Use of ENVISAT ASAR Global Monitoring Mode to complement optical data in the mapping of rapid broad-scale flooding in Pakistan

Envisat ASAR Global Monitoring Mode (GM) data are used to produce maps of the extent of the flooding in Pakistan which are made available to the rapid response effort within 24 h of acquisition. The high temporal frequency and independence of the data from cloud-free skies makes GM data a viable tool for mapping flood waters during those periods where optical satellite data are unavailable, which may be crucial to rapid response disaster planning, where thousands of lives are affected. Image differencing techniques are used, with pre-flood baseline image backscatter values being deducted from target values to eliminate regions with a permanent flood-like radar response due to volume scattering and attenuation, and to highlight the low response caused by specular reflection by open flood water. The effect of local incidence angle on the received signal is mitigated by ensuring that the deducted image is acquired from the same orbit track as the target image. Poor separability of the water class with land in areas beyond the river channels is tackled using a region-growing algorithm which seeks threshold-conformance from seed pixels at the center of the river channels. The resultant mapped extents are tested against MODIS SWIR data where available, with encouraging results

Scree characteristics and processes, Mt. Toowoonan, south-east Queensland

The morphology and particle size characteristics of a basaltic scree slope in the sub-coastal hill country of SE Queensland are examined. Particle size and sphericity increase significantly in a downslope direction. Investigation of scree fabric suggested the operation of two transport mechanisms on the slope, namely sliding and rolling of particles. With continued evolution of the slope, discrete particle fall diminishes in importance and debris slides and large particle rolling become important agents for particle redistribution. -Author

Analysis of a late Quaternary deposit and small mammal fauna from Nettle Cave, Jenolan, New South Wales

Volume: 117Start Page: 135End Page: 16

Mulu: the world’s most spectacular tropical karst

The Gunung Mulu karst of northern Sarawak hosts some of the longest caves in Southeast Asia. The majority of the cave passages in the Mulu karst are of phreatic origin and formed between sinks and springs as a series of loops crossing the bedding planes along which the passages formed. Water draining off the Mulu Sandstone also invaded the limestone down-dip, under a hydraulic gradient large enough to facilitate phreatic tubes rising up to 100 m to intersect other bedding planes. Rain falling directly on the\ud limestone massifs has created vertical shafts and invasion vadose passages, which intersected the drained phreatic tubes, creating a three-dimensional array of cave passages. The drainage off the sandstone also migrated laterally along the contact with the limestone to produce a series of very large cavities, whose roof collapse produced a series of very large dolines or tiankeng (sky windows)

Mass movements in cave sediments: investigation of a ~40,000-year-old guano mudflow inside the entrance of the Great Cave of Niah, Sarawak, Borneo

The West Mouth of the Great Cave at Niah in Sarawak, northwest Borneo and the North Passage that leads to the West Mouth contain large deposits of guano. The main deposit, several metres thick in places, forms the sloping floor of the entire North Passage. A mass movement deposit identified in the West Mouth, having a volume of 600 m3, originated as a guano mudflow up the North Passage in the order of 40,000 years ago. This failure of the guano slope was investigated to determine whether particular conditions or events could be identified as the most likely causes. The physical, hydrological and geotechnical properties of samples of the material were determined so that the stability of the slope could be assessed. Stability analyses showed that shearing failure of the slope would require inputs of water to the slope in quantities for which no feasible explanation can be suggested. However, the properties of the guano are similar to those of loess, indicating a high susceptibility to ‘hydrocollapse’. Very shallow failure of the slope, possibly as several smaller mudflows, could therefore have occurred due to additional water in quantities that could realistically be supplied as rainwater spray, possibly with a seismic trigger. The climate must therefore have been wetter than it is at present. These findings have implications for the interpretation of sediment deposits in other relict caves

Diversity and endemism of Murinae rodents in Thai limestone karsts

This study aims to investigate the species diversity of rodents living in karst ecosystems of Thailand. A survey has been conducted throughout Thailand, 122 karsts sampled and 477 Murinae rodents live-trapped. Phylogenetic reconstructions were carried out using two mitochondrial markers (cytb, COI). A sequence-based species delimitation method completed by the analysis of the level of genetic divergence was then applied to define species boundaries within our dataset. The phylogenetic position of Niviventer hinpoon was also investigated and sequences obtained from the holotype specimen of this species were used to reliably identify samples of N. hinpoon. A total of 12 described Murinae species, corresponding to 17 deeply divergent genetic lineages, were encountered in limestone karsts of Thailand. Our study revealed an important genetic diversity within the traditionally recognized species Maxomys surifer (four highly divergent genetic lineages), Leopoldamys neilli (two highly divergent genetic lineages) and Berylmys bowersi (two highly divergent genetic lineages). These species could be considered as species complex and require further taxonomic work. This study also provides valuable information on the distribution of the two rodent species endemic to limestone karsts of Thailand, L. neilli and N. hinpoon. Leopoldamys neilli was the most abundant species encountered in Thai karsts during our survey. However, L. neilli specimens from western Thailand are genetically highly divergent from the remaining populations of L. neilli and could represent a separate species. Niviventer hinpoon, phylogenetically closely related to N. fulvescens, is much rarer and its distribution limited to central Thailand. Most of the other captured species are typically associated with forest ecosystems. This study suggests that limestone karsts play a key role in the preservation of the rodent species endemic to such habitat, but they would also provide refuges for the forest-dwelling Murinae rodents in deforested regions

Formation of mud clast breccias and the process of sedimentary autobrecciation in the hominin-bearing (Homo naledi) Rising Star Cave system, South Africa

Unconsolidated mud clast breccia facies in the hominin-bearing (Homo naledi) Rising Star Cave, Cradle of Humankind, South Africa, are interpreted to have formed through a process termed sedimentary autobrecciation in this study. This process, by which most of the angular mud clast breccia deposits are thought to have formed autochthonously to para-autochthonously via a combination of erosion, desiccation, diagenesis and microbial alteration of laminated mud deposits, is thought to have taken place under relatively dry (i.e. non-flooded) conditions inside the cave. Subsequently, gravitational slumping and collapse was the dominant mechanism that produced the mud clast breccia deposits, which commonly accumulate into debris aprons. The mud clast breccia is typically associated with (micro) mammal fossils and is a common facies throughout the cave system, occurring in lithified and unlithified form. This facies has not been described from other cave localities in the Cradle of Humankind. Additionally, sedimentary autobrecciation took place during the deposition of some of the fossils within the Rising Star Cave, including the abundant Homo naledi skeletal remains found in the Dinaledi Subsystem. Reworking of the mud clast breccia deposits occurs in some chambers as they slump towards floor drains, resulting in the repositioning of fossils embedded in the breccias as evidenced by cross-cutting manganese staining lines on some Homo naledi fossil remains. The formation of the unlithified mud clast breccia deposits is a slow process, with first order formation rates estimated to be ca 8 x 10(-4) mm year(-1). The slow formation of the unlithified mud clast breccia facies sediments and lack of laminated mud facies within these deposits, indicates that conditions in the Dinaledi Chamber were probably stable and dry for at least the last ca 300 ka, meaning that this study excludes Homo naledi being actively transported by fluvial mechanisms during the time their remains entered the cave

Oxygen-isotope (delta18O) evidence of Holocene hydrological changes at Signy Island, maritime Antarctica

A record of Holocene hydrological changes has been produced from variations in oxygen-isotope composition (delta(18)O) preserved in freshwater lake sediments from maritime Antarctica. Small amounts (<5%) of authigenic carbonate have been extracted from a non-marl sediment core from Sombre Lake, Signy Island (60 degrees 43'S, 45 degrees 38'W). Oxygen-isotope and particle-size analysis provide a sensitive record of hydrological events in the lake arising from local and regional climate phenomena. The climate affects delta O-18 through snowpack volume and glacier activity in the catchment, lakewater temperatures, the input versus evaporation balance and the duration of seasonal lake ice cover. The most depleted (negative) delta O-18 values are associated with influxes of meltwater at times of glacier advance or retreat. Enriched (positive) delta O-18 values occur during more arid, warmer conditions with longer periods of open water in summer. This isotope record can be used to determine century-scale to decadal variability in air circulation and moisture origin. Strong similarities with other Holocene proxy records from the Weddell Sea and Antarctic Peninsula Region are apparent, including the mid-Holocene climate optimum followed by the Neoglacial and, most recently, late twentieth-century climatic warming. The oxygen-isotope record from Sombre Lake illustrates the importance of remote islands in contributing to our understanding of teleconnections in atmospheric and oceanographic circulation, sea-ice extent, air temperatures and precipitation in the Southern Ocean