On the frontier of the Western Shire,British Central Africa

Superficial deposits (residual, colluvial, alluvial) are important as environmental resources in tropical environments. An understanding of their formation through varying time periods is essential to a correct interpretation of their economic and hazard potentials. This requires an integration of process studies with a reconstruction of longer term development. Saprolite formation is considered over 10⁵‐10⁷ yr, while colluvial and alluvial sediments are commonly Late Quaternary (10³‐10⁵ yr) in age. The importance of Quaternary environmental changes in the humid tropics to an understanding of heavy mineral placer deposits in West Africa and Indonesia is illustrated. It is concluded that geomorphologists can often make their most important contributions to developing areas by offering a sound interpretation of landsurfaces and their underlying deposits for engineers, geologists and pedologists, with whom a close working relationship is essential.     

Field Measurements of Wave Characteristics on a Near‐Horizontal Shore Platform,Mahia Peninsula,North Island,New Zealand

Waves are an important process responsible for the initiation and subsequent development of intertidal shore platforms. However, few field studies to date have described wave processes on shore platforms. A field experiment was conducted using an across‐shore array of wave gauges, including a directional sensor, on a near‐horizontal platform at Mahia Peninsula, North Island, New Zealand. Results show that the platform is very efficient in filtering wave energy at gravity wave frequencies (>0.05 Hz), with 40–80% reduction in wave height measured across the 140 m wide platform. By contrast, infragravity waves are present on the platform and increase in magnitude towards the cliff toe. Directional wave analysis indicates that wave reflection is mainly restricted to infragravity wave frequencies, demonstrating the differences in gravity and infragravity wave behaviour on the platform studied. Results indicate that, under fair weather conditions, the role of waves as an agent of cliff toe erosion is likely to be limited at present, although they are probably important for removing sediments accumulated at the cliff toe. The observed increase in infragravity wave energy towards the cliff toe implies that these long‐period waves may be important geomorphic agents on shore platforms.     

Geographers in Their Ivory Tower: Academic Geography and Popular Geography in Paris 1931

Abstract: French academic geography achieved remarkable success during the 1920s making Paris an appropriate location for the XIIIth International Geographical Congress to meet in 1931. These scholarly activities were counterpoised by expressions of an exotic 'popular geography' at the great Exposition Coloniale staged in the French capital at the same time. At the Congress, French academics displayed their research achievements in denudation chronology, rural settlement studies and cartography, extending their work from the Hexagon to parts of the Empire. Patronage by leading professors in Paris and Grenoble clearly played a vital role in shaping the discipline. The location and content of excursions for visiting scholars also highlighted French achievements and suggested what remained to be done. Scrutiny of activities at the XIIIth IGC reveals a profession whose official pronouncements appear isolated from the momentous economic and political changes triggered by global depression at that time.     

Geoarchaeology of Beirut's ancient harbour,Phoenicia

This paper presents geoarchaeological results from the ancient harbour of Beirut (Lebanon). As at Sidon, knowledge of Beirut's ancient tell has advanced significantly over the past decade, thanks namely to redevelopment of the city centre and excavations centred on the modern port. In spite of this research, understanding of the city's coastal palaeoenvironments during antiquity is poor. Buried Iron Age harbourworks presently 300 m from the sea attest to pronounced coastal changes during the past 3000 years. These processes have been significantly accentuated during the last two centuries by redevelopment of the port, which remains in use some 5000 years after its foundation. Here we elucidate the coastal stratigraphy east and west of the Bronze Age tell to yield new insights into the evolution of the Beirut seaboard, in addition to the complex history of human–environment interactions. These chronostratigraphic data are subsequently used to (1) precisely locate the main anchorage haven during antiquity; and (2) propose a chronology for its evolution.     

A River Runs Through It: Morphological and Landowner Sensitivities Along the Upper Missouri River, Montana, USA

Landowners along the Missouri River in Montana believe that the operation of Fort Peck Dam has initiated bank erosion, thus threatening agricultural development within the region. Their concerns have been heightened by proposals to increase discharge in order to enhance fisheries and wildlife interests. Geomorphological evaluation indicates that bed degradation and bank erosion have declined since construction of the dam, and the channel is now approaching dynamic equilibrium; public sensitivity to the proposed change is greater than the morphological sensitivity of the river. Sustainable management of the Missouri is now based on strategies that place more emphasis on partnership with local citizens.     

Geoarchaeology of Sidon's ancient harbours,Phoenicia

Geoarchaeological data from Sidon's ancient harbour areas elucidate six evolutionary phases since the Bronze Age. (1) At the time of Sidon's foundation, during the third millennium BC, medium sand facies show the city's northern and southern pocket beaches to have served as proto-harbours for Middle to Late Bronze Age societies. (2) Towards the end of the Late Bronze Age and the Early Iron Age, expanding international trade prompted coastal populations into modifying these natural anchorages. In Sidon's northern harbour, transition from shelly to fine-grained sands is the earliest granulometric manifestation of human coastal modification. The lee of Zire island was also exploited as a deep-water anchorage, or outer harbour, at this time. (3) Although localised sediments evoke developed port infrastructure during the Phoenician and Persian periods, high-resolution reconstruction of the northern harbour's Iron Age history is problematic given repeated dredging practices during the Roman and Byzantine periods. (4) Fine-grained silts and sands in the northern harbour are coeval with advanced Roman engineering works, significantly deforming the coastal landscape. Bio- and lithostratigraphical data attest a leaky lagoon type environment, indicative of a well-protected port. (5) The technological apogee of Sidon's northern harbour is recorded during the late Roman and Byzantine periods, translated stratigraphically by a plastic clays unit and brackish lagoon fauna. (6) A final semi-abandonment phase, comprising coarse sand facies, concurs silting up and a 100–150 m progradation of the port coastline after the seventh century AD. We advance three hypotheses to explain these stratigraphic data, namely cultural, tectonic and tsunamogenic. Finally, our results are compared and contrasted with research undertaken in Sidon's sister harbour, Tyre.     

Fracture‐focused fluid flow in an acid and redox‐influenced system: diagenetic controls on cement mineralogy and geomorphology in the Navajo Sandstone

Differential cement mineralogy is influenced by depositional textures, structural deformation, pore fluid chemistry, and ultimately influences landscape evolution by introducing heterogeneities in erodibility. In Southern Utah, the region West of the Kaibab uplift known as Mollies Nipple (Mollies) in Grand Staircase‐Escalante National Monument exhibits a complex history of fluid–sediment interactions, which has resulted in a localized zone of anomalous diagenetic iron sulfate (jarosite) mineralogy in a well‐exposed dune–interdune deposit within the Navajo Sandstone. Mineralogy and geochemistry of cements within this region are examined using reflectance and imaging spectroscopy, field investigations, microscopy, and whole‐rock geochemical analyses. These data show that the in‐situ jarosite cement is localized to a plane along the highest ridge of the butte, providing an armor along with other secondary cements, which controls the butte's geomorphic evolution. The jarosite cement is associated with other mineralogies suggesting that the sulfate was one of the latest fluid‐related precipitates in the paragenetic sequence. It was preceded by a regional bleaching event, precipitation of clay cements, some localized concretionary iron oxide precipitation, and formation of deformation bands. At least one generation of dense iron oxide mineralization is associated with cataclastic brittle deformation predating the sulfate precipitation. Trace element geochemistry of cements shows certain metal oxide populations associated with extremely high (>2000 ppm) arsenic values. We interpret the combination of spatial mineral distribution, observed paragenetic sequence, and trace element geochemistry to suggest this region experienced acid sulfate diagenesis along fracture‐controlled fluid conduits related to weathering of proximal, unidentified, sulfides, or H₂S associated with deep source beds. Jarosite is highly soluble, and its presence suggests that abundant fluid flow has not occurred in this region since its formation. This terminal cement‐forming event must have occurred prior to sandstone exhumation and erosion to form the current extreme landscape at Mollies. This site exhibits the influence that fluid geochemistry, sedimentary mineralogy, and structural fabric have on geomorphic evolution.     

Preliminary U-series and Thermoluminescence dating of excavated deposits in Liang Bua sub-chamber,Flores, Indonesia

We report the results of a test excavation of deposits in a limestone cave sub-chamber located beneath the main chamber of Liang Bua, Flores, Indonesia; the discovery site of the small hominin species, Homo floresiensis. Well-preserved remains of extinct Pleistocene fauna and stone artefacts have previously been identified on the surface of a sediment cone within the sub-chamber. Our excavation of the deposits, at the base of the sediment cone in the sub-chamber (to 130 cm depth) yielded only a few fragmentary bones of extant fauna. Uranium/Thorium (U-series or U/Th) dating of soda straw stalactites excavated from 20 to 130 cm in depth demonstrates that the excavated sediments were deposited during the Holocene. Red Thermoluminescence (TL) dating of the sediments at the base of the excavation (130 cm depth) indicates these sediments were last exposed to sunlight at 84 ± 15 ka (thousand years), similar to red TL ages of cave sediments from the main chamber. Together, these results indicate that the surface faunal remains, which are morphologically analogous to Pleistocene finds from the main chamber excavations, were transported to the sub-chamber relatively recently from the main chamber of Liang Bua and probably originated from conglomerate deposits at the rear of the cave and from deposits around the front entrance. There is no evidence for hominin occupation of the sub-chamber, instead it seems to have acted as a sink for cultural materials and fossil remains transported from the surface via sinkholes. Despite the small number of finds from the test excavation, it is possible that more extensive excavations may yield additional transported cultural and faunal evidence at greater depths.     

Environmental changes in the Maryut lagoon (northwestern Nile delta) during the last ∼2000 years

Here, we interpret the evolution of Maryut lagoon (Egypt) during the past ∼2000 years. Chronostratigraphy and laboratory analyses have enabled us to identify four main phases since the 3rd century AD: (1) a fluvial-dominated lagoon between the 2nd–3rd and the 8–9th centuries cal. AD; (2) a gradual desiccation of the lagoon toward a sebkha-like environment from the 9–10th to the 13th centuries cal. AD; (3) a fluvial-dominated lagoon from the 13th century cal. AD; and (4) a second gradual desiccation between the 17th and the 18th centuries cal. AD. The general aridification trend described throughout the study period may be linked to the gradual decline of the Canopic branch, which supplied the Maryut lagoon with freshwater. Nonetheless, at shorter timescales, the different phases of lagoon aridification and flooding coincide with land abandonment and irrigation works in the region. It is suggested that the history of the Alexandria countryside has been a key driver in shaping the environmental history of the Maryut during the past ∼2000 years.     

Landscapes at the Periphery of Glacierization – Retrospect and Prospect

This paper reviews the evolution of palaeoglaciological reconstructions in regions at the periphery of glacierization, where an improved understanding of the role of glacial thermal regime has helped refine the delimitation of ice sheet maxima. Also significant has been the recognition in numerical models that some areas, especially ice sheet marginal zones, are subject to short periods of ice occupancy and hence that glacial landsystem signatures can be extremely subtle. This is compounded wherever cold-based conditions dominate during early stages of ice sheet recession, giving rise to a landform imprint typical of peripheral regions and hence often misinterpreted as unglaciated or glaciated only by older glaciations. Subtle landform imprints include meltwater channels, thin glacigenic veneers or scattered erratics and modified tors. More substantial glacigenic landform-sediment assemblages (‘drift belts’) do not always represent ice sheet maxima but instead may record significant changes in thermal regime, possibly linked to periods of ice-marginal stabilization. Some upland areas that lie beyond the traditionally demarcated limits of glaciation (e.g. Dartmoor in SW England) may contain subtle evidence of satellite ice cap development which has been overlooked due to the strong periglacial landform signature.