Flotation versus dry sieving archaeobotanical remains: A case history from the Middle Horizon southern coast of Peru

Abstract

During excavations at the site of Casa Vieja located in the Peruvian coastal desert, archaeological plant remains were systematically collected to assess whether it is more productive and informative to sieve sandy sediments in dry environments or to process such samples by water flotation, a persistent methodological concern. At Casa Vieja, dual subsamples were collected and analyzed using both of these procedures. For dry, sandy sediment conditions, each processing strategy was found to yield a different view of the botanical remains. Dry sieving recovers more of the larger plant specimens whereas water flotation yields more of the smaller-sized material. These results should be incorporated into archaeological research designs in the future, especially for desert environments. IntroductionThis project was designed to determine if archaeologists are collecting and processing archaeological plant remains effectively in dry, desert regions, specifically along the drier parts of the South American west coast. In 1995, excavations in a small residential settlement were conducted in the Ica River Valley of Peru to study plant access and local food production. Due to the lack of a clear protocol for processing the collected sediment samples for such a study, a dual processing procedure was devised that consisted of both dry sieving and water flotation with the purpose of determining which technique is better suited for this environment. Archaeobotanists use flotation to recover carbonized plant material while those working in dry, sandy conditions may adopt a recovery strategy that favors dry sieving over flotation in order to collect desiccated remains. Little is known, however, about the relative efficiency of the two different recovery methods. Our study presents concrete results as to the advantages and disadvantages of both methods and offers insight into how archaeological projects excavating in dry, sandy conditions can modify their archaeobotanical processing strategies to ensure optimal recovery. Casa Vieja (ca. A.D. 600-1000) is a late Early Intermediate Period (EIP) and early Middle Horizon (MH) site located in the desert of the Lower Ica Valley.It offers excellent preservation conditions, presenting a prime opportunity to investigate effective ways to extract and identify archaeobotanical samples from sandy sediments. Most South American archaeobotanical research has concentrated on highland or tropical lowland areas with much of the focus on early time periods. Archaeological projects in those regions deal with clay content and regular clumping of the soil and tend to float the site sediment. Ironically, until very recently less archaeobotanical information was available for the coast of Peru, where organic materials are found in large quantities and in excellent condition. Casa Vieja, for example, has yielded much archaeobotanical information: discussion concerning major changes in plant use during the period of Wari presence in the Ica Valley is presented in Cook and Parrish (2005). Roqué Gamarra and c...

Botanical Evidence of Paleodietary and Environmental Change: Drought on the Channel Islands, California

“…Significant numbers of carbonized nutshells, seeds of manzanita and manroot, and even corms/bulbs are present in many of these dry-screened samples. We find precedent for this dual-collection strategy in various regions with good preservation (Chiou et al 2013;Hageman and Goldstein 2009). The loci represented here are shell-rich, sandy-soil, toss-zone areas outside defined house depressions.…”

Análisis morfométrico de las semillas del género Capsicum (Solanaceae) en el Perú prehispánico

“…Las investigaciones arqueobotánicas en Sudamérica han empleado la morfometría como herramienta de análisis para estudiar estos cambios en diversos órganos vegetales (semillas, hojas, tallos, flores, raíces, entre otros) (Bruno & Whitehead, 2003;Bruno, 2005;Langlie, 2019;Martínez et al, 2015;Morales-Santos et al, 2017;Planella et al, 2012;. Además, su recuperación en regiones secas y desérticas ha favorecido la buena preservación de los órganos diagnósticos de estudio (semillas, hilum, testa, entre otros) que ha coadyuvado el desarrollo de las investigaciones (Roque et al, 2003;Cook & Parrish, 2005;Chiou et al, 2013;Dillehay et al, 2017).…”