The age of homo naledi and associated sediments in the rising star cave, South Africa

New ages for flowstone, sediments and fossil bones from the Dinaledi Chamber are presented. We combined optically stimulated luminescence dating of sediments with U-Th and palaeomagnetic analyses of flowstones to establish that all sediments containing Homo naledi fossils can be allocated to a single stratigraphic entity (sub-unit 3b), interpreted to be deposited between 236 ka and 414 ka. This result has been confirmed independently by dating three H. naledi teeth with combined U-series and electron spin resonance (US-ESR) dating. Two dating scenarios for the fossils were tested by varying the assumed levels of222Rn loss in the encasing sediments: a maximum age scenario provides an average age for the two least altered fossil teeth of 253 +82/-70 ka, whilst a minimum age scenario yields an average age of 200 +70/-61 ka. We consider the maximum age scenario to more closely reflect conditions in the cave, and therefore, the true age of the fossils. By combining the US-ESR maximum age estimate obtained from the teeth, with the U-Th age for the oldest flowstone overlying Homo naledi fossils, we have constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the later parts of the Pleistocene in Africa, and indicate a much younger age for the Homo naledi fossils than have previously been hypothesized based on their morphologyWe would also like to thank the many funding agencies that supported various aspects of this work. In particular we would like to thank the National Geographic Society, the National Research Foundation and the Lyda Hill Foundation for significant funding of the discovery, recovery and initial analysis of this material. Further support was provided by ARC (DP140104282: PHGMD, ER, JK, HHW; FT 120100399: AH). The ESR dosimetry study undertaken by CENIEH and Griffith University has been supported by a Marie Curie International Outgoing Fellowship (under REA Grant Agreement n˚ PIOF-GA-2013–626474) of the European Union’s Seventh Framework Programme (FP7/2007-2013) and an Australian Research Council Future Fellowship (FT150100215). ESR and U-series dating undertaken at SCU were supported by ARC (DP140100919: RJB)

Integrating paleoseismic studies with geochronology and thermochronology to understand the timing of rifting, volcanism and uplift in the Rukwa Rift Basin, Tanzania

Although continental rifting has contributed to shaping the Earth's landmasses and landscapes for arguably a large part of our planet's history, the archetypal East African Rift System is one of very few active continental rifts on the Earth today. Research to better understand rifting mechanisms and rift evolution is of great interest because rifts are natural laboratories for understanding how continents break up. Furthermore, rifts result in the accumulation of thick sediments with the potential to form both hydrocarbon resources and rich fossil archives of past ecosystems and climates. The break-up of lithosphere also leads to significant disturbances of the Earth's surface, and consequently rift regions are regarded as geologic hazards, involving large magnitude earthquakes, volcanic eruptions, debris flows, and more. In an effort to elucidate some of the complexities of the active East African Rift System, this research has focused on a lesser-studied segment of the western branch of the East African Rift System, the Rukwa Rift Basin, located in southwestern Tanzania. Developed within the Paleoproterozoic Ubendian orogenic belt between the margins of Archean cratons, the Rukwa Rift Basin is unique because it preserves one of the thickest (~9-11 km) and best-exposed sedimentary sequences in East Africa, containing sedimentary units deposited from the Permian – Recent times, including a rare window into the late Oligocene and late Miocene continental records that are not exposed anywhere else in subequatorial Africa. The common objective of the studies presented here was to decipher how a sedimentary basin within a continental rift zone records the complex relationships between the generation of accommodation space, uplift, volcanism, faulting, and sediment drainage and depositional patterns in response to rifting. Previous work on the rift flanks, volcanic rocks, and stratigraphy provided only a limited view into this important basin, and so an integrated approach to basin analysis was devised in order to understand the above associations via a sedimentary perspective. U-Pb geochronology has been combined with (U-Th)/He and fission track low-temperature thermochronology and applied to detrital zircons and apatites from the sedimentary sequences of the Rukwa Rift. U-Pb dating of newly discovered tuffs and detrital zircons from well cuttings revealed that after initial rifting in the late Oligocene, renewed volcanism and sediment accumulation began again by at least 8.7 Ma in the Rukwa Rift Basin. Provenance studies of the Lake Beds succession that contains these late Miocene tuffs reveal that the Rukwa Rift Basin was internally draining through to at least the Pliocene, implying that rift flank and volcanic topography impeded drainage inlets and outlets. A new approach for utilizing hydrocarbon exploration well cuttings for detrital zircon analysis, specifically to obtain maximum depositional age control, was developed as a part of this study on the Lake Beds, and has the potential to become a powerful new tool for stratigraphic dating and correlation for hydrocarbon exploration. Detrital lowtemperature thermochronology data suggests that there was minimal uplift associated with either pulse of rifting and sedimentation (at ~25 and ~9 Ma) recorded in the Rukwa Rift Basin, and therefore much of the high topography and incised landscape observed today in this part of eastern Africa likely developed during the late Pliocene to Quaternary. Multiple populations of cooling ages spanning the Paleoproterozic to Late Cretaceous obtained from detrital zircon and apatite low-temperature thermochronology suggests that the Rukwa Rift and vicinity was subject to repeated far-field tectonic stresses. The sedimentary record in the Rukwa Rift also preserves a rare archive of seismicity, in the form of soft-sediment deformation features (seismites). This research has documented several new seismite morphologies, expanding the database of seismogenic sedimentary structures, which is important for future seismic hazard preparations and predictions. Extensive seismites from the Late Quaternary to Recent upper Lake Beds have been documented, including a decameter-scale clastic 'megablock complex' correlative to similarly sized recumbent folds over 35 km away; evidence for Late Pleistocene large magnitude earthquakes in the Rukwa Rift Basin. In addition, new seismogenic sedimentary structures from the Cretaceous Namba Member of the Galula Formation, termed 'balloon-shaped inflation structures', formed primarily by gas-escape as opposed to the more commonly called upon mechanism, water-escape. This discovery not only has shed light on the longevity of seismic activity within the Rukwa Rift Basin, but also serves as an important discovery for the re-examination of the classification scheme of soft-sediment deformation structures. The results of combined zircon and apatite detrital- and tephro-geochronology and thermochronology have been integrated with sedimentology-based paleoseismic investigations to provide new insights into the history of the Rukwa Rift Basin, which has important implications for documenting the evolutionary record and for documenting previously unknown seismic activity. Constraining the magnitude and timing of rifting events, magmatism, faulting, and uplift is critical because these processes created and fundamentally changed the landscape, redirected drainages, affected local climate, and more, all of which have major implications for the flora and fauna, including hominins, that evolved along the East African Rift valleys

A U/Pb detrital zircon provenance study of the flysch of the Paleogene Orca Group, Chugach-Prince William Terrane, Alaska

The southern Alaska continental margin is comprised of highly deformed, offscraped, and underplated deep-sea rocks that have been accreted from the Late Triassic to the present. These rocks constitute one of the largest subduction-related accretionary complexes in the world. The outboard part of the Mesozoic to Tertiary Chugach-Prince William composite terrane (CPW) is composed of deep-water turbidites (flysch) and associated volcanic rocks exposed for ~2,000 km in southern Alaska. In an effort to better understand the tectonic evolution of southern Alaska, this paper focuses on the Orca Group, the outboard Paleogene flysch of the CPW terrane. U-Pb zircon age data (n = 1400) from the Orca Group reveal an inboard to outboard (NW to SE) maximum depositional age progression from ~69 Ma to ~35 Ma. This time bracket is important because it spans the time when the CPW is proposed to have either 1) interacted with the fixed (relative to North America) Kula-Farallon trench-ridge-trench triple junction south of its present latitude and then migrated along the North American coast to its present position, or 2) interacted with the migrating Kula-Resurrection trench-ridge-trench triple junction at its present latitude. These maximum depositional ages also show that deposition was contemporaneous with the intrusion of the flysch by the near-trench plutons of both the 61 to 48 Ma Sanak Baranof belt and the ~37-39 Ma Eshamy suite. In addition, these ages suggest nearly continuous deposition (from 157 to 35 Ma) of the CPW from the inboard McHugh Complex through the outboard Orca Group. U-Pb detrital zircon age data in combination with fission track analysis divide the Orca Group into three unique fault-bounded belts. U-Pb detrital zircon ages from this study reinforce the along-strike correlation between the Kodiak Formation and the Valdez Group, the Ghost Rocks Formation and the inboard Orca Group, and the Sitkalidak Formation and the outboard Orca Group. U-Pb age spectra of the Orca Group and the Kootznahoo Formation in southeast Alaska are similar, suggesting that the Orca was partially sourced by the Coast Mountains Batholith. This work advances methods of detrital zircon U-Pb analysis through a new approach, targeting key Precambrian grain populations. Data enhanced by this new methodology reveals dominant Precambrian age populations between 1787 and 1865 Ma, suggesting that the southern Rocky Mountains Yavapai-Mazatzal terrane might also be a potential source for the Orca flysch

The water and peace Nexus: insights via a global media analysis and a historical analysis of the Syria-Turkey friendship Dam

This MSc thesis is based on work and research carried out by the author during an internship at the Geneva Water Hub. The Geneva Water Hub works to enable water to be used as an instrument of peace. Two main projects are presented in this thesis: (1) The Water Diplomat media data project, and (2) hydropolitical and hydrodiplomatic research on the Syria-Turkey Friendship Dam. The Water Diplomat project documents the development, construction, and analysis of a database of hydrodiplomacy media, contributing to the Geneva Water Hub’s Global Observatory on Water and Peace. The research study of the Syria-Turkey Friendship Dam aims to understand the (hydro)political and (hydro)diplomatic variables that can lead to the establishment of so-called “friendship dams” and to begin to understand what purpose such dams play in the context of transboundary water cooperation. This work aims to be a first steppingstone towards a conceptual understanding of “friendship dams”

Giant seismites and megablock uplift in the East African Rift: evidence for Late Pleistocene large magnitude earthquakes

In lieu of comprehensive instrumental seismic monitoring, short historical records, and limited fault trench investigations for many seismically active areas, the sedimentary record provides important archives of seismicity in the form of preserved horizons of soft-sediment deformation features, termed seismites. Here we report on extensive seismites in the Late Quaternary-Recent (≤ ~ 28,000 years BP) alluvial and lacustrine strata of the Rukwa Rift Basin, a segment of the Western Branch of the East African Rift System. We document examples of the most highly deformed sediments in shallow, subsurface strata close to the regional capital of Mbeya, Tanzania. This includes a remarkable, clastic 'megablock complex' that preserves remobilized sediment below vertically displaced blocks of intact strata (megablocks), some in excess of 20 m-wide. Documentation of these seismites expands the database of seismogenic sedimentary structures, and attests to large magnitude, Late Pleistocene-Recent earthquakes along the Western Branch of the East African Rift System. Understanding how seismicity deforms near-surface sediments is critical for predicting and preparing for modern seismic hazards, especially along the East African Rift and other tectonically active, developing regions

Field photographs of the megablock complex at the Songwe Megablock Site.

<p>(A) Megablock unit and offset conglomerate unit. (B) “Blowout” fault bounding the left side of the injectite. (C) Clastic injection dyke emerging from basal LBS conglomerate. Note the pebbles and cobbles entrained in the dyke, as well as the offset dyke segments. (D) Panoramic photograph of injectite complex outcrop, highlighting its position within undeformed, horizontal Lake Beds strata. Person is for scale on the lower right of the injectite.</p

AMS radiocarbon dates from the Songwe Valley region.

<p>(A) Dates from the Ilasilo 6 seismite, Songwe Megablock site, and samples from Cohen et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129051#pone.0129051.ref045" target="_blank">45</a>] sourced near Ilasilo 6. (B and C) The intersection of the megablock unit sample (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129051#pone.0129051.g003" target="_blank">Fig 3</a>) and Ilasilo 6 seismite sample radiocarbon dates (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129051#pone.0129051.g004" target="_blank">Fig 4</a>), respectively, with the calibration curve [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129051#pone.0129051.ref017" target="_blank">17</a>].</p

Correlation of Ilasilo 6 and the Songwe Megablock sites, with model approximating age of deformation.

<p>The Songwe Megablock Site radiocarbon sample is from an organic-rich layer containing macrofossil reeds of the unit that was fractured and uplifted, forming the megablock (UTM: 522904 E 9015130 N, zone 36, ARC 1960 datum). The Ilasilo 6 radiocarbon sample is from a black, fossiliferous, organic-rich unit ~1.5 meters below the large-scale seismite (UTM: 502917 E 9044472 N, zone 36, ARC 1960 datum). These two indistinguishable radiocarbon dates provide a tie point for the correlation of the two deformed outcrops over 35 km, and support the hypothesis for synchronous deformation of the megablock complex and asymmetric, recumbent folds.</p

Seismites from the Lake Beds Succession at Ilasilo 6.

<p>(A and B) Clastic injection dykes. Vertical movement of clasts of the sidewall rock and sandstone parent bodies present below the field of view of the photographs indicate upward-directed injection. Bottom scale in (A) is in cm. (C) Ball-and-pillow structure. (D) Cm-scale convolute bedding. (E) Convolute bedding, folds, flame structures, and evidence of vertical fluid escape. Refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129051#pone.0129051.g004" target="_blank">Fig 4</a> for color-coding. Soft sediment deformation features were photographed on vertical, southwest- (A and B), northeast- (C and D), and southeast-facing (E) canyon walls of LBS strata, exposed by down cutting of modern-day rivers.</p

Outcrop exposure of injectite and megablock complex at the Songwe Megablock Site.

<p>(A) Photograph of megablock complex outcrop. (B) Trace of intact stratigraphy and displaced megablock. Red arrows indicate flow of injectite material. Yellow arrow indicates path of clastic injection dyke. White arrows represent surface alluvium and clasts of the sidewall infilling the top of the clastic injection dyke. (C) Reconstructed megablock in original stratigraphic position. An estimate is made of the cross-sectional surface area of material ejected onto the surface after formation of injectite and vertical displacement of megablock.</p