A revised lower estimate of ozone columns during Earth’s oxygenated history

The history of molecular oxygen (O 2 ) in Earth’s atmosphere is still debated; however, geological evidence supports at least two major episodes where O 2 increased by an order of magnitude or more: the Great Oxidation Event (GOE) and the Neoproterozoic Oxidation Event. O 2 concentrations have likely fluctuated (between 10 −3 and 1.5 times the present atmospheric level) since the GOE ∼2.4 Gyr ago, resulting in a time-varying ozone (O 3 ) layer. Using a three-dimensional chemistry-climate model, we simulate changes in O 3 in Earth’s atmosphere since the GOE and consider the implications for surface habitability, and glaciation during the Mesoproterozoic. We find lower O 3 columns (reduced by up to 4.68 times for a given O 2 level) compared to previous work; hence, higher fluxes of biologically harmful UV radiation would have reached the surface. Reduced O 3 leads to enhanced tropospheric production of the hydroxyl radical (OH) which then substantially reduces the lifetime of methane (CH 4 ). We show that a CH 4 supported greenhouse effect during the Mesoproterozoic is highly unlikely. The reduced O 3 columns we simulate have important implications for astrobiological and terrestrial habitability, demonstrating the relevance of three-dimensional chemistry-climate simulations when assessing paleoclimates and the habitability of faraway worlds.

Hermann Löns’ “Quintär” – an early approach to the geological stratigraphy of the Age of Humans and its significance in geosciences

In 1908, Hermann Löns outlined the concept of a Quintär” (“Quintary period”) to describe geological and biological manifestations of the Age of Humans. His definition of the “Quintary” consisted of twocomponents: a lithostratigraphical (“Quintary deposits” or “Quintary stratum”), and a faunistic (“Quintary fauna”) one. With a view on the stratigraphical component, Löns already anticipated the approach of the 21st Century to establish a geological definition for the Age of Humansbased on physical manifestations and geological evidence, that is nowadays reflected in the attempts to define the anthropocene. Transposed into modern terminology, the “Quintary stratum” is definedas a lithostratigraphical unit (Quintary Lithosome), that contains all deposits in which non-anthropogenic sedimentary processes have been replaced or modified by anthropogenic or technogenic activity. The Quintary Lithosome has a diachronous base and intercalates in its lower part vertically and laterally with non-anthropogenic deposits of the Holocene Series. The upper part, that correlates with the anthropocene series, has a global distribution. The Quintary Lithosome is exclusively defined for geological stratigraphies on Earth. It widely – though not totally – overlaps with the archaeosphere as a partial equivalent in archaeological stratigraphy. Previous suggestions to redefine the mostrecent period of Earth history by adopting a biostratigraphical scheme based on hominids and their cultural manifestations, are rejected hereinfor the realm of geological stratigraphy. However, for the context of archaeological stratigraphy, it is suggested to define the phase of cultural manifestations of hominins and their corresponding deposits as the Anthropian age and deposits, respectively.

Informed Decisions Guided by GeoMechanics to Improve Drilling Performance: A Case Study from Onshore Field, Abu Dhabi; UAE

ADNOC (Abu Dhabi National Oil Company) recently drilled some wells in Onshore Abu Dhabi (Field-A) and encountered consistent hole instability from Umm Er Radhuma (UER) to Simsima. Thus, a GeoMechanical review was proposed to investigate the root causes, if any, and recommend possible remedies for the upcoming drilling campaign. While detailed drilling event analysis allowed to investigate the correlation between the mud weight program and well trajectory, borehole image log analysis and geological understanding from nearby fields indicated the possible role of structural and lithological features on hole instability. Integration of drilling engineering data and regional geological knowledge helped to narrow down the possible causes of drilling challenges. Sedimentalogical review of Image logs have established some correlation between rock types and hole instability events. Drilling experience shows there is very narrow margin for loss and/or gain to occur. There is regional geological evidence of the presence of a wide range of vuggy structures, as well as natural fractures and/or faults. These features tend to make Simsima formation heterogeneous in terms of permeability and more prone to losses. Since most fractures are parallel to SHmax direction and well was drilled towards Shmin direction, there are greater chances of encountering faults and/or fractures, which would be critically-stressed and lead to loss and/or gain situations. Geomechanical parameters helped highlight the magnitudes and orientations of principal stresses. Observations of several tight hole and stuck pipe events while tripping from Radhuma and UERB shale to Simsima seem to indicate mud weight used was insufficient. Role of multiple failure mechanisms was identified, and relevant solutions were recommended as well as implemented to achieve the drilling success. The case study presented here emphasizes how different carbonate textures and the presence and orientation of natural fractures and/or faults within Simsima formation can impact hole instability with respect to wellbore trajectory. Proactive implementation of recommendations from this analysis on well planning and fluid design resulted in improvement of drilling performance and reduction of non-productive time in new wells.

Biogeography of Neotropical Meliaceae: geological connections, fossil and molecular evidence revisited

We here provide, first, a general introduction into the woody angiosperm family Meliaceae, including updated numbers of the genera and species found in different parts of the globe, paying attention to geographic centres of diversity and patterns of endemism. Second, and more specifically, we review the latest literature concerning land connections (i) between Eurasia and North America, (ii) between North America and South America, as well as (iii) dispersal paths between Africa and South America that have existed since the proposed evolutionary origin of modern Meliaceae, i.e. from the Upper Cretaceous onwards (ca. 100 Million years ago). Comparing geological evidence with the fossil record as well as biogeographic studies, there is indication that the nowadays pantropically distributed family has made use of all these three routes. Five out of the eight modern Neotropical genera have a fossil record, namely Carapa Aubl., Cedrela P. Browne, Guarea F. Allam., Swietenia Jacq., and Trichilia P. Browne. Carapa and Trichilia have a modern transatlantic disjunction (distribution in Africa, Central and South America), and a fossil record in Africa and North/Central America (Trichilia), or Africa and Eurasia (Carapoxylon). Cedrela has a rich fossil record in Eurasia and the Americas. The global decrease in temperatures and a lack of Cedrela fossils in North America from the Late Miocene onwards suggest the genus had gone extinct there by that time, leading to its modern distribution in Central and South America. Oligocene to Pliocene fossils of Guarea, Swietenia and Trichilia in Central American key regions support biotic interchange between North and South America at various times.

New Geological Evidence of the 1755 Lisbon Tsunami from the Rock of Gibraltar (Southern Iberian Peninsula)

This paper presents the easternmost mineralogical and geochemical evidence of the 1755 Lisbon tsunami found in the Western Mediterranean. This multidisciplinary analysis of a sediment core obtained in Gibraltar (southern Iberian Peninsula) has allowed us to differentiate a tsunamiite from an old lagoon (The Inundation). This tsunamigenic layer has increased levels of calcite and aragonite and higher concentrations of Ba and ferromagnesian elements in comparison with the underlying lagoonal sediments of this core. This layer is also differentiated by its paleontological record, with the introduction of marine species within this lagoon. The uppermost part of the core includes a transition from swampy/marsh paleoenvironments to terrestrial scenarios, with a final anthropogenic filling occurring during the last century.

Geological evidence of an unreported historical Chilean tsunami reveals more frequent inundation

Assessing tsunami hazards commonly relies on historical accounts of past inundations, but such chronicles may be biased by temporal gaps due to historical circumstances. As a possible example, the lack of reports of tsunami inundation from the 1737 south-central Chile earthquake has been attributed to either civil unrest or a small tsunami due to deep fault slip below land. Here we conduct sedimentological and diatom analyses of tidal marsh sediments within the 1737 rupture area and find evidence for a locally-sourced tsunami consistent in age with this event. The evidence is a laterally-extensive sand sheet coincident with abrupt, decimetric subsidence. Coupled dislocation-tsunami models place the causative fault slip mostly offshore rather than below land. Whether associated or not with the 1737 earthquake, our findings reduce the average recurrence interval of tsunami inundation derived from historical records alone, highlighting the importance of combining geological and historical records in tsunami hazard assessment.

Geology and geochemistry of jasperoids from the ‘Montaña de Manganeso’ district, San Luis Potosí, north-central Mexico

Large outcrops of jasperoids occur in the ‘Montaña de Manganeso’ mining district in north-central Mexico. They range from massive manganiferous jasperoids to highly brecciated, hematitic jasperoid. The jasperoids of ‘Montaña de Manganeso’ occur mainly as replacements of limestone, sandstone and shale, commonly nearby high-angle fault systems. The mineralogy of the jasperoids consist of quartz and its polymorphs (chalcedony, tridymite and cristobalite), Fe-Mn oxyhydroxides, calcite and minor barite. Many outcrops show evidence of several periods of brecciation and silicification. The geochemical signature of the jasperoids suggests that silicification was product of hydrothermal activity. The jasperoids display enrichment in elements of hydrothermal provenance such as Ba, Sr, As, Cr, Mo, Sb, Ni, Zn and Cu, whereas are strongly depleted in the elements indicative of clastic sources such as Ti, K, Th and Zr. Element ratios such as (Fe+Mn)/Ti, Al/(Al+Fe+Mn), Fe/Mn and U /Th, along with the Al-Fe-Mn and Fe-Mn-(Ni+Co+Cu)×10 ternary diagrams confirm a hydrothermal origin. Low ∑REE, an enrichment of LREE over HREE, negative Ce anomalies and positive Y anomalies (YPASS/HoPAAS) also support the hydrothermal processes. The geological evidence, in the form of a feeder zone and extensive hydrothermal alteration, show that the silica forming the rocks originated from ascending hot fluids.

Habitability of the early Earth: liquid water under a faint young Sun facilitated by strong tidal heating due to a closer Moon

Geological evidence suggests liquid water near the Earth’s surface as early as 4.4 gigayears ago when the faint young Sun only radiated about 70% of its modern power output. At this point, the Earth should have been a global snowball if it possessed atmospheric properties similar to those of the modern Earth. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as reservoirs or traps for heat. For now, the faint-young-Sun paradox persists as an important problem in our understanding of the origin of life on Earth. Here, we use the constant-phase-lag tidal theory to explore the possibility that the new-born Moon, which formed about 69 million years (Myr) after the ignition of the Sun, generated extreme tidal friction—and therefore, heat—in the Hadean and possibly the Archean Earth. We show that the Earth–Moon system has lost $${\sim }3~{\times }~10^{31}$$ ∼ 3 × 10 31 J (99% of its initial mechanical energy budget) as tidal heat. Tidal heating of $${\sim }10\,\mathrm{W\,m}^{-2}$$ ∼ 10 W m - 2 through the surface on a time scale of 100 Myr could have accounted for a temperature increase of up to $$5\,^\circ $$ 5 ∘ C on the early Earth. This heating effect alone does not solve the faint-young-Sun paradox but it could have played a key role in combination with other effects. Future studies of the interplay of tidal heating, the evolution of the solar power output, and the atmospheric (greenhouse) effects on the early Earth could help in solving the faint-young-Sun paradox.

THE RESIZING OF THE MOST POWERFUL ITALIAN INSTRUMENTAL EARTHQUAKE (SEPTEMBER 8, 1905, CALABRIA REGION, SOUTHERN ITALY)

The 8 September 1905 Calabria earthquake is the seismic event for which the Italian Seismic Catalogue shows the highest instrumental magnitude of the whole dataset. However, the reported Ms=7.47 was calculated over only two stations, and leaves room for a revision. In this work I provide a new estimate of the surface-wave magnitude of the earthquake calculated over sixteen individual values of magnitude from seven different stations. The new estimate is Ms=7.06±0.13, a value that is consistently lined up with other estimates provided by means of macroseismic or geological evidence. The novel estimate is stable despite alternative epicentral locations and different depths proposed for this event by several investigators. The net variation of almost half a unit magnitude implies a resizing of the seismogenic source of the event in the frame of the seismotectonics of the region, and highlights the strong need for a systematic revision of the instrumental magnitude estimates for several ‘historical’ earthquakes that occurred at the dawning of the instrumental seismology.

Holocene surface-rupturing earthquakes on the Dinaric Fault System, western Slovenia

The Dinaric Fault System in western Slovenia, consisting of NW–SE-trending, right-lateral strike-slip faults, accommodates the northward motion of Adria with respect to Eurasia. These active faults show a clear imprint in the morphology, and some of them hosted moderate instrumental earthquakes. However, it is largely unknown if the faults also had strong earthquakes in the late Quaternary. This hampers our understanding of the regional tectonics and the seismic hazard. Geological evidence of co-seismic surface ruptures only exists for one historical event, the 1511 Idrija earthquake with a magnitude of ∼ M 6.8, but the causative fault is still disputed. Here we use geomorphological data, near-surface geophysical surveys, and paleoseismological trenching to study two of these faults: the Predjama Fault and the Idrija Fault. In a paleoseismological trench across the Predjama Fault we found deformation features that may have been caused by an earthquake between 13–0.7 ka, very likely not earlier than 8.4 ka. At the Idrija Fault, a surface-rupturing earthquake happened around 2.5 ka. We show that instrumental and historical seismicity data do not capture the strongest events in this area.