New fossil remains of Homo naledi from the Lesedi Chamber, South Africa

The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species

The evolution of the modern dam conflict on the Snake River, USA

As dams age and values shift, communities face dam removal decisions that involve navigating complex social, economic and ecological interactions. Sometimes, this results in decades-long conflicts, such as that over the removal of the four lower Snake River dams (LSRD) in Washington State, USA–the focus of this study. We apply a broad analytical framework to understand how key factors in this conflict perpetuate it. We find that western science and economic expertise are politicized, and that while venues and geographies for stakeholder engagement are expanding, these shifts are not powerful enough to interrupt the cycle of litigation sustaining the LSRD debate.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

New sedimentary structures in seismites from SW Tanzania: evaluating gas- vs. water-escape mechanisms of soft-sediment deformation

Seismite horizons are abundant in Cretaceous sandstones of the Rukwa Rift Basin, southwestern Tanzania. Diverse morphologies of soft-sediment deformation are preserved, including two new, unusual sedimentary structures, herein referred to as 1) balloon-shaped inflation structures and 2) surface fractures with linked sandstone splays. This original description of new sedimentary structures contributes to the growing catalogue of seismically induced deformation features. Their unusual morphologies bring to the forefront an important, though seldom touched upon, question of how to differentiate between gas- and water-escape in soft-sediment deformation features. The recognition of the spectrum of soft-sediment deformation structures contained in strata and their deformational mechanisms is important because it permits the differentiation between triggering mechanisms, particularly seismic activity, and can constrain such events spatially and temporally. We interpret the surface fractures and linked sandstone splays to reflect a high gas effusion rate, formed by the release of high-pressure gas followed by a limited expulsion of water. The balloon-shaped inflation structures reflect lower gas effusion rates due to expulsion of lower pressure gas that did not breach the Cretaceous surface seal. When these gas pulses did breach the paleosurface, they formed gas-discharge pits. These seismogenic structures are consistent with deposition of Cretaceous strata in the Rukwa Rift during periods of active carbonatite volcanism, seismicity, and possibly hot spring activity. This documentation serves as an important data point for the re-examination of the classification scheme of soft-sediment deformation structures as primarily water-escape structures to accommodate for the genesis of some secondary sedimentary features by gas-escape

Development of large-scale seismites in Upper Cretaceous fluvial sandstones in a fault-proximal setting

Large-scale soft-sediment deformation structures occur within fluvial sandstone bodies of the Upper Cretaceous Wahweap Formation in the Kaiparowits basin, southern Utah, USA. These structures represent an exceptional example of metre-scale fault-proximal, seismogenic load structures in nearly homogenous sandstones. The load structures consist of two types: large-scale load casts and wedge-shaped load structures. Large-scale load casts penetrate up to 4·5 m into the underlying sandstone bed. Wedge-shaped load structures include metre-scale, parallel, sub-vertical features and decimetre-scale features along the periphery of the large-scale load casts or other wedgeshaped load structures. Wedge-shaped load structures contain well-developed, medial cataclastic shear deformation bands. All load structures contain pervasive well-defined millimetre-thick to centimetre-thick internal laminae, oriented parallel to the outside form of the load structures and asymptotic to deformation bands. Both types of load structures formed because of an inverted density profile, earthquake-triggered liquefaction and growth of irregularities (a Rayleigh–Taylor instability) on the sandstone–sandstone erosional contact. The internal laminae and deformation bands formed during deformation and clearly demonstrate polyphase deformation, recording a transition from liquefied to hydroplastic to brittle modes of deformation. Decimetre-scale wedge-shaped load structures on the edge of the large-scale load casts probably formed towards the end of a seismic event after the sediment dewatered and increased the frictional contact of grains enough to impart strength to the sands. Metre-scale wedge-shaped load structures were created as the tips of downward foundering sediments were driven into fractures, which widened incrementally with seismic pulsation. With each widening of the fracture, gravity and a suction effect would draw additional sediment into the fracture. Superimposed laminae indicate a secondary syndeformational origin for internal laminae, probably by flow-generated shearing and vibrofluidization mechanisms. Large-scale and wedgeshaped load structures, polyphase deformation and secondary laminae may characterize soft-sediment deformation in certain fault-proximal settings

Implications of the internal plumbing of a Late Cretaceous sand volcano: Grand Staircase-Escalante National Monument, Utah

[Extract] A vertical, cross-sectional exposure through a well-preserved sand blow and the associated volcano was discovered 1.8 m above the base of the Upper Cretaceous upper member of the Wahweap Formation. Preserved features within the feeder conduit (pipe) of the sand vo1cano facilitate reconstruction of the vertical fluid flow and interpretation of liquefied sand flow generated by local seismogenic faulting. In the lower reaches of the conduit, a dilation fracture crosscuts a low-permeability, fine-grained sandstone seal. Above this, the conduit widens and the edges become more diffuse in the overlying higher-permeability sandstone, and conversely, the pipe contracts in diameter as it passes through lower-permeability sandstones. This change in character of the pipe, in addition to the structureless sandstone adjacent to the pipe, indicates that lateral flow to the conduit was greater in the high-permeability zones. Within the pipe, subvertical stringers of granules 30 cm below the vent indicate that fluid row of the liquefied sediment was of sufficient velocity to move granules. Medium to fine sand, elutriated from the sediment in the conduit, forms the subarial sand volcano cone. The internally massive surface volcano is slightly asymmetrical, measuring ~120 cm in apparent diameter and ~20 cm in height and is onlapped by the lee face of a fluvial dune. Modern sand volcanoes often develop proximal to faults as a result of high-magnitude seismic events. This ancient sand volcano is located in close proximity to a series of normal faults and, along with other preserved syntectonic deposits in the Wahweap Formation, indicates that the fault slip history includes intense, high-magnitude seismic activity

Evidence for 2.0 Ga continental microbial mats in a paleodesert setting

Early evolved microbial communities characterized the initial biological invasion of Precambrian continental landscapes. In modern arid settings, microbial mats and biological soil crusts are well-developedand stabilize sediment. The Paleoproterozoic Makgabeng Formation in South Africa is one of the oldestand best preserved, dryland systems on Earth. Six types of microbial mat-related structures are nowrecognized within these depositional systems. This paper presents three newly discovered structures that include tufted microbial mat, biological soil crusts, and gas-escape features, in addition to three previously documented structures that include roll up features, sand cracks, and wrinkled features. These discoveries demonstrate that microbial communities were well-established and inhabited diverse continental settings by 2.0 Ga, approximately 200 million years after the onset of the Great Oxidation Event

Evidence for climate shifts in the similar to 2.0 Ga upper Makgabeng Formation erg, South Africa

Eolian ergs, and associated environs are sensitive to short- and long-term climate changes. In one of the oldest, erg deposits, the ~2.0 Ga Makgabeng Formation, facies association changes reflect one of the earliest recordings of short-term climatic shifts in a continental setting. The Makgabeng Formation is separated into lower and upper erg deposits by a playa or saline pan deposit. The lower erg deposit consists of dune sets with thin lenses of dry and deflationary interdunes that transitions vertically to thicker damp to wet interdunes. A laterally persistent playa deposit in the middle of the section consists of mudstone with deep and shallow penetrating mud cracks and subordinate siltstone and sandstone interbeds. Above this lower mudstone interval, the playa strata are sandy. Overlying the playa deposit, the upper erg deposit consists of thick eolian sets with thin lenses of dry interdune deposits. Grain size change near the top of the upper erg deposit corresponds to the appearance of fluvial, sheet flood, eolian cross-beds sculpted by mass flows, and thin playa deposits. The vertical facies association demonstrates shifts in precipitation and fluctuating water tables. Fluvial and playa deposits record high water tables whereas low-water tables are reflected in the core erg. The transition from a lower to higher water table is recorded by wet interdune interspersed within the dune strata towards the top of this interval. Rapid climatic amelioration occurred near the termination of the Makgabeng erg resulting in impingement of ephemeral river systems, development of playas, and generation of massive sand flows. This 2.0 Ga erg demonstrates the impact of climate change on erg development, resulting from shifts in the monsoonal impingement through time.Kutztown University Undergraduate Research Committee, Kutztown University Research Committee, Kutztown University Foundation, Kumba-Exxaro, the National Research Foundation, and the University of Pretoria in South Africa.http://elsevier.com/locate/palaeohb201

Oligocene termite nests with in situ fungus gardens from the rukwa rift basin, Tanzania, support a paleogene african origin for insect agriculture

Based on molecular dating, the origin of insect agriculture is hypothesized to have taken place independently in three clades of fungus-farming insects: the termites, ants or ambrosia beetles during the Paleogene (66-24 Ma). Yet, definitive fossil evidence of fungus-growing behavior has been elusive, with no unequivocal records prior to the late Miocene (7-10 Ma). Here we report fossil evidence of insect agriculture in the form of fossil fungus gardens, preserved within 25 Ma termite nests from southwestern Tanzania. Using these well-dated fossil fungus gardens, we have recalibrated molecular divergence estimates for the origins of termite agriculture to around 31 Ma, lending support to hypotheses suggesting an African Paleogene origin for termite-fungus symbiosis; perhaps coinciding with rift initiation and changes in the African landscape.</p

Providing context to the Homo naledi fossils: Constraints on the age of sediment deposits in the Rising Star Cave, South Africa

Rising Star Cave in the Cradle of Humankind, South Africa, contains one of the richest hominin-bearing deposits in the world, and is the type locality for the Homo naledi fossils. This paper provides a stratigraphic and geochronological framework, within which published and future fossil finds from Rising Star Cave can be placed. Detailed mapping of flowstone horizons combined with new age constraints based on both U-Th disequilibrium and 234U/238U dates and one new OSL date help define seven periods of flowstone formation that punctuate episodes of clastic sedimentation and erosion. Clastic sediments entered the cave through an opening in the roof of the Postbox Chamber from about 600 ka onward, until the opening was choked by coarse breccia blocks, probably sometime after 180 ka. Depositional and erosional events changed the internal morphology of the cave chambers over time, and thereby changed the access route into the Dinaledi Chamber where the bulk of the H. naledi fossils were found. Periods of pervasive flowstone formation at all levels of the cave occurred at >600 ka, ~500–400 ka, ~225–190 ka and ~110-90 ka. Additional periods of localised flowstone growth restricted to individual chambers (or parts thereof) occurred at ~300 ka, ~160 ka, ~70 ka, ~50 ka, ~30 ka, and ~10 ka. Flowstone horizons bracket sedimentary units that include a variety of sediment types that changed with time. The oldest flowstones overlie lithified mud clast breccias (LMCB), which were partly eroded before they were covered by externally derived laminated orange sands (LOS) and 500–400 ka flowstones. These flowstones and sands were removed between 290 ka and 225 ka, with sediment transported to deeper parts of the cave via erosion channels characterised by massive orange sands (MOS). In this period of time, the access route into the Dinaledi Chamber may have further changed due to the collapse of the Dragon's Back block. Deposition of laminated orange-red mud (LORM) from suspension occurred between 225 and 190 ka and temporally overlaps with widespread flowstone formation around ~225 ka and ~200 ka. The LORM deposits were largely removed from the upper chambers by ~110 ka, before the youngest group of flowstones formed in the cave; some of which are still growing today. The U-Th ages from Rising Star Cave, combined with other dating constraints reveal age clusters of flowstone formation, which coincided with warmer interglacial or interstadial periods. The patterns recognised in Rising Star Cave overlap with periods of flowstone formation recognised in nearby caves in the Cradle of Humankind, thereby confirming a regional climatic control on flowstone growth in caves during the past 500 ky. The new ages further constrain the minimum age of H. naledi to ~241 ka. Thus, H. naledi entered the cave between 241 ka and 335 ka, during a glacial period, at which time clastic sediments inside the cave were undergoing erosion. H. naledi would probably have entered the cave through an access point in the roof of the Postbox Chamber and made its way along a SW trending fracture towards the Dragon's Back and Dinaledi Chambers

Photographs of specimens <i>in situ</i> displaying different morphologies and weathering stages.

<p>(A) Sample RRBP 08248a (Colony 1) with preserved fungus comb. (B) Sample RRBP 08248c (Colony 1). (C) Sample RRBP 08248g showing galleries and concentric chambers (Colony 1). (D) Uncollected nest RRBP 08248d (Colony 1) showing an external morphology and gallery network above the main nest.</p