Taxonomy and Distribution of the Deep-Sea Batfish Genus Halieutopsis (Teleostei: Ogcocephalidae), with Descriptions of Five New Species

The deep-sea batfish genus Halieutopsis is reviewed based on worldwide collections. Sixteen species are recognized, including five newly described species: Halieutopsis echinoderma sp. nov. from eastern Taiwan and northeastern Australia, Halieutopsis kawaii sp. nov. from Taiwan and Indonesia, Halieutopsis okamurai sp. nov. from southeastern Japan, Halieutopsis murrayi sp. nov. from the Gulf of Aden, and Halieutopsis taiwanea sp. nov. from northeastern Taiwan. These species differ from their congeners in escal morphology, squamation, and morphometric proportions. Dibranchus nasutus Alcock, 1891, a senior synonym of Halieutopsis vermicularis Smith & Radcliffe, 1912, as well as Dibranchus nudiventer Lloyd, 1909 and Coelophrys oblonga Smith & Radcliffe, 1912, are recognized as valid species in Halieutopsis. Comments on the systematics and biogeographic distributions of the species of Halieutopsis are provided, along with a key to the species.

Revealing 60 years of Earthquake Swarms in the Southern Red Sea, Afar and the Gulf of Aden

Earthquake swarms occur sporadically at divergent plate boundaries but their recurrence over multiple decades and relation to magmatic spreading activity remain poorly understood. Here we study more than 100 earthquake swarms over a 60-year period in the southern Red Sea, Afar, and Gulf of Aden region. We first compiled an earthquake-swarm catalogue by integrating reexamined global and local earthquake catalogues from 1960 to 2017. This yielded 134 earthquake swarms that mainly cluster in 19 different areas in the study region, showing that in most cases swarms recur every few decades in the same area. The swarms exhibit a range of earthquake magnitudes and often include multiple M3 to M5 events with some swarms having occasional larger earthquakes over M6, primarily in southern Afar. Many of the earthquake swarms were clearly associated with rifting events, consisting of magmatic intrusions, surface faulting, and in some cases volcanic eruptions. Together, the swarms suggest that extension at these divergent plate boundaries occurs episodically along <100 km long segments, some of which were previously unrecognized. Within the study region, the Gulf of Aden shows the most frequent swarm activity, followed by Afar and then the southern Red Sea. The results show that the three areas were subject to an increase of earthquake-swarm activity from 2003 to 2013 in the form of three rifting episodes and at least seven volcanic eruptions. We interpret that the most likely controls on temporal variations in earthquake swarm activity are either temporal variations in magma supply, or rifting-induced stress change that trigger clusters of swarms.

Margin-to-Margin Seafloor Spreading in the Eastern Gulf of Aden: A 16 Ma-Long History of Deformation and Magmatism from Seismic Reflection, Gravity and Magnetic Data

In this paper we present and analyze spreading-parallel seismic transects that image the oceanic crust in the eastern Gulf of Aden, from the Oman to the Socotra margins, across the active Sheba mid-oceanic ridge and between the Socotra-Hadbeen and Eastern Gulf of Aden Fracture Zones. The correlation of potential field data sets and gravity modelling allow us to document the spreading history of this oceanic basin from the onset of seafloor spreading ∼16 Ma-ago to the present. Two main oceanic sub-domains display distinct structural characteristics associated with different magmatic budgets at this mid-ocean ridge. In addition, we document the occurrence of a magmatic pulse at the Sheba Ridge around 11 Ma leading to the construction of a magmatic plateau in the western part of the studied area. This event led to substantial deformation and additional magmatism in previously formed oceanic crust. It could be related to an off-axis magmatic event previously identified in the adjacent Sheba segment, itself possibly related to the Afar plume.

Seismicity in Yemen and the Gulf of Aden in a geological context.

The study presents geologic investigation of Yemen and the Gulf of Aden with a special focus on geophysical, seismic, tectonic and topographic mapping performed by the integrated approach of QGIS and GMT scripting. Cartographic visualization is crucial in geologic analysis, data processing and prognosis of mineral resource prospects. The region of Yemen and Gulf of Aden was formed as a result of Arabian and African plates movements and still tectonically active. Besides, the Gulf of Aden contains mineral resources of hydrocarbons which makes this region actual for investigation. The IRIS database on earthquakes was used for visualization of the magnitude of submarine earthquakes in the Gulf of Aden for the period of 2007-2020. The paper presents 6 new thematic maps for the region of Yemen and Gulf of Aden. The research presented an analysis of correlation between the geological, topographic and geophysical settings. Through combined approach of cartographic high-resolution data visualization and geologic analysis, this paper contributed to the regional geological studies of Yemen, Gulf of Aden and the Middle East.