The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth’s atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning the link between biological evolution and contemporaneous changes in the oceanic environment. In this study, integrated δ13Ccarb–δ13Corg–δ15N compositions were analysed from the YD-4 core samples to understand redox fluctuations and nitrogen cycling of the middle Yangtze Block across the E-C transition. Two negative δ13Ccarb excursions (N1 and N2) and a positive δ13Ccarb excursion (P1) are identified from the studied samples and are supposedly of primary origin. Constrained by of the U-Pb age, biolithology and pattern of isotopic variation, N1, P1 and N2 are comparable to the Basal Cambrian Carbon Isotope Excursion (BACE), Zhujiaqing Carbon Isotope Excursion (ZHUCE) and Shiyantou Carbon Isotope Excursion (SHICE). We interpreted the decreased δ15N values in this study as resulting from intensified atmospheric nitrogen fixation driven by enhanced denitrification associated with expanded marine anoxia, as well as partial ammonium assimilation, while increased δ15N values suggest weakened denitrification associated with an amplified oxic water mass. The temporal coincidence of N1 and N2, with two episodes of negative δ15N excursions, and of P1, with a positive δ15N excursion, suggests that variable oceanic redox conditions and nitrogen bioavailability may have influenced the evolution of the Cambrian eukaryote-dominated community.

Although the Rhætic beds are not exposed continuously along the eastern boundary of the Keuper outcrop, they have been proved at many points from the River Trent in the north on the Nottinghamshire border to Glen Parva in the south. South of this point there is so much drift, and borings within the Liassic outcrop have been so isolated or shallow, that there is a gap in our knowledge of the intervening ground between the last point and the Rugby district. The Countesthorpe boring, carried to a depth of over 600 feet, encountered Upper Keuper beneath the Drift, with no intervening Rhætics. Commencing in the north in the Gotham district the two outliers are capped above the Red Marl and Tea-green Marl with Rhætic beds, and Lower Lias Limestone (Ps. planorbe zone) above. At Ash Spinney at the south end of the southern outlier, and at the east end of Crownend Wood, Black Shales with Avicula contorta crop out; and on the west side septaria are seen. On the north-west side of the northern outlier at Cottager's Hill Protocardium phillipianum has been found in a well-section near the lane. Rhætic shales are seen in the shafts driven for gypsum works about Gotham.

With the removal of certain genera the Illaenidae has become a very homogeneous family. Attempts have been made to group genera into subfamilies, the most important of which was that made by Salter in 1867, but these efforts have not met with general approval. Thus Warburg (1925, pp. 97–100) has given a recent summary of the Illaenid classification and discussed the previous literature, and this author endorses the opinion expressed by Raymond in 1916, “that it is still too early to make any natural classification.” Whittard (1938, p. 89) follows Holm and Warburg and meantime would only admit Illaenus and Bumastus as valid genera and suggests that Salter’s genus Ectillaenus might be retained for species of Illaenids in which visual organs were either absent or vestigial.

The subject of denudation is so important that I propose giving a few instances of denudation and of the transport of material that have actually come under my own observation or that of my friends. Where one sees the same familiar crags and pinnacles year after year, apparently quite unchanged, one may perchance fancy that denudation is at a standstill; but anyone who, in scrambling across the screes that clothe many a steep hillside, finds them moving beneath his feet, or perhaps has clattering about his ears a shower of stones dislodged by some wandering sheep, will at once perceive that it is not so: for it is obvious that if the mere tread of such a small beast as a sheep, shepherd or other pedestrian, can set scree rolling downhill, it must be in a very unstable state, and may be expected to move in a conspicuous manner under more potent forces than the tread of animals. Observation shows that this is the case. Not a year passes without some conspicuous fall of scree or of solid rock, owing chiefly to great downpours of rain. Leaving general statements, I will now give actual instances of the fall of rock or movement of scree that have recently taken place in the Snowdon district.

These Foraminifera were obtained from fifteen zones of the Jurassic strata, between Solothurn, in Switzerland, and the Eichberg, in Baden: three Liassic zones (Black or Lower Jura); six in the Brown or Middle Jura; and six in the White or Upper Jura; beginning with the Turneri-zone of the Lower Lias, and ending with the Pteraspis-zone of Schaffhausen. The Numismalis marl, Amalthei-clay, Murchisonæ-bed, Discoidei-marl, Crenularis-bed, the Coral-limestone, and the Virgulian stage yielded few or no traces of Foraminifera.

Several major tholeiitic (e.g. the Skaergaard intrusion) and alkaline (e.g. the Kangerlussuaq Syenite) intrusive complexes of the North Atlantic Large Igneous Province are exposed along the Kangerlussuaq Fjord in East Greenland. The Kærven Complex forms a satellite intrusion to the Kangerlussuaq Syenite and includes early tholeiitic gabbros and a series of cross-cutting alkaline intrusions ranging from monzonite to alkali granite. The alkaline intrusions cut the gabbros, and are cut by the outer nordmarkite zone of the Kangerlussuaq Syenite. This study presents the first U–Pb zircon ages from the alkaline units of the Kærven Complex. Fourteen multi-grain zircon fractions have been analysed by thermal ionization mass spectrometry (TIMS). Absolute age differences could not be resolved between the different units, suggesting a relatively rapid succession of intrusions between c. 53.5 and 53.3 Ma. Our compilation of precise radiometric age data shows that most of the alkaline magmatism in the Kangerlussuaq Fjord occurred prior to 50 Ma. Moreover, pre-50 Ma alkaline intrusions and lavas show a SSE-younging trend, which is interpreted as the track of the Iceland hotspot during the rift-to-drift transition of the North Atlantic.

The Songling and Majiayu peridotite blocks occur in the Eastern Block, North China Craton (NCC). Geothermobarometry data show that the Songling peridotites began exhumation from a depth of c. 70 km (c. 23 kbar). During exhumation, the Songling peridotites were intruded by an upper-crust-derived, high-δ18O (up to +7.28‰ in zircon) trondhjemitic dyke at 2.47 Ga and experienced granulite-facies metamorphism. The Songling peridotites have hybrid mantle wedge (HMW) -like high SiO2 (> 45 wt%), high FeOt (c. 10 wt%) content, high modal orthopyroxene abundance (> 35%) and high ϵNd(t) (+18.4 to +21.4), which were generated by the reaction between peridotite and eclogite-derived melts. The clinopyroxenes from the Songling peridotites were in equilibrium with a Nb-, Zr- and Ti-depleted arc-like magma. The Majiayu peridotites are characterized by depletion of Nb, Zr and Hf and are highly enriched in FeOt, Th and light rare earth elements (LREEs), which can be interpreted as an open system reaction between hydrous melts and fore-arc mantle peridotites. These two peridotite blocks are considered to be arc-related mantle peridotites that experienced melt extraction and metasomatism in different styles. They were exhumed to the north margin of the North China Craton during the c. 2.47 Ga arc–continent collision along the Zunhua structural belt.