Jurassic Research Articles

Paleoclimate-induced wildfires in a paleomire in the Ordos Basin, Northern China during the Middle Jurassic greenhouse period

Paleo-wildfires are of great significance in the study of paleomire ecosystems. The products of such fires preserved in paleomires can provide detailed information for the reconstruction of wildfire regimes. This study analyzed the distribution of charcoal and aromatic biomarkers in a coal seam from the Middle Jurassic Yan'an Formation in the Ordos Basin, China. The results showed very high content of pyrogenic inertinite (38%–62%) and common occurrence of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in the studied coal seam, suggesting that wildfires occurred frequently during the period of peat accumulation. The mean reflectance of pyrogenic inertinite (1.50%) in all samples indicates a dominance of low-temperature wildfires in the paleomire, which is also supported by the high abundance of 2- to 3-ring PAHs. Furthermore, the common observations of high-reflectance pyrogenic inertinite (∼ 4.47%RIo) and 4- to 6-ring PAHs suggest the repeated occurrence of high-temperature wildfires. Various parameters of 3- to 4-ring PAHs indicate a relatively high proportion of charred material contributing to the organic matter in the paleomire. The dimethylphenanthrene ratios of the studied samples were inconsistent with those of modern experimental results, which can be probably attributed to the non-analogous vegetation composition in the Jurassic paleomire, and caution should thus be exercised when applying dimethylphenanthrene ratios to ancient sediments. The ratio of retene to 3-ring PAHs implies the contribution of conifers to the fires in the paleomire. The pyrogenic PAHs originated from both, combustion residues and smokes produced by in situ and local wildfires. The high O2 level during the Middle Jurassic promoted the frequent occurrence of wildfires in the studied paleomire. In addition, the occurrence of wildfires was collectively affected by the wet/humid climates, seasonality, and depositional environment.

Primary and secondary sedimentary processes in debris-flow-dominated alluvial fan deposits within karstic setting: An example from the Middle Atlas-Sais foreland basin transition zone, Morocco

The transition between the Middle Atlas and the Sais Basin contains a sequence of alluvial fans from the Plio-Quaternary period. These fans are mostly made up of debrites and are found resting unconformably on top of carbonate beds from the Jurassic Period. This location provides a key case study for investigating the primary processes of aggradation, as well as the secondary processes that alter alluvial fan deposits. Alluvial fans are developed through primary processes that occur intermittently over time, resulting in both active and inactive sectors. Internal and external organization of the deposits is, however, partially influenced by secondary processes that can cause mechanical, chemical, and/or biochemical changes, making the comprehension of alluvial fan development processes more complex. In this study, we investigated fan development processes by examining five lithostratigraphic logs and seven sedimentary facies in eight alluvial fans that have merged together. The findings indicate that debris flows were the main driver of fan development, with some contribution from sheet floods and mud-flows. In addition, the study suggests that secondary processes, including mechanical, chemical, biochemical, and diagenetic processes, have had a substantial impact on sediment deposition. The mechanical processes include brittle deformation, incision, reworking, and desiccation. On the other hand, the chemical and/or biochemical processes are evidenced by paleosol and calcrete development, as well as cementation, micritization, dissolution, development of porosity, oxidation, recrystallization, epigenesis, and neoformation. These processes would have been influenced by hydrological, hydrogeological and karstic factors, which are closely linked to the generally semi-arid climatic conditions punctuated by wet phases.

Turtle tracks from the middle Jurassic Yaopo formation in Beijing, China

ABSTRACT This study introduces new discoveries of fossil footprints from the Middle Jurassic Yaopo Formation in Beijing, China, marking the first reptile fossils that have been discovered in this formation. The two small footprints with parallel digits and drag marks suggest they were made by tetrapods moving through water. While there are similarities to crocodylian and pterosaur tracks, the evaluation suggests that turtles are the most likely trace-makers. If correct, the Yaopo Formation footprints are likely made by xinjiangchelyids, given their dominance in Asian freshwater ecosystems during the Late Jurassic and their widespread distribution in Late Jurassic China. Sichuanchelyids, Bashuchelyidae, and Hongkongochelys are less likely candidates due to their limited temporal and geographical distribution. This finding adds to the growing body of evidence on the evolution and ecology of turtles in Asia during the Late Jurassic period. These new findings offer important insights into the behaviour and spatiotemporal occurrence of these ancient reptiles and expand our understanding of their role in prehistoric aquatic ecosystems.

Outline, phylogenetic and divergence times analyses of the genus Haploporus (Polyporales, Basidiomycota): two new species are proposed.

Haploporus species have a worldwide distribution and 27 species have been accepted. In this study, two new species, Haploporuscrystallinus and H.dextrinoideus, are proposed from South America, based on the molecular fragments (ITS, LSU and mtSSU) and morphological evidence. Molecular clock analysis was performed and the result suggests that the ancestor of Polyporales originated between the Late Jurassic and Early Cretaceous period, with a mean stem of 159.8 Mya [95% higher posterior density (HPD) of 142.4-184.1 Mya] and the genus Haploporus occurred at a mean stem of 108.3 Mya (95% HPD of 88.5-128.2 Mya). In addition, most species of the genus are diversified between 60.5 Mya and 1.8 Mya, during the Paleogene to Neogene. A key to the accepted species of the genus Haploporus is provided.

Is biodiversity promoted in rift-associated basins? Evidence from Middle Jurassic conifers from the Otlaltepec Formation in Puebla, Mexico

The Jurassic Period is an important moment in the origin and evolution of modern conifer lineages. They dominated most of the land plant communities, as reported in different high latitude floras worldwide. However, there have been few reports of Middle Jurassic conifers from low latitude regions of Western Laurasia, such as Mexico. Most data on the composition of these Jurassic Mexican floras come from other plant lineages that thrived in different rift-associated basins, like the Tlaxiaco Basin and the Ayuquila Basin. Here we describe six new fossil conifers from the Middle Jurassic Otlaltepec Formation, Puebla, Mexico. Based on morphological features, we identify the following genera: Brachyphyllum, Platycladium, Podocarpites, and Masculostrobus and propose two new species (Brachyphyllum dimorpha Morales-Toledo & Cevallos-Ferriz, sp. nov. and Platycladium mexicanum Morales-Toledo & Cevallos-Feriz, sp. nov.). The description of the first ovulate cone for the Middle Jurassic of Mexico is provided, as well as a conifer foliage of uncertain affinities. Based on the available data we discuss the implications of the fossil record from the Otlaltepec Formation in context of the break-up of Pangea and how the conifer diversity seems to be increased by the rifting process through separating plant communities in different basins. Finally, this work contributes to the knowledge of conifer diversity at low latitude floras from Western Laurasia during the Middle Jurassic.

Jurassic NLR: Conserved and dynamic evolutionary features of the atypically ancient immune receptor ZAR1.

Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors generally exhibit hallmarks of rapid evolution, even at the intraspecific level. We used iterative sequence similarity searches coupled with phylogenetic analyses to reconstruct the evolutionary history of HOPZ-ACTIVATED RESISTANCE1 (ZAR1), an atypically conserved NLR that traces its origin to early flowering plant lineages ∼220 to 150 million yrs ago (Jurassic period). We discovered 120 ZAR1 orthologs in 88 species, including the monocot Colocasia esculenta, the magnoliid Cinnamomum micranthum, and most eudicots, notably the Ranunculales species Aquilegia coerulea, which is outside the core eudicots. Ortholog sequence analyses revealed highly conserved features of ZAR1, including regions for pathogen effector recognition and cell death activation. We functionally reconstructed the cell death activity of ZAR1 and its partner receptor-like cytoplasmic kinase (RLCK) from distantly related plant species, experimentally validating the hypothesis that ZAR1 evolved to partner with RLCKs early in its evolution. In addition, ZAR1 acquired novel molecular features. In cassava (Manihot esculenta) and cotton (Gossypium spp.), ZAR1 carries a C-terminal thioredoxin-like domain, and in several taxa, ZAR1 duplicated into 2 paralog families, which underwent distinct evolutionary paths. ZAR1 stands out among angiosperm NLR genes for having experienced relatively limited duplication and expansion throughout its deep evolutionary history. Nonetheless, ZAR1 also gave rise to noncanonical NLRs with integrated domains and degenerated molecular features.

A new extinct conifer Brachyoxylon from the Middle Jurassic in southern China: Wood anatomy, leaf phenology and paleoclimate

The Jurassic System in the Sichuan Basin of eastern Asia is represented by the extensive development of massive thick red beds, mainly composed of purplish-red sandstones and mudstones. Abundant invertebrate and vertebrate fossils have been recovered from these Jurassic red beds. However, fossil woods are much less documented. Here, we describe fossil woods from the Middle Jurassic Shaximiao Formation at Qijiang of Chongqing City in southeastern Sichuan Basin, China, obtaining typical Brachyoxylon anatomy with mixed radial tracheid pitting and araucarioid cross-field pitting. Owing to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Brachyoxylon qijiangense Xie, Wang et Tian sp. nov. is recognized here. Based on the tree mean sensitivity and leaf retention time analysis, along with the comparison with other invertebrate and leaf fossils in the Shaximiao Formation, the new fossil woods bearing true growth rings with abundant, well-formed earlywood and extremely narrow latewood indicates that B. qijiangense sp. nov. was an evergreen tree growing in a warm and humid climate with mild seasonality during the Middle Jurassic in Qijiang, probably in a flooding-disturbed, streamside condition.

Tracing the evolution of the ZAR1 resistosome back to the Jurassic era.

Tracing the evolution of the ZAR1 resistosome back to the Jurassic era.

Revision of Jurassic Protobranch Bivalves from Gebel Maghara, northern Sinai, Egypt

AbstractThe Jurassic rocks of Gebel Maghara, northern Sinai, Egypt, contain a well-preserved and highly diverse macrobenthic fauna, dominated by bivalves. This fauna, particularly bivalves and gastropods, have received little attention in the last 100 years. In an attempt to provide a sound database on the marine bivalve diversity of Egypt during the Jurassic period, a first faunal group, the protobranch bivalves, is reviewed in detail. Sixteen taxa (three of them new), belonging to two orders, five families, and nine genera are systematically described and compared to closely related Jurassic taxa from various locations, particularly in Europe and India. New species are Nuculoma douvillei n. sp., N. sinaiensis n. sp., and Palaeoneilo aegyptiaca n. sp. In addition, Palaeonucula cuneiformis (J. de C. Sowerby), P. muensteri (Goldfuss), Dacryomya diana (d'Orbigny), D. lacryma (J. de. C. Sowerby), and Praesaccella juriana Cox are identified from Jurassic strata of Egypt for the first time. The younger records of the genus Palaeoneilo have not been accepted by some researchers, since almost all exhibit only limited features. The genus occurs with certainty in the Middle Jurassic (Bajocian‒Bathonian) rocks of Egypt, based on well-preserved external and internal characters. Similarly, Dacryomya and Ryderia from Bathonian‒Kimmeridgian rocks of Egypt are younger than previously recorded from other parts of the world. The identified genera have wide geographic ranges and have been reported from different faunal provinces, which suggests that latitudinal climate differences did not influence their distribution pattern to a great extent.UUID: https://zoobank.org/7f3a9185-d690-4563-bdc0-df1c8d42ec0d

Jurassic system stratigraphy at the Kamianka village. Part 1. The Kozhulinska formation

Introduction. Despite the active research of Jurassic system deposits of Donbas during the last two centuries the issue of their stratigraphy principles is still debatable. The authors` analysis of the available scientific material revealed a conflict between the normatively established requirement to rely on lithostratigraphy during the sediment research, and the fact that the existing common system relies on biostratigraphy. This contradiction could be solved by the study of lithostratigraphic units of the Donetsk Jurassic deposits. Therefore, the purpose of the article was to research the Kozhulinska formation, establish its composition and describe its main features. The Lower Jurassic deposits from the outcrops near the village of Kamyanka (Izyum district) were studied, since the studyable stratotypes of most of the Jurassic strata, which are well exposed in the studied area, are available in this area. Material and methods. The scientific search was based on the analysis of literature, results of previous drilling and mapping works, as well as own field, laboratory and analytical studies. Clay samples were taken from different stratigraphic levels of the formation and from different lithological varieties. Laboratory research was carried out in two directions: using an electron microscope and a spectrometer to detect the material composition of clays. A palynological analysis of these deposits was also carried out, namely, stratified deposits with the help of microphytofossils, including, for the first time, according to the orthostratigraphic group – dinocysts. Results and discussion. The results showed that the Kozhulinska formation was mainly represented by shaly clays (gray, dark gray, sometimes blue-gray) that contained relatively thin layers of sandstones. The main mass of clays consisted of hydromicas, with an insignificant content of montmorillonite, and an even smaller amount of kaolin. The layers of quartz sandstones cemented with clay material were separately traced along the strike. Paleontological remains in the clays of Kozhulinska formation were rare. Palynological groups are mainly represented by pollen and spores, as well as remains of dinophytes, green algae and acritarchs. According to paleoalgological analysis, the sediments of the Kozhulinska formation are dated for the first time. Stratigraphy. Kozhulinska formation is represented by a fairly uniform layer of montmorillonite clays of hydromica composition. The clays are mainly siltstone, but there are, especially in the lower part, washed clean varieties. It is impossible to divide the formation into sub formation based on lithological features. According to biostratigraphic data, deposits are divided into Plinsbachian, Toarian and Aalenian. Paleogeography. At the end of the Early Jurassic and the beginning of the Middle Jurassic era, the territory of the Kamianska area was a low-lying part of the seabed that was drained during low tides. The land that surrounded it was also low-lying and almost did not supply detrital material, however, there is a regular removal of plant detritus. The source of the terrigenous material was the sedimentary complexes of the Donetsk Ridge. Features of the chemical composition of the world are a significant amount of iron (siderite, ocher, chamosite) and the absence of calcium and magnesium carbonates. At the end of the early Aalene, this unstable basin finally regresses, which leads to the accumulation of a powerful subaerial pack of sandstones, which weigh and border the cores of anticlines - elevated areas of the bottom or small islands.

Sedimentary Evolution and Geological Characteristics of the Jurassic in the South Qiangtang Basin, China

Based on the analysis of lithology, lithofacies combinations, sedimentary structures, and fossil types in five geological sections measured through fieldwork, this paper comprehensively elucidates the sedimentary evolution characteristics of the Jurassic period in the South Qiangtang area. The South Qiangtang Basin is renowned for preserving the most complete Jurassic marine sedimentary strata in China, and it primarily consists of a mixed platform environment of carbonate and clastic rocks. The Jurassic strata in the South Qiangtang Basin range from the Quse Formation at the base to the Suowa Formation at the summit, with sedimentary facies evolving from the outer shelf to the subtidal zone, and seawater depth gradually becoming shallower. This trend may be associated with the division and expansion of the Bangong–Nujiang suture zone during the Late Triassic, subduction in the Middle Jurassic, and the suture and splicing of the Qiangtang–Lhasa plate during the Late Jurassic tectonic movements. In conclusion, this research presents a comprehensive analysis of the sedimentary evolution of the Jurassic period in the South Qiangtang Basin for the first time. The findings offer significant contributions to the understanding of the region’s geological history and serve as a valuable foundation for future investigations.

Petrogenesis of Shihuiyao Rare-Metal Granites in the Southern Great Xing’an Range, NE China

Shihuiyao Rb–Nb–Ta-rich granites from the Late Jurassic period are newly discovered rare-metal-bearing granites found in the southern Great Xing’an Range, NE China. Further research of these granites may contribute to better understanding the petrogenesis of rare-metal granites and their associated mineralization mechanisms. The granites are high-silica (SiO2 = 73.66–77.08 wt%), alkali-rich (K2O + Na2O = 8.18–9.49 wt%) and weakly to mildly peraluminous with A/CNK values (molar ratios of Al2O3/(CaO + Na2O + K2O)) ranging from 1.06 to 1.16. High differentiation indexes (DI = 95–97) and low P2O5 contents demonstrate that Shihuiyao rocks are low-P and peraluminous rare-metal granites. Mineral chemistry and whole-rock geochemistry can be used to obtain the following lithological sequence: zinnwaldite granite, muscovite–zinnwaldite granite, amazonite-bearing granite and amazonite pegmatite. The effect of the rare-earth element tetrad; low K/Rb (18.98–32.82), Nb/Ta (2.41–4.64) and Zr/Hf (5.99–8.80) ratios; and the occurrence of snowball-textured quartz suggest that extreme magmatic fractionation might be the key factor that causes Rb–Nb–Ta enrichment.

Quantifying the Impact of Coal Mining on Underground Water in Arid and Semi-Arid Area: A Case Study of the New Shanghai No. 1 Coal Mine, Ordos Basin, China

The new Shanghai No. 1 Coal Mine is located in arid and semiarid area of northwest China, which is characterized by scarce rainfall, intense evaporation, and limited water resources. High-intensity coal mining has caused severe damage to groundwater resources. The Baotashan sandstone aquifer of the Jurassic system has abundant water resources, and they are stored in the floor strata of mining coal seams. This poses the risk of high-pressure build-up and water inrush hazards during the mining of coal. To avoid these, the Baotashan sandstone aquifer needs to be drained and depressurized, which can result in a huge waste of water resources. Thus, taking the New Shanghai No. 1 Coal Mine as the basis for the case study, the impact of coal mining on the underground water resources was quantified. Large-scale water release tests were performed under the shaft to determine the hydrogeological properties of the Baotashan sandstone aquifer and a three-dimensional numerical model of the groundwater system was established. The dynamic phenomenon of water drainage was simulated and the drained water discharge was predicted under the condition of safe mining.

Characteristics and genesis of reef-bank complexes in deep shelf facies: A case study of the Middle-Late Jurassic in the northern Amu Darya Basin, Central Asia

A large-rimmed carbonate platform was developed in the Amu Darya Basin during the Middle-Late Jurassic Callovian-Oxfordian period. What distinguishes it from typical carbonate platforms is that a series of reef-bank complexes had extensively developed in the deep shelf depositional zone of the basin. However, only a few studies have reported on the classification, characteristics, and genesis of these reef-bank complexes in relatively deep water, greatly limiting the development of deep-water carbonate sedimentology. To address this issue, the types and the genesis of reef-bank complexes in the deep shelf environment have been clarified based on the systematic petrography, seismic sedimentology, and geomorphology study of the Callovian-Oxfordian carbonate rocks in the northern Amu Darya Basin during the Middle-Late Jurassic period. The results find that the reef-bank complexes are widely distributed in the deep shelf environment in the study area with laminar, reticulated, and zonal distributions. The reef-bank complexes include barrier-bonding reef-bank complexes, lime-mud mounds (LMMs), and granular shoals (GSs). The deep shelf environment can be further divided into an inner shelf, shelf margin, and shelf slope. The inner shelf and shelf margin have a relatively shallow water body and a strong sedimentary hydrodynamic force, mainly developing reticulated reef-bank complexes and laminar GSs, whereas the shelf slope mostly develops zonal LMM deposits in strips. The scale of the reef-bank complexes is mainly controlled by basement paleogeomorphology and water energy. Relatively high-energy reef-bank complex bodies are developed on the seaward side of the paleouplift limb with relatively turbulent hydrodynamic conditions, whereas low-energy LMMs are mostly developed on the high position of paleouplift and landward side. The obtained findings can deepen our understanding of relatively deep-water carbonate sedimentation and enrich the carbonate sedimentation theory.

Igneous Records of Mongolia–Okhotsk Ocean Subduction: Evidence from Granitoids in the Greater Khingan Mountains

Large-scale Mesozoic granitoids are exposed in the Greater Khingan Mountains. Their relationship with the Mongolia–Okhotsk and the Paleo-Pacific Ocean is still under discussion and a matter of debate. In this study, field observations were made and a total of 18 granitoids exposed in the vicinity of the Heihe–Baishilazi area in the northern part of the Greater Khingan Mountains were sampled for petrological, geochronological, and geochemical research. In addition, to complement this study, 90 granitic samples from the Xinghua, Dajinshan, Yili, Chabaqi, and Sankuanggou areas in the Greater Khingan Mountains were compiled in order to reveal rock assemblages, magma sources, and then inquire into the tectonic background. Zircon LA–ICP–MS U–Pb dating indicates that two samples from the Heihe area were formed in the Early Jurassic period (194.2 ± 1.4 Ma and 183.1 ± 1.3 Ma), and the εHf(t) values and TDM2 of the zircons were mainly +5.8 to +10.7 and 528 Ma to 834 Ma, respectively, with a large variation range. The intrusive rocks from the Greater Khingan Mountains (108 in total) belonging to the T1T2G1G2 assemblage contained tonalites (T1), trondhjemites (T2), granodiorites (G1), and granites (G2). These granitoids are presented as subalkaline series in a plot of total alkali versus SiO2 (TAS diagram), medium-K calc-alkaline and high-K calc-alkaline series on SiO2 versus K2O diagram, with metaluminous to peraluminous characteristics on an A/CNK versus A/NK diagram. These are shown as a MA (magnesium andesite) series and LMA (lower (or non) magnesium andesite) series on a SiO2 versus MgO diagram, which can be further divided into the higher-pressure TTG subtype of the MA (corresponding to high-SiO2 adakite (HSA)) series and the lower-pressure TTG subtype of LMA (corresponding to typical calc-alkaline suprasubduction zone rocks). In addition, granitoids were enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high-field-strength elements (HFSEs), corroborating a suprasubduction zone environment. Regional correlations as well as geochemical characteristics indicate that the rocks from the Greater Khingan Mountains formed in a subduction zone environment during the Early Jurassic; primary magma had presumably originated from the melting of young and hot oceanic crust under eclogite to amphibolite facies conditions. According to the spatial variation in rock assemblages (T1T2G1 to G1G2 and G2), we speculate that the northeastern Heihe, Baishilazi, and Xinghua areas as well as the westward Dajinshan area were adjacent to the ocean and formed an outer subduction zone, whereas the southwestward Sankuanggou, Yili, and Chabaqi areas were adjacent to the continent, forming an inner subduction zone. The distribution sites of the inner and outer subduction zones indicate southward and southwestward ocean subduction. Therefore, we propose a direct connection with southward subduction of the Mongolia–Okhotsk Ocean.

Study on the influence of key active groups on gas products in spontaneous combustion of coal

In order to reveal the internal relationship between the active groups and gas products in spontaneous combustion of coal, the correlation between the content of active functional groups and the production of gas products was studied by temperature programmed experiment and in situ infrared spectroscopy analysis experiment. The results show that there are three characteristic temperature points in the gas release curve of Jurassic coal spontaneous combustion in northern Shaanxi, which can be divided into slow oxidation stage, critical temperature stage, rapid oxidation reaction stage and combustion stage. CH3, CH2, C–H and OH are actively consumed in the spontaneous combustion of coal. CO gradually increased, which is an important oxidation product during Jurassic coal oxidation in northern Shaanxi. The chain length CH2/CH3 is attacked and the fracture shortened, while the oxygen enrichment degree of CO/CC in coal increases gradually. The correlation values of key active groups of CH3, CH2, C–H, OH, CO, CH2/CH3, and CO/CC with oxygen, carbon and oxygen gases and alkane and olefin gases in the process of coal oxidation heating in different coal seams in northern Shaanxi during Jurassic period are obtained. The results show that CH3, CH2 and CH2/CH3, are the main parts of oxygen molecules attacking and binding in the Jurassic coal oxidation process in northern Shaanxi, and the oxygen-rich products of coal decompose into carbon oxygen gas and alkane alkene gas. Due to the different activation energies of various active groups, the spontaneous combustion of coal shows different reaction degrees in each stage. The research results can be used to understand the occurrence and development degree of spontaneous coal combustion, and have important guiding significance for the monitoring and warning of spontaneous coal combustion and the targeted prevention and control of spontaneous coal combustion disasters.

THE EFFECT OF ANCIENT GEOLOGICAL PERIODS IN BIOLOGY

At the end of the 19th century and the beginning of the 20th century, extensive works began in the world for the construction of railways, and for these works, the previous biography of land is necessary. William Smith was the first scientist. The rocks found in the Somerset region from the lower layers of the earth and belong to the Jurassic period (20–144 million years ago). He compared the rocks of the coastal areas of the northern seas and using these rocks, he drew a map of the past periods of the earth in England. Even so far, the stones that came from the lower layers of the earth represented its place, that is, by using those stones, William Smith not only made a map of the past of the earth, but also a map of the lower layers of the earth. This map has a special place in the knowledge of modern geology it helps us to create a table of the past periods. From the information contained in this map, we can see the underground layers and their contents, iron, coal, etc. even if it is in the middle of the ocean. Fossils are very valuable to us. By using fossils, humans can identify the living creatures of the past times and get to know their ways of life. It can also be done by using fossils to divide the age table of the earth into cycles first and then the cycles are divided into periods. For this reason, the previous age table is first divided into periods and then the periods are divided into periods. 1. Upper Carboniferous Period; 2. Lower Carboniferous Period; 3. Middle Jurassic Period; 4. Jurassic Period and 5. Triassic Period. Keywords: Period, fossils, Evolutionary modeling, extinction, Biodiversity and organisms.

Sedimentary Filling Evolution under Paleoclimate Transition—A Case Study from the Middle Jurassic Zhiluo Formation, Ordos Basin

Under a specific tectonic background, the change in paleoclimate can show different facies associations and depositional architecture. The Jurassic China continent was an important region for transforming the Paleotethys tectonic domain to the circum-Pacific tectonic domain, and its paleoclimate information was entirely preserved in the continental sedimentary successions. The Middle Jurassic Zhiluo Formation, in the Ordos Basin, was at just the critical period of paleostructure and paleoclimate transition, preserving considerable sedimentological evidence; however, little sedimentological research has been conducted under the transition. This study reconstructed the sedimentary filling characteristics of the Zhiluo Formation under paleoclimate transition based on field outcrop survey, thin section observation, geochemical indices, stratigraphic correlation, and depositional environment analysis. The results showed that with the paleoclimate change from warm and humid to hot and arid, the sedimentary facies of the Zhiluo Formation were characterised by the change from the braided river/braided river delta in the J2z1-1 sedimentary period to the meandering river/meandering river delta in the J2z1-2 sedimentary period, and finally the change to the meandering river, meandering river delta, and lacustrine in the J2z2 sedimentary period. The combined action of the southern super monsoon effect, the increasing global CO2 concentrations, the moving southward of the East Asian block, and the terrain elevation difference, changed the basin’s climate from warm and humid to hot and semi-arid/arid. This study provides a crucial basis for reconstructing the interplay between paleoclimate and paleotectonics, and guiding sedimentology and paleoenvironment research on East Asia during the Middle Jurassic period.

Magmatic evolution of the Calc-alkaline Middle Jurassic igneous rocks in the eastern pontides, NE Turkey: insights from geochemistry, whole-rock Sr-Nd-Pb, in situ zircon Lu-Hf isotopes, and U-Pb geochronology

ABSTRACT The Eastern Pontides in NE Turkey hosts a very limited number of plutonic rocks from the Jurassic period. Here we submit new geochemical, Sr-Nd-Pb and zircon Lu-Hf isotope data, and zircon U-Pb ages for plutonic rocks in this region. Zircon U-Pb dating for the Alemdar and Işıkdere plutons yielded an age of 175–170 Ma (Middle Jurassic). The Alemdar and Işıkdere plutons have I-type, medium to high-K calc-alkaline series, and metaluminous to slightly peraluminous characteristics. On PM-normalized diagrams, the plutons are enriched in large-ion lithophile elements (LILEs) with pronounced depletion of high field strength elements (HFSEs, Ta, Nb, Ti). Chondrite-normalized plots for the plutons show variable enrichment in light rare earth elements (LREEs) with depletion of heavy rare earth elements (HREEs). The rocks of the Alemdar Pluton have homogeneous ISr values (0.70585 to 0.70673), low εNd(i) values (−3.9 to −1.6), pozitif εHf(i) values (+3.3 to +9.1), and Hf single-stage model ages (563–712 Ma), whereas those of Işıkdere have high ISr values (0.70666 to 0.70673), low εNd(i) values (−3.9 to −3.8), εHf(i) values (−3.1 to +1.1), and Hf single-stage model ages (791–969 Ma). These values imply that they have different sources. These results suggest that the magma of the Alemdar was formed by the partial melting of a relatively depleted lithospheric mantle wedge interaction of the OIB-like melts, while those of Işıkdere have derived from the partial melting of an enriched mantle metasomatized by slab-derived sediments and then modified by fractional crystallization and crustal contamination in crustal magma chambers. Considering the available data, we conclude that the studied plutons were related to extensional tectonic events during the Middle Jurassic in response to the roll-back of the Paleotethys oceanic slab in the final stage of oceanic closure. These rocks are an example of the formation of deep subduction products following Early Jurassic subduction.

Tropical Arctic

Tropical Arctic asks us to imagine the Arctic as a lush, green paradise (think Miami) through the story of an expedition to Greenland and the subsequent analysis of the fossils collected there by a team including an artist, botanist, and paleobotanist. The expedition team was specifically interested in a mass extinction event that occurred during a period of catastrophic climate change 200 million years ago between the Triassic and Jurassic periods. The team targeted particular fossil beds to help them find the answers they were looking for. They collected more than a metric ton of fossils and used the data to put together a picture of what the ancient Arctic ecosystem looked like by determining which plants were dominant and which were rare both before and after the mass extinction. They then used the fossils to create three-dimensional models to increase their understanding of the plant characteristics. This provided insight into which plants were resilient in the face of change and which characteristics might have contributed to that resilience. The team coupled this evidence with laboratory evidence on extant plants that measured their response to conditions similar to ancient Earth’s.What was a dense forest canopy in the Triassic transitioned to lower-growing plants that had to survive harsh atmospheric conditions in addition to frequent fire in the early Jurassic. When conditions stabilized, those plants able to survive could thrive. The team hypothesized that the slow rate of change of Earth’s conditions contributed to the plants’ ability to migrate, essentially germinating where conditions were favorable. Certain species were better adapted for conditions on one side of the boundary. The book ends with lessons for the future, pinpointing the magnitude of temperature change associated with a reduction in biodiversity and loss of species and what it might mean for Earth’s future.While the photographs and illustrations are beautiful, I found the story hard to follow. At the end of the book, I wished some of the information presented in Chapter 4 had been presented earlier. I was less motivated to learn about the expedition and all of the fossils collected because I didn’t know the story of the conditions on Earth that led to and followed the mass extinction. Had that context come first, it would have provided framing for the expedition, sparking curiosity about what the team found. I found myself wanting a map or a timeline to help me track Earth’s history both spatially and temporally.It may be beyond the scope of this book, but I was left wondering about the conditions in the Arctic that allowed all that plant life to grow in the first place. How does the 40,000-year cyclical change in the Earth’s tilt play into the story of energy and matter in the Arctic? Does that explain why it was lush there once but cold and icy there now? And how will the anthropogenic changes we have made to Earth’s system interact with that natural cycle?Today, many high school biology teachers are tasked with integrating Earth and space science standards into their curricula. Using historical events that caused changes to Earth’s system as phenomena can help students understand the flow of energy and matter and provide a context for understanding why the mechanisms of photosynthesis and cellular respiration are so important. Tropical Arctic is a beautiful text and illuminates a part of Earth’s history that I knew little about. On its own, it is missing necessary pieces to spark the interest of someone who lacks expertise in the field, but it would be a worthwhile complement to other texts on the topic.