Quaternary research

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The Quaternary is systematically studies of the geological period of the Quaternary and recent geological period. This period is characterized by a series of glacial periods with extensive glaciations that alternate with relatively warm, interglacial periods, such as the present Holocene . Research into the Quaternary began in the late 18th century, although this branch of research did not establish itself together with paleontology until the 19th century . As in many other scientific disciplines, the early pioneers of Quaternary research also struggled to overcome entrenched ideas and dogmatic notions, which were based primarily on a literal interpretation of the Bible with the Flood as a real worldwide event. Modern Quaternary research is strongly interdisciplinary and integrates information from various sciences, such as paleoclimatology , geology , oceanography , but also from archeology or anthropology . The inclusion of these research areas in the evaluation of the Quaternary geological archives has contributed significantly to how recent geological history is interpreted today since the beginning of the 20th century.

History of Quaternary Research

Foundling Siebenschneiderstein on Rügen
Glacier scratches at the glacier gate of the Aletsch glacier

The term Quaternary was coined by the Italian mining engineer Giovanni Arduino (1714–1795). He distinguished four geological orders, which covered the entire history of the earth: primary, secondary, tertiary and quaternary . These four "layers", which seemed to lie on top of each other, manifested themselves differently in Italy from region to region. Arduino identified the mica schist of the Atesin Platform in the vicinity of the northern Italian cities of Bolzano and Trento as primary, the secondary as the fossil-rich deposits of the Southern Limestone Alps , the Tertiary as the fossil-rich sedimentary rocks of the valleys and the Quaternary with the gravel of the Po Valley . The term Quaternary was only used again in 1829 by the French geologist Jules Desnoyers to distinguish the tertiary from the younger deposits in the Paris Basin . The term Quaternary was described a short time later in 1833 by the French Henri Reboul to the effect that the Quaternary layers contain the most recent flora and fauna .

The geological period of the Quaternary is currently divided into the geochronological epochs of the Pleistocene and Holocene . The conceptual history of these time periods also turned out to be very lengthy. The name Pleistocene was coined in 1839 by the Scottish geologist Charles Lyell . Lyell defined the Pleistocene as the most recent geological era. When the theory of the formation of glaciers established itself, the Pleistocene of Edward Forbes was equated with the age of glaciers (Glacial epoch) in 1846 . Moriz Hoernes introduced the term Neogene in 1853 and thus formed the superordinate system to Lyell's Miocene and Pliocene . With reference to this, Lyell specified in 1873 that the term Pleistocene "strictly synonymous with post-Pliocene" ("strictly synonymous with Post-Pliocene") should be used. In the same publication, Lyell explicitly separated the Pleistocene ( glacial ) from the present ( postglacial ). Paul Gervais replaced the term present a short time later with Holocene .

As a result, the stratigraphic nomenclature of the Quaternary already existed at the end of the 19th century . However, at this point in time it was still unknown when the Tertiary ended and the Quaternary began. In geology, type localities are determined for this purpose , which form the boundaries between different stratigraphic units. During the 18th International Geological Congress in London in 1948 it was decided to find such a type locality for the Pliocene-Pleistocene (Tertiary-Quaternary) boundary. After almost three decades, such a stratigraphic reference profile was established at the locality Vrica in Calabria in 1985 and originally dated to around 1.64 million years. An exact age determination was only possible through the inclusion of radiometric dating methods, which have since formed a central part of Quaternary research.

The discovery of the Pleistocene inland glaciations

Schematic representation of the ice edge layers of the inland freezing in the north German lowlands:
  • Ice edge of the Vistula glaciation
  • Ice edge of the Saale Glaciation
  • Ice edge of the Elster Glaciation

    • The Pleistocene inland glaciations were one of geology's greatest mysteries, as it was beyond imagination that large parts of the flat land were covered by mighty ice sheets . Nothing comparable was known and therefore the actualistic principle prevailing in science was not applicable.

    The origin of the numerous boulders and debris in the north-central European plains was already known towards the end of the 18th century . For the erratic blocks in the area of ​​the Swiss Jura , which Horace-Bénédict de Saussure made generally known , their origin from the crystalline zone of the Alps was also established early on, but how did they get across the broad and up to 700 m deep basin of the Swiss plateau? The solution to the riddle was already close at hand in the early 1830s and reached by the mid-1840s at the latest. But the astute ideas of individuals and even clear evidence could not prevail for a long time against the resistance of the authorities. It therefore took almost 100 years from the discovery, or rather perception, of these striking phenomena to the largely undisputed acceptance of the inland theory.

    The trials and tribulations of the history of the discovery of inland freezing are traced predominantly on the basis of primary literature. The ideas of the proponents of the volcanism theory and the mud flood and roll tide theories went the furthest past reality because they were based on catastrophe theories, also disregarding the laws of mechanics .

    Volcanic theories

    Volcanic events were also used to determine the origin and transport of the erratic blocks until the mid-1840s . By Johann Silberschlag , were as he writes, in accordance with the biblical story of creation frequent in the North German Plain "Crater" ( dead ice holes and kettle holes returned) to "... outbreaks of subterranean forces." The debris ("field stones") piled up like a wall are said to be ejections from deeper layers. For the relocation of the erratic blocks to the Jura, Jean-André Deluc assumed large eruptions of gaseous liquids when underground caves collapsed.

    These ideas were taken up again more than 70 years later by Johann Georg Forchhammer and Ernst Boll , although the discussion about inland glaciation was well advanced.

    If this idea of ​​a volcanic explosive force without the escape of magma and such a large area effect was already quite absurd, it was exceeded by the assumption in the roll-flood and mud-flood theories that flowing water could move such large blocks in flat terrain.

    Mud flood and roll flood theories

    The idea already expressed by De Saussure that the displacement of the erratic blocks to be found in most of the Alpine valleys was caused by a large current was taken up by Leopold von Buch . Although his rough calculation showed that an unimaginable force would be required to transport the granite blocks from their area of ​​origin to the heights of the Jura through water, he only saw the possibility that these blocks were moved by a "... tremendous push". The boulders in the north-east German plains were also said to have "... flowed over the Baltic Sea" through a "... current in which violent shocks occurred". In the disaster of the glacial lake eruption on June 16, 1818 in Val de Bagnes , in which the up to 30 m high mud flood also carried large blocks of stone with it, he saw a confirmation of his theory.

    In a modification of this mud flood theory, a tidal flood theory was developed for the transport of boulders in the north-central European plains by the end of the 1830s, according to which a mysterious catastrophe occurred , disregarding all hydromechanical laws. The representatives were Gustav Adam Brückner and Nils Gabriel Sefström . The "furrows" ( glacier scratches) that are common on the rocks in Scandinavia are said to have been created by this "Petridelaunian scree flood". Georg Gottlieb Pusch characterized such a “rolling tide” most clearly when he writes on page 589: “... it should be regarded as a certainty that the great tide, which hurled the Nordic boulders over the once narrower Baltic Sea, came from the northeast must have gone to the southwest, and that a sudden breakthrough of great northern waters in this direction with a great, but probably not greater speed than it took place in our time when the alpine rivers that were dampened by glacier breaks, was quite possible, To hurl these northern rock debris at their current deposit, just as well as such breakthroughs in high alpine lakes threw the Uralpen blocks across flat Switzerland onto the heights of the Jura. "

    Drift theory

    British geologist Charles Lyell , one of the most influential geologists of the 19th century and proponent of drift theory

    The actualistic principle was more in line with the drift theory, as blocks of stone in the icebergs drifting south from Greenland were known early on. Already Johann Jakob Ferber and Georg Adolph von Winterfeld had intended to transport the large boulders of ice floes. But it was only Ernst Friedrich Wrede , one of the fathers of actualism, who demonstrated on the basis of observations and calculations that the boulders could only be transported through ice floes. In 1829, 35 years later, Karl Friedrich von Klöden took over the transport through ice floes for the boulders of the “southern Baltic plain”, but just 5 years later the result of his examination of the bed load led to the conclusion “... that the great geognostic phenomenon of bed load and blocks in the southern Baltic plain cannot be explained by a simple process, and that much more complex causes and forces must have contributed to it than was previously believed. With just as much evidence it turns out that we are further removed from the solution to the problem than was supposed to be, and that apparently the key to the great riddle has not yet been found, which is more unexplored than ever. "

    After Charles Lyell had toured northern Germany and Denmark in 1834, he published his drift theory in 1835, without going into detail about his predecessors, which he "... brought to general recognition by virtue of his authority". Although Leopold von Buch had already ruled out the transport of the erratic blocks through ice floes "... on the former inner sea of ​​Switzerland" to the Jura in 1815, the 1839 publication made such an assumption. In addition, the works by Jens Esmark (1824) and Albrecht Reinhard Bernhardi (1832) published in well-known magazines were not taken into account, see below. The drift theory also quickly found supporters and defenders among the leading German geologists, and this meant that recognition of the inland theory was delayed by 40 years. Charles Lyell stuck to the drift theory until the end, only for the Alps and Scotland could he be convinced to transport the boulders through glaciers.

    Mountain and inland glaciations

    The Swiss-American geologist Louis Agassiz , one of the most famous researchers of the Alpine glaciers

    As shown above, the erratic boulders were not enough to solve the riddle of inland glaciations. For this purpose, the glacier scrapes and glacier cuts had to be recognized in their significance as additional features . The route to this led in particular over the glaciers of the Alps.

    Deepest superstitions dominated the inhabitants of the Alps until the second half of the 18th century. It was reported that serious consideration was given to preventing the Grindelwald Glacier from advancing further in the years 1768 to 1770 with an expulsion of the devil. At the same time, Bernhard Friedrich Kuhn , one of the fathers of contemporaryism, founded glacier science. With strict application of the actualistic principle, he described the mechanism of the glaciers, the moraines and the glacier scrapes on the valley walls. He saw terminal moraine walls in the land used as evidence of earlier glacier advances, e.g. B. the powerful advance in 1600. With the evidence of old moraines , the search for the fluctuations in glaciation was initiated. These investigations were only continued by Ignaz Venetz , who attributed the fluctuations in glaciation to temperature changes. In 1829, Ignaz Venetz put forward the hypothesis at a conference of the General Swiss Society for All Natural Sciences that the erratic blocks in the Alps and the erratic boulders in northern Europe were the legacy of a large glaciation. This is said to have met with strict rejection, in particular by Leopold von Buch and Johann von Charpentier and that is probably also the reason that only a very short report appeared on the content of the lecture. As a result, it is not certain what evidence he presented for the Alps, and for the boulders of the north-central European plains it can only have been a bold vision. However, he is often referred to as the founder of the glaciation theory.

    Jens Esmark's observations could actually have been groundbreaking for the solution of the problem much earlier, who based on widespread large erratic blocks and smoothly ground rocks, for which he ruled out a fluvial cause for reasons of transport dynamics, concluded that the entire Scandinavian mountains was originally glaciated. For Albrecht Reinhard Bernhardi it was "... only one more step from there" to the assumption that the entire area of ​​distribution of the erratic boulders must have been glaciated. Although it was published in one of the most important magazines, this logical conclusion was completely ignored, and it probably also did not fit with the doctrine of the time . There was still no direct evidence of an influence of the ice sheet in the area where the erratic boulders spread, but this was the second time that the inland ice theory was founded.

    The proof that the Rhone glacier filled the entire valley widening of the Swiss plateau and that the erratic blocks reached the Jura was provided by Karl Friedrich Schimper by finding the glacier cut marks, which are unmistakable for the activity of glaciers, from Neuchâtel to Olten . As early as February 15, 1837, he had the proven great glaciation of the Alps and its consequences in the ode "The Ice Age", the term Ice Age is still in use today, presented in poetic form. Only a short excerpt was published from the extensive description that he had sent in a letter to Louis Agassiz , the President of the Swiss Natural Research Society , in preparation for the annual meeting in July 1837. Leaving out essential parts of the subject, Louis Agassiz took on the topic and developed his own Ice Age hypothesis in the opening speech in anticipation of his extensive presentation from 1840 and 1841 in German translation. He only mentioned KF Schimper briefly and left it out entirely in later publications. Agassiz spread his hypothesis with so much force that he was soon celebrated as the founder of the Ice Age theory . In the USA he is z. B. is still referred to today as its founder, although his hypothesis has proven to be wrong. As a result of his glacier studies, he postulated that before the uplift of the Alps, almost the entire northern hemisphere, in Europe from the polar region across the Mediterranean to the Atlas Mountains, was covered by an enormous "ice crust". The rising Alps are said to have pierced the ice and the boulders falling on the ice would have slid onto the Jura.

    Carl Friedrich Naumann, lithograph by Rudolf Hoffmann , 1857

    When Bernhard von Cotta toured the Alps in 1843 and Louis Agassiz also showed him the glacier cuts near Neuchâtel, the thought occurred to him whether erratic boulders also occur on the northern border of the area where erratic boulders are distributed in Germany. As he was unable to do so himself due to illness, he asked Carl Friedrich Naumann for an inspection and he found the characteristic glacier cuts and scrapes in several places on the porphyry rocks in the Hohburg Mountains near Wurzen . As a result of the assessment by the Swiss geologist Adolph von Morlot , who was just in Freiberg , he confirmed the unmistakability of the cut marks and deduced from this that there must have been a large inland ice glacier that reached from the north to the foothills of the Ore Mountains . With that the inland glaciation was proven beyond doubt. However, the resistance of the authorities prevented recognition and even the detailed description by CF Naumann in 1847 could not change that. It was not until later that Albert Heim interpreted the genesis of significantly deviating cut marks, which occur mainly on vertical rock faces and which he was not yet able to explain, as wind cuts.

    CF Naumann, who had obviously been convinced of the correctness of the inland theory throughout his life, made another attempt at the beginning of the 1870s to get it recognized and also showed the cut marks in the Hohburg Mountains to Charles Lyell. But Albert Heim, who traveled the Hohburg mountains alone, confirmed in the result of his investigation that the grinding marks were in no way caused by glaciers. This was also discovered during an excursion in 1874 and in 1875 Hermann Credner moved the southern border of the so-called “Diluvial Sea” further south.

    The lecture by Otto Martin Torell at the conference of the German Geological Society in November 1875 in Berlin finally brought about the breakthrough. The glacier cuts on the Muschelkalk of Rüdersdorf near Berlin that were observed on the excursion were a clear indication of inland glaciation and Otto Torell has since been celebrated as the founder of the inland ice theory. The spell was broken and by the beginning of the 1880s, drift theory had largely been overcome in German-speaking countries. So described z. B. in 1879 Hermann Credner glacier cuts on several mountain peaks of the northern Erzgebirge foothills , but without mentioning those on the Hohburger mountains and CF Naumann, and Albrecht Penck found at least three glaciations of the north German lowlands. For polyglacialism, the repeated glaciation, there were already findings much earlier. Ignaz Venetz had already suspected that the discovery of shale coal between two moraine banks was an indication of the repeated large glaciation of the Alps. Adolph von Morlot demonstrated that the Alps had glaciated at least twice in the 1850s. The research of the Alpine glaciations was put on a new basis by Albrecht Penck in 1882 and, together with Eduard Brückner, in the standard work Die Alpen im Eiszeit [The Alps in the Ice Age] , the names that are still valid today for the four youngest alpine cold ages Günz , Mindel , Riss and Würm were introduced. Konrad Keilhack and Jakob Stoller gave the three northern European glaciations, which were already known at that time, the still valid names Elster-Kaltzeit , Saale-Kaltzeit and Weichsel-Kaltzeit .

    Louis Agassiz's trip to Scotland in 1840 encouraged the early exploration of the Pleistocene glaciers of Scotland and Northern Ireland. The dominant drift theory hindered further progress, however, it could only be overcome by James Geikie .

    With the emigration of Louis Agassiz to the USA in 1846, research into the glaciation of North America began , but was also hindered by drift theory. Substantial advances were not made until the 1870s by James Geikie and Thomas Chrowder Chamberlin . In 1894, Thomas Chrowder Chamberlin introduced the name Wisconsin for the recent glaciation. For a long time it had been assumed that four glaciations in North America were compatible with those in Europe and the names Nebraskan glacial, Kansan glacial, Illinois glacial and Wisconsin glacial were used. The current structure is very different.

    The extinct Pleistocene mammals

    Reconstruction of woolly mammoth (left) and American mastodon (right)

    One of the branches of research that led to modern Quaternary research was vertebrate paleontology . In particular, the fossil remains of large mammals that died out in the Pleistocene aroused interest early on.

    The discovery of unusually large skeletal parts has always stimulated the imagination, until the end of the 18th century they were mostly associated with legends or the biblical flood. The pieces of bone found in 1577 at Reiden Monastery in Wiggertal ( Switzerland ) were said to come from a 6 m high giant , the "Giant of Reiden". Only in 1799 they were by Johann Friedrich Blumenbach as woolly mammoth ( Mammuthus primigenius ) and the family of elephants determined to belong. The fossil remains of the mammoth found in the Swiss plateau in the early 19th century initially served as the basis for the cataclysmic theory .

    Georges Cuvier , the proponent of the theory of cataclysm and the founder of paleontology

    According to the cataclysmic theory, particularly advocated by Georges Cuvier and originally derived from the ideas of mythological floods, it was assumed that life was almost completely wiped out in major catastrophes and could only develop again afterwards. Initially, a climate comparable to that of Africa was assumed for the layers of finds with the “elephants” , which changed due to a major catastrophe and led to sudden extinction. However, a closer examination of the layers of the found layers of the woolly mammoths, first known in 1806 and preserved in the frozen state in the permafrost soil of Siberia , showed that the animal was adapted to a cold climate.

    The discoverer of the American mastodon is Charles de Lougueuil, the commander of a French military expedition who visited the site in Big Bone Lick State Park on the Ohio River in Kentucky (USA) in 1739 . Nicholas Cresswell wrote a description of finds in 1775.

    After the US bought the central area of ​​North America, the Louisiana (colony) , from France in 1803 , then-President of the United States Thomas Jefferson sent explorers Meriwether Lewis and William Clark to explore and explore this new American area map. Thomas Jefferson was an avid naturalist, he showed great interest in the fossil bones of Big Bone Lick, and he may have anticipated the discovery of some living specimens of the mastodon as well as other large mammals.

    Excavation of the first American mastodon , painting by Charles Willson Peale , circa 1806

    Following the Lewis and Clark expedition , Thomas Jefferson commissioned William Clark with a comprehensive excavation campaign at the Big Bone Lick, which unearthed around 300 specimens of the most varied of fossils and formed a basis for research into the large Pleistocene mammals.

    Theories on the evolution of cold ages

    At the end of the 19th century, the fact of large-scale glaciation was generally accepted by science, but the causes and the exact duration of the glacial and interglacial phases remained unclear. It was only certain that the changing climatic conditions of recent geological history claimed many millennia. Several hypotheses have been developed to explain these cycles, such as changes in the atmospheric carbon dioxide concentration or periodic fluctuations in solar activity .

    Orbital theory by James Croll

    One of the earliest theories about the periodic change between glacial and interglacial comes from the Scottish naturalist James Croll (1821-1890). In correspondence with Charles Lyell , Croll described his idea of ​​the connection between glaciations and changes in orbital orbital elements . Lyell was impressed by this assumption and enabled Croll to join the Geological Survey of Scotland in 1867 . Here he was encouraged by the geologist Archibald Geikie to further develop his theory. Croll corresponded regularly with Charles Darwin at this time , from which both scientists benefited. Croll began to publish his theory in several treatises and works from 1867. His best known publications are Climate and Time, in their Geological Relations in 1875 and Climate and Cosmology in 1885.

    In 1846 the French astronomer Urbain Le Verrier published formulas for calculating orbital elements. Croll used this publication to reconstruct Earth's orbit ( eccentricity ) over the past three million years. He discovered that patterns of high eccentricity lasted for over a hundred thousand years and alternated with patterns of low eccentricity, as they were at the time of his calculations. The more the orbit deviated from a circular shape , the greater the difference in solar radiation in the seasonal change. Croll understood the importance of the seasonality of solar irradiation and thus achieved one of the most important gains in paleoclimatology . Changes in the Earth's orbit led to an extension of winter, so that larger amounts of snow fell in the high latitudes. A more extensive snow cover reflects more solar radiation and thus intensifies the orbital effects ( ice-albedo feedback ). Croll saw in this reinforcement the trigger for the growth of ice sheets. Croll's theory was of great importance for climatology , but subsequent investigations also showed clear shortcomings. The occurrence of the Pleistocene glaciations could not be adequately represented on this basis, and on the other hand, Croll's chronology of the glaciations was incorrect. Above all, he classified the youngest glacial phase much older than the geological investigations by James Geikie (the younger brother of Archibald Geikie ) and others showed. Croll failed to convince the majority of his contemporary colleagues, and as a result his ideas were largely ignored until the 1940s.

    Milanković cycles

    Diagram of the Milankovitch cycles including an overview of
    precession (precession) ,
    obliquity of the ecliptic (obliquity) ,
    eccentricity (excentricity) ,
    fluctuations of solar radiation on the earth (solar forcing) and the cold and warm periods (Stages of Glaciation)

    Milutin Milanković (1879-1958) was a Yugoslav mathematician who specialized in geophysics and astronomy. In 1909 he became a member of the Faculty of Applied Mathematics at the University of Belgrade . Due to his imprisonment by Austria-Hungary during the First World War , he was only able to continue his research on the mathematical theory of climate change - based on earlier work by Joseph-Alphonse Adhémar and James Croll - in 1920 and complete it in 1941. However, Adhémar explained the glacial climate exclusively through precession , while Milanković considered the cyclical changes of the three orbit elements of the earth's orbit around the sun: eccentricity , ecliptic and precession. On the basis of these orbital parameters, he developed a comprehensive mathematical model in order to calculate the dependence of solar irradiation on geographical latitude and the associated surface temperatures over the past 600,000 years.

    His next step was to try to correlate the changing orbital parameters with the glacial-interglacial cycles. In collaboration with the German climatologist Wladimir Köppen , Milanković assumed that fluctuations in irradiation in certain latitudes and seasons are able to intensify or weaken glaciation processes. For decades, this approach met with little response from experts and was largely regarded as speculative. It was not until 1976 that the geologist James Hays published an interdisciplinary study on deep-sea sediment cores . In it, Hays and his research colleagues postulated a high degree of agreement with Milanković's predictions in connection with the timing and intensity of changed climatic conditions over the past 450,000 years. The study showed that significant climatic changes are closely linked to the orbital parameters eccentricity, ecliptic and precession. These orbital changes are known today as Milanković cycles .

    However, there were several climate change events during the Quaternary, which apparently did not correlate with all astronomical parameters, but only matched a single cycle, including a "jump" from the 40,000-year cycle (inclination angle of the earth's axis) to the 100,000 years Cycle (change in eccentricity) has been demonstrated. A study published in 2019 postulates a significant weakening of the deep water circulation, especially in the subpolar regions of the southern ocean, as the main cause of this change. As a result of these processes, significantly less carbon dioxide from the deep sea reached the sea surface and from there into the atmosphere, which led to an extension of the cold-age conditions.

    Since the 1980s, the Milanković cycles in modified and expanded form have been an integral part of paleoclimatology and Quaternary research and are often used to reconstruct the ice age phases.

    Quaternary research analysis tools

    Dating methods

    Without an absolute age determination , for example, it would hardly have been possible to check the various components of the Milanković cycles for their climatic relevance. Until the second half of the 20th century, Quaternary research could not make any well-founded statements about the exact chronological sequence or the duration of the various cold and warm periods. The chronology of Quaternary events was determined exclusively by relative dating methods and was limited to a sequence of events that were assigned to a specific stratigraphic profile on the basis of fossil finds . However, it inevitably remained open whether a geological event was 50,000 or 150,000 years ago.

    Uranium decay series

    The development of radiometric dating not only revolutionized Quaternary research, but also led to the establishment of the subdisciplines geochronology and chronostratigraphy and thus acquired great importance for all periods of the 541 million years long Phanerozoic and beyond. The beginnings of this analytical method go back to the year 1902 when the physicists Ernest Rutherford and Frederick Soddy discovered the decay series of radioactive elements. The possibility of a practical use for age dating was first mentioned by Rutherford in 1904. Two years later, Rutherford began calculating the radioactive decay of the element uranium . In the process, nuclides with different half-lives are formed and, based on them, further decay series are formed. This results from the parent isotope 234 U different daughter isotopes such as thorium isotope 230 means Th. The decay chains of uranium and it became possible to use the numerical age of igneous rocks and volcanogenic sediments to determine the expelled millions of years ago by eruptive processes and had been deposited. Indirect could thus also the age of adjacent fossil defined leading sedimentary rocks and thus the geological time scale to be provided with numerical age data. Methods currently in use are uranium-thorium dating or uranium-lead dating . In order to achieve the most accurate results possible, zirconium crystals are often used. Due to their heat resistance and their lattice structure, which has remained stable as a result, these are suitable for the precise analysis of the radioactive nuclides enclosed therein (such as 235 U, 238 U or 232 Th).

    Radiocarbon dating

    Probably the most important contribution to the dating of Quaternary fossils and sediments was made by the discovery of the radiocarbon method (also known as the 14 C method). In 1940, the physicists Martin Kamen and Sam Ruben discovered the long-lived radioactive carbon isotope 14 C. Kamen used 14 C as a tracer in biological systems and found that under the influence of cosmic rays the nitrogen isotope 14 N in the atmosphere becomes 14 C. is converted. The existence of the carbon isotope 14 C was postulated as early as 1934, but it could not initially be observed or characterized. Kamen was the first to succeed in determining the half-life of 14 C to be around 5,730 years.

    Based on Kamen's discoveries, chemist Willard Libby found in 1947 that plants absorb traces of 14 C during their carbon uptake during photosynthesis . After they die, the absorption of carbon ceases and the 14 C it contains decomposes at its usual rate without being replaced. In 1952, Libby finally discovered that the time of death could be determined by measuring the remaining 14 C concentration in the plant remains. In addition, concentrations of 14 C were also found in the tissues of animals because they had ingested plant material either directly or indirectly through their diet. Radiocarbon dating enables an absolute age determination of fossil animal or plant finds from the last 50,000 years, but only covers a relatively small area of ​​the Quaternary. In addition, the cycles of solar activity, changes in the geomagnetic dipole field and the exchange between carbon sinks and the atmosphere can be calculated from the natural fluctuations of the 14 C isotope and the stable carbon isotope 12 C. For the discovery of radiocarbon dating, Willard Libby received the Nobel Prize in Chemistry in 1960 . The increasing anthropogenic CO 2 emissions are currently leading to a significant reduction in the 14 C content in the atmosphere. This effect will likely make future radiocarbon dating considerably more difficult or significantly falsify it.

    Luminescence dating

    Luminescence dating is a physical determination of the age for quaternary sediments. This method is based on radiation damage that increases with age , which is quantified by the emitted luminescence . Within this form of age determination, a distinction is made between thermoluminescence dating (TL) and optically stimulated luminescence (OSL) depending on the stimulation energy used . The TL method has its origins in the 1950s and was first used to date fired pottery. The OSL method is particularly important in Quaternary research. It is based on the principle that if there is sufficient light exposure (e.g. sunlight) the entire luminescence signal is reset. This means that in contrast to surface exposure dating, the age of the sedimentation can be determined. OSL dating was developed in the mid-1980s. Luminescence dating has made a significant contribution to quaternary research, as it was the first time it was possible to date individual mineral grains and not just organic components (as in radiocarbon dating). Luminescence dating covers a measurement range from a few centuries to around 150,000 years.

    Atom Trap Trace Analysis

    The crypto-dating using the isotope 81 Cr in conjunction with the stable isotope 83 Kr is used in practice since 2011 on. The breakthrough came with a new detector technology based on Atom Trap Trace Analysis (ATTA) . With a half-life of 230,000 years, 81 Kr within the Quaternary time frame is particularly suitable for examining glaciers and old ice layers, such as those found on Greenland and in the Antarctic, and provides considerably more precise results than conventional dating methods. Another area of ​​application of this method is the detection of the argon isotope 39 Ar , which is currently still in its infancy, for the analysis of glacial ice and oceanic deep water. The Atom Trap Trace Analysis is a magneto-optical " atom trap " (MOT) using laser physics for trace analysis of rare noble gas isotopes. Each atom of the sample material is counted individually, for example, there is only one 39 Ar isotope for every quadrillion argon atoms .

    Standard proxies

    In order to be able to make well-founded statements about the climate , environmental conditions and geophysical events of earlier epochs, Quaternary research has a large number of special measurement and determination methods. The standard instrumentation includes climate proxies that can be found in natural archives such as tree rings , stalactites , ice cores , corals , sea or ocean sediments . These are not only used to reconstruct cold and warm periods, but also provide information on solar activity, precipitation intensity and air composition. In order to rule out incorrect results as far as possible, climate proxies must be compared with modern, instrumentally determined data series and calibrated on them. Below are a number of proxies that are fundamental to Quaternary research.

    Hollow drill for taking dendrochronological samples, including two drill cores
    • With the dendrochronology , the annual tree growth can be reconstructed depending on the weather, the environment and the climate by analyzing the annual rings. For individual European tree species, complete annual ring tables were created over a period of 10,000 years. The current “record holder” is the Hohenheim tree ring calendar , on which central European climate developments can be traced back from the present to the Younger Dryas period .
    • The palynology (pollen analysis) under the name Pollenstratigraphie a portion of the paleontology and has been in the Quaternary and paleoclimatology also gained in importance. Thanks to its global distribution and great resistance to environmental influences and geological processes, primeval own pollen , spores and microfossils to the geological present as index fossils . In addition, complex ecosystems can also be reconstructed based on the local frequency and species diversity of pollen .
    • The varven chronology , also called band tone dating , is based on the exact counting of deposit layers (varves) in still and flowing waters such as lakes or rivers. If the count can be integrated into an absolute time frame, this enables the age to be specified in varve years . The scope of the varven chronology extends over a time frame of several hundred to about 30,000 years and in individual cases extends beyond this.
    • Ice cores are among the most accurate climate archives and are therefore very methodically analyzed and evaluated. In addition to mountain glaciers, whose drill cores can be used to reconstruct regional climatic processes over the past millennia under favorable conditions, the Greenland and Antarctic ice sheets are suitable for detailed analyzes over longer periods of time. While the oldest Greenland ice examined so far covers around 123,000 years and thus includes the Eem warm period ,an Antarctic core with a total age of over 800,000 years was recovered aspart of the EPICA project. The “fossil” air bubbles within an ice core are archives for the composition of the atmosphere and especially for the carbon dioxide and methane concentrations, which, coupled with the cold and warm phases of an ice age cycle, were subject to strong fluctuations and together with the Milanković cycles form an essential climate factor. Ice cores also provide data on solar activity, air temperatures, evaporation and condensation processes, and anomalies in the earth's magnetic field.
    • Oceanic sediments . Thelayers of deposits formedover long periods of time on the continental shelves or in the deep sea are divided into biogenic, lithogenic and hydrogen sediments. Depending on the origin, the drill core samples allow conclusions to be drawn about the geographical distribution of living beings, changes in the state of ocean currents or past climatic fluctuations. The exact dating of oceanic drill core samples usually varies greatly and is dependent on their age and the speed of the respective sedimentation processes. Deposits from the Holocene allow, under favorable conditions, a temporal resolution of a few decades.
    • Dripstones such as stalagmites and stalactites occur worldwide and are almost inevitably to be found in the caves of karst and limestone areas. Stalactites arise from surface water enriched with carbon dioxide, which absorbs organic acids on its way through crevices and porous material, which in combination with the carbon dioxidedissolve the calcium carbonate contained in the rock. The ratio of the oxygen isotopes in the limestone, the thickness of the growth layers and the proportions of various trace elements add up to an environmental archive accurate to decades, which alsorecordsabrupt and brief changes such as the Dansgaard-Oeschger events of the last glacial period. Dripstones can - depending on the duration of the water and thus the calcium carbonate supply - grow for a very long time and sometimes reach an age of several hundred thousand years.
    • The paleothermometer δ 18 O (Delta-O-18), with which the temperatures during the Cenozoic era were measured for the first time in the 1970s , is based on the ratio of the stable oxygen isotopes 18 O and 16 O. This versatile method is suitable for the reconstruction of precipitation temperatures and also serves as an indicator of processes of isotope fractionation such as methanogenesis . In Quaternary research, 18 O / 16 O data are used as a temperature proxy for fossil foraminifera , ice cores, dripstones and freshwater sediments, among other things .

    Current Quaternary Research

    Models for the future development of global warming are based on reconstructed temperature data from the past.

    Quaternary research is a strongly interdisciplinary research field that deals with environmental changes over the past 2.6 million years (the period of the Quaternary). The aim of the quaternary researchers is to evaluate the geological archives of this time in order to record those key factors that trigger and control processes of change on different spatial and temporal scales. The key factors can be of physical, chemical, biological, atmospheric or anthropogenic origin. This broad spectrum of research requires a comprehensive exchange of information between numerous scientific and technical disciplines. For example, the basis of accurate age dating was only created through the developments in atomic physics in the early 20th century. Gains in knowledge in evolutionary biology or precise analysis options for biomolecules made it possible to improve the interpretation of quaternary fossil finds. Innovations in engineering after the end of the Second World War meant that drill cores such as EPICA , GISP and GRIP could be extracted from oceanic sediments or from the Greenland and Antarctic ice sheets. These drill cores also provided new information on the earth's climate sensitivity . After analyzing the last 784,000 years with eight complete warm-and-cold cycles, the authors of a study published in 2016 come to the conclusion that climate sensitivity is highly temperature-dependent. According to this, the climate sensitivity during a cold period such as the Würm or Vistula glacial is around 2 ° C and increases by almost double under warm period conditions.

    The evaluation of the Quaternary geological archives has contributed significantly to how recent geological history is interpreted today since the beginning of the 20th century. The instruments for analyzing these geological conditions grew steadily and enabled reconstructions with a temporal resolution that was unthinkable just a few decades ago (especially with regard to sudden climate change events ).

    During the Quaternary, the earth had essentially already assumed its present physical appearance in terms of the size and distribution of continents and mountains, ocean currents , the composition of the earth's atmosphere or large biomes . However, the geological archives also revealed that the terrestrial climate system had changed often and in some cases significantly. In the course of the Quaternary, modern man emerged, which gradually became the dominant influencing factor on the terrestrial biosphere in the course of its worldwide expansion .

    The fact of current climate change combined with other factors such as the extinction of species, acidification of the oceans or the reduction of natural biotopes led to the design of the Anthropocene ( ancient Greek : the man-made new ), which according to the ideas of British geologists and the Dutch Nobel Prize winner for chemistry, Paul J. Crutzen , as the most recent period to be implemented in the chronostratigraphic system of earth's history. At the 35th International Geological Congress in Cape Town in 2016, the working group on the Anthropocene formed in 2009 followed this position, with 1950 being the preferred starting point for the new epoch. In May 2019, a majority of this committee decided to submit a draft for the introduction of the Anthropocene to the International Commission on Stratigraphy by 2021 . Until then, a geologically defined starting point for the new epoch should be established.

    Quaternary researchers integrate information from various natural sciences such as climatology , ecology , geology , physical geography or oceanography , but also from human sciences such as archeology or anthropology . Behind this stands the need for an inter- and multidisciplinary approach to understanding the Earth system and includes the challenge of recognizing and limiting the potential dangers of global environmental changes. The German Quaternary researcher Paul Woldstedt already noted in 1951 that Quaternary research contributes “to an understanding of the present and our position in it”.

    See also

    literature

    Reference works and overviews

    • Scott Elias and Cary Mock (Eds.): Encyclopedia of Quaternary Science . 2nd Edition. Elsevier, 2013, ISBN 978-0-444-53643-3 (important reference work on the subject, the first chapters deal with the development of Quaternary research itself).
    • Vivien Gornitz (Ed.): Encyclopedia of Paleoclimatology and Ancient Environments (=  Encyclopedia of Earth Sciences Series ). 2009, ISBN 978-1-4020-4551-6 , sections Glaciations, Quarternary et al
    • Mike Walker: Quaternary Science 2007: a Fifty-Year Retrospective . In: Journal of the Geological Society . December 2007, doi : 10.1144 / 0016-76492006-195 (overview of the research history since the middle of the 20th century).

    Introductions

    German speaking

    • Jürgen Ehlers : The Ice Age . Spectrum Academic Publishing House, 2011, ISBN 978-3-8274-2327-6 (introductory work aimed at a wide audience).
    • Karl N. Thome: Introduction to the Quaternary: The Age of Glaciers . 2nd Edition. Springer, 2013, ISBN 978-3-642-58744-3 (unchanged new edition of the 1999 edition, only includes literature up to the beginning of the 1990s).
    • Albert Schreiner : Introduction to Quaternary Geology . 2nd Edition. Swiss beard, 1997, ISBN 3-510-65177-4 .
    • Jürgen Ehlers: General and historical Quaternary geology . Enke, 1994, ISBN 3-432-25911-5 .

    English speaking

    • J. John Lowe and Michael JC Walker: Reconstructing Quaternary Environments . 3. Edition. Routledge, 2014, ISBN 978-1-317-75371-1 (strongly method-oriented introduction and overview).
    • Neil Roberts: The Holocene: An Environmental History . Wiley, 2014, ISBN 978-1-4051-5521-2 (introduction for undergraduate students focusing on the Holocene, including chapters on methodology and the Pleistocene).
    • Raymond S. Bradley : Paleoclimatology. Reconstructing Climates of the Quaternary (=  International geophysics series . Volume 68 ). 3. Edition. Academic Press, 2013, ISBN 978-0-12-386995-1 (emphasis on overview of paleoclimatic methods, frequently cited work for advanced students and for researchers, won a Textbook Excellence Award (“Texty”) in 2015 ).
    • William F. Ruddiman : Earth's Climate: Past and Future . WH Freeman, 2008, ISBN 978-0-7167-8490-6 (Introduction to the history of climate, often cited, parts III and IV are particularly relevant for the Quaternary).
    • Harry John Betteley Birks and Hilary H. Birks: Quaternary Palaeoecology . Blackburn Press, 2004, ISBN 1-930665-56-3 (Introduction to Quaternary Paleoecology , Chapter 1 and Chapter 2 online).

    Method-oriented literature

    • Mike Walker: Quaternary Dating Methods: An Introduction . Wiley, 2013, ISBN 978-1-118-70009-9 (frequently cited introductory work on dating methods).
    • Jay Stratton Noller, Janet M. Sowers, and William R. Lettis: Quaternary Geochronology: Methods and Applications . Wiley, 2000, ISBN 0-87590-950-7 .

    history

    • Rodney H. Grapes, David Oldroyd , Algimantas Grigelis (Eds.): History of Geomorphology and Quarternary Geology , Geological Society of London Special Publication 301, 2008.
    • Norman Henniges: The track of the ice: a praxeological study of the scientific beginnings of the geologist and geographer Albrecht Penck (1858-1945). Contributions to regional geography. Volume 69, Leibniz Institute f. Regional studies, Leipzig 2017, ISBN 978-3-86082-097-1 , 556 pp. (Online)
    • Tobias Krüger: The Discovery of the Ice Ages - International Reception and Consequences for Understanding Climate History. Schwabe-Verlag, Basel 2008, ISBN 978-3-7965-2439-4 .
    • Otfried Wagenbreth : History of the geology in Germany . Springer Spectrum 1999, 2015.

    Scientific journals

    Individual evidence

    1. ^ A b S. A. Elias: History of Quaternary Science. In: Encyclopedia of Quaternary Science. Elsevier, 2006, ISBN 0-444-51919-X , p. 11. ( PDF of the second edition, 2013)
    2. ↑ M. Allaby: Earth Science: A History of the scientific Solid Earth. Facts On File, 2009, ISBN 978-0-8160-6097-9 , p. 127.
    3. ↑ J. Desnoyers: Observations sur un ensemble de dépôts marins plus recents que les terrains tertiaries du bassin de la Seine, et constituant une formation geologique distincte; precedees d'une aperçu de la non-simulaneite des bassins tertiares. In: Annals Sciences Naturelles (Paris). 16, 1829, pp. 171-214, pp. 402-491.
    4. ^ Henri Reboul: Géologie de la période Quaternaire et introduction a l'histoire ancienne. FG Levrault, Paris 1833, pp. 1-2. (Digitized version)
    5. ^ F. Gradstein, J. Ogg, M. Schmitz, G. Ogg: The Geologic Time Scale 2012. Elsevier, 2012, ISBN 978-0-444-59425-9 , p. 411.
    6. ^ E. Forbes: On the connection between the distribution of existing fauna and flora of the British Isles, and the geological changes which have affected their area, especially during the epoch of the Northern Drift. In: Great Britain Geological Survey Memoir. 1, 1846, pp. 336-342.
    7. ↑ M. Hörnes: Communication addressed to Prof. Bronn. Vienna, October 3rd, 1853. New yearbook Mineralogie Geologie Geognosie und Petrefaktenkunde 1853, pp. 806–810.
    8. ^ E. Aguirre, G. Pasini: The Pliocene – Pleistocene boundary. In: Episodes. 8, 1985, pp. 116-120.
    9. ^ MG Bassett: Towards a 'common language' in stratigraphy. In: Episodes. 8, 1985, pp. 87-92.
    10. ↑ a b Georg Adolph von Winterfeld: From the fatherland of the Mecklenburg granite rock. In: Monthly by and for Mecklenburg. Volume 3. Schwerin 1790. pp. 475–478. [1]
    11. ↑ Von Arenswald: History of the Pomeranian and Mecklenburg Petrifications. In: The natural scientist. 5 pieces. Halle (Gebauer) 1775. pp. 145–168. [2]
    12. ↑ a b Horace-Bénedict de Saussure: Voyages dans les Alpes précédés d'un essai sur l'histoire naturell des environs de Geneve. Volume 1. Neuchâtel 1779. S. XXXVI, 1-540. [3]
    13. ↑ Johann Esaias Silberschlag: Geogeny or explanation of the Mosaic creation of the earth according to physical and mathematical principles. 1st chapter. Berlin (Verlag Buchhandlung Realschule) 1780. S. X, 1–194. [4]
    14. ^ Jean-André de Luc: Lettres physiques et morales sur les montagnes et sur l'histoire de la terre et de l'homme. En Suisse (Chez Les Libraires Associés) 1778. pp. XXIV, 1-224. [5]
    15. ↑ Johann Georg Forchhammer: About bed load formations and diluvial scratches in Denmark and a part of Sweden. In: Poggendorff's annals of physics and chemistry. Volume 58. Leipzig 1843. pp. 609-646. [6]
    16. ↑ Ernst Boll: Geognosy of the German Baltic Sea countries between Eider and Oder. Neubrandenburg (Brünslow) 1846, p. VI, 1–285. [7]
    17. ↑ Leopold von Buch: About the causes of the spread of large alpine debris. In: Treatises of the physical class of the Royal Prussian Academy of Sciences from the years 1804-1811. Berlin (Realschul-Buchhandlung) 1815. pp. 161–186. [8th]
    18. ↑ Stefan Berchtold, Peter Bumann: memorial Ignaz Venetz 1788-1859 - engineer and natural scientist. In: Messages from the Natural Research Society of Upper Valais. Volume 1, Brig (Rotten-Verlag) 1990. pp. 1-144. [9]
    19. ↑ Leopold von Buch: About the distribution of large alpine debris. In: Poggendorff's annals of physics and chemistry. Volume 9. Leipzig (Barth) 1827. pp. 575-588. [10]
    20. ↑ Gustav Adam Brückner: How is the land and soil of Mecklenburg layered and created? Neustrelitz / Neubrandenburg (Dümmler) 1825. P. VIII, 1–192. [11]
    21. ↑ Nils Gabriel Sefström: About the traces of a very great primeval flood. In: Poggendorff's annals of physics and chemistry. Volume 38 No. 8. Leipzig (Barth) 1836. pp. 614-618. [12]
    22. ↑ Nils Gabriel Sefström: Investigation of the furrows present on the rocks of Scandinavia in a certain direction and their probable formation. In: Poggendorff's annals of physics and chemistry. Volume 43. Leipzig (Barth) 1838. pp. 533-567. [13]
    23. ↑ Georg Gottlieb Pusch: Geognostic description of Poland, as well as the rest of the North Carpathian countries. Part 2. Stuttgart / Tübingen (Cotta) 1836. S. XII, 1-695
    24. ^ Johann Jakob Ferber: Notes on the physical description of the earth from Kurland. Riga (Hartknoch) 1784. pp. XIV, 1–196. [14]
    25. ^ Ernst Georg Friedrich Wrede: Geological results from observations over part of the southern Baltic countries. Halle (Renger) 1794. S. XII, 1-204. [15]
    26. ↑ Karl Friedrich Klöden: About the shape and the prehistory of the earth together with the phenomena that depend on it in astronomical, geognostic, geographical and physical terms. Berlin (Nauck's Buchhandlung) 1829. S. XXVIII, 1–384. [16]
    27. ^ Karl Friedrich Klöden: The fossils of the Mark Brandenburg, which can be found in the pebbles and blocks of the southern Baltic plain. Berlin (Lüderitz) 1834. S. X, 1–378. [17]
    28. ^ Charles Lyell: Principles of Geology: Being an Inquiry how far the Former Changes of the Earth's Surface. Vol. I. London 1835. pp. XVIII, 1-441. [18]
    29. ↑ a b Werner Schulz: The development of the inland ice theory in the southern Baltic region. In: Journal of Geological Sciences. Volume 3, Issue 8. Berlin 1975. pp. 1023-1035
    30. ^ Carl Lyell: Elements of Geology (from the English by Carl Hartmann). Weimar (Voigt) 1839. pp. 114–119. [19]
    31. ↑ Charles Lyell: The age of the human race on earth and the origin of the species by modification along with a description of the ice age in Europe and America (Authorized German translation of the original from 1873 by Ludwig Büchner). Leipzig (Theodor Thomas) 1874. S. X, 1-519. [20]
    32. ^ Johann Albrecht Höpfner: Something about the moral and domestic condition of the inhabitants of the Grindelwaldthales and Oberland. In: Swiss Museum. Volume 2, issue 9. Zurich 1785. pp. 769–787. [21]
    33. ^ Bernhard Friedrich Kuhn: Attempt on the mechanism of the glacier. In: Magazine for the natural history of Helvetia. Volume 1. Zurich (Orell, Geßner, Füßli and Company) 1787. pp. 117-136. [22]
    34. ↑ Bernhard Friedrich Kuhn: Addendum to the experiment on the mechanism of glaciers in the first volume of this magazine. In: Magazine for the natural history of Helvetia. Volume 3. Zurich (Orell, Geßner, Füßli and Company) 1788. pp. 427-436. [23]
    35. ↑ Ignaz Venetz: Mémoire sur les variations de la temperature dans les Alpes de la Suisse (lecture from 1821). In: Memoranda of the general Swiss society for the entire natural sciences. 1st volume, 2nd section. Zurich (Orell, Füssli & Compagnie) 1833. pp. 1–38. [24]
    36. ↑ Ignaz Venetz: About the changes in temperature in the Swiss Alps. In: Stefan Berchhold, Peter Bumann (ed.): Commemorative publication Ignaz Venetz 1788-1859 - engineer and natural scientist. Brig (Rotten-Verlag) 1990. pp. 125-143. [25]
    37. ↑ Stefan Berchhold, Peter Bumann (ed.): Commemorative publication Ignaz Venetz 1788-1859 - engineer and natural scientist. Brig (Rotten-Verlag) 1990. p. 101
    38. ↑ Ignaz Venetz: Sur l'ancienne extension des glaciers et sur leur retraite dans leur limites actuelles. In: Actes de la Société Helvétique des Sciences naturelles. Quinzième Réunion annuelle à l'Hospice du Grand-Saint-Bernard, les 21, 22 et 23 juillet 1829. Lausanne 1830. p. 31. [26]
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