Sand Sea Research Articles

Burial of a sand sea: Heterogeneous compaction and cementation of the jurassic Etjo Formation, Namibia and what it tells

Aeolian sandstones are capable of forming excellent reservoir rock due to their textural and compositional maturity. Often spanning across large areas, such formations may however experience spatial variability in burial and temperature exposure potentially leading to a heterogeneous diagenesis and subsequent reservoir quality. To assess such potential variability, this case study focusses on the diagenesis of the aeolian units of the Lower Jurassic Etjo Formation in Namibia, exposed at three key localities lying >100 km apart from each other. The Etjo Formation has experienced two major burial phases controlled by the emplacement of (I) Jurassic Karoo and (II) Lower Cretaceous Paraná-Etendeka volcanic rocks separated by an intervening exhumation phase. Petrographic analysis reveals very different rock properties between the localities with respect to intergranular volumes (IGV), intensity of quartz cementation, and preserved porosities. Average IGV and quartz cement values are 30.7 % and 24.3 % at Gamsberg, 23.7 % and 6.5 % at Waterberg and 19.7 % and 15.4 % at Mt. Etjo. Point-counted intergranular porosity values are on average 2.6 % (Gamsberg), 10.8 % (Waterberg), and 1.5 % (Mt. Etjo). Waterberg samples had an on average 72 % larger nucleation surface area available for quartz cement growth than samples from Mt. Etjo. The higher quartz cement volumes at Mt. Etjo therefore argue for a higher thermal exposure than at Waterberg. This is supported by kaolinite-to-illite transformation only occurring at Mt. Etjo. We attribute the higher temperature signature to the proximity of Mt. Etjo to the center of lower Cretaceous Paraná-Etendeka volcanism and related elevated thicknesses of the lava pile or heat flow increase. At Gamsberg, there is evidence for a quartz cement generation that formed during the Jurassic. This earlier cement stabilized the grain framework and preserved the IGV during the following Etendeka burial event. The Etjo Formation provides an exceptional example for the wide range of very low to very high degrees of compaction and cementation that can occur within an otherwise homogeneous, texturally and compositionally mature sandstone formation. This study underscores the importance of accounting spatial variations in burial depths and temperatures when predicting the diagenetic properties of reservoir rocks.

A Language Island in a Sea of Sand

A Language Island in a Sea of Sand

An island in a sea of sand: a first checklist of the herpetofauna of the Serra da Neve inselberg, southwestern Angola.

The Serra da Neve inselberg in Namibe Province, southwestern Angola is the second highest peak of Angola with an elevation of 2489 m. It remains one of the least explored regions in the country, despite several endemic species having been recently described from this inselberg. Here we provide an inventory of the amphibian and reptile species ocurring in Serra da Neve and compare its fauna with that of the surrounding habitats at lower elevations. We also examine the phylogenetic affinities of the inselberg taxa. A total of 59 herpetological taxa were recorded for the Serra da Neve inselberg and its immediate surroundings. These include 11 species of amphibians, belonging to nine genera and seven different families, and 48 species of reptiles, belonging to 32 genera and 12 families. Of these, one amphibian and seven reptiles from seven different genera are strictly endemic, making the inselberg the richest region in southwestern Africa with respect to strict endemics, with one endemic reptile taxa per 127 km2. Not surprisingly, most of the recorded taxa belong to clades that are endemic, or at least strongly associated, with southern Africa, but two are representatives of central African clades, and another two are more closely related to eastern African highland taxa. We also provide comments on the threats to the conservation of this endemic-rich inselberg.

Aeolian dynamics at the northern edge of Deliblato (Banat) Sand Sea, Vojvodina, Serbia, at the time of the last deglaciation

Abstract The Deliblato (Banat) Sand Sea, which is one of the largest areas of аeolian sand in Europe, is located near the Iron Gate, which marks the crossing of the Danube River through the biggest gorge of this river. Here, Danubian alluvium has served as the sand source for the Banat Sand Sea, which was formed primarily through southeasterly (Košava) winds. Utilizing a multi-proxy approach, the objective of this study is to gain a better understanding of the environmental dynamics of the Banat Sand Sea. To achieve this goal, we conducted an analysis of an archive representing an approximately 20-m-thick dune formation on the northern edge of this dune field. Using optically stimulated luminescence (OSL) dating, we calculated aeolian sedimentation rates and dune ages. Sand was deposited here approximately between 17 ka and 13 ka. Magnetic susceptibility, grain size, and colorimetric analyses were interpreted in terms of local paleoenvironmental conditions. Calculated sedimentation rates (SR) indicate intensive aeolian deposition during the study period that range from 483 cm/ka to 502 cm/ka. We compared our data with regional and other European archives, as well as with climatic variations recorded in the Greenland ice core North Greenland Ice Core Project (NGRIP).

Landscape evolution and hydrology at the Late Pleistocene archaeological site of Narabeb in the Namib Sand Sea, Namibia

The Namib Sand Sea (NSS) in Namibia is known to preserve a wide variety of Pleistocene-age archaeological sites. However, few Middle Stone Age (MSA) sites in this region have been systematically investigated and basic questions around chronology and technological organization remain open. Here we examine Narabeb, an open air MSA surface site exposed in an interdune pan, ∼30 km into the northern NSS. Narabeb was first documented in the 1970s, and then re-examined in 2021 and 2022 by members of this team. Lithic technological analysis combined with a geomorphological description of the site, palaeoenvironmental interpretation of fine-grain water-lain sediments, and luminescence ages from northern and southern locations on the Narabeb pan provide some of the first understanding of human-environmental interactions and estimates of chronology from the later-Middle and Late Pleistocene in the NSS. In addition, we apply a quantitative approach to aeolian linear dune accumulation and extension to explore possible scenarios for landscape development at this site, in order to better understand the former water course(s) affecting the area. The new chronology suggests this site contained standing water at, or just after, the MIS 7/6 transition, and again at, or just after, the end of MIS 6 into early MIS 5. The timing of greater phases of water availability have some overlap with the speleothem growth record at Rössing Cave, situated ∼90 km north of the NSS (and ∼135 km north of Narabeb). Our results provide the foundation for larger, regional-scale analyses of early human adaptive strategies in this unique environment within Southern Africa.

Fingerprinting aeolian sediment sources in the Mu Us Sandy Land using the MixSIAR model

Understanding and quantifying aeolian sediment sources in sand seas is imperative to elucidate their formation mechanism and promote ecological restoration, particularly in transitional zones between agricultural farming and animal grazing. Despite considerable efforts to identify the provenance of the Mu Us Sandy Land (Mu Us), a clear boundary demarcating the provenance differences between its western and eastern regions remains elusive. Furthermore, the quantitative contributions of its potential source areas are yet to be determined. This study elucidated these aspects using robust source indicators and the MixSIAR fingerprinting model, underpinned by geochemical data. Utilizing provenance indicators such as the K/Ba, K/Rb, Ba/Sr, and Rb/Sr ratios, this study identified the line connecting Angsu and Huanghaojie Town as the clear boundary demarcating the provenance differences between the western and eastern Mu Us. The eastern Mu Us's coarse sand primarily derives from underlying sandstones (70.5%) and local fluvio-lacustrine deposits (29.5%), while the western region's coarse sand predominantly originates from Yellow River (YR) sediments in the Yinchuan Basin, transported from the Northeastern Tibetan Plateau (NTP) (82.2%), and local fluvio-lacustrine deposits (17.8%). Similarly, the Mu Us's fine sand mainly originates from local fluvio-lacustrine deposits, contributing 66.5% and 67.6% to the fine sand in the eastern and western regions, respectively. Under strong westerly winds, Gobi deposits from upwind areas contribute 33.5% and 32.4% of fine sediments to the eastern and western Mu Us, respectively. The spatial heterogeneity of material sources in the Mu Us highlights the combined influence of fluvial and wind processes. Lacustrine deposits play a crucial role in the sediment provenance of the Mu Us. This study demonstrates that the MixSIAR model constitutes an effective approach for quantitative provenance research in deserts located in climatic transitional zones worldwide.

Probability density distributions of morphological parameters of barchan dunes and their responses to the climate environment

Barchan dunes are a common aeolian geomorphology in sand seas on Earth and Mars. They occur primarily as barchan dune groups. Obvious regional differences occur in the size distribution of dune swarms in different dune fields because of sediment grain size, regional airflow, sand flux, and surface conditions. To explore dune size distributions in different barchan dune fields and clarify the effects of climate on barchan dune morphometry, we used high-resolution remote sensing images and extended time-series meteorological data. Barchan dune fields were located in the southeast edge of the Taklimakan Desert, the western and southern parts of the Qaidam Basin Desert, the Gonghe Basin Sandy Land, and the sand belt connecting the Badain Jaran Desert and the Tengger Desert. Our results revealed the probability density distribution of morphological parameters of barchan dunes, correlations among parameters, and responses to wind regime. The main conclusions are: (1) Probability density distributions of the lengths of windward and lee slopes, the lengths of the two horns, and the dune width, height, and spacing in different deserts followed a log-normal distribution function. (2) Good correlations were found among the dune morphological parameters; width and height, windward slope length and width, and height and spacing showed positive proportionality, and the basal area and the product of width and height were linearly correlated in a double logarithmic coordinate system. (3) Good correspondence was found between dune asymmetry and regional wind conditions, which can be explained by Tsoar's model. Morphological parameters of barchan dunes were linearly and positively correlated with the drift potential. These results provide essential data for further study of the morphological thresholds for dune-dune interactions and elucidation of the mechanisms of interaction among barchan dunes.

Spectral imaging of grass species in arid ecosystems of Namibia

Grasslands across the African continent are under pressure from climate change and human activities, particularly in arid ecosystems. From a remote sensing perspective, these ecosystems have not received much scientific attention, especially in Namibia. To address this knowledge gap, various remote sensing methods were implemented using new generation spaceborne imaging spectrometers amongst others. Therefore, this research provides a first methodological approach aimed at mapping and evaluating the distribution of grasslands within two private nature reserves, namely, the NamibRand Nature Reserve (NRNR) and ProNamib Nature Reserve (PNNR) with surrounding farmlands on the edge of Namib Sand Sea. The multi-sensor approach utilizes Mixture Tuned Matched Filtering (MTMF) and incorporated spectral information collected in the field to analyze grasslands. The research involves a sensor comparison of multispectral Sentinel-2 and PlanetScope data, hyperspectral data from Environmental Mapping and Analysis Programme (EnMAP) and PRecursore IperSpettrale della Missione Applicativa (PRISMA) and an additional data fusion product derived from Sentinel-2 and EnMAP imagery based on a Smoothing Filter-based Intensity Modulation Hypersharpening method (SFIM-HS). Additionally, a unique spectral library of collected field spectra was established and inter-species spectral separability and intra-species spectral homogeneity was analyzed. This library presents newly published spectra of individual species. Due to dry initial conditions, the calculated spectral separability of individual grasses is limited, making only a mean endmember feasible for partial unmixing. The validation results of satellite comparison show that data fusion products (R2 = 0.51 with Normalized Difference Vegetation Index (NDVI); R2 = 0.66 with Soil Adjusted Vegetation Index (SAVI)) are more suitable for mapping arid grasslands than multispectral or hyperspectral data (all R2 < 0.35). More research is required and potential methodological adjustments are discussed to further investigate the spatio-temporal dynamics of arid grasslands and to aid conservation efforts in the Greater Sossusvlei-Namib Landscape in line with the United Nations Decade of Restoration.

Antecedent bedrock control on the sediment-starved continental shelf of south/central Namibia

The Namibian inner continental shelf immediately north of the Orange River delta is sediment-poor, dominated by outcrop of metamorphic basement with a scarcity of sandy cover. Using a combination of high and very-high resolution geophysical tools and drill cores, an examination of the evolution of the inner shelf stratigraphy and geomorphology shows persistent antecedent bedrock controls throughout the Pleistocene.The bedrock of the inner shelf comprises schists, in places overlain by Eocene sandstones, over which a subaerial unconformity (H1) formed in the late Oligocene. H1 was repeatedly re-occupied during succeeding transgressive/regressive cycles, creating a backstop for erosion/sedimentation and creating a repeating topography on which transgressions took place. Apart from localised development of Miocene phosphatic limestones, little sediment has since accumulated. Large-scale karst weathering of the limestones reflects several periods of subaerial exposure most recently during the Quaternary lowstands of sea level including MIS 2 and 1.Thin Quaternary cover, housed within depressions on the H1 surface is predominantly preserved in the lee of bedrock ridges, behind which shallow and occasionally hypersaline lagoonal conditions developed. These preserved back-barrier sedimentary sequences developed post-MIS 5 (previous phases were either eroded/weathered or not deposited). Dolomite precipitation occurred when sea-level stabilised at −75 m 37,000 cal BP and restricted lagoonal conditions prevailed.Currently, there are very limited MIS 2/1 deposits preserved above H1. The absence of thick sand cover, adjacent to and downdrift of the Orange River delta, suggests that the onshore diversion of sand that currently supplies the Namib Sand Sea also operated during lower sea levels, related to the bedrock control and lack of accommodation in surface H1. This persistent onshore diversion of sediment throughout the Quaternary has implications for sediment source as well as budget calculations for the Namib Sand Sea.

ANALISIS KANDUNGAN PROTEIN DAN LEMAK PADA TERIPANG PASIR (Holothuria scabra) YANG DIPEROLEH DARI PERAIRAN DESA SULI DAN APLIKASINYA KEPADA MASYARAKAT MELALUI PENYULUHAN

Background: One kind of animals with spines are sea cucumbers. Sandy waters, rocky or muddy beaches, and coral reefs are common habitats for these species. Clear, clean waters with a fine sandy bottom, away from pounding waves, are ideal for the growth of sand sea cucumbers. Sea cucumbers are found in great number across Maluku. One such location is the waters surrounding Suli village, where sand sea cucumbers, or Holoturia scabra, are particularly common. Methods: Descriptive approaches are used in this study. The laboratory study findings served as the basis for the data sources. Results: In samples of sand sea cucumbers (Holothuria scabra), the protein yield was greater than the fat content. Conclusion: The protein content is 15.3544 and the fat content is 0.1816. This protein level figure is still below the maximum protein threshold of 72.93%.

Penguatan Kesadaran Perbaikan Lingkungan melalui Participatory Action Research Dusun Gedok Wisata B29 L

One of the interesting tourist destinations in Lumajang Regency is B29 Tourism Village in Argosari Village, Senduro District. From here, visitors can enjoy views of Mount Bromo, the highest peak in the Sand Sea area, which is located about 40 kilometers from Lumajang City and has a height of about 2900 meters above sea level. Argosari Village also has amazing natural beauty, making it an attraction for tourists. The Lumajang Regency Government has a policy that regulates the tourism sector through the cultural tourism office. Garbage is a common problem for the wider community, especially in the people of Gedok Hamlet, Argosari Village, Senduro District, Lumajang Regency. The unavailability of trash bins has led to the habit of burning garbage which can cause air pollution, and throwing garbage in vacant land or ravines which can cause environmental damage. This service focuses on the waste problems that occur in Gedok Hamlet, to reduce littering we provide several trash cans that can be useful for Gedok Hamlet residents to dispose of waste in its place. This service uses the PAR (Participatory Action Research) method, which involves community participation through interviews and observations of the community around Gedok Hamlet as a data source. This service aims to provide benefits and good impacts on waste problems that occur both in Gedok Hamlet and in the wider community, so that they understand the impact of waste on the environment and health.

Morphometry of the Samalayuca dunes, northern Chihuahua, Mexico

The Samalayuca Dunes (SMD) (Médanos de Samalayuca), Chihuahua, México, are one of México’s largest and least studied dune fields, now managed as a Protected Area for their ecological characteristics. We present a morphometric characterization of the dune field based on remote sensing and field studies, to advance understanding of its physical environment. SMD’s generally-fine sands originate from shoreline deposits of Paleolake Palomas, transported eastward (downwind) along an aeolian corridor, accumulating primarily as echo dunes upwind of the sierras of Samalayuca and Presidio. A complex wind regime, with northerly and southerly winds complementing regionally-prevailing southwesterlies, modified by topographic effects, shapes the SMD’s morphology. The sand sea covers ~139.7 km2, with ~113.8 km2 in the main eastern body and ~25.9 km2 in a northwestern subfield. We describe six major dune forms: north to south straight-crested dunes, east to west straight-crested dunes, star dunes, vegetated parabolic dunes, relict transverse dunes, and “megastar” (draa) dunes. Mean interdune centroid spacing is 76.5 m. The active dunes, previously described as an “aklé” pattern, are predominantly straight-crested dune sets oriented near-perpendicular to each other with general north-south and east-west crest orientations, 4-5 m high, spaced ~67 m apart for north-south trending crests and ~53 m for east-west trending crests, representing a nearly perpendicular interference pattern in some locations. The active dunes are superimposed in a compound and complex arrangement on relict remnants of much larger north-northwest trending transverse dune ridges fanning out from south to north-northwest, spaced approximately ~1 km apart and ~50 m high. The easternmost dune ridge contains an active set of at least 15 active megastar and reversing dunes up to 120 m tall, increasing in size and complexity from south to north. As a protected area with historical and ecological value, additional geologic investigations should be performed at the SMD, to help conserve this remarkable geologic feature.

Modern periglacial eolian deposits and landforms in the Søndre Strømfjord area, West Greenland and their palaeoenvironmental implications

Modern fluvio glacial sediments in two east-west oriented valleys between Søndre Strømfjord Air Base and the Inland Ice (West Greenland) are partly redeposited by eolian activity. Topographic barriers have induced an areal distinction between sandy and silty eolian sediments. Morphological and sedimentological investigations enable a facies analysis of these rare, active cold-climate eolian deposits and a comparison with the extensive Pleistocene sand sheets and loess deposits of Europe.
 Eolian processes are active throughout the year in a dry cold-climate environment. Accumulation of eolian material on the eolian sand sheets and silt covers mainly takes place in summer, whereas deflation and redeposition is dominant in winter. Meteorological conditions (especially thickness of snow cover) may prevent eolian activity.
 The vegetation on the sand sheets adapts itself to the intensity of the eolian activity. Vegetation is scarce in the low areas near the active flood plains where deflation is intensive, whereas the downwind depositional areas are more densely vegetated. Only a few species play an active role in the formation of small phytogenic dunes, which are characterized by a low preservation potential. Similar conditions are envisaged for the extensive Pleistocene sand seas of northwestern Europe.
 A characteristic sedimentary sequence occurs in downwind, upslope direction. Fluvio-eolian deposits on and near the active flood plain are characterized by horizontally bedded eolian sand interbedded with fluvial deposits. The latter are partly winnowed by eolian activity leading to inversely graded lamination. Horizontal bedding of fine-medium grained sand interbedded with thin coarse-grained strata is the proximal facies of cold-climate eolian sand sheets. Within-bed structures are dominated by plane bed lamination. A more homogeneous (fine-medium grained) horizontally bedded sediment, comparable to that dominating in the extensive Pleistocene sand sheets, represents the distal facies of these sand sheets.
 The uplands are covered by eolian silt deposits. These are coarser than 'typical' loess and lack other loess characteristics. This is explained by the local source area and the short transport distance. These 'proximal loess' deposits are mainly deposited on the windward side of the valley walls due to blocking of dust-laden airflows by these topographic barriers. The primary micro-lamination in these deposits may also have been present in the Pleistocene loess deposits.

Seasonal morphological evolution and migration of granule ripples in the Sanlongsha Dune Field, northern Kumtagh Sand Sea, China

Granule ripples are aeolian landforms that are armored against erosion by coarse grains at their crest. Their bimodal grain-size distributions and large dimensions distinguish them from normal wind ripples. The morphodynamics of granule ripples have attracted considerable attention because they provide a good example of coarse-grained aeolian bedforms. Previous studies have mainly focused on the morphological characteristics and formation process of granule ripples, but their evolution has been less studied. Using unpiloted aerial vehicle photogrammetry and real-time kinematic positioning, we conducted five field observations in the Sanlongsha Dune Field of northern China's Kumtagh Sand Sea. We analyzed the seasonal morphological evolution and migration of granule ripples, and the corresponding wind regimes. The morphometric parameters and migration rate showed distinctly different changes in different periods. The lowest height, the fastest migration, and most of the disintegration of granule ripples occurred in the season with the strongest wind. Although the proportions of wind speeds that exceeded the impact and fluid threshold velocities of coarse grains were low, these wind events significantly influenced the morphodynamics of granule ripples. Our findings and theoretical analysis demonstrate that the evolution of granule ripples is closely related to bimodal and unimodal transport events. To enhance our understanding of the morphodynamics of granule ripples, we must focus future research on the reptation and saltation of coarse grains.

Penguatan Kesadaran Perbaikan Lingkungan melalui Participatory Action Research Dusun Gedok Wisata B29

One of the interesting tourist destinations in Lumajang Regency is B29 Tourism Village in Argosari Village, Senduro District. From here, visitors can enjoy views of Mount Bromo, the highest peak in the Sand Sea area, which is located about 40 kilometers from Lumajang City and has a height of about 2900 meters above sea level. Argosari Village also has amazing natural beauty, making it an attraction for tourists. The Lumajang Regency Government has a policy that regulates the tourism sector through the cultural tourism office. Garbage is a common problem for the wider community, especially in the people of Gedok Hamlet, Argosari Village, Senduro District, Lumajang Regency. The unavailability of trash bins has led to the habit of burning garbage which can cause air pollution, and throwing garbage in vacant land or ravines which can cause environmental damage. This service focuses on the waste problems that occur in Gedok Hamlet, to reduce littering we provide several trash cans that can be useful for Gedok Hamlet residents to dispose of waste in its place. This service uses the PAR (Participatory Action Research) method, which involves community participation through interviews and observations of the community around Gedok Hamlet as a data source. This service aims to provide benefits and good impacts on waste problems that occur both in Gedok Hamlet and in the wider community, so that they understand the impact of waste on the environment and health.

Islands in a sea of sand: The role of Tarim Basin polities in global trade during late antiquity

AbstractMuch of the literature on the Ancient Silk Road has examined its operation through the prism of empires and East-West connections. Yet in the last few decades several scholars have sought to re-examine this framework, with a number suggesting that the roots of the Silk Road exchange network should be sought instead in the many polities which lay along its routes. This article similarly seeks to challenge the traditional ‘Silk Road of Empires’ concept by applying approaches from global history and examining both archaeological and written sources from the third- and fourth-century kingdom of Kroraina in the south-eastern Tarim Basin in Xinjiang, Western China. The first goal of this article is to consider Kroraina’s inclusion in the wider Silk Roads network and how this network influenced local elite consumption. The second is to examine Kroraina’s role in the Silk Road network. It is argued that polities like Kroraina played a crucial role in facilitating and maintaining trans-Eurasian trade in Late Antiquity.

Real-Time Kinematic Positioning (RTK) for Monitoring of Barchan Dune Migration in the Sanlongsha Dune Field, the Northern Kumtagh Sand Sea, China

Dune migration is one of the main processes in arid lands’ geomorphology and is important for the design of windbreaks and sand fixation projects and for the monitoring of desertification dynamics. We conducted long-term continuous positioning monitoring of barchan dunes using RTK equipment and wind regime monitoring in the Sanlongsha dune field, which is located in the northern part of China’s Kumtagh Desert. We analyzed the wind energy environment of the study area, the migration characteristics of different positions in the barchan dune, and dune shape changes during different periods. We found that (1) comparing the differences in migration distance and direction measured at six positions in the barchan, there existed variations in barchan migration across these positions. (2) The shape changes at the left horn, right horn, and windward slope of barchans were larger than at the center of the leeward toe and brink, so the estimates based on measurements at these four positions had a weaker fit with the resultant drift potential (RDP) and a greater difference from the resultant drift direction (RDD). (3) The shape of the leeward slope on the barchan did not change much during dune migration, so the center of the leeward toe and brink measurements were closer to the actual dune migration distance and direction. Thus, we recommend using the center of the leeward toe or brink as the optimal measurement points to monitor barchan dune migration. This study will provide a reference for the more accurate measurement of barchan dune migration.

Using Texture Statistics to Identify and Map Different Dune Types within the Rub’ al Khali

Understanding the movement, direction, and shape of sand dunes can contribute to reducing their impact on infrastructure and the environment. The Rub’ al Khali desert has a distribution of dune types. This study aims to identify and map the different types of dunes within the Rub’ al Khali using a texture analysis method based on a digital elevation model (DEM). Statistical texture analysis methods (variance, skewness, and kurtosis) show three different textures of sand dune shapes, according to the geography of the dunes, using data contained in global DEMs. The analysis presented in this study focused on the use of DEMs to investigate the varied dune morphology within the Rub’ al Khali. The GMTED2010 and EarthEnv_DEM90 digital elevation models were compared. Spatial variability in dune height, spatial variability in dune texture, and profile graphs were created to examine dune surfaces in cross-section. The results provided six different dune types within the sand sea: giant compound linear dunes, simple linear dunes, simple transverse dunes, compound crescentic dunes (megabarchans), huge star dunes, and many transitional forms that defy classification. The results showed that the compound linear dune and simple linear dune were the dominant dune types, covering 41.61% and 31.7% of the total study area, respectively. The maps of variance, using either 10 × 10 and 30 × 30 focal blocks, produced a fairly sharp distinction in dune texture. It is hoped that future research in aeolian geomorphology will greatly benefit from these results, which could easily be expanded with the use of more sophisticated pattern recognition software, which clearly shows the value of using such an approach.

Source supply processes of the megadune field in the Badain Jaran Sand Sea

Source supply processes of the megadune field in the Badain Jaran Sand Sea

Antioxidant and antibacterial activity test on a crude extract of sand (Holothuria atra) in Lemukutan water, Bengkayang District

Sea cucumbers are soft-bodied marine invertebrates from the Holothuroidea class whose habitat is in sandy areas. This study aims to determine the content of secondary metabolites in crude extracts of sea cucumber which have the potential as antioxidants and antibacterials. The type of sea cucumber used in this research is the sand sea cucumber (Holothuria atra). The research was carried out from October 2020-February 2021. Samples were taken using the exploratory method, the sea cucumber samples were processed with 5 treatments, namely cleaning and crushing sea cucumber samples, extraction using the maceration method, evaporation with a vacuum rotary evaporator, and drying using freeze-drying. The bioactive components found in sea cucumbers are alkaloids, flavonoids, saponins, and phenols. The antioxidant activity found in sea cucumbers has an IC50 1194 ppm which is classified as a weak antioxidant. The antibacterial activity found intraday sand sea cucumbers E. coli gave the highest inhibition zone at a concentration of 20% with an inhibition zone diameter of 20.08 mm while S. aureus gave the highest inhibition zone at a concentration of 30% with an inhibition zone diameter of 22.17 mm.