Stable isotope analysis of the Cenomanian–Turonian (Late Cretaceous) oceanic anoxic event in the Crimea

Carbon and oxygen isotope data from Cenomanian–Turonian sediments from the southwest of the Crimea are presented. The sediments consist of limestones, marls and organic-rich claystones, the latter with total organic carbon values up to 2.6 wt. %, representing Oceanic Anoxic Event 2. A shift to more negative δ¹⁸O values through the uppermost Cenomanian into the lowermost Turonian may be the result of warming; however, petrographic analysis shows that the samples have undergone a degree of diagenetic alteration. The carbon isotope data reveal a positive excursion from 2.7‰ to a peak of 4.3‰ at the Cenomanian/Turonian boundary; values then decrease in the early Turonian. This excursion is comparable to those of other Cenomanian–Turonian sections, such as those seen in the Anglo-Paris Basin, and is thought to be due to global changes in the oceanic carbon reservoir. On this curve are a number of negative δ¹³C excursions, just below the Cenomanian/Turonian boundary. It is suggested that these negative excursions are associated with the uptake of light carbon derived from the oxidation and deterioration of organic material during localised exposure of the sediments to oxic or meteoric diagenetic conditions, possibly during sea-level fluctuations.     

Modelling microseismicity of a producing reservoir from coupled fluid‐flow and geomechanical simulation

In this paper, we investigate production induced microseismicity based on modelling material failure from coupled fluid‐flow and geomechanical simulation. The model is a graben style reservoir characterized by two normal faults subdividing a sandstone reservoir into three compartments. The results are analysed in terms of spatial and temporal variations in distribution of material failure. We observe that material failure and hence potentially microseismicity is sensitive to not only fault movement but also fluid movement across faults. For sealing faults, failure is confined to the volume in and around the well compartment, with shear failure localized along the boundaries of the compartment and shear‐enhanced compaction failure widespread throughout the reservoir compartment. For non‐sealing faults, failure is observed within and surrounding all three reservoir compartments as well as a significant distribution located near the surface of the overburden. All shear‐enhanced compaction failures are localized within the reservoir compartments. Fault movement leads to an increase in shear‐enhanced compaction events within the reservoir as well as shear events located within the side‐burden adjacent to the fault. We also evaluate the associated moment tensor mechanisms to estimate the pseudo scalar seismic moment of failure based on the assumption that failure is not aseismic. The shear‐enhanced compaction events display a relatively normal and tight pseudo scalar seismic moment distribution centred about 10⁶ Pa, whereas the shear events have pseudo scalar seismic moments that vary over three orders of magnitude. Overall, the results from the study indicate that it may be possible to identify compartment boundaries based on the results of microseismic monitoring.     

Provenance and tectonic implications of Orán Group foreland basin sediments,Río Iruya canyon,NW Argentina (23° S)

Foreland basins are important recorders of tectonic and climatic processes in evolving mountain ranges. The Río Iruya canyon of NW Argentina (23° S) exposes ca. 7500 m of Orán Group foreland basin sediments, spanning over 8 Myr of near continuous deposition in the Central Andes. This study presents a record of sedimentary provenance for the Iruya Section in the context of a revised stratigraphic chronology. We use U‐Pb zircon ages from six interbedded ash layers and new magnetostratigraphy to constrain depositional ages in the section between 1.94 and 6.49 Ma, giving an average sedimentation rate of 0.93 ± 0.02 (2σ) km Myr^?1. We then pair U‐Pb detrital zircon dating with quartz trace‐element analysis to track changes in sedimentary provenance from ca. 7.6 to 1.8 Ma. Results suggest that from ca. 7.6 to ca. 6.3 Ma, the Iruya watershed did not tap the Salta Group or Neogene volcanics that are currently exposed in the eastern Cordillera and Puna margin. One explanation is that a long‐lived topographic barrier separated the eastern Puna from the foreland for much of the mid‐late Miocene, and that the arrival of Jurassic‐Neogene zircons records regional tectonic reactivation at ca. 6.3 Ma. A second major provenance shift at ca. 4 Ma is marked by changes in the zircon and quartz populations, which appear to be derived from a restricted source region in Proterozoic‐Ordovician meta‐sediments. Considered in conjunction with the onset of coarse conglomerate deposition, we attribute this shift to accelerated uplift of the Santa Victoria range, which currently defines the catchment's western limit. A third shift at ca. 2.3 Ma records an apparent disconnection of the Iruya with the eastern Puna, perhaps due to defeat of the proto Rio‐Iruya by the rising Santa Victoria range. This study is one of the first applications of quartz trace‐element provenance analysis, which we show to be an effective complement to U‐Pb detrital zircon dating when appropriate statistical methods are applied.     

Variability of Sea-Ice Extent in Baffin Bay over the Last Millennium

Comparison of an ice core glaciochemical time-series developed from thePenny Ice Cap (PIC), Baffin Island and monthly sea-ice extent reveals astatisticallysignificant inverse relationship between changes in Baffin Bay spring sea-iceextent andPenny Ice Cap sea-salt concentrations for the period 1901–1990 AD.Empiricalorthogonal function analysis demonstrates the joint behavior between changesin PICsea-salt concentrations, sea-ice extent, and changes in North Atlanticatmosphericcirculation. Our results suggest that sea-salt concentrations in snowpreserved on thePIC reflect local to regional springtime sea-ice coverage. The PIC sea-saltrecord/sea-ice relationship is further supported by decadal and century scalecomparisonwith other paleoclimate records of eastern Arctic climate change over the last700 years. Our sea-salt record suggests that, while the turn of the century wascharacterized bygenerally milder sea-ice conditions in Baffin Bay, the last few decades ofsea-ice extentlie within Little Ice Age variability and correspond to instrumental recordsof lowertemperatures in the Eastern Canadian Arctic over the past three decades.     

Microbiological estimate of water quality in the Amur and Sungari rivers after a technogenic accident in China in 2005

The results of microbiological water quality monitoring in the Amur and Sungary rivers after a technogenic accident in Tzilin province (China) in November 2005 are considered. Bioindication technique is used to show that various pollutants earlier entered the Amur with the Sungari runoff: low-molecular volatile benzene derivatives entered from November 28 to December 2; naphthalene derivatives entered from November 29 to December 7; and nitrobenzene and high-molecular polyaromatic hydrocarbons entered in December 15–23, 2005. The major portion of pollutants moved along the right bank. The most sensitive to the total pollution by toxic substances were nitrifying bacteria, especially in bottom water layers. The Amur water in the zone of influence of the Sungari was estimated to belong to the IV–V quality class and referred to the categories of “polluted” and “dirty.” The poor quality of Amur water persisted over 9 months throughout the Amur reach from the Sungari mouth to Khabarovsk City.     

Life in the Slow Lane: Growth and Longevity of Cold-seep Vestimentiferans

Abstract. Yearly, in situ growth of two species of cold-seep vestimentiferan tubeworms was measured using a combination of banding and video analysis. A total of 53 animals from 15 different aggregations were included in the study, which was conducted over a Cyear period. The most common species, Lamellibrachia sp., grows very slowly (averaging 0.77 cm. a^-1) and yet commonly reaches lengths over 2 m. Based on conservative calculations we conclude that individuals in mature aggregations are a minimum of 100 a old and are likely to be much older. Smaller numbers of a second species of vestimentiferan (related to escarpids) were also monitored over this period. We consider it likely that the individuals of the second species banded for this study were already on the plateau of their growth curve, and that the very low average growth rates recorded here would lead to an overestimate of the ages of the individuals used in this study. However, life history considerations combined with the extremely low measured growth rates of this species suggest it is also long-lived.     

The kinematics of solar inner coronal transients

Solar Physics - The kinematic properties of a dozen ‘loop-like’ coronal transients have been examined over the range 1.2–2.4 R⊙ from Sun center. Values and trends of...     

The response of vegetation cover and dune activity to rainfall,drought and fire observed by multitemporal satellite imagery

The stable longitudinal dunes in the northern Simpson Desert, Australia, were observed in satellite imagery to become more active after vegetation cover was reduced by fire and drought. Subsequent rainfall events also resulted in significant vegetation regrowth and dune stabilization. These switches between more active and stable conditions have not been previously described in the largely vegetated dune fields of central Australia. The observations, made on 12 dune sites, relied on high spatial resolution satellite imagery to observe dune crest activity, and seasonal Landsat fractional cover imagery to observe vegetation cover changes. The non-photosynthetic vegetation (NPV) component of the fractional vegetation cover images revealed significant changes in hummock grass cover on the dunes between 1988 and 2018, with a positive relationship with the three-year cumulative rainfall, disrupted by two periods of patchy burning. Only those sites that had burnt became active, and only after vegetation cover had remained low (NPV < 16%) during the ‘Millennium Drought’. There is no threshold in vegetation cover, below which dune crests become active, but active dune features require four-years of low NPV cover (< 16%) to develop. The large rainfall event that ended the drought increased NPV cover, stabilizing the dunes. Similar hummock grass covered dunes are present across large areas of the arid zone, and are likely to respond in similar ways, given that fire and drought are common occurrences in Australia. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Integrating land-cover data with different ontologies: identifying change from inconsistency

Spatially coincident land-cover information frequently varies due to technological and political variations. This is especially problematic for time-series analyses. We present an approach using expert expressions of how the semantics of different datasets relate to integrating temporal time series land-cover information where the classification classes have fundamentally changed. We use land-cover mapping in the UK (LCMGB and LCM2000) as example data sets because of the extensive object-based meta-data in the LCM2000. Inconsistencies between the two datasets can arise from random, gross and systematic error and from an actual change in land cover. Locales of possible land-cover change are inferred by comparing characterizations derived from the semantic relations and meta-data. Field visits showed errors of omission to be 21% and errors of commission to be 28%, despite the accuracy limitations of the land-cover information when compared with the field survey component of the Countryside Survey 2000.