Hispanic Corridor formed as early as Hettangian: On the basis of bivalve fossils

After tracking the historical distribution of the pectinids being very capable of dispersion, it is easy to be found that the bivalves Chlamys (Chlamys) valoniensis (Defrance), Camptonectes (Camptonectes) auritus (von Schlo-theim) and Chlamys (Chlamys) textoria (von Schlotheim) first occurred in the Late Rhaetian, the end of the Triassic, or the earliest Hettangian, the earliest Jurassic of western Europe, and subsequently they spread into the southeastern coast of Palaeo-pacific through the Hispanic Corridor during the Hettangian or a little later. It has demonstrated that the Hispanic epicontinental seaway became established along the rifting area between North America and South America and Africa of the Pangaean supercontinent as early as Hettangian or even earlier, connecting western Tethys and eastern Palaeo-pacific and providing a corridor for migration and exchange of creatures between Tethys and Palaeo-pacific.

西藏海相三叠系—侏罗系界线及晚三叠世生物绝灭事件研究

1998—2004年间在西藏聂拉木、林周、墨竹工卡和洛扎等地进行的三叠系/侏罗系界线地层研究表明,西藏隆子县和洛扎县尚未发现具有连续菊石层序的三叠系/侏罗系界线地层剖面。拉萨以北地区广泛分布的火山岩时代确定为晚三叠世—早侏罗世早期,这有助于解释晚三叠世末期生物绝灭与晚三叠世岩浆侵入和大规模的火山活动有关,但T/J界线尚待精确限定。聂拉木县格米格剖面是特提斯地区唯一未曾“压缩”的三叠系/侏罗系界线地层剖面,具有瑞替阶MARSHI菊石带、赫塘阶Tibeticum、Callyphyllum和Pleuro-notum菊石带。格米格剖面三叠系/侏罗系界线碳稳定同位素曲线记录了晚三叠世瑞替阶末期(Marshi菊石带)突然的负偏移,它很有可能和晚三叠世末期的由超级温室效应所产生的生物绝灭事件相对应。

Sequence Stratigraphy of the Jurassic Coal Measures in Northwestern China

The sequence stratigraphy of the Jurassic coal measures of northwestern China has been studied based on data from outcrop and borehole sections. Because of the geological background and the diversity of basin types, such as isochronisms of coal seams and recognition of key sequence boundaries, it is rare to summarize and correlate sequence structure and framework. The types and recognition characteristics of the sequence boundaries of the Jurassic coal measures are revealed by comparing climatic characteristics, structural styles and the base level cycle. A total of five third-order sequences and 15 systems tracts have been subdivided and the sequence stratigraphic framework has been reconstructed confirming that the thick coals accumulated in the late stage of transgression system tracts of sequence I （SQ I） and sequence III （SQ III）. This idea is of important academic significance for instructing coal resources exploration, and enhancing geological effects of prospecting engineering. It is also of practical significance for guaranteeing construction of the large-scale coal production base in northwestern China, accelerating the westward development of the coal industry stratagem.

Stratigraphy of the Triassic-Jurassic Boundary Successions of the Southern Margin of the Junggar Basin,Northwestern China

The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected： the Late Triassic （Rhaetian） Aratrisporites-Alisporites Assemblage, the Early Jurassic （Hettangian） Perinopollenites-Pinuspollenites Assemblage, and the Sinemurian Perinopollenites-Cycadopites Assemblage. The Tr-J boundary is placed between bed 44and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha （？）, Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized. The Ferganoconcha （？） bed is limited to the upper Haojiagou Formation,Unio- Ferganoconcha and Waagenoperna- Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites and the marine-littoral facies bivalve Waagenoperna from the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.

陕西榆林-横山地区富县组孢粉组合

本文研究了陕西榆林-横山地区富县组孢子花粉66属88种(包括一个新种),建立了该区富县组孢粉组合。根据孢粉组合确定富县组地质时代为早侏罗世,其下部相当于早侏罗世早期赫唐期或辛涅缪尔期。作者还根据孢粉植物群的演替,探讨了该区早侏罗世的古气候特征。