Search

Varicoceles are a common cause of male infertility, affecting up to 35% of men undergoing fertility evaluations. This study aims to investigate the potential influence of altitude and residence time on the occurrence of varicoceles, as well as on sperm quality and sterility in plateau areas. A total of 168 patients with varicocele were enrolled in the study, and the study population was divided into groups based on their direct exposure to different high altitudes due to their living locations. The internal diameter in Quiet breath (Dr), internal diameter in Valsalva maneuver (Dv), reflux peak value, and reflux time are gradually increased accompanied with altitude elevation and residence time extension. The number of cases above 4,500 m also increased with the severity of varicocele, and the altitude of clinical types was higher than that of subclinical types of varicocele. Especially above 4,500 m, the Dv, Dr, reflux peak value, and reflux time all increased with the severity of varicocele. The severity of varicocele was positively correlated with the residence time in plateau area. Patients with residence time of more than 1 year had higher values of Dr, Dv, differentiation time, reflux peak value, and reflux time than those with residence time of less than 1 year. Compared to 3,650 m, patients with varicocele in 4,500 m also have worse semen quality. Both altitude and residence time are strongly positively related to the severity and incidence rate of varicocele in plateau areas. [ABSTRACT FROM AUTHOR]

• Sand wedge deposits were identified in the Early Miocene Wuqia Group. • Sand wedges occurred in braided fluvial environment under arid and cold climate. • The northern Tibetan Plateau surpassed 1000 m elevation in the Early Miocene. The uplift of the Tibet Plateau and its climatic effects have long been a hot topic in academic research. However, there is still significant controversy regarding the uplift history and related climate changes along the northern margin of the plateau. In this paper, we present sand wedge deposits from the base of the Wuqia Group (∼20 Ma) on the southwestern Tarim Basin, representing the oldest reported sand wedges in the Tibetan Plateau. A comprehensive study was conducted on lithostratigraphy, sedimentary environment, and macroscopic–microscopic features of the sand wedge deposits. The results indicate that the lithostratigraphic succession preserving the sand wedge deposits consists mainly of lenticular conglomerates and cross-bedded gravelly sandstone interbedded with medium–thin-bedded mudstone, consistent with the braided fluvial environment. The sand wedge deposits commonly exhibit a V-shape geometry and are filled with gravelly sandstone, with the gravels arranged parallel to the walls of the wedge. The clasts of the wedge-filled sandstone are well-rounded and show a unimodal grain size distribution. The quartz surfaces commonly display dish-shaped and crescent-shaped impact features, indicating an eolian origin and an arid climate. Based on the relationship between the formation temperature of modern sand wedges, the atmospheric temperature gradient, and altitude, the reconstructed paleo-elevation of the sand wedge deposits at the base of the Wuqia Group in the southwestern Tarim Basin is approximately ∼ 1000 m. These results indicate that the northern margin of the Tibet Plateau had already reached an elevation of ∼ 1000 m during the Early Miocene, forming a seasonal arid and cold climate. [ABSTRACT FROM AUTHOR]

The Late Paleozoic Ice Age is characterized by diverse stratigraphic records with extensive spatial-temporal distribution in the Gondwana. The Lhasa terrane located in northeastern Gondwana during the late Paleozoic developed successive glacial sedimentary records, but the depositional evidence, as well as age constraint for the onset of glaciation, is unknown. This paper provides the first full description of the basal glacial deposits in the Xainza area of Lhasa terrane, southern Tibet. Conodonts present in the carbonate overlying the glacial bed (1 m) dominantly consist of Declinognathodus intermedius , indicating that the initiation of the Late Paleozoic Ice Age in the Lhasa terrane took place in Bashkirian. Three facies associations were recognized: (i) tidal flat association (subtidal channel, bar, intertidal mixed flat), (ii) subglacial association (megaclasts and melt-out diamictite), and (iii) lonestone-bearing heterolithic association (grounding-line fan and iceberg). These facies associations are vertically arranged into a complete transgressive-retrogressive glacial succession. Ice movement direction reconstructed from the imbricated megaclasts, the concordant folds and the lateral distribution of subglacial deposits and glacial marine deposits is consistently from NNE to SSW. These characteristics suggest that the Bashkirian glaciation in the Lhasa terrane is irrelevant to western Australia, implying that these two blocks were separated during the Late Carboniferous. • The initiation of the LPIA in the Lhasa terrane took place in Bashkirian. • The tidal flat, subglacial and lonestone-bearing heterolithic associations were recognized. • The reconstructed ice movement direction is from NNE to SSW. • The Bashkirian glaciation in the Lhasa terrane is irrelevant to western Australia. • The Lhasa terrane was separated from Australia during the Late Carboniferous. [ABSTRACT FROM AUTHOR]

Abstract: Upper Jurassic–Lower Cretaceous transitional successions are widely distributed in the Tethyan Himalaya, southeast of Yangzuoyong Co Lake, southern Tibet. In ascending order, these include the Weimei (J3, Tithonian), Sangxiu/Jiabula formations (K1, Berriasian). The J/K boundary is located between the Weimei Formation and Sangxiu/Jiabula Formations. Ammonites found in J/K boundary sections in the research area have been classified into three assemblages: Valanginites–Phyllopachyceras assemblage zone (Valanginian), Spiticeras–Thurmanniceras assemblage zone (Berriasian) and Haplophylloceras–Blanfordiceras–Himalayites assemblage zone (Tithonian). Six nannofossil zones: Calcicalathina oblongata assemblage zone, Speetonia colligate zone, N. st. steinmannii zone, N. st. minor zone, P. beckmanni–N. st. minor interval zone, Conusphaera–Polycostella–Nannoconus–Watznaueria assemblage zone were recognized as well. On the basis of lithology, biostratigraphy and geochronology of the J/K transitional deposition succession, this study suggests that the J/K boundary, in southern Tibet, is located on the bottom of P. beckmanni–N. st. minor interval zone, which is further definited as and disappear of Polycostella beckmanni. To address the paucity of previously reported reliable ages for the J/K boundary, this study reports four U–Pb zircon ages (140–142 Ma) obtained with Secondary Ion Mass Spectrometry (SIMS) from the volcanic rocks interbedded in the lower Sangxiu Formation, which is expected to provides a direct date reference for the J/K boundary in the Tethyan Himalaya, southern Tibet. From integration of our new (SIMS) U–Pb zircon ages with calcareous nannofossils and ammonites, the age of the N. st. minor zone (NK-D) directly above the P. beckmanni-N. st. minor interval zone (NJK-C) of the basal Berriasian in the Tethyan realm is estimated to be 141–142 Ma. This research is not only helpful to improve the isotopic determination of absolute age for the J/K boundary, but also implies that the Tethyan Himalaya of southern Tibet may be an ideal location in which to explore the J/K boundary in both biostratigraphy and geochronology in future. [Copyright &y& Elsevier]