Occurrence of some campanian-maastrichtian organic-walled microfossils from Enugu Shale, Anambra Basin, Southeastern nigeria: Implications for age and paleoenvironments

Detailed geological field mapping and sampling of the Enugu Formation in the Anambra Basin has been carried out in order to re-examine the age of sediments and reconstruct their paleoenvironments of deposition. A total of ten (10) outcrop samples of shale were subjected to palynological laboratory examination, using conventional method of acid demineralization and maceration techniques for recovering acid-insoluble organic-walled microfossils from sediments. Two main lithological units were distinguished: - carbonaceous fissile shale and siltstone. A late Campanian - Earliest Maastrichtian age was assigned based on index palynomorphs marker taxa Longapertites marginatus (overwhelming abundance), Monocolpites marginatus, Zlivisporis blanensis, and Echitriporites trianguliformis. The age designation was strengthened by the occurrence of a well-known stratigraphic age-diagnostic organic-walled microplankton Coronifera tubulosa, Senegalinium spp. and Andalusiella polymorpha. Palynomorphs of environmental value include Cyathidites minor, (a tree fern of wet, forested, tropical to temperate regions, usually most developed in mountainous / highland terrains under moist and equable climate); Spinizonocolpites baculatus/echinatus, Longapertites marginatus, Mauritidites crassibaculatus and Moncolpites marginatus, which are palm pollen that inhabit similar brackish water as the mangrove. A non-marine to marginal marine depositional setting has therefore been proposed for the Enugu Formation.

Slowing down the overturning – Insights from conceptual modelling on a stably stratified Mediterranean Sea during the Messinian Salinity Crisis

<p>Although the Mediterranean is known for its equable climate, this does not apply on geological timescales. At the end of the Miocene, salinity of the Mediterranean Sea exceeded gypsum and halite saturation, leading to the youngest known salt giant to form in a relatively short time span. This event is called the Messinian Salinity Crisis. Insight into the exact circumstances leading to this extreme situation would increase our understanding of today’s system and how it would react to climatic changes. Some of the theories rely on a drastic change in circulation, leading to a stably stratified water column at high salinities. It is yet to be determined how realistic these ideas are.</p><p>Conceptual box models can help to find answers to this. In a previous study it was already shown that a decrease in the rate of deep water formation in the margins can lead to a stratified water column. Here we used a predefined value for the overturning. In contrast, in the present study, the circulation, including the exchange through the strait of Gibraltar, is dynamically driven by density differences. By modelling stratification for various assumptions regarding the efficiency of the strait of Gibraltar, evaporation and the connectivity of the margins, this set-up ables us to get in-depth insights regarding the system in general, and the influence of climate and bathymetry on the circulation, specifically.</p><p>This model brings us one step closer to an understanding of the circumstances of this extreme state of the Mediterranean Sea</p>

Topological Climate Change

This article presents a bifurcation analysis of a simple Energy Balance Model (EBM) of the Earth’s climate, which suggests that topological change has occurred in the paleoclimate history of the Earth. In the theory of dynamical systems, two systems that are topologically equivalent have solutions with the same qualitative behavior. A change in the topological equivalence class, as parameters are varied, is called a bifurcation. Thus, a bifurcation demarcates a significant change in the behavior of the solutions of a dynamical system. If that system represents climate, then that topological change may represent an abrupt transformation of the climate, occurring even with a very small change in the forcing parameters. In this paper, the existence of a cusp bifurcation is proven in a climate EBM. The existence of this cusp bifurcation implies the co-existence of two distinct stable equilibrium climate states (bistability), as well as the existence of abrupt transitions between these two states (fold bifurcations) in the EBM. These transitions are dependent on the past history of the system (hysteresis). The two universal unfolding parameters for the cusp bifurcation have been determined as functions of the relevant physical parameters. These ideas lead to the proposal of a new explanation for the so-called warm equable climate problem of the mid-Cretaceous and early Eocene. The analysis presented here implies that the mid-Cretaceous and early Eocene climate systems are topologically equivalent to each other, but they are not topologically equivalent to the preindustrial modern climate. The transition from the warm, equable paleoclimate to today’s cooler nonequable climate occurs via fold (or saddle-node) bifurcations in the EBM, which correspond to the Eocene-Oligocene Transition (EOT) at the south pole and the Pliocene-Pleistocene Transition (PPT) at the north pole, in the paleoclimate record of Earth.

An energy balance model for paleoclimate transitions

A new energy balance model (EBM) is presented and is used to study paleoclimate transitions. While most previous EBMs only dealt with the globally averaged climate, this new EBM has three variants: Arctic, Antarctic and tropical climates. The EBM incorporates the greenhouse warming effects of both carbon dioxide and water vapour, and also includes ice–albedo feedback and evapotranspiration. The main conclusion to be inferred from this EBM is that the climate system may possess multiple equilibrium states, both warm and frozen, which coexist mathematically. While the actual climate can exist in only one of these states at any given time, the EBM suggests that climate can undergo transitions between the states via mathematical saddle-node bifurcations. This paper proposes that such bifurcations have actually occurred in Paleoclimate transitions. The EBM is applied to the study of the Pliocene paradox, the glaciation of Antarctica and the so-called warm, equable climate problem of both the mid-Cretaceous Period and the Eocene Epoch. In all cases, the EBM is in qualitative agreement with the geological record.

Species diversity and community structure of butterfly in urban forest fragments at Lucknow, India

The survey was carried out between September 2015-August 2016 in five different localities in Lucknow like Bijli Pasi Quila, Smriti Upvan, Vanasthali Park, Butchery Ground and BSNVPG College Campus, Lucknow, 26.84’N latitude and 80.92’E longitude, is located at an elevation of 126 meters above sea level and in the plain of northern India. Its location is responsible for the diverse weather patterns and climate change. The region has tropical dry equable climate having three main seasons; cold, hot and rainy season. Temperature of the city ranges from 23.8- 45.8°C in summer and 4.6-29.7°C in winter. During the study, butterflies were collected mainly with the help of circular aerial net, which were then placed in killing jar. Killed butterflies were stored in the insect box by proper pinning them for identification. During the course of study, 30 species of butterflies, belonging to 26 genera, representing 5 families, were recorded in Lucknow. 11 Species from nymphalidae, 7 sp. pieridae, 5 sp. from lycaenidae, 3 sp. From hesperidae and 3 sp. from papilionidae were recorded in all selective sites. The butterflies observed were categorized into groups based on their relative numbers; most common >9-10, common 6-8, rare 3-5, very rare 0-2. This study is used for academic as well as applied importance.

Geochemical Evolution of Earth's Continental Crust

Earth’s unique continental crust represents the active interface between the deep earth and the surface earth system, and is crucial for the survival and diversification of life on Earth, both as a source for nutrients and a component in the silicate weathering feedback that stabilizes Earth’s equable climate on billion-year timescales. However, many open questions remain regarding the formation and secular temporal evolution of Earth’s crust – in part due to the extremely poorly-mixed nature of Earth’s continental crust such that compositional heterogeneity at any one point in geologic time typically dwarfs any systematic variation over time. New computational approaches enabled by the emergence of large, freely accessible geochemical datasets provide a way to see through this heterogeneity and extract quantitative information about underlying processes and variables that drive the evolution of Earth’s crust over geologic time.

An Energy Balance Model for Paleoclimate Transitions

A new energy balance model (EBM) is presented and is used to study Paleoclimate transitions. While most previous EBMs dealt only with the globally averaged climate, this new EBM has three variants: Arctic, Antarctic and Tropical climates. This EBM incorporates the greenhouse warming effects of both carbon dioxide and water vapour, and also includes ice-albedo feedback. The main conclusion to be drawn from the EBM is that the climate system possesses multiple equilibrium states, both warm and frozen, which coexist mathematically. While the actual climate can exist in only one of these states at any given time, the climate can undergo transitions between the states, via mathematical saddlenode bifurcations. This paper proposes that such bifurcations have actually occurred in Paleoclimate transitions. The EBM is applied to the study of the Pliocene Paradox, the Glaciation of Antarctica and the so-called warm, equable climate problem of both the mid-Cretaceous Period and the Eocene Epoch. In all cases, the EBM is in qualitative agreement with the geological record.

Coleoptera from the middle-upper Eocene European ambers: generic composition, zoogeography and climatic implications

The paper contains a review of coleopteran genera known from Baltic, Bitterfeld and Rovno amber localities. Altogether 420 genera (191 extinct and 229 extant) from 78 families are listed from these three Lagerstätten (as of 7 March 2017). The listed beetles were analyzed zoogeographically and distributional maps for 72 genera were compiled. One-quarter (56) of the genera that have survived since the Eocene have cosmopolitan ranges at present; 35 extant genera have been extripated from the Palaearctic since the Eocene. Approximately 40% of beetle genera from the middle-upper Eocene European ambers can be encountered in the wild in present-day Europe, while 5 of these genera are supposed to be European relict endemics originating in Fennosarmatia. The general similarity of the Baltic amber (s.l.) beetle assemblage to modern south Palaearctic fauna is the strongest, the Nearctic elements are more numerous in the middle-upper Eocene European ambers than the Oriental taxa. The simplified Mutual Climatic Range (MCR) method was used for palaeoclimate reconstruction based on fossil beetles. The coleopteran assemblage of Baltic amber is interpreted as indicative of warm temperate, humid, equable climate with reduced thermal seasonality [annual average temperatures range from +10–20˚C; mean of the coldest month temperatures around +10˚C; mean of the hottest month temperature around +20–24˚C; annual precipitation around 750–1500 mm]. The primary importance of high humidity for existence of the Eocene biota is pointed out.

The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?

Geological data for the Early Eocene (56–47.8 Ma) indicate extensive global warming, with very warm temperatures at both poles. However, despite numerous attempts to simulate this warmth, there are remarkable data–model differences in the prediction of these polar surface temperatures, resulting in the so-called ‘equable climate problem’. In this paper, for the first time an ensemble with a perturbed climate-sensitive model parameters approach has been applied to modelling the Early Eocene climate. We performed more than 100 simulations with perturbed physics parameters, and identified two simulations that have an optimal fit with the proxy data. We have simulated the warmth of the Early Eocene at 560 ppmv CO 2 , which is a much lower CO 2 level than many other models. We investigate the changes in atmospheric circulation, cloud properties and ocean circulation that are common to these simulations and how they differ from the remaining simulations in order to understand what mechanisms contribute to the polar warming. The parameter set from one of the optimal Early Eocene simulations also produces a favourable fit for the last glacial maximum boundary climate and outperforms the control parameter set for the present day. Although this does not ‘prove’ that this model is correct, it is very encouraging that there is a parameter set that creates a climate model able to simulate well very different palaeoclimates and the present-day climate. Interestingly, to achieve the great warmth of the Early Eocene this version of the model does not have a strong future climate change Charney climate sensitivity. It produces a Charney climate sensitivity of 2.7 ° C, whereas the mean value of the 18 models in the IPCC Fourth Assessment Report (AR4) is 3.26 ° C±0.69 ° C. Thus, this value is within the range and below the mean of the models included in the AR4.