U–Pb dating of silicic lavas,sills and syneruptive resedimented volcaniclastic deposits of the Lower Devonian Crudine Group,Hill End Trough,New South Wales

The Hill End Trough of central‐western New South Wales was an elongate deep marine basin that existed in the Lachlan Fold Belt from the early Late Silurian to late Early Devonian. It is represented by a regionally extensive, unfossiliferous sequence of interbedded turbidites and hemipelagites of substantially silicic volcanic derivation, which passes laterally into contemporaneous shallow‐water sedimentary rocks. The Turondale and Merrions Formations of the Lower Devonian Crudine Group are two prominent volcanogenic formations in the predominantly sedimentary trough sequence. They contain a range of primary and resedimented volcanic facies suitable for U–Pb dating. These include widespread subaqueous silicic lavas and/or lava cryptodomes, and thick sequences of crystal‐rich volcaniclastic sandstone emplaced by a succession of mass‐flows that were generated by interaction between contemporaneous subaerial pyroclastic flows and the sea. Ion microprobe dating of the two volcanogenic formations by means of the commonly used SL 13 zircon standard yields ages ranging between 411.3 ± 5.1 and 404.8 ± 4.8 Ma. Normalising the data against a different zircon standard (QGNG) yields preferred slightly older mean ages that range between 413.4 ± 6.6 and 407.1 ± 6.9 Ma. These ages broadly approximate the Early Devonian age that has been historically associated with the Crudine Group. However, the biostratigraphically inferred late Lochkovian ‐ early Emsian (mid‐Early Devonian) age for the Merrions Formation is inconsistent with the current Australian Phanerozoic Timescale, which assigns an age of 410 Ma to the Silurian‐Devonian boundary, and ages of 404.5 Ma and 395.5 Ma to the base and top of the Pragian, respectively. There is, however, good agreement if the new ages are compared with the most recently published revision of the Devonian time‐scale. This suggests that the Early Devonian stage boundaries of the Australian Phanerozoic Timescale need to be revised downward. The new ages for the Merrions Formation could also provide a time point on this time‐scale for the Pragian to early Emsian, for which no data are presently available.     

Morphology and internal structure of two new abelisaurid remains (Theropoda,Dinosauria) from the Adamantina Formation (Turonian – Maastrichtian), Bauru Group,Paraná Basin,Brazil

The knowledge on the Brazilian theropod fauna is hampered by the limited number of specimens unearthed so far. The most potential deposits for the finding of those dinosaurs are the layers of Bauru Group, which comprises several different formations of Late Cretaceous age. Most of those remains are referred to Abelisauroidea, a clade that is particularly well represented in Gondwana. Here we report two new abelisaurid specimens comprising a left ilium (DGM 927-R) and the distal articulation of a right femur (MCT 1857-R) unearthed from the outcrops of Adamantina Formation (Turonian – Maastrichtian) in the locality known as Santo Anastácio, that comprises an abandoned quarry located in the outskirts of the homonymous city in São Paulo State. The ilium has a preacetabular process horizontally oriented and ventrally deflected, as well as an acute angle between this process and the pubic peduncle. The femur shows a well-developed anteromedial crest, but not to the same degree as in noasaurids, and ossified ridges between condyles and tibiofibular crest. Those features allow us to assign both specimens to Abelisauridae. CT-scans of those specimens shows that the ilium has pneumaticities similar to the camellate pattern previously recorded in neosauropods and reveals the diverticula invasion of abdominal air-sacs. The femur presents a developed anisotropic trabecular system, which suggests that the main muscular strain is located at the distal portion of this bone. These features have not been previously reported in Abelisauridae, indicating that the internal organization of the postcranial skeleton in the group is rather complex and quite variable.     

Discovery of 2Obaichthyidae gars (Holostei,Ginglymodi, Lepisosteiformes) in the Aptian Codó Formation of the Parnaíba Basin: Remarks on paleobiogeographical and temporal range

Here we report the first 2obaichthyid gar from the Lower Cretaceous (Aptian) Codó Formation of the Parnaíba Basin, Northeastern Brazil. It shows the following obaichthyid characters: numerous odontods firmly attached to the outer surface of the dermal bones, free and mobile maxilla, presence of interopercle, lack of contact between the metapterygoid and ectopterygoid, absence of lacrimomaxillary bones, and a prominent spine at the posterior margin of the scales. Due to the presence of scales bearing a prominent ventral posterior spine and a number of additional posterior marginal spines, the fish from the Codó Formation is noticeably the same species found in the Albian Santana Formation of the Araripe Basin, Dentilepisosteus laevis. Although probably restricted to fresh or brackish water, the new discovery adds one more taxon to the assemblages found in the Parnaíba and the Araripe basins. The new record extends the temporal range of this species down into the Aptian (about ∼10 myr older than the previous occurrence).     

The Early Cretaceous Jacuí Group,a newly discovered volcaniclastic–epiclastic accumulation at the top of the Paraná Basin,southern Brazil

The presence of volcaniclastic rocks related to the silicic magmatism within the Serra Geral Formation has been a matter of long-standing debate. In this paper, we present extensive documentation that supports the presence and abundance of these rocks in the Jacuí Group, a newly discovered volcaniclastic and epiclastic accumulation in southern Brazil. The Jacuí Group is composed of two interfingered stratigraphic units, the Volta Alegre and Tupanciretã formations, and it represents the uppermost stratigraphic unit of the Paraná Basin. The Volta Alegre Formation is primarily composed of resedimented volcaniclastic tuffites, the pyroclasts which were sourced from the Santa Maria subgroup of the Palmas-type of the Serra Geral Formation. The Tupanciretã Formation is composed of fluvial and aeolian deposits transported towards the north–northwest. Deposition of the Jacuí Group began in the Early Cretaceous (∼132 Ma) and was coeval with the acidic volcanism of the Santa Maria subgroup. This group was deposited in a probable interior sag basin that represents either the beginning of the extension in the inner part of the continent that subsequently migrated to the east or the far-field impact of extensional processes that preceded the break-up of Gondwana and the opening of the South Atlantic Ocean.     

Two new glaphyrids (Coleoptera,Scarabaeoidea) from the Jehol Biota,China

Two new species, Cretohypna puncta sp. nov. and Cretohypna robusta sp. nov., of Glaphyridae are described and illustrated. These fossils were collected from the Jehol Biota, Lower Cretaceous Yixian Formation of Liutiaogou Village in Ningcheng, Inner Mongolia, China. Up to date, 18 fossil species in 6 genera of Glaphyridae have been reported, among which ten species are from China. Respective keys to the Mesozoic genera of Glaphyridae and to species of Cretohypna Yan, Nikolajev & Ren, 2012 are provided. This is the first report of spiracles in fossil Glaphyridae leading to a hypothesis that the character of the 7th abdominal spiracles present in pleural membrane is a plesiomorphy for Glaphyridae.     

Mawsoniid remains (Sarcopterygii: Actinistia) from the lacustrine Missão Velha Formation (Lower Cretaceous) of the Araripe Basin,North-East Brazil

Mawsoniids are a lineage of extinct fresh/brackish water coelacanth fishes, common in Cretaceous Godwanan deposits of South America, North and West Africa and Madagascar. Here we formally describe mawsoniid remains from the fluvio-lacustrine Missão Velha Formation (Lower Cretaceous) of the Araripe Basin, North-East Brazil. The examples from the Missão Velha Formation are here described as Mawsonia cf. gigas, based mainly on elements of the lower jaw and opercular series. The occurrence of M. cf. gigas in the Missão Velha Formation expands the stratigraphic and geographical ranges of the type species.     

New fossil species of the Venicoridae (Heteroptera: Pentatomomorpha) from the Lower Cretaceous of Northeast China

Specimens of the Venicoridae (Heteroptera) occur in the Lower Cretaceous Yixian Formation in northeastern China. We describe a new genus and two new species Halonatusivena shii gen. et sp. nov. and Halonatusivena nervosus sp. nov. from this formation. The veins of the membrane are distinctive; the edges of veins are not simple but resemble an irregular stain, with a reduced vasiform structure previously unknown in the Heteroptera. Remarkably, the antennae of one of the specimens of Halonatusivena shii exhibit morphological abnormality. An identification key for the known species of the Venicoridae is provided.     

渝东南下古生界页岩构造裂缝形成及分布控制因素

天然裂缝对页岩气储集和渗流有重要影响,但目前对页岩构造裂缝研究不够深入。本文通过露头、岩心裂缝观察和分析,探讨了渝东南下古生界页岩构造裂缝类型、形成机理及分布控制因素。基于裂缝特征及力学成因,将剪切裂缝分为高角度剪切裂缝、倾斜滑脱裂缝和水平滑脱裂缝。倾斜滑脱裂缝是在上覆岩层重力和水平构造应力共同作用下沿应力集中的软弱面发生剪切滑动形成,水平滑脱裂缝是在构造挤压应力作用条件下主要沿页理面方向的剪切或层间滑动形成;页理发育程度及岩层曲率是控制水平滑脱裂缝形成的关键因素,岩石矿物组成、构造作用及岩层厚度是控制其它类型构造裂缝形成和分布的主要因素,页岩岩石力学层的划分需要根据裂缝特征、岩性变化特征、岩石力学参数及沉积界面等综合确定,岩层厚度与层间构造裂缝密度呈负相关关系。     

准噶尔盆地东部沙帐地区中二叠统平地泉组一段致密油源储组合模式

综合利用录井、镜下薄片及压汞等资料,对准噶尔盆地东部沙帐地区中二叠统平地泉组一段致密油储集层岩性、储集空间和孔隙结构等特征进行了分析,在此基础上结合平一段致密油纵向岩性组合特征及源储关系,总结了平一段致密油源储组合模式。研究发现平一段致密油储集层岩性以碎屑岩为主,云质类岩石次之,储层孔隙结构具"粗态型"、"偏细态型"和"细态型",储集空间表现为常规孔隙与纳米孔隙并存;平一段源储组合表现为"泥包砂"、"砂包泥"和"砂泥互层"。研究表明:平一段储集层表现为致密储层特征,纳米孔喉是致密油储层的主体孔喉,平一段致密油具有源储一体型、源储交接型和源储隔离型三类组合模式。     

Effects of low- to high-angle normal faults on sedimentary architectures in the Eocene Wenchang Formation,Enping Sag,Pearl River Mouth Basin,South China Sea

The effects of low- to high-angle (>30°) normal faults on sedimentary architectural units in the Eocene Wenchang Formation, Enping Sag, Pearl River Mouth Basin (PRMB), South China Sea were investigated utilising a high-quality 3D seismic data set and restored paleogeomorphology. It has been shown that sequence stratigraphic units and sedimentary architecture are significantly controlled by the low- to high-angle normal faults. The Wenchang Formation, a second-order sequence, can be subdivided into two para-second-sequences (the Lower and Upper Wenchang sequences, E₂W^L and E₂W^U) and seven third-order sequences (from base to top: SQ1～SQ7). The low-angle fault confined sequence architecture of the Wenchang Formation is mainly characterised by lateral stacking with the ratio of the vertical subsidence (V) to horizontal slip (H) being reduced from 1/2 for E₂W^L to 1/6 for E₂W^U. In contrast, the high-angle fault confined sequence is characterised by vertical stacking with the ratio of V/H close to 1 for sequences SQ1 to SQ7. In the 3D seismic area, the features of sediment-dispersal pattern were interpreted based on an integrated analysis of paleogeomorphology, seismic reflection characteristics, stratal thickness distribution and multiple attribute clustering. The results show that the large-scale fan delta, belt-shape lacustrine deposit and bird-foot braided delta systems mainly developed in the low-angle fault confined sequences, whereas small-scale fan delta, rhombus-shaped lacustrine deposit and lobe-shaped braided delta systems inherited tectono-sedimentary architectures in the high-angle fault confined sequences.