Late Pleistocene stratigraphy of IODP Site U1396 and compiled chronology offshore of south and south west Montserrat, Lesser Antilles

Abstract

Marine sediments around volcanic islands contain an archive of volcaniclastic deposits, which can be used to reconstruct the volcanic history of an area. Such records hold many advantages over often incomplete terrestrial data sets. This includes the potential for precise and continuous dating of intervening sediment packages, which allow a correlatable and temporally constrained stratigraphic framework to be constructed across multiple marine sediment cores. Here we discuss a marine record of eruptive and masswasting events spanning 250 ka offshore of Montserrat, using new data from IODP Expedition 340, as well as previously collected cores. By using a combination of high-resolution oxygen isotope stratigraphy, AMS radiocarbon dating, biostratigraphy of foraminifera and calcareous nannofossils, and clast componentry, we identify five major events at Soufriere Hills volcano since 250 ka. Lateral correlations of these events across sediment cores collected offshore of the south and south west of Montserrat have improved our understanding of the timing, extent and associations between events in this area. Correlations reveal that powerful and potentially erosive density-currents traveled at least 33 km offshore and demonstrate that marine deposits, produced by eruption-fed and mass-wasting events on volcanic islands, are heterogeneous in their spatial distribution. Thus, multiple drilling/coring sites are needed to reconstruct the full chronostratigraphy of volcanic islands. This multidisciplinary study will be vital to interpreting the chaotic records of 3000Geochemistry, Geophysics, Geosystems PUBLICATIONS submarine landslides at other sites drilled during Expedition 340 and provides a framework that can be applied to the stratigraphic analysis of sediments surrounding other volcanic islands.

Submarine record of volcanic island construction and collapse in the Lesser Antilles arc: First scientific drilling of submarine volcanic island landslides by IODPExpedition 340

“…We recovered 434 core sections containing 2384 m of seafloor sediment samples. Information collected included physical properties on cores (thermal conductivity, shear strength, natural gamma ray emissions, P wave, magnetic susceptibility, density), and data obtained in situ by downhole logging operations (gamma rays, P wave, magnetic susceptibility, resistivity) [ Manga et al ., , Le Friant et al ., , Lafuerza et al ., , Wall‐Palmer et al ., ]. Table summarizes the location and characteristics of each hole at every site.…”

The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long‐term (>1 Ma) record offshore Montserrat, Lesser Antilles

“…Assuming that the average total erosion beneath turbidites is on the order of centimeters, and assuming that MIS boundaries have been correctly constrained within a few centimeters, the event dating errors are likely to be on the order of 10 2 −10 5 years. This is of a similar magnitude to stratigraphic gaps identified in other cores around Montserrat, including instances where >30 ka of stratigraphy was removed by turbidite erosion (JR 123‐5‐V and Hole U1396C) [ Trofimovs et al ., ; Wall‐Palmer et al ., ]. In order to assess how sensitive our event‐frequency analysis is to dating errors of this magnitude, we conduct the same analysis with three different age models.…”

“…The first occurrence of Emiliania huxleyi (250 ka) was found at 36.74 m, close to the MIS 7/8 boundary (243 ka). The first occurrence of E. huxleyi has also been identified across the MIS 7/8 transition in Hole U1396C [ Wall ‐ Palmer et al ., ] and CAR‐MON 2 [ Le Friant et al ., ] (Figure ).…”

“… Correlations of the top of core U1395B with shallow cores based on componentry and oxygen isotope data [ Le Friant et al ., ; Cassidy et al ., , ; Ogg , ; Trofimovs et al ., ; Wall ‐ Palmer et al ., ].…”

“…CAR‐MON 2 is a piston core collected in 2002, which extends 5.75 m and was taken ∼55 km to the southwest of Montserrat (Figure ) [ Le Friant et al ., ]. Site U1396C is situated ∼33 km southwest of Montserrat (Figure ) and was collected during IODP Expedition 340 [Wall‐ Palmer et al ., ].…”