Late Substage Research Articles

Этапы подготовки к прерывистому скольжению на предварительно вырезанных разломах в лабораторных моделях и проверка этапов в природе

This study is focused on analog modeling of the stick-slip process along an existing large fault in an elastic-viscoplastic model subjected to loading at a constant strain rate. Based on our model results and data from (Ma et al., 2012, 2014), we distinguish stable, meta-stable, and meta-instable stages of the stick-slip process (the latter includes the early and late sub-stages). Our experiments show that the fault is periodically reactivated by segmentation. We analysed this mechanism from one fault reactivation to another, and identified regressive and progressive trends of segmentation. The regressive segmentation takes place during the stable and meta-stable stages of the stick-slip process. Under regressive segmentation the number of active segments and their lengths are reduced. The progressive segmentation is initiated at the early meta-instable sub-stage of the stick-slip process. Its activity is desplayed by an increase in the number of active segments to a certain critical density, while their pattern becomes more chaotic. In the late sub-stage, number of segments decreases as they rapidly grow and join with each other to form larger active segments, up to full reactivation of the entire fault. For comparison with the model results, we interpret rock deformation monitoring records before the Bystroe earthquake. Our analysis confirms specific features of the anomalous rock deformation that are similar to the strain features observed along the model fault during the meta-instable stage. There are evidence to suggest that meta-instability of a fault is a potential candidate to short-term precursor of earthquakes.

Cryohydromorphic paleosols in the north of West Siberia as indicators of the warm stages of the Late Pleistocene and their link to the cryogenesis development

The aim of the study. The aim of the study was to find and justify specifics of the paleosol development in the north of West Siberia, revealing soils levels, associated with climate warming during sea isotope stages (SIS), namely MIS-5, MIS-3 and at the end of MIS-2. Location and time of the study. The research was conducted during the last 10 years in the representative area between the Polar Circle and the sub-latitudinal sector of the Ob river all over the area. We carried out paleopedological and paleocryological investigations with fieldwork in the basin of the Vakh River (right tributary of Ob), the Taz and Nadym Rivers, where the soil pits were studied, and paleosols were discovered for the first time. Methods. The methodology has been focused on detailed study of the paleosols discovered by the present authors based on the investigation in respect to the interaction of paleopedogenetic and cryogenetic processes. Also, the encountered paleosols have been, as well compared to the surface Holocene soils that comprises an important element of analysis of the paleopedological records. For age determination we applied radiocarbon dating of organic residues and humus, contained in the paleosols, as well as U/Th-dating in paleosols. Results. Several paleosol levels were identified in the study area. The paleosol of the early substage of MIS-5 (MIS-5e) had signs of forest pedogenesis without permafrost, whereas the soils of late substages of MIS-5 and MIS3 showed evidence of gleying and cryogenesis; the paleosol corresponding to the end of MIS-2 was best represented by gleyic pedosediments in the ice-wedge pseudomorphs. The studied paleosols indicate the permafrost state of the soil-forming sediments in all phases of the Late Pleistocene with the exception of MIS-5e; the finding is important for the paleoenvironmental reconstruction. The article presents the data about wide distribution in the study region of the polygonal structures represented by the ice-wedge pseudomorphs formed in the coldest phases MIS-4 and MIS-2. The pseudomorphs were developed syn-cryogenically when permafrost still existed and were closely related to the formation of cryohydromorphic paleosols. Within the entire sequence of MIS-3 deposits initially ground wedges are common, also indicating syn-cryogenic development, however, under less strong freezing conditions than during MIS-2. Yet at the end of MIS-3 in the upper part of the sequence cryohydromorphic soils appeared again, as a sign of approaching to the MIS-2 cryochron. It was shown that the fills of the ice wedge pseudomorphs contain well preserved redeposited materials of the cryohydromorphic paleosols, including fragments of the humus horizons. It was suggested that the material from such redeposited pedosediments could be used for the radiocarbon dating and for sampling for the paleobotanical investigations. Conclusions. The obtained results cast doubt on the hypothesis of domination of the cold deserts and ice sheets in the study region during the Pleistocene and hence the formation of only extremal soils. There is evidence indicating the existence of well-developed vegetation and soil cover during the cryochrons with sufficient and in some areas excessive soil moisture, due to shallow permafrost table. The interaction of the paleopedogenetic and paleocryogenic processes resulted in rather informative relict objects, and their studies provide highly reliable results about the factors of past pedogenesis.

Size adjustment occurs during the larval growth of the separated blastomeres of the starfish, Patiria Pectinifera.

Starfish embryos derived from blastomeres separated at the early cleavage stage exhibit morphogenesis to form normally shaped, but smaller-sized dwarf bipinnaria larvae. To further understand this developmental capacity, we primarily characterized the morphogenetic processes of separated 2-cell and 4-cell stage blastomeres during the embryonic and larval periods of the starfish, Patiria Pectinifera. Using non-separated blastomeres as the control, we subjected the separated blastomeres to morphological analyses in conjunction with quantitative measurements of the changes in their body sizes with time post-fertilization. Our results were as follows: (i) Blastomeres separated at 2-cell and 4-cell stages synchronously developed into dwarf-sized bipinnaria larvae. (ii) Upon reaching a body size of 500-700 μm, all the bipinnaria larvae originating from the separated blastomeres and controls began to undergo a series of similar organ formation events in preparation for metamorphosis-recognized as the demarcation between the early and late substages of the bipinnaria larval period. (iii) The separated blastomeres became brachiolaria larvae capable of undergoing metamorphosis at differing rates after reaching approximately 1000-1200 μm body sizes, with adult rudiment and sensory organ forming functionally. (iv) The unfed controls and dwarf bipinnaria larvae derived from blastomeres separated at the 4-cell stage arrested their development synchronously without reaching the threshold size required for the latter half of the bipinnaria stage. These results, taken together, suggested that separated blastomeres possess the developmental capacity to become brachiolaria larvae through a shift in morphogenetic regulation from a synchronous growth to size adjustment during the larval period.

Petrogenetic peculiarities of Fe-Ti oxide minerals in the processes of crystallization and evolution of late Cretaceous volcanic complexes of the Lesser Caucasus


 
 
 
 Drawing from the determined differences between iron-titanium oxide minerals, we analyzed the conditions of crystallization and evolution of late-Cretaceous magmatic complexes of the Lesser Caucasus. It was found that the rocks of basalt-andesibasalt complex, which correspond to the early substage (upper Coniacian-lower Santonian) of late-Cretaceous volcanism in the Qazakh, Agjakand, Agdara depressions, have crystallized in the conditions of relatively highly- thermobaric crystallization of titanomagnetite, poorly differentiated and evolutionized according to the Fenner trend. In the second substage of volcanism, due to decrease in permeability of the Earth’s crust, the elevation of the remaining magma to the upper horizons was hindered. Therefore, within the Qazakh depression, shallow intermediate sites of crystallization developed where moderately titaniferous magnetite crystallized with the participation of oxidized fluids earlier than hornblende, pyroxene and plagioclase. Thus, the remaining magma evolutionized its composition through Bowen’s reaction series. In the Agjakand and Agdara depressions, change of previous expansion to compaction was the cause of hindering of partly fractioned portion of the magma. The latter thermally interacted with the above-embedded maghemite, hematite and in a number of cases magnetite. In the Khojavand depression, rocks of trachibasalt- trachiodolerite complex, which characterize the late substage of the Santonian volcanism, contain moderately titanium magnetites and maghemites. In the second substage of volcano-plutonism, rocks of tephrite-teshenite complex developed. There, accompanied by oxidized fluids, highly-clayey titanomagnetite crystallized before chrome-diopside and salite. However, the ulvospinel titanomagnetite in teshenites, having associated with barkevikite and kaersutite, crystallized at a relatively higher temperature. Within the Senonian volcanites of the Azykh depression, along with the moderately-titanium magnetite, chromic titanomagnetite and rarely chromite was determined. Similar mineralogical diversities are also characteristic for the Gochas depression.
 
 
 

Ore genesis of Qingyunshan Cu-Au deposit in the Dehua-Youxi area of Fujian Province, southeastern China: Constraints from U-Pb and Re-Os geochronology, fluid inclusions, and H-O-S-Pb isotope data

The Qingyunshan Cu-Au deposit, located in the Dehua-Youxi area (Fujian Province, southeastern China), is a vein-type deposit that occurs along fractured zones in the Late Jurassic volcanic-sedimentary rocks and Early Silurian intrusions. Three mineral paragenetic stages are identified, including the pyrite-quartz veins (stage I), polymetallic sulfide-quartz-calcite veins (stage II), and calcite (±siderite)-chalcedony-comb quartz veins (stage III). The stage II is the main mineralization stage, dominated by pyrite, chalcopyrite, and galena as well as two generations of Fe-poor sphalerite with average Fe content of 0.84 wt% in the early sub-stage and 0.31 wt% in the late sub-stage. Fluid inclusion studies indicate that the stage I has a temperature of 220–240 °C and salinity of 3.00–3.50 wt% NaCleq., whereas the stage II has lower temperature (140–160 °C), but similarly low salinity (2.50–3.00 wt% NaCleq.), suggesting it is an intermediate-low temperature epithermal deposit. Hydrogen and oxygen isotope data indicate the fluids of stage I has a δD value of −72.5 to −69.5‰ and δ18Ow value of −2.96 to −0.46‰, whereas the stage II fluids show similar or slightly higher δD value (−68.0 to −66.5‰), but significantly lower δ18Ow value from −6.96 to −6.26‰, which suggest meteoric water predominated in the ore-forming fluid and shows an increasing trend from stage I to II. The δ34S values of sulfide minerals are between −3.7 and −2.3‰, consistent with a major magmatic sulfur source. The lead isotope data show a relatively narrow range with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of 18.392–18.513, 15.642–15.758, and 38.497–39.043, respectively. These Pb-isotope data are similar to those of the Late Jurassic intrusions, but quite different from those of the surrounding rocks of Early Silurian quartz diorite. Pyrite from the ores yielded a Re-Os isochron age of 158.1 ± 9.3 Ma, which is similar to the zircon U-Pb age (162.0 ± 1.0 Ma) of the host dacite crystal tuff in the Nanyuan Formation. Therefore, we concluded that the Late Jurassic magmatic activity (ca. 160 Ma) has a genetic relation with formation of the Qingyunshan vein-type Cu-Au deposit, for which the ore metals were mainly derived from the magma, but ore-forming fluids evolved from a mixing of magmatic fluids and meteoric water with the later playing a major role in the main stage of ore formation.

The genesis of gold deposits in the Hetai goldfield, South China: New constraints from geochronology, fluid inclusion, and multiple isotopic studies

The Hetai goldfield is one of the largest gold mining districts in the South China Block. A complex paragenesis consists of three mineralization stages: syntectonic metamorphic stage, hydrothermal stage, and supergene stage. The syntectonic metamorphic stage is characterized by banded quartz (Q1) and invisible Au in mylonites. The hydrothermal stage, which is the main gold mineralization stage, can be divided into three substages: an early substage characterized by coarse‐grained quartz (Q2) + pyrite + arsenopyrite + pyrrhotite, an intermediate substage characterized by gray fine‐grained quartz (Q3) + electrum + poly‐sulphides + sericite + chlorite and a late substage with predominate white quartz (Q4) + calcite as well as lesser sulphides. During the supergene stage, malachite, covellite, and limonite were formed. Four types of fluid inclusions (FIs) in these types of quartz were identified: aqueous FIs (type 1), CO2‐bearing aqueous FIs (type 2), CO2‐rich FIs (type 3), and solid‐bearing FIs (type 4). Q1 only contains type 1 FIs; Q2 contains types 2 and 4 FIs; Q3 contains types 2 and 3 FIs; and Q4 only contains type 1 FIs. Microthermometric results show that the homogenization temperatures of fluid inclusions range from 350°C to 400°C for Q1, 250°C to 320°C for Q2, 138°C to 245°C for Q3, and 110°C to 207°C for Q4. Salinities of fluid inclusions range from 3.4 to 5.7 wt.%, 2.6 to 12.9 wt.%, 0.5 to 11.5 wt.%, and 0.2 to 7.3 wt.% for Q1, Q2, Q3, and Q4, respectively. Alteration minerals (sericite and chlorite) from the main mineralization stage have δDH2O‐VSMOW values of −62‰ to −98‰ and calculated δ18OH2O‐VSMOW values of 6.3‰ to 4.4‰. The in situ sulphur isotope analysis of pyrite yields a narrow δ34SCDTrange of −1.5‰ to −5.2‰ (average −3.4‰), combined with the Pb isotopic compositions of the sulphides, wall rocks, and Wucun pluton, revealing that the ore‐forming material was mainly derived from magmatic source. The mineralization age (sericite40Ar/39Ar: 159.3 ± 0.8 Ma) is close to the emplacement age of Wucun biotite monzonitic granite pluton (LA‐ICP‐MS zircon U–Pb age: 158.1 ± 1.9 Ma). These geochemical and geochronological data suggest that the main phase of gold mineralization in the Hetai goldfield is genetically related to the granitic activities in the Late Jurassic rather than the mylonitization event in the Late Triassic to Early Jurassic.

Invisible gold in arsenian pyrite from the high-grade Hishikari gold deposit, Japan: Significance of variation and distribution of Au/As ratios in pyrite

Au and As concentrations in pyrite grains from the Hishikari deposit were extensively determined by secondary ion mass spectrometry (SIMS) and electron probe microanalysis (EPMA) to investigate the microscale relationship between Au and As. The low-sulfidation epithermal Hishikari deposit, which has produced more than 224 t of gold since 1985 (as of March 2016), is world-famous for its high-grade ore. Accurate quantitative SIMS analyses of Au in pyrite were possible by preparing an Au-implanted pyrite standard sample and by using a properly tuned SIMS analytical method. An analysis size of 3 μm was chosen since the pyrite grains from the Hishikari deposit have heterogeneous As concentrations. This paper presents the first comprehensive data set of Au and As concentrations in a 3 μm area of pyrite obtained from the widely distributed high-grade Au-bearing Hishikari veins.Microanalyses of arsenian pyrite from the Hishikari gold deposit by SIMS and EPMA revealed that Au concentrations of 0.1–2800 ppm are positively correlated with As concentrations of 0 to 7 wt% in a 3 μm area. The formation of Hishikari veins is divided into two stages that are further subdivided into the early and late sub-stages. The rim of a pyrite grain precipitates after formation of the core; however, the time scale of core and rim formation is far shorter than that of the entire mineralization sequence. The specific value of the Au/As ratio in pyrite proves to be characteristic of the specific Au-bearing vein and its specific depth. Therefore, it could be possible to infer the nature of unknown veins by the Au/As ratio obtained. Although the Au/As ratio varies from vein to vein, a general tendency is observed for each ore zone of the Hishikari deposit. The Au/As ratio is high in the Sanjin ore zone, which consists of numerous high-grade veins in or above the Cretaceous accretionary sedimentary rocks of the Shimanto Group. The Au/As ratio is moderate in the Honko ore zone, which consists of several high-grade veins and also occurs in or above the basement sedimentary rocks. On the other hand, the Yamada ore zone, which consists of relatively low-grade veins, occurs in Pleistocene andesitic pyroclastic rocks that overlie the basement sedimentary rocks unconformably. The Au/As ratio in pyrite of the Yamada ore zone is relatively low compared with that of other ore zones.Several previous papers have proposed that the As− in pyrite may contribute to the reduction of Au+ to Au0 as Au nanoparticles (NPs) by As oxidation; however, Au and As concentrations of arsenian pyrites fall on or below the Au solubility limit in this study. Moreover, the As and S concentrations in pyrite are inversely correlated, which is consistent with the substitution of As for S as anionic As− in the Fe(S1−xAsx)2 solid solution of natural arsenian pyrite under reducing environments. The present study suggests that the Hishikari Au exists as a solid solution in the Hishikari arsenian pyrite, although there remains a possibility that it exists partially in the form of NPs even though the Au and As concentrations of arsenian pyrites fall on or below the Au solubility limit.

Organization and Behavior of the Synaptonemal Complex during Achiasmatic Meiosis of Four Buthid Scorpions

Testicular cells of 4 buthid scorpions, Rhopalurus agamemnon (2n = 28), R. rochai (2n = 28), Tityus bahiensis (2n = 6), and T. fasciolatus (2n = 14), which show different types of chromosomal configurations in meiosis I, were subjected to cellular microspreading in order to (1) obtain knowledge about the organization and behavior of the synaptonemal complex (SC), and (2) acquire data about the mechanisms responsible for inter- and intraindividual chromosomal variation within Buthidae. Ultrastructural analysis of microspread nuclei revealed SCs with a well-preserved structure until late substages of prophase I, but did not detect kinetochore plates and recombination nodules. Pachytene cells of R. agamemnon, R. rochai and T. bahiensis exhibited single and unsynapsed axes continuous with totally synapsed SCs, indicating the occurrence of heterozygous chromosomal rearrangements. Although chromosome chains were not observed in T. fasciolatus, the presence of gaps and interlocks points out that this species also carries heterozygous rearrangements, involving a small chromosome segment. Especially in R. rochai, the cellular microspreading analysis was useful to clarify the origin of inter- and intraindividual variation in the number of bivalent-like elements and in the number of chromosomes involved in multivalent associations. It was found that more chromosomes were involved in rearrangements than previously established through investigations using light microscopy alone.

Ontogeny, functional morphology, and comparative morphology of lower (Stage 4) and basal middle (Stage 5) Cambrian gogiids, Guizhou Province, China

Three gogiid eocrinoids, numbering in the thousands of specimens, are well known from the lower Cambrian (Stage 4) Balang Formation (Guizhoueocrinus yui) and basal middle Cambrian (Stage 5) Kaili Formation (Kaili Biota) (Sinoeocrinus lui and Globoeocrinus globulus) that resided on the Yangtze-South China Plate (modern Guizhou Province, China). In each species a complete ontogenetic sequence, using thecal height (TH) as a scale, juvenile stage (early, middle, and late substages), mature stage (early, middle, and late substages), and a gerontic stage can be identified. Sutural pores appeared in an orderly sequence; below the ambulacrals, above the stalk and generally over the theca, in that order. In younger species their emplacement and growth was commonly precocious relative to G. yui. Also, their shape ranges from circular to oval to triangular in a single growth sequence, after the establishment of the 2-1-2 pattern; brachioles were added in series of five and were also precocious in time of occurrence in younger species. Thecae in younger species tend to retain juvenile aspects relative to G. yui. All of these species lived in outer shelf settings in fine-grained, organic-rich siliciclastics.

Natural Apoptosis During the Blastogenetic Cycle of the Colonial AscidianBotryllus schlosseri: A Morphological Analysis

Colonies of the compound ascidian Botryllus schiosseri undergo regular generation changes, during which adult zooids are progressively resorbed and replaced by growing buds. The generation change, or take-over, is characterized by massive cell death by apoptosis, as indicated by nuclear condensation, activation of caspases, overexpression of molecules recognized by antibodies against mammalian Bax, Fas, and FasL, changes in the expression of surface molecules by senescent cells of zooid tissues, and recruitment of circulating phagocytes in zooid tissues which ensure the complete clearing of dying cells. The entire process lasts 24-36 h at 20 degrees C and has been subdivided, on the basis of the degree of contraction of old zooids, into four substages. In the present work, we carried out a detailed morphological analysis of the events occurring in zooid tissues during the take-over substages. Results Indicate that traces of apoptosis can be found in the epidermis, peribranchial epithelium, and heart in the late substage but are easily found in the branchial basket 2-4 h after the beginning of the generation change, thus confirming the antero-posterior progression of cell death, at least in the alimentary system.

New evidence for complex climate change in MIS 11 from Hoxne, Suffolk, UK

The climatic signal of Marine Isotope Stage (MIS) 11 is well-documented in marine and ice-sheet isotopic records and is known to comprise at least two major warm episodes with an intervening cool phase. Terrestrial records of MIS 11, though of high resolution, are often fragmentary and their chronology is poorly constrained. However, some notable exceptions include sequences from the maar lakes in France and Tenaghi Philippon in Greece. In the UK, the Hoxnian Interglacial has been considered to correlate with MIS 11. New investigations at Hoxne (Suffolk) provide an opportunity to re-evaluate the terrestrial record of MIS 11. At Hoxne, the type Hoxnian Interglacial sediments are overlain by a post-Hoxnian cold-temperate sequence. The interglacial sediments and the later temperate phase are separated by the so-called ‘Arctic Bed’ from which cold-climate macroscopic plant and beetle remains have been recovered. The later temperate phase was deposited during an episode of boreal woodland and is associated with the artefacts, a diverse vertebrate fauna and molluscs. New amino acid geochronological data and biostratigraphical considerations suggest that the post-Hoxnian sequence correlates with late substages of MIS 11. The paper further investigates the correlation of the sequence at Hoxne with the palynological sequences found elsewhere in Europe and adjacent offshore areas.

The Genesis of Epithermal Au-Ag-Te Mineralization, Panormos Bay, Tinos Island, Cyclades, Greece

The Panormos Bay Au-Ag-Te vein system, Tinos Island, Greece, which is hosted in Mesozoic marbles, comprises 30 subparallel, steeply dipping quartz veins that extend for at least 500 m. In places, gold telluride mineralization occurs in hydraulic breccias and alteration halos, which are the products of CO 2 effervescence of the ore fluid and wall-rock interaction, respectively. Seventy ore and gangue minerals have been identified. Zones of chlorite, talc, and muscovite-albite-tourmaline alteration, up to 50 cm wide, are associated with precious metal-bearing milky and clear quartz veins. The Au-Ag-Te mineralization is developed in stage V of eight hydrothermal stages. Stage V consists of three substages (early, middle, and late) that are characterized by Ag-, Cu-, and Au-bearing tellurides, respectively. Hessite, sylvanite, altaite, native tellurium, stutzite, cuprian cervelleite, and an unnamed Cu-bearing precious metal sulfotelluride [(Ag,Au,Cu) 9 Te 2 S 3 ] characterize the early substage, whereas melonite, rickardite, vulcanite, weissite, and native tellurium are present in the middle substage. The late substage contains rickardite, kostovite, krennerite, petzite, and calaverite. Unexploited Au-Ag-Te mineralization at Panormos Bay is though to be genetically related to a fluorine- and boron-bearing per-aluminous leucogranite (Tinos leucogranite). A combination of fluid inclusion microthermometry and sylvanite geothermometry suggests that the hydrothermal mineralization was deposited under hydrostatic pressures at a minimum depth of 1 km from moderate-temperature (155°–320°C), low- to moderate-salinity (0.2–13.2 wt % NaCl equiv), effervescing, CO 2 -bearing fluids that contained appreciable amounts of CaCl 2 and MgCl 2 . Calculated isotope compositions of δ 18 O = −3.3 to +5.1 per mil and δD of −73 to −62 per mil for waters in equilibrium with muscovite, quartz, and talc are consistent with the ore fluids being derived from the Tinos leucogranite (δ 18 O = +4.2‰ and δD = −71‰) and their subsequent mixing with a more dilute, low-temperature Miocenic meteoric hydrothermal fluid. Calculated δ 13 C fluid (−2.0 to −0.3‰) and δ 34 S H 2 S (−10.5 to +0.8‰) compositions of the ore fluids indicate an igneous source of carbon and sulfur, which were highly exchanged with a metasedimentary source. Physicochemical conditions of the ore fluids were T = 300° to 200°C, pH = 4.6 to 6.5, f S 2 = 10 −10.9 to 10 −15 , f O 2 = 10 −31.5 to 10 −41 , f Te 2 = 10 −7.7 to 10 −10.7 , f CO 2 = 10 −0.2 to 10 −0.8 , and f H 2 S = 10 −1.7 to 10 −1.8 .

Confirming and Disconfirming Theories About Ideomotor Compatibility in Dual-Task Performance: A Reply to Greenwald (2005).

Because small dual-task costs with ideomotor-compatible tasks do not necessarily indicate the absence of a bottleneck, M.-C. Lien, R. S. McCann, E. Ruthruff, and R. W. Proctor (2005) considered additional sources of evidence regarding bottleneck bypass. This evidence argued against complete bottleneck bypass and, instead, supported an engage-bottleneck-later model in which early bottleneck substages are bypassed but late substages are not. A. G. Greenwald (2005), however, contended that M.-C. Lien et al. did not use the procedures needed to produce complete bottleneck bypass and that a complete bottleneck bypass hypothesis, combined with additional assumptions, could explain their data. The authors contend that this disagreement stems from Greenwald's focus on confirming predictions of complete bottleneck bypass (small dual-task costs) without disconfirming predictions of bottleneck presence. In particular, Greenwald neglects to consider the possibility that a latent bottleneck limitation could also produce small dual-task costs.

Succession of secondary forests affected by pine wilt disease in western Japan followed on vegetation maps

Abstract. Succession, changes in the distribution pattern of forest vegetation, and Pinus forest survival following pine wilt disease were clarified based on phytosociological analysis and vegetation maps. Survival of Pinus forests was restricted to the early successional stages, which were located on ridges and the upper part of slopes. Subsequent to pine wilt disease, the succession progressed from early to late substages of Pinus forest, mixed deciduous and evergreen Quercus, to evergreen Quercus forest. Succession occurs in abandoned pine forests which apparently are in a bad state and are vulnerable to attacks by pine wilt disease.

Do Greenland Ice Cores Reflect NW European Interglacial Climate Variations?

The climatic evolution during the Eemian and the Holocene in western Europe is compared with the sea-surface conditions in the Norwegian Sea and with the oxygen-isotope-derived paleotemperature signal in the GRIP and Renland ice cores from Greenland. The records show a warm phase (ca. 3000 yr long) early in the Eemian (substage 5e). This suggests that the Greenland ice sheet, in general, recorded the climate in the region during this time. Rapid fluctuations during late stage 6 and late substage 5e in the GRIP ice core apparently are not recorded in the climatic proxies from western Europe and the Norwegian Sea. This may be due to low resolution in the terrestrial and marine records and/or long response time of the biotic changes. The early Holocene climatic optimum recorded in the terrestrial and marine records in the Norwegian Sea-NW European region is not found in the Summit (GRIP and GISP2) ice cores. However, this warm phase is recorded in the Renland ice core. Due to the proximity of Renland to the Norwegian Sea, this area is probably more influenced by changes in polar front positions which may partly explain this discrepancy. A reduction in the elevation at Summit during the Holocene may, however, be just as important. The high-amplitude shifts during substage 5e in the GRIP core could be due to Atlantic water oscillating closer to, and also reaching, the coast of East Greenland. During the Holocene, Atlantic water was generally located farther east in the Norwegian Sea than during the Eemian.

Late Pleistocene foraminiferal stratigraphy on the Vøring Plateau, Norwegian Sea

Quantitative studies of foraminiferal faunas and isotope ratios have been done in two gravity cores from the Vøring Plateau. Core 23199 from about 2000 m water depth included sediments younger than oxygen Stage 7. Core 23205 from about 1400 m ended in sediments from Stage 5. According to the transfer temperatures, the onset of abundances of Cibicidoides wuellerstorfi and the δ13C values of Neogloboquadrinapachyderma, the Vøring Plateau was covered by pack‐ice during Stages 6,4,2 and, to some extent, also during Stage 3. Ice‐free sea‐surface conditions prevailed from late Substage 5e throughout Stage 5 and during stage 1. The transition from Stage 6 to Stage 5 (Termination II) took place in two steps: Ila is defined by the δ18O signal of N. pachyderma (reduced global ice volume) and lib by the increased occurrence of C. wuellerstorfi (melting of local pack‐ice). A contemporaneous development of an interglacial deep‐water circulation system is indicated.

Crossing over in the male mouse as analysed by recombination nodules and bars

The present study of 26 serially sectioned mouse spermatocyte nuclei has permitted the following observations and conclusions: 1) The pachytene stage can be subdivided into an early, a mid, and a late substage. 2) A morphological change of the early spheric recombination nodule to an elongated bar is observed. 3) The number of recombination structures per nucleus decreases from a mean of 31 nodules and 2 bars at early pachytene to a mean of 8 nodules and 6 bars at mid pachytene. The number of nodules and bars remains virtually constant at late pachytene and early diplotene. 4) The number of bivalents with one and two nodules is higher than would be expected if the nodules were distributed at random. 5) Along the bivalents the frequency of nodules and bars exhibits a characteristic pattern of troughs and peaks. 6) The presence of a nodule/bar distally in the synaptonemal complex segment combining the X and the Y chromosomes strongly indicates the existence of an obligatory crossover between the terminal parts of the long arm of the X and Y chromosomes.

Human meiosis VII. Chiasma formation in human spermatocytes

The diplotene and diakinesis stages in human spermatocytes have been analyzed by serial sectioning and three dimensional reconstruction of 17 nuclei covering the period from early diplotene to prometaphase I. The analysis has permitted the following observations and conclusions: 1) The diplotene and diakinesis stages in human spermatocytes are very short but can be subdivided into early, mid and late substages on the basis of changes in nuclear shape, centriolar behaviour, synaptonemal complex elimination and bivalent contraction. The ultrastructure of the autosomal bivalents and the XY bivalent is described. 2) Synaptonemal complex elimination is initiated at a low number of sites at early diplotene, creating about 70 remaining stretches of synaptonemal complex. Degradation continues during diplotene but is confined to the ends of these segments as the total number of distinct segments is unchanged during diplotene. The distribution of the segments among and along the bivalents is similar to that of crossovers and chiasmata, suggesting that the crossovers are contained in these segments. In virtually all XY bivalents, a short synaptonemal complex segment combines the homologous regions of the X and the Y chromosome. 3) The length of the synaptonemal complex segments remains unchanged from early diakinesis until metaphase I. The mean number of segments at early-mid diakinesis amounts to 62. At late diakinesis the segments are eliminated and replaced by chromatin bridges, the eliminated segments forming small polycomplexes. By metaphase I these polycomplexes are shed from the bivalents. 5) A comparison between the chiasma distribution as seen in the light microscope and that of crossovers or synaptonemal complex segments at mid-late diplotene reveal that chiasmata occupy more distal positions. 6) It is proposed that the pattern of elimination of the synaptonemal complexes, at diplotene, reflects differences in their resistance towards degradation along the bivalent arms, regions of high probability for crossing over being less susceptible to breakdown. The segments which are preserved through early and mid diakinesis are assumed to have gained additional resistance as a consequence of crossing over in that region.

北陸の海岸砂丘

Some coastal sand dunes, such as the Himi, Uchinada, Katayamazu and Sanribama dunes, are distributed widely along the coast of the Japan Sea in the central Japan. I have made for about two decades research of the coastal sand dunes throughout the Japanese Islands, especially the Hokuriku district, from the view points of the age of formation of sand dunes, palaeoenvironment during the time of the formation of sand dunes and the relationship between the age of formation and change of sea-level.In this article I have proved the following six items in regard to the coastal sand dunes of the Hokuriku district:(1) Summary of some gists of the distribution, arrangement, basement and age of formation of the coastal sand dunes.(2) The age of formation of the coastal sand dunes which are distributed in the Hokuriku district is divided into seven periods as follows: First period-the Late Pleistocene Riss/Wurm Interglacial age, Hiradoko stage; Second period-the late substage of the Earliest Jomonian age to the early substage of the Early Jomonian age; Third period-the late substage of the Early Jomonian age, the highest sea-level stage of the Flandrian transgression age; Fourth period-the earliest substage of the Middle Jomonian age; Fifth period-the Late Jomonian age to Yayoian age; Sixth period-the early substage of the Tumulusian age, the old tomb age, the Minor transgression age; Seventh period-the middle Muromachi age. Among them, the time when larger dunes were formed is the fourth, fifth and sixth periods.(3) Judging from the view point of relationship between the formation of the coastal sand dunes and the palaeoenvironment in the time of formation, both the palaeotemperature and palaeomoisture during the Holocene epoch were not in direct connection with the formation of the coastal sand dunes.(4) The necessary conditions for the formation of the coastal sand dunes are the following: (a) supply of sand, (b) migration of sand, and (c) sedimentation of sand. The conditions were prescribed by a position of strand line, it needs the fix of the position of the strand line for the formation of the coastal sand dunes.(5) From the view point of relationship between the change of sea-level and the formation of the coastal sand dunes, when the environment was changed topographically by the change of sea-level, a scale of sand dune may be changed by the fact that the above-mentioned three conditions are promoted or hindered under this changed environment. Roughly speaking, better conditions for the formation of sand dune may be just after the time when a sea-level changes from rising to lowering.(6) The relationship between the relative change of sea-level, the change of palaeoenvironment and the formation of the coastal sand dunes in every stage of the Holocene epoch is described in this article in the concrete.