episodes.
Geoarchaeology of an Aztec dispersed village on the Texcoco piedmont of Central Mexico
Geoarchaeology, 1997
Analysis of the microstratigraphy, geomorphology, and soils within an Aztec site in the piedmont of Texcoco provides information on the ecological context of the dispersed village during the Late Aztec phase (A.D. 1350-1520). Two erosional phases are identified, the first in the period between A.D. 500 and 1000, and the second in the 1600s. The two erosional events are correlated with the transition from dispersed settlements, with relatively high population density, to nucleated settlements marking a decline in population. Land reclamation by Aztec settlers is attested by the remains of the semiterracing system of metepantli and rock-faced terraces, which are features discussed in the context of anthropogenic soils identified within the site.
Soil-geomorphology and “wet” cycles in the Holocene record of North-Central Mexico
Geomorphology, 2008
The distinction between the impact of climatic periodicities or land-use practices on soil erosion is an important issue for Pre-Hispanic and Colonial Mexico. That question can best be addressed by first documenting the dynamics of changing “wet” cycles during the Holocene in the central Mexican region between the northern limits of Pre-Hispanic agriculture and its southern margins in northwestern Chihuahua. Consequently the Laguna Project targeted a 125,000 km2 sector of North-Central Mexico, 250 km from north to south and 500 km from east to west, from Saltillo to Durango. Some 40 sedimentary profiles with multiple cumulic soils were studied in the field and laboratory, supported by 163 conventional 14C and AMS dates on charcoal and soil humates. We distinguish: (1) wet floodplains (with humic paleosols, redox phenomena reflecting high water tables, channel-ponding sequences, and interbedded tufas) that imply aquifer recharge, sustained base flow, and mainly low-energy conditions; and (2) high-energy pulses of discharge that mobilized cobble gravels or forced channel entrenchment (“gullying”) and were tied to episodic, excessive rains that promoted valley and slope instability. In between such “wet” cycles and recurrent disequilibrium events, climate was similar to today, probably less humid, with limited geomorphologic change or slow soil formation.“Wet” cycles were rare at the end of the Pleistocene, but prominent during the Holocene. Disequilibrium proxies became common and dramatic after 2500 BP. The drainages from the Eastern and Western Sierra Madres responded in phase, but varied in detail. Around AD 1050–1200 “natural” erosion led to loss of soil organic carbon, as alternating severe droughts and heavy rains destroyed the ground cover and led to ecological aridification, well before arrival of Spanish miners and settlers. The evidence that human activity triggered Pre-Hispanic or Colonial erosion in Central Mexico should therefore be re-evaluated. Global comparisons and interpretations are discussed, but with caution, since no single theory can explain the whole of the record. The soil-geomorphology geoarchive of North-Central Mexico primarily is an environmental history of alternating “wet” cycles, rather than of sustained wet or dry climates. The critical differences between “soaking” and “excessive” rains, with their respective impacts, may be due to switching between winter and summer storm categories.