Introduction
In the Cenozoic, compared to the previous Phanerozoic eras, climatic reconstructions according to paleobotany and geographical finds have a higher degree of reliability. The study of the High Canadian Arctic through the prism of such important climate parameters as average annual temperature and carbon dioxide concentration allows studying the evolution of Earth. Geological processes throughout the Cenozoic have shaped the modern appearance of the oceans and continents. The climate and, as a consequence, the flora was gradually changing. This also affected the development of mammals, in particular the emergence of humans. Humankind, having reached a particular stage of civilization, began to render a strong influence on the surrounding nature. In this regard, there is often talk of global warming seen in the Holocene. The purpose of this work is to compare the Eocene and Holocene epochs in the northern latitudes, in particular, the High Canadian Arctic.
Brief Description
The Cenozoic era is remarkable for the development of mammals that have replaced dinosaurs and other reptiles, which are almost entirely extinct. The Cenozoic is divided into several eras, among which the Eocene and Holocene. The Eocene is the second Paleogene period, which lasted until 33.9 million years ago (Willard et al., 2019). The Eocene Earth healed its wounds thoroughly after the Cretaceous–Paleogene extinction event. The death of reptiles contributed to the development of all the mammals that inhabited the entire planet. Holocene is the last epoch of the Quaternary, which began 11,700 years ago and continues to this day (Briner et al., 2016). In other words, there is a difference of nearly forty million years between the two analyzed epochs, for which not only life has changed, but also climatic conditions. According to data presented in Figure 1, the average temperature and concentration of carbon dioxide decreased. The total CO2 content has been declining for tens of millions of years but has started to increase gradually in recent times.
Life in the Eocene Era
The parallel drop in temperature and carbon dioxide concentration has left an indelible mark in the Eocene High Canadian Arctic. The prehistoric Arctic can be compared to the tropical zones where favorable conditions have been created for exotic plants such as palms (Willard et al., 2019). This is confirmed by numerous paleontological remains of fossil forms of cypress forests and swamps (Eberle & Greenwood, 2012). Gradual cooling occurred from the middle Eocene, the continental climate became drier, and therefore the forests consisting of the Metasequoia were replaced by broad-leaved areas (Eberle & Greenwood, 2012). Only in those areas of the High Canadian Arctic, where the climate was more humid and rained, broadleaved forests were replaced by coniferous plants (Salpin et al., 2019). Palm, laurel, and magnolia inclusions could also often be found between them (Willard et al., 2019). Over millions of years, High Canadian Arctic vegetation continued to thrive, with new groups of mammals becoming increasingly prominent and progressive. Among fauna, climate indicators include fossil remains of crocodiles, some forms of large mammals, colonial corals, and mollusks (Eberle & Greenwood, 2012). The northern waters of the High Canadian Arctic during the Eocene period began to become warmer, and corals have populated them as a result. Along with bat ideas and sharks, the first whale species emerged in the ocean depths of the High Canadian Arctic (Bears, 2017). They were the early mammals to develop the ocean and marine aquatic environments. The abundance of plant food influenced the development of heterotrophs: large herbivores such as Coryphodon existed in the Arctic Eocene zones (Eberle & Greenwood, 2012). The second part of the Eocene is marked by periods of cooling that lasted until the end of an era. In addition, due to the abundance of plankton, some animals have returned to the waterways. The end of the Eocene was marked by the fall of a giant asteroid whose impact crater is located on the east coast of the North American continent. This circumstance launched new tectonic processes in the Earth’s interior, accompanied by the separation of territories and subsequent isolation of biological species.
Life in the Holocene Era
Holocene is characterized by alternating warm and cold, dry and wet periods, which range in duration from several hundred to a thousand years. In the Arctic basin, a sophisticated mobile system was formed of small local glacier coverings that, at times, partially joined and reached the shelf. Therefore, the position of the northern boundary of the forest is an essential indicator of changes in the state of vegetation and climate of the High Canadian Arctic. The flowering plants, which had been actively conquering the planet since the Cretaceous period, continued to inhabit the land at northern latitudes. Dwarf forms of birch and willow can still be found on these lands, but the dominant niche is occupied by classical tundra plants (Briner et al., 2016). The leafy plants of the tropical climate have given way to other types of trees, such as pine forests adapted to low temperatures. Additionally, small lichens gradually occupied a significant ecological niche. The modern fauna of the Arctic is just a remnant of the rich and diverse life of the glacial period of the past, the most famous representative of which was the vast mammoth (Callaghan & Nuttall, 2019). The fauna included many mammal species which, through adaptations, managed to adapt to the cold continental climate of forest-steppe and tundra areas with their permafrost. Zoogeographical conditions in the Holocene on High Canadian Arctic lands are harsh and unfavorable for most terrestrial animals. The fauna of the Arctic is not rich in species, but the most characteristic inhabitants of these areas include reindeer, polar bears, foxes, hares, and owls.
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