A NEW CONTRIBUTION TO UNDERSTANDING LATE HOLOCENE ENVIRONMENTAL DYNAMICS IN THE SOUTHEASTERN PAMPA PLAIN, ARGENTINA: A MULTI-INDICATOR ANALYSIS OF LAGUNA LAS MOSTAZAS

STUTZ, SILVINA MARÍA; HASSAN, GABRIELA S.; DE FRANCESCO, CLAUDIO G.; SANCHEZ VUICHARD, GUILLERMINA; TONELLO, MARCELA SANDRA

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2024

0002-7014

A multi-indicator analysis, including diatoms, mollusks, pollen, and non pollen palynomorphs (NNPs), was performed to reconstruct Las Mostazas lake environmental history during the Late Holocene to provide detailed paleoenvironmental new data for the southeastern Pampa plain. The record indicates the presence of a lake since ca. 3400 cal. yr BP to the present. At the record’s base, ca. 3400 and 3200–3100 cal. yr BP and under a regional dry environment, a shallow, clear and brackish environment, subjected to intermittent/ephemeral regimes intercalated with episodes of total desiccation was developed. The lake evolved into a fresh and brackish shallow lake towards ca. 2200 cal. yr BP, in which most indicators suggest shallowness conditions but a brief moment of higher water-lake level at ca. 2200–2000 cal. yr BP is detected and turbidity begins to increase. Freshwater conditions installed ca. 1700–1600 cal. yr BP in a deeper and turbid lake. Periods ofintense rainfall, that would have started at ca. 2000 cal. yr BP, and intensified at ca. 1500–1200 cal yr BP, may have promoted high water-lake levels and the input of organic matter into the lake. In the last ca. 600 cal. yr BP lake became configured like modern one. During the last ca. 80years (1930–2009 CE), a process of accelerated eutrophication has been registered in the lake. In general terms, the evolution of the Las Mostazas Lake agrees with the model proposed for other lakes of the southeastern Pampa plain.