Constraining recycled detritus in quartz‐rich sandstones: Insights from a multi‐proxy provenance study of the Mid‐Carboniferous, Clare Basin, western Ireland

Abstract

Quartz‐rich sandstones can be produced through multiple sedimentary processes, potentially acting in combination, such as extensive sedimentary recycling or intense chemical weathering. Determining the provenance of such sedimentary rocks can be challenging due to low amounts of accessory minerals, the fact that the primary mineralogy may have been altered during transport, storage or burial and difficulties in the recognition of polycyclic components. This study uses zircon and apatite U‐Pb geochronology, apatite trace elements, zircon‐tourmaline‐rutile indices and petrographic observations to investigate the sedimentary history of mineralogically mature mid‐Carboniferous sandstones of the Tullig Cyclothem, Clare Basin, western Ireland. The provenance data show that the sandstones have been dominantly and ultimately sourced from three basement terranes: older Laurentian‐ associated rocks (ca. 900–2500 Ma) which lay to the north of the basin, peri‐Gondwanan terranes (ca. 500–700 Ma) to the south and igneous intrusive rocks associated with the Caledonian Orogenic Cycle (ca. 380–500 Ma). However, the multi‐proxy approach also helps constrain the sedimentary history and suggests that not all grain populations were derived directly from their original source. Grains with a Laurentian or a Caledonian affinity have likely been recycled through Devonian basins to the south. Grains with a peri‐Gondwanan affinity appear to be first cycle and are potentially derived from south/southwest of the basin. Taken as a whole, these data are consistent with input into the basin from the south and southwest, with the reworking of older sedimentary rocks, rather than intensive first‐cycle chemical weathering, likely explaining the compositional maturity of the sandstones. This study highlights the need for a multi‐proxy provenance approach to constrain sedimentary recycling, particularly in compositionally mature sandstones, as the use of zircon geochronology alone would have led to erroneous provenance interpretations. Zircon, together with U‐Pb geochronology from more labile phases such as apatite, can help distinguish first‐cycle versus polycyclic detritus.

Heavy mineral variations in mid‐Carboniferous deltaic sandstones: Records of a pre‐depositional sediment history?

“…The most recent provenance model suggests that sandstones of the Tullig Cyclothem are derived from multiple sources from the south and south‐west, with fresh input from peri‐Gondwanan terranes and recycling of Laurentian and Caledonian material through Devonian sedimentary rocks. This previous study ascribes the compositional maturity of these sandstones to sedimentary recycling rather than the chemical weathering that could have occurred during transport (Nauton‐Fourteu et al, 2020). Apatite U‐Pb geochronology coupled with trace element data suggest that Caledonian (potentially Donegal and Galway granites) apatite has survived recycling through the Old Red Sandstones of the Dingle Basin (Nauton‐Fourteu et al, 2020).…”

“…The Clare Basin is located above the Iapetus Suture, which represents the collision between Avalonia‐Baltica and Laurentia during the late Silurian (Fairey et al, 2018; Waldron et al, 2014). The subsidence of the basin is generally believed to be linked with the reactivation of Iapetus Suture structures; however, there are contrasting models to explain how this occurred (Martinsen et al, 2017; Nauton‐Fourteu et al, 2020; Pyles, 2008; Wignall & Best, 2016).…”

“…Sandstones from the Tullig Cyclothem of the Clare Basin have been classified as fine to medium quartz arenites, with finer grain sizes observed in mouth bar and interdistributary bay sandstones than in channelised sandstones (Nauton‐Fourteu et al, 2020). Significant quartz overgrowths are common, resulting in an intra‐grain porosity close to zero, highlighting the potential significant impact of burial diagenesis.…”

“…A multi‐proxy provenance study of the Tullig Cyclothem has allowed for detailed sources and sediment routing interpretations (Nauton‐Fourteu et al, 2020). The most recent provenance model suggests that sandstones of the Tullig Cyclothem are derived from multiple sources from the south and south‐west, with fresh input from peri‐Gondwanan terranes and recycling of Laurentian and Caledonian material through Devonian sedimentary rocks.…”

“…This study aims to utilise heavy mineral analysis to better understand modifications to sediment composition which can occur in the hinterland, prior to deposition, and more specifically better constrain the impacts of sediment hinterland residence time and associated palaeoweathering. The Tullig Cyclothem of the mid‐Carboniferous Clare Basin, western Ireland, for which provenance has been previously constrained, is used as a case study (Nauton‐Fourteu et al, 2020). Such sedimentary rocks were deposited as a response to the high‐frequency sea‐level fluctuation intrinsically linked with climate, thus potentially recording variations of palaeoweathering conditions in the hinterland (Pyles, 2008).…”