Chapter 12 - Influence of Large Igneous Provinces

Abstract

Owing to their large volume (up to millions of km3) and short duration of emplacement (often less than a few million years) Large Igneous Provinces (LIPs) and associated Silicic LIPs (SLIPs) can have a dramatic effect on global environments. Postulated effects include warming, cooling, acid rain and ocean acidification, ozone depletion and increased UV-B radiation, marine anoxia, mercury poisoning, and sea level changes, many of which are evidenced by, for example, stable isotopic excursions and changes in sedimentary composition (e.g., black shales). Major environmental changes linked to LIPs have resulted in biotic crises, including several mass extinctions. With increasing precision of U–Pb dating of LIPs resulting in age uncertainties that can be of <50,000 years, an increasing number of Phanerozoic chronostratigraphic boundaries that mark biotic crises can be correlated with LIP events. This relationship extends into the Precambrian, for which existing chronostratigraphic boundaries are represented by approximate numbers (mostly rounded to the nearest 100Myr). We propose that specific LIPs should define these boundaries. The context is that while LIPs have a regional magmatic extent (often more than 1Mkm3 in volume) their often major, global environmental effects are preserved in sedimentary archives. Thus LIPs are not “golden spikes” in themselves, but their sedimentary signatures are potential proxies for golden spikes in the sedimentary record. There is a need for a more integrated and detailed correlation of LIPs and sedimentary records in order to (1) identify LIPs with significant environmental effects, as well as those with only minor or even no recognizable environmental effects, and (2) lead to a full evaluation of the causal relationship between LIPs and sudden environmental change in comparison with other drivers of sudden change such as bolide impact, orogenic weathering, and biological evolution. Key to this progress is expanded high-precision dating of LIPs and the identification and analysis of time-correlative portions of the sedimentary record.