Description: The population structure of the California market squid Loligo opalescens was studied for the Channel Islands region off Southern California between June 1998 and March 2000. During this time Californian waters were exposed to an extraordinary El Niño event that was possibly the most dramatic change in oceanographic conditions that occurred last century. There was then a rapid transition to record cool La Niña conditions. Statolith increments were used to determine age parameters and increment periodicity was validated for the first 54 days of life. Based on statolith increment counts, the oldest males and females were 257 and 225 days respectively and individuals matured as young as 129 and 137 days respectively. No distinct hatching period was detected. There was a general trend of increasing body size throughout the study period. Squid that hatched and grew through the El Niño were strikingly smaller and had slower growth rates compared to squid that grew through the La Niña. This was related to oceanography and associated productivity. There was a positive correlation between squid mantle length and upwelling index and a negative correlation between mantle length and sea temperature. The 'live-fast die-young' life history strategy of squid makes them ideal candidates for following the effects of the dramatic changes in oceanographic conditions off California. We propose that squid can serve as ecosystem recorders and productivity integrators over time and space and are useful organisms to tie oceanography to biology.

Description: The Iapetus Ocean opened during the fission of the supercontinent Rodinia, from the breakup of three of its core continental constituents: Laurentia, Baltica and Amazonia. The timing of Iapetus opening is still much debated, with estimates ranging from 700 to 550 Ma. Similarly debated is exactly how Laurentia, Baltica and Amazonia were positioned relative to each other immediately before their breakup. In this study, we reconsider the timing and framework of Iapetus opening by integrating the fragmentary mid-Neoproterozoic to early Cambrian observational records from these continents. We first demonstrate that paleomagnetic data, despite being both sparse and probably contaminated by some global-scale, non-uniformitarian process in Ediacaran time, support the existence of a wide ocean between these continents by 575 Ma. However, the paleomagnetic data alone are insufficient to allow the formulation of more specific conclusions concerning the timing and paleogeography of Iapetus opening. We therefore conduct an extensive review of the mid-Neoproterozoic to Cambrian geology of eastern Laurentia, western Baltica and western Amazonia which, jointly interpreted with the paleomagnetic constraints, allow us to construct a self-consistent and geodynamically feasible plate tectonic model. In this model, the breakup of Laurentia, Baltica and Amazonia was polyphase, involving the spalling of multiple marginal terranes from Laurentia and the successive opening of several oceans, including a composite ‘Iapetus Ocean’. The first phase of continental breakup occurred between eastern Laurentia and western Amazonia at 750–700 Ma, leading to the opening of the Puncoviscana Ocean. This was followed by the opening of the eastern branch of the Iapetus Ocean, between Laurentia and Baltica, at ~590 Ma, which may have been instigated by emplacement of the Central Iapetus Magmatic Province. The western branch of Iapetus subsequently opened at ~550 Ma by the detachment of marginal terranes from eastern Laurentia, following a protracted phase of rifting. We contend that our preferred scenario is the simplest solution given the presently available evidence but throughout this review we underline key outstanding questions and the attendant uncertainties in our preferred model.

Description: Most hotspots, kimberlites, and large igneous provinces (LIPs) are sourced by plumes that rise from the margins of two large low shear-wave velocity provinces in the lowermost mantle. These thermochemical provinces have likely been quasi-stable for hundreds of millions, perhaps billions of years, and plume heads rise through the mantle in about 30 Myr or less. LIPs provide a direct link between the deep Earth and the atmosphere but environmental consequences depend on both their volumes and the composition of the crustal rocks they are emplaced through. LIP activity can alter the plate tectonic setting by creating and modifying plate boundaries and hence changing the paleogeography and its long-term forcing on climate. Extensive blankets of LIP-lava on the Earth’s surface can also enhance silicate weathering and potentially lead to CO2 drawdown (cooling), but we find no clear relationship between LIPs and post-emplacement variation in atmospheric CO2 proxies on very long (〉10 Myrs) time-scales. Subduction is a key driving force behind plate tectonics but also a key driver for the long-term climate evolution through arc volcanism and degassing of CO2. Subduction fluxes derived from full-plate models provide a powerful way of estimating plate tectonic CO2 degassing (sourcing) and correlate well with zircon age frequency distributions through time. This suggest that continental arc activity may have played an important role in regulating long-term climate change (greenhouse vs. icehouse conditions) but only the Permo-Carboniferous icehouse (~330-275 Ma) show a clear correlation with the zircon record.