Grass development in the Amazon drainage basin, evidence from the fossil and phytochemical record

2020 ◽  
Author(s):  
Carina Hoorn ◽  
Judith Kirschner ◽  
Maxine Beer ◽  
Caixia Wei ◽  
Tyler Kukla ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Electron Microscopy Analysis ◽  
Heated Debate ◽  
Neogene Sediments ◽  
History Of ◽  
Andean Uplift ◽  
Staged Model ◽  
Land Surfaces ◽  
Glacial Periods ◽  
Fluvial Environments

<p>The Poaceae (the grass family) includes over 11000 species and covers large part of the Earth land surfaces. Their history is rooted in the Cretaceous, but this group only expanded fully over the globe during the late Miocene. In the Amazon drainage basin (ADB) grasses were at the core of a heated debate, in which it was hypothesized that during the Pleistocene glacial periods grasses replaced vast extents of the Amazon rainforest. Although this hypothesis is now rejected, the history of grasses in the ADB still remains to be resolved. In this paper we propose a 3-staged model for grass development in the ADB: (1) from c. 23 to 9 Ma western Amazonia was dominated by a megawetland (the ‘Pebas system’) that harboured large amounts of (aquatic?) grasses; (2) from c. 9 Ma Andean uplift prompted megafan and fluvial environments on the Andean slopes and in the Amazon lowlands respectively, these environments created new settings for grass colonization; (3) from c. 5 Ma grasses were firmly established in the tropical alpine vegetation (páramo), the tropical lowland floodplains (várzeas), and savannas (cerrado). To test these scenarios we analysed Neogene and extant Andes-Amazonian grasses by means of Fourier Transform Infrared spectroscopy, we performed a Light- and Scanning Electron Microscopy analysis, and compared the results with existing biomarker data from the Neogene sediments. Here we report on the preliminary results that, among others, suggest that in the middle Miocene aquatic (C3) taxa were comon in the Amazon lowlands. Although further study will have to confirm the precise nature of the ADB grass history, we anticipate that abiotic processes during the Neogene and Quaternary left a strong imprint in the grass phytogeography of northern South America.</p><p> </p>

scholarly journals Landscape dynamics promoted the evolution of mega-diversity in South American freshwater fishes

2021 ◽  
Author(s):  
Fernanda Cassemiro ◽  
James S Albert ◽  
Alexandre Antonelli ◽  
Andre Menegotto ◽  
Rafael O Wuest ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Freshwater Fishes ◽  
Landscape Dynamics ◽  
South American ◽  
Serra Do Mar ◽  
History Of ◽  
Andean Uplift ◽  
Abrupt Shifts ◽  
Lineage Diversification

Landscape dynamics and river network rearrangements are widely thought to shape the diversity of Neotropical freshwater fishes, the most species-rich continental vertebrate fauna on Earth. Yet the effects of hydrogeographic changes on fish dispersal and diversification remain poorly understood. Here we integrate an unprecedented occurrence dataset of 4,967 South American freshwater fish species with a species-dense phylogeny to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Three abrupt shifts in diversification rates occurred during the Paleogene (between 63 and 23 Ma) in association with major landscape evolution events, and net diversification accelerated from the Miocene to the Recent (c. 20 - 0 Ma). The Western Amazon exhibited the highest rates of in situ diversification and was also the most important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including Early Miocene (c. 20 Ma) uplift of the Serra do Mar, and Late Miocene (c. 10 Ma) uplift of the Northern Andes and formation of the modern transcontinental Amazon River. Reciprocal mass dispersal of fishes between the Western and Eastern Amazon coincided with this phase of Andean uplift. The Western Amazon has the highest contemporary levels of species richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics were constrained by the history of drainage basin connections, strongly affecting the assembly and diversification of basin-wide fish faunas.

Evolution of the Paran drainage basin and its relation to the Plio-Pleistocene history of the Arava Rift western margin, Israel

2000 ◽  
Vol 49 (4) ◽  
pp. 215-238 ◽  
Author(s):  
Hanan Ginat ◽  
Yoav Avni ◽  
Zvi Garfunkel ◽  
Hanan Ginata ◽  
Yosef Bartov
Keyword(s):  
Drainage Basin ◽  
Western Margin ◽  
History Of

scholarly journals Erosion assessment in the middle Kali Gandaki (Nepal): A sediment budget approach

2013 ◽  
Vol 46 ◽  
Author(s):  
Monique Fort ◽  
Etienne Cossart
Keyword(s):  
Drainage Basin ◽  
Sediment Budget ◽  
Mountain Range ◽  
Primary Concern ◽  
Stream Power ◽  
Sediment Budgets ◽  
Relative Chronology ◽  
Wide Range ◽  
History Of

Active mountains supply the largest sediment fluxes experienced on earth. At mountain range scale, remote sensing approaches, sediments provenance or stream power law analyses, collectively provide rough long-term estimates of total erosion. Erosion is indeed controlled by rock uplift and climate, hence by a wide range of processes (detachment, transport and deposition), all operating within drainage basin units, yet with time and spatial patterns that are quite complex at local scale. We focus on the Kali Gandaki valley, along the gorge section across the Higher Himalaya (e.g. from Kagbeni down to Tatopani). Along this reach, we identify sediment sources, stores and sinks, and consider hillslope int eractions with valley floor, in particular valley damming at short and longer time scales, and their impact on sediment budgets and fluxes. A detailed sediment budget is presented, constrained by available dates and/or relative chronology, ranging from several 10 kyr to a few decades. Obtained results span over two orders of magnitude that can best be explained by the type and magnitude of erosional processes involved. We show that if large landslides contribute significantly to the denudation history of active mountain range, more frequent medium to small scales landslides are in fact of primary concern for Himalayan population.

scholarly journals The Finnish Comprehensive School

2019 ◽  
pp. 122-142
Author(s):  
Jaakko Kauko
Keyword(s):  
International Student ◽  
Comprehensive School ◽  
The Political ◽  
Policy Success ◽  
Political Debates ◽  
Path Dependencies ◽  
Complex Development ◽  
Heated Debate ◽  
History Of ◽  
Complexity Theories

For a decade, Finnish education, claimed to be among the best in the world, has basked in international glory. This reputation is largely due to the country’s success in the Programme for International Student Achievement (PISA), run by the OECD. The aim of this chapter is to critically examine this purported policy success of the Finnish comprehensive school from the perspective of complexity theories. By drawing on different research and statistical data, the chapter critically analyses the extent to which the Finnish comprehensive school can be seen as a success story in terms of performance. Using the well-reported history of the comprehensive school, it teases out the milestones of its development, while pointing to contingencies and path dependencies along the way, which have led to its legitimate position. It also reviews scholarly accounts in contrast to the political debates. Finally, the chapter sums up the complex development of comprehensive education and discusses the question under heated debate: what, if anything, can we learn from it?

A Brief History of the Discovery of Amelogenin Nanoribbons In Vitro and In Vivo

2021 ◽  
pp. 002203452110434
Author(s):  
Y. Bai ◽  
J. Bonde ◽  
K.M.M. Carneiro ◽  
Y. Zhang ◽  
W. Li ◽  
...  
Keyword(s):  
Recombinant Proteins ◽  
Protein Structures ◽  
Historical Review ◽  
Limited Information ◽  
Transmission Electron Microscopy Analysis ◽  
Electron Microscopy Analysis ◽  
History Of ◽  
The 1960S

Without evidence for an organic framework, biological and biochemical processes observed during amelogenesis provided limited information on how extracellular matrix proteins control the development of the complex fibrous architecture of human enamel. Over a decade ago, amelogenin nanoribbons were first observed from recombinant proteins during in vitro mineralization experiments in our laboratory. In enamel from mice lacking the enzyme kallikrein 4 (KLK4), we later uncovered ribbon-like protein structures that matched the morphology, width, and thickness of the nanoribbons assembled by recombinant proteins. Interestingly, similar structures had already been described since the 1960s, when enamel sections from various mammals were demineralized and stained for transmission electron microscopy analysis. However, at that time, researchers were not aware of the ability of amelogenin to form nanoribbons and instead associated the filamentous nanostructures with possible imprints of mineral ribbons in the gel-like matrix of developing enamel. Further evidence for the significance of amelogenin nanoribbons for enamel development was stipulated when recent mineralization experiments succeeded in templating and orienting the growth of apatite ribbons along the protein nanoribbon framework. This article provides a brief historical review of the discovery of amelogenin nanoribbons in our laboratory in the context of reports by others on similar structures in the developing enamel matrix.

scholarly journals Mnemonic Populism: The Polish Holocaust Law and its Afterlife

2020 ◽  
pp. 1-13 ◽  
Author(s):  
Kornelia Kończal
Keyword(s):  
Significant Other ◽  
The Past ◽  
Cultural Foundations ◽  
The Holocaust ◽  
Heated Debate ◽  
History Of ◽  
The Law ◽  
The Relationship

In early 2018, the Polish parliament adopted controversial legislation criminalising assertions regarding the complicity of the ‘Polish Nation’ and the ‘Polish State’ in the Holocaust. The so-called Polish Holocaust Law provoked not only a heated debate in Poland, but also serious international tensions. As a result, it was amended only five months after its adoption. The reason why it is worth taking a closer look at the socio-cultural foundations and political functions of the short-lived legislation is twofold. Empirically, the short history of the Law reveals a great deal about the long-term role of Jews in the Polish collective memory as an unmatched Significant Other. Conceptually, the short life of the Law, along with its afterlife, helps capture poll-driven, manifestly moralistic and anti-pluralist imaginings of the past, which I refer to as ‘mnemonic populism’. By exploring the relationship between popular and political images of the past in contemporary Poland, this article argues for joining memory and populism studies in order to better understand what can happen to history in illiberal surroundings.

scholarly journals Neogene precipitation, vegetation, and elevation history of the Central Andean Plateau

2020 ◽  
Vol 6 (35) ◽  
pp. eaaz4724 ◽  
Author(s):  
C. Martínez ◽  
C. Jaramillo ◽  
A. Correa-Metrío ◽  
W. Crepet ◽  
J. E. Moreno ◽  
...  
Keyword(s):  
Fossil Record ◽  
Climate Model ◽  
Regional Climate ◽  
High Elevation ◽  
The Andes ◽  
Plant Fossil ◽  
History Of ◽  
Andean Uplift ◽  
Climate Model Simulations ◽  
Fossil Data

Andean uplift played a fundamental role in shaping South American climate and species distribution, but the relationship between the rise of the Andes, plant composition, and local climatic evolution is poorly known. We investigated the fossil record (pollen, leaves, and wood) from the Neogene of the Central Andean Plateau and documented the earliest evidence of a puna-like ecosystem in the Pliocene and a montane ecosystem without modern analogs in the Miocene. In contrast to regional climate model simulations, our climate inferences based on fossil data suggest wetter than modern precipitation conditions during the Pliocene, when the area was near modern elevations, and even wetter conditions during the Miocene, when the cordillera was around ~1700 meters above sea level. Our empirical data highlight the importance of the plant fossil record in studying past, present, and future climates and underscore the dynamic nature of high elevation ecosystems.

scholarly journals River profile response to normal fault growth and linkage: An example from the Hellenic forearc of south-central Crete, Greece

2016 ◽  
Author(s):  
Sean F. Gallen ◽  
Karl W. Wegmann
Keyword(s):  
Drainage Basin ◽  
Profile Analysis ◽  
Normal Fault ◽  
Drainage Area ◽  
Fault System ◽  
Stream Power ◽  
River Incision ◽  
South Central ◽  
History Of ◽  
Fault Growth

Abstract. Topography is a reflection of the tectonic and geodynamic processes that act to uplift the Earth's surface and the erosional processes that work to return it to base level. Numerous studies have shown that topography is a sensitive recorder or tectonic signals. A quasi-physical understanding of the relationship between river incision and rock uplift has made the analysis of fluvial topography a popular technique for deciphering relative, and some argue absolute, histories of rock uplift. Here we present results from a study of the fluvial topography from south-central Crete demonstrating that river longitudinal profiles indeed record the relative history of uplift, but several other processes make it difficult to recover quantitative uplift histories. Prior research demonstrates that the south-central coastline of Crete is bound by a large (~100 km long) E-W striking composite normal fault system. Marine terraces reveal that it is uplifting between 0.1–1.0 mm yr−1. These studies suggest that two normal fault systems, the offshore Ptolemy and onshore South-Central Crete faults linked together in the recent geologic past (Ca. 0.4–1 Myrs bp). Fault mechanics predicts that when adjacent faults link into a single fault the uplift rate in the linkage zone will increase rapidly. Using river profile analysis we show that rivers in south-central Crete record the relative uplift history of fault growth and linkage, as theory predicts that they should. Calibration of the commonly used stream power incision model shows that the slope exponent, n, is ~ 0.5, contrary to most studies that find n ≥ 1. Analysis of fluvial knickpoints shows that migration distances are not proportional to upstream contributing drainage area, as predicted by the stream power incision model. Maps of the transformed stream distance variable, χ, indicate that drainage basin instability, drainage divide migration and river capture events complicate river profile analysis in south-central Crete. Waterfalls are observed in southern Crete and appear to operate under less efficient and different incision mechanics than assumed by the stream power incision model. Drainage area exchange and waterfall formation are argued to obscure linkages between empirically derived metrics and quasi-physical descriptions of river incision, making is difficult to quantitatively interpret rock uplift histories from river profiles in this setting. Karst hydrology, break down of assumed drainage area-discharge scaling and chemical weathering might also contribute to the failure of the stream power incision model to adequately predict the behavior of the fluvial system in south-central Crete.

Glacial history reflected by geochemically constrained stratigraphic sections in the Chaudière River drainage basin of the Canadian Appalachians

2018 ◽  
Vol 91 (1) ◽  
pp. 234-249 ◽  
Author(s):  
William W. Shilts ◽  
Olivier J. Caron
Keyword(s):  
New York ◽  
Drainage Basin ◽  
Early Pleistocene ◽  
Eastern United States ◽  
Eastern Canada ◽  
Glacial Deposits ◽  
Glacial Sediments ◽  
Oxygen Isotope Stage ◽  
River Region ◽  
History Of

AbstractThe Chaudière River region in the Appalachian Mountains of eastern Canada is approximately 700 km north of the southernmost Pleistocene glacial deposits in New York and New Jersey. Detailed compositional analyses of glacial and non-glacial sediments from stratigraphic exposures and more than 40 boreholes drilled to bedrock provide a compositionally constrained record of glacial events, which include deposits of one Marine Oxygen Isotope Stage (MIS) 6 and two post-MIS 5 glaciations. The glacial and associated proglacial deposits rest on compositionally distinctive, preglacial saprolite that is preserved in deeper valleys. These observations constrain interpretations of the glacial/Pleistocene history of the eastern United States and Canada. The fact that there is no unequivocal evidence of pre-MIS 6 till in the Chaudière River region, while there are well-documented pre-MIS 6 glacial deposits south of there and in the American Midwest, also has major climatic implications. The Laurentide Ice Sheet and its ancestors must have been more robust in the west in the early Pleistocene and in the east most recently.

Modern Alluvial History of the Paria Rver Drainage Basin, Southern Utah

1986 ◽  
Vol 25 (3) ◽  
pp. 293-311 ◽  
Author(s):  
Richard Hereford
Keyword(s):  
Sediment Yield ◽  
Drainage Basin ◽  
River Channel ◽  
High Flow ◽  
Low Flow ◽  
Vertical Accretion ◽  
Important Process ◽  
Stream Channels ◽  
History Of ◽  
Peak Flood

Stream channels in the Paria River basin were eroded and partially refilled between 1883 and 1980. Basin-wide erosion began in 1883; channels were fully entrenched and widened by 1890. This erosion occurred during the well-documented period of arroyo cutting in the Southwest. Photographs of the Paria River channel taken between 1918 and 1940 show that the channel did not have a floodplain and remained wide and deep until the early 1940s. A thin bar (<50 cm), now reworked and locally preserved, was deposited at that time. Basin-wide aggradation, which began in the early 1940s, developed floodplains by vertical accretion. The floodplain alluvium, 1.3–3 m thick. consists of two units recognizable throughout the studied area. An older unit was deposited during a time of low flow and sediment yield whereas the younger unit was deposited during times of high flow, sediment yield, and precipitation. Tree-ring dating suggests that the older unit was deposited between the early 1940s and 1956, and the younger between 1956 and 1980. The units are not time transgressive, suggesting that deposition by knickpoint recession was not an important process. High peak-flood discharges were associated with crosion and low flood discharges with aggradation. The erosional or aggradational mode of the streams was determined principally by peak-flood discharge, which in turn was controlled by precipitation.

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