ALBERT

Description: Near Reykjavik/Iceland, a "soft stimulation” geothermal experiment was performed in the frame of the DESTRESS project in 2019. The installed seismic stations consist of short period, and borehole stations in and around Geldinganes, NE of Reykjavik. The task of this network is the monitoring of the seismic events in the area around the stimulation site. The installation started in late 2018 with 6 short period stations (Reykjavik Energy). Since July 2019 additional seismic stations were integrated as a small scale array on the island Geldinganes and additional short period stations. A borehole geophone chain was installed with 17 short period 3-component geophones with a vertical spacing of 10 meter in the depth interval 1040m to 1200 m. Waveform data are available from the GEOFON data centre, under network code YG, and are embargoed until January 2025.

Description: The Bransfield Strait is a seismically active extensional rift located between the Antarctic Peninsula and the South Shetland Islands. The Strait is partly located on continental crust including areas within the transition to seafloor spreading. The amphibious seismic network BRAVOSEIS is an international effort focused on the seismological research of submarine volcanoes and rift dynamics in the Bransfield Strait. This network is the onshore component of the entire network consisting of 15 broadband land stations deployed in the South Shetland Islands and Antarctic Peninsula between January 2018 and February 2020. The offshore components (network code ZX) include 9 broadband ocean bottom seismometers (OBS) across the Central Bransfield Basin and a group of 6 hydrophone moorings spanning the rift area of 200 x 100 km2, with inter-station distance of ~30 km. Additionally, a smaller offshore array consisting of 15 short-period OBSs with an aperture of 20 km and a narrow inter-station distance of ~4 km was deployed around the Orca submarine volcanic edifice south of King George Island. The data will be used to study the geodynamics of the Bransfield Strait and the evolution of the incipient rifting zone in the domain where extension has been suggested. Seismological methods will include earthquake location, source mechanism, surface wave analysis with ambient noise and earthquake data, receiver function and shear wave splitting. The results may shed light on the crustal structure and tectonic regime in the region and image the location and extent of magma accumulations related to submarine volcanic structures. Finally, the results should provide clues to assess the internal processes that occur in the submarine volcanoes of the area undergoing rifting. Waveform data are available from the GEOFON data centre, under network code 5M and are embargoed until Mar 2024. Acknowledgments: We thank all participants in the BRAVOSEIS 2018, 2019, and 2020 cruises, with a special acknowledgement to Capt. Jose Emilio Regodon and his crew at R/V Hesperides; Capt. Juan Carlos Hernandez and his crew at Sarmiento de Gamboa; Miki Ojeda, Ezequiel Gonzalez, and all the UTM staff involved in the planification and realization of the surveys. We also thank the Spanish Polar Committee and institutions involved in the management of the Spanish Antarctic campaigns and the development of the Spanish Polar Program. We are grateful for the help and support that we always find in the personnel of the Antarctic Bases, especially the Spanish Bases Juan Carlos I and Gabriel de Castilla.

Description: Oldoinyo Lengai in the North Tanzanian Divergence is the only active natrocarbonatite volcano world-wide and presents an important endmember magmatic system in a young rift segment of the East African Rift System. This volcano typically experiences long-duration episodes of natrocarbonatitic effusions with intermittent short-duration explosive eruptions. To better understand the role of the stress interactions and magma plumbing on the eruptions dynamics, this study aims to constrain the subsurface magmatic architecture of Oldoinyo Lengai, and a zone of ongoing seismicity and intrusive activity below the extinct 1 Ma-old Gelai shield volcano and active Naibor Soito monogenetic cone field. Waveform data are available from the GEOFON data centre, under network code 9J, and are embargoed until November 2025.

Description: On 26th of November 2019 an Mw 6.4 earthquake ruptured near the port town of Durres, only 25 km from Tirana, the capital of Albania. The earthquake caused major damage and killed 51 people, making it the deadliest earthquake in 2019 worldwide. The mainshock was relatively deep (~25 km) and of thrust type. In December 2019, a Hazard and Risk team (HART) from German Center for Geosciences (GFZ), Karslruhe Institute of Technology (KIT) in cooperation with the Institute of Geosciences, Energy, Water and Environment (IGEWE) of the Polytechnic University of Tirana, Albania installed a 30-station seismic network in the epicentral region to record aftershocks. Stations were equipped with short-period (1 Hz or 4.5 Hz) 3-component seismometers and CUBE data loggers recording continuously 100 sps. Waveform data are available from the GEOFON data centre, under network code 9K under CC-BY 4.0 license and are embargoed until January 2024.

Description: Proficiency testing (PT) is one of the few ways for an analytical laboratory to assess data quality under routine operating conditions. Here we report the results of Round 1 of the G-Chron PT programme, which is sponsored by the International Association of Geoanalysts. G-Chron is the first PT scheme devoted to the U-Th-Pb dating of mineral phases, primarily zircon, in geological materials. In this first round of G-Chron a total of 72 geochronology laboratories received the test material “Rak-17”, which previously had been characterized by seven well-established isotope dilution TIMS laboratories. A total of 63 of the PT participating laboratories reported data by the 15 December 2019 deadline. Here we both report and assess the measurement results submitted to this round. Our analysis provides a means for participating laboratories to assess their individual performance in relation to the isotope ages assigned, the experimental fitness-for-purpose criteria proposed by the scheme’s organisers and the results of similar laboratories participating in this round.

Description: A c. 2.4 Ga microbialite reef complex within the Turee Creek Group (TCG) in Western Australia was deposited in the aftermath of the Great Oxidation Event (GOE). The diverse reef contains the first appearance of thrombolites, a complex deep water microfossil assemblage, and the oldest shallow water sedimentary phosphorous deposit [1, 2, 3]. Silica is present throughout the reef, as microcrystalline quartz in thrombolites, fine chert preserving the deep water microfossil assemblage, and as euhedral quartz crystals within phosphorous-rich peloids and pebbles [1, 2, 3]. Petrographic examination indicates some relatively early silica phases. Si isotope analysis will be used to evaluate the effect of re-equilibration by Proterozoic sea water and pore fluids on the cherts and quartz grains within this reef, to determine whether primary information (such as sea water temperature, pH, and salinity [4, 5]) can be retained. Here we present a wide range of recorded δ30Si from -2.8 to 4.1 ‰, which is typical of Precambrian cherts [4, 5, 6]. It was recently demonstrated that low temperature re-equilibration of Si isotopes between amorphous and aqueous states readily occurs in water with high ionic strength and that is supersaturated with Si [4]. Since these units were deposited before the advent of silicifers (e.g. diatoms), the ocean would have been supersaturated with silica [4, 5]. Re-equilbration is likely to have occurred, and it is possible that some isotope values reflect the sea water, or diagenesis, rather than the process that first precipitated the silica or the source of silica. By determing how much of an effect re-equilibration has had, we can try to determine what useful, primary information is retained and what the environment was like during the GOE.

Description: IGMAS+ is a software for 3-D modelling of potential fields and its derivatives under the condition of constraining data and independent information. It comes with tools for forward and inverse modelling. IGMAS+ has a long history starting 1988 and has seen continuous improvement since then with input by many contributors.

Description: The dataset is composed of Neo HySpex (VNIR/SWIR) hyperspectral imagery acquired during airplane overflights on June 6th, 2015 covering the Omongwa Pan located in the South-West Kalahari, Namibia. The dataset includes three cloud-free flight lines with 408 spectral bands ranging from VNIR to SWIR wavelength regions (0.4-2.5 µm). The dataset also includes Level 2A EnMAP-like imagery simulated using the end-to-end Simulation tool (EeteS). The overall goal of the campaign was to acquire imagery over the Omongwa Pan and use the spectral reflectance for the analyses of surface sediments, specifically the mineralogical composition of exposed surface evaporites / salts on the airborne and spaceborne scale. The data are highly novel and can be used to test estimation of surface sediment properties in a highly saline and dynamic environment.

Description: The dataset is composed of Neo HySpex (VNIR/SWIR) hyperspectral imagery acquired during the GFZ/DIMAP Geoarchive airborne campaign on June 6th, 2015 covering the Omongwa salt pan located in the South-West Kalahari, Namibia. The dataset includes 9 merged cloud-free flight lines with 408 spectral bands ranging from VNIR to SWIR wavelength regions (0.4-2.5 μm). The dataset also includes Level 2A EnMAP-like imagery simulated using the end-to-end Simulation tool (EeteS). The overall goal of the campaign was to test the potential of advanced optical hyperspectral remote sensing, or imaging spectroscopy, for the analysis of surface processes in the Omongwa salt pan and for the quantification of surface sediments. Specifically, the mineralogical composition of exposed evaporites such as halite, gypsum and calcite were investigated at the airborne and spaceborne scale, associated with comprehensive field campaigns, ich which spectral reflectance and ground-truth chemical data of field samples have been collected. The data are highly novel and can be used as testbeds for the development and validation of retrieval algorithms based on air- and space-borne hyperspectral imagery for estimation of surface sediment properties in a highly saline and dynamic environment.

Description: Viscoelastic deformations of an earth structure in response to a time-varying surface load are analyzed in glacial isostatic adjustment (GIA). When solving this problem, aspects like flexure of the lithosphere and retarded response of mantle material become evident. Quantified are these by flexural rigidity and relaxation times. The concepts partly lose their relevance when changing from a 1D earth structure (only radial variations) to a 2D or a 3D earth structure (lateral variations). In regions like Fennoscandia and Laurentide, which are affected by GIA, lateral variations of the lithosphere and mantle structure are moderate and, so, the application of a 1D earth structure is widely accepted. But, also for these two regions one has to keep in mind that the respective 1D earth structures differ and that such an approximation mainly holds in the central part of the respective region. In contrast, lateral variations or a local structure of different viscosity have to be considered in areas like Patagonia, Antarctica or Alaska which is located above tectonic activity or covers a region with significant lateral changes in earth structure. But, already for the two former examples one has to keep in mind that the respective 1D earth structures inferred from GIA modelling differ between the two regions. Focusing on the relaxation behavior and the mantle-material transport, we discuss the effect of lateral variations on the deformation process. We will assess to which extent a 1D earth structure can represent lateral variability in structural features, and, at which point a 3D earth structure has to be considered. Such questions are of concern, when discussing GIA for geodetic applications as well as in earth system modeling as this study contributes to the climate modeling initiative Palmod.