Southern End Research Articles

Yoḥannәs Mäțmәq (Saint-Jean Baptiste) de Gazen (Tәgray) : l’église et son baptistère. Nouvelles hypothèses

Dedicated to the rock-hewn church of John the Baptist (Yoḥannәs Mäțmәq) of Gazen, in Eastern Tәgray, which has received little attention so far, this paper aims to specify its chronology and to shed light on its function. It is a vast three-aisled basilica, covered with ceilings, the naves being separated by pillars supporting an architrave. The sanctuary, extended by a semicircular apse, is flanked by annexes, including, at the southern end, a baptistery, which adds to the very few examples so far recorded in Ethiopia. If the precise ceremony ritual procedures escape us, we can at least reconstruct the dynamics of circulation of baptismal candidates. The architecture of the church has many points in common with the basilicas of the Aksumite period, but also, more broadly, with the early Christian churches of the Eastern Mediterranean, which leads us to suggest a 6th century or early 7th century dating ; this hypothesis is not contradicted by the evidence recently brought by archaeology for this region. Furthermore, this chronology, if accepted, could invite reconsideration of that of other rock-cut churches (Dәgum Sәellase, Bäraqit Maryam, Ḥawzen Täklä Haymanot). Easily accessible, of imposing dimensions, with benches along the walls and endowed with a baptistery, the church of Yoḥannәs Mäțmәq was intended to accommodate a large number of faithful. Its use was not limited to a funeral function, hitherto privileged in scholarship ; the hypothesis of a pilgrimage center, where baptism could be carried out, can be considered. Finally, the church of Gazen, whose commissioners are unknown, but which testifies to a substantial investment, may have played a role in the Christianization process of the rural populations of Eastern Tәgray.

Tectonics and Sulphide Mineralization in the Boundiali Birimian Formations by Means of Geophysical Data

This study focused on the interpretation of geophysical data collected from the Sissedougou prospect which is located at the southern end of the Korhogo-M’Benguebirimian trench. The geophysical surveys were carried out on two grids with two magnetometers and an induced polarisation unit composed of a transmitter and a receiver. The magnetic data allowed on one side the mapping of basic, intrusive and volcanic formations, weakly magnetic rocks produced by meta-sediments to be showed, and on the other hand to identify the continuity of the shear corridor observed southward and northward of the prospect. Induced polarisation data revealed the signature of sulphide and disseminated mineralization. The synthesis of the obtained results showed that deep NE-SW, NNE-SSW and N-S oriented fractures promoted the late rise of sulphide fluids. The setting of sulphide and gold mineralization in the southern part of the Boundiali trench is therefore controlled by ductile and brittle shearing.

Fault Controlled Geometries by Inherited Tectonic Texture at the Southern End of the East African Rift System in the Makgadikgadi Pans, Northeastern Botswana

Fault Controlled Geometries by Inherited Tectonic Texture at the Southern End of the East African Rift System in the Makgadikgadi Pans, Northeastern Botswana

Каменная индустрия памятника Гвоздевка i

The article covers the exploration of the stone industry of a Mesolithic site Gvozdevka I. The Stone Age man site is located in Moskalenki district of Omsk region, at the southern end of Lake Ebeyty, on the eastern bank of flood plain Amre (Amrinsky beam). It was discovered in 1976, last investigated in 2004. In the course of archaeological work, a representative collection of stone artefacts was formed, among them microplates occupying a considerable place. The manufacturing specificity of site materials is difficult for analysis, but certain aspects of plate production and utilisation can be taken into consideration. The techno-typological method, as part of attributive approach, was used for their analysis. The description and analysis of the stone industry was made according to the parameters characterising the metric indicators of cleavage, cleavage zone and dorsal surface. The basic strategy of stone cleavage is reconstructed, aimed to produce lamellar chipping with the use of pressure flaking technique. The production of inlay blanks - thin plates with straight lateral profile and sharp longitudinal edges - appears to have been the ultimate goal of the cleavage. The quality of the analysed material enables one to study not only the techno-typological aspects of its manufacture, but also the traces of non-utilisation wear, secondary processing of blanks as well as functional wear (which is the subject of further research). This suggests that the monument was used to split pre-nuclei or nuclei brought by people; the obtained plates were actively used in the process of treatment of various materials. On the whole, using the attributive approach to the study of Gvozdevka I site stone industry made it possible to establish the major strategies of stone splitting and to reconstruct the primary splitting system, as well as to create a framework for comparison with other monuments of the same period on the territory of Omsk region and adjacent areas, to outline the prospects for further research.

Cretaceous Rift‐Drift Tectonics Then Paleogene Prearc Subsidence Related to Subduction Initiation: Aotea Basin, Zealandia, Southwest Pacific

AbstractStratal stacking patterns and termination relationships of Upper Cretaceous and Paleogene strata of Aotea Basin, which is at the southern end of New Caledonia Trough and adjacent to Taranaki Basin, are used to infer vertical movements before, during, and after Tonga‐Kermadec subduction initiation. Regional 2D seismic‐stratigraphic units are tied to petroleum exploration wells, including recently drilled Romney‐1. We identify: (a) an uppermost Cretaceous to Paleocene (70–56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea‐level falls; (b) a diachronous deepening of the basin from shelfal to bathyal environments, that progressed northwest to southeast during the early to middle Eocene (53–46 Ma); (c) that was contemporaneous with small‐scale volcanism; (d) a brief phase of middle to late Eocene (46–35 Ma) delta development at the western basin margin (Challenger Plateau) that is evidence for local uplift; and (e) an onlapping sequence deposited since the latest Eocene (35–0 Ma) that requires ∼1,300 m of subsidence at the western margin. Paleogeographic maps and a generalized stratigraphic chart summarize our observations. The Eocene phase of tectonic subsidence, uplift, and diffuse volcanism (53–46 Ma) was a precursor to plate motion at the Cenozoic plate boundary through New Zealand and suggests a causal relationship between prearc subsidence, Tonga‐Kermadec subduction initiation, and plate motion change. Delamination of lower crust beneath Aotea Basin during initial subducted slab formation might explain our observations.

Polygamous Family Life and Geographic Isolation: The Poetry of Esther Ann Birch Bennion

Polygamous Family Life and Geographic Isolation: The Poetry of Esther Ann Birch Bennion

Volcanic tremor associated with the Surtsey eruption of 1963–1967

The formation of the island of Surtsey over 3.5 years, remains one of the best-documented volcanic, island-forming eruptions to date. The basaltic submarine volcanic activity was detected on November 14, 1963, where ocean depth was 130 m prior to the eruption at the southern end of the Vestmannaeyjar archipelago. The eruptions occurred in several phases involving explosive and effusive activity, including the initial submarine phase on November 12–13, 1963. Separate phases of subaerial volcanic activity occurred during November 14, 1963–January 1964, January–April 1964, April 1964–May 1965, May–October 1965, December 1965–August 1966, and August 1966–June 1967. Seismic data quality from this period is inferior compared to that of modern monitoring systems. Four permanent seismic stations were operated in Iceland at the time, whereof only two, located at 115 and 140 km distance, had the sensitivity to record tremor from Surtsey. Nevertheless, the scanned analog seismograms (http://seismis.hi.is/) show that the eruptive activity was accompanied by considerable seismic activity, both earthquakes, and volcanic tremor. Earthquakes were primarily associated with changes in vent location. Both spasmodic and harmonic tremor was identified, both with low (<3 Hz) and higher (3–5 Hz) characteristic frequencies. The results indicate a complicated relationship between tremor and magma flow rate or style of activity. During the explosive eruption, the highest magma flow rates occurred in the first 10–20 days, a period with little observed tremor. The highest tremor is observed in December 1963–March 1964, after the discharge rates had dropped substantially, and on a timescale of hours-to-days, no clear relationship between tremor and eruption style is observed. The same applies to the effusive activity, where no seismic tremor was observed during most of the effusive eruption of Surtungur, despite the fact that magma flow rates were ~3 times higher than during later phases where some tremor was observed. Keywords: Submarine volcanism, eruption precursors, volcanic tremor, precursory tremor, continuous uprush eruptions

An assessment of the groundwater potentials of the farm with preliminary geophysical method and grain size analysis prior to the drilling of boreholes

The study of groundwater potentials of the Owutu-Ogbu area, Southeastern Nigeria, has been carried out to delineate its availability of water. A geological study revealed that two main rock types, sandstone and shale, characterize the study area. The shale does not yield enough water, while the sandy area is the water-bearing zone. The sandstone outcrop trends N 55°E, dipping 160°SE with a dip of 60°, which facilitates the downward water motion by gravity. The presence of highly fractured and jointed sandstone is another attribute of the porous Afikpo sandstone in the Owutu-Amaigbo area. All the sample sizes are moderately sorted and moderately well sorted, with the exception of the sample at 120 ft. that is poorly sorted. At 90 ft., the sample is strongly positively skewed at 30 ft., 120 ft., 180 ft., and at the surface. At 60 ft., 150 ft., and 210 ft., they are nearly symmetrical. The samples are very coarse sand, except at 30 ft. and 210 ft. From the VES data, the aquifers were delineated between layers 3 and 4, ranging in depth from 50 to 60 m. Proper grain size analysis and VES interpretation show that a feasible borehole can be drilled at the southern end of the N 55°E trending sandy ridge.

Genetic Diversity, Structure, and Selective Sweeps in Spinacia turkestanica Associated With the Domestication of Cultivated Spinach.

Genotype-by-sequencing (GBS) was used to explore the genetic diversity and structure of Spinacia turkestanica, and the selective sweeps involved in domestication of cultivated spinach, S. oleracea, from S. turkestanica. A total 7,065 single nucleotide polymorphisms (SNPs) generated for 16 Spinacia oleracea and 76 S. turkestanica accessions placed the S. oleracea accessions in one group, Q1, and the 76 S. turkestanica accessions, which originated from Central Asia, in two distinct groups, Q2 and Q3. The Q2 group shared greater genetic identity with the S. oleracea accessions, Q1, than the Q3 S. turkestanica group. Likewise, the S. oleracea Q1 group had a smaller Fst (0.008) with the Q2 group than with the Q3 group (Fst = 0.012), and a greater gene flow (Nm = 30.13) with the Q2 group than with the Q3 group (Nm = 21.83). The Q2 accessions originated primarily from Uzbekistan while the Q3 accessions originated mostly from Tajikistan. The Zarafshan Mountain Range appears to have served as a physical barrier that largely separated members of the Q2 and Q3 groups of S. turkestanica. Accessions with admixtures of Q2 and Q3 were collected primarily from lower elevations at the southern end of the Zarafshan Mountain Range in Uzbekistan. Selective sweep regions identified at 32, 49, and 52 Mb on chromosomes 1, 2, and 3, respectively, appear to have played a vital role in the domestication of S. oleracea as they are correlated with important domestication traits, including day length sensitivity for bolting (flowering). High XP-CLR scores at the 52 Mb genomic region of chromosome three suggest that a selective sweep at this region was responsible for early differentiation of S. turkestanica into two groups in Central Asia.

Macrobenthic Mollusca of the Prince Gustav Channel, Eastern Antarctic Peninsula: An Area Undergoing Colonisation

In 2018 RRSJames Clark Rossinvestigated the marine benthic biodiversity of the Prince Gustav Channel area which separates the eastern coast of the Antarctic Peninsula from James Ross Island. The southern end of this channel had been covered by the Prince Gustav Ice Shelf until its collapse in 1995. Benthic samples were collected by an epibenthic sledge at six stations (200–1,200 m depth) in the channel and adjacent Duse Bay. In total 20,307 live collected mollusc specimens belonging to 50 species and 4 classes (Solenogastres, Bivalvia, Gastropoda, and Scaphopoda) were identified. The area may be characterised by it’s low species richness (ranging from 7 to 39 species per station) but high abundances (specifically of the Scaphopods with 11,331 specimens). The functional traits of the community were dominated by motile development and mobility type. Assemblage analyses of the molluscan species abundances within the Prince Gustav Channel stations sit distinct, with no pattern by depth or location. However, when bivalve assemblages were analysed with reference to the wider Weddell Gyre region (15 stations from 300 to 2,000 m depth), the Prince Gustav Channel sits distinct from the other Weddell Gyre stations with a higher dissimilarity between the deeper or more geographically distant areas. The Prince Gustav Channel is undergoing colonisation following the recent ice shelf collapse. With many Antarctic ice shelves threatened under climate warming, this area, with future monitoring, may serve as a case study of benthic faunal succession.

Conceptual contours of migration studies in and from Asia

Conceptual contours of migration studies in and from Asia

Sounds of Silence

It was the early 1980s on a warm summer’s evening on North West Island, located in the Capricornia Bunker Group towards the southern end of the Great Barrier Reef. I had some time to myself and was wandering along the beach at sunset. Looking up, I realised there were thousands and thousands, if not hundreds of thousands, of birds — wedge-tailed shearwaters, in fact — circling the island as they returned to their underground nests and their mates and chicks after a day of feeding and cruising the air currents. What was so special about this? After all, it happens every summer’s evening on many Reef sand cays. It was special for me because I suddenly realised that this huge sweep of birds was flying past in total silence … the only sound was an occasional wing dipping into the sea.

How gathering wild rice under human-mediated drought stress could have inadvertently paved the way to Asian rice incipient domestication and cultivation

In eastern China, on the southern end of the Yangtze Valley, early Holocene hunter-gatherers were foraging various plants, including wild rice – Oryza rufipogon Griff. – an aquatic and perennial plant which is the wild progenitor of domesticated rice. According to optimal foraging theory, these foragers should have tried to enhance the efficiency of harvesting wild rice seeds by draining water around the plants before seeds ripened and shattered. This proto-cultivation practice led to unintended consequences given that wild rice responds to drought stress owing to its phenotypic plasticity. Plant and panicle architectures were modified with transitions to more compact and erect tillers and to a closed panicle shape. They provide incentives to early foragers for intensifying their proto-cultivation practices and so could have also triggered initial cultivation of rice. They also triggered incipient domestication of rice, starting by the transition to selfing. According to this narrative, it is even possible that rice incipient domestication preceded cultivation.

Larval lake whitefish distribution in the open waters of Green Bay, Lake Michigan

Most lake whitefish populations within Lake Michigan are experiencing widespread population declines due to low levels of recruitment. However, the stock within Green Bay is flourishing, and various assessment tools suggest consistent recruitment to the juvenile stage each year. The distribution of offshore and drifting lake whitefish larvae were last described in the 1970s, prior to the resurgence of the southern Green Bay stock and prior to increasing knowledge of adult spawning behavior. We conducted a Green Bay wide survey of lake whitefish larvae over three years to provide an update of larval abundance and distribution and to discern influential biotic and abiotic factors that correlate to larval densities. In contrast with historical studies, our sampling illustrated high densities of larvae in both offshore and nearshore environments. Offshore expansion may be a factor in the population increase, but long term survival effects are still unknown. This study also provides the first documentation of larvae within the southern end of the bay below Chambers Island, WI and near re-colonized rivers. Average overall densities were relatively consistent each year, ranging between 29.5 and 49.6 per 1000 m3. Lake whitefish larvae were patchy in distribution and were associated with warmer and more productive waters at small spatial scales. Larval lake whitefish appear to be distributed widely throughout the entirety of Green Bay during the drift life stage, and we discuss our results in light of re-established river spawning and the overall increase in abundance.

A tidally driven fjord-like strait close to an amphidromic region

Abstract. The strait studied in this paper, “Sundalagið Norður”, is the northern part of a narrow body of seawater separating the two largest islands in the Faroe Islands (Faroes). It has shallow sills in both ends and considerably deeper waters in between. South of the southern end of the strait there is an amphidromic region for the semidiurnal tides so that the tidal range is much lower south of the strait than north of it. The resulting tidal forcing generates periodically varying inflow of seawater across the northern sill, but only a part of that manages to cross the narrow and shallow southern sill. Combined with a large input of freshwater, this gives the strait a fjord-like character. To investigate how this fjord-like character affects the circulation within the strait and its exchanges with outside waters, a pilot project was initiated to simulate the dynamics of the strait with a high-resolution ocean model for a month. The model simulations show clearly the dominance of tidal forcing over freshwater (estuarine) and wind on timescales up to a day. On longer timescales, the simulations indicate systematic variations in the net flows (averaged over a diurnal tidal period) through both the upper and deeper layers. These long-period variations of net flow in the model simulations are forced by sea level differences between both ends of the strait generated by the dominant fortnightly and monthly tidal constituents (Mf, MSf, Mm, MSm). Harmonic analysis of sea level records from two tide gauges located off each end of the strait demonstrates that this behaviour is not a model artefact and it has pronounced effects on the strait. Not only does it induce long-period (mainly fortnightly) variations in the net flow through the strait, but it also generates variations in the estuarine characteristics. According to the model simulations, periods with net southward flow, typically lasting a week, have a strait-like character with net southward flow almost everywhere. Periods with net northward flow, in contrast, have a more fjord-like character with stronger salinity stratification and a southward counter-flow in the deep layer. This also induces a large difference in renewal rate of the deep water between the two periods, which is important to consider for human utilization of the strait, especially the local aquaculture plant. The combination of topographic, freshwater, and tidal characteristics creating these long-period variations is rather unusual, and it is not known whether similar systems exist elsewhere, but the long-period variations tend to be masked by the stronger semidiurnal and diurnal variations and may easily be overlooked.

MODELING THE DISTRIBUTION OF THE SOUTHERN YELLOW-CHEEKED GIBBON (NOMASCUS GABRIELLAE) USING MAXENT

The Southern Yellow-cheeked Gibbon (Nomascus gabriellae) is an endangered species found only in a small region of Indochina, and its populations have declined in most known sites. In this study, we use Maxent, a robust and widely used species distribution modeling approach, to predict the current and future distributions of the Southern Yellow-cheeked Gibbon over its entire range based on an extensive review of published records. In total, we compile and provide a comprehensive set of known distribution records of the species from Cambodia, Laos, and Vietnam. The model results show that N. gabriellae potentially occurs in much of area around the Central Highlands in both Vietnam and Cambodia sides and the southern end of Laos. Our study suggests that protected areas in this region will play a key role in conservation actions for the gibbons. In addition, the distribution of the gibbon in future climate conditions, even in the best-case scenario, is likely to shrink significantly, as the species would have to move upwards to higher elevations. Under such impact, the populations will become more fragmented and restricted to a few areas with higher elevations. Our study also confirms that the climatic difference in distribution ranges may not be fully responsible for the speciation and biogeography of the N. annamensis/gabriellae complex.

Migration-Based Local Event-Location Workflow for Ocean-Bottom Seismometer (OBS) Records in Subduction Zones: A Practical Approach for Addressing a Large Number of Events

ABSTRACT An efficient event-location workflow is highly desired to analyze large numbers of local earthquakes recorded by ocean-bottom seismometers (OBSs) in subduction zones. The present study proposes a migration-based event-location approach for evaluating OBS records to examine local subduction-zone earthquakes. This approach can significantly reduce the amount of manual time picks compared with conventional methods. The event-location workflow was designed to detect arrival onsets of both P and S phases. Synthetic tests have shown that the proposed migration-based event-location method is robust against different types of noise, such as environmental noise and local spike noise. This workflow was then applied to real OBS data in the off-Ibaraki region at the southern end of the Japan trench. The results show that this approach is applicable to real data from subduction-zone events: It gives reasonable agreement with manual time picks for both P and S waves and reasonable error bars, and it demonstrates a clear down-dip trend of seismicity. The results also show fair agreement with event distributions from previous studies of the off-Ibaraki region. This proposed workflow can be used to examine the seismicity of local earthquakes around the subduction zone using OBSs. This approach is especially effective when the seismicity is high and/or in cases in which long-term OBS monitoring has recorded a large number of events.

Compared structure and evolution of the conjugate Demerara and Guinea transform marginal plateaus

The Demerara and Guinea plateaus are conjugate Transform Marginal Plateaus (TMPs) formed at the junction of the Jurassic Central Atlantic Ocean and the Cretaceous Equatorial Atlantic Ocean. We compare their structure and evolution through a combined industrial/academic seismic dataset tied by well data. We show that these TMPs record a complete evolution history from the Jurassic Central Atlantic to the Equatorial Atlantic breakup and seafloor spreading phases. Both plateaus first formed as volcanic margins displaying successive SDR wedges migrating towards the newly forming Central Atlantic domain. In this context, Demerara and Guinea, conjugates of the Bahamas, seem to have formed in relation to plume activity at the southern end of the Central Atlantic domain. Our dataset suggests that the Demerara and Guinea plateaus initially represented two distinct extrusive centres separated by a crustal basement high. Later, during the Cretaceous Equatorial opening phase, both plateaus separated in a transform mode following this discontinuity. Deformation is notably asymmetric during this phase: Aptian to Albian folding, strike-slip, transtensive deformation and complex vertical movements on the Demerara side and only minor deformation on the Guinean side, except on its divergent Sierra Leone termination. The deformation is sealed on both plateaus by a regional upper Albian erosion unconformity. Extensional reactivation occurs on the Guinea side (probably through a general collapse?). To conclude, this study provides new insights into the nature and origin of TMPs and the key tectono-sedimentary archives they may contain to understand the polyphase breakup conditions of Gondwana.

Environmental Considerations for the Management of the Bivalve Fisheries of Bahía Magdalena (Mexico), a Coastal Lagoon at the Southern End of the California Current

This study presents an overview of bivalve assemblages in Bahia Magdalena (BM, México) and the possible impact of environmental variability on these populations, constantly stressed by fishing. This lagoon is responsible for a high proportion of harvest of regional bivalves. First, we list the bivalve species reported in public biogeographic databases. Based on eight commercially exploited species, we described the composition of the bivalve assemblage and its biological characteristics, the history of fishery, and environmental variability in the marine area adjacent to the lagoon (1970–2019) and the habitat of bivalves (2002–2020). Sources of data were public databases and published literature. The enlisted species (n = 184) belong to six orders, and most are small and infaunal, but the structure of the assemblage is unknown. The fisheries began at different times and focused on the most valuable resources. Almost all harvest of bivalves had wide variations because of intensive fishing and a weak regulation frame. After 2015, the main resources were the Pacific wing-oyster (a new resource since 2017) and the geoduck clam due to the declining abundance of other resources (e.g., pen shells, Pacific calico scallop). There was a warming trend in the region since the 1970's, but the strongest El Niño-Southern Oscillation (ENSO) phases caused the most notable changes before 2013; after that year, a combination of large-scale phenomena increased the temperature significantly. The trend of chlorophyll-a abundance negatively correlated with temperature, but there was an almost constant supply of particulate organic matter in the interior of Bahia Magdalena (BM). After 2015, the quality of lagoon water gradually deteriorated, and in 2017 and 2019, harmful algal blooms developed, but the impact was not fully assessed. The challenges faced by the fishery are multiple (institutional weakness and regional warming); however, permanent monitoring programs of environmental conditions and critical biological variables should be implemented to design scenarios that allow fishery sustainability.

The uppermost Cretaceous continental deposits at the southern end of Patagonia, the Chorrillo Formation case study (Austral-Magallanes Basin): Sedimentology, fossil content and regional implications

The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.