The early–middle Cambrian (Fortunian to Age 4) is characterized by a significant increase in metazoan diversification. Furthermore, this interval is marked by a prominent environmental and ecological expansion of arthropod- and echinoderm-rich biotas. Recent redox work has suggested that this shift occurred during stable or decreasing marine oxygen...

The radiation of angiosperm lineages during the Cretaceous Period (145.5–65.5 Ma) initiated one of the greatest floral turnovers to have occurred on our planet. Much of our understanding of the floral biology and diversity of these early angiosperms derives from exceptionally preserved charcoalified and coalified Cretaceous fossil floras. Although...

The use of volatile-bearing (H2O-Cl-F-C-S) minerals as proxies for constraining the volatile content of lunar magmas remains controversial. In this study, we apply published F-Cl-S signature trends in apatite from lunar mare basalts, new experimentally determined apatitemelt partition coefficients for S, and thermodynamic modeling to demonstrate...

In recent years ophiolitic diamonds have been reported mostly from podiform chromitites. However, the mechanism of such diamond formation remains unknown. We report in situ diamond, graphite pseudomorphs after diamond crystals, and hydrocarbon (C-H) and hydrogen (H2) fluid inclusions in ultrahigh-pressure (UHP) peridotitic minerals of the Nidar...

The flow dynamics of magmas is controlled by several parameters, including magma rheology, density, surface tension, gas and liquid flow rate, and the geometry of the flow field, which is mainly regulated by the conduit shape. For this reason, magmatic flows along fissures and dikes are significantly different from those along axisymmetric conduits....

The Earth's climate cooled through the Ordovician Period leading up to the Hirnantian glaciation. Increased weatherability of silicate rocks associated with topography generated on the Appalachian margin during the Taconic orogeny has been proposed as a mechanism for Ordovician cooling. However, paleogeographic reconstructions typically place the...