Approximately 20km north of Volcan Socompa is the El Negrillar field. Lavas from this field are typical of other basaltic andesite to andesite monogenetic lavas thoughout the Central Andes but show a more dendritic outcrop pattern. They occur over an area of about 15 x 20km and are related to a series of prominent regional faults trending dominantly north-south. On TM images the lavas show varying states of preservation indicating different ages. The few dark, fresh-looking lavas are obviously the youngest but even these are older than the débris flow from Volcan Socompa which is thought to be about 7,200 years old (Francis and Wells, 1988). Deruelle (1982) and Harmon et al., (1984) inlcude lavas from this field as part of regional geochemical studies and show that they have a wide range of compositions.
Deruelle, B. 1982. Petrology of Plio-Quaternary volcanism of the south central and meridional Andes. Jour. Volcanol. Geotherm. Res., 14, p77-124.
Francis, P.W., and Wells, G.L., 1988. Landsat Thematic Mapper observations of debris avalanche deposits in the Central Andes. Bulletin of Volcanology, 50(4): 258-278.
Harmon, R.S., and 8 others, 1984. Regional O-, Sr-, and Pb-isotope relationships in late Cenozoic calc-alkaline lavas of the Andean Cordillera. J. Geol. Soc. Lond. 141, no. 5, p803-822.