Paleoenvironmental interpretation of the mid‐late Holocene of Corrientes province, Argentina

Abstract

The objective of the present paper is to recognize and reconstruct, from the analysis of pollen recovered from sedimentary cores, the predominant plant communities and their variations during the Holocene in Corrientes Argentina, in order to infer changes in climatic conditions, vegetation and paleoenvironmental evolution in the northeast of Argentina. For this study, lakes located in the central region of Corrientes province were selected, comprising part of the western margin of the Iberá Wetland. The palynological analysis of the paleocommunities shows, in a first stage of the mid Holocene, the predominance of marsh grasslands and hygrophilous communities that indicates humid to sub‐humid environmental conditions. In a later stage of the mid Holocene, the paleocommunities show a characteristic association of wetlands, which together with the presence of Typha sp., would indicate sub‐humid to humid conditions and waterlogged or flooded soils with slow‐moving water. For the late Holocene, the paleocommunities show, initially, the presence of a grass‐dominated herbaceous steppe, indicating environmental disturbances, which in the fossil record could reflect the combination of intense wind action under a dry climate. In a later stage, the frequency and variety of species characteristic of humid environments increase, dominated by marshy‐herbaceous species, in addition to the development of the hygrophilous forest. Consequently, since the mid Holocene, the main climate factors responsible for the observed changes in wetland conditions were the location and intensity of the Atlantic and Pacific anticyclones in addition to changes in sea level. These forces mainly affected the distribution of precipitation, causing significant changes in the vegetation communities.

Pollen and spores morphology from the Holocene of the Iberá Wetlands in northeastern Argentina

“…Local taxa refer to those species that are part of the natural vegetation of the Iberá Wetlands (Arbo & Tressens, 2002) whereas the extra-local taxa are those that do not belong to the Iberá. The latter species found in low percentages in the Tilia diagrams of the lakes analyzed by Fernandez Pacella et al (2011) andLara (2019). They achieved to depocenters by means of wind currents coming from farther regional vegetation of N, NW and W of Corrientes and E of Chaco (Carnevali, 1994;Fontana, 2018).…”

“…The taxonomic analysis of pollen grains and spores presented in this contribution is a new study derived from previous studies carried out by Fernandez Pacella et al (2011), Fernandez Pacella (2013) and Fernandez Pacella & Lara (2019 in which paleoenvironmental interpretations based on main palynologic groups addressed. These works included the study of core samples obtained with a Livingston-type sampler from six lakes in their central and deepest parts on the western margin of the Iberá Wetlands.…”

“…Terminology used for descriptions of pollen grains and spores is based on Kremp (1965), Nilson & Praglowski (1992), Punt et al (2007), andSáenz Laín (2004). The reference collection PAL-CTES of the UNNE and specialized literature were used to identify pollen grains and spores (Acevedo & Anzótegui, 1998;Anzótegui & Ferrucci, 1998;Anzótegui, 2001;Anzótegui & Caccavari, 2001;Anzótegui & Mautino, 2001a, b;Bhattacharya et al, 2009;Caccavari & Dome, 2001Cuadrado, 1998a, b, c;Fernandez Pacella & Canteros, 2014;Fernandez Pacella et al, 2014a, b;Fuertes & Rodríguez, 2009;Garralla & Cuadrado, 2001;Markgraf & D`Antoni, 1978;Pire et al, 2006).…”

“…Palynomorphs were identified in lacustrine sediments of northwestern of the Iberá Wetlands (Fernandez Pacella et al, 2011, 2013Fernandez Pacella & Lara, 2019) which represented mostly marsh-herbaceous vegetation under humid condition between 5968-5000 years cal BP. In agreement with Iriondo (1994), drier conditions were determined from 5000 to 3506 years cal BP with a decrease in the species frequency typical of wet environments and increase of xero-halophyte vegetation.…”

“…Pore 1-4 μm diameter with a ring 1 to 6 μm thick. Exine 1-3 μm thick, tectate, psilate to scabrate (Fernandez Pacella & Canteros, 2014).…”