Shallow subsurface geology and seismic microzonation in a deep continental basin. The Avezzano Town, Fucino basin (central Italy)

We present detailed geological investigations aimed at the reconstruction of the shallow subsurface geology, and associated local seismic hazard, of the Avezzano town in the Quaternary Fucino basin (central Apennines). This work shows a basic (Level 1) seismic microzonation (SM) of the Avezzano town, focusing the attention on geologic constraints. We also discuss some methodological procedures of SM. Level 1 SM involves a reconstruction of the subsurface geological model achieved by a multidisciplinary approach synthesized in two main thematic maps and geologic sections. The first map, containing essential geologic information, is formed by overlapping layers (geological units, litho-technical units, and geomorphological/structural features). The second map is a summary map, easily accessible to non-geologist earthquake scientists/technicians, which synthesizes surface geology, subsurface data and resonance frequencies into homogeneous microzones. The two maps are tools for land and urban planning. The Avezzano area provides a case study of shallow subsurface geology and site effects in a deep continental basin environment, and is of potential interest for similar geologic contexts worldwide. Within the investigated area, almost all the possible earthquake-induced effects can occur, such as (a) stratigraphic amplifications in a wide range of resonance frequencies (from 0.4 to > 10 Hz); (b) liquefaction; (c) coseismic surface faulting; (d) basin-edge effects; and (e) slope instability

Holocene Hydrological Changes Inferred from Alluvial Stream Entrenchment in North Tian Shan (Northwestern China)

We analyze the possible contribution of climate change or tectonics on fluvial incision from the study of a case example along the northern flank of Tian Shan. The rivers that exit the high range fed large alluvial fans by the end of the last glacial period. They have since deeply entrenched the piedmont by as much as 300 m. We have surveyed several terraces that were cut and abandoned during river entrenchment, providing information on intermediate positions of the riverbed during downcutting. They suggest a gradual decline in river slope during a major phase of incision throughout the Holocene. Tectonic uplift affects only a zone about 5 km wide, corresponding to a growing anticline, and is shown to account for about 10% of total incision. Incision was therefore most probably driven by climate change. From observed fluvial incision, we estimate the water discharge in excess of that needed to carry the sediments supplied by hillslope erosion in the headwaters. We used a model based on a transport‐limited erosion law. The model predicts relaxation process with entrenchment in the upper reach, downstream progradation of the incision‐sedimentation line, and a progressive decrease of river slope during incision consistent with our observations. According to this model, river slope might be used as a proxy for specific discharge and then for volumetric discharge, provided that an assumption is made about river width variations. We conclude that river incision in the study area has resulted from dynamic adjustment of the hydrological system to the settlement of wetter conditions in the early Holocene, when water discharge might have been about three times as high as at present. Then, a rather arid climate with enhanced seasonality has likely prevailed from the mid‐Holocene (~6 ka B.P.) until now

Some evolutionary patterns of palaeokarst developed in Pleistocene deposits (Ebro Basin, NE Spain): Improving geohazard awareness in present-day karst

Pleistocene detrital deposits in the central Ebro Basin frequently show deformation features due mainly to karstification in the underlying Neogene evaporites. In 123 cases, estimation of parameters of shape and minimum volume of materials involved was accomplished. Six of them were analysed in more detail to establish the main processes involved in their genesis and the succession of events. All the deformation features in the selected sites are synsedimentary. To achieve the objectives, intense fieldwork was made applying methods of sedimentology and structural geology. Usually, a complex evolutionary pattern was observed, with evidences of dissolution, sagging, collapse, gravity flow, suffosion, and plastic flow. In a schematic way, three main situations, independent of the age of the analysed deposits, can be distinguished: (a) slow subsidence, (b) collapse, and (c) temporal overlapping of both processes. In the first 2 scenarios, basins with smooth or abrupt borders, respectively, were generated on the land surface. In the third one, slow subsidence was followed by a collapse, located in the area of maximum flexure. These patterns are also observed in present-day dolines. Comparison of direct and indirect parameters between paleodolines and present-day dolines indicates a bigger size of the latter, probably caused by the different conditions of observation. This study helps to know the possibilities in the evolution of mantled karst features, to estimate the volume of material affected by karstification and to improve the knowledge of present-day dolines behaviour. Consequently, study of paleodolines must be considered to achieve a better urban planning in active karstic areas

Early human impacts and ecosystem reorganization in southern-central Africa

Modern Homo sapiens engage in substantial ecosystem modification, but it is difficult to detect the origins or early consequences of these behaviors. Archaeological, geochronological, geomorphological, and paleoenvironmental data from northern Malawi document a changing relationship between forager presence, ecosystem organization, and alluvial fan formation in the Late Pleistocene. Dense concentrations of Middle Stone Age artifacts and alluvial fan systems formed after ca. 92 thousand years ago, within a paleoecological context with no analog in the preceding half-million-year record. Archaeological data and principal coordinates analysis indicate that early anthropogenic fire relaxed seasonal constraints on ignitions, influencing vegetation composition and erosion. This operated in tandem with climate-driven changes in precipitation to culminate in an ecological transition to an early, pre-agricultural anthropogenic landscape.info:eu-repo/semantics/publishedVersio

Lake Magadi and the Soda Lake Cycle: A Study of the Modern Sodium Carbonates and of Late Pleistocene and Holocene Lacustrine Core Sediments

The Magadi Basin, Kenya, within the East African Rift Valley, contains two closed-basin alkaline lakes, Lake Magadi and Nasikie Engida that now precipitate trona (Na2CO3.NaHCO3.2H2O) and nahcolite (NaHCO3). Observations of the conditions of modern trona and nahcolite deposition in the Magadi Basin form the basis of the “soda lake cycle”. This study aims to use the sedimentary structures of the modern sodium carbonates of Lake Magadi as an analogue for similar ancient deposits around the world, including the vast trona and nahcolite deposits of the Eocene Green River Formation. Lake Magadi has been evolving since 1.08 Ma within a well-known region of early hominin activity in East Africa. As part of the Hominin Sites and Paleo-lakes Drilling Project (HSPDP) four boreholes were drilled beneath Lake Magadi up to a maximum depth of 197 m. Analysis of three of the extracted sediment cores has provided information on the evolution of Lake Magadi from the Late Pleistocene to present

Saline lake ichnology : composition and distribution of cenozoic traces in the saline, alkaline lakes of the Kenya Rift Valley and Eocene Green River Formation, U.S.A.

A detailed study was made of the composition and distribution of modern and fossil animal and plant traces around saline, alkaline lakes in tectonically active, closed lake-basins. Modern and Pleistocene traces that were examined in lake basins of the Kenya Rift Valley (Lakes Bogoria, Magadi, and Nasikie Engida) were compared directly with fossil traces from the Eocene Lake Gosiute in the Green River Formation of Wyoming, U.S.A., which had a similar hydrochemistry. Analysis of lithofacies and the stratigraphic packaging of the sediments hosting biogenic structures was undertaken so that their vertical and lateral distribution could be used to interpret lake histories and to help to develop depositional models of enigmatic sedimentary successions. A focus was given to the application of the results for paleoecology and stratigraphy, and a model for predicting the position of different trace associations in vertical successions and in different parts of saline, alkaline lake basins has been developed. Evidence from the Kenyan lakes and Eocene Lake Gosiute shows that (1) sedimentary environments are diverse in underfilled basins, and frequent lake-level fluctuations strongly impact the distribution of sedimentary environments suitable for the production and preservation of biogenic structures; (2) the distribution of biogenic structures in underfilled basins is related to the geomorphological and structural setting, tectonic activity, catchment lithology, the basin margin or basin centre location, climate, and salinity and alkalinity, together with other finer-scale environmental and biological controls; (3) because saline environments are restrictive, sites of relatively dilute inflow (springs, rivers and deltas, ephemeral streams) provide oasis-like habitats for animals and plants, and contribute to the increased diversity and laterally variable distribution of saline-lake trace assemblages; and (4) the vertical distribution of trace fossils in a stratigraphic succession reflects changing environments through time; important stratigraphic surfaces, usually formed during periods of lake-level fall, can be recognized from the overprinting patterns of traces produced under different conditions

Quaternary diatomaceous sediments and the geological evolution of lakes, Turkana, Baringo and Bogoria Kenya Rift Valley.

PhdQuaternary lacustrine sediments are described from three contrasting areas within the Kenya Rift Valley. Descriptions are given of the mid-Pleistocene Olorgesailie Formation at Olorgesailie. (southern-, Kenya Rift Valley), a series of lacustrine sediments deposited between the mid-Miocene and present in the Baringo District (central Kenya Rift Valley) and finally of Quaternary'(largely Holocene) deposits at East Turkana (northern Kenya Rift Valley). A wide range of environments are represented by these deposits including offshore and littoral lacustrine, deltaic and alluvial situations. Emphasis is placed on the examination of lacustrine and lake marginal sediments. Diatom assemblages found. in these deposits are described for the first time. These have 'been studied using optical and scanning electron microscopy. The. relationships between diatom assemblages and sedimentary facies are examined and evolutionary trends in certain diatoms are discussed. The contemporary ecology of diatoms at East Turkana is discussed and a review is given of diatom ecology and lake classification in East Africa. Diatoms are used to indicate transgression-regression. cycles during the Holocene, and palaeoecological conditions through the Quaternary. Mapping in conjunction with some altimetric data is used to indicate the location, extent and height of several Holocene lacustrine still-stands. Geochemical and sedimentological data is presented for the Holocene deposits at East Turkana and in the Baringo District. Several erosional and depositional processes operating at East Turkana are briefly discussed. A classification of Holocene environments at East T»rksna is presented. The palaeogeography of the northern Kenya Rift Valley and the development of diatom floras during the Holocene is discussed. Data presented here and in the literature is considered and reviewed from a palaeoclimatic viewpoint. The development of Lakes Turkana, Baringo and Bogoria through the Quaternary are also considered. Conclusions are drawn as to the value of diatoms in palaeoecology and stratigraphy

Rainstorm Debris Floods: A Problem in Public Welfare

This item is part of the Agricultural Experiment Station archive. It was digitized from a physical copy provided by the University Libraries at the University of Arizona. For more information, please email CALS Publications at [email protected]

Structural, tectonic and Quaternary study of the eastern Madeline Plains, California and southwestern Smoke Creek Desert, Nevada

Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.A structural, tectonic and Quaternary study of the eastern Madeline Plains (MP) and southwestern Smoke Creek Desert (SCD) in northeastern California and northwestern Nevada indicates that: 1) the Likely fault zone (LFZ) may be the northeastern limit of the Walker Lane (WL), 2) the WL appears to step right to the LFZ in the eastern Honey Lake Valley (HLV)/southwestern SCD area of California and Nevada, 3) a structural block defined by the Honey Lake Fault (HLF) and the northern extension of the WL on the west, easternmost HLV/southwestern SCD on the south, and the LFZ, Dry Valley-Smoke Creek Ranch fault zone (DV-SCRFZ) and the Bonham Ranch fault zone (BRFZ) on the east may be migrating toward the northwest, and 4) eastern HLV and southwestern SCD may be a young pul 1 - apart basin forming along the trailing edge of the northwest migrating block. Pluvial deposits of <5,000 years have been displaced along the LFZ in eastern MP. Pluvial deposits of <12,000 years have been displaced along the right-oblique-slip DV-SCRFZ and BRFZ in southwestern SCD. Fault scarp profiles along the BRFZ show two tectonic events in the past 12,000 years; the most recent occurred about 290 ± 70 years B.P. This event resulted in about 40 km of surface rupture length and a maximum of 2.9 m of vertical displacement. Surface magnitudes of Ms 7.0 and Ms 7.3 for the 290 ± 70 years B.P. event were estimated using the regression curves, respectively, of Slemmons and others (1989) and Bonilla and others (1984)

Environmental context and adaptations of prehistoric and early historical occupation in the Southern Altai (SW Siberia–East Kazakhstan)

The Altai Mountains are well-known for their unique archaeological records, with rich, chronologically sequenced Palaeolithic, Neolithic and the Bronze Age (late fourth–early first millennium BC) sites and, in particular, the Iron Age Scytho-Siberian and early historical monuments represented by burial sites, ritual structures, and rock-art. The Altai prehistoric archaeological localities are distributed across a broad range of topographic and ecological settings, encompassing altitudinal zones from 800 m asl in the lower reaches of glacial river valleys up to 2500/3000 m asl on the high mountain plateaus. The partial spatial overlap of these (often multi-component) geoarchaeological loci over time suggests that similar adaptive strategies were employed by countless generations of hunter and later nomadic communities—their actions constrained by the locally specific forms of (palaeo-)relief and the associated ecosystems. The dynamics of the initial occupation of the boreal and alpine Altai landscapes and subsequent processes of (re-)colonisation during the Final Pleistocene-Holocene transition are directly linked to transformations in the regional hydrological systems after the LGM. The principal settings for early pastoral settlements were the xerothermic grasslands that formed on the flat glacio-lacustrine terraces which rise above the modern fluvial floodplains—the remains of ice-dammed wastage lake basins drained at the end of the Pleistocene (15,000–13,000 year BP). Marked climatic changes, evidenced by regional variations in temperature and humidity across the territory, are well attested in the geological, biotic and archaeological records. The initial Sub-Boreal aridification correlated with the beginnings of the Altai Bronze Age traditions continued until the early Iron Age—causing an expansion of parkland-steppe in the main valleys and a forest retreat in the foothills. Mountain steppes constituted the most essential food-procurement habitat for the Holocene prehistoric and historical settlements of Southern Altai. The current degradation of insular alpine permafrost poses an imminent threat to preservation of the region’s most precious archaeological monuments—the frozen burial mounds of the Pazyryk culture (sixth–third century BC) belonging to the UNESCO World cultural heritage. © 2018, The Author(s).IRBIS, ngo.; Czech Development Program (Ministry of Environment); Government of the Republic of Gorno Altai; National Geographic Societ