Element maps from 5x 10 cm sections generated using the Zeiss Sigma HD Field Emission Gun Analytical SEM at Cardiff University. Maps come from sections within the early Miocene pelagic interval situated directly below the Nicobar Fan succession at IODP Site U1480 in the Eastern Equatorial Indian Ocean (for more information see published report, https://doi.org/10.1016/j.epsl.2017.07.019). These specific sections were chosen to examine the depositional environments associated with transitions from red clays to white chalk, which demonstrate distinct banding at the micro and macro scale.

This dataset comprises palynological counts on sediments from IODP Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Marine palynomorphs are counted in 23 samples, and 7 samples were counted for terrestrial palynomorphs (pollen and spores). Shipboard biostratigraphy and magnetostratigraphy suggests the samples are early Miocene in age (McKay et al., 2019, Proceedings of the International Ocean Discovery Program).

This dataset comprises continuous logging of clasts >2 mm from International Ocean Discovery Program Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Shipboard biostratigraphy and magnetostratigraphy suggests the sediments are early Miocene in age (McKay et al., 2019, Proceedings of the International Ocean Discovery Program). Logged clasts are grouped by core into seven main lithological groups: igneous rocks, quartz fragments, dolerites, volcanic rocks, metamorphic rocks, sedimentary rocks and sedimentary intraclasts. A full methods description is provided at the bottom of the data file. The clast abundances can be compared to knowledge of terrestrial geology, allowing the changing provenance of the sediments to be traced.

Data derived from NERC Grant NE/N001621/1. Geographical Area - DSDP/ODP/IODP Sites 516, 1138, 925, 242, 1338, 871, 872

This dataset comprises 35 samples analysed for clay mineralogy from IODP Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Shipboard biostratigraphy and magnetostratigraphy suggests the samples are mainly early Miocene in age (McKay et al., 2019, Proceedings of the International Ocean Discovery Program). The uppermost samples do, however, include younger Plio-Pleistocene sediments.

Count data (original counts and percentage abundances) from nannofossil assemblage analysis of Early Miocene samples. These form the prime data for a paper submitted to Palaeogeography, Palaeoclimatology, Palaeoecology (Young et al. submitted, 2019).

We report sedimentary coatings and fish teeth neodymium isotope values – tracers for water-mass mixing – from deep-water International Ocean Discovery Program (IODP) Site U1438 (4.7 km water depth) in the Philippine Sea, northwest Pacific Ocean. The time period encompasses the last 20 million years.

This dataset comprises 40Ar/39Ar dated detrital hornblende grains for 5 samples from IODP Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Shipboard biostratigraphy and magnetostratigraphy suggests the samples are early Miocene in age (McKay et al., 2019, Proceedings of the International Ocean Discovery Program). These data can be compared to terrestrial geochronological data, allowing the changing provenance of the sediments to be traced.

Mg/Ca in multiple species of planktonic foraminifera from five time slices since the Middle Miocene to present (target ages 15, 12.5, 10, 7.5, 4.5, 2.5 and 0 Ma). These samples are from a range of globally and latitudinally distributed DSDP (Deep Sea Drilling Program), ODP (Ocean Drilling Program), IODP (International Ocean Discovery Program) open ocean sites. From low to high latitudes these are: Site U1338, U1489 (Eastern and Western Equatorial Pacific), Sites 871, 872, and Site U1490, (Western Tropical Pacific), Site 242 (Mozambique Channel, Indian Ocean), U1482 (Australian Continental Margin), Site 516 (Western Atlantic Ocean), Site 1138 (Kerguelen Plateau, Southern Ocean). The Mg/Ca ratios were measured using Inductively coupled mass spectrometry (ICP-MS) at Cardiff University between December 2018 and June 2019. The data were collected to explore Mg/Ca values for modern and extinct species at different intervals of time (which were different climatically) and at different geographical locations. This data was collected by E.Mawbey as part of a project funded by NERC (Q10 project) to investigate changes in foraminiferal depth habitat in response to different climate conditions.

This dataset comprises zircon U-Pb data on 11 samples, each containing ~90-150 individual grains. This method was applied to sediment samples from IODP Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Shipboard biostratigraphy and magnetostratigraphy suggests the samples are mainly early Miocene in age (McKay et al., 2019). The uppermost samples do, however, include younger Plio-Pleistocene sediments. Samples were measured using an Agilent 7900 laser ablation inductively-coupled plasma mass spectrometer (LA-ICP-MS) with a 25-35 µm pit diameter in the London Geochronology Centre at University College London.