Mid‐Holocene vegetation dynamics in the Tejo River estuary based on palaeobotanical records from Ponta da Passadeira (Barreiro–Setúbal, Portugal)

Abstract

This paper presents the results of pollen and charcoal analyses carried out in the sedimentary formation of Ponta da Passadeira, south of the Tejo River estuary, Portugal. The data provide information regarding the evolution of the coastline and ecosystem of the estuary during the mid and late Holocene. The study focuses on a group of upright woody fossilized tree remains that, together with those identified earlier by García-Amorena et al. (2007), form part of the fossil forest of Ponta da Passadeira. Eight remains were identified as Pinus pinaster, four as Pinus pinea and one as Pinus sp. Two specimens of these species were dated to 6523 and 5805 cal. a BP. Pollen analysis was undertaken in a clay layer located at the same point as the fossil forest, which is currently below sea level; the base of the clay layer was dated to 4906 cal. a BP. The pollen spectra reflect the dynamics of the vegetation that grew on this deposit, whereas the sporopollinic input masks the contribution of the regional vegetation. Wood charcoal remains recovered at an adjacent Final Neolithic settlement were also analysed, and a Pinus sp. specimen was radiocarbon dated to 5050 cal. a BP. The correlation amongst the three records provides key ecological markers for the understanding of the evolution of coastline ecosystems, and helps to clarify and understand the Holocene sea rise on the Atlantic seaboard of Iberia. The geographical location of Ponta da Passadeira is strategic because it enables a more clear definition of the configuration of landscapes that show an inflection point in this area of central Portugal.Luis Gómez-Orellana (luis.gomez-orellana@usc.es) and Pablo Ramil-Rego, GI-1934-TB.

Aeolization on the Atlantic coast of Galicia (NW Spain) from the end of the last glacial period to the present day: Chronology, origin and evolution of coastal dunes linked to sea‐level oscillations

“…This would already indicate that the continental environments on this coast were affected by dunes. This hypothesis is supported by the submerged forests that appear under the intertidal sands of aeolian origin during storm events, along the coast of Galicia and North‐Central Portugal (García‐Amorena et al, 2007; Gómez‐Orellana et al, 2014; Granja & Soares de Carvalho, 1995; Ribeiro et al, 2011; Vidal‐Romaní & Grandal‐d'Anglade, 2018) (Table 2, Figure 11), as well as the French Atlantic coast and southern British Isles (Bicket & Tizzard, 2015; Westley & Woodman, 2020; Williams & Doyle, 2014) (Figure 10). This highlights the regional importance of this aeolian accretion model.…”

“…Subsequently, the sea‐level rise to present‐day levels has led to the flooding/reworking/marine erosion of the aeolian sands, favouring the sporadic and brief appearance of the submerged forests in the present intertidal (Vidal‐Romaní & Grandal‐d'Anglade, 2018). The erroneous interpretation of coastal sands as present‐day marine formations (Alonso & Pagés, 2010; Gómez‐Orellana et al, 2007, 2014) ignores the most logical sequence of aeolian accretion. This is the case of the 7 ky woody macrofossils found on the north coast of Galicia (Table 2), subjectively interpreted as materials removed from the seabed and moved by the waves to the intertidal (see figure 2 of Gómez‐Orellana et al, 2021), although they are represented by fossil roots and trunks in a living position (Figure 10).…”

Holocene environmental change on the Atlantic coast of NW Iberia as inferred from the Ponzos wetland sequence

“…During this time, the organic sedimentation in Moug as ceased. The Moug as deposit was the most recent site representative of a wide group of wetlands that occupied the emerged areas during the W€ urm glacial period, and whose remains are currently fossilized (G omez-Orellana 2002;G omez-Orellana et al 2007G omez-Orellana et al , 2013. Now, the new pollen and chronological data obtained establish the beginning of the Ponzos sequence between 10 950 and 8500 cal.…”

“…Only the palynological sequence of Area Longa covers the last glacial (G omez-Orellana et al 2007). A number of pollen sites record different periods of the MIS 3 (Nonn 1966;Mary et al 1977;Granja & De Groot 1996;G omez-Orellana et al 2007G omez-Orellana et al , 2013; and other groups of sites record the second half or the last third of the Holocene (Santos et al 2001;Garc ıa Anton et al 2006;Bao et al 2007;Costas et al 2009;Granja et al 2010Granja et al , 2016G omez-Orellana et al 2014;Muñoz Sobrino et al 2016;S aez et al 2018). Finally, pollen sequences recording the Lateglacial or the beginning of the Holocene are limited to the deposits of Moug as (G omez-Orellana et al 1998) and Urdaibai (Iriarte Chiapusso et al 2006).…”