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The Lower Cretaceous succession in Svalbard contains numerous glendonites, pseudomorphs after the cold-water carbonate mineral ikaite, which have been used in conjunction with other evidence to argue for episodic global cooling punctuating the greenhouse climates of the Early Cretaceous. Recent fieldwork in central Spitsbergen has recovered giant bladed glendonites of up to half a metre long, the largest ever recorded in a Lower Cretaceous site, and comparable in size to outlier glendonites found in similar-aged strata of the Sverdrup Basin in Arctic Canada. Unlike the rosette to pineapple-like morphologies seen in some of the largest Canadian Arctic specimens, the new finds in Svalbard appear only as single or crossed blades. These large glendonites, found closely associated with numerous smaller, stellate examples in the same stratigraphic interval, indicate that very local variations in pore water chemistry governed whether numerous small ikaite crystals or few large crystals grew. Taken with evidence from modern ikaite and other large ancient glendonites, we argue that large glendonites such as these (>30 cm long) are pseudomorphs after ikaites that took, at the shortest, decades, but potentially millennia to even tens of millennia to attain their massive size. As growth of the parent ikaite took place in the sediments just below the seafloor of the shallow, epicontinental seas of the High Arctic (then situated at c. 63–66°N), this is consistent with the hypothesis that geologically short-term cooling episodes interrupted the background warmth of the Early Cretaceous greenhouse, although the duration, extent, and cause of such cooling is still debated.

Sedimentary rocks can provide information about the Earth paleoenvironment and are studied extensively to understand the causes and consequences of global climate changes in deep time. They facilitate long-time perspectives that constrain climate models and provide analogues for how Earth systems may respond to, and recover from, intervals of profound environmental change, including projected anthropogenic change. The Norwegian Svalbard archipelago offers an extensive Phanerozoic stratigraphic record that reflects the geological evolution of the northern flanks of continental assemblages that include Laurentia, Eurasia, and Pangea. Svalbard's Phanerozoic sedimentary and paleoclimatic archive is controlled largely by Svalbard's overall northward plate-tectonic motion from equatorial to high latitudes but also by regional to local formation of topography and basins in response to long-term plate reorganization, as well as the near- and far-field influence of large igneous province activity on the tectono-stratigraphic and paleoclimatic development. Various sedimentary and geochemical proxies, such as bentonite beds and carbon isotope excursions associated with the far-reaching environmental effects of the Siberian Traps, the High Arctic Large Igneous Province, and the North Atlantic Igneous Province, are present in Svalbard's near complete geological record. As such, Svalbard is unique in that these and numerous other global environmental perturbations are recorded within a relatively restricted study area, with most of the key events preserved and recorded in easily accessible drill cores and well-exposed outcrop sections. Here we review deep-time paleoenvironmental and paleoclimate research in Svalbard by summarizing 148 peer-reviewed scientific articles. The review builds on the well-established tectono-stratigraphic and lithostratigraphic framework, as well as state-of-the art environmental reconstructions, to provide insights into the Earth system during the Phanerozoic northward drift of Svalbard and the many major biotic crises in the geological past. We focus on globally significant events including (i) the expansion of Devonian vegetation, (ii) the Carboniferous–Permian response to icehouse conditions during the Late Paleozoic Ice Age (LPIA), (iii) the End-Permian Mass Extinction (EPME) and the subsequent Triassic recovery, the (iv) Carnian Pluvial Episode, (v) Jurassic–Early Cretaceous climate perturbations including the Volgian Isotopic Carbon Excursion (VOICE) and the Aptian Ocean Anoxic Event 1a (OAE1a), and (vi) the Paleocene–Eocene Thermal Maximum (PETM). We present and synthesize existing core and outcrop data that preserve biological and geochemical proxies and climate-sensitive sedimentary facies that reflect environmental change in terrestrial and marine settings. Finally, we discuss the Phanerozoic climate recorded in Svalbard and its role in providing high-latitude calibration points for several global paleoclimate events to provide a higher-latitude perspective to complement the dominance of mid- and low-latitude locations and datasets in the literature.

A causal mechanism for the Volgian Isotopic Carbon Excursion (VOICE) remains enigmatic. Elemental geochemical profiles of the Deer Bay Formation, Sverdrup Basin, Arctic Canada that record the VOICE and contemporaneous strata are herein examined to provide insight into depositional environments during Late Jurassic-Early Cretaceous time. Silver (Ag) and Cadmium (Cd) are enriched across the VOICE at localities on Axel Heiberg Island, and in Tithonian (∼Volgian) strata of Ellef Ringnes Island. Other redox-sensitive trace elements do not exhibit spatially or temporally consistent patterns and indicate oxic conditions. A lack of relationship across the VOICE between Ag and the quality, quantity, and isotopic composition of organic matter suggests that the negative isotope excursion and interval of Ag enrichment are not merely functions of changes in organic matter source or amount, while a lack of spatially consistent change in geochemical indices of weathering similarly excludes climate change and/or sediment provenance as a driver. Therefore, in a ventilated setting and without marked changes in organic matter content, Ag enrichment may be due to hydrothermal activity. Contemporaneous Ag enrichment in strata from Svalbard suggests that a source of hot fluid sufficient to produce Ag-rich seawater may have been related to rifting in the adjacent proto-Amerasia Basin. Hydrothermal activity may also have been a widespread source of isotopically depleted carbon. This work develops new geochemical fingerprints that may be used to trace the spatial extent of hydrothermal events that do not leave an extinction pattern but may nonetheless have a far-reaching influence on biogeochemical systems.