02076nas a2200241   4500000000100000008004100001260003300042100001500075700001700090700001600107700001600123700001600139700001600155700001700171700001700188700001300205700001700218700001400235245011200249856003900361300002200400520141200422       2012                            d  bGeological Society of London1 aM. Cassidy1 aJ. Trofimovs1 aS.F.L. Watt1 aM.R. Palmer1 aR.N. Taylor1 aT.M. Gernon1 aP.J. Talling1 aA. Le Friant1 aG. Wadge1 aR. Robertson1 aB. Voight00aMulti-stage collapse events in the South Soufrière Hills, Montserrat, as recorded in marine sediment cores  uhttp://eprints.soton.ac.uk/338926/  a383\textendash3973 a<p>We present new evidence for sector collapses of the South Soufrière Hills (SSH) edifice, Montserrat during the mid-Pleistocene. High-resolution geophysical data provide evidence for sector collapse, producing an approximately 1 km3 submarine collapse deposit to the south of SSH. Sedimentological and geochemical analyses of submarine deposits sampled by sediment cores suggest that they were formed by large multi-stage flank failures of the subaerial SSH edifice into the sea. This work identifies two distinct geochemical suites within the SSH succession on the basis of trace-element and Pb-isotope compositions. Volcaniclastic turbidites in the cores preserve these chemically heterogeneous rock suites. However, the subaerial chemostratigraphy is reversed within the submarine sediment cores. Sedimentological analysis suggests that the edifice failures produced high-concentration turbidites and that the collapses occurred in multiple stages, with an interval of at least 2 ka between the first and second failure. Detailed field and petrographical observations, coupled with SEM image analysis, shows that the SSH volcanic products preserve a complex record of magmatic activity. This activity consisted of episodic explosive eruptions of andesitic pumice, probably triggered by mafic magmatic pulses and followed by eruptions of poorly vesiculated basaltic scoria, and basaltic lava flows.</p>