Widespread Sand Research Articles

A novel approach to understanding the genesis and distribution of widespread reservoirs at the basin edge: A case study of gas-bearing sandstone in the Sangonghe Formation, Junggar Basin, Western China

A 20 m thick sandstone drilled in the second member of the Sangonghe Formation in the Qianshao area of the Junggar Basin has been identified to be a high-quality gas-bearing reservoir. However, recent missions reveal an uncertainty in reservoir distribution and bring high risk to the subsequent gas development, although the gas-bearing reservoir has been encountered by several drillings and proved to be widespread. To investigate the accurate distribution and reveal the evolution of the reservoir, we reconstruct the stratigraphic framework and depositional stages by a high-revolution sequence stratigraphic method, effectively identify the gas-bearing reservoir by seismic attributes refusion and seismic stratigraphic slices, and finally map the distribution strata distribution at different stages. The results indicate that the landward onlap phenomenon in the seismic data indicates a retrogradational stratigraphic structure during the water level rise rather than the equal-thickness stratigraphic pattern under stable water conditions. According to the retrogradational stratigraphic structure, the real driver for the widespread characteristic of a gas-bearing reservoir is the backward staggered movement of multistage sand bodies during the transgressive process rather than single-stage deposition. The fusion of seismic acoustic impedance and main frequency attributes provides an effective survey to identify the accurate distribution of the reservoir, by which interpretation of a stratigraphic slice along the vertical centerline of the reservoir extracted from the multiattribute fusion survey can present the distribution and evolution of the three stages on only one map. Achieved by an appropriate interpretation on the map, two sandy debris flow bodies are identified as being deposited at the bottom successively during the first two transgressive stages. They are completely staggered in the source direction with a clear boundary between well Qs9 and Qs7. Subsequently, the subsequent rise of the water level led to the deposition of a large-scale multibranch shallow-water delta, which exhibits the characteristics of multistage, multisource, and multibranch. The results not only advance our comprehension of widespread sand bodies but also furnish fundamental insights for the development of lithologic condensate gas reservoirs in the Qianshao area.

The effect of dust storms on air quality and public health in the city of Hillah

Dust storms, which have become frequent events, pose great risks to health and the environment. There are three factors responsible for generating them: strong winds, lack of rain, and lack of vegetation cover. AirQ+ software developed by the World Health Organization, was used to assess the health risks resulting from short-term exposure to PM2.5 measured using Continuous Particulate Monitor BAM-1020 for a period of two years from Jan 2021 to Jan 2023. The frequency and intensity of dust storms were recorded during the summer and spring of 2022, with high concentrations. The concentrations of the pollutant PM2.5 range during storm days (213.89 - 674.48 μg/m3), where short-term exposure causes an increase in the risk of respiratory illnesses and cardiovascular diseases. The most severe dust storms (674.48 μg/m3) caused a rise in the risk relative to 3.395 for respiratory diseases and 1.801 for cardiovascular disease. The great danger of dust storms is evident by comparing them with corresponding days for the year 2021, where the relative risk did not exceed 1.03for respiratory diseases and 1.01) for cardiovascular diseases. In general, air quality was classified using the concentrations obtained, where the concentrations of PM2.5 increased strongly, especially during the dry months, and the sand and dust storms that happened in 2022 caused the air quality to become dangerous by 2%, very unhealthy by 6%, and unhealthy by 8%. As for the other pollutants (SO2, NO2, and CO), they did not rise much beyond the allowable limit, and it has no direct relationship with dust storms, i.e. they did not increase with their increase. Several health and safety precautions and environmental control techniques can be used to lessen the effects of sand and dust storms. Although it is unreasonable to take action to stop or prevent widespread sand and dust storms from occurring, management measures can be taken to lessen their effects.

Recent intensification of riverbed mining in the Mekong Delta revealed by extensive bathymetric surveying

Large-scale sand extraction has had significant and compounding impacts on the riverine environment of the Vietnamese Mekong Delta (VMD). Yet, effective and targeted implementation of regulations and sustainable management remains hindered by scant data availability, limiting a comprehensive understanding of the delta's sand mining scale and extent. This study assessed recent intensifying patterns of sand mining activities in the VMD mainly based on extensive bathymetric surveys carried out across 800 km2 of the VMD river channel from 2017 to 2022. Our results revealed severe riverbed deepening across the VMD, with the upper reaches of the Hau (Bassac) River experiencing an average incision of 1.4 m from 2017 to 2022, resulting in sediment losses of 127 Mm3. Similarly, the upper reaches of the Tien (Mekong) River and the Co Chien branch showed incisions of 1.3 m and 0.7 m from 2017 to 2020, accompanied by sediment losses of 139 Mm3 and 87 Mm3, respectively. The observed spatial and temporal variability in incisions, along with widespread sand mining pockmarks along the riverbed profiles, provide strong evidence of the significant contribution of sand mining to changes in riverbed morphology. The progressive lowering of riverbed elevation provides further evidence of the recent intensification of sand mining activities. Additionally, field surveys highlighted the proximity of perceived sites of bank collapse to pitted riverbeds, providing reliable indications of sand mining-induced erosion. Ultimately, we intend for this evidence-based assessment of sand mining activities in the VMD to contribute to informed quantitative assessments of sediment budgets and effective implementation of regulatory frameworks for sustainable sand mining in the future.

Characteristics of Co-Seismic Surface Rupture of the 2021 Maduo Mw 7.4 Earthquake and Its Tectonic Implications for Northern Qinghai–Tibet Plateau

A magnitude (Mw) 7.4 Maduo earthquake occurred on 22 May 2021 in the northern Qinghai-Tibet Plateau, with predominantly left-lateral strike-slip faulting and a component of normal faulting within the Bayan Har Block. The co-seismic surface rupture extended in a NWW direction for ~160 km with a complicated geometry along a poorly known young fault: the Jiangcuo Fault. The main surface rupture propagated bilaterally from the epicenter and terminated eastward in horsetail splays. The main rupture can be divided into five segments with two rupture gaps. Field surveys and detailed mapping revealed that the co-seismic surface ruptures were characterized by a series of left-lateral offsets, en echelon tensional cracks and fissures, compressional mole tracks, and widespread sand liquefication. The observed co-seismic left-lateral displacements ranged from 0.2 m to ~2.6 m, while the vertical displacements ranged from 0.1 m to ~1.5 m, much lower than the InSAR inverse slip maximum of 2–6 m. Based on the comprehensive analysis of the causative fault geometry and the tectonic structure of the northern Bayan Har Block, this study suggests that the multiple NWW trending sub-faults, including the Jiangcuo Fault, developed from the East Kunlun fault northeast of the Bayan Har Block could be regarded as the sub-faults of the East Kunlun Fault system, constituting a broad and dispersive northern boundary of the Block, controlling the inner strain distribution and deformation.

An explosive volcanic origin identified for dark sand in Aeolis Dorsa, Mars

Abstract Dark, windblown (eolian) sand on Mars has produced significant geologic effects throughout Martian history. Although local and regional sand sources have been identified, a primary origin, or genesis, for Martian sand has not been demonstrated. This knowledge gap was recently heightened by the discovery of widespread sand motion, implying breakdown of grains to sub-sand sizes. To address the question of sand genesis, we investigated the source(s) of sand in Aeolis Dorsa (AD), the westernmost Medusae Fossae Formation, using comparisons to sand potentially sourced from multiple regions, each connoting a different sand genesis. Our methods included comparison of (1) AD sand mineralogies with those of possible sand source features, and (2) mapped AD sand deposits and inferred emplacement directions with modeled sand deposit locations and transport pathways. The results point to a time-transgressive unit, interpreted as pyroclastic, as a source of dark sand. High-resolution images of this unit reveal outcrops with dark sand weathering out of lithified bedrock. Given the extent of interpreted pyroclastic deposits on Mars, this sand genesis mechanism is likely widespread today and operated throughout Martian history. Whereas this work identified olivine-rich sand, a range of original pyroclastic lithologies would account for the mineralogic variability of dune fields on Mars. These findings can be tested through analyses of other pyroclastic deposits and potentially by data from the NASA Curiosity rover in nearby Gale crater.

The giant 1960 tsunami in the context of a 6000‐year record of paleotsunamis and coastal evolution in south‐central Chile

AbstractThe tsunami associated with the giant 9.5 Mw 1960 Chile earthquake deposited an extensive sand layer above organic‐rich soils near Queule (39.3°S, 73.2°W), south‐central Chile. Using the 1960 tsunami deposits, together with eye‐witness observations and numerical simulations of tsunami inundation, we tested the tsunami inundation sensitivity of the site to different earthquake slip distributions. Stratigraphically below the 1960 deposit are two additional widespread sand layers interpreted as tsunami deposits with maximum ages of 4960–4520 and 5930–5740 cal BP. This >4500‐year gap of tsunami deposits preserved in the stratigraphic record is inconsistent with written and geological records of large tsunamis in south‐central Chile in 1575, 1837, and possibly 1737. We explain this discrepancy by: (1) poor preservation of tsunami deposits due to reduced accommodation space from relative sea‐level fall during the late Holocene; (2) recently evolved coastal geomorphology that increased sediment availability for tsunami deposit formation in 1960; and/or (3) the possibility that the 1960 tsunami was significantly larger at this particular location than other tsunamis in the past >4500 years. Our research illustrates the complexities of reconstructing a complete stratigraphic record of past tsunamis from a single site for tsunami hazard assessment.

Late Paleozoic (Late Mississippian–Middle Permian) sediment provenance and dispersal in western equatorial Pangea

Late Mississippian to middle Permian sediment-dispersal networks of regional to continental scale in western equatorial Pangea, depicted here in a series of paleogeographic maps, developed in response to temporally and spatially changing influences of climate, eustasy, and a continent-wide late Paleozoic orogenic system. The orogenic system included linked Alleghanian, Ouachita-Marathon-Sonora collisional belts and associated foreland basin systems on Laurentia and magmatic arcs on Gondwana, intracratonic basement uplifts and basins of the Ancestral Rocky Mountains, flexural arches and intracratonic basins of the US midcontinent region, and basins and uplifts of the southwestern Laurentian transcurrent continental margin. Consideration of new and published U-Pb detrital-zircon datasets permits delineation of Laurentian sediment-dispersal networks of the developing supercontinent. The Transcontinental Arch deflected Late Mississippian transcontinental rivers with Alleghanian headwaters toward the southern midcontinent and nascent, deep-marine foreland basins along the Ouachita collision orogen. Pennsylvanian rivers likewise headed in the Alleghanian Orogen, transporting sediment southwest across the midcontinent and along the Alleghanian foreland basin to empty into the Arkoma Basin and Fort Worth Basin, which also received voluminous sediment from Gondwana and the Ouachita Orogen. Concomitantly, major growth of Ancestral Rocky Mountains uplifts yielded basement-derived sediment, much of which was retained in local flexural basins. Increased aridity drove ascendant eolian transport in early Permian (Artinskian) time, just as lowstand desiccation of a midcontinent seaway exposed unconsolidated silt and sand derived from eastern, western, and southern sources in an extensive interior desert sink. Eolian transport within the interior desert further mixed and deflated the already-cosmopolitan sediment, pushing it southwest toward the Permian Basin and westward beyond the Ancestral Rocky Mountains. Intercepted by newly developed monsoonal circulation, the deflated sediment came to reside in erg systems along the western marine margin of Pangea. Subtropical Pennsylvanian transcontinental fluvial networks were similar to those of modern big river systems of the eastern and midcontinent United States that drain toward the Gulf of Mexico. In contrast, Permian drainage networks yielding sediment to a continental desert more resembled Pleistocene sediment routes of the Arabian Plate; there, intermittent wadis draining western rift highlands and big rivers of the Mesopotamian foreland contribute sediment to Arabian eolian sands via zonal and monsoonal surface winds to create widespread sand seas of mixed Eurasian and Arabian provenance.

The status and ecology of the sand cat in the Uruq Bani Ma’arid Protected Area, Empty Quarter of Saudi Arabia

Abstract The sand cat is one of the world’s least studied small cats. Our camera-trap survey, one of the largest undertaken in a desert system, generated over 1500 images of the species across 100 camera-traps distributed systematically over the 2400 km2 core area of the Uruq Bani Ma’arid Protected Area of the Empty Quarter, Saudi Arabia. The study revealed a much more significant and widespread sand cat population in the ecosystem than previously understood. Sand cats were detected across one-third of the core area in all major habitats, comprising escarpment plateau, sand dunes and interdunal gravel valleys. The species showed a marginal preference for the interior parallel dune system with interspersed gravel valleys where they also preferred sand dunes over the gravel valley in the hot season. There was no evidence of strong spatial interactions with other predators. The ecosystem’s larger predators (Arabian red fox and honey badger, and all records of wild and feral cats) were primarily associated with the escarpment plateau. The smaller Rueppell’s fox was the only other carnivore more consistently present in the main dune system. Sand cats were strictly nocturnal and 14% more active in the hot season than the cool season.

Cryptic species and co‐diversification in sand scorpions from the Karakum and Kyzylkum deserts of Central Asia

AbstractLittle is known about species diversification within the deserts of Central Asia. For example, the degree of lineage divergence and timing of population differentiation, as well as potential biogeographic barriers driving diversification, are nearly unknown. Here, we analysed a multi‐locus data set for a widespread sand scorpion (Mesobuthus gorelovi) to evaluate cryptic species diversity and phylogeographic patterns across the Karakum and Kyzylkum deserts. We also combined these data with previously published sequence data to test for a signal of co‐diversification. A consensus species delimitation approach indicated that the widespread M. gorelovi is likely composed of up to five distinct species that began to diversify at the Miocene–Pliocene boundary. We observed shared patterns of lineage divergence across the Amu Darya River region in three scorpion taxa and found support for a shared history of assemblage diversification across this biogeographic barrier. Thus, major river systems appear to facilitate diversification among desert scorpions.

Young colonization history of a widespread sand dollar (Echinodermata; Clypeasteroida) in western Taiwan

Arachnoides placenta is the most common sand dollar species in western Taiwan. Due to its lack of fossil record, the arrival of this species in Taiwan could not be estimated until now. Fragments of A. placenta was recovered sorting through a 1981- museum collection of sand dollars collected off Mailiao county, western Taiwan. Additional echinoderm specimens were recovered from Holocene sediments nearby, but no fragments of A. placenta were found, indicating a decline in the living population. A total of 11 echinoderm samples, including five specimens that were assigned to A. placenta with certainty, were sent for radiocarbon dating. Results showed that studied echinoderm fragments range from modern (after 1950) to as old as 2680 ± 55 a BP and the oldest date is from A. placenta. It is evident that Taiwan is an active migration front for A. placenta due to the relatively young arrival age for this pandemic species which is widespread in the Indo-West Pacific region. Additionally, the DNA sequence, including the cytochrome c oxidase subunit I (cox1) gene, of the species was obtained to conduct the first molecular phylogenetic study of sand dollars in Taiwan.

Single-crystal hematite (U–Th)/He dates and fluid inclusions document widespread Cryogenian sand injection in crystalline basement

The Tavakaiv Quartzite (informal) in Colorado, USA, is one of the world's largest basement-hosted clastic injectite systems and provides a glimpse into the tectonic and near-surface environment of ancient North America. The age, origin, and significance of Tavakaiv injectites has been debated for over a century, owing to inherent difficulties with assigning absolute age constraints to unfossiliferous sandstone intrusions. Here, we apply an innovative combination of single-crystal hematite (U–Th)/He thermochronometry and fluid inclusion microthermometry to hematite mineralization associated with the injectites to document the age and ambient fluid conditions of Tavakaiv injectite formation. Our approach confirms individual hematite crystals comprising commonly analyzed polycrystalline aggregates are the He diffusion domains and that hematite (U–Th)/He closure temperature increases with crystal size. We apply apatite and zircon fission-track thermochronometry to the Tavakaiv Quartzite and host rock to account for the consequences of Phanerozoic orogenic episodes on the hematite (U–Th)/He dates and explain the observed trends between hematite He date and crystal size. Our results indicate that hematite formed 676 ± 26 million years ago (arithmetic mean date ±1σ), constraining the timing of the Tavakaiv injection event. Fluid inclusion studies reveal that this mineralizing fluid was at least 200 °C and saline (>20 wt% CaCl2 equiv.). Comparison of new and previously published detrital zircon U–Pb age populations from quartzite samples yield a sediment source common to Tavakaiv bodies across a broader region and illuminate the greater areal extent of the Cryogenian injection event. We interpret that formation of basement-penetrating fracture arrays was associated with crustal extension within Rodinia at this time. This was accompanied by sand remobilization that promoted widespread sand injection within horsts bounding Neoproterozoic rift basins. The resulting sand injectites served as permeable pathways for contemporaneous circulation of saline groundwater, driven by fluid gradients in extensional and/or transtensional basins.

Aeolian saltation on Mars at low wind speeds

AbstractLaboratory experiments indicate that the fluid threshold friction speed, u*tf, required to initiate fully developed aeolian saltation is much higher on Mars than on Earth. A discrepancy exists between Mars climate models that do not predict winds this strong and observations that sand‐sized particles are indeed moving. This paper describes how wind friction speeds well below u*tf, but above the impact threshold, u*ti, required to sustain saltation, can initiate sustained saltation on Mars, but at relatively low flux. Numerical experiments indicate that a sand grain on Mars mobilized sporadically between u*ti and u*tf will develop, over fetch lengths longer than generally available within low‐pressure wind tunnels, trajectories capable of splashing grains that propagate saltation and collectively form a cluster of saltating grains that migrate downwind together. The passage of a saltation cluster should leave behind a narrow zone of affected surface grains. The cumulative effect of many clusters represents a low‐flux phenomenon that should produce slow changes to aeolian bedforms over periods in which winds remain close to u*ti and never or rarely reach u*tf. Field evidence from small impact ripples along rover traverses is consistent with effects of saltation at these low friction speeds, without obvious evidence for events ≥u*tf. The potential utility of this grain mobility process is that it can operate entirely at more common winds well below u*tf and so help explain widespread sand movements observed on Mars wherever evidence might be mostly absent for u*tf being exceeded.

The ecological-hydrochemical condition of the Ryazan Meshchera lakes

Identifies the main hydro-chemical parameters of some lakes of the Ryazan Meshchera, including lakes Laskowski, located in the immediate vicinity of the centre. All lakes are of glacial origin and were formed in specific environmental and geochemical conditions of Polesie landscapes. They are characterized by widespread fluvioglacial and ancient alluvial sand deposits, a kind of combination of coniferous forests with marshy areas, a relatively small anthropogenic load. The research established that extremely low TDS water of all lakes, and respectively detected very small concentrations of major macro - and micronutrients. Against this background, a large presence of iron in lake water, which is related to the geochemical background. The signs of pollution, including domestic sewage, in the studied lakes was not detected.

Sedimentology and composition of sands injected during the seismic crisis of May 2012 (Emilia, Italy): clues for source layer identification and liquefaction regime

In May 2012 widespread sand blows formed along buried channels in the eastern sector of the Po Plain (Northern Italy) as a consequence of a series of seismic events with main shocks of Mw 6.1 and 5.9. At San Carlo (Ferrara) a trench dug a few week after the earthquakes exposed sand dikes cutting through an old Reno River channel–levee system that was diverted in the 18th century and was deposited starting from the 14th century (unit A). This sequence overlies a Holocene muddy floodplain deposits and contains scattered sandy channel deposits (unit B) and a Pleistocene channel sand unit (unit C). Sands with inverse and normal grading, concave layering and vertical lamination coexisting along the dikes suggest multiple rhythmic opening and closing of the fractures that were injected and filled by a slurry of sand during the compression pulses, and emptied during the extension phase. The pulse mechanism may have lasted for several minutes and formed well stratified sand volcanoes structures that formed at the top of the fractures. Sands from dikes and from the various units show well defined compositional fields from lithoarenitic to quartz-feldspar-rich compositions. Sands from the old Reno levee and channel fill (unit A) have abundant lithic fragments derived from the erosion of Apennine sedimentary carbonate and terrigenous successions. Composition of the sand filling the dikes show clear affinities with sand layers of the old Reno River channel (Unit A) and clearly differ from any sand from deeper Holocene and Pleistocene layers (Unit B and C), which are richer in quartz and feldspar and poorer in sedimentary lithic fragments. Sorting related to sediment flux variations did not apparently affect the sand composition across the sedimentary structures. Textural and compositional data indicate that the liquefaction processes originated from a relatively shallow source consisting of channel sands located within Unit A at 6.8.to 7.5m depth.

Sustainably managing natural resources and the need for construction materials in Pacific island countries: The example of South Tarawa, Kiribati

AbstractThe growing demand for construction materials in South Tarawa, a remote atoll in the South Pacific, provides an example of the environmental and social challenges associated with the use of non‐renewable resources in the context of small island countries threatened by coastal erosion and climate change. In many small Pacific island countries, the availability of construction materials is limited, with the majority mined from beaches and coastal reefs in an unsustainable manner. Growing demand for construction aggregates is resulting in more widespread sand mining by communities along vulnerable sections of exposed beach and reefs. This has serious consequences for coastal erosion and impacts on reef ecosystem processes, consequences that cannot be easily managed. Construction materials are also in high demand for infrastructure projects which are financed in part with support from international development agencies and donors. This paper reviews the various challenges and risks that aggregate mining poses to reefs, fish, and the coastal health of South Tarawa and argues that the long term consequences from ad hoc beach/reef mining over large areas are likely to be far greater than the impacts associated with environmentally sustainable, organized extraction. The paper concludes with policy recommendations that are also relevant for neighbouring island countries facing similar challenges.

The dynamics of a frictionally-dominated Amazonian estuary

The hydrodynamics, morphology and sedimentology of the Taperaçu estuary were investigated. This is one of several estuaries located within the largest mangrove fringe in the world, bordering the Amazon region, subject to a macrotidal regime and regionally atypical negligible fresh water supply. The results reveal widespread sand banks that occupy the central portion of the estuarine cross-section. Well-sorted very fine sandy sediments of marine origin prevail. Shorter flood phases, with substantially higher current velocities, were observed in the upper sector of Taperaçu, as expected for a shallow, friction-dominated estuary. However, ebb domination can be expected for estuaries with large associated mangrove areas and substantial estuarine infilling, both of which situations occur on the Taperaçu. The tidal asymmetry favoring flood currents could be the result of the absence of an effective fluvial discharge. Furthermore, it was observed that the Taperaçu is connected by tidal creeks to the neighboring Caeté estuary, allowing a stronger flux during the flood and intensifying the higher flood currents. As a whole, the results have shown a complex interaction of morphological aspects (friction, fluvial drainage, connections with neighbor estuaries, infilling and large storage area) in determining hydrodynamic patterns, thus improving the understanding of Amazon estuaries.

Stowing Mining Technology in the Northwest Ecologically Fragile Areas

Northwest China is rich of coal energy. Mining activities bring serous impact on the environment and scarce water resources because of its shallow buried and severe mining impact. Stowing mining is one of the most effective measures to control strata movement and reduce surface subsidence. Based on the local surface widespread wind-blown sand for aggregate and combined with the knife pillar mining，this paper introduces the stowing mining technology.

Images- Pulmonary Alveolar Microlithiasis (PAM)

Pulmonary alveolar microlithiasis (PAM) is a rare disease of unknown origin in which calcific concretions collect in alveolar spaces. No known cause for the disease had been identified and there appears to be no systemic disorder of calcium metabolism. Plain chest X-ray shows a white lung consisting of fine sandlike micro calcification diffusely scattered throughout both lungs with high density at lung basis. CT reveals ground glass haze with inter and intra lobular septal thickening suggestive of crazy paving pattern. We here report the typical X-ray and HRCT images of a case of PAM: a rare disease characterized by wide spread sand like intra alveolar calcifications.

El tsunami del 22 de abril de 1991 en Bocas del Toro, Panamá

A local tsunami was observed few minutes after the 22 April 1991 (MS= 7,5) earthquake, along the Caribean coast of Costa Rica and Panama. This study summarizes eyewitness accounts and field observations from 16 sites along the afected coast, from Gandoca, near the Costa Rica - Panama border to Bastimentos Island, Panama. Little or no tsunami damage occurred because the fringing coral reefs served as natural protection barriers. The maximum run up height was between 2.0 and 2.5 m, and inundation and coastal flooding extended up to 200 m inland in some locations. In some parts the coastal subsidence amplified the run up effects. Widespread sand deposition near the Costa Rica - Panama border is similar to eyewitness accounts of the 7 May l822 earthquake, suggesting that the return time for tsunamogenic events similar to the April 22, I991 event may be on the order of less than two hundred years in this region.

Palaeoclimate change drove diversification among isolated mountain refugia in the Australian arid zone

Refugia featured prominently in shaping evolutionary trajectories during repeated cycles of glaciation in the Quaternary, particularly in the Northern Hemisphere. The Southern Hemisphere instead experienced cycles of severe aridification but little is known about the temporal presence and role of refugia for arid-adapted biota. Isolated mountain ranges located in the Australian arid zone likely provided refugia for many species following Mio/Pliocene (<15 Ma) aridification; however, the evolutionary consequences of the recent development of widespread sand deserts is largely unknown. To test alternative hypotheses of ancient vs. recent isolation, we generated a 10 gene data set to assess divergence history among saxicolous geckos in the genus Heteronotia that have distributions confined to major rocky ranges in the arid zone. Phylogenetic analyses show that each rocky range harbours a divergent lineage, and substantial intraspecific diversity is likely due to topographic complexity in these areas. Old divergences (~4 Ma) among lineages pre-date the formation of the geologically young sand deserts (<1 Ma), suggesting that Pliocene climate shifts fractured the distributions of biota long before the spread of the deserts.