Article

# Increased sedimentation following the Neolithic Revolution in the Southern Levant

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## Abstract

The Dead Sea drainage basin offers a rare combination of well-documented substantial climate change, intense tectonics and abundant archaeological evidence for past human activity in the Southern Levant. It serves as a natural laboratory for understanding how sedimentation rates in a deep basin are related to climate change, tectonics, and anthropogenic impacts on the landscape. Here we show how basin-wide erosion rates are recorded by thicknesses of rhythmic detritus laminae and clastic sediment accumulation rates in a long core retrieved by the Dead Sea Deep Drilling Project in the Dead Sea depocenter. During the last ~ 11.5 kyear the average detrital accumulation rate is ~ 3–4 times that during the last two glacial cycles (MIS 7c-2), and the average thickness of detritus laminae in the last ~ 11.6 kyear is ~ 4.5 times that between ~ 21.7 and 11.6 ka, implying an increased erosion rate on the surrounding slopes during the Holocene. We estimate that this intensified erosion is incompatible with tectonic and climatic regimes during the corresponding time interval and further propose a close association with the Neolithic Revolution in the Levant (beginning at ~ 11.5 ka). We thus suggest that human impact on the landscape was the primary driver causing the intensified erosion and that the Dead Sea sedimentary record serves as a reliable recorder of this impact since the Neolithic Revolution.

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... On both sides of the Dead Sea (Syrian African) Rift (Jordan and Dead Sea Valley)-in the Land of Israel (modern Israel/Cisjordan) and Transjordan (modern Kingdom of Jordan) (southern Levant) ( Fig. 1)-Neolithic society and the agricultural revolution impacted the rock surfaces, slopes, sediments, and soils of the landscape adjacent to settlements (Grosman and Goren-Inbar, 2007;Yaroshevich et al. 2018;Goren-Inbar et al. 2022). However, the environmental impact of the Neolithic era is still under debate and may have been over-emphasised in some cases (see Lu et al. 2017Lu et al. , 2020. As a rule, palaeoenvironmental studies of the Early Holocene rely on single archaeological sites, specific proxies, or a compilation of regional data (Palmisano et al. 2019). ...
... The Dead Sea sediments also point to high fine-grained sediment availability and possible erosion in the Early Holocene; there was a significant increase in fine-grained deposition in the northern Dead Sea basin at this time (Lu et al. 2017). During this period, the source of the fine detritus was probably remobilised Judean soils/sediment and basaltic soils from northern Israel. ...
... In turn, the vegetation cover likely reduced surface rainfall wash and fine-grain erosion rates and we hypothesise that it constrained the intensity of the Soreq flows and water infiltration into the aquifer. However, the large annual dust loads were somewhat prone to fluvial erosion by the copious winter rain and possible summer rain (Bar-Matthews et al. 2019) as recorded in the Dead Sea sediments (Lu et al. 2017). ...
Article
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One of the largest prehistoric settlements in Israel and Jordan was uncovered by the Motza salvage excavation in the largest and deepest drainage basin of the Judean highlands in central Israel. On a fan-shaped piedmont-like slope probably developed from Neolithic waste and materials and covering more than 0.5 km, the Motza “megasite” comprises more than 1,200 excavation squares, each measuring 25 sq.m. Plastered structures, a rich artefactual assemblage and a distinct unit of angular clasts containing artefacts dating mainly to the final stage of the Pre-Pottery Neolithic B (PPNB) period suggest a significant engagement with surrounding resources. A geospatial analysis of the Motza region is presented with preliminary artefactual, geoarchaeological and analytical results from the excavation and a review of regional palaeoclimate, palaeoenvironment and geoscientific studies. The present and past geomorphic processes, and the hydrology of the site’s environs are assessed and their influence on-site selection and sustainability are discussed. The Early Holocene palaeoclimatic and palaeoenvironmental conditions during a geomorphic time-window help to explain the Neolithic climax that apparently generated a reasonable ecogeomorphic impact, probably for the first time in the region. However, this review cannot offer deterministic explanations, especially regarding the abandonment of the megasite. The limitations of palaeo-reconstruction and the impact of recycled landscapes and intensive early modern-to-modern land use are discussed, along with the contribution of the occupiers of the megasite to shaping the regional Mediterranean landscape to the present day.
... We measure thicknesses of aragonite and detritus laminae as couplets on high-resolution digital images using the Corelyzer software with an accuracy of 0.1 mm (estimated to 0.05 mm) (Lu et al., 2017b). The high-resolution images and color contrast of the aragonite and detritus make the laminae easy to recognize, and therefore the counting and measuring were relatively straightforward (e.g., Fig. 2DeF). ...
... One may argue that a lake-level threshold situated at ca. À400 m prevailed (Hall, 1996) since the basin slope angle is relatively moderate around this elevation, and thus can accumulate much more lacustrine sediments during high-stands. However, no apparent increase in the thickness of detritus laminae and the total clastic sediment accumulation rate (SAR) (Lu et al., 2017b) is noted during the time intervals in which the lake-level fluctuated below À400 m (during~14.0e11.6 ka; Fig. 6AeC). Moreover, large areas of loose Lisan outcrops (e.g., Massada and Perazim Valley) on the western Dead Sea lake's margins above À400 m have been exposed during the last deglaciation and may have also supplied a large amount of erodible materials. ...
... The Dead Sea drainage basin experiences relatively high year-toyear precipitation variations due to the influence of two nearby major climatological provinces (Dayan and Morin, 2006; Morin (Torfstein et al., 2013;Hall, 1996). B: Clastic (detritus laminae plus detritus layers) sediment accumulation rate (SAR) in the Dead Sea depocenter, based on Core 5017-1 (Lu et al., 2017b). C: Comparison of lamina thickness (21-points running average) change with significant lake-level and size changes during 26-8 ka; yellow and blue curves represent aragonite and detritus laminae from Core 5017-1, respectively; green curves represent aragonite and detritus laminae from the Dead Sea margin. ...
... This case study provides a unique opportunity to shed new light on the debate by distinguishing and separating trigger and preconditioning factors. First, we focus on one specific setting in which the sediments experienced the same climatic and tectonic forcing (Lu, Bookman, et al., 2020;Lu, Waldmann, Ian Alsop, & Marco, 2017;Lu, Waldmann, Nadel, & Marco, 2017;Lu, Wetzler, et al., 2020). Second, it is established that earthquakes act as the trigger for these events (Lu, Waldmann, Ian Alsop, & Marco, 2017;Lu, Wetzler, et al., 2020;Lu et al., 2021). ...
... In the Dead Sea case, relatively low sedimentation rates are statistically correlated with lake-level rises and high-stands at both the millennial-and orbital-scales (Figures 3b-3d and 4e) (Lu, Bookman, et al., 2020;Lu, Waldmann, Nadel, & Marco, 2017), and thus do not support mechanism "(i)." Regarding the enhanced seismicity hypothesis, a complete paleoearthquake (M w ≥ 5) record that covers the Last Glacial is currently lacking and we are therefore unable to evaluate this model. ...
Article
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Plain Language Summary Some researchers propose that lowering sea‐level leads to mass failures, while, others suggest that raising sea‐level induces mass failures. In contrast, other researchers conclude that no clear correlation exists between mass failures and sea‐level change as the ages of failure events are random. This dispute is due largely to the lack of comprehensive records of mass failures in the geologic record for which ages, triggers, and preconditioning factors can be reliably constrained, thus preventing the testing of cause‐ and ‐effect relationships. We present a record of mass failures from the Dead Sea center over the last 220 kyr. The high‐resolution dating, combined with well‐constrained trigger and preconditioning factors, makes this a unique archive for testing the different hypotheses. Our analysis indicates that mass failures can occur during seismic shaking at any lake‐level state at the centennial‐to decadal‐scale, but are more frequent during lake‐level high‐stands with large‐amplitude fluctuations at orbital‐ and millennial‐scales. Furthermore, we find that sedimentation rate is not a preconditioning factor for mass failures under seismic shaking at both the orbital‐ and millennial‐scales.
... The complete lithostratigarphic framework of the Quaternary sediments deposited in the Northern Dead Sea basin was recently reconstructed from records recovered by the International Continental Drilling Program (ICDP) in the deep depocenter of the lake (Neugebauer et al., 2014;Kiro et al., 2017;Lu et al., 2017). However, relatively little attention has been paid to the effect of lake level changes on facies evolution or on the architecture of the main sequences deposited in the central part of the basin. ...
... This is attributed to a regional climatic shift to cooler and wetter climate, which prompted previous studies (e.g. Lu et al., 2017) to regard the entirety of MIS 5 as representing interglacial conditions in the Dead Sea. ...
Article
Sequence architecture and depositional sequences of the Quaternary lacustrine succession deposited in the northern Dead Sea sub-basin were examined using logging data collected during the 2010-2011 ICDP campaign. Methods borrowed from sequence stratigraphy techniques were used to investigate the characteristics of sediments deposited in the central part of the northern lake. High resolution wire logging data combined with a detailed lithological description of the ICDP 5017-1-A deep borehole were used to examine depositional systems and related processes controlling their formation. Analysis of sedimentary stacking patterns and stratal surfaces within the late Pleistocene-Holocene lacustrine succession revealed 10 depositional sequences. It was possible to identify key stratal boundaries and to discern between three sedimentary stacking patterns interpreted here as representing lowstand systems tracts (LST), transgressive systems tracts (TST) and highstand systems tracts (HST). Examined together, they may be interpreted in terms of relative lake level changes. On the basis of the stratigraphic analysis complemented with new age dating, this article presents a record of the sediment accumulation pattern and a relative lake level curve reconstructed for the last ca 225 ka. Results show that stratigraphic units and depositional and erosional surfaces examined in the deep 5017-1-A borehole can be correlated to the proximal area of the basin. This means that changes in relative lake levels were generally synchronous and uniform across the Dead Sea basin. The creation of accommodation space in the northern Dead Sea was found to generally be in phase with paleoclimatic modulating lake levels, and not due to tectonics.
... g-h: Earthquake-deformed AAD(Lu et al., 2020b). i-n, Seismogenic turbidites(Lu et al., 2021a), and seismogenic slump and chaotic deposits(Lu et al., 2017b). Depth of core intervals: (a), 24715-24755 cm; (b), 32751-32760 cm; (c), 33058-33086 cm; (d), 10578-10588 cm; (e), 11004.5-11009.5 ...
Article
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In lakes and oceans, links between modern sediment density flow processes and deposits preserved in long-term geological records are poorly understood. Consequently, it is unclear whether, and if so how, long-term climate changes affect the magnitude/frequency of sediment density flows. One approach to answering this question is to analyze a comprehensive geological record that comprises deposits that can be reliably linked to modern sediment flow processes. To address this question, we investigated the unique ICDP Core 5017-1 from the Dead Sea (the largest and deepest hypersaline lake on the Earth) depocenter covering MIS 7-1. Based on an understanding of modern sediment density flow processes in the lake, we link homogeneous muds in the core to overflows (surface flood plumes, ρflow<ρwater), and link graded turbidites and debrites to underflows (ρflow>ρwater). Our dataset reveals (1) overflows are more prominent during interglacials, while underflows are more prominent during glacials; (2) orbital-scale climate changes affected the flow magnitude/frequency via changing salinity and density profile of lake brine, lake-level, and source materials.
... The range of carbonate veins ages roughly corresponds to intensive weathering in the southern Levant during interglacial periods [24]. If the similar process and ages are correct, then the youngest limits of the zeolitization process are about 30 Ka. ...
Article
The Hatrurim Basin, Israel, is located on the western border of the Dead Sea Transform. This is one of the localities of a unique pyrometamorphic complex whose genesis remains problematic. This paper deals with zeolite-bearing rock that is known in the Hatrurim Basin only. The strata subjected to zeolitization is called the “olive unit” and consists of anorthite–pyroxene (diopside–esseneite) hornfels. Zeolitization occurred in an alkaline environment provided by the interaction of meteoric water with Portland-cement-like rocks of the Hatrurim Complex. The resulting zeolite-bearing rocks contain 20–30% zeolitic material. The main zeolitic minerals are calcic: thomsonite-Ca ± Sr, phillipsite-Ca, gismondine-Ca, and clinoptilolite-Ca. The remainder is calcite, diopsidic pyroxene, garnets (either Ti-andradite and/or hydrogrossular), and less frequently, fluorapatite, opal, and others. Their major mineralogical and chemical compositions resemble carbonated zeolite-blended Portland mortar. Rocks show different values of porosity. Their mechanical characteristics are much better for samples with porosity values below 24%. The related parameters are like those of blended concretes. The minimal age of zeolitization is 5 Ka. The natural zeolite-bearing rocks are resistant to weathering in the Levant desert climate.
... The ∼150 km long and ∼15 km wide Dead Sea Basin formed along this fault, and during the Quaternary this pull-apart basin received ∼4 km of lacustrine sediments in its depocenter (Figure 1a) (Ben-Avraham et al., 2008). The sedimentary sequence comprises alternating laminae of aragonite and detritus (aad; Text S1) (Figure 1o), homogeneous mud (Figures 1n and 1o), gypsum (Figure 1b), halite ( Figure 1c) (Neugebauer et al., 2014;Lu et al., 2017aLu et al., , 2020a, and seismically disturbed units (Figures 1d-1m) (Lu et al., 2017b(Lu et al., , 2020b. The first four types of sediment are regarded as background sedimentation (Text S2), while disturbed units including soft-sediment deformation, liquefied sand layers, slumps, chaotic deposits, and micro-faults have been interpreted as seismites (Heifetz et al., 2005 Widespread in situ soft-sediment deformation characterizes the Dead Sea sediments (Marco & Agnon, 1995;Lu et al., 2017b;Alsop et al., 2019), which manifests as several forms of (i) linear waves, (ii) asymmetric billows, (iii) coherent vortices, and (iv) intraclast breccias (Figures 1d-1m) (Lu et al., 2020b). ...
Article
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Plain Language Summary Seismogenic turbidites are widely used for geohazard assessment. The use of turbidites as an earthquake indicator requires a clear demonstration that an earthquake, rather than non‐seismic factors, is the most plausible trigger. The seismic origin is normally verified either by correlating the turbidites to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. The correlated historic earthquakes could thus constrain the seismic intensities necessary for triggering turbidites. However, the historic correlation method is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites cannot be verified if only one deep core is drilled in a depocenter. Here, we propose a new approach to constrain the seismic origin for prehistoric turbidites in a deep core from the Dead Sea center. Moreover, we constrain the seismic intensities that triggered prehistoric turbidites by analyzing the degree of in situ deformation underlying each turbidite. In addition, we use our results to propose seven basic earthquake‐related depositional scenarios preserved in depocenters located in tectonically active regions like the Dead Sea. These techniques and findings permit a more confident geohazard assessment in the region and other similar tectonic settings by improving the completeness of a paleoseismic archive.
... As an ultimate repository for mass wasting (24) with an average sedimentation rate of 2 mm year −1 (25), the Dead Sea depocenter provides the most complete record of earthquake shaking along the plate boundary. Alternating laminae of white aragonite and dark detritus that characterize the sedimentary sequence of the ICDP Core 5017-1 serve as sensitive markers for identifying earthquake-induced deformation (24,26). ...
Article
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Large earthquakes (magnitude ≥ 7.0) are rare, especially along slow-slipping plate boundaries. Lack of large earthquakes in the instrumental record enlarges uncertainty of the recurrence time; the recurrence of large earthquakes is generally determined by extrapolation according to a magnitude-frequency relation. We enhance the seismological catalog of the Dead Sea Fault Zone by including a 220,000-year-long continuous large earthquake record based on seismites from the Dead Sea center. We constrain seismic shaking intensities via computational fluid dynamics modeling and invert them for earthquake magnitude. Our analysis shows that the recurrence time of large earthquakes follows a power-law distribution, with a mean of 1400 ± 160 years. This mean recurrence is notable shorter than the previous estimate of 11,000 years for the past 40,000 years. Our unique record confirms a clustered earthquake recurrence pattern and a group-fault temporal clustering model, and reveals an unexpectedly high seismicity rate on a slow-slipping plate boundary.
... While along the Egyptian-Israeli border the disruption of grazing pastoral practice had led to deterioration of natural and human habitats, along the Israeli-Jordanian border (the Jordan Rift Valley) the Jordan River fl oodplain supplied suffi cient rangeland resources, preventing the pasture over-burden. In addition, the Jordan Valley is one of the fi rst locations with documented human settlements and probably the fi rst evidence of livestock farming (Lu et al., 2017;Martínez-Navarro et al., 2012). ...
Chapter
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This chapter of the IPBES Land Degradation and Restoration Assessment evaluates the effectiveness of current response strategies both for avoiding or mitigating land degradation and for restoring previously degraded lands. More specifically: it develops a framework to assess the effectiveness of existing interventions designed to avoid and reduce land degradation processes and to rehabilitate or restore various types of degraded lands (e.g., croplands, rangelands, forest lands, urban lands and wetlands) through the recovery of biodiversity, ecosystem structure and services; assesses how responses to land degradation and restoration vary according to site-specific characteristics, including the type and severity of degradation, underlying direct and indirect drivers, and effects on ecosystem services and quality of life; evaluates the effectiveness of various response options to direct drivers (e.g., better land management techniques, access to training) and indirect drivers (e.g., institutions, governance systems) of land degradation; examines the relative success of different institutional, governance and management response options to avoid, reduce and reverse land degradation across a range of economic, social, environmental, cultural, technical and political scenarios; and assesses different institutional, policy and governance responses to research and technology development.
... The identification of these lacustrine facies in the studied boreholes was established based on a visual core description. Following a comparison between high-resolution lithological descriptions (Neugebauer et al., 2014;Torfstein et al., 2015;Kiro et al., 2017;Lu et al., 2017) this approach clearly shows some limitations and in places, the interpretation of these bed units appears to be discordant, such as in the Amora Fm. in the distal 5017-1-A borehole. Furthermore, the distribution of these lithofacies in the basin appears to be complex and occasionally the laminated detritus facies, such as those recorded in the upper sections of the Samra Fm and the Lisan Fm Middle Member, appears to be regionally discordant when comparing distal (Neugebauer et al., 2014) andproximal (e.g. ...
Article
The sedimentary sequences that accumulated within various lakes that occupied the Dead Sea Basin since the Pliocene, contain a detailed record of the climate and tectonic history of the area. Until recently, most of the information about these paleo-lakes was derived from exposures along the marginal terraces of the current Dead Sea (lake), focusing mainly on the last Glacial Lake Lisan and the Holocene-modern Dead Sea. The International Continental Drilling Program (ICDP) recovered a series of cores in the northern Dead Sea Basin, both in the deep depocenter (300 m water depth) and in shallower waters near the current shore. Here, we present downhole logging measurements that were used to provide continuous records of petrophysical properties at depth and to reconstruct lithological profiles. The study highlights how logging data can overcome gaps in drilled-core recovery and be used to examine subsurface geology on a regional scale. Gamma ray, resistivity and velocity wire logs were examined to infer a log-derived lithofacies. The reconstructed profiles presented in this study constitute a first attempt to link deep central settings of the basin with marginal sedimentary sequences. Three main facies were identified in the boreholes including: (Bartov et al., 2002) Finely laminated sequences of mudstones interbedded with siltstones to sandstones; (Bartov et al., 2003) Medium to thick bedded mudstone to sandstone: and (Bartov et al., 2007) Evaporites (e.g. halite and gypsum with some intervals of detrital sediments). The formations that were previously defined along the marginal terraces of the Dead Sea: the Holocene Ze'elim Formation, the last Glacial Lisan Formation, the last interglacial Samra Formation and the early to mid-Pleistocene Amora Formation are identified in the boreholes. A spatial correlation is established providing the stratigraphic architecture of the sedimentary structure beneath the Dead Sea during the late Quaternary. This paper combines geophysical and lithological data and provides the base for subsequent studies on facies interpretation.
... The Dead Sea marginal area has much lower sediment accumulation rates than the depocenter. For example, during the last glacial period, the mean sediment accumulation rate in the PZ1 outcrop (Fig. 1b) was ~0.7 mm yr -1 , which is about half of the rate preserved in core 5017-1 (~1.4 mm yr -1 ) [Lu et al., 2017]. During the Holocene, the mean sediment accumulation rate in the Ein Gedi core ( Fig. 1d; ~10-0 ka) was ~2.1 mm yr -1 [Migowski et al., 2004], which is three times lower than in core 5017-1 (~7.8 mm yr -1 ) for the same time period. ...
Article
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We have studied the history of earthquakes over the past 70 kyr by analyzing disturbed sedimentary layers around the margins of the Dead Sea. However, we know little about disturbances in the basin depocenter, where water depth is ~300 m, and accessible only by drilling. In this study, we compare disturbances from the Dead Sea depocenter, with the contemporaneous earthquake record (~56-30 ka) that was recovered on the western margin of the lake. This comparison allows us to discern the characteristics of disturbance in the different subaqueous environments and identify the source and sedimentary process of mass transport deposits. Our observations indicate that (i) the long disturbance sequences in the Dead Sea depocenter are composed of in situ deformation, slump, and chaotic deposits; (ii) earthquake-triggered Kelvin-Helmholtz Instability is a plausible mechanism for the in situ deformation in the lake center; (iii) the slump is slope area sourced; (iv) the unit of chaotic deposits is lakeshore sourced; and (v) earthquake-triggered slope instability is a viable mechanism for the slump and chaotic deposits. We further suggest that long sequences of disturbance in seismically active lake depocenters can be used to infer earthquake clusters.
Chapter
The Dead Sea is a hypersaline terminal lake located in a tectonic depression along the Dead Sea Transform. The regional paleogeographic setting began to take shape in the Miocene, and by the late Neogene fluvio-lacustrine sequences confined to the basin announced a new subsidence regime. Marine intrusion flooded the tectonic valley in the Pliocene, leading to the accumulation of a thick sequence of evaporites and initiated the development of the unique Ca-chloride brine of the basin. Rapid tectonic movements during the Pleistocene, or even earlier, disconnected the open sea and the valley became a deep, landlocked depression that hosted a series of lacustrine phases. The lakes deposited fine-laminated sequences during relatively wet phases and precipitated gypsum and halite during arid periods. The uppermost sedimentary fill comprises the Late Pleistocene Lisan Formation and the Holocene Ze’elim Formation. Lake Lisan existed during the last glacial period and in its highest stand extended from the Sea of Galilee to south of the Dead Sea, more than 200 m above the current level. The transition to the Holocene began with a dramatic dry-up recorded as a series of retreat strands on the margins of the basin and deposition of a thick halite unit. The Holocene Dead Sea was restricted to the deepest depression and its level fluctuated around 400 m below sea level in pace with climatic fluctuations dictated mostly by precipitation over the northern headwaters. The lake-water balance is a proxy for regional freshwater availability that influenced cultural transformations and demographic patterns during historical periods. The modern Dead Sea is being altered by intensified human activities. Water diversion and damming of freshwater for domestic and agricultural use, and brine evaporation for the potash industry have resulted in a level drop of over 1 m yr⁻¹. The negative water balance has led to erosion of the exposed margins and development of sinkholes due to subsurface evaporite dissolution. The stable stratification of the lake-water column has diminished, and seasonal halite deposition characterizes the modern lake. The level drop has also resulted in drying and migration of spring seepages, putting unique ecosystems under threat. Currently, diversion of sea water from the Red Sea to the Dead Sea is viewed as a comprehensive solution for stabilizing the level as well as for producing hydroelectric power and desalinated water. However, this ambitious initiative must hurdle diplomatic tensions and financing difficulties, as well as intensive environmentalists’ objections.
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This paper explores long-term trends in human population and vegetation change in the Levant from the early to the late Holocene in order to assess when and how human impact has shaped the region’s landscapes over the millennia. To do so, we employed multiple proxies and compared archaeological, pollen and palaeoclimate data within a multi-scalar approach in order to assess how Holocene landscape dynamics change at different geographical scales. We based our analysis on 14 fossil pollen sequences and applied a hierarchical agglomerative clustering and community classification in order to define groups of vegetation types (e.g. grassland, wetland, woodland, etc.). Human impact on the landscape has been assessed by the analysis of pollen indicator groups. Archaeological settlement data and Summed Probability Distribution (SPD) of radiocarbon dates have been used to reconstruct long-term demographic trends. In this study, for the first time, the evolution of the human population is estimated statistically and compared with environmental proxies for assessing the interplay of biotic and abiotic factors in shaping the Holocene landscapes in the Levant.
Chapter
History of the climate has made significant contributions to the understanding of the past climate and could contribute much more than it has to present-day discussions about global climate change knowledge, impacts, and responses (Carey 2012). Climate is basically the history of weather over periods of years, decades, centuries, and more (Edwards 2010). Scholars have used several innovative climate reconstructions and methods to reconstruct the history of climate change (Carey 2012). Their research methods used different sources from radioactive dating, painting, diaries, newspapers, government documents, correspondence, mission reports and daily weather observations, etc. to reconstruct the past climatic conditions (Carey 2012).
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No abstract available. doi:10.2204/iodp.sd.11.04.2011
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The A.D. 2011 Tohoku-Oki Mw 9 earthquake ruptured the megathrust up to the Japan Trench with a large displacement and caused a catastrophic tsunami. This study is the first to use short-lived radioisotopes, including those emitted by the damaged nuclear reactors at the Fukushima Daiichi nuclear power plant (Japan), to document the remobilization of the upper few centimeters of sediment as a highly significant process triggered by the earthquake and its aftershocks. Targeting the post-earthquake environment allowed characterization of the sedimentary signature of this event for a better understanding of paleoearthquakes in Japan and other tectonically active boundary areas. The results stem from 23 piston cores recovered by the 2013 expedition NT13-19 of the Japan Agency for Marine-Earth Science and Technology. We document submarine homogeneous muddy flow deposits that were triggered by ground motion in 2011. They are highly enriched with excess (xs) xs210Pb, requiring only centimeters-deep sediment remobilization over large areas of the seafloor. Some contain 134Cs and 137Cs radioisotopes derived from the Fukushima nuclear reactors, indicating that sedimentation persisted for at least 30 days after the main shock. We found these deposits at all sampling sites in an ~5000 km2 area of the seafloor in 4000-6000 m of water depth. The study area extends for ~260 km parallel to the strike of the trench. The thickness of this "Tohoku layer" (3-200 cm) increases toward the zone of maximum megathrust slip, where deposits are thickest. These results demonstrate that the shaking of the seafloor above large megathrust ruptures near the trench remobilized surficial unconsolidated sediment for hundreds of kilometers. The characteristics of these deposits may typify deposits resulting from large fault slips like that of the Tohoku-Oki earthquake, but also other earthquake deposits, contributing to their identification in the sedimentary record globally.
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Lacustrine laminated sediments are often varves representing annual rhythmic deposition. The Dead Sea high-stand laminated sections consist of mm-scale alternating detrital and authigenic aragonite laminae. Previous studies assumed these laminae were varves deposited seasonally. However, this assumption has never been robustly validated. Here we report an examination of the seasonal deposition of detrital-aragonite couplets from two well-known Late Holocene laminated sections at the Ze'elim fan-delta using palynology and grain-size distribution analyses. These analyses are complemented by the study of contemporary flash-flood samples and multivariate statistical analysis. Because transport affects the pollen preservation state, well–preserved (mostly) air-borne transported pollen was analysed separately from badly-preserved pollen and fungal spores, which are more indicative of water transport and reworking from soils. Our results indicate that (i) both detrital and aragonite laminae were deposited during the rainy season; (ii) aragonite laminae have significantly lower reworked and fungal spore concentrations than detrital and flash-flood samples; and (iii) detrital laminae are composed of recycling of local and distal sources, with coarser particles that were initially deposited in the Dead Sea watershed and later transported via run-off to the lake. This is in line with previous carbon balance studies that showed that aragonite precipitation occurs after the massive input of TCO2 associated with run-off episodes. Consequently, at least for the Holocene Ze'elim Formation, laminated sediments cannot be considered as varves. Older Quaternary laminated sequences should be re-evaluated.
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Earthquakes impart an impressive force on epicentral landscapes, with immediate catastrophic hillslope response. However, their legacy on geomorphic process rates remains poorly constrained. We have determined the evolution of landslide rates in the epicentral areas of four intermediate to large earthquakes (Mw, 6.6–7.6). In each area, landsliding correlates with the cumulative precipitation during a given interval. Normalizing for this meteorological forcing, landslide rates have been found to peak after an earthquake and decay to background values in 1–4 yr, with the decay time scale probably proportional to the earthquake magnitude. The transient pulse of landsliding is not related to external forcing such as rainfall or aftershocks, and we tentatively attribute it to the reduction and subsequent recovery of ground strength. Observed geomorphic trends are not linked with groundwater level changes or root system damage, both of which could affect substrate strength. We propose that they are caused by reversible damage of rock mass and/or loosening of regolith. Qualitative accounts of ground cracking due to strong ground motion abound, and our observations are circumstantial evidence of its potential importance in setting landscape sensitivity to meteorological forcing after large earthquakes.
Conference Paper
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Reconstructing past climatic and environmental conditions is a key task for understanding the history of modern mankind. The interaction between environmental change and migration processes of the modern Homo sapiens from its source area in Africa into Europe is still poorly understood. The principal corridor of the first human dispersal into Europe and also later migration dynamics crossed the Middle East. Therefore, the southern Levant is a key area to investigate the paleoenvironment during times of human migration. In this sense, the Last Glacial (MIS 4-2) is particularly interesting to investigate for two reasons. Firstly, secondary expansions of the modern Homo sapiens are expected to occur during this period. Secondly, there are ongoing discussions on the environmental conditions causing the prominent lake level high stand of Lake Lisan, the precursor of the Dead Sea. This high stand even culminated in the merging of Lake Lisan and Lake Kinneret (Sea of Galilee). To provide an independent proxy for paleoenvironmental reconstructions in the southern Levant during the Last Glacial, we investigated pollen assemblages of the Dead Sea/Lake Lisan and Lake Kinneret. Located at the Dead Sea Transform, the freshwater Lake Kinneret is nowadays connected via the Jordan with the hypersaline Dead Sea, which occupies Earth's lowest elevation on land. The southern Levant is a transition area of three different vegetation types. Therefore, also small changes in the climate conditions effect the vegetation and can be registered in the pollen assemblage. In contrast to the Holocene, our preliminary results suggest another vegetation pattern during the Last Glacial. The vegetation belt of the fragile Mediterranean biome did no longer exist in the vicinity of Lake Kinneret. Moreover, the vegetation was rather similar in the whole study area. A steppe vegetation with dwarf shrubs, herbs, and grasses predominated. Thermophilous elements like oaks occurred in limited amounts. The limiting factor for tree growth was precipitation. Consequently, the precipitation gradient was not as strong as today, and semiarid conditions prevailed in the southern Levant during the Last Glacial. Our study will contribute to the overall aim to reconstruct the way of modern humans to Europe and to understand the complex connection between climate and vegetation change in the Eastern Mediterranean.
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Despite extensive research on the transition from semimobile hunters and gatherers to sedentary, food-producing villagers in Southwest Asia, associated changes in community organization remain unexplored. Undoubtedly new social and economic mechanisms were necessary to facilitate the success of these larger permanent settlements. The emergence of novel intrasite organizational patterns can be elucidated in the archaeological record through analysis of the built environment. This paper presents an interpretation of temporal transformations in community organization utilizing the results from the detailed analysis of Beidha, one of the most extensively excavated early Neolithic villages in Southwest Asia. It is proposed that the emergence of Neolithic farming villages in Southwest Asia was characterized by two parallel and interrelated organizational trends: a more restricted social network for sharing production and consumption activities, and the development of more formal and institutionalized mechanisms for integrating the community as a whole.
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Netiv Hagdud is an Early Neolithic village site in the Lower Jordan Valley. Systematic excavations exposed a 500-sqm surface, which included several oval and circular houses. Carbonized plant remains, animal bones, and a wealth of lithic assemblages were the primary materials recovered from the houses and the fill. The seeds indicate that barley cultivation was practiced, along with the continuous gathering of wild fruits and seeds. Gazelle hunting and trapping of migratory waterfowl provided the major meat sources. Evidence concerning distribution of subsistence activities indicates that the site was occupied during at least nine months each year. Domestic activities are expressed in a variety of grinding and pounding tools, a few bone objects, and numerous flint tools. The lithic industry, classified as Sultanian, is characterized by the presence of Khiam points, sickle blades, and tranchet (Tahunian) axes, and is similar to that uncovered in Jericho. Flexed burials, the removal of adult skulls, and a few female figurines are the only sources of information concering on-site symbolic activities. The report discusses the primary finds from the excavations and places the site within the context of other Early Neolithic sites in the southern Levant.
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The aim of this short note is to provide a summary over on-fault palaeoseismic works on the behavior of the Dead Sea fault (DSF). Key achievements of these studies include: the determination of slip rate of the DSF across different space and time resolutions, which converges at around 4–5 mm/a, confirmation of the sinistral relative motion between the Arabia Plate and the Sinai Subplate and of thrust motion and normal faulting associated with restraining bends and pull apart grabens respectively, and the verification of historical accounts on several strong earthquakes that were associated with surface ruptures. The comparison between the state-of-the-art slip-rate determinations along the DSF and the total motion accommodated by the known historical and instrumental earthquakes shows that current seismicity rates cannot account for the full slip rate. As previously proposed, the short-term rate of seismicity is not necessarily representative of the long-term seismic activity along the DSF. Assuming the historical records of the last two millennia are complete for strong earthquakes, we note long periods of quiescence in the sections of the northern Yammouneh, the Jordan Valley, and the southern Araba.
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Observations of intraclast breccia layers in the Dead Sea basin, formerly termed "mixed layers," provide an exceptionally long and detailed record of past earthquakes and defi ne a frontier of paleoseismic research. Multiple studies of these seismites have advanced our understanding of the earthquake history of the Dead Sea and of the processes that form the intraclast breccias. In this paper, we describe a systematic study of intraclast breccia layers in laminated sequences. The relationship of intraclast breccia layers to intraformational fault scarps has motivated the investigation of these seismites. Geophysical evidence shows that the faults extend into the subsurface, supporting their potential association with strong earthquakes. We defi ne fi eld criteria for the recognition of intraclast breccias, focusing on features diagnostic of a seismic origin. The fi eld criteria stem from our understanding of the mechanisms of breccia formation, which include ground acceleration, shearing, liquefaction, water escape, fl uidization, and resuspension of the originally laminated mud. Comparison between a dated record of breccia layer and the record of historical earthquakes provides an independent test for a seismic origin. The historical dating is signifi cantly more precise and accurate than the radiocarbon dating of breccia layers. Yet, assuming that the lamination of the sediments shows an annual cycle, the precision of counting laminae may approach the precision of the historical record. A similar accuracy is then expected for the intervals between earthquakes. We review our work based on counting laminae representing the historical period, mutually corroborating the seismic origin and the annual lamination. The correlation of documented historical earthquakes with individual breccia layers provides quantitative estimates for the threshold of ground motion for breccia formation in terms of earthquake magnitude and epicentral distance. The investigation of breccia layers and the associated historical earthquakes has underscored cases in which a breccia layer represents a pair of earthquakes. We consider the resolution of individual events in records of breccia layers. A thick breccia layer can account for multiple events, biasing the paleoseismic record. The resolution of an interseismic time interval is no better than the ratio between the thickness of a breccia layer and the rate of sedimentation. We use revised age data for the Lisan Formation and reassess temporal clustering of earthquakes during the late Pleistocene. The variation of recurrence interval corroborates signifi cant clustering. During periods of clustered earthquakes, of order of 1000-5000 yr, the interseismic interval becomes short, and the resolution diminishes, so the peak rate of recurrence may be underestimated. Recurrence intervals inferred from the Dead Sea record of Holocene breccia layers do not feature the extreme variation encountered in the late Pleistocene record. Yet the Holocene record shows marked transitions between periods, each with relatively uniform recurrence interval. Two of the transitions are contemporaneous with transitions in the recurrence intervals of the Anatolian faults, implying broad-scale elastic coupling.
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The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay between river incision and rock uplift is important for understanding tectonic deformation in this region. We report here the discovery of a deeply incised canyon of the Yarlung Tsangpo River, at the eastern end of the Himalaya, which is now buried under more than 500 meters of sediments. By reconstructing the former valley bottom and dating sediments at the base of the valley fill, we show that steepening of the Tsangpo Gorge started at about 2 million to 2.5 million years ago as a consequence of an increase in rock uplift rates. The high erosion rates within the gorge are therefore a direct consequence of rapid rock uplift. Copyright © 2014, American Association for the Advancement of Science.
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The issue of PPNC–PN lithic continuity and change has been raised in the literature, but there are only a few sites where a stratified sequence of the relevant periods can be studied. One such case is Tel Roim West (Hula Valley). The flint assemblages from three relevant successive layers at the site were studied, and details are provided. An emphasis is placed on the sickle blades, as their types have been incorporated in the definitions of Neolithic entities. The TRW results indicate very high resemblance between the assemblages, reflecting no apparent change through the shift from late Pre-Pottery Neolithic to Pottery Neolithic layers.
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A detailed pollen record for the time interval of ∼2500–500 BCE, which covers the time period of the Intermediate Bronze Age (Early Bronze Age IV) into the Iron Ages in the Levant, is presented. The study was conducted in the Ze’elim Gully, which drains the southern Judean Highlands into the Dead Sea. During the Bronze and Iron Ages, the Judean Highlands exhibited dramatic settlement fluctuations. To better understand these oscillations, high-resolution fossil pollen data were combined with a recent pollen data set, lithological features, radiocarbon dating and palaeohydrological information derived from the Dead Sea levels. Due to the occurrence of hiatuses in this fluvial environment, we used a composite profile which was based on two palynological-sedimentological profiles. This integrated information enabled us to reconstruct in great detail for the first time the environmental conditions in relation to the picture derived from archaeological field-work in the Judean Highlands. Evidence for drier climate conditions at the end of the Late Bronze Age may account for the dramatic changes in the settlement pattern which include the destruction of a large number of urban centres and shrinkage of other major sites, not only in the Judean Highlands but in the entire southern Levant. This arid phase may have been one of the reasons for the collapse of eastern Mediterranean civilizations in the mid-thirteenth and twelfth centuries BCE. The improved conditions in the Judean highlands during the Iron Age I (evident by the increasing percentages of both Mediterranean elements and agricultural taxa, e.g. olive and cereals) enabled the recovery of settlement activity, which is the backdrop for the rise of ancient Israel.
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The emerging picture of plant and animal domestication and agricultural origins in the Near East is dramatically different from that drawn 16 years ago in a landmark article by Bar-Yosef and Meadow. While in 1995 there appeared to have been at least a 1,500-year gap between plant and animal domestication, it now seems that both occurred at roughly the same time, with initial management of morphologically wild future plant and animal domesticates reaching back to at least 11,500 cal BP, if not earlier. A focus on the southern Levant as the core area for crop domestication and diffusion has been replaced by a more pluralistic view that sees domestication of various crops and livestock occurring, sometimes multiple times in the same species, across the entire region. Morphological change can no longer be held to be a leading-edge indicator of domestication. Instead, it appears that a long period of increasingly intensive human management preceded the manifestation of archaeologically detectable morphological change in managed crops and livestock. Agriculture in the Near East arose in the context of broad-based systematic human efforts at modifying local environments and biotic communities to encourage plant and animal resources of economic interest. This process took place across the entire Fertile Crescent during a period of dramatic post-Pleistocene climate and environmental change with considerable regional variation in the scope and intensity of these activities as well as in the range of resources being manipulated.
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The influence of forest clearing on landsliding is central to long-standing concern over the effects of timber harvesting on slope stability. Here we document a strong topographic control on shallow landsliding by combining unique ground-based landslide surveys in an intensively monitored study area with digital terrain modeling using high-resolution laser altimetry and a coarser resolution regional study of 3224 landslides. As predicted by our digital terrain based model, landslides occur disproportionately in steep, convergent topography. In terrain predicted to be at low risk of slope failure, a random model performs equally well to our mechanism-based model. Our monitoring shows that storms with 24 hr rainfall recurrence intervals of less than 4 yr triggered landslides in the decade after forest clearing and that conventional monitoring programs can substantially underestimate the effects of forest clearing. Our regional analysis further substantiates that forest clearing dramatically accelerates shallow landsliding in steep terrain typical of the Pacific Northwest.
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Analyses of mean daily discharges and annual peak discharges for streams in 14 of the United States and spanning a wide range of climates show that frequency of occurrence relationships for the large-discharge tails of both follow power laws. The number N(Q) of days on which the discharge exceeds Q, or the number of years in which the peak discharge exceeds Q, is related to Q by N(Q) $\propto$ Q-alpha. Values of the exponent alpha (1 < alpha < 6) decrease in magnitude with increasing aridity so that the ratio of the frequency of occurrence of very large discharges to that of smaller discharges is higher in arid than in humid environments of the United States. To examine the effect of climate change on bed load transport and river incision, we obtain a curve-fit relating mean annual discharge per unit area of drainage basin (an effective precipitation rate $\overline{P) to alpha: alpha - 1$\propto\overline{Pn, where n ~ 1.6. Using this relationship, we confirm that rivers in arid regions should incise less rapidly as climate becomes yet more arid. (If no water flows, the river'' transports no sediment.) Whether aridification of an initially humid environment leads to increased or decreased incision rates, however, depends on the minimum (threshold) discharge capable not only of transporting bed load but also sufficient to scour alluvium from the riverbed and then erode the bedrock. The curve fit relating \$\overline{P to alpha implies that for aridification to accelerate incision, floods that recur only once or twice per millennium (or less frequently) must carry out most of the incision. An overestimate of n could permit smaller, more frequent floods to incise, but it appears that in only special circumstances will aridification accelerate steam incision.
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We argue that by fracturing rock, not by raising it relative to base level, tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes. Tectonic deformation riddles the upper crust with fractures, which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes. Bends in active faults require straining of adjacent rock masses. Aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust. At least some aftershocks must nucleate or lengthen cracks, which contribute to the comminution of these rock masses. Scaling rules suggest that dimensions of ruptures for very small (M < -2) earthquakes can be meters or less. The Gutenberg-Richter recurrence relationship implies that such earthquakes are common, as high-magnification seismographs in low-noise environments confirm. Moreover, large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another; some faults must intersect. Thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller. Dismembered rock arrives at the Earth's surface already prepared to be transported away. As a corollary, both deeply exhumed lower crust and posttectonic igneous rock, never deformed under brittle conditions and not deformed recently, should be less susceptible to detachment and subsequent transport than fractured rock.
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The human population has been increasing exponentially. Simultaneously, as digging sticks and antlers have given way to wooden plows, iron spades, steam shovels, and today's huge excavators, our ability and motivation to modify the landscape by moving earth in con- struction and mining activities have also increased dramatically. As a consequence, we have now become arguably the premier geomorphic agent sculpting the landscape, and the rate at which we are moving earth is increasing exponentially. As hunter-gatherer cultures were re- placed by agrarian societies to feed this expanding population, erosion from agricultural fields also, until recently, increased steadily. This constitutes an unintended additional human impact on the landscape.
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The Dead Sea pull-apart basin is dominated by two tectonic domains, each recording a different subsidence history. The margins are controlled by large N-S-trending zigzags of normal faults and the inner basin by north-south strike-slip faults. This tectonic scenario was accentuated during the tectonically active late Pleistocene. By analyzing the differential subsidence across the basin we illuminate its fine structure. Representing the marginal tectonic domain, the Massada Plain features two fault systems, one at the western edge of the basin and one at the central part of the plain. The integrated subsidence rate for these fault systems amounts to 0.3-0.6 m/ky at the basin margin and 1 m/ ky in the basin center. This rate is in accordance with the long-term calculations from boreholes. The Lisan Peninsula reflects a very different tectonic regime controlled by the eastern segment of the strike-slip fault and the rising salt diapir. The ascent rate of this salt structure during the Holocene was 9 m/ky, as calculated from the 6000-year-old ravinement surface. The volume of this uplift combined with the volume of Mount Sedom accounts for a maximum of 5% of the subsidence in the southern Dead Sea basin, with the remainder attributed to tectonic activity. The subsidence history of the basin is useful not only for the analysis of the basin fill over time but also for correction of datum elevation of the lake level curve. Here we apply this correction to the reference curve for consistency with the global sea level datum and for analysis of the factors controlling lake levels such as bathymetry and climate changes.
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Long-term bedrock incision is driven by daily discharge events of variable magnitude and frequency, with ineffective events below an incision threshold. We explore theoretically how this short-term stochastic behavior controls long-term steady state incision rates and bedrock channel profiles, combining a realistic frequency-magnitude distribution of discharge with a deterministic, detachment-limited incision model in which incision rate is a power function of basal shear stress above a critical shear stress. Our model predicts a power law relationship between steady state slope and drainage area consistent with observations. The exponent of this power law is independent of discharge mean and variability, while the amplitude factor, which controls mountain belt relief, is a power law function of mean runoff (with an exponent of -0.5) and a complex function of runoff variability. In accordance with evidence that incision occurs between 6 and 20&percnt; of time in rapidly incising rivers (>1 mm/yr) our model predicts that channel steepness is virtually insensitive to runoff variability. Runoff variability can only decrease channel steepness for very slow incision rates and/or weak lithologies. The relationship between channel steepness and incision rate is always a power law whose exponent depends on the channel cross-sectional geometry and runoff variability. This contradicts models neglecting discharge stochasticity in which the steepness-incision scaling is set by the incision law exponent. Our results suggest that changes in climate variability cannot explain an increase in bedrock incision rates during the Late Cenozoic within the context of a detachment limited model.
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Tropical mountain areas may undergo rapid land degradation as demographic growth and intensified agriculture cause more people to migrate to fragile ecosystems. To assess the extent of the resulting damage, an erosion rate benchmark against which changes in erosion can be evaluated is required. Benchmarks reflecting natural erosion rates are usually not provided by conventional sediment fluxes, which are often biased due to modern land use change, and also miss large, episodic events within the measuring period. To overcome this, we combined three independent assessment tools in the southern Ecuadorian Andes, an area that is severely affected by soil erosion. First, denudation rates from cosmogenic nuclides in river sediment average over time periods of 1-100 k.y. and establish a natural benchmark of only 150 +/- 100 t km(-2) yr(-1). Second, we find that land use practices have increased modern sediment yields as derived from reservoir sedimentation rates, which average over periods of 10-100 yr to as much as 15 x 10(3) t km(-2)yr(-1). Third, our land cover analysis has shown us that vegetation cover exerts first-order control over present-day erosion rates at the catchment scale. Areas with high vegetation density erode at rates that are characteristically similar to those of the natural benchmark, regardless of whether the type of vegetation is native or anthropogenic. Therefore, our data suggest that even in steep mountain environments sediment fluxes can slow to near their natural benchmark levels with suitable revegetation programs. A set of techniques is now in place to evaluate the effectiveness of erosion mitigation strategies.
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Tell es-Sâfi/gath is situated in the semiarid foothills of central Israel, adjacent to the coastal . plain. An enigmatic landscape feature, noted on aerial photographs, encircles the tell on three sides. This unique feature, unknown from other Near Eastern tells, was investigated. Methods of analysis include aerial photographs, field surveys, excavations, soil analyses, chronotypological ceramic classification, and radiocarbon dating. We concluded that (1) the peculiar landscape feature is a huge human-made trench, over 2 km long, 5–6 m deep, and more than 8 m wide, cut through bedrock; (2) the trench was excavated during the Iron Age IIA (ca. 1000–800 B.C.E.), apparently as part of a siege system; (3) the extracted rock and soil material was dumped on the Iron Age landscape surface on one side of the trench, forming an elevated “berm”; (4) erosion processes transformed this landscape scar, as the trench filled with sediment; (5) stratigraphic analysis indicates two major phases of filling, separated by a period of landscape stability and soil formation (A horizon); (6) the two filling phases, exhibiting Iron Age IIA and Byzantine pottery (ca. 324—638 C.E.), appear to coincide with more intense human activity; and (7) the possible effect of climatic variations seems less obvious. © 2005 Wiley Periodicals, Inc.
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The extent to which Aboriginal Australians used fire to modify their environment has been debated for decades and is generally based on charcoal and pollen records rather than landscape responses to land-use change. Here we investigate the sensitivity of in-situ-produced 10Be, an isotope commonly used in geomorphological contexts, to anthropogenic perturbations in the southeastern Australian Tablelands. Comparing 10Be-derived erosion rates from fluvial sediment (8.7 ± 0.9 mm k.y.-1; 1 standard error, SE; n = 11) and rock outcrops (5.3 ± 1.4 mm k.y.-1; 1 SE; n = 6) confirms that landscape lowering rates integrating over 104-105 yr are consistent with rates previously derived from studies integrating over 104 to >107 yr. We then model an expected 10Be inventory in fluvial sediment if background erosion rates were perturbed by a low-intensity, high-frequency Aboriginal burning regime. When we run the model using the average erosion rate derived from 10Be in fluvial sediment (8.7 mm k.y.-1), measured and modeled 10Be concentrations overlap between ca. 3 ka and 1 ka. Our modeling is consistent with intensified Aboriginal use of fire in the late Holocene, a time when Aboriginal population growth is widely recognized.
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This article discusses two major revolutions in the history of humankind, namely, the Neolithic and the Middle to Upper Palaeolithic revolutions. The course of the first one is used as a general analogy to study the second, and the older one. This approach puts aside the issue of biological differences among the human fossils, and concentrates solely on the cultural and technological innovations. It also demonstrates the issues that are common-place to the study of the transition from foraging to cultivation and animal husbandry can be employed as an overarching model for the study of the transition from the Middle to the Upper Palaeolithic. The advantage of this approach is that it focuses on the core areas where each of these revolutions began, the ensuing dispersals and their geographic contexts.
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Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn – Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (μ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at ~3500–3300 and ~3000–2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns.
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Establishing background (geologic) rates of erosion is prerequisite to quantifying the impact of human activities on Earth's surface. Here, we present 10Be estimates of background erosion rates for ten large (10,000-100,000 km2) river basins in the southeastern United States, an area that was cleared of native forest and used intensively for agriculture. These 10Be-based rates are indicative of the pace at which the North American passive-margin landscape eroded before European settlement (~8 m/m.y.). Comparing these background rates to both rates of post-settlement hillslope erosion and to river sediment yields for the same basins, we find that following peak disturbance (late 1800s and early 1900s), rates of hillslope erosion (~950 m/m.y.) exceeded 10Be-determined background rates more than one-hundred fold. Although large-basin sediment yields during peak disturbance increased 5-10× above pre-settlement norms, rivers at the time were transporting only ~6% of the eroded material; work by others suggests that the bulk of historically eroded material remained and still remains as legacy sediment stored at the base of hillslopes and along valley bottoms. Because background erosion rates, such as we present here, reflect the rate at which soil is generated over millennial time scales, they can inform and enhance landscape-management strategies.
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As efforts to recognize the Anthropocene as a new epoch of geological time are mounting, the controversial debate about the time of its beginning continues. Here, we suggest the term Palaeoanthropocene for the period between the first, barely recognizable, anthropogenic environmental changes and the industrial revolution when anthropogenically induced changes of climate, land use and biodiversity began to increase very rapidly. The concept of the Palaeoanthropocene recognizes that humans are an integral part of the Earth system rather than merely an external forcing factor. The delineation of the beginning of the Palaeoanthropocene will require an increase in the understanding and precision of palaeoclimate indicators, the recognition of archaeological sites as environmental archives, and inter-linking palaeoclimate, palaeoenvironmental changes and human development with changes in the distribution of Quaternary plant and animal species and socio-economic models of population subsistence and demise.
Tectonic uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet's surface, natural and anthropogenic processes serve to modify quite different parts of the Earth landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 meters per million years (m/My), resulting in the accumulation of about 5 giga-tons of sediment per year (Gt/y). Erosion irregularly increased over the ~542 million year span of Phanerozoic time to a Pliocene value of 81 m/My (~19 Gt/y). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of about 74 m/My (~25 Gt/y). Consideration of variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confined to drainage headwaters; ~83% of the global river sediment flux is derived from the highest 10% of the Earth's surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of about 600 m/My (~74 Gt/y), and is largely confined to lower elevations of the Earth's land surface, primarily along passive continental margins; ~83% of cropland erosion occurs over the lower 65% of the Earth's surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (~25 Gt/y) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (74 Gt/y) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately down slope from eroding croplands over the history of human agriculture. Accumulation of post-settlement alluvium on higher order tributary channels and floodplains (mean rate ~12,600 m/My) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of the Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Human beings are therefore the dominant agent of topographic change operating on the surface of the planet today.
Article
Topography acts as a template for numerous landscape processes that include hydrologic, ecologic, and biologic phenomena. These processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes. We have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches. Vegetation is assumed to form a uniform ground cover. Runoff erosion is modeled based on a power function of excess shear stress, in which shear stress efficiency is inversely proportional to vegetation cover. This approach is validated using data. Plant effect on slope stability is represented by additional cohesion provided by plant roots. Vegetation cover is assumed to reduce sediment transport rates due to physical creep processes (rainsplash, dry ravel, and expansion and contraction of sediments) according to a negative exponential relationship. Vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances (runoff erosion and landsliding) and wildfires. Analytical results suggest that in an equilibrium basin with a fixed vegetation cover, plants may cause a transition in the dominant erosion process at the channel head. A runoff erosion–dominated landscape, under none or poor vegetation cover, may become landslide dominated under a denser vegetation cover. The sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena. With model parameter values representative of the Oregon Coast Range (OCR), numerical experiments conducted using the Channel Hillslope Integrated Landscape Development (CHILD) model confirm the findings based on the analytical theory. A highly dissected fluvial landscape emerges when surface is assumed bare. When vegetation cover is modeled, landscape relief increases, resulting in hollow erosion dominated by landsliding. Interestingly, our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure. Simulated landscapes resemble real-world catchments in the OCR when such disturbances are considered.
Article
Le site de Gilgal I, dans la basse vallee du Jourdain a ete occupe au cours de deux courtes periodes attribuees a deux phases anciennes du PPNA datees du debut du 8e millenaire. Plusieurs maisons rondes comportant un abondant materiel (industrie lithique, vaisselle en pierre et figurines) y ont ete fouillees.
Article
Rock uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet's surface, natural and anthropogenic processes serve to modify quite different parts of Earth's landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 m per million years (m/m.y.), resulting in the accumulation of ∼5 gigatons of sediment per year (Gt/yr). Erosion irregularly increased over the ∼542 m.y. span of Phanerozoic time to a Pliocene value of 53 m/m.y. (16 Gt/yr). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of ∼62 m/m.y. (∼21 Gt/ yr). Consideration of the variation in large river sediment loads and the geomorphology of respective river basin catchnients suggests that natural erosion is primarily confined to drainage headwaters; ∼83% of the global river sediment flux is derived from the highest 10% of Earth's surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of ∼600 m/m.y. (∼75 Gt/yr), and is largely confined to the lower elevations of Earth's land surface, primarily along passive continental margins; ∼83% of cropland erosion occurs over the lower 65% of Earth's surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (∼21 Gt/yr) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (75 Gt/ yr) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately downslope from eroding croplands over the history of human agriculture. Accumulation of postsettlement alluvium on higher-order tributary channels and floodplains (mean rate ∼12,600 m/m.y.) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Conversely, available data suggest that since 1961, global cropland area has increased by ∼11%, while the global population has approximately doubled. The net effect of both changes is that per capita cropland area has decreased by ∼44% over this same time interval; ∼1% per year. This is ∼25 times the rate of soil area loss anticipated from human denudation of cropland surfaces. In a context of per capita food production, soil loss through cropland erosion is largely insignificant when compared to the impact of population growth.
Article
Neogene redbeds passing upward into upward-coarsening conglomerate and debris-flow deposits at the foot of the Kunlun Mountains record the change in paleoslope related to uplift of the surface of the northern Tibetan Plateau. Detailed magnetostratigraphy of a 4.5 km section near Yecheng in the western Kunlun Mountains shows that the change from deposition on distal alluvial plains to proximal alluvial fans occurred during the Gilbert reversed chron (4.5 3.5 Ma). The change in depositional facies was accompanied by an increase in sedimentation rate from an average ˜0.15 mm/yr between the earliest Oligocene and the earliest Pliocene to 1.4 mm/yr in the Gauss normal chron (3.6 2.6 Ma). We interpret the change in depositional facies and increase in sedimentation rate as indicating that the main uplift of the northwestern Tibetan Plateau began ca. 4.5 Ma.
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Humans move increasingly large amounts of rock and sediment during various construction activities, and mean rates of cropland soil loss may exceed rates of formation by up to an order of magnitude, but appreciating the actual importance of humans as agents of global erosion necessitates knowledge of prehistoric denudation rates imposed on land surfaces solely by natural processes. Amounts of weathering debris that compose continental and oceanic sedimentary rocks provide one such source of information and indicate that mean denudation over the past half-billion years of Earth history has lowered continental surfaces by a few tens of meters per million years. In comparison, construction and agricultural activities currently result in the transport of enough sediment and rock to lower all ice-free continental surfaces by a few hundred meters per million years. Humans are now an order of magnitude more important at moving sediment than the sum of all other natural processes operating on the surface of the planet. Relationships between temporal trends in land use and global population indicate that humans became the prime agents of erosion sometime during the latter part of the first millennium A.D.
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Current global warming necessitates a detailed understanding of the relationships between climate and global ice volume. Highly resolved and continuous sea-level records are essential for quantifying ice-volume changes. However, an unbiased study of the timing of past ice-volume changes, relative to polar climate change, has so far been impossible because available sea-level records either were dated by using orbital tuning or ice-core timescales, or were discontinuous in time. Here we present an independent dating of a continuous, high-resolution sea-level record in millennial-scale detail throughout the past 150,000 years. We find that the timing of ice-volume fluctuations agrees well with that of variations in Antarctic climate and especially Greenland climate. Amplitudes of ice-volume fluctuations more closely match Antarctic (rather than Greenland) climate changes. Polar climate and ice-volume changes, and their rates of change, are found to covary within centennial response times. Finally, rates of sea-level rise reached at least 1.2 m per century during all major episodes of ice-volume reduction.
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A characteristic hallmark of the Pre-Pottery Neolithic B (PPNB) in the southern Levant was the extensive use of lime plaster for architectural and other purposes. Yet no obvious kilns have been identified in archaeological contexts. Here we present details of an experimental pit-kiln modeling lime-plaster production based on observed burnt stone accumulations in pits at the PPNB site of Kfar HaHoresh in the lower Galilee. The experimental kiln was loaded in layers with ∼500 kg of limestone (pebbles and stones) and ∼1000 kg of fuel (branches and dung). Fired for 24 hours, and reaching a maximum 870°C, the kiln yielded almost 250 kg of quicklime (calcium oxide, CaO). Micromorphological samples, general observations, and scaled plan view drawings made immediately following and nine years after ignition demonstrate that the original shape of the kiln and residual quicklime within and around it rapidly dissipated through bioturbation, trampling by animals, erosion, rain, and exposure to the elements. This could account for the seeming absence of kilns within sites, although they were probably located close to where lime-plaster was applied, given the unstable nature and toxic effects of handling quicklime. Calculations of the manpower and fuel involved indicate that PPNB lime-plaster production may have been less labor intensive and less detrimental to the environment than previously portrayed. © 2008 Wiley Periodicals, Inc.