Geomorphic context of the prehistoric Huastec floodplain environments: lower Pánuco basin, Mexico

Abstract

The Huasteca of eastern Mexico is the northern extent of prehistoric Mesoamerican complex culture. In comparison to other major Mesoamerican culture regions, much less is known about the physical environment of the Huasteca. This paper examines the structure, scale, and dynamics of floodplain environments in the lower Pánuco basin, the major physical setting in which prehistoric Huastec resided. Data sources included total-station surveying, topographic and historic maps, particle size of floodplain deposits, and analysis of air photos and satellite imagery. Study results illustrate the geoarchaeological significance of spatial changes in floodplain environments. Valley profiles grade from concave to planar in the upper portions of the study area, where the Rio Moctezuma exits the mountains, and are characterized by low floodplain relief and active floodplain reworking. Thus, the narrow valley and dynamic fluvial environment would not have been suitable for sustained habitation. The lower Moctezuma and Pánuco valleys have a convex profile with low rates of floodplain reworking, relict meander belts, and floodplain environments that are more prone to flooding. The Pánuco valley would have represented a stable environment suitable for habitation along wide natural levees, which are perched above extensive flood prone backswamps with buried relict channels. The absence of multiple oxbow lakes coupled with the association of older Huastec material culture along the active channel suggests that low rates of floodplain reworking have persisted since the late-Holocene, and help to constrain the age of a meander belt for a major river system. Study results provide a framework for future geoarchaeological research within the Huasteca.

Introduction

Prehistoric settlements were located along rivers for resources, transportation, and fertile soils for agriculture, and there is a close correlation between human adaptive patterns and the morphology and dynamics of floodplain environments [7], [9]. Alluvial geoarchaeology depends on an understanding of floodplain morphology and channel dynamics [4], [6]. Although floodplains are subtle landscapes, each type of floodplain deposit is hydrologically discrete, and therefore has distinct environmental implications to humans. The risk of flooding and amount of arable land are two fundamental characteristics of floodplain environments that must be met for sustained habitation, but the risk of floodplain erosion is also important [6], [39]. Excluding low Holocene terraces, natural levees are the optimum site for habitation due to the lower risk of flooding, and also because they provide arable land for agriculture [7], [10], [21], [22], [39], [45]. In many large river systems natural levees grade to floodplain bottoms, which may include backswamps. Prehistoric agriculture had long utilized the transition between levee backslopes and backswamps for intensifying agricultural production [10], [14], [67]. Within a single river system natural levees vary in their width and height above the floodplain bottoms, presenting considerable diversity in the land suitable for human habitation and manipulation. Natural levees are eroded at channel cutbanks, resulting in significant variability in the size of natural levees. In addition to representing a more hazardous setting [53], the erosion of levees also results in the loss of older cultural materials, and can therefore bias the archaeological record [24]. Some river valleys include extensive relict channel systems. The associated natural levees potentially increase the amount of space suitable for human habitation, or in the case of buried channels potentially serve as a cultural archive. Within a large watershed systematic changes in fluvial processes results in spatial variability in the size of natural levees, floodplain hydrology, and in channel erosion [32], [34].

Prehistoric societies residing within alluvial settings adjusted in response to floodplain hazards [53], or in the case of more complex societies, imposed their own culturally specific styles of technology and innovation to overcome specific floodplain conditions [6], [9]. The Huasteca culture region (Fig. 1) represents the northern extent of prehistoric Mesoamerican complex society [12], [15]. The lowland Huasteca is located along the Mexican Gulf Coastal Plain of eastern San Luis Potosi, northern Veracruz, and southern Tamaulipas, and is strongly associated with the floodplain environments of the lower Pánuco basin [15], [56]. The large river valleys comprising the lower Pánuco basin represent major physiographic alignments within the Huastec culture region. Moreover, they represent the landscape matrix within which the lowland Huastec resided and interacted, and thus were fundamental components of their physical environment. This study provides an overview of the morphological framework and floodplain dynamics of the lowland Huastec environment. The study examines the fluvial environment the Huastec confronted, and may serve as a framework for more extensive Holocene geoarchaeological research.