Sea-level Stands Research Articles

The role of sea-level and climate changes in the assembly of Sri Lankan biodiversity: A perspective from the Miocene Jaffna Limestone

As part of the Western Ghats-Sri Lanka biodiversity hotspot, Sri Lanka harbors a rich and diverse fauna with a considerable number of endemic species, especially in the wet southwestern part of the island. Understanding the origin of this biodiversity requires consideration of the land bridge history between the island and southern Peninsular India. To examine the influence of fluctuating sea levels and climate on island connectivity and isolation during the Miocene, we describe the lithological succession of the Jaffna Limestone in surface outcrops of north(west)ern Sri Lanka and interpret it with respect to palaeoenvironments and sequence stratigraphy. A stack of three marine intervals was identified, which were deposited in seagrass-, coral reef-, and nearshore siliciclastic environments of a land-attached carbonate platform and are separated by caliche and palaeokarst unconformities. They represent high sea-level peaks during the long-term sea-level maximum related to the Middle Miocene Climate Optimum (MMCO). In support of divergence time from Sri Lankan and south Indian species, it is argued that the Palk Isthmus connected Sri Lanka to mainland India prior the MMCO (~17–15 Ma) and after the Middle Miocene Climate Transition (~15–13 Ma), whereas a marine barrier continued to persist during low sea-level stands associated with the Mi2, Mi3a and Mi3 glaciations within this period of time. The early and middle Miocene landbridge connections opened up dispersal opportunities for terrestrial animals. Species migrations via the Palk Isthmus were, however, impacted by a climatic filter, which promoted a high level of ancient endemism on Sri Lanka. Our results indicate that the Sri Lankan sub-center of biodiversity started to evolve in response to increased sea-level and climate variability associated with Antarctic ice dynamics and the initiation of the South Asian monsoon system during the early stage of the current ice house period.

Climate effects on fish diversity in the subtropical bays of Texas

Climate change affects temperatures, sea level, and salinities, all of which can affect fish distributions. In order to assess the impact of climate change on the marine fish communities of Texas, fish diversity response to climate variables was modeled. Leveraging 33 years of gillnet survey data from eight major bays along the coast of Texas, asymptotic Shannon diversity was estimated for each bay, season, and year using rarefaction analysis. This allowed for the estimation of spatial, temporal, and seasonal trends in fish diversity. In order to assess the impact of climate-related variables on the fish communities of Texas, we associated the Shannon diversity index with environmental variables using a repeated measures model approach. We found significant increasing trends in fish diversity across all eight bays in fall and six of eight bays in spring. Among the variables identified as significant, temperature, salinity, and sea level stood out as most important for driving the increase in fish diversity. Our results suggest that observed increases may be attributable to changing habitat availability resulting from sea-level rise and increasing winter temperatures. Mangrove expansion and warmer winters are likely allowing for range expansion by tropical species, driving the observed increase in fish diversity.

Shales of Palaeo-Mesoproterozoic Vindhyan Basin, central India: insight into sedimentation dynamics of Proterozoic shelf

AbstractThe Vindhyan Supergroup represents the largest Proterozoic sedimentary basin fill in the Indian shield. In addition to some significant palaeobiological discoveries, the sedimentary sequence of the Vindhyan, particularly its argillaceous intervals, holds crucial information for our understanding of sedimentation dynamics in Proterozoic clastic shelves. Here we attempt an extensive, although not exhaustive, review of the physical characteristics of six argillaceous (shale) intervals (Arangi, Koldaha, Rampur, Bijaygarh, Rewa and Sirbu shale) from the Son valley sector, Vindhyan Basin, augmented with new observations to unravel the status of current understanding in terms of palaeo-flow dynamics, shelf sedimentation processes and dispersal pattern, depositional cyclicity and basinal tectonics. The sedimentary attributes of Vindhyan shales reveal their deposition largely in relative bathymetry fluctuating from distal shoreface or inner shelf (near to fair-weather wave base) to distal shelf below storm wave base. More often than not, the Vindhyan shelf was storm-infested and the operation of both storm-generated return flow and Coriolis-force-guided geostrophic currents are documented from different stratigraphic intervals of argillaceous successions. The thick arenaceous intervals interrupting the deposits of the Koldaha, Rewa and Sirbu shales at multiple stratigraphic levels indicate the presence of a fan delta and braided fluvial system during intermittent regressive stands of sea level or event deposition during a sea-level highstand, respectively. Based on facies pattern and flow vectors, a rift-related half-graben model is inferred for Arangi and Koldaha shale and a low-gradient stable-shelf model with well-defined energy gradient is proposed for successions from Rampur shale onwards.

New Geomorphological and Historical Elements on Morpho-Evolutive Trends and Relative Sea-Level Changes of Naples Coast in the Last 6000 Years

This research aims to present new data regarding the relative sea-level variations and related morpho-evolutive trends of Naples coast since the mid-Holocene, by interpreting several geomorphological and historical elements. The geomorphological analysis, which was applied to the emerged and submerged sector between Chiaia plain and Pizzofalcone promontory, took into account a dataset that is mainly composed of: measurements from direct surveys; bibliographic data from geological studies; historical sources; ancient pictures and maps; high-resolution digital terrain model (DTM) from Lidar; and, geo-acoustic and optical data from marine surveys off Castel dell’ Ovo carried out by using an USV (Unmanned Surface Vehicle). The GIS analysis of those data combined with iconographic researches allowed for reconstructing the high-resolution geomorphological map and three new palaeoenvironmental scenarios of the study area during the Holocene, deriving from the evaluation of the relative sea-level changes and vertical ground movements of volcano-tectonic origin affecting the coastal sector in the same period. In particular, three different relative sea-level stands were identified, dated around 6.5, 4.5, and 2.0 ky BP, respectively at +7, −5, and −3 m MSL, due to the precise mapping of several paleo-shore platforms that were ordered based on the altimetry and dated thanks to archaeological and geological interpretations.

The lagoon geomorphology of pearl farming atolls in the Central Pacific Ocean revisited using detailed bathymetry data

The lagoons of seven French Polynesia and Cook Islands pearl farming atolls (Raroia, Takume, Mopelia, Takapoto, Ahe, Takaroa and Manihiki) were surveyed using multibeam and mono-beam sounders. From the detailed bathymetry, morphometric variables (average and maximum depth, frequency-area of depth, lagoon area and volume) are computed and compared. Remarkable geomorphological structures highlighted by bathymetric variations include deep reticulated structures and pinnacles. The seven atolls appear very different in abundance, size and density of these entities. Considering them as markers of the geological, sedimentological and eustatic processes that shape atoll lagoons, they are discussed in the context of the general theory of atoll lagoon formations involving karstic dissolution during Pleistocene or earlier low sea-level stands. In terms of pearl farming management, accurate bathymetric maps help pearl oyster wild stock assessment, development of circulation and biogeochemical models, better lagoon zoning and strategy to remove pearl farming derelict gears.

Sea-level changes controlled detrital sediment inputs to the Bicol Shelf in the western Philippine Sea since 150 ka

Detrital sediments derived from the Philippine Islands are one of the main sources of deep-sea sediments in the western Philippine Sea. However, systematic research on their characteristics and transport mechanisms are lacking. We used parametric end-member analysis to quantitatively partition the grain size of detrital sediments in core MD06-3052 from the Bicol Shelf in the western Philippine Sea; three end-members EM1, EM2, and EM3, whose respective modes were at 2, 10, and 45 µm, were separated. We also measured the Sr and Nd isotopic compositions of different size fractions ( 20 µm) of the detrital sediments and the results showed that the detrital sediments mainly originate from the Philippine Islands. Components EM1 and EM2 are transported to the Bicol Shelf mainly by surface and bottom currents from the islands, and component EM3 is delivered by gravity flow from the exposed shelf during low sea-level stands. The content of the total detrital fraction and the three end-members, as well as the mass accumulation rates (MARs) of the coarse detritus (EM2 and EM3), were considerably higher during glacial periods (40–14 ka and 150–130 ka) than during other intervals; the glacials corresponded to a low sea level, while the MAR of the fine detritus (EM1) did not increase remarkably during 40–14 ka. We therefore concluded that the input of coarse detritus to the Bicol Shelf from the islands was mainly controlled by sea-level change. Variations of the input of fine-grained detritus (EM1) was influenced not only by sea level but also by ocean currents and regional precipitation. Overall, our results help understand “source-to-sink” processes in the western Pacific marginal seas and their response to global change.

Already too late? Massive trade in Indian star tortoises (Geochelone elegans) might have wiped out its phylogeographic differentiation

Abstract Geochelone elegans is one of the most heavily traded tortoise species of the world, and confiscated tortoises are frequently released into the wild, without knowledge about their origin. Using for the first time samples from Pakistan and Sri Lanka, we examined phylogeographic differentiation of G. elegans using 2289 bp of mitochondrial DNA. We found weak intraspecific differentiation without a clear geographic pattern. We suggest that natural phylogeographic differentiation may have been already destroyed by massive releases of confiscated non-native tortoises. The presence of two distinct clades on Sri Lanka, however, could also be the result of a natural range expansion of a mainland lineage into the distribution range of a lineage endemic to Sri Lanka during Pleistocene low sea level stands. We propose that a systematic screening of the genetic differentiation of wild G. elegans should be conducted across its entire distribution range to provide a sound basis for the relocation of confiscated tortoises.

Variations in eastern Mediterranean hydrology during the last climatic cycle as inferred from neodymium isotopes in foraminifera

The Nd isotopic compositions (εNd) of mixed planktonic foraminifera have been analyzed in two sediment cores collected in the Nile deep-sea fan in order to reconstruct past εNd of the Eastern Mediterranean Deep Water (EMDW) and to assess the relative contributions of Nile discharge and Modified Atlantic Water (MAW) inflow to the Eastern Mediterranean Sea hydrology, as well as their potential control on anoxic events over the last climatic cycle. The two foraminiferal εNd records are similar and display an increase in εNd values during the African Humid Periods. Superimposed on this precession-forced variability (insolation received by the Earth at low latitudes), the record of variations in foraminiferal εNd indicates a 2-unit decrease in εNd during the interglacial Marine Isotope Stages (MIS) 5 and 1 compared to glacial MIS6, 4, 3 and 2. The εNd results suggest that the long-term glacial to interglacial changes in Nd isotopic composition of EMDW were not entirely induced by variations in Nile River discharge and Saharan dust inputs. Decreases in εNd during MIS5 and MIS1 interglacials indicate an increase in the contribution of unradiogenic MAW to the eastern Mediterranean Sea related to high sea-level stands and greater seawater exchange between the North Atlantic and Mediterranean basins. In addition, radiogenic seawater εNd values observed during African Humid Periods (and sapropel events) are associated with an intensification of Nile discharge and an increase in residence time of deep-water masses in the eastern Mediterranean Sea, which induces an increase in the interaction between deep-water masses and radiogenic sediments along the margin of the eastern Mediterranean Sea. Results confirm that an intensification of the hydrological exchanges between the western and eastern Mediterranean basins during high sea-level stand and the subsequent higher proportion of Atlantic Water in the Levantine Basin may have preconditioned the eastern Mediterranean Sea to sapropel depositions during the last climatic cycle.

A paradigm for the evolution of human features: Apes trapped on barren volcanic islands

The aquatic ape hypothesis for human evolution can account for all the traits that distinguish humans from chimpanzees. This scientific paradigm has been considered impossible. It would require that human ancestors maintained a semiaquatic lifestyle for millions of years, whereas hominin fossils indicate relatively dry terrestrial environments. Here I propose a marine aquatic evolution that is speculative, but compatible with all the fossil and genetic evidence. In this hypothesis, hominins evolved from chimpanzee-like apes that became stranded on proto-Bioko — new volcanic islands with no terrestrial foods available. The apes were forced to eat shellfish and seaweed. From wading in water on two legs to obtain food, their bodies evolved to become bipedal. Naked skin, blubber, and protruding noses were also aquatic adaptations. Brain-size increase resulted from marine fatty acid DHA. Some of these hominins escaped to mainland Africa and their bipedal descendants are recorded at the famous fossil sites. The volcanic islands grew and evolved into Bioko, and the hominins that remained there evolved into Homo sapiens. They gave up their marine diet and semiaquatic habitat after food became available on the evolving island. Then, during one of the low sea-level stands in the Pleistocene epoch, humans walked to the mainland on the emergent Bioko land bridge. Unlike earlier aquatic ape ideas, the Bioko scenario can be tested by DNA. If the human genome includes a retrovirus that is otherwise only found in endemic animals on Bioko, it would show that our ancestors came from there. Unfortunately, Bioko and west-central Africa are not interesting to traditional paleoanthropologists, because they do not contain fossils.

Parallels between stream and coastal water quality associated with groundwater discharge.

Groundwater-surface water interactions drive water quality in both streams and the coastal ocean, where groundwater discharge occurs in streams as baseflow and along the coastline as submarine groundwater discharge (SGD). Groundwater contributions to streams and to the coastal ocean were quantified in three urban streams in Kāneʻohe Watershed, Hawaiʻi. We used radon as a groundwater tracer to show that baseflow contributions to streams ranged from 22 to 68% along their reaches leading to the coast of Kāneʻohe Bay. Total SGD was 4,500, 18,000, and 23,000 m3/day for the northwest, central, and southern sectors of the bay, respectively. Total groundwater (stream baseflow + SGD) dissolved nutrient fluxes were significantly greater than those sourced from stream surface runoff. The studied streams exhibited increasing nutrient levels downstream from groundwater inputs with high nutrient concentrations, negatively impacting coastal water quality. SGD dynamics were also assessed during the anomalously high perigean spring tides in 2017, where SGD was four times greater during the perigean spring tide compared to a spring tide and resulted in strong shifts in N:P ratios, suggesting that rising sea level stands may disrupt primary productivity with greater frequency. This study demonstrates the importance of considering baseflow inputs to streams to coastal groundwater budgets and suggests that coastal water quality may be improved through management and reduction of groundwater contaminants.

Paleoceanographic evolution of the Japan Sea over the last 460 kyr – A coccolithophore perspective

Abstract Changes in the intensity of the influx of the Tsushima Warm Current (TWC) in the south-central part of the Japan Sea (JS), or East Sea in Korean, were reconstructed for the last 460 kyr at IODP Site U1427 using the composition and abundance of the coccolithophore assemblage. In addition, the recent distribution of coccolithophore taxa in the JS and the East China Sea was assessed using electron microscopy. Coccolithophore assemblages, dominated by Emiliania huxleyi and Gephyrocapsa species, and coccolith abundance reveal a strong relationship between sea level and ocean variability over the last five glacial/interglacial cycles, in good agreement with planktic foraminiferal data. Three different circulation modes based on calcareous nannofossil and foraminifera TWC indicators were proposed for the JS. Coccolith production was low and TWC indicators (i.e., Gephyrocapsa oceanica, Calcidiscus leptoporus s.l., and Helicosphaera carteri) absent due to the isolation of the JS during glacials in response to global sea level falls (Mode 1). In contrast, coccolith abundance and TWC indicators reach a maximum due to the most intense TWC flow through the Tsushima Strait during interglacials (Mode 3). Intermediate conditions (Mode 2) are characterized by moderate/high coccolith numbers, presence of TWC coccolith indicators, and rare TWC planktic foraminifera indicators. This mode resulted in intermittent variations in the contribution of the TWC and East China Sea coastal water due to relatively low sea level stands (ca. −90 m to −20 m). Coccoliths dominated the carbonate sequence prior to MIS 8 and were major contributors to the total carbonate of the sediment at Site U1427, suggesting high coccolithophore productivity and a bloom-type environment during MIS 11 and 9. These changes in the carbonate chemistry caused by glacio-eustacy in the JS at the northwest margin of the Pacific Ocean should be considered in future paleoceanographic and paleoclimate models.

Shelf-edge delta overreach at the shelf break can guarantee the delivery of terrestrial sediments to deep water at all sea-level stands

How and when sediment moves from terrestrial sources to deep-water sinks is a significant area of research. We have used an array of seismic, borehole, and gravity core data sets to explore the timing and magnitude of sediment-routing to Pearl River slope over the last 478 k.y. As predicted by existing sequence stratigraphic models, most sediment dispersal to deep water is shown to have occurred during glacial sea-level falls; however, clastic detritus was still being transported into deep water during interglacial sea-level rises. We suggest that sediment routing to deep water during interglacial sea-level rise is caused by summer monsoon strengthening and resultant warmer and wetter climates, both of which have enhanced effective precipitation and sediment supply. Although some models for the delivery of sediment to deep-water basins stress the importance of proximity of canyon heads and coeval shorelines, we observed that sediment routing to deep water could occur regardless of the distance between channel head and coeval shorelines. In the present case, the success of delivery is related to the combined effects of (1) the short duration and high amplitude of sea-level oscillations during the past 478 k.y. and (2) the enhanced sediment supply caused by more humid climates and greater temperature difference between glacial and interglacial period. This hypothesis is supported by (1) observations that outer Pearl River deltas prograded as an apron over preexisting shelf edges for 10–15 km (6–9 mi) and (2) the occurrence of slope channels extending back to prodelta reaches of Pearl River shelf-edge deltas.

Ice ages and butterflyfishes: Phylogenomics elucidates the ecological and evolutionary history of reef fishes in an endemism hotspot.

For tropical marine species, hotspots of endemism occur in peripheral areas furthest from the center of diversity, but the evolutionary processes that lead to their origin remain elusive. We test several hypotheses related to the evolution of peripheral endemics by sequencing ultraconserved element (UCE) loci to produce a genome‐scale phylogeny of 47 butterflyfish species (family Chaetodontidae) that includes all shallow water butterflyfish from the coastal waters of the Arabian Peninsula (i.e., Red Sea to Arabian Gulf) and their close relatives. Bayesian tree building methods produced a well‐resolved phylogeny that elucidated the origins of butterflyfishes in this hotspots of endemism. We show that UCEs, often used to resolve deep evolutionary relationships, represent an important tool to assess the mechanisms underlying recently diverged taxa. Our analyses indicate that unique environmental conditions in the coastal waters of the Arabian Peninsula probably contributed to the formation of endemic butterflyfishes. Older endemic species are also associated with narrow versus broad depth ranges, suggesting that adaptation to deeper coral reefs in this region occurred only recently (<1.75 Ma). Even though deep reef environments were drastically reduced during the extreme low sea level stands of glacial ages, shallow reefs persisted, and as such there was no evidence supporting mass extirpation of fauna in this region.

Spotlight on islands: on the origin and diversification of an ancient lineage of the Italian wall lizard Podarcis siculus in the western Pontine Islands

Groups of proximate continental islands may conceal more tangled phylogeographic patterns than oceanic archipelagos as a consequence of repeated sea level changes, which allow populations to experience gene flow during periods of low sea level stands and isolation by vicariant mechanisms during periods of high sea level stands. Here, we describe for the first time an ancient and diverging lineage of the Italian wall lizard Podarcis siculus from the western Pontine Islands. We used nuclear and mitochondrial DNA sequences of 156 individuals with the aim of unraveling their phylogenetic position, while microsatellite loci were used to test several a priori insular biogeographic models of migration with empirical data. Our results suggest that the western Pontine populations colonized the islands early during their Pliocene volcanic formation, while populations from the eastern Pontine Islands seem to have been introduced recently. The inter-island genetic makeup indicates an important role of historical migration, probably due to glacial land bridges connecting islands followed by a recent vicariant mechanism of isolation. Moreover, the most supported migration model predicted higher gene flow among islands which are geographically arranged in parallel. Considering the threatened status of small insular endemic populations, we suggest this new evolutionarily independent unit be given priority in conservation efforts.

Late Cretaceous endemic shallow-marine gastropod genera of the northeast Pacific: biodiversity and faunal changes

Endemic genera of shallow-marine gastropods in the Cretaceous Northeast Pacific Subprovince (NEP), extending from Alaska to northern Baja California Sur, Mexico, are tabulated and discussed in detail for the first time. None are known in Lower Cretaceous or Cenomanian strata, but 43 genera, nearly two-thirds of which are neogastropods, are recognized in Upper Cretaceous strata. Their first appearance was at the beginning of the Turonian, which coincided with the warmest time of the Cretaceous and one of its highest sea-level stands. Fourteen new subtropical endemic genera appeared then, and 10 (71%) were neogastropods. Tethyan-influenced thermophilic mollusks (nerineid, acteonellid, neritid, and cypraeoidean gastropods, as well as rudistid bivalves) were present. A turnover at the Turonian/Coniacian boundary occurred when cooler waters migrated southward, resulting in the subtropical endemics being abruptly and nearly completely replaced by 10 warm-temperate new endemic neogastropods, which commonly had long-living lineages persisting through the Campanian or early Maastrichtian. Eight (80%) of these new genera were neogastropods. During these cooler water times in the Coniacian and nearly all of the Santonian, there was an absence (“gap”) of Tethyan-influenced and other thermophile mollusks. New endemic genera, were added during an origination event in the early Campanian and also during another one in the late Campanian. Fewer and fewer new neogastropod genera appeared during each of these origination events, whereas new endemic genera of non-neogastropods increased. Rudistids and thermophilic mollusks also returned in the Campanian. Most of the post-Turonian endemic genera went extinct at a turnover at the end of the early Maastrichtian (=“Middle Maastrichtian Event”), rather than at the K/Pg boundary mass-extinction event. Two new endemic genera, both neogastropods, originated just before the end of the Maastrichtian. They and three other Cretaceous endemic gastropod genera occur also in the NEP Cenozoic record, thereby imparting a somewhat transitional aspect between these two faunas. The tectonically transported fauna of the middle Albian Alisitos Formation in northern Baja California, Mexico is confirmed to have lived in the tropical-water Caribbean Biotic Province of the Tethyan Realm.

On the long-lasting sequences of coral reef terraces from SE Sulawesi (Indonesia): Distribution, formation, and global significance

Many islands of the eastern Indonesian Archipelago exhibit Late Cenozoic sequences of coral reef terraces. In SE Sulawesi, on the Tukang Besi and Buton archipelagos, we identified 23 islands bearing such sequences. Remote sensing imagery and field mapping combined to U/Th and 14C dating enable to establish a chronologic framework of the reef terrace sequences from Wangi-Wangi, Buton as well as on the neighbouring, smaller islands of Ular, Siumpu and Kadatua. We identified the terraces from the last interglacial maximum (MIS 5e) at elevations lower than 20 m except on W Kadatua where it is raised at 34 ± 5 m. Such elevations yield low to moderate Upper Pleistocene uplift rates (<0.3 mm yr−1). On SE Buton Island, a sequence culminates at 650 m and includes at least 40 undated strandlines. Next to this exceptional sequence, on the Sampolawa Peninsula, 18 strandlines culminate at 430 m. Dated samples at the base of this sequence (<40 m) yield mean Middle Pleistocene uplift rates of 0.14 ± 0.09 mm yr−1. Extrapolation of these uplift rates compared to the geological setting suggests that the sequences of the Sampolawa Peninsula provide a record of sea-level high-stands for the last 3.8 ± 0.6 Ma. The sequences on SE Buton Island therefore constitute the best preserved long-lasting geomorphic record of Plio-Quaternary sea-level stands worldwide.

MIS 5e relative sea-level changes in the Mediterranean Sea: Contribution of isostatic disequilibrium

Sea-level indicators dated to the Last Interglacial, or Marine Isotope Stage (MIS) 5e, have a twofold value. First, they can be used to constrain the melting of Greenland and Antarctic Ice Sheets in response to global warming scenarios. Second, they can be used to calculate the vertical crustal rates at active margins. For both applications, the contribution of glacio- and hydro-isostatic adjustment (GIA) to vertical displacement of sea-level indicators must be calculated. In this paper, we re-assess MIS 5e sea-level indicators at 11 Mediterranean sites that have been generally considered tectonically stable or affected by mild tectonics. These are found within a range of elevations of 2–10 m above modern mean sea level. Four sites are characterized by two separate sea-level stands, which suggest a two-step sea-level highstand during MIS 5e. Comparing field data with numerical modeling we show that (i) GIA is an important contributor to the spatial and temporal variability of the sea-level highstand during MIS 5e, (ii) the isostatic imbalance from the melting of the MIS 6 ice sheet can produce a >2.0 m sea-level highstand, and (iii) a two-step melting phase for the Greenland and Antarctic Ice Sheets reduces the differences between observations and predictions. Our results show that assumptions of tectonic stability on the basis of the MIS 5e records carry intrinsically large uncertainties, stemming either from uncertainties in field data and GIA models. The latter are propagated to either Holocene or Pleistocene sea-level reconstructions if tectonic rates are considered linear through time.

Eurasian contribution to the last glacial dust cycle: how are loess sequences built?

Abstract. The last 130 000 years have been marked by pronounced millennial-scale climate variability, which strongly impacted the terrestrial environments of the Northern Hemisphere, especially at middle latitudes. Identifying the trigger of these variations, which are most likely associated with strong couplings between the ocean and the atmosphere, still remains a key question. Here, we show that the analysis of δ18O and dust in the Greenland ice cores, and a critical study of their source variations, reconciles these records with those observed on the Eurasian continent. We demonstrate the link between European and Chinese loess sequences, dust records in Greenland, and variations in the North Atlantic sea ice extent. The sources of the emitted and transported dust material are variable and relate to different environments corresponding to present desert areas, but also hidden regions related to lower sea level stands, dry rivers, or zones close to the frontal moraines of the main Northern Hemisphere ice sheets. We anticipate our study to be at the origin of more sophisticated and elaborated investigations of millennial and sub-millennial continental climate variability in the Northern Hemisphere.

ENTREPRENEURAL FIGURE OF MOUNT AGUNG TREKKING GUIDES

Mount Agung with an altitude of 3,142 meters from sea level stood at the coordinates of 8020'27 "S 115030'12" E, circled along 105 kilometers (65 miles), and classified as a volcanic type monoconic strato. The highest mountain in Bali Province was located in Selat District, Karangasem Regency. It got a last major eruption in 1963 and since then began to be climbed by climbers/tourists. Because in 1970s and 1980s some climbers/tourists very often got lost and accidents to death, since the 1990s a number of the local community members took initiative to serve the climbers/tourists who want to explore the mountain known as holy and sacred one. This study was conducted in order to understand and describe the pioneering aspects of entrepreneurial figure of the related trekking guides. It was a qualitative study with a qualitative data analysis.&#x0D; The results of this study showed that because Mount Agung was not an ordinary mountain but full of myths and stories that were supernatural, so the entrepreneurial practices of the Selat Village community appeared not only to serve the climbers/trekkers as usual but also to preserve the environment and ensure their safety as there were so many taboos in the climbing/trekking. All these facts can be seen from the depiction of the stories and experiences of the local climbing/trekking guides who had been doing their work for years. As entrepreneurs, they looked for income but, above all, environmental sustainability and the spirituality of the mountain werw not neglected.

Morphology of the Raised Shore Platforms along the Coastline between Daghmar and Dhabab, Sultanate of Oman

Raised shore platforms, are rocky surfaces formed by wave action and subaerial weathering during global high sea level stands. The present height of the raised shore platforms is attributed to several factors, mainly to eustatic sea level changes, isostatic changes in the relative level of land and sea, and vertical tectonic activities. The aim of this study is to investigate the detailed morphology of the raised shore platform along the rocky coastline between Daghmar and Dhabab, in the southeastern part of Muscat Governorate. The study also intends to establish a tentative chronology of the raised shore platforms development. The methodology is based on field observation and documentation, along with satellite and aerial photographs analysis. The results have shown that the study area has a sequence of five successive, well developed raised shore platforms and well preserved, except the platform at 10m altitude which is only found in isolated fragments. The formation of the raised shore platforms has been affected by a number of constructive factors including tectonic activity, and destructive factors such as fluvial action and subaerial weathering. No absolute dating has been reported or can be obtained from the study area, due to its erosional nature. However, dating from the shorelines adjacent to the study area, ranging in heights from 3 to 15m above sea level, revealed a narrow range of 26,400 to 29,600 years. This period coincides with the last glaciations when the sea level was at about 75m below the present level, and thus did not match with the altitudes of the platforms. This suggests that the platforms could be belong to the last interglacial high sea level, when the sea level stood at about 6m above the present level. Based on this scenario, the study concludes that the coastline of the study area has not experienced any significant uplift during the Late Quaternary.