The continental Middle Miocene Climatic Transition in Southern Europe as derived from clumped isotope analyses

2020 ◽  
Author(s):  
Niklas Löffler ◽  
Andreas Mulch ◽  
Wout Krijgsman ◽  
Emilija Krsnik ◽  
Jens Fiebig
Keyword(s):  
Late Miocene ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Time Interval ◽  
Suitable Model ◽  
Southern Europe ◽  
Carbonate Formation ◽  
Carbon And Oxygen Isotope ◽  
Clumped Isotope ◽  
Isotope Analyses

<p>Reconstructing Cenozoic terrestrial paleoclimate is frequently limited by temporal resolution and suitable quantitative tools to reliably assess changes in temperature and aridity. The dynamics of ocean temperatures<sup>1</sup> and chemistry<sup>2</sup>, varying <em>p</em>CO<sub>2</sub><sup>3</sup>, and faunal assemblages are known to a certain extent, however, terrestrial data on temperatures, which are mostly indirectly derived from fossil assemblages and palynologycal data<sup>4</sup> are rare. This study contributes to the understanding of the dynamics and variability of terrestrial temperatures during one of the most extreme Neogene climate changes, the Middle Miocene Climate Transition (MCT). The comparison of <em>p</em>CO<sub>2</sub> forecasts for the coming century and reconstructed Mid-Miocene <em>p</em>CO<sub>2</sub> levels suggest that the Mid-Miocene is an important time interval for ascertaining suitable model projections of the future anthropogenic impact on climate. In order to establish an appropriate understanding and modeling of the natural variability of the European/Mediterranean climate system, quantitative climate information of the European continental Mid-Miocene is mandatory. This would facilitate the identification of main drivers of climate evolution in an area which is exposed to the present climate change and its subsequent natural hazards.</p><p> </p><p>This study presents a profound and well-dated terrestrial clumped isotope (Δ<sub>47</sub>) paleosoil carbonate dataset from Spain that ranges from 13.0 to 15.1 Ma (100 kyr resolution) and hence covers an interval that was previously classified as the MCT. The Δ<sub>47 </sub>data is supported by stable carbon and oxygen isotope analyses that are in agreement with previously published continental and oceanic records. A distinct decline in apparent Δ<sub>47</sub>-based temperatures between 13.7 and 14.1 Ma reveals a substantial drop in continental temperatures and indicates changes in seasonality of pedogenic carbonate formation. The major cooling thereby coincides with a change in Milanković periodicities and can be linked to oceanic isotope records<sup>5</sup>. While the transition into the MCT shows a high temperature variability indicating varying environmental conditions, calculated oxygen isotopic values of the soil water point to a rather stable moisture source across the MCT in Southern Europe.</p><p> </p><p>1: Super, J. R., Thomas, E., Pagani, M., et al. (2018) North Atlantic temperature and pCO<sub>2</sub> coupling in the early-middle Miocene. Geology, 46(6), 519-522.</p><p>2: Pearson, P. N., and Palmer, M. R. (1999) Middle Eocene seawater pH and atmospheric carbon dioxide concentrations. Science, 284(5421), 1824-1826.</p><p>3: Pagani, M., Freeman, K. H., and Arthur, M. A. (1999) Late Miocene atmospheric CO<sub>2</sub> concentrations and the expansion of C4 grasses. Science, 285(5429), 876-879.</p><p>4: Lewis, A. R., Marchant, D. R., Ashworth, A. C., et al. (2008) Mid-Miocene cooling and the extinction of tundra in continental Antarctica. Proceedings of the National academy of Sciences.</p><p>5: Holbourn, A., Kuhnt, W., Clemens, S., et al. (2013) Middle to late Miocene stepwise climate cooling: Evidence from a high resolution deep water isotope curve spanning 8 million years. Paleoceanography, 28(4), 688-699.</p>

scholarly journals A Middle to Late Miocene Trans-Andean Portal: Geologic Record in the Tatacoa Desert

2021 ◽  
Vol 8 ◽  
Author(s):  
C. Montes ◽  
C. A. Silva ◽  
G. A. Bayona ◽  
R. Villamil ◽  
E. Stiles ◽  
...  
Keyword(s):  
Late Miocene ◽  
Amazon Basin ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Structural Data ◽  
Coverage Area ◽  
Geologic Record ◽  
Mapping Models ◽  
Central Cordillera ◽  
Lines Of Evidence

Integration of several geologic lines of evidence reveals the prevalence of a lowland trans-Andean portal communicating western Amazonia and the westernmost Andes from at least middle Miocene until Pliocene times. Volcanism and crustal shortening built up relief in the southernmost Central and Eastern Cordilleras of Colombia, closing this lowland gap. Independent lines of evidence consist first, of field mapping in the Tatacoa Desert with a coverage area of ∼381 km2, 1,165 km of geological contact traces, 164 structural data points, and 3D aerial digital mapping models. This map documents the beginning of southward propagation of the southernmost tip of the Eastern Cordillera’s west-verging, fold-and-thrust belt between ∼12.2 and 13.7 Ma. Second, a compilation of new and published detrital zircon geochronology in middle Miocene strata of the Tatacoa Desert shows three distinctive age populations: middle Miocene, middle Eocene, and Jurassic; the first two sourced west of the Central Cordillera, the latter in the Magdalena Valley. Similar populations with the three distinctive peaks have now been recovered in western Amazonian middle Miocene strata. These observations, along with published molecular and fossil fish data, suggest that by Serravallian times (∼13 Ma), the Northern Andes were separated from the Central Andes at ∼3°N by a fluvial system that flowed into the Amazon Basin through the Tatacoa Desert. This paleogeographic configuration would be similar to a Western Andean, or Marañon Portal. Late Miocene flattening of the subducting Nazca slab caused the eastward migration of the Miocene volcanic arc, so that starting at ∼4 Ma, large composite volcanoes were built up along the axis of today's Central Cordillera, closing this lowland Andean portal and altering the drainage patterns to resemble a modern configuration.

Tectonics–Earth surface processes interactions of the Central Anatolian Plateau during the late Miocene to Pliocene revealed by ecosystem and paleotemperature reconstructions 

2021 ◽  
Author(s):  
Maud J.M. Meijers ◽  
Gilles Y. Brocard ◽  
Ferhat Kaya ◽  
Cesur Pehlevan ◽  
Okşan Başoğlu ◽  
...  
Keyword(s):  
Late Miocene ◽  
Tooth Enamel ◽  
Surface Processes ◽  
Central Anatolia ◽  
Earth Surface ◽  
Anatolian Plateau ◽  
Surface Uplift ◽  
Carbonate Formation ◽  
Southern Margin ◽  
Clumped Isotope

<div> <p>The Central Anatolian Plateau (CAP, Turkey, elevation ca. 1-1.5 km) was established during the late Miocene. Prior to Pleistocene surface uplift of its southern margin (Tauride Mountains), a southern margin orographic barrier with similar-to-present elevations (ca. 2 km) existed between 8 and 5 Ma.</p> </div><div> <p>To unravel the interactions between tectonics and Earth surface processes, we quantify biotic and abiotic parameters for the late Miocene to Pliocene. As the CAP exposes presently incised fluvio-lacustrine sedimentary rocks of well-dated Miocene to Pliocene age, the region provides an excellent archive for reconstructing past landscape dynamics, such as surface uplift, lake hydrology, and drainage integration. Within this established framework, we now reconstruct the late Miocene to Pliocene ecosystem by measuring clumped isotope (Δ<sub>47</sub>) temperatures of carbonate formation and δ<sup>13</sup>C and δ<sup>18</sup>O values of paleosol carbonate and fossil mammal tooth enamel. Collectively, our data allow for the reconstruction of paleoclimate, vegetation types (C<sub>3</sub> vs. C<sub>4</sub>), mammalian diet, landscape heterogeneity, and seasonality.</p> </div><div> <p>The first clumped isotope-derived paleotemperatures indicate a large (8 <span>°</span>C) temperature difference at ca. 5.5 Ma between lacustrine carbonate from the Mediterranean coastal region (Adana Basin; ca. 26 ± 1.8 <span>°</span>C) and paleosol carbonate from the central Anatolian interior (ca. 18 ± 1.7 <span>°</span>C), which likely reflects the higher elevation of the CAP. Soil carbonate δ<sup>13</sup>C values from the plateau interior (13 sites, N= 344, ca. 10 to 2 Ma) are much higher between ca. 8 and 5 Ma (ca. –3 to 0 ‰) than earlier or later in time (ca. –8 to –5 ‰), which indicates the presence of a significant component of C<sub>4</sub> vegetation, characterized by wooded grasslands and grasslands, during the latest Miocene. In contrast, C<sub>3</sub>-dominated vegetation reflecting more wooded environments were dominant at ca. 10 Ma and from 4 to 2 Ma. The increase in C<sub>4</sub> vegetation during the late Miocene is coeval with surface uplift of the southern CAP margin, whereas an increase of C<sub>3</sub> vegetation by the Pliocene could coincide with a phase of subsidence of the southern CAP margin prior to its final phase of Pleistocene surface uplift. Furthermore, we collected mammal tooth enamel samples (equid, bovid, rhinocerotid, suid) from 11 individuals at one ca. 9 Ma-old and one latest Miocene-Pliocene<span> fossil site. </span>δ<sup>13</sup>C and δ<sup>18</sup>O values indicate the mammals at the two nearby fossil sites had varying diets and therefore access to different vegetation and water supplies. We are currently improving the stratigraphic framework and dating of these fossil sites, as well as obtaining tooth enamel δ<sup>13</sup>C and δ<sup>18</sup>O values of 44 more individuals to further constrain paleoenvironmental conditions and eventually the causality between tectonics and Earth surface processes in central Anatolia.</p> </div><div> <p><span>References:</span><strong><span> </span></strong><span>Meijers et al., 2018a: Palaeo3, doi: 10.1016/j.palaeo.2018.03.001; Meijers et al., 2018b: EPSL, doi: 10.1016/j.epsl.2018.05.040; Huang, Meijers et al., 2019: J of Biogeography, doi: 10.1111/jbi.13622; Meijers et al., 2020: Geosphere, doi: 10.1130/GES02135.1</span></p> </div>

Eocene age for Ag–Pb–Zn–Au vein and replacement deposits of the Kokanee Range, southeastern British Columbia

1992 ◽  
Vol 29 (1) ◽  
pp. 3-14 ◽  
Author(s):  
G. Beaudoin ◽  
J. C. Roddick ◽  
D. F. Sangster
Keyword(s):  
British Columbia ◽  
Middle Jurassic ◽  
Middle Eocene ◽  
Hanging Wall ◽  
Spatial Association ◽  
High Heat ◽  
Time Interval ◽  
Genetic Link ◽  
Metasedimentary Rocks ◽  
Magmatic Event

The Ag–Pb–Zn–Au vein and replacement deposits of the Kokanee Range, southeastern British Columbia, are hosted by the Middle Jurassic Nelson batholith and surrounding Cambrian to Triassic metasedimentary rocks in the hanging wall of the transcrustal Slocan Lake Fault, Field relations indicate that mineralization is younger than the Nelson batholith and a Middle Jurassic foliation in the Ainsworth area but coeval or older than Eocene unroofing of the Valhalla metamorphic core complex in the footwall of the Slocan Lake Fault. Lamprophyre and gabbro dykes are broadly coeval with mineralization and have biotite and hornblende K–Ar ages defining a short-lived Middle Eocene alkaline magmatic event between 52 and 40 Ma. An older, Early Cretaceous alkaline magmatic event (141 – 129 Ma) is possible but incompletely documented.K–Ar and step-heating 40Ar/39Ar analyses on hydrothermal vein and alteration muscovite indicate that hydrothermal fluids were precipitating vein and replacement deposits 58–59 Ma ago. Crosscutting relationships with lamprophyre dykes indicate the Kokanee Range hydrothermal system lasted for more than 15 Ma. Eocene crustal extension resulted in a high heat flow and structures which were probably responsible for hydrothermal fluid movement and flow paths.A 100 Ma time interval is documented between batholith emplacement and spatially associated mineralization, ruling out any genetic link between the two. Similar large age differences between granite intrusion and peripheral mineralization have recently been documented for two world-sea le Ag–Pb–Zn vein districts, which suggest that spatial association between granite and Ag–Pb–Zn mineralization is not sufficient to infer a genetic link.

Middle Miocene (∼14 Ma) and Late Miocene (∼6 Ma) Paleogeographic Boundary Conditions

2021 ◽  
Author(s):  
Zhilin He ◽  
Zhongshi Zhang ◽  
Zhengtang Guo ◽  
Christopher R. Scotese ◽  
Chenglong Deng
Keyword(s):  
Boundary Conditions ◽  
Late Miocene ◽  
Middle Miocene

A new argyrolagoid (Mammalia: Marsupialia) from the middle Miocene of Bolivia

1988 ◽  
Vol 62 (3) ◽  
pp. 463-467 ◽  
Author(s):  
Villarroel A. Carlos ◽  
Larry G. Marshall
Keyword(s):  
South America ◽  
Late Miocene ◽  
Adaptive Radiation ◽  
Middle Miocene ◽  
Northwest Argentina ◽  
The Family ◽  
Size And Structure

A new argyrolagoid marsupial, Hondalagus altiplanensis n. gen., n. sp., from the middle Miocene (Santacrucian–Friasian) age locality of Quebrada Honda in southernmost Bolivia represents the smallest and most specialized member of the family Argyrolagidae known. The lower molars are hypselodont and lack vertical grooves labially and lingually, and M4 is greatly reduced relative to M3. In overall size and structure, H. altiplanensis compares best with Microtragulus catamarcensis (Kraglievich, 1931) from rocks of late Miocene (Huayquerian) age in northwest Argentina. Hondalagus altiplanensis demonstrates that the adaptive radiation of argyrolagoids was much greater than previously envisioned, and that generic differentiation of known taxa occurred no later than early–middle Miocene time in South America.

scholarly journals Structural setting and tectonic evolution of the Bahariya Depression, Western Desert, Egypt

GeoArabia ◽  
2003 ◽  
Vol 8 (1) ◽  
pp. 91-124 ◽  
Author(s):  
Adel R Moustafa ◽  
Ati Saoudi ◽  
Alaa Moubasher ◽  
Ibrahim M Ibrahim ◽  
Hesham Molokhia ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Tectonic Evolution ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Western Desert ◽  
Normal Faults ◽  
Surface Mapping ◽  
Early Mesozoic ◽  
Hydrocarbon Fields ◽  
Stable Area

ABSTRACT An integrated surface mapping and subsurface study of the Bahariya Depression aided the regional subsurface interpretation. It indicated that four major ENE-oriented structural belts overlie deep-seated faults in this part of the ‘tectonically stable’ area of Egypt. The rocks of the Bahariya area were deformed in the Late Cretaceous, post-Middle Eocene, and Middle Miocene-and subsurface data indicated an early Mesozoic phase of normal faulting. The Late Cretaceous and post-Middle Eocene deformations reactivated the early normal faults by oblique slip and formed a large swell in the Bahariya region. The crest was continuously eroded whereas its peripheries were onlapped by Maastrichtian and Tertiary sediments. The tectonic evolution of the Bahariya region shows great similarity to the deformation of the ‘tectonically unstable’ area of the northern Western Desert where several hydrocarbon fields have been discovered. This similarity may indicate that the same phases of deformation could extend to other basins lying in the ‘tectonically stable’ area, such as the Asyut, Dakhla, Nuqura, and El Misaha basins.

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