Shoreline migration and beach-nearshore sand balance over the last 200 years in Haifa Bay (SE Mediterranean)

Several researchers have investigated morphological changes on the south-eastern Mediterranean coast during the late Holocene. However, very few of these studies include quantitative data covering the last 200 years. In this study, topographical maps, nautical charts and aerial photographs are used to estimate the shoreline migrations and beach–nearshore sand balance over the last 200 years in Haifa Bay, Israel, the northernmost final depositional sink of the Nile littoral cell. The findings reflect two main periods. During the first period, between 1799 and 1928, human intervention along the bay’s coast was negligible, a significant coastal expansion of ∼50 to 150 m (averages of 0.4–1.2 m/year) was measured, and sand accumulation was estimated at ∼70,000 m³ annually in the beach–nearshore area. A dramatic change in the sedimentological pattern was observed during the second period, between 1928 and 2006, following the completion of Haifa Port’s main breakwater (1929–1933). During this period, most of the bay’s coast was in a steady state, with seasonal fluctuations of less than about ±20 m, and slight erosion of ∼7,000 m³ annually. These findings are consistent with previous studies which conclude that from approximately 4,000 years ago until the construction of Haifa Port, sea level remained relatively stable, and a continuous accumulation of Nile-derived sand dried up the Zevulun Plain and shifted the Haifa Bay shoreline westwards to its present location. This long-term trend ceased after completion of the Haifa Port main breakwater.     

A three-dimensional mechanistic-empirical model for geocell-reinforced unpaved roads

Geocell is a three-dimensional geosynthetic product that was originally developed to confine granular bases and minimize permanent deformation of unpaved roads. Many laboratory and field tests have demonstrated the effectiveness of geocell reinforcement in roadway constructions. However, the lack of a well-established design method that can quantify the benefit of geocell reinforcement has greatly limited the application of geocell in roadways. This paper presents the development of a three-dimensional mechanistic-empirical (M-E) model for geocell-reinforced unpaved roads. The constitutive equation for the tangential resilient modulus of the base material was derived under a general three-dimensional condition. Two analytical models were introduced to estimate the compaction- and repeated load-induced residual stresses in the base layer. These analytical models consider the material properties and construction effects in a rational way thus can be used for various situations. Finally, the proposed M-E model was validated against the test results from four unpaved road sections. Comparisons between the calculated results and the test data show that the three-dimensional M-E model effectively simulated the permanent deformation behavior of geocell-reinforced unpaved roads under a large number of load repetitions, given that the unpaved road was stable under a repeated load.     

On the African rift system,theoretical and experimental study

The East African rift system is a product of two separate activities. An ancient process (Precambrian?) resulted in brittle crustal fracture, a deep vertical tensional feature. This defined the principal fracture pattern of the continent. It was initiated by an upward diapiric stress and propagated laterally according to the principles of elastic fracture and bifurcation. Later (Jurassic-Recent) horizontal and vertical multi-stage forces caused tectonic displacements along the ancient fractures and the present rift pattern was derived. As opposed to previous models, the present concept is compatible with many conflicting opinions of previous workers (e.g. indications of tensional versus compressional or vertical forces), and is capable of explaining many moot questions.     

Interpretation on the basis of Hertzian theory of a spiral carbonatite structure at Homa Mountain, Kenya

It is demonstrated that a cone fracture can be produced in a brittle material by a liquid “indenter”. Cone fractures of carbonatite structures can be interpreted on the basis of the Hertzian fracture theory. Tensile stresses are most important in initiating cones at shallow depths and shear stresses start cone fractures at great depths. Four stages of cone fracture can be observed in the Homa Mountain area. The spiral cone fracture at Homa Mountain and several other ring structures can be looked upon as an inherent feature of these structures and perhaps spiral cone fractures are more common than has been thought before. Twin centres can also be explained on the basis of the Hertzian theory.     

Reevaluating the tectonic uplift of western Mount Carmel, Israel, since the middle Pleistocene

Reevaluation of geological and archaeological evidence from western Mount Carmel constrains its maximal tectonic uplift since the Middle Pleistocene. Tabun Cave, presently 45 m above sea level (asl), revealed human occupation from about 600 ka to 90 ka before present. The 25 m thick archaeological strata at Tabun are composed of laminated fine sand, silt and clays. Moreover, no marine deposits were found in Tabun or nearby caves. Since sea level in the last 600 ka reached a maximal of 5 to 10 m asl, Tabun Cave could not have been uplifted since then by more than 35 to 40 m, that is a maximal average rate of 58 to 67 mm/ka.     

Vegetation as a major conductor of geomorphic changes on the Earth surface: toward evolutionary geomorphology

Earth surface processes and landforms may have coadjusted^? with plant morphology, biomechanics and life‐history. We suggest that the colonization of land by plants at the early Silurian, and their propagation inside continents, represent critical phases of the coupling between geomorphic and biological processes on the Earth at a global scale. The consideration of this coupling involving geomorphic‐biological feedback mechanisms at the scales of ecological succession and organisms' evolution may promote the emergence of an evolutionary^? geomorphology. Copyright © 2009 John Wiley & Sons, Ltd.     

Darwinian origin of landforms

Whilst earth surface landforms evolve largely as a result of the activity of certain living organisms, the biologically driven geomorphic changes have evolutionary consequences on organisms and ecological communities. Recognition of complex biotic–abiotic feedbacks may lead to deep changes in our understanding of geomorphology. Copyright © 2007 John Wiley & Sons, Ltd.     

Drainage response to Arabia–Eurasia collision: Insights from provenance examination of the Cyprian Kythrea flysch (Eastern Mediterranean Basin)

The Cenozoic geodynamics of the north‐eastern Mediterranean Basin have been dominated by the subduction of the African Plate under Eurasia. A trench‐parallel crustal‐scale thrust system (Misis–Kyrenia Thrust System) dissects the southern margin of the overriding plate and forms the structural grain and surface expression of northern Cyprus. Late Eocene to Miocene flysch of the Kythrea (De?irmenlik) Group is exposed throughout northern Cyprus, both at the hanging‐wall and foot‐wall of the thrust system, permitting access to an extensive Cenozoic sedimentary record of the basin. We report the results of a combined examination of detrital zircon and rutile U–Pb geochronology (572 concordant ages), coupled with Th/U ratios, Hf isotopic data and quantitative assessment of grain morphology of detrital zircon from four formations (5 samples) from the Kythrea flysch. These data provide a line of independent evidence for the existence of two different sediment transportation systems that discharged detritus into the basin between the late Eocene and late Miocene. Unique characteristics of each transport system are defined and a sediment unmixing calculation is demonstrated and explained. The first system transported almost exclusively North Gondwana‐type, Precambrian‐aged detrital zircon sourced from siliciclastic rock units in southern Anatolia. A different drainage system is revealed by the middle to late Miocene flysch sequence that is dominated by Late Cretaceous–Cenozoic‐aged detrital zircon, whose age range is consistent with the magmatic episodicity of southeast Anatolia, along the Arabia–Eurasia suture zone. Deposition of these late Miocene strata took place thereupon closure of the Tethyan Seaway and African–Eurasian faunal exchange, and overlap in time with a pronounced uplift of eastern Anatolia. Our analytical data indicate the onset of prominent suture‐parallel sediment transport from the collision zone of south‐eastern Anatolia into the Kyrenia Range of northern Cyprus, marking the drainage response to the continental collision between Arabia and Eurasia.     

Tectonic juxtaposition of blueschists and greenschists in Sifnos Island (Aegean Sea)—implications for the structure of the Cycladic blueschist belt

In the Cyclades, kilometre-thick high-pressure rock sequences, displaying blueschist- and eclogite-facies mineral assemblages, overlie a rock sequence which was thoroughly overprinted in the greenschist and amphibolite facies during its exhumation. Both rock sequences, subducted and metamorphosed at high-pressures in Eocene times, have been considered by previous workers to have been exhumed as a coherent rock unit. In contrast, it is suggested here that the preserved high-pressure rock sequences were exhumed more rapidly and prior to the underlying greenschists. Significant metamorphic, structural and geochronological discontinuities exist across the blueschist-greenschist contact and field evidence suggests that the high-pressure metamorphic rocks in Sifnos are tectonically juxtaposed above the greenschists. These two rock sequences were juxtaposed by a low-angle fault subsequent to the Oligocene-Miocene greenschist-facies overprint. Published geochronological data and petrological criteria are used to show that the high-pressure sequence cooled below 350°C when the rocks now immediately underlying it suffered a greenschist-facies overprint at temperatures of ca 450°C. The section inferred to absorb this temperature difference is now missing and it is suggested that it has been cut out by the low-angle fault.