Systematics of Miocene angiosperm woods from the Panama Canal, and their palaeoenvironmental implications

Oris Rodriguez Reyes

Research output: ThesisDoctoral Thesis

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Miocene fossil woods exposed during the recent widening of the Panama Canal are described and their palaeoecological, palaeoclimatic and biogeographic implications are discussed. The woods occur in the Cucaracha Formation (early to mid-Burdigalian, 18 – 20 Ma) and comprise (1) a forest of charred and silicified stumps preserved in growth position by a pyroclastic flow and (2) calcareous permineralised trunks, bored by Teredolites and transported within fluvio-estuarine channel deposits. Woods were identified using a searchable authoritative online database (Inside Wood) and through detailed comparison with modern woods, mostly at the Jodrell Laboratory, Kew, UK. The two assemblages differ at genus-level, and to some extent, family-level. The permineralised wood assemblage contains dicots and is dominated by Malvaceae with some Leguminosae, Cannabaceae and Elaeocarpaceae. It includes representatives of several extant genera tolerant of flooding and exposed coastal conditions, consistent with the estuarine setting inferred from the geological evidence. In contrast, the charcoalified wood assemblage contains monocot palms (Arecaceae) but also includes dicots (Leguminosae, Malvaceae, Sapotaceae, ?Melastomataceae, Meliaceae) and dicot indeterminate forms. The extant relatives of this assemblage include a mixture of coastal and forest interior taxa representing a more diverse floodplain forest. Reflectance data from the charred stumps indicate that entombing pyroclastic flows reached minimum temperatures that ranged from 490 – 505ºC. Palaeoclimatic inferences, based on anatomical comparison of fossil woods and present-day woods and floras from Panama, suggest that Miocene forests were somewhat cooler and drier than 3 modern equivalents. The fossil wood assemblages contain several taxa endemic to South America, despite Panama being part of the North American continent in Miocene times. This implies that the collision of the Americas, which was traditionally thought to have occurred around 3 – 4 million years ago (mid – to late Pliocene) may have begun much earlier, with intercontinental exchange of tree species beginning by 18 – 20 Ma.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Falcon-Lang, Howard, Supervisor
  • Collinson, Margaret, Supervisor
Thesis sponsors
Award date1 Mar 2015
Publication statusUnpublished - 4 Mar 2015


  • Miocene
  • Panama Canal
  • woods
  • systematics
  • permineralised
  • charcoalified

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