Luminescence age estimates of Pleistocene marine terrace and alluvial fan sediments associated with tectonic activity along coastal Otago, New Zealand

Abstract

Six luminescence age estimates have been obtained from raised beach sands and loess, and alluvial fan sediments in the outboard zone of the active Otago reverse fault province, coastal Otago, New Zealand. These age estimates constrain the timing of movement of the Akatore Fault and the Titri Fault System. Five of the samples were dated by optical dating of K-feldspar in the polymineral fine silt fraction; the remaining sample was dated using thermoluminescence (TL) emitted from quartz (fine sand fraction). Raised beach sands from the lowest Pleistocene marine terrace on the upthrown side of the reverse faults (Taieri Beach) yielded ages of 117 ± 13 ka (optical dating, K-feldspar) and 117 ± 12 ka (TL dating, quartz), indicating terrace formation during the peak sea-level highstand of the last interglacial, marine oxygen isotope substage (MISS) 5e (c. 125 ka). The K-feldspar optical age has not been corrected for anomalous fading, but its consistency with the quartz TL age indicates that anomalous fading is insignificant in this sample. Samples from a raised beach sand unit and an underlying loess unit that bracket a marine terrace that has previously been associated with the c. 125 ka sea-level highstand, situated 10 km northeast of the effects of faulting (Warrington), yielded optical age (K-feldspar) estimates of 97 ± 11 and 96 ± 5 ka, respectively. These ages have not been corrected for anomalous fading and therefore the true ages might be slightly older. Two loess units within alluvial fans along the Titri Fault System in the Waihola region yielded optical age estimates of 92 ± 5 and 151 ± 5 ka (both K-feldspar), which bracket the last period of faulting along the Titri Fault System; the latter age result is consistent with geomorphic evidence that suggests fan formation during the glacial period MIS 6 (186-128 ka); this consistency also implies that there was no significant anomalous fading in these samples. Together with published radiocarbon ages, our results imply that no activity has occurred on the Akatore Fault in the period c. 125-3.8 ka and only localised activity (at Moneymore) on the Titri Fault System post-150 ka.

Correlation of fluvial terraces within the Hikurangi Margin, New Zealand: implications for climate and baselevel controls

“…Although generally sparse, organic material is present as wood within the gravel-dominated deposits, and also occurs as peat in terrace cover deposits, and charcoal within tephras. Luminescence dating is being increasingly used in New Zealand to extend age control beyond the limits of radiocarbon dating, and has particularly been used to date loess (e.g., Berger et al, 1992Berger et al, , 2001Berger et al, , 2002Litchfield and Lian, 2004). The present study is the first to apply Optically Stimulated Luminescence (OSL) dating directly to fluvial deposits in the eastern North Island, although OSL ages of loess coverbeds have been used to estimate the minimum ages of river terrace deposits (Wang, 2001;Formento-Trigilio et al, 2003).…”

Luminescence dating of young coastal deposits from New Zealand using feldspar

“…A comprehensive review by Jacobs (2008) compiles all these coastal studies and a review by Madsen and Murray (2009) summarizes the dating of young (<1000 years) coastal and aeolian sediments. So far, a limited number of studies have been published from coastal sites in New Zealand (Duller, 1996;Shulmeister et al 1999;ReesJones et al 2000;Nichol, 2002;Litchfield and Lian, 2004;Cooper and Kostro, 2006;Kennedy et al 2007) and these have focused mainly on Pleistocene deposits (older than 10,000 years). Only Shulmeister and Kirk (1996) and Nichol et al (2003) present chronologies on a millennial time-scale of Holocene (younger than 10,000 years) dune ridges.…”

Marine submersion of an archaic moa-hunter occupational site, Shag River estuary, North Otago

“…The 65-km-long Akatore Fault has a maximum of c. 120 m of Quaternary uplift (Litchfield & Norris 2000). Detailed studies of the onshore section have identified two rupture events within the Holocene (Litchfield & Norris 2000;Litchfield & Lian 2004). The youngest rupture is well constrained by 14 radiocarbon ages at AD 800Á950 (Litchfield & Norris 2000), although McFadgen (2007) has reinterpreted the constraining dates and extended the possible age to lie between AD 900 and 1450.…”