Obsidian provenance studies in Colombia and Ecuador: obsidian sources revisited

What is it about?

The field occurrences, elemental compositions and formation ages of Colombian and Ecuadorian obsidians are revisited. It is shown that the regional sources of this raw material are linked to two major volcanic structures: the Chacana and the Paletara calderas, localised on the eastern cordillera of Ecuador and on the central Andean cordillera of south Colombia respectively. Seventy-two samples were analysed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS) and/or particle induced X-ray emission (PIXE). The same 10 types of elemental compositions were identified independently from ICP and PIXE. Four of these types were previously unknown. The formation ages of these obsidians previously determined by fission tracks dating are in the range 0.17–1.58 Ma at Chacana and 3.46–4.27 Ma at Paletara. Most Colombian and Ecuadorian pre-Hispanic artefacts present elemental compositions compatible with a Chacana- or Paletara-derived origin of the raw material. However, some of them present fission track ages discordant with the present-day known obsidian occurrences, which implies that the regional source inventory is not yet exhaustive.

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