A multi-proxy study of Holocene environmental change recorded in alluvial deposits along the southern coast of the Pampa region, Argentina

Abstract

Analyses of fossil records of molluscs, stable isotopes of carbon and oxygen, diatoms and palynomorphs from alluvial deposits at Arroyo Claromecó, in the southern Pampa region of Argentina, provide an integrated reconstruction of rapid Holocene environmental change related to marine and palaeoclimate influences. The major events recorded include: (i) disturbances produced by marine influences in close proximity to the coast before ca. 7700 cal a BP; (ii) a short‐term decrease in salinity associated with freshwater influx between ca. 7700 and 7400 cal a BP in response to eustatic adjustment as sea level rose; (iii) an increasing input of marine water related to the Holocene sea‐level highstand and greater evaporative conditions between 7400 and 6450 cal a BP; and (iv) evaporative processes linked to a pronounced climatic variability that triggered changes in water chemistry during the last ca. 6000 cal a BP concurrently with the late Holocene sea‐level fall. A comparison of coastal and continental stable isotope records from the Pampa region reveals that evaporation and a negative precipitation/evaporation (P/E) ratio balance strongly influenced water chemistry in the coastal region, and was as important an influence as marine water during the period of maximum sea‐level highstand.

Diatomeas holocenas del delta del río Colorado, Argentina. Una aproximación paleoambiental a partir del estudio de “fragilarioides pequeñas”

“…Ambos géneros Staurosira y Pseudostaurosira han sido reconocidos ampliamente en sedimentos holocenos de Argentina, conformando ensambles salobre-dulceacuícolas en sistemas estuáricos y lacustres (Espinosa, 1994(Espinosa, , 2008Hassan et al, 2009Hassan et al, , 2011Espinosa et al, 2012;Prieto et al, 2014;Fayó et al, 2018;Guerrero et al, 2019, entre otros). Pseudostaurosira oliveraiana Grana, E. Morales, Maidana & Ector fue descripta recientemente en sedimentos holocenos de lagos salinos del noroeste de Argentina (Grana et al, 2018); el mismo año esta especie fue registrada como Psudostaurosira sp.…”

Patterns of Resource Use and Isotopic Niche Overlap Among Guanaco (Lama guanicoe), Pampas Deer (Ozotoceros bezoarticus) and Marsh Deer (Blastocerus dichotomus) in the Pampas. Ecological, Paleoenvironmental and Archaeological Implications

“…The second peak of the guanacós values overlaps with the MCA, which was a warmer and a mostly wetter phase than today, with a migration of tropical isotherms and isohyets toward the south, and where the guanaco is well represented throughout the entire archaeological record of the Pampa region. In the middle of the HTM and MCA, an intermediate period developed with a similar climate to the current one, as indicated by some authors, while others indicate the existence of periods of arid conditions, with a later shift to a more humid environment like the present one after 2.0 -1.5 ka 14 C YBP (see these climatic changes during the Holocene on a local and global scale, but with some internal differences, in Bartlein et al 2011;Bjune et al 2005;Bonadonna, Leone, and Zanchetta 1999;Cioccale 1999;Clapperton 1993;Guerra et al 2015;Iriondo 1994Iriondo , 1999Iriondo and García 1993;Iriondo, Bunetto, and Kröhling 2009;Jansen et al 2007Jansen et al , 2008Laprida et al 2014;Ledru 1993;Mancini et al 2005;Panigatti 1981;Prieto et al 2014;Teta et al 2005;Tonello and Prieto 2010;Renssen et al 2012;Soilbenzon, Medina, and Abba 2013;Stutz et al 2012;Waldmann et al 2010). During the warm and wet periods of the HTM and the MCA, C 4 species of the NADP-ME biochemical type, especially those in the Panicoideae and Aristidoideae subfamilies which are now broadly represented in the Pampa Ondulada, must also have been widely distributed in the coverage during both phases, as they found suitable parameters in wet and hot environments.…”

Reconstrucción Paleoambiental de la Planicie Costera de Mar Chiquita (Provincia de Buenos Aires, Argentina) Durante el Holoceno, Basada en Diatomeas

“…También fueron citadas en la sucesión sedimentaria de Arroyo Las Brusquitas a los c. 2040 14 C años AP (Vilanova et al, 2006) y son muy comunes en depósitos cuaternarios de ambientes lacustres de Patagonia y Tierra del Fuego (Espinosa, 2008). Staurosira venter fue registrada en lapsos más amplios: en La Ballenera entre 6790 y 6120 años 14 C AP (Espinosa et al, 2003) y en Claromecó entre 6540-6000 14 C años AP (Prieto et al, 2014).…”