Abstract
In Faial Island (Azores Archipelago, North Atlantic Ocean), charcoalified and mummified wood fossils have been reported within late Holocene (Meghalayan) pyroclastic deposits from the Caldeira Formation. Due to their recent age, a detailed study conveys a snapshot into Azorean palaeophytodiversity and palaeovegetation, ca. 7–5 centuries before the arrival of Portuguese settlers to the Azores Islands. Here we provide the first detailed anatomical and taxonomical study of these wood fossils. In total, 41 samples were collected from seven localities, mainly from a ~1200 yr BP ignimbrite. Field work revealed autochthonous and paraautochthonous assemblages, with tree trunks in upright position. The anatomical study of the fossil woods resulted in the identification of Juniperus brevifolia, Laurus azorica, Myrsine retusa, Morella faya, Picconia azorica, Prunus lusitanica subsp. azorica, and Vaccinium cylindraceum. Two fossil assemblages are comparable to the proposed potential natural vegetation (PNV) for the Azores. Surprisingly, P. lusitanica subsp. azorica was the second most abundant fossil wood suggesting that this tree was more abundant in a recent past in Faial Island and probably in the archipelago. This is corroborated by historical accounts, and its modern scarcity was certainly anthropically driven. Identifying Holocene plant macrofossils is essential to properly reconstruct oceanic islands terrestrial palaeoecosystems, especially where forests with high percentage of entomophilous taxa are underrepresented in palaeopalynological limnic record. Further work is necessary to reconstruct Faial Island and Azores archipelago palaeovegetation which is essential to provide an ecosystem base-line for restoration and management.
Highlights
The interaction between explosive or effusive volcanic events and vegetation may provide ideal taphonomical environments for plants to be buried and preserved as charcoals or mummifications (e.g. Fritz, 1986; Spicer, 1989; Hudspith et al, 2010; Scott, 2010; Mustoe, 2018)
Charcoalified wood was studied and identified under a reflected light microscope (LM), and each sample studied in transverse surface (TS), radial longitudinal surface (RLS) and tangential longitudinal surface (TLS) sections
The east site (Fig. 3C–E) outcrop, at an elevation of 897 m a.s.l., displays 4 breccias separated by paleosols or ero sional unconformities; a wood sample from the palaeosol underlying the top breccia was radiocarbon dated at 1660 ± 45 yr BP (ICEN-994), while the west site (Fig. 3A–B) corresponds to a small stream valley, at an elevation of 977 m, that exposes a breccia covering a palaeosol rich in trunks, one of which was dated at 1820 ± 45 yr BP (ICEN-972)
Summary
The interaction between explosive or effusive volcanic events and vegetation may provide ideal taphonomical environments for plants to be buried and preserved as charcoals or mummifications (e.g. Fritz, 1986; Spicer, 1989; Hudspith et al, 2010; Scott, 2010; Mustoe, 2018). From a volcanological point of view, the degree of charcoalification and re flectance can provide insights on the palaeotemperature of the volcanic event that buried the wood (e.g. Scott and Jones, 1991b; Scott and Glasspool, 2005; Hudspith et al, 2010). I.e. almost unaltered wood with preservation of the original matter (Mustoe, 2018), can be preserved within cold phreatomagmatic deposits (e.g. Góis-Marques et al, in press). Charcoal and mummified wood found associated with volcanic deposits have been used worldwide to date late Quaternary volcanic eruptions (e.g. Bryson et al, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
