Abstract. We use a standardized template for Pleistocene sea-level data to review last interglacial (Marine Isotope Stage 5 – MIS 5) sea-level indicators along the coasts of the western Atlantic and southwestern Caribbean, on a transect spanning from Brazil to Honduras and including the islands of Aruba, Bonaire, and Curaçao. We identified six main types of sea-level indicators (beach deposits, coral reef terraces, lagoonal deposits, marine terraces, Ophiomorpha burrows, and tidal notches) and produced 55 standardized data points, each constrained by one or more geochronological methods. Sea-level indicators are well preserved along the Brazilian coasts, providing an almost continuous north-to-south transect. However, this continuity disappears north of the Rio Grande do Norte Brazilian state. According to the sea-level index points (discrete past position of relative sea level in space and time) the paleo sea-level values range from ∼ 5.6 to 20 m above sea level (a.s.l.) in the continental sector and from ∼ 2 to 10 m a.s.l. in the Caribbean islands. In this paper, we address the uncertainties surrounding these values. From our review, we identify that the coasts of northern Brazil, French Guiana, Suriname, Guyana, and Venezuela would benefit from a renewed study of Pleistocene sea-level indicators, as it was not possible to identify sea-level index points for the last interglacial coastal outcrops of these countries. Future research must also be directed at improving the chronological control at several locations, and several sites would benefit from the re-measurement of sea-level index points using more accurate elevation measurement techniques. The database compiled in this study is available in spreadsheet format at the following link: https://doi.org/10.5281/zenodo.5516444 (Version 1.02; Rubio-Sandoval et al., 2021).
Abstract. In this paper, we use a standardized template for Pleistocene sea-level data to review last interglacial (MIS 5) sea-level indicators along the coasts of the Western Atlantic and Southwestern Caribbean, on a transect spanning from Brazil to Honduras, and including the islands of Aruba, Bonaire, and Curaçao. Our review produced 55 standardized datapoints, each assigned to one or more geochronological constraints. Sea-level index points are well preserved along the Brazilian coasts, providing an almost continuous north-to-south transect. Despite this and the variety of relative sea-level indicators (i.e. beach deposits, coral reef terraces, marine terraces, Ophiomorpha burrows, and tidal notches) our data compilation highlights several concerns related to age control and the accuracy of elevation measurements. We identify that the coasts of Northern Brazil, French Guyana, Suriname, Guyana, and Venezuela would benefit from a renewed study of Pleistocene sea-level indicators, as it was not possible to identify sea-level index for the last interglacial coastal outcrops along the coasts of these countries. Future research must also be directed at improving the chronological control at several locations, and several sites would benefit from re-measurement of sea-level index points using more accurate elevation measurement techniques. Our database contribution represents a starting point to detail the last interglacial sea-level history in this area. The database is available at the following link: https://zenodo.org/record/4727850 (Version 1.01; Rubio-Sandoval et al., 2021).
Lake Tzibaná is one of the largest (1.27 km2) and deepest (Zmax = 52 m) karstic lakes in the UNESCO’s Biosphere Reserve “Nahá-Metzabok” and in the Lacandon Forest, southeastern Mexico. It archives sediments from multiple sources and the inflowing Nahá River forms deltaic deposits. In 2019, the water level in Lake Tzibaná declined by ~ 15 m, persisting for 4 months and exposing the Nahá River Delta. A geophysical profile on the exposed delta revealed an accumulation of ~ 20 m of such deposits. Three sediment outcrops from an inactive channel in the Nahá River Delta, which ranged in height from 0.6 to 1.43 m, were sampled and a multi-proxy analysis of biological remains and geochemical variables was conducted. Four facies were observed: (1) massive-coarse sand, (2) fine sand, (3) dark leaf litter and (4) massive silty clay, each characterized by specific microcrustacean, testate amoebae and diatom taxa. Six dark leaf litter horizons were radiocarbon dated and revealed a complex depositional history including inverted ages making the establishment of an age model difficult. Nevertheless, past lake-level changes and the formation of the four facies match three characteristic water-level stages, which can also be observed on recent satellite images: (1) Massive-coarse sand deposits, with compositional and sedimentological characteristics of a shoreline environment and fluvial lateral banks, were formed during large-magnitude reductions in the lake level, similar to the one in 2019, (2) Interbedded layers of fine sand and dark leaf litter, currently found in low-energy fluvial environments, were formed during shorter and less pronounced decrease intervals, and (3) Massive silty clay, with distinctive microorganisms from low-energy lacustrine environments, is deposited during high water-level stages, when the delta is covered by water. Our findings illustrate how hydrological changes alter sedimentary dynamics in deltaic areas of lakes. Despite the complexity of their depositional processes, deltaic records can serve as a complementary source of paleolimnological information to records from distal zones due to their sensitivity to variations in water level, especially during extreme and prolonged desiccation events. Future research should attempt to combine evidences from deltaic and sediment sequences from deeper zones of Lake Tzibaná to reconstruct water-level variations during the entire Holocene. Understanding past lake-level reductions is not only relevant for the local indigenous communities but also crucial for the conservation of this ecosystem of international importance.
en las plataformas interna y externa debido a la estrecha plataforma continental. Los muestreos de zooplancton se efectuaron con 2 redes cónicas de apertura de malla de 333 y 505 µm en 33 estaciones de muestreo. En el laboratorio se estimó la biomasa de zooplancton en peso húmedo y se separaron e identificaron los moluscos holoplanctónicos. Los valores de biomasa registrados (0.02 a 7.51 g 100 m -3 ) son típicos de las aguas oligotróficas del Caribe. Se identificaron 8 especies de moluscos, que en orden decreciente de abundancia son: Creseis acicula, Heliconoides inflatus, Atlanta lesueurii, Diacavolinia longirostris, Limacina trochiformis, Limacina lesueurii, Firoloida desmarestia y Limacina bulimoides. Los resultados de la prueba estadística Anosim mostraron que no hubo diferencias en la distribución de la fauna entre las plataformas interna y externa, probablemente debido a la fuerte influencia de aguas oceánicas sobre las neríticas. La información aquí proporcionada es de gran importancia en la generación de eventuales planes de conservación de la biota pelágica de la reserva.
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