Holocene seismic and tectonic activity in the Dead Sea area

The Dead Sea is a large, active graben within the Dead Sea rift, which is bounded by two major strike-slip faults, the Jericho and the Arava faults. We investigated the young tectonic activity along the Jericho fault by excavating trenches, up to 3.5 m deep, across its trace. The trenches penetrate through Late Pleistocene and Holocene sediments. We found that a zone, up to 15 m wide, of disturbed sediments exists along the fault. These disturbed sediments provide evidence for two periods of intensive activity or more likely, for two major earthquakes, that occurred during the last 2000 years. The earthquakes are evident in small faults, vertical throw of a few layers, cracks, unconformities and wide fissures. We further documented evidence for recent sinistral shear along the Jericho fault in deformed sediments and damage to an 8th Century palace on a subsidiary fault. We suggest that the two earthquakes may be correlated with the 31 B.C. earthquake and the 748 A.D. earthquake, reported by the ancients.     

A late Wisconsin and Holocene vegetation history from the central brooks range: Implications for Alaskan palaeoecology

Five pollen diagrams reveal late Wisconsin and Holocene vegetation changes in the Walker Lake/Alatna Valley region of the central Brooks Range, approximately 100 km west of the area studied by D. A. Livingstone (1955, Ecology36, 587–600). New insights into the vegetation history of this region are provided by calculations of pollen influx and by the use of linear discriminant analysis to separate Picea glauca and P. mariana pollen. Three major pollen zones are identified: (1) a basal herb zone, characterized by high percentages of Cyperaceae, Gramineae, Salix, and Artemisia, and low total pollen influx; (2) a shrub Betula zone with increased total pollen influx and very high percentages of Betula pollen, predominantly in the size range of B. nana and B. glandulosa; and (3) and Alnus zone dominated by Alnus pollen. Lakes currently within the boreal forest or near tree line show relatively high percentages of Picea pollen in the Alnus zone. Several striking vegetation changes occurred between ca. 10,000 and 7000 yr B.P. Between ca. 11,000 and 10,000 yr B.P., Populus balsamifera pollen percentages as great as 30% indicate that this species was present at low-elevation sites near Walker Lake. These populations declined abruptly ca. 10,000 yr ago and have never regained prominence. About 8500 yr B.P., Picea glauca pollen reached 10–15%, indicating the arrival of P. glauca in or near the study area. P. glauca populations evidently decreased ca. 8000 yr ago, when Picea pollen percentages and influx fell to low values. About 7000 yr B.P., Alnus pollen percentages and influx rose sharply as alder shrubs became established widely. Picea once more expanded ca. 5000 yr ago, but these populations were dominated by P. mariana rather than P. glauca, which increased slowly at this time and may still be advancing northward. Some vegetation changes have been remarkably synchronous over wide areas of interior Alaska, and probably reflect responses of in situ vegetation to environmental changes, but others may reflect the lagged responses of species migrating into new areas.     

Holocene rockfalls in the southern Negev Desert,Israel and their relation to Dead Sea fault earthquakes

Rockfall ages in tectonically active regions provide information regarding frequency and magnitude of earthquakes. In the hyper-arid environment of the Dead Sea fault (DSF), southern Israel, rockfalls are most probably triggered by earthquakes. We dated rockfalls along the western margin of the DSF using terrestrial cosmogenic nuclides (TCN). At each rockfall site, samples were collected from simultaneously exposed conjugate boulders and cliff surfaces. Such conjugate samples initially had identical pre-fall (“inherited”) TCN concentrations. After boulder detachment, these surfaces were dosed by different production rates due to differences in post-fall shielding and geometry. However, in our study area, pre-rockfall inheritance and post-rockfall production rates of TCN cannot be evaluated. Therefore, we developed a numerical approach and demonstrated a way to overcome the above-mentioned problems. This approach can be applied in other settings where rockfalls cannot be dated by simple exposure dating. Results suggest rockfall ages between 3.6 ± 0.8 and 4.7 ± 0.7 ka. OSL ages of sediment accumulated behind the boulders range between 0.6 ± 0.1 and 3.4 ± 1.4 ka and support the TCN results. Our ages agree with dated earthquakes determined in paleoseismic studies along the entire length of the DSF and support the observation of intensive earthquake activity around 4–5 ka.     

Holocene climate variability and cultural evolution in the Near East from the Dead Sea sedimentary record

A comprehensive record of lake level changes in the Dead Sea has been reconstructed using multiple, well dated sediment cores recovered from the Dead Sea shore. Interpreting the lake level changes as monitors of precipitation in the Dead Sea drainage area and the regional eastern Mediterranean palaeoclimate, we document the presence of two major wet phases ( 10–8.6 and  5.6–3.5 cal kyr BP) and multiple abrupt arid events during the Holocene. The arid events in the Holocene Dead Sea appear to coincide with major breaks in the Near East cultural evolution (at  8.6, 8.2, 4.2, 3.5 cal kyr BP). Wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions, suggesting a parallelism between climate and Near East cultural development.     

Holocene palaeoecology and shoreline displacement on the Biskopsmåla Peninsula, southeastern Sweden

High-resolution palaeoecological proxies of pollen, macrofossils and diatoms from an isolation lake provide a long-term record of the Holocene landscape history and shoreline displacement on the Biskopsmåla Peninsula in central Blekinge, SE Sweden. During the Preboreal/Boreal transition, the peninsula was sparsely vegetated by woodlands, along with lateglacial dwarf shrub/steppe communities. The lake basin was isolated from the shallow Yoldia Sea during this time. The regional climate improved from 10 700 cal. BP, evident as progressive expansion of Pinus-dominated mixed forest with deciduous trees. The lake basin was probably connected with the Ancylus Lake during the period 10700–10 100 cal. BP. Subsequently the basin became isolated again, corresponding to the Early Littorina Sea phase. Replacement of freshwater diatoms by those with brackish-water affinity at 8100 cal. BP indicates the initial transgression of the Littorina Sea in this basin. But not until 7500 cal. BP were brackish conditions fully established. Peaks of brackish-marine diatoms and dinoflagellates during 7500–7000 cal. BP indicate increased saltwater inflow to the Baltic Sea in response to global meltwater pulse 3. However, interactive changes in seagrass and stonewort macrofossil concentrations suggest that three minor transgressions during 5900–5300, 5000–4700 and 4400–4000 cal. BP occurred locally, associated with centennial-scale variations in regional wind pattern or coastal storminess. By 3000 cal. BP, the lake basin was finally isolated from the Baltic, and thereafter the landscape on the peninsula became gradually more influenced by human activities.     

Palynology and sedimentology of the Miocene series in the north-east of Tunisia: the climatic and eustatic signature

The Saouaf syncline is located in Tunisia Centre north-east, south-east of the Tunisian dorsal. The sedimentary series, starting with limestone and marlstone, is essentially an alternation of three terms, sandstone, clay and lignite. It is in this basin that the Saouaf Formation was defined as a siliciclastic and lignite series dating back to the Serravallian-Tortonian age. The pollen associations identified in this series allowed for the organization of the vegetation in the era in altitudinal levels (coastal environment, rivers edges, plains, high zones). The evolution of vertical micro-floristic associations through the detailed analysis of the palynological diagram reflects the fluctuation of climatic and ecological parameters during this period. Moreover, the facies associations reflect an evolutionary curve in the depositional environment, showing its fluctuation over time. Accordingly, the synthesis of palynological data, correlated with lithosedimentological ones, suggests the type of environment prevailing at that time. This is a coast-lagoon fluvio-deltaic environment with a significant detrital influence in a subsiding context controlled by a fluctuating but generally warm climate.     

Palynology, palaeoecology and palaeodepositional environment of Eocene lignites and associated sediments from Matanomadh mine, Kutch Basin, western India

Extensive Cenozoic lignite-bearing sediments in the western part of Kutch, western India provide a unique opportunity to study the floral diversity at a crucial time of early Eocene Climatic Optimum (EECO). Rock samples representing a lignite-bearing sequence from the open cast mine at Matanomadh, Gujarat, western India were collected to study the palynofloral composition and to interpret the palaeoclimate and environment of deposition. The sequence mainly composed of lignites, shales and calcareous mudstones yielded rich assemblage consists of pteridophytic spores (7 genera, 10 species), angiosperm pollens (20 genera, 26 species), fungal remains (14 genera, 16 species) and dinoflagellate cysts. The palynofloral assemblage is marked with dominance of angiospermic pollen, particularly those having affinity with the family Arecaceae. Occurrence of fungal remains in high abundance is also noticed. Based on palynomorph contents, the studied sequence is divisible into two palynozones. It is inferred that lower part of the sequences was deposited in a near-shore environment with intermittent marine incursions whereas the depositional regime of upper part was shallow marine. The climate is found to be tropical-subtropical, humid with heavy precipitation during the deposition of Matanomadh lignite-bearing sequence.     

Control of wind strength and frequency in the Aral Sea basin during the late Holocene

Changing content of detrital input in laminated sediments traced by XRF scanning and microfacies analyses reflect prominent variations in sedimentation processes in the Aral Sea. A high-resolution record of titanium from a core retrieved in the northwestern Large Aral Sea allows a continuous reconstruction of wind strength and frequency in western Central Asia for the past 1500 yr. During AD 450–700, AD 1210–1265, AD 1350–1750 and AD 1800–1975, detrital inputs (bearing titanium) are high, documenting an enhanced early spring atmospheric circulation associated with an increase in intensity of the Siberian High pressure system over Central Asia. In contrast, lower titanium content during AD 1750–1800 and AD 1980–1985 reflects a diminished influence of the Siberian High during early spring with a reduced atmospheric circulation. A moderate circulation characterizes the time period AD 700–1150. Unprecedented weakened atmospheric circulation over western Central Asia are inferred during ca. AD 1180–1210 and AD 1265–1310 with a considerable decrease in dust storm frequency, sedimentation rates, lamination thickness and detrital inputs (screened at 40-μm resolution). Our results are concurrent with changes in the intensity of the Siberian High during the past 1400 yr as reported in the GISP2 Ice Core from Greenland.     

A high resolution late Holocene palaeo environmental record from the central Adriatic Sea

A multi-proxy study of a Holocene sediment core (RF 93-30) from the western flank of the central Adriatic, in 77 m of water, reveals a sequence of changes in terrestrial vegetation, terrigenous sediment input and benthic fauna, as well as evidence for variations in sea surface temperature spanning most of the last 7000 yr. The chronology of sedimentation is based on several lines of evidence, including AMS ¹⁴C dates of foraminifera extracted from the core, palaeomagnetic secular variation, pollen indicators and dated tephra. The temporal resolution increases towards the surface and, for some of the properties measured, is sub-decadal for the last few centuries.The main changes recorded in vegetation, sedimentation and benthic foraminiferal assemblages appear to be directly related to human activity in the sediment source area, which includes the Po valley and the eastern flanks of the central and northern Appenines. The most striking episodes of deforestation and expanding human impact begin around 3600 BP (Late Bronze Age) and 700 BP (Medieval) and each leads to an acceleration in mass sedimentation and an increase in the proportion of terrigenous material, reflecting the response of surface processes to widespread forest clearance and cultivation. Although human impact appears to be the proximal cause of these changes, climatic effects may also have been important. During these periods, signs of stress are detectable in the benthic foram morphotype assemblages. Between these two periods of increased terrigeneous sedimentation there is smaller peak in sedimentation rate around 2400BP which is not associated with evidence for deforestation, shifts in the balance between terrigenous and authigenic sedimentation, or changes in benthic foraminifera.The mineral magnetic record provides a sensitive indicator of changing sediment sources: during forested periods of reduced terrigenous input it is dominated by authigenic bacterial magnetite, whereas during periods of increased erosion, anti-ferromagetic minerals (haematite and/or goethite) become more important, as well as both paramagnetic minerals and super-paramagnetic magnetite. Analysis of the alkenone, U₃₇^k′, record provides an indication of possible changes in sea surface temperature during the period, but it is premature to place too much reliance on these inferred changes until the indirect effects of past changes in the depth of the halocline and in circulation have been more fully evaluated.The combination of methods used and the results obtained illustrate the potential value of such high resolution near-shore marine sedimentary sequences for recording wide-scale human impact, documenting the effects of this on marine sedimentation and fauna and, potentially, disentangling evidence for human activities from that for past changes in climate.     

Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.     

Modern and Holocene carbonate sedimentology of two saline volcanic maar lakes, southern Australia

The Basin Lakes are two adjacent maar lakes located in the centre of the Western Volcanic Plains District of Victoria, Australia. Both lakes are saline and alkaline; West Basin Lake is meromictic whereas East Basin is a warm monomictic lake. The carbonate mineral suite of the modern offshore bottom sediments of these Basins consists mainly of dolomite and calcite, with smaller amounts of hydromagnesite and magnesite in West Basin and monohydrocalcite in East Basin. The dolomite, hydromagnesite, magnesite, and monohydrocalcite are endogenic in origin, being derived by primary inorganic precipitation within the water columns of the lakes or at the sediment-water interface. The calcite is biologically precipitated as ostracod valves. In addition to the carbonates in the modern offshore (deep-water) sediments, the lakes also contain a girdle of nearshore carbonate hardgrounds. Both beachrock and microbialites (algal boundstones) are present. These modern lithified carbonate units exhibit a wide range of depositional and diagenetic fabrics, morphologies and compositions. In West Basin, the hardgrounds are composed mainly of dolomite, hydromagnesite, and magnesite, whereas dolomite and monohydrocalcite dominate the East Basin sediments. Aragonite, high-Mg calcite, kutnahorite, siderite, and protohydromagnesite also occur in these lithified carbonate units. Stratigraphic variations in the carbonate mineralogy of the Holocene sediment record in the lakes were used to help decipher the palaeochemistry and palaeohydrology of the Basins. These changes, in conjunction with fluctuations in organic remains and fossil content, indicate a pattern of lake level histories similar to that deciphered from other maar lakes in western Victoria.     

Halite oolites and ripples in the Dead Sea, Israel

Clastic features in recent halite deposits are observed along the beaches of an artificially dammed part of the Dead Sea. These features include halite oolites (termed halolites in this paper) and ripples. Halite precipitates initially either at the brine surface or on the floor. It is suggested that moderate increase of wave agitation shifts the balance towards brine-surface crystallization, and keeps the growing halite grains in constant motion. In this way rippled structures are formed. A further increase of wave energy leads to the growth of coated halite grains. The accumulation of the various halite grains along the beach, to form soft rippled floor and oolitic beach ridge is brought about during shoreward winds. During calm periods the bulk of the halite crystallizes directly on the floor. It develops into a hard crust which assumes the morphology of the substrate, including the ripple forms.     

The sedimentology,ichnology and invertebrate palaeontology of the late Silurian Downton Bone Bed

The Downton Bone Bed is a Konzentrat-Lagerstätte deposit located in the Welsh Borderlands, United Kingdom. The Downton Bone Bed is late Silurian, considered to be P?ídolí in age, and occurs within the Platyschisma Shale Member of the Downton Castle Sandstone Formation. The bone bed is exposed at Weir Quarry (Herefordshire), which this study proposes should become established as the type locality for this stratigraphic horizon, due to the destruction of other localities and lack of access to other sites. As Weir Quarry is one of the last remaining exposures of this unit, the objective of this study is to qualitatively describe the sedimentology, ichnology, and invertebrate palaeontology of the bone bed, to enhance the regional understanding of the palaeogeography, depositional environments and depositional processes of the Welsh Borderlands during the late Silurian. Parasequence thickness and frequency, and sedimentary structures such as hummocky cross stratification, observed within the Downton Castle Sandstone Formation, have traditionally been explained to have formed by sea-level oscillations. These are interpreted to have formed entirely by nearshore to shoreface, shallow marine autogenic sedimentary processes, such as storm events (tempestites) and tidal scour. It is interpreted that formation of the Downton Bone Bed occurred as a by-product of these autogenic sedimentary processes, through winnowing and erosion during storm-driven scour and reworking. The low diversity ichno- and invertebrate fauna observed within the Downton Bone Bed is consistent with a nearshore depositional environment and is indicative of a stressed ecosystem due to fluctuating salinity and oxygen levels.     

Palynology of late Middle Pennsylvanian coal beds in the Appalachian Basin

Fossil spores and pollen have long been recognized as valuable tools for identifying and correlating coal beds. This paper describes the palynology of late Middle Pennsylvanian coal beds in the Appalachian Basin with emphasis on forms that assist both intra- and interbasinal coal bed correlation.Stratigraphically important palynomorphs that originate in late Middle Pennsylvanian strata include Torispora securis, Murospora kosankei, Triquitrites minutus, Cadiospora magna, Mooreisporites inusitatus, and Schopfites dimorphus. Taxa that terminate in the late Middle Pennsylvanian include Radiizonates difformis, Densosporites annulatus, Dictyotriletes bireticulatus, Vestispora magna, and Savitrisporites nux. Species of Lycospora, Cirratriradites, Vestispora, and Thymospora, as well as Granasporites medius, Triquitrites sculptilis, and T. securis end their respective ranges slightly higher, in earliest Late Pennsylvanian age strata.Late Middle Pennsylvanian and earliest Late Pennsylvanian strata in the Appalachian Basin correlate with the Radiizonates difformis (RD), Mooreisporites inusitatus (MI), Schopfites colchesterensis–S. dimorphus (CP), and Lycospora granulata–Granasporites medius (GM) spore assemblage zones of the Eastern Interior, or Illinois Basin. In the Western Interior Basin, these strata correlate with the middle-upper portion of the Torispora securis–Laevigatosporites globosus (SG) and lower half of the Thymospora pseudothiessenii–Schopfites dimorphus (PD) assemblage zones. In western Europe, late Middle Pennsylvanian and earliest Late Pennsylvanian strata correlate with the middle-upper portion of the Torispora securis–T. laevigata (SL) and the middle part of the Thymospora obscura–T. thiessenii (OT) spore assemblage zones. Allegheny Formation coal beds also correlate with the Torispora securis (X) and Thymospora obscura (XI) spore assemblages, which were developed for coal beds in Great Britain.     

末次冰盛期-全新世东海陆坡滑塌沉积的地质年代与沉积学证据

基于东海陆坡区OT12-01孔长度为5.35 m沉积物AMS 14C测年、高分辨率粒度分析和XRF岩芯元素扫描数据,识别出了末次冰盛期(LGM)至全新世期间发生的多次滑塌事件。研究发现,OT12-01孔全新世晚期沉积层缺失,LGM至全新世期间呈现AMS 14C年龄模式频繁倒转、沉积物粒度、元素比值垂向上多处突变或"错动"等特征,保存了LGM至全新世非连续的沉积记录。OT12-01孔沉积物主要来源于低海平面时期的长江/黄河物质,OT12-01孔是由中国大陆陆源物质在东海陆架经水动力分选,细颗粒被搬运至东海陆坡后,发生多次滑塌形成。LGM时期物源供给是OT12-01孔形成滑塌沉积的重要因素,末次冰消期海平面快速上升可能是高频滑塌沉积的触发原因,而低海平面时期甲烷水合物溢出、频繁的地震和火山喷发可能是海底滑坡作用发生的诱因。     

Middle Weichselian to Holocene palaeoecology in the eastern Kattegat, Scandinavia: foraminifera, ostracods and 14C measurements

Examination of a 10 m piston core from the eastern Kattegat revealed marine sediments spanning a period from the late Middle Weichselian to the Early Holocene. The oldest marine unit in the core is ¹⁴C-dated to about 30,000–36,000 years BP. These sediments represent the Middle Weichselian Sandnes/Denekamp-Hengelo Interstadial (upper part of stable isotope stage 3) and can be correlated to marine deposits from several localities in the Kattegat region by means of foraminifera. The Late Weichselian deposits comprise sediments from the Oldest Dryas Stadial and the Allerød Interstadial. The intervening periods are not represented in the sequence (hiatuses). Sediments from the latest part of the Early Holocene Preboreal period succeeding the Allerod sequence indicate a considerable hiatus spanning 2000–3000 years around the Weichselian/Holocene boundary. The late Preboreal faunas document a high freshwater inflow during this period, and stable conditions seem not to have been reached in the area until a few hundred years later, in the Boreal period. Comparison with boxcore material from the same site documents a reduction of the energy level of the bottom currents some time between c. 8000 and 800 years BP.     

New faunal and isotopic evidence on the late Weichselian—Holocene oceanographic changes in the Norwegian Sea

Downcore studies of planktonic and benthonic foraminifera and δ¹⁸O and δ¹³C in the planktonic foraminifer Neogloboquadrina pachyderma (sin.) in two piston cores from the southern part of the Norwegian Sea suggest large changes in the oceanic circulation pattern at the end of oxygenisotope stage 2 and in the early part of stage 1. Prior to oxygen-isotope Termination IA (16,000–13,000 yr B.P.), an isolated watermass with lower oxygen content and temperature warmer than today existed below a low salinity ice-covered surface layer in the Norwegian Sea. Close to Termination IA, well-oxygenated deep water, probably with positive temperatures, was introduced. This deep water, which must have had physical and/or chemical parameters different from those of present deep water in the Norwegian Sea, could have been introduced from the North Atlantic or been formed within the basin by another mechanism than that which forms the present deep water of the Norwegian Sea. A seasonal ice cover in the southern part of the Norwegian Sea is proposed for the period between Termination IA and the beginning of IB (close to 10,000 yr B.P.). The present situation, with strong influx of warm Atlantic surface-water and deep-water formation by surface cooling, was established at Termination IB.     

Radiochemistry of sediments from the southern Dead Sea, Jordan

 A sediment core from the southern Dead Sea was analyzed using gamma spectroscopy as well as ²¹⁰Pb dating in order to ascertain if any radioactive contamination could be detected and to determine the sedimentation rates in the area. Results of this study show no presence of man-made radionuclides in the area. Sedimentation rates were determined to be between 0.25 and 0.4 g/cm²/year. (∼0.5 cm/year), which is in line with what would be expected assuming carbonate layers are annual varves. Received: 31 January 1997 · Accepted: 11 March 1997