Revistes Catalanes amb Accés Obert (RACO)

Peat-forming plants in the Maastrichtian coals of the Eastern Pyrenees

Sheila Villalba Breva, Carles Martín-Closas, J. Marmi, B. Gómez, Ma. Teresa Fernández Marrón

Resum


The Lower Maastrichtian of Fumanya and neighbouring localities of the Vallcebre syncline (Eastern Pyrenees, Catalonia) provide the first taphonomic evidence for the hypothesis that cheirolepidiacean conifers were significant precursors of Maastrichtian Pyrenean coal. Most Frenelopsis-rich lignite beds do not bear rootlet marks, suggesting that the original peat was detrital. Sedimentological and taphonomic evidence indicates deposition in the margins of a lagoon after the transport of the cheirolepidiacean remains by flotation. The same parautochtonous assemblage includes complete impressions Sabalites longirhachis leaves and large impressions of logs attributed to the same palm trees. Other parautochthonous or allochthonous plant megaremains include extremely rare cycadalean and monocot leaves and abundant minute angiosperm seeds. Rootlet marks associated with thin lignite beds occur at the top of some charophyte limestones. The charophyte association, dominated by in situ accumulation of Peckichara and Microchara gyrogonites, suggests that these limestones were deposited in shallow, freshwater lakes and that the corresponding peat mires were limnic rather than paralic in nature. The botanical affinity of plant remains associated with these root-bearing lignites is uncertain. Palynological analysis showed abundant bisaccates, with less abundant fern spores and freshwater algal oospores. Locally, the abundant rootlet marks were associated with large brush-like rooting structures attributed to Sabalites longirhachis palms. Our results show that, at the beginning of the Maasrichtian, cheirolepidiacean conifers were still significant peat-producing plants, although, unlike analogous Lower Cretaceous ones, they shared this role with rare angiosperms, such as palms.

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