Fossils of the Carpathian Region

5. The Paleocene and Eocene

225 The Cenozoic, meaning “recent life,” is the next major era in the history of the Earth, and covers the period from 65 million years ago until the present. The name comes from two Greek words, which can be translated as “new animal life.” This is intended to indicate that the animal life of this era was similar to that seen today (in contrast to the Mesozoic and the much older Paleozoic). During the Cenozoic the continents drifted into their present—and, for us, seemingly final—positions. Remarkable changes also occurred in the climatic conditions of the Earth: the balanced climate of the Mesozoic was followed by a more extreme and colder one. This climactic change was gradual, and probably started in the Late Eocene. In the polar regions—at first presumably in the Antarctic—a continental ice sheet slowly developed. Indeed, the last 2 million years of the Cenozoic—the epoch called the Pleistocene—are referred to as an Ice Age in the strictest sense. Parallel to this change in climate and paleogeography, a change in the living world on Earth also occurred. After the extinction event at the end of the Cretaceous, vacant niches were filled by recovering lineages of animals and plants. The evolution of flora is principally characterized by the explosive expansion of angiosperms. At the end of the Cretaceous empty marine niches were also filled by representatives of different groups. Ammonites and belemnites—together with several other creatures that are characteristic of the Mesozoic oceans—became extinct, and the diversity of the formerly significant brachiopods declined. Their position in the living world has been assumed by bivalves. This group has existed for a long time, and thrived in the Tertiary. Moreover, new groups of planktonic foraminifera appeared that now play an important role in defining Tertiary stratigraphic subdivisions. The evolution of vertebrates at this time was characterized by the expansion of mammalian lineages. If the Mesozoic can be called the age of reptiles, then the Tertiary should be known as the age of mammals. Due to one small, but significant, moment in the evolution of this group, one branch of the primate tree was pushed in a specific direction, and for the first time in Earth’s 4-billion-year history a creature evolved that was able to acquaint itself with that history: Man. The long unit of geological time called the Cenozoic is divided into the Tertiary and the Quaternary. The Tertiary —a no longer official, but still widely used, subdivision that encompasses more than 62 million years—is represented by two periods: the Paleogene and the Neogene. The Quaternary spans the period from 2.6 million years ago to the present. From this last period we know about many rocks and sediments that were left behind across the Carpathian Basin. Further subdivision of the Tertiary is based on correspondence between past and recent life, based in large part upon the similarities between fossil and recent bivalve and gastropod faunas. The names of the epochs of the Tertiary—the Paleocene, Eocene, Oligocene , Miocene, and Pliocene—emphasize ever-increasing similarity with recent faunas. From the Oligocene onward, the Carpathian Basin was covered by the Paratethys Sea, which spread over the depression north of the Alp-Carpathian range and extended from present-day Switzerland as far east as the Aral Sea. Until the end of the Middle Miocene, completely marine conditions prevailed. The Late Miocene is the age of the brackish-water Lake Pannon. During the Pliocene, the entire area of the Carpathian Basin became a continental terrain. The varied Tertiary sediments and rocks of the Carpathian region and their fossil contents reflect these paleoenvironmental changes. Paleocene The end of the Cretaceous period was characterized by strong orogenic movements, including thrusting (nappe formation) and uplift in the Carpathian-Pannonian region . This area became a continental terrain which was to last for a long period, and erosion was predominant at the beginning of the Tertiary. Sedimentation took place sporadically, and only a few of the rock formations from 5 The Paleocene and Eocene 226 t h e c e n o z o i c this time period have remained undisturbed: rocks in the Carpathian region that date to the Paleocene (the first 10 million years of the Tertiary) are found only rarely. Layers of probable Paleocene age are known only from deep boreholes in Hungary, and the only fossil locality of importance in the Carpathian region is at Jibău, Transylvania. A rich association of fossil...