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The main aim of this study is to investigate how the composition and provenance of early basin fill in Aotea Basin changes with respect to Cretaceous rifting. To date, only three wells have been drilled in Aotea Basin, all of which are included in the study (Romney-1, Hoki-1, Tane-1). Two Taranaki Basin wells are also included for comparison with Aotea Basin (Matuku-1, Maui 4). This first report (part 1) addresses Cretaceous stratigraphy and aims to build a stratigraphic framework; the second report (part 2) documents the chemical and mineralogical features with a discussion on source-to-sink composition (Higgs et al., forthcoming 2022). In this study, we have reviewed available biostratigraphy data through the Cretaceous section at the five study wells. Paleoenvironmental interpretations from biostratigraphic analyses are based largely on the abundance of dinoflagellate cysts, which are rare or absent in coastal plain environments, and rare in backshore environments, but abundant in shallow marine environments. These data have been used with conventional wireline log data to provide a broad facies interpretation; only two very short, cored intervals from Tane-1 are available for facies validation. Five main proximal to distal facies associations are defined: coastal plain, marginal marine, upper shoreface, lower shoreface to offshore transition zone, and offshore marine. Diagnostic criteria used in the interpretations include: (1) wireline log motif of stacked facies, (2) relative abundance of coals and (3) relative abundance of marine flora. Where possible, biostratigraphic dating has been assessed using both dinoflagellate and miospore zones. Dinoflagellates have only proven useful in the fully marine strata and are therefore restricted to the latest Cretaceous interval and sporadically through the older Cretaceous section at Romney-1 (the most distal study well). Because of the predominance of marginal marine environments, chronostratigraphic control is therefore mostly based on miospore zonal boundaries. However, given that the miospore zonal boundaries are based solely on the lowest occurrence of a single species, there are significant uncertainties. Boundaries may occur deeper than recorded, particularly where there is low palynomorph recovery and/or poor preservation; additionally, where caving is a problem, boundaries may actually be higher than recorded. (The authors)

This report focuses on Paleocene, Eocene and relevant latest Cretaceous strata of the Zealandia Megasequence and provides a review of paleofloral, paleoclimate and coaly source rock abundance assessments. It is the third report in a series, with previous reports focusing on the Jurassic to Early Cretaceous and mid-Cretaceous. Paleocene and Eocene strata (c. 66–34 Ma) are deposited widely throughout New Zealand’s sedimentary basins as a result of post-rift transgression and long-term passive margin subsidence. Non-marine strata of this age are predominantly present in western and south-eastern basins. A review is provided of the stratigraphy and correlation of New Zealand’s Paleocene and Eocene non-marine strata, with selected outcrop and wells discussed in more detail. There is an emphasis on palynological data, as these provide relevant information for dating and correlating coaly rock strata and understanding past vegetation and climate. Marine strata are included where important terrestrial palynomorph data have been obtained. The nearest living relative (NLR) paleoclimate reconstruction method is applied to miospore data from Tui-1 exploration well, Taranaki Basin, to reconstruct mean annual temperature (MAT) from the early Paleocene to late Eocene. New paleoclimate estimates are produced from a Paleocene leaf fossil assemblage from Strongman Mine, West Coast, and a review of known Paleocene and Eocene plant macrofossil sites and associated climate proxy data is provided. Geophysical log-derived estimates of the net thicknesses of coaly source rock lithologies are provided for four exploration wells, three in Taranaki Basin (Maui-4, Pukeko-1, Waihapa-1/-1A/-1B) and one in Great South Basin (Tara-1), and existing geochemical data are used to calculate petroleum source potential index for the three Taranaki wells. Using new and available paleotemperature data from non-marine and marine sites, and known plant micro- and macro-fossil information, an overview of New Zealand Paleocene to Eocene climate and vegetation is discussed. The Paleocene has relatively warm temperatures, with background sea surface temperatures (SSTs) of 20–22°C, and two intervals of cooler temperatures: the post-Cretaceous/Paleogene (K/Pg) boundary, where SSTs drop to c. 13°C, and late Paleocene decreases in both SST and MAT associated with deposition of the Waipawa organofacies (c. 59 Ma). Vegetation was severely affected by the K/Pg boundary event, with mixed forest vegetation replaced by ferns that then transitioned into gymnosperm-dominated assemblages that characterise the remaining Paleocene. Sparse precipitation estimates in the lower Paleocene suggest high rainfall, but these estimates are lower than from Eocene assemblages. Thermophilic vegetation is first seen in the latest Paleocene prior to short-term warming of the Paleocene–Eocene thermal maximum (c. 56 Ma) and continues into the longer-term warming of the early Eocene. Temperatures peak in the early Eocene climatic optimum, with SSTs up to c. 35°C and MAT up to c. 24°C, and vegetation is characterised by increasing angiosperm and declining gymnosperm abundance. Through the late early to middle Eocene, SSTs show notable cooling (>10°C), which contrasts with minimal cooling in MAT estimates. The reappearance of Nothofagidites pollen is seen in the middle Eocene, and miospore assemblages in the upper middle to late Eocene continue to reflect a cooler climate, with an increasing abundance and diversity of Nothofagidites taxa, disappearance of some thermophilic taxa and varying gymnosperm abundance. There is evidence of developing regional vegetation in plant communities in the late Eocene, perhaps the result of cooler climates or geographical barriers. This report provides contextual information to help understand the underlying relationships between coaly source rock formation, coal oil and gas potential, depositional controls, vegetation and paleoclimate. (The authors)

Jurassic to Early Cretaceous strata of New Zealand were deposited at high latitude on the southern margin of Gondwana in several tectonic situations, now recognised as distinct tectonostratigraphic terranes within the Eastern Province of Zealandia. To develop a chronostratigraphic framework of coaly petroleum source rock potential in relation to vegetation and climate, we review the stratigraphy of non-marine strata, estimate relative abundance of coaly lithologies in available exploration wells and outcrop sections and discuss macrofloral and palynological evidence for paleoclimate. Marine strata with relevant paleobotanical data are also mentioned but covered in less detail. This work is part of a larger programme of research into petroleum source rocks. The Drumduan Terrane in Nelson City includes plant-bearing carbonaceous siltstone of mid Jurassic age in a non-marine sequence of volcanogenic breccia and finer clastics. Thin coal seams occur in similar strata further south, but metamorphic rank throughout is too high for miospore preservation. In Southland, Permian strata of the Brook Street Terrane are unconformably overlain by Barretts Formation, fossiliferous fluvial to estuarine strata of mid Jurassic age. This unit is predominantly sandstone and conglomerate, but finer sediments, including thin coal beds, occur locally. Good miospore preservation indicates a low degree of thermal maturity. The Torlesse Composite Terrane has yielded Jurassic and Early Cretaceous palynofloras at some localities, and non-marine strata with macroscopic plant fossils of mid Jurassic age at several Canterbury localities. Miospore preservation at some localities indicates low thermal maturity, but, at other places, carbonaceous material is of anthracite coal rank. In these terranes, lack of detailed lithological logs from outcrop sections prevented numerical estimates of the relative proportion of coaly rocks. The Murihiku Terrane includes extensive outcrop of Jurassic strata in western North Island and southern South Island, and Early Cretaceous in the subsurface of Northland. The relatively undeformed strata are largely of marine facies but include non-marine sediments of mid- and latest Jurassic age. Plant macrofossils are well-documented from the non-marine strata, and the whole sequence has provided palynological data. Lithological logs from six measured outcrop sections, and geophysical logs from three petroleum exploration wells (Waka Nui-1, Pluto-1 and Pukearuhe-1), were used to estimate relative proportions of coal, shaly coal and coaly mudstone. Coaly lithologies make up a very small percentage of the total Jurassic interval in the wells, ranging from