University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln ANDRILL Research and Publications Antarctic Drilling Program 2010 40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): Correlations with the Erebus Volcanic Province and implications for the age model of the core Gianfranco Di Vincenzo Istituto di Geoscienze e Georisorse, CNR, Pisa, Italy, [email protected] Laura Bracciali Università di Pisa Paola Del Carlo Istituto Nazionale di Geofisica e ulcanologia,V Pisa, Italy Kurt Panter Bowling Green State University, [email protected] Sergio Rocchi Università di Pisa Follow this and additional works at: https://digitalcommons.unl.edu/andrillrespub Part of the Environmental Indicators and Impact Assessment Commons Di Vincenzo, Gianfranco; Bracciali, Laura; Del Carlo, Paola; Panter, Kurt; and Rocchi, Sergio, "40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): Correlations with the Erebus Volcanic Province and implications for the age model of the core" (2010). ANDRILL Research and Publications. 52. https://digitalcommons.unl.edu/andrillrespub/52 This Article is brought to you for free and open access by the Antarctic Drilling Program at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in ANDRILL Research and Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Published in Bulletin of Volcanology: Official Journal of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), Volume 72 (2010), pp. 487–505; doi: 10.1007/s00445-009-0337-z Copyright © 2010 Springer-Verlag. Used by permission. Submitted May 26, 2009; accepted December 11, 2009; published online January 26, 2010. 40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): Correlations with the Erebus Volcanic Province and implications for the age model of the core Gianfranco Di Vincenzo,1 Laura Bracciali,2 Paola Del Carlo,3 Kurt Panter,4 and Sergio Rocchi 2 1. Istituto di Geoscienze e Georisorse, CNR, via Moruzzi 1, I-56124 Pisa, Italy 2. Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, I-56126 Pisa, Italy 3. Sezione di Pisa, Istituto Nazionale di Geofisica e Vulcanologia, via della Faggiola 32, I-56126 Pisa, Italy 4. Department of Geology, Bowling Green State University, Bowling Green, OH 43403, USA Corresponding author — Gianfranco Di Vincenzo, email [email protected] Abstract gests that volcanic rocks within the AND-2A core were sup- The AND-2A drillcore (Antarctic Drilling Program—AN- plied from the south, possibly with source areas closer to the DRILL) was successfully completed in late 2007 on the Antarc- drill site for the upper core levels, and from 358 m below sea tic continental margin (Southern McMurdo Sound, Ross Sea) floor down hole, with the “proto-Mount Morning” as the main with the aim of tracking ice proximal to shallow marine envi- source. ronmental fluctuations and to document the 20-Ma evolution Keywords: ANDRILL SMS, 40Ar–39Ar geochronology, Erebus of the Erebus Volcanic Province. Lava clasts and tephra layers volcanic province, McMurdo Sound, Lava clasts, Sedimenta- from the AND-2A drillcore were investigated from a petro- tion rate, Tephra layers, Victoria Land Basin graphic and stratigraphic point of view and analyzed by the 40Ar–39Ar laser technique in order to constrain the age model Introduction of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early In December 2007, the Antarctic Drilling (ANDRILL) Miocene. Ten out of 17 samples yielded statistically robust program completed its second hole (AND-2A, Figure 1), 40Ar–39Ar ages, indicating that the AND-2A drillcore recov- recovering 98% of the sediments cored to a depth of ered ≤230 m of Middle Miocene (~128–358 m below sea floor, 1,138.54 m below the sea floor (bsf) in McMurdo Sound ~11.5–16.0 Ma) and >780 m of Early Miocene (~358–1093 m be- (Florindo et al. 2008; Harwood et al. 2008). The funda- low sea floor, ~16.0–20.1 Ma). Results also highlight a nearly mental goal of the ANDRILL program is to obtain from continuous stratigraphic record from at least 358 m below high-resolution sediment cores important new infor- sea floor down hole, characterized by a mean sedimentation mation about the Neogene Antarctic climate and evolu- rate of ~19 cm/ka, possible oscillations of no more than a few tion of Antarctic rift basins (http://andrill.org/). A fo- hundreds of ka and a break within ~17.5–18.1 Ma. Compari- cus of the Southern McMurdo Sound (SMS) project is to son with available data from volcanic deposits on land, sug- recover strata from the Middle Miocene, a period char- 487 488 DI VINCENZO ET AL. IN BULLETIN OF VOLCANOLOGY 72 (2010) acterized by warmer conditions (Middle Miocene Cli- ANDRILL hole (AND-1B, MIS in Figure 1) during the matic Optimum) followed by long-term climate change McMurdo Ice Shelf project (Naish et al. 2007). towards cold-polar conditions (Flower and Kennett All the objectives of the SMS project rely heavily on 1994; Zachos et al. 2001; Holbourn et al. 2007; Zachos et the achievement of an age model for the core that is as al. 2008). This objective was accomplished, providing an accurate as possible. This study reports the entire set of expanded Early to Middle Miocene record (Harwood 40Ar–39Ar data available from volcanogenic products of et al. 2008) and filling the gap left by previous drilling the AND-2A core in conjunction with petro-chemical of older sediments (~34–17 Ma) recovered in the Cape and lithological data of the dated materials, with a two- Roberts project (CRP in Figure 1—Barrett 2007) and fold purpose: first, to examine possible correlations with younger sediments (~14–0 Ma) recovered in the first the activity of the Erebus Volcanic Province in order to Figure 1. Satellite image of the McMurdo Sound area showing the location of the ANDRILL SMS (AND-2A) drill site and previ- ous drill sites. Inset b has been redrawn and modified after Fielding et al. (2008a). 40AR–39AR DATING OF VOLCANOGENIC PRODUCTS FROM THE AND-2A CORE 489 constrain possible volcanic sources; and second, to dis- canism. Large volcanoes include Mount Erebus cuss the implications for the age model of the core and, (~2,000 km3), Mount Terror, and Mount Bird, which more in general, for sedimentation in the Victoria Land form Ross Island, Mount Discovery, Minna Bluff, and Basin since Early Miocene. Mount Morning located on the mainland (Figure 1). These volcanoes as well as many smaller volcanic cen- ters (e.g., Brown Peninsula, White and Black Islands) Background and volcanic fields (foothills of Royal Society Range, Wright–Taylor Valleys, Dailey Islands group) are part The AND-2A core of the Erebus Volcanic Province of the McMurdo Volca- nic Group (Kyle and Cole 1974; Kyle 1990a, b). The Ere- The AND-2A core contains terrigenous clastic lithol- bus Volcanic Province represents the largest area of ex- ogies ranging from claystones through siltstones and posed Late Cenozoic volcanic rocks and the longest and sandstones to conglomerates, breccias, and diamictites. most complete record of alkaline volcanism in Antarc- The core is subdivided into 14 lithostratigraphic units tica. The volcanic deposits on land range in age from ap- on the basis of major changes in lithology with partic- proximately 19 Ma to current Strombolian-style activity ular emphasis on diamictite abundance and associ- within the summit crater of the Erebus Volcano (Dibble ated sediments relative to other lithologies (Fielding et et al. 2008: Kelly et al. 2008). Evidence for older activ- al. 2008b). Fielding et al. (2008b) identified 13 recurring ity is from volcaniclastic sediments and tephra found in lithofacies interpreted to represent a wide spectrum of drill cores (CIROS-1, MSSTS-1, Cape Roberts, and AND- depositional environments ranging from minimally ice- 2A) and extends the history of alkaline volcanism in this influenced, shallow marine settings (e.g., diatomite and area back to 26–20 Ma (Gamble et al. 1986; Barrett 1987; fossil-rich mudstone), through ice contact proglacial and McIntosh 1998, 2000). glacimarine (e.g., ripple cross-laminated sandstone, in- The volcanism is located in the southern portion of terlaminated sandstone, siltstone, and diamictite) to the Victoria Land Basin, one of four major rift-related possibly subglacial environments (e.g., massive diamic- basins within the Ross Sea (Figure 1b), which, along tite that shows extensive shear and rotation fabrics). The with the Transantarctic Mountains, are components of lithologies are arranged vertically in a repetitive fashion the West Antarctic rift system (Van der Wateren and through the length of the core and are divided into 70 Cloetingh 1999). Extension, rifting, and basin subsid- sequences, each of which fine upward and are truncated ence began in the Eocene to Early Oligocene (Fielding et by the next sequence boundary (Fielding et al. 2008b). al. 2008a). On the basis of drillhole and seismic reflection Each sequence possibly represents a cycle of maximum studies (Fielding et al. 2008a and references therein), ice advance followed by a transgression towards mini- the Victoria Land Basin evolved in a series of intervals mum ice conditions (C. Fielding, personal communica- each reflecting changes in basin forming tectonic pro- tion, 2009). cesses. A phase of renewed rifting during the Middle to Volcanic material is persistent throughout the AND- Late Miocene in the Southern Victoria Land Basin pro- 2A core and is the dominant clast type (>50%) in nine duced the Terror Rift (Wilson 1995, 1999; Fielding et al. of the 14 lithostratigraphic units (Panter et al. 2008). 2008a).