Boletín de la Sociedad Geológica Mexicana Volumen 71, núm. 2, 2019, p. 519‒541 http://dx.doi.org/10.18268/ BSGM2019v71n2a17

Late Holocene human activities and their impacts on the soils and sediments at La Playa, Sonora, Mexico

Tamara Cruz-y-Cruz^1,*, Guadalupe Sánchez², John Carpenter², Sergey Sedov³,

Hermenegildo Barceinas-Cruz⁴, Elizabeth Solleiro-Rebolledo³

¹Programa de Becas Posdoctorales en la UNAM, Becaria del Instituto de Investigaciones Antropológicas, asesorada por el Dr. Terrazas.

²Centro INAH Sonora, Jesús García S/N, La Matanza, 83080 Hermosillo, Sonora, Mexico.

³Instituto de Geología, UNAM, Ciudad Universitaria, 04510 CDMX, Mexico.

⁴Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 CDMX, Mexico.

* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

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 were the living surface of the Early Agriculture Period community (4000 – 1800 cal 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 suggests that La Playa Fluvisols are poorly developed and were formed with alluvial deposits (largely composed of reworked soils). The pedogenic properties indicate that 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. 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 dead, and removing soil for several agricultural activities.

Keywords: Soil degradation, human activities, magnetic properties, paleosols, Sonora.