Stable isotope composition of crocodilian teeth provides new information on climatic change in the East-African Rift along the Plio-Pleistocene period (Shungura Formation, Lower Omo Valley Ethiopia) 

2021 ◽  
Author(s):  
Axelle Gardin ◽  
Emmanuelle Pucéat ◽  
Géraldine Garcia ◽  
Jean-Renaud Boisserie ◽  
Olga Otero
Keyword(s):  
Isotopic Composition ◽  
Environmental Changes ◽  
Tooth Enamel ◽  
Isotope Composition ◽  
Eastern Africa ◽  
East African ◽  
New Information ◽  
Major Shift ◽  
African Rift ◽  
Available Information

<p><span xml:lang="EN-GB"><span>I<span xml:lang="EN-GB"><span>sotopic fluctuation of certain stable isotopes, notably Oxygen, provide important information on paleoenvironmental change along geological times. However, interpreting isotopic change along continental series depends on our ability to understand its recording, for instance in soils or in mammal teeth. In the case of continental series yielding most of available information on hominid diversification and expansion within and beyond Africa, isotopic information even seems to show discrepancies depending on the archive. In our study, we use isotopic composition in crocodilian tooth enamel. We assume that, for these ectotherms that regulate their temperature, isotopic composition recorded in their teeth mainly depends on drinking water, itself depending on precipitation. Moreover, crocodilian fossil teeth are abundant and widely distributed within continental series, thus constituting an interesting archive. We sampled crocodilian teeth from the </span></span><span xml:lang="EN-GB"><span>Shungura</span></span><span xml:lang="EN-GB"><span> Formation (Lower Omo Valley, Ethiopia), which spans major steps of human evolution between 3.6 Ma and ~1.0 Ma, tentatively correlated with major environmental changes in eastern Africa (intensification of seasonal contrasts, increasing aridity and landscape opening). The analyses of δ</span></span><sup><span xml:lang="EN-GB"><span>18</span></span></sup><span xml:lang="EN-GB"><span>O of hundreds of crocodilian teeth have identified environmental changes. Whereas the isotopic composition of paedogenic carbonates displays a different trend over time, that of crocodilian teeth relates changes already observed in mammal teeth, notably a major shift between 2.6 Ma and 2.3 Ma toward more arid conditions. Our study indicates that crocodilian teeth are a relevant archive of environmental change in continental contexts, and calls for further study to strengthen interpretations of isotopic composition in fossil archives.</span></span><span> </span></span></span></p>

Herbivore paleodiet and paleoenvironmental changes in Chad during the Pliocene using stable isotope ratios of tooth enamel carbonate

Paleobiology ◽  
2000 ◽  
Vol 26 (2) ◽  
pp. 294-309 ◽  
Author(s):  
Antoine Zazzo ◽  
Hervé Bocherens ◽  
Daniel Billiou ◽  
André Mariotti ◽  
Michel Brunet ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Environmental Changes ◽  
Tooth Enamel ◽  
Isotope Composition ◽  
Plant Cover ◽  
Carbon Isotope Composition ◽  
Dental Morphology ◽  
Early Hominid ◽  
Carbon And Oxygen Isotope

Chad is a key region for understanding early hominid geographic expansion in relation to late Miocene and Pliocene environmental changes, owing to its location 2500 km west from the Rift Valley and to the occurrence of sites ranging in age from about 6 to 3 Ma, some of which yield fossil hominids. To reconstruct changes in herbivore paleodiet and therefore changes in the paleoenvironment, we measured the carbon and oxygen isotope composition of 80 tooth-enamel samples from three time horizons for nine families of Perissodactyla, Proboscidea, and Artiodactyla. The absence of significant alteration of in vivo isotopic signatures can be determined for carbon, thus allowing paleodietary and paleoenvironmental interpretations to be made.While the results generally confirm previous dietary hypotheses, mostly based on relative crown height, there are some notable surprises. The main discrepancies are found among low-crowned proboscideans (e.g., Anancus) and high-crowned rhinocerotids (Ceratotherium). Both species were more opportunistic feeders than it is usually believed. This result confirms that ancient feeding ecology cannot always be inferred from dental morphology or extant relatives.There is an increase in the average carbon isotope composition of tooth enamel from the oldest unit to the youngest, suggesting that the environment became richer in C4 plants with time. In turn, more C4 plants indicate an opening of the plant cover during this period. This increase in carbon isotope composition is also recorded within genera such as Nyanzachoerus, Ceratotherium, and Hexaprotodon, indicating a change from a C3-dominated to a C4-dominated diet over time. It appears that, unlike other middle Pliocene hominid sites in eastern and southern Africa, this part of Chad was characterized by very open conditions and that savanna-like grasslands were already dominant when hominids were present in the area.

The Aquatic Civilization of Middle Africa

1974 ◽  
Vol 15 (4) ◽  
pp. 527-546 ◽  
Author(s):  
J. E. G. Sutton
Keyword(s):  
Lake Victoria ◽  
Eastern Africa ◽  
Cultural Tradition ◽  
Main Stage ◽  
African Culture ◽  
Way Of Life ◽  
East African ◽  
Aquatic Life ◽  
Kenya Rift ◽  
African Rift

Between the ninth and third millennia B.C. wetter conditions prevailed over most of Africa. Lakes and rivers were fuller and some of the internal basins were temporarily linked, especially in the ‘Middle African’ belt. This comprises the southern Sahara and Sahel, stretching from the Upper Niger to the Middle Nile, with a south-easterly extension into the Upper Nile basin and the East African rift valleys. This situation was exploited by people who developed a decidedly aquatic economy and culture. From their waterside camps and settlements archaeologists have recovered bones of fish and aquatic animals which these people ate, as well as the distinctive harpoon-heads carved from bone with which they obtained them, and also pottery, bearing peculiar decoration executed with fish-bones and water-shells, made in imitation of (fishing-) baskets. Boating and other cultural developments are deducible. The harpoons date back to 7,000 b.c. at least; the pottery dates back to more than 6,000 b.c. and was clearly an African invention. It reflects important developments in gastronomy and home life.In the Kenya rift valley the main stage of Leakey's ‘Kenya Capsian’ culture is essentially the local manifestation of this far-flung ‘aquatic civilization’.Its greatest extent was achieved during the wettest times of the seventh millennium b.c., and probably involved the expansion of Negroid peoples across this continent-wide savanna belt. Also explained perhaps is the extensive, though now fragmented, distribution of languages which Greenberg combines in his ‘Nilo-Saharan’ super-family. It is suspected that aspects of this ancient aquatic way of life may be maintained or reflected by latter-day isolated or ‘unclean’ lake or swamp communities. This subject has been largely neglected by African culture-historians.Drier conditions in the late sixth and fifth millennia b.c. signalled a decline of this aquatic civilization and, in particular, broke its geographical continuity. Nevertheless, there was a qualified revival in many parts in the fourth and third millennia. In the Kenya rift this later phase seems to equate with the first stage of the ‘stone bowl cultures’. Around Lake Victoria a devolved relic survived until the eve of Bantu expansion about two thousand years ago. Other late or modified examples are known on the Nile and in the western Sudan. Generally, however, the viability and prestige of an aquatic way of life were undermined by the second millennium b.c. In the Sahara and Sahel as well as in the northerly parts of eastern Africa this decline was paralleled by the spread of pastoralism as a new basis of subsistence and prestige. Those who introduced cattle to Kenya from Ethiopia were Cushitic-speakers maintaining, significantly, a fish-taboo.This subject should prove of considerable historiographical interest. The aquatic way of life flourished through Middle Africa at the very time when grain-agriculture and stock-raising were being pioneered in the Near East; and the slow spread of agriculture in Africa, sometimes considered an indication of ‘backwardness’, may be partly explicable by the very success of the aquatic life and of its distinct cultural tradition which was ascendant for a while across the widest part of the continent.

Joint inversion and collaborative interpretations in complex geodynamical context

2020 ◽  
Author(s):  
Christel Tiberi ◽  
Adeline Clutier ◽  
Matthieu Plasman ◽  
Stéphanie Gautier ◽  
Fleurice Parat ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Joint Inversion ◽  
Dynamical Evolution ◽  
Active Regions ◽  
East African ◽  
Lithospheric Deformation ◽  
Complex Interactions ◽  
New Information ◽  
Structure Heterogeneity ◽  
African Rift

<p>Active regions concentrate different geodynamical processes sometimes with complex interactions and retroactions. In order to understand the associated lithospheric deformation and evolution, scientists deduce crustal and mantle structures from sparse, inaccurate and indirect observations. In particular, geophysics aims at retrieving physical properties of crustal or lithospheric media from gravity, electric or seismic measurements. Those indirect tools have been used for decades now to image the Earth Interior at many different scales, from the surface down to the Core.</p><p>Besides, density, resistivity or seismic velocity retrieved from geophysical inversions are sensitive to many different factors (temperature, pressure, melt, composition…), each of them impacting the parameters variously. Finally, each of these methods presents its own depth investigation and accuracy, which depends on time lap, network configuration, data wavelength, etc.</p><p>In order to distinguish the role of each factor in the lithospheric structure heterogeneity, and to counteract the different method limits, geophysicists have combined their observations in combined schemes for decades now. We will present here how jointly inverting seismic tomography and gravity may help to better understand complex zones implying melt, faults, crustal modification and plate interaction. When mathematical link between the parameters doesn’t exist, we will present a combination of petrophysics and geophysics, that brings new information on past and present dynamical evolution in a magmatic area (East African Rift, Tanzania). Finally, we will address the question of the real benefit of a joint inversion, and whether we can combine all kind of data.</p>

scholarly journals Isotopic evidence for climatic, ecologic, and faunal change in the Siwaliks of Pakistan

1992 ◽  
Vol 6 ◽  
pp. 54-54
Author(s):  
Thure E. Cerling ◽  
Jay Quade
Keyword(s):  
Isotopic Composition ◽  
Tooth Enamel ◽  
Indian Subcontinent ◽  
Carbon Isotopic Composition ◽  
Major Change ◽  
Global Circulation ◽  
Carbon Isotopic ◽  
Tropical Grasslands ◽  
Major Shift ◽  
Soil Carbonates

The biggest replacement of fauna in the Siwaliks of Pakistan takes place between 7.5 and 7.0 million years (Ma) ago. By 5 Ma, almost the entire fauna that existed at 8 Ma had been replaced by a different fauna. Although other important faunal changes occurred at about 13.5, 12, and 9.5 Ma those changes are small compared to that between 7.5 and 7.0 Ma. What event caused the wholesale local extinction of fauna which was replaced by another?The stable isotopic composition of paleosol carbonate shows two important “events” in the Siwalik sequence. First, at 8 Ma a big shift in the δ18O of soil carbonate indicates that a major shift in climate occurred. We have found a similar change in Europe and East Africa in soil carbonates on those continents, suggesting a major change in global circulation patterns. The second event is a change in the isotopic composition of carbon-bearing phases which shows that the pre-7.5 Ma vegetation was dominated by C3 plants which were completely replaced by C4 plants between 7 and 6 Ma. This is most likely a replacement of woody plants by tropical (C4) grasses.The carbon isotopic composition of tooth enamel from Siwalik mammals shows that prior to 7.5 Ma they consumed C3 plants, and by 5 Ma consumed only C4 plants. While it comes as no surprise that animals eat local vegetation, this study shows that isotopic reconstruction of paleo-diets can be traced back into the Tertiary.Global climatic change in the late Miocene resulted in the invasion of tropical grasslands into the Indian subcontinent. The resulting change in habitat and diet caused the migration of many species of mammals, which is manifested as an almost complete turnover in the fauna fo the Siwaliks.

Background

2004 ◽  
Author(s):  
William H. Kimbel ◽  
Yoel Rak ◽  
Donald C. Johanson ◽  
Ralph L. Holloway ◽  
Michael S. Yuan
Keyword(s):  
Fossil Record ◽  
Eastern Africa ◽  
Northern Ethiopia ◽  
East African ◽  
Afar Depression ◽  
The North ◽  
Time Period ◽  
African Rift ◽  
The One ◽  
Fossil Hominin

Australopithecus afarensis is a fossil hominin species known from at least four East African Rift Valley sites ranging from northern Ethiopia in the north to northern Tanzania in the south and bridging the time period between approximately 3.6 and 3.0 million years ago (Ma). First identified in the late 1970s as the bipedal but craniodentally apelike rootstock from which later Australopithecus and Homo evolved (Johanson et al., 1978; Johanson and White, 1979), A. afarensis constituted the first substantial record of unequivocal human ancestors older than 3.0 million years (Myr). An array of more recently made discoveries have placed A. afarensis in a pivotal position in early hominin phylogeny, bracketed in time between, on the one hand, two temporally successive species, A. anamensis and Ardipithecus ramidus, that jointly extend the hominin record back to 4.4 Ma (M. Leakey et al., 1995, 1998; White et al., 1994, 1995), and, on the other hand, the earliest strong (stratigraphic) evidence for hominin lineage diversification, with the first known records of A. africanus (ca. 2.7 Ma) in southern Africa, and of A. aethiopicus (ca. 2.7 Ma) and A. garhi (2.5 Ma) in eastern Africa (Walker et al., 1986; Asfaw et al., 1999).2 The task of sorting out the relationships among all of these species hinges on the interpretation of A. afarensis itself, from its alpha taxonomy and phylogenetic role to its pattern of evolution over time. A prerequisite to achieving this goal is a more complete knowledge of the A. afarensis fossil record, narrowing gaps in our knowledge of anatomy and variation, as well as of distributions in space and time. On sample size alone, A. afarensis is the best-known hominin species in the eastern African fossil record. The vast majority of fossils in the A. afarensis hypodigm, some 360 specimens, or approximately 90% of the total, have been recovered at the Hadar site, from the 200+ meter sequence of silts, sands, and clays that comprise the Hadar Formation, which is exposed along the drainages of the Awash River in the Afar Depression of northern Ethiopia (Johanson et al., 1982a; Kimbel et al., 1994).

A perspective on Plio-Pleistocene hydrosystems of the northern Turkana Depression (East African Rift System) reconstructed from the study of freshwater mollusk communities

2021 ◽  
Author(s):  
Juan Andrade ◽  
Mathieu Schuster ◽  
Alexis Nutz ◽  
Bert Van Bocxlaer
Keyword(s):  
Environmental Changes ◽  
East African Rift ◽  
Freshwater Ecosystems ◽  
Rift System ◽  
East African Rift System ◽  
East African ◽  
Faunal Turnover ◽  
Freshwater Mollusk ◽  
African Rift ◽  
Freshwater Mollusks

<p>The northern Turkana Depression of the East African Rift System in Northern Kenya and Southwestern Ethiopia has one of the most complete and well-documented late Cenozoic continental fossil records worldwide, including remarkable finds of early hominins and associated African Cenozoic vertebrates. Most previous paleoenvironmental reconstructions of the depression were developed using terrestrial vertebrate faunas and paleolandscapes, leaving freshwater ecosystems and associated hydrosystems (lakes, tributaries, river deltas, and wetlands) largely unaddressed. African Cenozoic freshwater mollusks were long considered to be good biostratigraphic indicators, given that their communities are able to represent long phases of morphological stability and at other times rapid morphological changes. However, to what extent changes in freshwater mollusk assemblages match with changes in sedimentary landscapes and lake level fluctuations remains unclear. Here, we address this question through integrative studies on Plio-Pleistocene fossil freshwater mollusks assemblages. Specifically, we are developing a taxonomic framework on fossil freshwater bivalves belonging to the families Unionidae, Iridinidae, Etheriidae and Corbiculidae to create a standardized overview of stratigraphically well-characterized fossil assemblages. Subsequently, we integrate this paleontological dataset with sedimentological characterizations of the depositional environments in which shell beds accumulated at high resolution around faunal turnover events. A detailed reconstruction of environmental changes and how these changes affected freshwater ecosystems in the northern Turkana Depression may allow us to recognize key environmental drivers that triggered faunal turnover events. Such an understanding of drivers from the past perhaps provides our best hope to anticipate how future environmental changes will alter freshwater ecosystems in tropical Africa, and, ultimately, the availability of various freshwater resources on which humanity depends.</p>

Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

2012 ◽  
Vol 78 (2) ◽  
pp. 256-265 ◽  
Author(s):  
Tom H. Brookman ◽  
Stanley H. Ambrose
Keyword(s):  
Seasonal Variation ◽  
Isotopic Composition ◽  
Environmental Changes ◽  
Tooth Enamel ◽  
Time Averaging ◽  
Isotopic Variation ◽  
Growth Increments ◽  
Serial Sampling ◽  
Isotopic Analyses ◽  
Oxygen Isotopic

AbstractSerial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ13C and δ18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north–south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

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