Coupling of marine and continental oxygen isotope records during the Eocene-Oligocene transition

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148587/1/Sheldon_et_al_2016_GSA_Bulletin-EOT_marine-terrestrial_comparison.pd

Earth: Atmospheric Evolution of a Habitable Planet

Our present-day atmosphere is often used as an analog for potentially habitable exoplanets, but Earth's atmosphere has changed dramatically throughout its 4.5 billion year history. For example, molecular oxygen is abundant in the atmosphere today but was absent on the early Earth. Meanwhile, the physical and chemical evolution of Earth's atmosphere has also resulted in major swings in surface temperature, at times resulting in extreme glaciation or warm greenhouse climates. Despite this dynamic and occasionally dramatic history, the Earth has been persistently habitable--and, in fact, inhabited--for roughly 4 billion years. Understanding Earth's momentous changes and its enduring habitability is essential as a guide to the diversity of habitable planetary environments that may exist beyond our solar system and for ultimately recognizing spectroscopic fingerprints of life elsewhere in the Universe. Here, we review long-term trends in the composition of Earth's atmosphere as it relates to both planetary habitability and inhabitation. We focus on gases that may serve as habitability markers (CO2, N2) or biosignatures (CH4, O2), especially as related to the redox evolution of the atmosphere and the coupled evolution of Earth's climate system. We emphasize that in the search for Earth-like planets we must be mindful that the example provided by the modern atmosphere merely represents a single snapshot of Earth's long-term evolution. In exploring the many former states of our own planet, we emphasize Earth's atmospheric evolution during the Archean, Proterozoic, and Phanerozoic eons, but we conclude with a brief discussion of potential atmospheric trajectories into the distant future, many millions to billions of years from now. All of these 'Alternative Earth' scenarios provide insight to the potential diversity of Earth-like, habitable, and inhabited worlds.Comment: 34 pages, 4 figures, 4 tables. Review chapter to appear in Handbook of Exoplanet

Variation in n-alkane delta D values from terrestrial plants at high latitude: Implications for paleoclimate reconstruction

The molecular hydrogen isotope composition ((delta D) of leaf waxes from terrestrial plants is increasingly used to infer hydrological characteristics of ancient high latitude climates. Analysis of the hydrogen isotope composition of n-alkanes (delta D(n-alkane)) from a global dataset of individual plants growing at low and middle latitudes indicates that plant ecological life form is an important factor in determining the hydrogen isotope fractionation. However, environmental and biological controls of high latitudinal leaf wax delta D values are poorly understood because of a lack of delta D records from modern flora in these regions. We previously noticed smaller apparent hydrogen isotope fractionations between n-alkanes and environmental water (epsilon(alk-water)) in deciduous trees growing at high latitudes (&gt; 59 degrees N; Liu, W.-G., Yang, H., 2008. Multiple controls for the variability of hydrogen isotopic compositions in higher plant n-alkanes from modern ecosystems. Global Change Biology 14,2166-2177.) To further examine these issues, we measured delta D(n-alkane) from a variety of plants that inhabit high latitude environments and added critically needed leaf wax delta D data from grass and herbs to the existing global delta D(n-alkane) database. Inclusion of these new data with the existing global dataset (n = 408) confirms plant ecological life form as an important control for leaf wax delta D variation for terrestrial plants living at high latitudes. Our results suggest that, while precipitation delta D is captured in these high latitude plants, physiological characters such as leaf area, venation pattern and hydraulic system, that enhance transpiration rate during summer growth, may impart delta D(n-alkane) differences among plants with different ecological life forms.</p

Assessment of water quality using multivariate analysis�a case study on the Brahmaputra River, Assam, India

Chemical composition of river water is vital to assessment of water quality for irrigation, agriculture and domestic usage. Chemical attributes of riverine water primarily governed by natural weathering of rocks have become overshadowed by increasing range of anthropogenic activities. Progressive pollution of the river waters are critical as rivers in floodplain zones recharge ground water; a vital source of drinking water in India. The degree of impact of the anthropogenic activities within the surface waters of the developing countries has expanded significantly amid the past decades. Hence identification and quantification of natural as well as anthropogenic impact and understanding the source of contaminant is fundamental. In addition continuous monitoring of river water quality is required in order to maintain freshwater assets. The Brahmaputra River is the lifeline of Assam. People residing along its bank directly or indirectly are heavily dependent on the river for their livelihood. Majority of the population in the region is dependent on an agricultural economy. In the present study different multivariate statistical techniques such as cluster analysis (CA), principal component analysis (PCA) and factor analysis (FA) were applied for evaluation of spatial and temporal variations of water quality of the Brahmaputra River for two years (2011�2014) by monitoring nine sampling sites from upstream to downstream along the Assam stretch. The present study highlights the usefulness and need of multivariate statistical assessment of the database in identification of main process that influence the water quality of the river and probable source of contamination.by Pallavi Das and Manish Kuma

Enhanced transcription and translation in clay hydrogel and implications for early life evolution

In most contemporary life forms, the confinement of cell membranes provides localized concentration and protection for biomolecules, leading to efficient biochemical reactions. Similarly, confinement may have also played an important role for prebiotic compartmentalization in early life evolution when the cell membrane had not yet formed. It remains an open question how biochemical reactions developed without the confinement of cell membranes. Here we mimic the confinement function of cells by creating a hydrogel made from geological clay minerals, which provides an efficient confinement environment for biomolecules. We also show that nucleic acids were concentrated in the clay hydrogel and were protected against nuclease, and that transcription and translation reactions were consistently enhanced. Taken together, our results support the importance of localized concentration and protection of biomolecules in early life evolution, and also implicate a clay hydrogel environment for biochemical reactions during early life evolution

Ice as a protocellular medium for RNA replication

A crucial transition in the origin of life was the emergence of an informational polymer capable of self-replication and its compartmentalization within protocellular structures. We show that the physicochemical properties of ice, a simple medium widespread on a temperate early Earth, could have mediated this transition prior to the advent of membraneous protocells. Ice not only promotes the activity of an RNA polymerase ribozyme but also protects it from hydrolytic degradation, enabling the synthesis of exceptionally long replication products. Ice furthermore relieves the dependence of RNA replication on prebiotically implausible substrate concentrations, while providing quasicellular compartmentalization within the intricate microstructure of the eutectic phase. Eutectic ice phases had previously been shown to promote the de novo synthesis of nucleotide precursors, as well as the condensation of activated nucleotides into random RNA oligomers. Our results support a wider role for ice as a predisposed environment, promoting all the steps from prebiotic synthesis to the emergence of RNA self-replication and precellular Darwinian evolution

Rodent faunas from the Paleogene of south-east Serbia

Seven new rodent faunas are described from the Pčinja and Babušnica-Koritnica basins of south-east Serbia. The geology of the Tertiary deposits in the Pčinja and Koritnica-Babušnica basins of south-east Serbia is briefly reviewed. The fossil content of the new vertebrate localities is listed, and an inventory of the rodent associations is presented. The rodent associations are late Eocene-early Oligocene in age, interpreted on biostratigraphical grounds. These are the first rodent faunas of that age from the Balkan area, an important palaeogeographic location between Europe and Asia. The Muridae, with the subfamilies Pseudocricetodontinae, Paracricetodontinae, Pappocricetodontinae, Melissiodontinae and ?Spalacinae, are dominant with eight genera, four of which are new. The diversity of the Melissiodontinae and Paracricetodontinae in the faunas suggests that these subfamilies originated in this region. The bi-lophodont cheek teeth occurring in the Oligocene assemblages are identified as the first record of the Diatomyidae outside of Asia. In light of the large amount of new data, the palaeogeographic setting and faunal turnover of the Eocene-Oligocene is discussed