Landscape evolution in Western Amazonia: palynostratigraphy, palaeoenvironments and diversity of the miocence Solimões formation, Brazil

During the Miocene (23.03 to 5.33 Ma), western Amazonia experienced major changes in its geography and biodiversity as a response to Andean uplift. To better understand these changes, the palynology of the Solimões Formation (NW Brazil) is presented with the objective of providing age control, and establishing palaeoenvironments and pollen richness within the framework of geological and climatic events. The ninety-five palynological samples yield 491 palynomorphs, of which 76 pollen and 25 spores are new. Correlation with a nearby calibrated biozonation resulted in ages from 18.7 to 10.7 Ma (late early to earliest-late Miocene). The pollen associations are typical of Amazonian humid forests, with abundant palms, Bombacoideae, trees and grasses, and lack diverse and abundant herbs or dry forest indicators. Spikes in algae and dinoflagellates show phases of lake development and two marine incursions – one between 18.4 and 17.8 Ma, and another between 14.1 and 13.7 Ma. Statistical analyses of the data show inundations had no effect in the vegetation composition. Estimates of diversity using different metrics clearly show a diversity increase and community change at ca. 16 Ma, independent of lithofacies. This change is driven by the Middle Miocene Climatic Optimum and not correlated with any of the marine incursions. Altogether, the results bring more detail to the environmental history of western Amazonia, establishing two inundation events and furthering the climate diversification relationship in Neotropical biomes into the Miocene period

Lagoa da Pata revisitada: maior sazonalidade como causa do reagrupamento da comunidade vegetal durante o último período glacial na Amazônia

Pollen in sediments of Lake Pata, northwestern Amazon, was studied with the aim of covering the entire last glacial cycle. Although a tall tropical forest seems to have remained unbroken throughout the past ~120,000 years, reanalyses and reinterpretation of data suggest the so-called nonanalog ice age vegetation was more seasonal, resembling present day seasonal tropical dry forests. This agrees with a prolonged annual dry season and polar air advection as the features setting the region biome. The very local paleoenvironmental interpretation cannot be perfectly extended to a broader lowland region because like presently, orographic rain caused the hill to have remained moister and less susceptible to drought, unlike the overall mesic lowland forests of the upper Rio Negro basin. Thus the dry events affected the region more drastically than what could have been assessed by means of a pollen study at the hill. Seasonally dry and moderately cooler is the most probable climatic picture for the region during the last ice agePólen em sedimentos da Lagoa da Pata, noroeste da Amazônia, foi estudado com o intuito de cobrir o último ciclo glacial. Embora uma floresta tropical alta pareça ter remanescido intocada durante os últimos ~120,000 anos, a re-análise e reinterpretação de dados sugerem que a vegetação não análoga da idade do gelo na Amazônia foi mais sazonal, assemelhando-se às florestas tropicas sazonalmente secas. O resfriamento teve papel importante em permitir a expansão local de elementos montanos, que é o ponto chave para estabelecer uma vegetação sem análogos modernos. A interpretação paleoambiental estritamente local não pode ser extendida a uma região mais ampla da planície, pois, como presentemente, chuvas orográficas fizeram com que o morro onde o lago está localizado permanecesse mais úmido e menos suscetível a seca, ao contrário das florestas na planície da alta bacia do rio Negro. Seco e moderadamente mais frio é o mais provável cenário climático para a região durante picos do último glacial

Palynological constraints on the provenance and stratigraphic range of a Lopingian (Late Permian) inter-extinction floral lagerstätte from the Xuanwei Formation, Guizhou Province, China

Late Permian (Lopingian) volcanoclastic lithologies from the Huopu Mine near Fuyuan, Guzihou Province, SW China have yielded konservat lagerstatte-grade plant macrofossils. These fossils derive from a stratigraphic interval bounded by the mid-Capitanian extinction below and the end Permian extinction above and globally, few anatomically preserved floras are known from this age. Due to practical constraints of active mining at the site, to date this konservat lagerstatte is only known from ex situ mine spoil. However, through the use of combined petrographic and palynologic analyses it has been possible to constrain the stratigraphic position, provenance and taphonomic history of these fossils, such that they are now known to have been deposited in in a shallow marine setting as part of the lower member of the Xuanwei Formation during the Wuchiapingian. The palynological assemblage is of low abundance and diversity and is dominated by fern spores with less common lycopsid and sphenopsid spores and gymnosperm pollen, and rare marine acritarchs and is suggestive of an ecologically pioneering rather than established flora. Given the Wuchiapingian age of the lagerstatte this flora has broader potential significance in that affords insights into pre-adaption and resilience to the profound environmental perturbations associated with the mid-Capitanian and end-Permian extinctions, which were key to long term survival into the Triassic. (C) 2016 Elsevier B.V. All rights reserved

The movement of pre-adapted cool taxa in north-central Amazonia during the last glacial

The effects of climate change on the lowland vegetation of Amazonia during the last glacial cycle are partially known for the middle and late Pleniglacial intervals (late MIS 3, 59–24 ka and MIS 2, 24–11 ka), but are still unclear for older stages of the last glacial and during the last interglacial. It is known that a more seasonal dry-wet climate caused marginal forest retraction and together with cooling rearranged forest composition to some extent. This is observed in pollen records across Amazonia depicting presence of taxa at glacial times in localities where they do not live presently. The understanding of taxa migration is hindered by the lack of continuous interglacial-glacial lowland records. We present new data from a known locality in NW Amazonia (Six Lakes Hill), showing a vegetation record that probably started during MIS 5 (130–71 ka) and lasted until the onset of the Holocene. The vegetation record unravels a novel pattern in tree taxa migration: (1) from the beginning of this cycle Podocarpus and Myrsine are recorded and (2) only later do Hedyosmum and Alnus appear. The latter group is largely restricted to montane biomes or more distant locations outside Amazonia, whereas the first is found in lowlands close to the study site on sandy soils. These findings imply that Podocarpus and Myrsine responded to environmental changes equally and this reflects their concomitant niche use in NW Amazonia. Temperature drop is not discarded as a trigger of internal forest composition change, but its effects are clearer later in the Pleniglacial rather than the Early Glacial. Therefore early climatic/environmental changes had a first order effect on vegetation that invoke alternative explanations. We claim last glacial climate-induced modifications on forest composition favoured the expansion of geomorphologic-soil related processes that initiated forest rearrangement. © 2017 Elsevier Lt

Results confirm a relatively dry setting during the last glacial (MIS 3 and LGM) in Carajás, Amazonia: A comment on Guimarães et al.

Recent pollen rain data from lake Amendoim in Carajás (southeastern Amazonia) revealed a dominant forest formation spectrum where, locally, montane savannas occupy a larger proportion of the lake’s basin (>90%). From this surprising result, we learn that local savanna coverage may not necessarily be enough to influence and dominate the pollen spectrum recorded in the lake sediments when rainforest is widespread in the surrounding areas. Therefore, even a minor proportion of tall forest in a savanna environment can have a significant influence on pollen deposition, masking the savanna signal in the stratigraphic record. Thus, when interpreting the last glacial pollen record of Carajás, the increased abundance of savanna taxa is an unequivocal indicator of local to regional savannas expansion. The postulation of a continued rainforest formation during the glacial times is an unsustainable alternative. © 2017, © The Author(s) 2017

The Hill of Six Lakes revisited: New data and re-evaluation of a key Pleistocene Amazon site

The new analyses of a sedimentary record of Lake Pata in the Hill of Six Lakes, in NW Amazon and its correlation with other Quaternary proxy records in the region provide new insights regarding the vegetation and climate of the lowland forest during the Last Glacial. Despite what has been reported previously in the literature, the sedimentary and pollen records are not continuous. The hill remained forested; however, clear signals of structural change are seen in the record, which indicate that the area experienced a significantly drier climate during the Last Glacial Maximum (LGM). The herbs and taxa that are known to be more dominant in seasonally dry forests were all more abundant during the glacial part of the record, and the cool-adapted elements were mixed with warm lowland elements, which indicates a temperature depression. A comparison of the palaeoecological data with other regional geoenvironmental records of the Upper Negro River basin and other areas of the Amazon provides additional support for a cooler and more seasonal environment during the middle Pleniglacial, which then became drier during the LGM. A "wet" LGM is strongly refuted; therefore, the palaeoclimatic and ecological models that used the previous proxy data from Six Lakes to sustain "wet" conditions and a "continuous forest record" during the LGM to reconstruct the palaeoenvironmental conditions in the Amazon should be reviewed. © 2013 Elsevier Ltd

Neogene paleoecology and biogeography of a Malvoid pollen in northwestern South America

Western Amazonian landscapes evolved dynamically during the Neogene. Large wetlands developed responding to Andean uplift what promoted the rise and diversification of many plant groups. One such group is the well-documented Malvoid pollen Malvacipolloides maristellae from the Miocene of northwestern South America. In the present contribution, we compared the botanical affinity among fossil and extant Malvoid, reconstructed past distributions of the taxa and their relative abundance throughout the Neogene-Quaternary, and interpreted the biogeographical and paleoecology of the group. We found similar pollen morphologies among the fossil and 14 extant Malvoids, mainly Allosidastrum, Sphaeralcea, Monteiroa, Malvella, and Wissadula. These belong to the Malveae tribe (subtribes Abutilinae and Malvinae), which are extra-Amazonian, mostly found in drier-colder settings, in full light environments (savannahs, forest edges), and tolerating varied oligotrophic and hydric stress soils. We recorded widespread Miocene populations of the fossil, from western Amazonia to coastal Venezuela, with high abundances in the early Miocene, when the group first appeared, then dropped significantly from the late Miocene onwards. The gradual demise of M. maristellae is attributed to the negative effects of brackish water inundations and the gradual increase of humidity and forest cover following the decline of wetlands that narrowed the open, light-demanding ecological niche exploited by M. maristellae. In the Pliocene-Quaternary, no records were found in western Amazonia, attesting to its final displacement outside the forest structure. In its northern extension (Venezuela and Colombia), the fossil survived for longer due to available open-dry environments that developed in the latest Neogene. © 2019 Elsevier B.V

Fossil pollen of Parkia R.Br. (Fabaceae) pollen from the Miocene of western Amazonia

Table S1. Raw measurements and morphological traits of fossil Parkiidites (P. marileae Leite et al. 2021 and P. microreticulatus Guinet et Salard-Cheboldaeff 1975) and of extant species of Parkia. Figure S1. Boxplots showing the main morphological characters from extant Parkia species, compared to the same characters from two fossils (Parkiidites marileae Leite et al. 2021; and Parkiidites microreticulatus Guinet et Salard-Cheboldaeff 1975). For detailed data see Table S1. Figure S2. Species distribution modelling for extant species of Parkia assigned as nearest living relative (NLR) of Parkiidites marileae Leite et al. 2021. Color legend is probability of occurrence. Outline of the Amazon biome based on WWF Ecoregions (Olson et al. 2001). Figure S3. Species distribution modelling for extant species of Parkia that do not belong to the NLR (nearest living relative) of Parkiidites marileae Leite et al. 2021. Color legend is probability of occurrence. Outline of the Amazon biome based on WWF Ecoregions (Olson et al. 2001). </p

Data from: Miocene flooding events of western Amazonia

There is a considerable controversy about whether western Amazonia was ever covered by marine waters during the Miocene [23 to 5 Ma (million years ago)]. We investigated the possible occurrence of Miocene marine incursions in the Llanos and Amazonas/Solimões basins, using sedimentological and palynological data from two sediment cores taken in eastern Colombia and northwestern Brazil together with seismic information. We observed two distinct marine intervals in the Llanos Basin, an early Miocene that lasted ~0.9 My (million years) (18.1 to 17.2 Ma) and a middle Miocene that lasted ~3.7 My (16.1 to 12.4 Ma). These two marine intervals are also seen in Amazonas/Solimões Basin (northwestern Amazonia) but were much shorter in duration, ~0.2 My (18.0 to 17.8 Ma) and ~0.4 My (14.1 to 13.7 Ma), respectively. Our results indicate that shallow marine waters covered the region at least twice during the Miocene, but the events were short-lived, rather than a continuous full-marine occupancy of Amazonian landscape over millions of years

Miocene flooding events of western Amazonia

There is a considerable controversy about whether western Amazonia was ever covered by marine waters during the Miocene [23 to 5 Ma (million years ago)]. We investigated the possible occurrence of Miocene marine incursions in the Llanos and Amazonas/Solimões basins, using sedimentological and palynological data from two sediment cores taken in eastern Colombia and northwestern Brazil together with seismic information. We observed two distinct marine intervals in the Llanos Basin, an early Miocene that lasted ~0.9 My (million years) (18.1 to 17.2 Ma) and a middle Miocene that lasted ~3.7 My (16.1 to 12.4 Ma). These two marine intervals are also seen in Amazonas/Solimões Basin (northwestern Amazonia) but were much shorter in duration, ~0.2 My (18.0 to 17.8 Ma) and ~0.4 My (14.1 to 13.7 Ma), respectively. Our results indicate that shallow marine waters covered the region at least twice during the Miocene, but the events were short-lived, rather than a continuous full-marine occupancy of Amazonian landscape over millions of years