Seeing Red: Some Aspects of the Geological and Climatic History of the Australian Arid Zone

2018 ◽  
pp. 5-43 ◽  
Author(s):  
Brad J. Pillans
Keyword(s):  
Arid Zone ◽  
History Of ◽  
Climatic History

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

2017 ◽  
Vol 4 ◽  
pp. 1-53 ◽  
Author(s):  
Paul Murphey ◽  
K.E. Townsend ◽  
Anthony Friscia ◽  
James Westgate ◽  
Emmett Evanoff ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Middle Eocene ◽  
Green River Basin ◽  
Green River ◽  
Scientific Exploration ◽  
History Of ◽  
Climatic History ◽  
Field Excursion ◽  
Land Mammal ◽  
Bridger Formation

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

Late Pleistocene–Holocene environmental and climatic history of a freshwater paramo ecosystem in the northern Andes

2020 ◽  
Vol 35 (8) ◽  
pp. 1046-1056
Author(s):  
Luisa Patiño ◽  
Maria Isabel Velez ◽  
Marion Weber ◽  
César A. Velásquez‐r ◽  
Santiago David ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Northern Andes ◽  
History Of ◽  
Climatic History

Biology and natural history of Caladenia

2009 ◽  
Vol 57 (4) ◽  
pp. 247 ◽  
Author(s):  
Kingsley Dixon ◽  
Raymond L. Tremblay
Keyword(s):  
Natural History ◽  
Arid Zone ◽  
Secondary Infection ◽  
Soil Surface ◽  
Growth Cycle ◽  
Cortical Cells ◽  
Herbaceous Perennials ◽  
Terrestrial Orchids ◽  
History Of ◽  
Soil Wetting

The genus Caladenia comprises species that exhibit remarkable consistency in terms of growth form and phenological patterns. All taxa are herbaceous perennials, with the shoot arising annually from a single, usually spheroid, tuber and producing a single, hairy leaf. The tuber is annually replaced either side-by-side with the parent tuber or terminating a descending structure known as a dropper. The dropper is a depth-seeking mechanism that enables placement of the tuber at depth in the soil as a means to avoid predation by surface-foraging native mammals or away from the high temperatures and desiccating conditions during summer dormancy. The 3--5 attenuated roots produced at the junction between the tuber and shoot and produced late in the growing cycle and devoid of mycorrhiza suggest their functional significance may relate to water uptake. Mycorrhizal endophytes are confined to a hypertrophic stem region at the soil surface (collar) subtending the leaf that positions the collar directly in the organically rich zone at the soil surface. This morphology is a unique characteristic of several Australasian orchids in the tribe Diuridae. Mycorrhizal infection occurs rapidly, with maximum colonisation in concert with the onset of breaking rains. Pelotons are restricted to cortical cells, with fully developed pelotons throughout infected tissues within a week or so of soil wetting. Infection occurs as a ‘once-off’ event, with little evidence of secondary infection later in the growth cycle and no evidence of peloton digestion. Some taxa utilise vegetative propagation, often leading to localised clustering as for taxa in the ‘filamentosa’ complex or, extensive clonal mats as found in Caladenia flava and C. latifolia where daughter tubers are produced at the end of extending horizontal outgrowths. For the majority of taxa, plants remain dry-season (summer) dormant from a few months up to 7 months for arid-zone taxa, with shoot emergence from the tuber of temperate species thought to occur in response to a drop in the mean minimum temperature. Pollination biology of Caladenia is apparently through a process of deception, either as food or sexual mimics, with some taxa engaging in self-pollination. Here we review the natural history of Caladenia and acknowledge that much of our understanding is based on assumptions of the biology of terrestrial orchids in general and emphasise areas of research and biological enquiry that will be critical in the development of an effective conservation program for the genus.

scholarly journals Atmospheric speciation of rocky planets from magma ocean outgassing

2020 ◽  
Author(s):  
Tim Lichtenberg ◽  
Dan J. Bower ◽  
Mark Hammond ◽  
Ryan Boukrouche ◽  
Shang-Min Tsai ◽  
...  
Keyword(s):  
Coupled Model ◽  
Initial Distribution ◽  
Occurrence Rate ◽  
Magma Ocean ◽  
Mantle Dynamics ◽  
Mantle Geochemistry ◽  
Prebiotic Chemical ◽  
History Of ◽  
Climatic History ◽  
Rocky Planets

<p>The earliest atmospheres of rocky planets originate from extensive volatile release during one or more magma ocean epochs that occur during primary and late-stage assembly of the planet (1). These epochs represent the most extreme cycling of volatiles between the interior and atmosphere in the history of a planet, and establish the initial distribution of the major volatile elements (C, H, N, O, S) between different chemical reservoirs that subsequently evolve via geological cycles. Crucially, the erosion or recycling of primary atmospheres bear upon the nature of the long-lived secondary atmospheres that will be probed with current and future observing facilities (2). Furthermore, the chemical speciation of the atmosphere arising from magma ocean processes can potentially be probed with present-day observations of tidally-locked rocky super-Earths (3). The speciation in turn strongly influences the climatic history of rocky planets, for instance the occurrence rate of planets that are locked in long-term runaway greenhouse states (4). We will present an integrated framework to model the build-up of the earliest atmospheres from magma ocean outgassing using a coupled model of mantle dynamics and atmospheric evolution. We consider the diversity of atmospheres that can arise for a range of initial planetary bulk compositions, and show how even small variations in volatile abundances can result in dramatically different atmospheric compositions and affect earliest mantle geochemistry and atmospheric speciation relevant for surficial prebiotic chemical environments (5). Only through the lense of coupled evolutionary models of terrestrial interiors and atmospheres can we begin to deconvolve the imprint of formation from that of evolution, with consequences for how we interpret the diversity revealed by astrophysical observables, and their relation to the earliest planetary conditions of our home world.</p> <div class=""><em>References</em></div> <ol> <li>Bower, D. J., Kitzmann, D., Wolf, A. S., et al. (2019). Astron. Astrophys. 631, A103.</li> <li>Bonati, I., Lichtenberg, T., Bower, D. J., et al. (2019). Astron. Astrophys. 621, A125.</li> <li>Kreidberg, L., Koll, D. D., Morley, C., et al. (2019). Nature 573, 87-90.</li> <li>Hamano, K., Abe, Y., Genda, H. (2013). Nature 497, 607-610.</li> <li>Sasselov, D. D., Grotzinger, J. P., Sutherland, J. D. (2020). Sci. Adv. 6, eaax3419.</li> </ol>

Two new species of freshwater sponges from Neotropical and Afrotropical Regions

Zootaxa ◽  
2020 ◽  
Vol 4728 (3) ◽  
pp. 363-371
Author(s):  
ULISSES PINHEIRO ◽  
LUDIMILA CALHEIRA ◽  
CELINA MARTINS ◽  
LIESL JANSON ◽  
RICKY TAYLOR ◽  
...  
Keyword(s):  
New Species ◽  
Valid Species ◽  
Single Specimen ◽  
Freshwater Sponges ◽  
Freshwater Systems ◽  
Morphological Complexity ◽  
Afrotropical Region ◽  
Two New Species ◽  
History Of ◽  
Climatic History

Geographic distributions of freshwater sponges are related to the geological and climatic history of the continents, on the presence of gemmules and the morphological complexity of this resistant body to withstand change. Gemmules are characteristic of the freshwater Families Spongillidae, Metaniidae and Potamolepidae. However, Acanthotylotra alvarengai, Echinospongilla brichardi and a number of other species within the genus Potamolepis do not produce gemmules. Potamolepis is endemic to the Afrotropical region with seven valid species. African freshwater sponges however, are mostly known from a single specimen (the holotype), due to the scarcity of material from these freshwater systems. In the present study, we describe two new species of non-gemmule bearing freshwater sponges from the Neotropical and Afrotropical Regions.  

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