Том 24, № 2 (2024)

It is shown that during reversals in geodynamo models the minimum amplitudes of the dipole, quadrupole and octupole coincide. Since the characteristic time of the reversal is close to the oscillations of the large-scale geomagnetic field, a similar analysis was carried out for the minima of the amplitude of the dipole magnetic field over the past 100 thousand years. It turned out that in this case such synchronization also occurs. It can be assumed that reversals and large scale variations of the geomagnetic field between the reversals have a lot in common. The wavelet analysis carried out indicates that the concept of the main geodynamo cycle is very arbitrary: the period of oscillation can vary from 8–10 thousand years to 20–30 thousand for a dipole. Analysis of the evolution of the Mauersberger spectrum allows us to conclude that magnetic field fluctuations observed at the Earth’s surface are associated with the transfer of the magnetic field to the surface of the liquid core and can hardly be described by functions periodic in time.

Interior Fars region is an important geological province of Zagros basin due to historical events. The present paper focused on the time span of the Asmari deposition (Oligo-Lower Miocene) in Fars area bounded by Kazerun and Nezamabad faults. The studied samples of Asmari Formation were collected from 3 different stratigraphic sections A, B and C. The area is discussed in view of microfacies variation, sequence stratigraphy and environmental factors such as diagenetic processes and sea level changes. Microscopic studies led to identification 13 carbonate facies in this area. The results showed that the Asmari Formation has been deposited in a carbonate shelf in 5 sedimentary sub-environments including open sea, bar, lagoon, shoal and tidal flat. Basin changes were also compared with global sea level changes. Sequential stratigraphic evidence showed that the Asmari Formation consists of two sedimentary sequences of third order. The unconformity in the lower boundary of Asmari Formation with Jahrom Formation in sections-B and C can be ascribed to the result of Pyrenean orogenic phase activity in this area. The Asmari Formation in this area has been undergone extensively by diagenetic processes. Micriticization, dolomitization, cementation, hematitization, stylolitization, neomorphism and dissolution are among the important and noteworthy of diagenetic processes. The intensity of each process is a function of facies characteristics (fabric control). Microfacies data and sea level changes curve in local (the area), regional and global scales revealed that these facies are more correlated to the local sea level variation than others. The present study resulted to new main points related to the Fars basin evolution. Reactivation of faults (such as Kazerun and Nezamabad), regional sea level changes and Alpine orogenic phases impact (i.e., Pyrenean phase) have involved a major role in sedimentary facies distribution and basin evolution.

Investigating variability in phytoplankton primary productivity as a key component of the “biological pump” is critical to quantifying flux in the marine environment. We hypothesized that under certain hydrological conditions, changes in phytoplankton productivity are greater with changes in photosynthetic efficiency (the ratio of primary production (P P ) to the rate of electron transport in the phytoplankton photosystem, P P /ETR) than with changes in chlorophyll content. This study showed that increase of P P during sharp changes in hydrological parameters in the temporary frontal South-East Baltic (SEB) is achieved by increasing the efficiency of photosynthesis, i.e., the degree of use of light energy captured by chlorophyll a (Chl a). In the Gulf of Finland (GF), an increase in P P followed an increase in salinity from the Neva mouth to the sea and controls chlorophyll contents with low variability in photosynthetic efficiency. For SEB and GF, measurements of parameters of phytoplankton productivity and chlorophyll a content in late autumn (November) are carried out. The first stage of carbon flow (in biological pump), expressed in terms of primary production, was higher in the SEB than in the GF

The interannual variability of the ocean surface temperature in the area of the Peruvian upwelling for the period 1980–2022 is considered according to the satellite archive GODAS (Global Ocean Data Assimilation System) using the methods of multivariate statistical analysis. Local foci of significant trends, for average annual Sea Surface Temperature (SST) values, were identified near the Peruvian offshore. Four regions (clusters) were obtained, which describe the variability of SST in front off Peru, which could be used to pretend to develop a prognostic oceanographic model. Furthermore, coincidences of temperature fluctuations were found between the first cluster and the region N3+4