Welcome to our field trip through the Plio-Pleistocene Whanganui Basin (WB) in the ManawatūWhanganui Region of the lower North Island, Aotearoa New Zealand (Fig. 1). The trips overarching theme is the influence of large-volume silicic volcanism on sedimentation within a dominantly shallow-marine sedimentary basin. More specifically, we will be exploring primary and reworked deposits from the Taupō Volcanic Zone (TVZ) in the central North Island of Aotearoa New Zealand, which form key marker horzions within the WB sedimentary succession, underpinning the basins chronostratigraphic framework and facilitating field mapping and regional correlation. The WB contains one of the most complete Quaternary stratigraphic records in the world, including cyclic, dominantly shallow marine strata that record glacio-eustatic sea-level fluctuations (Pillans 2017). Our journey will take us through rural hill country and river valleys to witness landscapes and outcrops that have only emerged from the sea in the last 1 million years. The field trip follows a transect from Palmerston North through the Rangitīkei and Pohangina valleys, with an overnight stay at Makoura Lodge. Stops have been selected to showcase key sedimentary units within the basin succession and explore the significance of these deposits for understanding basin history and the paleogeographic evolution of the lower North Island of Aotearoa New Zealand (Fig. 2). We will track primary and reworked volcaniclastic marker horizons through the basin to witness how they are expressed across different depositional settings and how they can be used for correlation and stratigraphic interpretation. The deposits are all less than 3 million years old and provide a distal record of volcanic activity in the central North Island, including the initiation of the Taupō Volcanic Zone (TVZ) at ~2 Ma, which is considered to be the most productive silicic volcanic region in the world with at least 12 caldera forming eruptions producing over 3300 km3 DRE of magma over the last 350 ka (Houghton et al. 1995; Wilson et al. 1995; Kósik et al. 2020). In addition, the trip will highlight river terraces preserved within actively uplifting landscapes that record partial inversion of the sedimentary basin and the interplay between sediment supply, stream power and base level associated with Quaternary climate events over the last ~350 thousand years. Overlying loess, tephra and paleosol coverbeds will be explored to gain insight into how these landforms are mapped and how they have formed through the late Quaternary. The WB is also a cultural landscape of deep significance to Māori. Māori have deep ties to the land (whenua), viewing it as not just a physical place but as a spiritual ancestor (Papatūānuku) from whom all life originates, central to their identify and culture. A visit to Rātā Marae will provide us with an opportunity to appreciate the connection to the land and water that hosts this internationally important geological record. A more detailed introduction to the WB and TVZ is provided in subsequent sections of this guide, followed by descriptions of each field trip stop, including the stratigraphy, age and key messages. Together, these stops offer a cross-section through the WB to explore how large-volume silicic volcanism has influenced sedimentation, stratigraphy, and geological interpretation within one of the world's premier Quaternary sedimentary basins.
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