`Fish-Tail' Projectile Points and Megamammals: New Evidence from Paso Otero 5 (Argentina)

Article excerpt

Introduction

Recently, archaeological knowledge of early human occupations in the Pampean region of Argentina has improved through new archaeological sites dated to c. 10,000-11,200 BP. Archaeological research carried out in Tandilia Serrana Area, at sites such as Cerro El Sombrero and Cerro La China (Flegenheimer 1980; 1986-87; Zarate & Flegenheimer 1991), as well as Cueva Tixi, Los Pinos, Burucuya and Cueva La Brava (Mazzanti 1996; 1999), have yielded significant archaeological contexts related to the Pleistocene-Holocene transition containing the so-called `fish-tail' projectile points. In the grasslands of the Interserrana Bonaerense Area the situation is quite different because only two sites can be related to the Pleistocene-Holocene transition: Arroyo Seco 2 (Politis 1997) and the recently excavated Paso Otero 5 (Martinez 1997).

The objectives of this paper are to summarize the results obtained from Paso Otero 5 (Pampa Humeda subregion, Pampean region, Argentina) and to discuss their contribution to the knowledge of projectile points and megamammals related to early human occupations in southeastern Buenos Aires Province. The so called `fish-tail' projectile points have played a particularly important role in South American prehistory, given the fact that they have been used as cultural and chronological markers in monitoring the dispersal of early hunter--gatherers (see discussion in Nami 1997 & Politis 1991). The presence in this archaeological context of a good record of extinct megamammals also raises the issue of the behavioural implications of the management and procurement of these species and the impact of humans on processes of extinction and survival of megamammals into the Holocene (see Politis & Gutierrez 1998).

Background information: Paso Otero 5

The Paso Otero 5 site (38 [degrees] 12'08"S/59 [degrees] 06'58"W) is located in the middle basin of the Quequen Grande river (Necochea District) in the Interserrana Bonaerense Area, a grassland plain surrounded by the Ventania and Tandilia mountain ranges (FIGURES 1 & 2). The site was found on the right bank of the river in 1994, when a concentration of burned and non-burned megamammal bones was recorded projecting from the bank, suggesting the presence of an archaeological site. Subsequently, three excavation seasons were carried out from 1995 to 1997, covering an area of 20 sq. m (Martinez 1997).

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The stratigraphic sequence in the middle basin of the Quequen Grande river is composed of sediments of the Lujan Formation, which in turn consists of the late Pleistocene Guerrero and the early to middle Holocene Rio Salado Members (Tonni & Fidalgo 1978). The former consists of fluvial and aeolian facies and the latter is a stratified fluvial deposit that records a pattern of alluviation-stability-alluviation (Johnson et al. 1998). The Rio Salado Member is formed from lagoons and swamp deposits. Diatomaceous deposits are also recorded in different parts of the basin (Zarate et al. 1998: 139). In Paso Otero 5, the sedimentary column of this member shows six periods of landscape stability represented by the development of buried `A' horizons (FIGURE 3). The sixth stabilization surface (Ab6), a palaeosoil named Puesto Callejon Viejo that separates the two members of the Lujan Formation, is placed on the transition from the Pleistocene to the Holocene. With the exception of a few isolated items present in the contacts between Ab6 and the Rio Salado and Guerrero Members, the archaeological de posit was recorded within this buried `A' palaeosoil (Holliday et al. forthcoming; Martinez 1997).

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Lithics

Forty-seven lithics have been found, among which fine-grained quartzite predominates (60.8%), with some basalt and chert. The procurement of raw materials such as quartzite and chert was carried out in the Tandilia hills (50-70 km northward), while basalt probably came from the Atlantic coast. …