The Upper Jurassic sediments,Marib-Shabwa Basin,Yemen:Lithofacies aspects and sequence stratigraphic analysis

The present study is devoted to understanding the evolution of the Upper Jurassic Sab'atayn Formation in the Marib-Shabwa Basin,Yemen,through a sequence stratigraphic analysis based on integrating datasets of sedimentology,seismic sections,and well logs.The Sab'atayn Formation(Tithonian age)is represented by a series of clastic and evaporites that were deposited under fluvio-deltaic to prodeltaic settings.It is divided into four members including Yah(at the base),upwards to Seen,Alif,and Safir at the top.Two third-order depositional sequences were determined for the Tithonian succession which were separated by three sequence boundaries.These sequences were classified into their systems tracts signifying several sedimentation patterns of progradational,aggradational,and retrogradational parasequence sets.The first depositional sequence corresponds to the early-middle Tithonian Yah and Seen units that can be classified into lowstand,transgressive,and highstand systems tracts.The second sequence comprises the late Tithonian Alif unit that can be subdivided into transgressive and highstand systems tracts.The sandy deposits of the Alif Member(highstand deposits)represent the most productive hydrocarbon reservoir in the basin.The Upper Jurassic sediments in the study area were resulted from a combination of eustatic and tectonic effects.

The First Stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic Shishugou Formation of Xinjiang, China

A new stegosaur species, Jiangjunosaurusjunggarensis, gen. et sp. nov., is erected based on a specimen collected from the Upper Jurassic upper section of the Shishugou Formation in the Junggar Basin, Xinjiang, China. It represents the first stegosaur from the Jurassic of Xinjiang and increases the diversity of the dinosaur fauna in the Shishugou Formation. The new genus is characterized by symmetrical and proportionally wide tooth crowns, a sub-rectangular axial neural spine seen in lateral view, and large openings on the lateral surfaces of the cervical centra. A preliminary character analysis suggests that this new taxon is more derived than the Middle Jurassic stegosaur Huayangosaurus but more primitive than most other known stegosaur species.

Revision of the Clam Shrimp Genus Magumbonia from the Upper Jurassic of the Luanping Basin,Hebei,Northern China

The diverse clam shrimp Nestoria-Keratestheria fauna is widely distributed in the Dabeigou Formation in northern Hebei and eastern Inner Mongolia of China. Its important component genus Magumbonia from the Dabeigou Formation in the Luanping Basin, northern Hebei, China, is revised on the basis of a scanning electron microscope （SEM） examination of the type species M.jingshangensis Wang, 1984, which revealed morphological features not recognized previously. These include coarse reticulation on the umbo and prominent growth lines ornamented with densely spaced, small tubercles and fine lirae.

Characteristics of the Upper Jurassic Marine Source Rocks and Prediction of Favorable Source Rock Kitchens in the Qiangtang Basin, Tibet

This study evaluated the hydrocarbon-bearing potential of Upper Jurassic marine source rocks in the Qiangtang （羌塘） Basin through a comprehensive organic geochemical analysis of the samples from a large number of outcrops in different structural units to predict the location of favorable hydro- carbon kitchens, based on the evaluation standards of Mesozoic marine source rocks in the Qiangtang Ba- sin. Rocks＇ depositional environment, thickness and organic geochemistry feature were analyzed in this study. The principal controlling factors of the occurrences of favorable source rocks were analyzed. Upper Jurassic Suowa （索瓦） Formation source rocks are mainly platform limestone in the Dongcuo （洞错）-Hulu （葫芦） Lake deep sag and Tupocuo （吐坡错）-Baitan （白滩） Lake deep sag. Lithologically, the Suowa Fro- mation is made up of a suite of marls in intra-platform sags, micrites and black shales, which were all de- posited in the closed, deep and static water depositional environment. Marl could form hydrocarbon-rich source rocks and its organic matter type is mainly II type in mature to highly-mature stage, the limestone forms a medium-level source rock. In addition, the favorable source kitchen of limestone is larger than that of mudstone. This study provides an important reference for the evaluation of Jurassic marine source rocks and for prediction of petroleum resources in the Qiangtang Basin.

Stratigraphy and palaeoenvironments across the Jurassic-Cretaceous boundary in the reference section (Olenek River) for eastern regions of Laptev Sea area (Arctic Siberia,Russia)

The Volgian-Valanginian succession of shallow-water deposits from the Olenek section(Anabar-Lena region,Arctic Siberia)has been studied by sedimentological and palaeontological methods.High-resolution biostratigraphy of studied interval is based on the ammonites,foraminifers,marine and terrestrial palynomorphs.Foraminiferal and palynological zones have important regional implications providing well-constrained biostratigraphy of the Anabar-Lena region.Sedimentological studies together with ecological analysis of the associations of microbenthos,microphytoplankton and terrestrial palynomorphs allow the palaeoenvironmental reconstructions for the marginal area of the Anabar-Lena palaeosea and coastal land areas.

Lebanese Amber: A Fantastic Journey into the Time of Dinosaurs

The history of amber and its trade in Lebanon dates back to ancient times,during the Phoenician civilization.Amber in Lebanon can be found in over 450 outcrops,comprising approximately 10%of the country’s land.Some of these outcrops are Late Jurassic(Kimmeridgian)in age,while the majority are Early Cretaceous(early Barremian).The Early Cretaceous amber found in Lebanon is the oldest amber with extensive biological inclusions,making it a crucial source of knowledge regarding continental palaeobiodiversity during the Early Cretaceous period.This period is widely recognized as witnessing the first occurrence and early evolution of angiosperms,representing a critical time for the co-evolution between flowering plants and insects.In Lebanese amber,biological inclusions often serve as records of the earliest representatives of modern living insect families or the youngest ones for extinct families.

Recent approach to Buchia biostratigraphy from the Tethyan Himalaya area,China

Recent collections from six sections in Lanongla area,Tethyan Himalaya allow the establishment of four buchia assemblages.In ascending order,they are Buchia-Buchia spitiensis,Buchia masquensis-Buchia rugasa,Buchia blanfordiana,Buchia piochii and Buchia subokensis assemblages.These Buchia assemblages first demonstrate that not only the Upper Jurassic strata but also the highest Buchia assemblage-Buchia subokensis,which appeared in Lower Cretaceous strata all over the world are present in Lanongla area.This first records the highest Buchia assemblage in Lanongla area.