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Fossils of the Carpathian Region
By István Fozy, István Szente, Gareth Dyke Indiana University Press
Copyright © 2014 István Fozy and István Szente
All rights reserved.
ISBN: 978-0-253-00987-6
CHAPTER 1
The Paleozoic
The Precambrian, which makes up about 85 percent of the history of the solid Earth, is represented by very sporadic fossil assemblages in the Carpathian region. A few poorly preserved organic-walled microfossils extracted from "crystalline" metamorphic rocks in a few areas including the Apuseni Mountains of Romania are thought to come from the latest Precambrian. However, due to the scarcity of fossil assemblages of this age, a detailed treatment of the two eons of the Precambrian, the Archaic and Proterozoic, is unjustified given the general scope of this book. Our present knowledge indicates that the living world of the Precambrian was immensely poorer than that of the Paleozoic; there were no organisms possessing hard skeletons at this time, for example, and the most widespread traces of life in the Precambrian are biosedimentary structures called stromatolites. These are mounds of mud and blue-green algae, or cyanobacteria, that have been found on almost all continents, and are particularly characteristic of the Ediacaran (i.e., the period immediately preceding the Phanerozoic).
As noted above, fossils from the Paleozoic are rare in the Carpathian Region. There are, however, a few localities that have yielded attractive fossil assemblages.
Paleozoic sedimentary rocks are much more widespread in the Carpathian region than are those from the Precambrian and, indeed, some of them contain fossil assemblages of scientific value. These fossil floras and faunas, however, are rather isolated in space and time and hardly any can be said to be spectacular or notable. Although many of the known Paleozoic successions were deposited in freshwater environments, sediments yielding exceptionally preserved fossils, such as those from the celebrated Carboniferous Mason Creek biota of North America, are lacking. These fossil assemblages are much less diverse than are those of coeval marine deposits, and many Paleozoic successions in the Carpathian area in general have been metamorphosed by the heat and/or pressure of orogenic processes resulting in the partial or total destruction of fossils. With this in mind, Carpathian Paleozoic assemblages are treated in a single chapter, rather than discussed period by period.
MEMORIALS OF LOST PEOPLES AND FARAWAY COUNTRIES: PALEOZOIC PERIODS
The Paleozoic, also called the "Primary" in older literature, was at least 290 million years long and, as such, was longer than both the Mesozoic and Cenozoic put together. It is subdivided into six periods that can be distinguished in sections all around the world. The earliest of these periods, the Cambrian, was named after the Roman name for North Wales (Cambria). Indeed, the next youngest, the Ordovician and Silurian Periods, are named for tribes that once lived in the area of present-day Wales; the Devonian was named for the county of Devonshire. The name Carboniferous refers to the Latin name for coal (carbo) and, as such is, a rare example among geochronological names; finally, the youngest period of the Paleozoic, the Permian, was named after the Perm Province of Russia.
EARTH HISTORY IN A NUTSHELL
Over the course of the almost 300 million years of the Paleozoic, the face of the Earth changed fundamentally. At the beginning of the Cambrian most of the ancient shields forming the so-called core of the present-day continents were concentrated between the 60th latitudes, principally in the Southern Hemisphere. Their arrangement differed markedly from that of today. Some continents (Africa, India, South America, Australia, New Guinea, and Antarctica) formed a huge supercontinent (Gondwanaland) in the Cambrian—the latter three being its northernmost "tongue," lying on the northern hemisphere. North America (Laurentia) and the landmass that would eventually constitute Europe (Baltica) were separated from one another by the Iapetus Ocean. The microcontinents Kazakhstania and Siberia, separated from all other landmasses, were situated near the equator.
The climate of the Cambrian is thought to have been warmer and more balanced than that of the present day and, in contrast to the Precambrian and Ordovician, no traces of glacial sediments have been found. At the very beginning of the Cambrian the biggest event in the history of life is thought to have taken place, the sudden and almost simultaneous appearance of both fossils with hard skeletons and several animal phyla, an event usually described as "the Cambrian explosion." This remains one of the most puzzling enigmas in evolution. In the Cambrian (actually until the end of the Silurian) life was mostly restricted to oceans.
During the Ordovician, the Northern Hemisphere was almost entirely covered with oceans. At the end of this period, considerable areas of the southern continent, including present-day North Africa, became covered with inland ice and glaciers. In the Silurian, huge parts of this region were flooded by ocean; in the tropics evaporite rocks were deposited, while at higher latitudes the ice age persisted. The ice-covered South Pole was situated in present-day Brazil; the Iapetus Ocean became narrower and narrower in the Silurian until, finally, it closed.
Sediments eroding from the folding and uplifting primeval Caledonian chain, whose remains form mountains in the eastern part of North America, on the British Isles, and on the Scandinavian Peninsula, were deposited in the Devonian. The continental succession that resulted from this erosion is widely known as the Old Red Sandstone. A new phase of mountain building began in the Carboniferous and lasted until the end of the Paleozoic and resulted in the formation of the Hercynian or Variscian Chain. The latter has two branches in Europe: the northern one stretches from the southern part of Northern Ireland to the Sudetes Mountains in Poland; the southern branch is traceable across the Iberian Peninsula. Details of the formation of the Hercynian Chain are still unknown, but the approximately 4,000-kilometer-long Ural Mountains, which mark the collision point between the ancient continents of Siberia and Baltica, also belongs to the Variscian Belt. The enormous weight of rock bodies thrust over one another during the Hercynian orogeny even created a flexure of the Earth's crust, which resulted in a series of depressions lying in front this major orogenic belt. These basins provided places for the subsequent deposition of Upper Carboniferous coal measures.
By the mid-Permian, the largest parts of the continental crust assembled into the supercontinent called Pangaea, extending over all climatic belts, and were surrounded by a global ocean called Panthalassa. A huge equatorial ocean divided Pangaea into a northern and a southern part, called Laurasia and Gondwanaland, respectively. The eastward open "embayment" of Panthalassa is named Tethys, after the sister of Oceanus in ancient Greek mythology. This name for the ancient ocean that dominated the surface of our planet for near 200 million years, was coined by influential Viennese geologist and conservative politician Eduard Suess (1831–1914), in his fundamental work The Face of the Earth (Das Anlitz der Erde). This work, more than 3,000 printed pages, laid long-enduring foundations for thinking about the Earth. In areas in the Permian South Pole glacial deposits were abundant, whereas in Europe red sandstone successions indicate the dominance of a hot and dry climate.
EARLY DEVELOPMENT OF THE LIVING WORLD
In the Paleozoic era there was a tremendous change in the living world. Among the marine invertebrates possessing hard skeletons, whose remains form the majority of the fossil record, three successive assemblages—usually called evolutionary faunas—can be distinguished. The dominant groups within these were especially diverse in an interval of the Paleozoic—if the number of the families is considered—and later on were replaced, gradually or suddenly, by other groups. The Cambrian was, therefore, the time of trilobites. Extinct mollusks known as hyoliths as well as monoplacophorans, inarticulate brachiopods, and primitive echinoderms also comprised the Cambrian evolutionary fauna.
In the Ordovician, articulate brachiopods became dominant in benthic communities and together with massive and lacelike bryozoans, reef-forming stromatoporoideans classified alongside sponges, cephalopods, sea lilies, starfish, and graptolites, they constitute the Paleozoic evolutionary fauna. The leading role of brachiopods persisted until the end of the Permian, when the brachiopods were replaced by different groups of organisms that have remained dominant in modern seas: bivalves, gastropods, vertebrates, arthropods, and bryozoans. The later history of brachiopods, this once abundant group, was quite different—and some managed to survive the decline. The inarticulate brachiopod Lingula (small tongue), for example, has persisted for around 500 million years, having changed little, and is today considered a so-called living fossil.
Besides fundamental changes in the composition of marine assemblages, conquest of the continents also occurred in the Paleozoic, at the end of the Silurian and in the Devonian. Spiders and scorpions were the first to inhabit dry lands, and the remains of the first amphibians—the first tetrapod animals—are known from the Upper Devonian. The hot and humid climate of the Carboniferous was especially favorable for the development of life on land, and some plants and insects are known to have reached gigantic sizes. Reptiles became very diverse in the Late Carboniferous, soon after their appearance, and the earliest mammal-like reptiles are known from the Permian.
The marine biota suffered a mass extinction at the end of the Permian and the inhabitants of shallow waters were especially afflicted. About 95 percent of invertebrate families, including some emblematic organisms of the Paleozoic like the fusulinid foraminifers, corals of the orders Rugosa and Tabulata, trilobites, and most of the previously dominant brachiopod groups, disappeared. This extinction was not a rapid event, having lasted several million years; it is interesting that little of the continental biota was affected.
Although all of the groups mentioned above were already in decline in the Permian and their diversity was already strongly reduced, the coincidence of their total disappearance has given scientists plenty to think about and has so far remained an enigma. Today the process of extinction is intensively studied, not just so that we can learn lessons for the future: formation of an anoxic water layer, global cooling, and lethal radiation generated by a supernova explosion that occurred close to Earth have all been proposed as possible causes for the Permian mass extinction, the most severe catastrophe that has ever befallen life on Earth. Finally, as a consequence of the formation of Pangaea, the area covered with shallow water also decreased significantly at this time and this could have also had a hand in triggering the mass extinction.
CHARACTERISTIC ROCKS
Because the formation of some rock types is confined to certain periods in Earth history, many Paleozoic sediments are characteristic to this era. In general, however, the Carpathian Basin has relatively few rocks of Paleozoic age.
The few successions of this age that are known from this region have restricted areal extent. In Hungary, these rocks are found in the Mecsek Mountains, in the Transdanubian Range and northern Hungary. Successions of considerable extent are also found in Styria in Austria (the Paleozoic of Graz), in the Gemerské (or Slovenské) Rudohorie in Slovakia (the Gemer Paleozoic), and in the Apuseni Mountains and the Banat region of Romania. A review of the Paleozoic geology and paleontology of Hungary, intended to be exhaustive, was published by József Fülöp (1928–1994) the former rector of Eötvös Loránd University in Budapest.
Fülöp 1990, 1994
The Fusulina Limestone
Foraminifera appeared at the beginning of the Cambrian but remained small in size for the next 200 million years. The first larger foraminifera that attained sizes of several centimeters appeared in the Carboniferous and belong to the order Fusulinidae. Fusulinas, like all larger-sized foraminifera, lived in shallow seas in the tropical belt and so their occurrence is indicative of the original periequatorial position of their depositional environment. As happened to rocks in the Carpathian Basin, some sedimentary successions have been moved, in some cases several thousands of kilometers, to their present positions by forces of plate tectonics.
The presence of Fusulina can even be seen on the weathered surfaces of limestones because these larger forams, similar to other related taxa, usually occur in large, often rock-forming quantities. However, the resistance of different rocks and fossils to weathering can vary; often fusulinids are seen at the surface as rounded or elongate outlines, and they are usually darker than the embedding rock. Since the outer shapes of different species, or even genera, of these forams are often the same, determination requires microscopic study using thin-sections. How these sections are made is explained below.
The order Fusulinidae, and thus Fusulina limestone, is characteristic of the Carboniferous and Permian. The genus Fusulina has, however, a much shorter range and is restricted to the Middle and Upper Carboniferous. Fusulina limestones are known to crop out in the Carboniferous of the Bükk Mountains and in Dobšiná, Slovakia, whereas representatives of the genus Codonofusiella, also belonging to Fusulinidae, are found in Permian limestones in the Bükk Mountains.
Red Sandstones
Successions predominantly consisting of red, or in some cases gray or green, sandstones, conglomerates, or finer-grained rocks that were deposited in continental environments under arid or semiarid climates are widespread throughout the Permian of Europe and are likewise found in the Carpathian Basin. Among them, the most famous is the Rotliegend (the "red underlying succession") that forms the lower unit of the traditionally two-part Permian (equivalent to the "Dyas" of older literature) in Germany. The word "Rotliegend" refers to the stratigraphic position of this succession with respect to the Zechstein succession, which is of economic importance because it contains evaporites and ore deposits such as the Mansfeld Copper Shale. The Val Gardena, or Gröden, Sandstone in the Southern Alps as well as the Verrucano—a rock named for its peculiar weathered surface that resembles a wart (verruca in Latin)—also belongs to this group of sedimentary rocks. In Hungary, this particular lithofacies is represented by the Balatonfelvidék Sandstone, uranium-bearing Permian sandstones in the Mecsek Mountains and the Turony Formation in Southern Transdanubia that have been explored using boreholes. A common feature of these successions is that they almost completely lack body fossils, but they are nevertheless worth mentioning because they do contain traces left by amphibians and reptiles. The processes of deposition and diagenesis of these rocks have prevented the preservation of bones and teeth, and so only ichnogenera and ichnospecies have been identified.
In general, most Permian rocks in southern Europe contain ichnofaunas, but in Hungary just a few examples have so far been found. György Majoros, a recognized authority on Permian sedimentology who worked for the former Mecsek Ore Mining Company, was the first to document (in 1964) the occurrence of reptile traces in the Pálköve Quarry at Balatonrendes.
Pentadactyl (five-fingered) traces attributed to the ichnogenus Korynichnium were formally described in 1968 by András Kaszap, who was working as an assistant professor at Eötvös Loránd University at the time. He later became the chief geologist on the board of directors for the baths in Budapest. Since this first description, a three-fingered trace has also been found at the same locality and in the 1960s, additional traces were found in cores from borehole Turony-1 drilled during subsurface geological investigations in the Mecsek-Villány region. These violet-brown sandstone beds have yielded two types of traces and some of them were identified by well-known expert on vertebrate traces Hartmut Haubold, now emeritus professor at the University of Halle, Germany. According to Haubold, these traces were produced by amphibians and can be assigned to the ichnospeciesBatrachichnus salamandroides. From the same borehole, another form was also found and was identified as Platytherium by Ágnes Barabásné Stuhl, who was at that time working as a palynologist with the Mecsek Ore Mining Company. Finding tetrapod footprints is not her only talent: she has also resolved fundamental stratigraphic questions relating to the Mecsek Mesozoic.
Majoros 1964; Kaszap 1968
Batrachichnus salamandroides (Geinitz 1861) Haubold 1996. Footprint of a small amphibian found 1,220 meters down borehole Turony-1. This species was formerly assigned to the genus Antichnium and is considered a good index fossil for the Lower Permian. The specimen was found by Ágnes Barabás-Stuhl, who worked as a palynologist with the Uranium of Pécs (Mecsek Ore Mining Company), and was identified by Hartmut Haubold, now emeritus professor at the University of Halle, Germany, and a recognized expert on fossil footprints.
FOSSILS FROM TRANSDANUBIA
Paleozoic sequences play only a subordinate role in the formation of the Transdanubian Central Range, as their outcrops are usually scattered and are situated far from one another. Indeed, some of these sequences are known only from borehole cores, and the oldest rocks of Lower Paleozoic age in this region were largely metamorphosed during orogenic movements. Some Lower Paleozoic metamorphic rocks are found along the northern shore of Lake Balaton as well as in its northeastern continuation in the Balatonfo area and in the Velence Hills. The western part of the Mecsek Mountains is formed largely from Permian rocks, although various Paleozoic successions have been explored by boreholes drilled in the neighborhood of these mountains. Although nearly all of these successions do contain fossils, most of these organic remains are purely of scientific interest.
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Excerpted from Fossils of the Carpathian Region by István Fozy, István Szente, Gareth Dyke. Copyright © 2014 István Fozy and István Szente. Excerpted by permission of Indiana University Press.
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