Pier Lorenzo Fantozzi

Inner Northern Apennines

The Northern Apennines are a fold—thrust belt formed during the Tertiary by the tectonic superposition from W to E of the Ligurides on the Tuscan nappe and on the Tuscan metamorphic complex (Boccaletti et al., 1971; Alvarez et al., 1974; Kligfield, 1979). The ophiolite-bearing Ligurides derived from the southern extension of the Ligurian—Piedmont ocean, from which similar mafic components of the Western Alps also derive (Fig. 14.1). The Tuscan units derived from the continental palaeomargin of the Adria microplate and contain a Hercynian continental basement with its upper Carboniferous Tertiary cover (Vai, this vol., Ch. 10).

Geological mapping in northeastern Somalia (Midjiurtinia region): Field evidence of the structural and paleogeographic evolution of the northern margin of the Somalian plate

Abstract A detailed geological investigation of the continental margins of northeastern Somalia, in land areas contiguous to major oceanic structures (e.g. the Alula–Fartaq fracture zone), was carried out from 1988 to 1991, and the results are given in the enclosed 1:200,000 geological map, derived from photointerpretation and fieldwork at the scale 1:50,000. With respect to the rift of the Gulf of Aden, the stratigraphic sequences illustrated in the map have been distinguished as pre- and syn- and post-rift sediments. The pre-rift sediments rest on the low-grade ?pre-Palaeozoic phyllites and pan-African granitic intrusions and consist of sedimentary cover of continental, lagoon and marine facies ranging in age from Dogger to Eocene. Cretaceous–Eocene sediments pass eastward into clastic and marly deposits of the pelagic domain of the Indian Ocean. The syn- and post-rift sequences ranging in age from Oligocene to Miocene crop out only in narrow “en-echelon” basins striking WNW–ESE along the coast of the Gulf of Aden. The deposits belonging to the syn- and post-rift sequences are discordant and transgressive over the Meso–Cenozoic substratum and are composed by organogenic neritic marine, lagoonal and continental deposits. The tectonic setting of the area is characterized by half-graben bordered by faults with displacements of several kilometres striking WNW–ESE. Faults bordering contiguous half-graben systems often dip in opposite directions, so that in the transition area between different ones a “transfer” or “accommodation” zone develops; the zones are on the landward projection of the oceanic fracture zones, whilst the syn-rift basins are on the landward projection of the oceanic ridge. Based on our fieldwork the following reconstruction is put forward: 1. During the Early Oligocene the Afro-Arabian plate underwent a phase of intense faulting which led to the formation of small syn-rift basins elongated in the WNW–ESE direction, separated by transfer zones and structural highs. 2. Progressive crustal extension led to the formation of spreading centres of oceanic crust corresponding to earlier syn-rift basins. The fracture zones linking spreading centres formed in alignment with continental transfer zones.

Geology of the Mesozoic-Tertiary sedimentary basins in southwestern Somalia

Abstract Two main sedimentary basins can be recognized in southern Somalia, the NE–SW trending Mesozoic-Tertiary Somali coastal basin, and the NNE–SSW Mesozoic Luuq-Mandera basin. The two basins are separated by the Bur region where the Proterozoic-Early Paleozoic Metamorphic basement of southern Somalia outcrops. The investigated area covers part of the Metamorphic basement of southern Somalia and of the Luuq-Mandera basin, although this basement is not described in details in this paper. In the Bur region the basement outcrops discontinuously near inselbergs and monadnocks, which stand out of a blanket of recent sediments. Because of this patchy distribution and the limited areal extent of the outcrops, the structure of the metamorphic basement is difficult to reconstruct. A NW–SE trend of structures prevails and two metamorphic complexes (the Olontole and Diinsor complexes) can be recognized. The Luuq-Mandera basin is a wide NNE–SSW synclinorium, delimited to the SE by the basement high of the Bur region, and to the west by the crystalline basement high of NE Kenya (Northern Frontier district). The extreme thickness of Triassic sediments in the axial part of the basin, and the thinner and younger succession on both sides of the basin suggest that the Luuq-Mandera basin was a subsiding elongated area that was invaded by the sea in the early Mesozoic, during the dismembering of Gondwana. The Jurassic–Cretaceous succession that followed comprises two main cycles of transgression and regression; the carbonate sediments that lie at the bottom pass up section into shales, evaporites and sandstone deposits. Since late Cretaceous, continental contition prevaled, with a long phase of peneplanation, and then a general uplift, which brought about the creation of lake depressions and the capture of the Dawa river, with formation of the present Jubba valley. The main tectonic events in the study area, and throughout SW Somalia, are represented by strike-slip movements along vertical faults in the Sengif and Garbahaarrey belt. Deformation is localized within a narrow belt that extends for more than a 100 km in a NE–SW direction. The near parallelism between the fold axes and the regional orientation of faults indicates a right-lateral movements along faults. The structure of the Garbahaarrey belt consists of an anastomosing fault system that delimits elongated folded blocks, arranged in anticline–syncline structures, with subvertical axial surfaces and fold axes parallel to the main wrench faults. The orientation of folds and the typical “positive flower structure” profile of the anticlines indicate that shortening was perpendicular to the strike of the wrench, i.e. in a SE–NW direction. In the Garbahaarrey belt, strike-slip and shortening, therefore, occurred contemporaneously and led to a relative transpression between the NW and SE blocks. The observed parallelism between fold and fault orientation cannot be explained with a simple rotation of pre-existing fold axes during transpression, but can be regarded as an example of folding and strike-slip movements that occurred simultaneously but independently along frictionless faults. The faults delimiting the anticlines accommodated the strike-slip component of transpression only, whereas the compressive component led to the generation of fold axes parallel to the wrench zone. Results of the field work are summarized in two geological maps of the Gedo, Bakool, and Bay regions (1:250,000) which accompany this report (maps are attached with this issue).

How Can Childbirth Care for the Rural Poor Be Improved? A Contribution from Spatial Modelling in Rural Tanzania.

Introduction Maternal and perinatal mortality remain a challenge in resource-limited countries, particularly among the rural poor. To save lives at birth health facility delivery is recommended. However, increasing coverage of institutional deliveries may not translate into mortality reduction if shortage of qualified staff and lack of enabling working conditions affect quality of services. In Tanzania childbirth care is available in all facilities; yet maternal and newborn mortality are high. The study aimed to assess in a high facility density rural context whether a health system organization with fewer delivery sites is feasible in terms of population access. Methods Data on health facilities’ location, staffing and delivery caseload were examined in Ludewa and Iringa Districts, Southern Tanzania. Geospatial raster and network analysis were performed to estimate access to obstetric services in walking time. The present geographical accessibility was compared to a theoretical scenario with a 40% reduction of delivery sites. Results About half of first-line health facilities had insufficient staff to offer full-time obstetric services (45.7% in Iringa and 78.8% in Ludewa District). Yearly delivery caseload at first-line health facilities was low, with less than 100 deliveries in 48/70 and 43/52 facilities in Iringa and Ludewa District respectively. Wide geographical overlaps of facility catchment areas were observed. In Iringa 54% of the population was within 1-hour walking distance from the nearest facility and 87.8% within 2 hours, in Ludewa, the percentages were 39.9% and 82.3%. With a 40% reduction of delivery sites, approximately 80% of population will still be within 2 hours’ walking time. Conclusions Our findings from spatial modelling in a high facility density context indicate that reducing delivery sites by 40% will decrease population access within 2 hours by 7%. Focused efforts on fewer delivery sites might assist strengthening delivery services in resource-limited settings.

Planation Surfaces and the Long-term Geomorphological Evolution of Ethiopia

Four major planation surfaces (PS) characterize the Ethiopian geology and landscape. They were modelled near or at sea level before the Ordovician (PS1), before the Late Triassic (PS2), before the Cenomanian (PS3), and before the Oligocene (PS4). These are unconformities in the sedimentary sequence recognizable across the entire country and the surrounding regions that due to uplift can be locally exhumed to generate wide steps in the landscape. At the top of the sequence, that also corresponds to the higher parts of the highlands, the flat depositional surface of the continental flood basalts (CFB) is preserved over large areas. However, a series of deep large palaeovalleys dissecting the CFB have been recognized on the water divides of the Afar, the Main Ethiopian Rift (MER), the Southern Ethiopian Rift (SER), and the Somalian and Sudan lowlands that are the main geomorphological features of the country. The palaeovalleys testify to a radial pattern that originated from the dome created by the emplacement of the CFB. They are easily recognizable to the south of Dire Dawa and in the northern part of the country. They were modelled over the pre-volcanic bedrock but in most of the highlands were buried under later volcanic products. The deep erosion of the dome and the later volcanic filling can explain the results of the previous thermochronological investigation. Unfortunately, the thickness of the CFB could have led to the reset of the apatite fission tracks (AFT) during the Oligocene and it is difficult to separate the effects of deep erosion from that of uplift, also considering that they can be closely related. In any case, a progressive incision of the thicker part of the dome is documented soon after the CFB deposition in the Blue Nile Gorge and during the Miocene and the Plio-Pleistocene in many other parts of the country.

Tuscany Hills and Valleys: Uplift, Exhumation, Valley Downcutting and Relict Landforms

The Tuscany physical landscape is the result of processes of selective erosion initiated by regional uplift. The overall geomorphological setting is characterized by “highlands” or mountain ridges alternated with “lowlands” or basins filled with Mio-Pliocene continental and marine sediments. A planation surface was shaped over bedrock, including Pliocene marine terrains, and is widely preserved on top of the mountain ridges. As a result of uplift, the sedimentary infillings of the Pliocene synform basins were affected by river incision. Gully and badland erosion dominate the clayey terrains while cuestas, mesas and stepped slopes are found in sandstones and conglomerate terrains. Large karstic depressions are also found. In the past, these hosted palaeo-springs that alimented travertine and calcareous tufa deposition which spread out to occupy large valley sectors.