Late Quaternary vegetation and coastal environmental changes at Ilha do Cardoso mangrove, southeastern Brazil

2012 ◽  
Vol 363-364 ◽  
pp. 57-68 ◽  
Author(s):  
Luiz Carlos Ruiz Pessenda ◽  
Elaine Vidotto ◽  
Paulo Eduardo De Oliveira ◽  
Antonio Alvaro Buso ◽  
Marcelo Cancela Lisboa Cohen ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Late Quaternary ◽  
Southeastern Brazil

Late Quaternary Vegetational Changes in a Marsh Forest in Southeastern Brazil with Comments on Prehistoric Human Occupation

Radiocarbon ◽  
2015 ◽  
Vol 57 (5) ◽  
pp. 737-753 ◽  
Author(s):  
Walter Mareschi Bissa ◽  
Mauro B de Toledo
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Human Impacts ◽  
Late Quaternary ◽  
Southeastern Brazil ◽  
Pollen Record ◽  
Important Indicator ◽  
Climate Conditions ◽  
Ams Radiocarbon Dating ◽  
Se Brazil

This article presents a palynological study carried out on a sediment core from a peat deposit in Serra de Botucatu, in SÃo Paulo State, southeastern Brazilian Plateau. This region has been covered by grassland vegetation and forest patches throughout the recorded period. AMS radiocarbon dating plus palynological analysis of 27 samples from the sediment core allowed the recognition of several environmental changes that took place during the last 33,000 yr recorded in the core. The relationship between sedimentation rates and changes in the abundance of plants recognized through their pollen record, particularly a few important indicator species, provided the paleoenvironmental history for the Serra de Botucatu region, allowing the identification of changes in climate conditions and comparison with other regions in Brazil. One of the most remarkable features of this record is the cold and humid conditions during the Last Glacial Maximum, which diverges from previous interpretations for southeastern and southern Brazil but is in good agreement with paleoclimatic data from trace elements from cave stalagmites in SE Brazil. No indications of human impacts on the vegetation were found in this record.

Insights into Holocene megafauna survival and extinction in southeastern Brazil from new AMS 14C dates

2011 ◽  
Vol 79 (2) ◽  
pp. 152-157 ◽  
Author(s):  
Alex Hubbe ◽  
Mark Hubbe ◽  
Ivo Karmann ◽  
Francisco W. Cruz ◽  
Walter A. Neves
Keyword(s):  
South America ◽  
Human Activities ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Southeastern Brazil ◽  
Radiocarbon Dates ◽  
Archaeological Data ◽  
Extinction Event ◽  
Ground Sloth ◽  
Ground Sloths

AbstractThe extinction of late Quaternary megafauna in South America has been extensively debated in past decades. The majority of the hypotheses explaining this phenomenon argue that the extinction was the result of human activities, environmental changes, or even synergism between the two. Although still limited, a good chronological framework is imperative to discuss the plausibility of the available hypotheses. Here we present six new direct AMS 14C radiocarbon dates from the state of São Paulo (Brazil) to further characterize the chronological distribution of extinct fauna in this part of South America. The new dates make evident that ground sloths, toxodonts, and saber-toothed cats lived in the region around the Pleistocene/Holocene transition, and in agreement with previous studies, also suggest an early Holocene survival for the ground sloth Catonyx cuvieri. Taken together with local paleoclimatic and archaeological data, the new dates do not support hunting or indirect human activities as a major cause for megafauna extinction. Although more data are required, parsimony suggests that climatic changes played a major role in this extinction event.

Change of channel pattern and construction of fluvial terraces driven by SAMS since the LGM in southeastern South America: records from Tietê River, Brazil

2021 ◽  
Author(s):  
Caio Breda ◽  
Fabiano Nascimento Pupim
Keyword(s):  
Environmental Conditions ◽  
Environmental Changes ◽  
Late Quaternary ◽  
River System ◽  
Luminescence Dating ◽  
Southeastern Brazil ◽  
Stream Power ◽  
Climatic Fluctuations ◽  
Tropical Regions ◽  
Fluvial Terraces

<p>The last 30 ka is a period marked by well-documented abrupt environmental changes on Earth. Despite the growing efforts to investigate the effects of past environmental changes in the fluvial dynamics, there is a lack of studies in intraplate tropical regions. Here, we applied geomorphological, sedimentological, and optically stimulated luminescence dating (OSL) technics to investigate the effects of environmental factors on the evolution of the Upper and Middle Tietê River during the Late Quaternary. Tietê River is one of the most important rivers of the southeast of Brazil, flowing from steepest to low-relief intraplate terrains, and under tropical climate. In order to understand the responses of the Tietê River system to environmental changes during the Late Quaternary, two main questions were tentatively answered: (i) what are the most important allogeneic factors for the evolution of this system?; (ii) how did climatic fluctuations affect river dynamics over time? We recognized a sequence of seven terraces, from 2 to 105 m above the channel, in the Middle Tietê valley. These terraces are formed by thin deposits (< 10 m), composed of sandy and conglomeratic sediments. The high and intermediate terrace levels of the Middle Tietê River are strath, while the low terraces of the middle reach are cut-and-fill. The formation of seven terrace levels in the Middle Tietê River was controlled by the combination of low erosion resistance of the lithological substrate and high stream power and coarse bedload that increase the erosion efficiency of the channels. OSL dating of sedimentary deposits in different terrace levels indicate 5 periods of aggradation in the Middle Tietê valley since the Last Glacial Maximum: 18.5 ± 2.0 ka; 9.8 ± 1.0 to 8.6 ± 0.8 ka; 7.1 ± 0.7 to 5.8 ± 0.5 ka; 4.2 ± 0.4 to 3.1 ± 0.3 ka; and 0.6 ± 0.06 ka. The results indicate that the activity of the South American Monsoon System induced the occurrence of climatic fluctuations and changes in vegetation cover in the river valleys of southeastern Brazil over the past 20 ka. The aggradation periods are correlated with more arid environmental conditions and sparser vegetation, while the incision events in the valley developed under transitions to humid environmental conditions and stimulated by vegetation recovery.</p><p><strong>Key-words: </strong>Tietê River, fluvial evolution, fluvial terraces, Quaternary geochronology.</p>

Late Pleistocene and Holocene Paleoenvironments of Chalco Lake, Central Mexico

1993 ◽  
Vol 40 (3) ◽  
pp. 332-342 ◽  
Author(s):  
Maria Socorro Lozano-Garcı́a ◽  
Beatriz Ortega-Guerrero ◽  
Margarita Caballero-Miranda ◽  
Jaime Urrutia-Fucugauchi
Keyword(s):  
Volcanic Activity ◽  
Lake Level ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Cold Climate ◽  
Central Mexico ◽  
Pollen Record ◽  
Loss On Ignition ◽  
Southeastern Part ◽  
Saline Marsh

AbstractIn order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.

scholarly journals Late Quaternary paleoenvironment of the Ross Sea continental shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 275-280 ◽  
Author(s):  
Akira Nishimura ◽  
Toru Nakasone ◽  
Chikara Hiramatsu ◽  
Manabu Tanahashi
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
Environmental Changes ◽  
Ross Sea ◽  
Late Quaternary ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Accelerator Mass Spectrometer

Based on sedimenlological and micropaleontological work on three sediment cores collected at about 167° Ε in the western Ross Sea, Antarctica, and accelerator mass spectrometer l4C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP at latest, this area was a marine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, the southernmost site (76°46'S) was covered by floating ice (shelf ice), preventing deposition of coarse terrigenous materials and maintaining a supply of diatom tests and organic carbon until 20 ka BP. The northernmost site (74°33'S) was in a marine environment with a moderate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP, a sedimentary environment similar to the present-day one has prevailed over this area.

scholarly journals Influence of Quaternary environmental changes on mole populations inferred from mitochondrial sequences and evolutionary rate estimation

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Azusa Nakamoto ◽  
Masashi Harada ◽  
Reiko Mitsuhashi ◽  
Kimiyuki Tsuchiya ◽  
Alexey P. Kryukov ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Population Expansion ◽  
Rapid Expansion ◽  
Dependent Manner ◽  
Distribution Analysis ◽  
Land Bridge ◽  
Mismatch Distribution Analysis ◽  
Expansion Event

AbstractQuaternary environmental changes fundamentally influenced the genetic diversity of temperate-zone terrestrial animals, including those in the Japanese Archipelago. The genetic diversity of present-day populations is taxon- and region-specific, but its determinants are poorly understood. Here, we analyzed cytochrome b gene (Cytb) sequences (1140 bp) of mitochondrial DNA (mtDNA) to elucidate the factors determining the genetic variation in three species of large moles: Mogera imaizumii and Mogera wogura, which occur in central and southern mainland Japan (Honshu, Shikoku, and Kyushu), and Mogera robusta, which occurs on the nearby Asian continent. Network construction with the Cytb sequences revealed 10 star-shaped clusters with apparent geographic affinity. Mismatch distribution analysis showed that modes of pairwise nucleotide differences (τ values) were grouped into five classes in terms of the level, implying the occurrence of five stages for rapid expansion. It is conceivable that severe cold periods and subsequent warm periods during the late Quaternary were responsible for the population expansion events. The first and third oldest events included island-derived haplotypes, indicative of the involvement of land bridge formation between remote islands, hence suggesting an association of the ends of the penultimate (PGM, ca. 130,000 years ago) and last (LGM, ca. 15,000 years ago) glacial maxima, respectively. Since the third event was followed by the fourth, it is plausible that the termination of the Younger Dryas and subsequent abrupt warming ca. 11,500 years ago facilitated the fourth expansion event. The second event most likely corresponded to early marine isotope stage (MIS) 3 (ca. 53,000 years ago) when the glaciation and subsequent warming period were predicted to have influenced biodiversity. Utilization of the critical times of 130,000, 53,000, 15,000, and 11,500 years ago as calibration points yielded evolutionary rates of 0.03, 0.045, 0.10 and 0.10 substitutions/site/million years, respectively, showing a time-dependent manner whose pattern was similar to that seen in small rodents reported in our previous studies. The age of the fifth expansion event was calculated to be 5800 years ago with a rate of 0.10 substitutions/site/million years ago during the mid-Holocene, suggestive of the influence of humans or other unspecified reasons, such as the Jomon marine transgression.

Grass phytoliths in surface sediments of the Sunderbans, India and their implications in reconstructing past deltaic environmental changes

The Holocene ◽  
2021 ◽  
pp. 095968362110417
Author(s):  
Madhab Naskar ◽  
Ruby Ghosh ◽  
Sayantani Das ◽  
Dipak Kumar Paruya ◽  
Binod Saradar ◽  
...  
Keyword(s):  
Surface Sediments ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Salinity Gradient ◽  
Detrended Correspondence Analysis ◽  
Mangrove Ecosystem ◽  
Sea Level Changes ◽  
Tidal Influence ◽  
Mangrove Environment ◽  
Mangrove Associate

Reliability of grass phytoliths for discriminating different deltaic sub-environments has been assessed on the modern surface sediments collected along the salinity gradient of the Sunderbans delta, India. It has been observed that grass phytolith assemblages can successfully distinguish different deltaic sub-environments especially the true mangrove zones from the mangrove associate and non-mangrove zones with minor overlaps, which further corroborated with the results of discriminant analysis (DA). Detrended correspondence analysis (DCA) and redundancy analysis (RDA) performed on the surface grass phytolith data show that salinity is the most crucial environmental parameter influencing grass phytolith distribution in the deltaic sub-environments. The potential of modern grass phytolith data in reconstructing past deltaic environmental changes has been further assessed on a late Quaternary fossil phytolith spectra from the Sunderbans spanning a sedimentary record for the last ~13.6 ka. A true mangrove environment with discernible tidal influence has been revealed between 13.6 and 3.9 ka. Absence of true mangrove–indicator grass phytoliths between ~3.9 and 2.2 ka further suggests disappearance of mangrove vegetation from this part of the Sunderbans which might have recolonized during ~2.2–0.8 ka. A mangrove associated or non-mangrove environment with little or no tidal influence came into existence in the study area since 0.8 ka onwards. A comparison with some earlier records suggests that the present grass phytolith-based palaeoenvironmental data shows conformity with the past dynamics in mangrove ecosystem in the east coast of India in respect to relative sea level changes.

Sign in / Sign up

Export Citation Format

Share Document