Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

ABSTRACT The monograptids from the Wenlock and Ludlow (mid- to late Silurian) of the palaeotropical Baltic Basin exhibit thickened ring structures (sicular annuli) over their initial phase of growth. Appearing before the lundgreni extinction event, they persisted throughout the remainder of the Silurian, fluctuating in number over that period. To better understand the mechanisms controlling their development and variation, counts of sicular annuli were taken from three well cores in Lithuania, compared between species in each sample and compared with contemporaneous gamma ray data, accompanied by the stable isotope (δ13C), and acritarch diversity data. Mean counts of annuli fluctuated greatly over the studied interval, but showed negligible variation between species, indicating that the trait is ecophenotypic. The fluctuation in annulus presence aligned with variations in fourth- and fifth-order cycles derived from the gamma ray trends, which represent significant sea level fluctuations, δ13C ratios, and primary productivity, suggesting that annuli were more plentiful in high-stand states which are associated with the wetter climate and more productive conditions, whereas dryer, less productive conditions were not conducive to annulus development. In light of this evidence, we hypothesise that the action of upwelling as a result of intensified storm events during wetter periods would have encouraged phytoplankton blooms, increasing construction of annuli. These results show the potential utility of sicular annuli in the study of Silurian climate change and give new insights into graptolite palaeoecology.

On the enigma of Palaenigma wrangeli (Schmidt), a conulariid with a partly non-mineralized skeleton

Palaenigma wrangeli (Schmidt) is a finger-sized fossil with a tetraradiate conical skeleton; it occurs as a rare component in fossiliferous Upper Ordovician strata of the eastern Baltic Basin and is known exclusively from north Estonia. The systematic affinities and palaeoecology of P. wrangeli remained questionable. Here, the available specimens of P. wrangeli have been reexamined using scanning electron microscopy and x-ray computed tomography (microCT). Additionally, the elemental composition of the skeletal elements has been checked using energy dispersive X-ray spectroscopy. The resulting 2D-, and 3D-scans reveal that P. wrangeli consists of an alternation of distinct calcium phosphate (apatite) lamellae and originally organic-rich inter-layers. The lamellae form four semicircular marginal pillars, which are connected by irregularly spaced transverse diaphragms. Marginally, the diaphragms and pillar lamellae are not connected to each other and thus do not form a closed periderm structure. A non-mineralized or poorly mineralized external periderm existed originally in P. wrangeli but is only rarely and fragmentary preserved. P. wrangeli often co-occurs with conulariids in fossil-rich limestone with mudstone–wackestone lithologies. Based on the new data, P. wrangeli can be best interpreted as a poorly mineralized conulariinid from an original soft bottom habitat. Here the new conulariinid family Palaenigmaidae fam. nov. is proposed as the monotypic taxon for P. wrangeli.

Navigation system for unmanned vessels using a navigation buoy

Nowadays the floating aids to navigation are being actively developed for remote control of the buoy location. The modern technical level allows building a buoy with the functions of monitoring the environment and transmitting the received information to coastal services. This task is becoming more urgent in connection with the development of unmanned vessels. The paper considers the results of field tests of an operating navigation buoy with special navigation equipment. The buoy is designed for information support during field tests of unmanned vessels and water transport facilities in the test water area in the Volga-Baltic basin of the inland waterways of the Russia Federation. Full-scale tests of special navigation equipment were carried out in accordance with the developed program and test procedure. The tests included the validation of the receipt of data from special navigation equipment to an external server via LTE mobile networks, assessment of the accuracy of positioning by means of navigation equipment, assessment of the percentage of data loss during transmission and validation of data visualization on an interactive map displayed in an Internet browser.

Brittle Creep and Viscoelastic Creep in Lower Palaeozoic Shales from the Baltic Basin, Poland

The paper analyses the mechanical properties of shales from the Baltic Basin, focusing on creep strain in conditions of variable stress and elevated temperature (85 °C). Rock samples were collected from drill cores from various depths between 3600–4000 m. A series of creep tests was performed using a triaxial apparatus in simulated pressure and temperature conditions in the reservoir. The creep tests were conducted at variable levels of differential stress in variable time intervals. The laboratory experiments were performed in order to study brittle and viscoelastic creep proceeding in time in shales rich in organic matter and clay minerals. Creep compliance of shale formations rich in organic matter influences the success of hydraulic fracturing procedures, as well as migration of natural gas during exploitation. Laboratory characteristics of geomechanical properties (compressive strength, strain and elastic moduli) is crucial for planning natural gas exploitation from unconventional resources. The results indicate that the level of constant differential stress and creep time significantly influence the mechanical properties of shales. The paper presents the differences between brittle and viscoelastic strain registered during creep tests at variable stress conditions and time intervals. In viscoelastic creep tests, creep strain is over two times larger in the second stage of creep in comparison to the magnitude of strain registered in the first stage. In brittle creep tests, axial strain in the first creep stage is two times larger than in viscoelastic creep tests in the second stage. Based on the experiments, elastic parameters, i.e., Young’s modulus and Poisson’s ratio, have been determined for each of the analysed samples. In brittle creep tests, Young’s modulus is smaller than in viscoelastic creep tests. In viscoelastic creep tests Young’s modulus increases in successive stages. Whereas Poisson’s ratio is larger for samples from brittle creep tests than for samples from viscoelastic creep tests and does not change with subsequent creep stages in viscoelastic creep tests.

Early Holocene bark-stripping damages as an indicator of large herbivores: Evidence from a submerged Mesolithic landscape in the Haväng area, southern Baltic basin

A unique assemblage consisting of 113 pine samples collected from a submerged Mesolithic landscape in the Haväng area, southern Sweden, was examined to assess the presence of large herbivores, as well as changes in wild-game population density and composition. Bark-stripping damages on prehistoric trees is an extremely underutilized source of information about past game-population dynamics, yet our analyzes of wood samples – dated to around 10 500 cal. yr. BP – shows that such material can be successfully used to study the presence and activities of large herbivores, most likely ungulates. To evaluate our results, comparisons have been made with subfossil peatland trees that grew around 6000 years ago, as well as trees from two present day clearcut logging sites in southern Sweden. Furthermore, studies in a wild-game reserve were performed to recognize and understand different types of damages on trees caused by ungulates. Bark-stripping indicate the presence of ungulates, and the rate of damage is commonly associated with the density of the wild game. Bark-stripping was most frequently observed in the submerged wood material from the early Holocene, where damages were detected in 15% of the trees. In comparisons, 11% of the mid-Holocene trees show bark-stripping damages, whereas marks could be detected in the range between 0% and 6% of the trees from the two present-day clearcut logging sites. Our results show that tree-ring analyzes of prehistoric wood can generate information about wild-game dynamics of the past, and thereby being a valuable complement to more commonly used paleoecological and zooarcheological records.

Prediction of Reservoir Parameters of Cambrian Sandstones Using Petrophysical Modelling—Geothermal Potential Study of Polish Mainland Part of the Baltic Basin

Important factors controlling the effective utilization of geothermal energy are favorable reservoir properties of rock formations, which determine both the availability and the transfer opportunities of reservoir fluids. Hence, crucial to the successful utilization of a given reservoir is the preliminary recognition of distribution of reservoir parameters as it enables the researchers to select the prospective areas for localization of future geothermal installations and to decide on their characters. The objectives of this paper are analyses and discussion of the properties of quartz sandstones buried down to a depth interval from about 3000 to under 5000 m below surface. These sandstones belong to Ediacaran–Lowery Cambrian Łeba, Kluki and Żarnowiec formations. The source data from the Słupsk IG-1 provided the basis for 1D reconstruction of burial depth and paleothermal conditions as well as enabled the authors to validate of the results of 2D models. Then, porosity distribution within the reservoir formation was determined using the modelings of both the mechanical and chemical compactions along the 70 km-long B’-B part of the A’-A cross-section Bornholm-Słupsk IG-1 well. The results confirmed the low porosities and permeabilities as well as high temperatures of the analyzed rock formations in the Słupsk IG-1 well area. Towards the coast of the Baltic Sea, the porosity increases to more than 5%, while the temperature decreases, but is still relatively high, at about 130 °C. This suggests the application of an enhanced geothermal system or hot dry rocks system as principal methods for using geothermal energy.