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The term Anthropocene, proposed and increasingly employed to denote the current interval of anthropogenic global environmental change, may be discussed on stratigraphic grounds. A case can be made for its consideration as a formal epoch in that, since the start of the Industrial Revolution, Earth has endured changes sufficient to leave a global stratigraphic signature distinct from that of the Holocene or of previous Pleistocene interglacial phases, encompassing novel biotic, sedimentary, and geochemical change. These changes, although likely only in their initial phases, are sufficiently distinct and robustly established for suggestions of a Holocene-Anthropocene boundary in the recent historical past to be geologically reasonable. The boundary may be defined either via Global Stratigraphic Section and Point ("golden spike") locations or by adopting a numerical date. Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. This datum, from the perspective of the far future, will most probably approximate a distinctive stratigraphic boundary.

Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium than melts of peridotite. Olivine phenocrysts' compositions record these differences and were used to quantify the contributions of pyroxenite-derived melts in mid-ocean ridge basalts (10 to 30%), ocean island and continental basalts (many >60%), and komatiites (20 to 30%). These results imply involvement of 2 to 20% (up to 28%) of recycled crust in mantle melting.

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Accreted terranes, comprising a wide variety of Jurassic and Cretaceous igneous and sedimentary rocks, are an important and conspicuous feature of Cuban geology. Although the Mesozoic igneous rocks are generally poorly exposed and badly altered, we have collected and geochemically analyzed 25 samples that place new constraints on plate tectonic models of the Caribbean region. From our recognizance sampling, six main lava types have been identified within the Mesozoic igneous rocks of Cuba: rift basalts, oceanic tholeiites, backarc basin lavas, boninites, island arc tholeiites (IAT), and calc-alkaline lavas. We suggest that the rift-related basalts may have formed during the development of the proto-Caribbean, as the Yucatan block rifted away from northern South America in Jurassic-Early Cretaceous time. The Early Cretaceous oceanic tholeiites have flat rare earth element patterns, and are compositionally similar to Pacific mantle plume-derived oceanic plateaus of similar age. The Early Cretaceous arcrelated rocks are either backarc basalts, boninites, or relatively trace element-depleted IAT lavas. A limited amount of geochemical and field evidence hints that two parallel arc systems existed in the western proto-Caribbean area in Early Cretaceous time. This leads us to speculate that in the proto-Caribbean at this time there was a western arc with a northeast-dipping subduction zone erupting IAT lavas (with Farallon plate being consumed), and a more eastern boninitic arc with a southwest dipping subduction zone (with proto-Caribbean plate being consumed). This latter arc was relatively short lived and after being aborted was mostly eroded away. The Cretaceous primitive (IAT) arc survived and, later in Cretaceous time, as this arc system moved into the widening gap between North and South Americas, calc-alkaline lavas began to be erupted. The evidence suggests that the change from IAT to calc-alkaline lavas was gradual and not abrupt. These new data, although limited, provide geochemical constraints on the tectonic development of the northern part of the Caribbean plate. In consequence, we present a new plate tectonic model for this area of the Caribbean.

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The Anthropocene, an informal term used to signal the impact of collective human activity on biological, physical and chemical processes on the Earth system, is assessed using stratigraphic criteria. It is complex in time, space and process, and may be considered in terms of the scale, relative timing, duration and novelty of its various phenomena. The lithostratigraphic signal includes both direct components, such as urban constructions and man-made deposits, and indirect ones, such as sediment flux changes. Already widespread, these are producing a significant ‘event layer’, locally with considerable long-term preservation potential. Chemostratigraphic signals include new organic compounds, but are likely to be dominated by the effects of CO 2 release, particularly via acidification in the marine realm, and man-made radionuclides. The sequence stratigraphic signal is negligible to date, but may become geologically significant over centennial/millennial time scales. The rapidly growing biostratigraphic signal includes geologically novel aspects (the scale of globally transferred species) and geologically will have permanent effects.