Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases

Abstract

A review of short-term (,3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third-and fourth-order hothouse sea-level changes, the sequencestratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequencebuilding bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian-Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ 18 O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sealevel lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a −1 (longer time intervals) to 0.7 mm a −1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sealevel budget.

Warm Middle Miocene Indian Ocean Bottom Water Temperatures: Comparison of Clumped Isotope and Mg/Ca‐Based Estimates

“…Ice grounding lines extending significantly further than modern also suggest larger than modern ice sheet extent (e.g., Passchier et al, 2011). Recently, it has also been suggested that during deeper geological time periods such as the Cenomanian and Turonian hothouse periods, groundwater storage must be invoked to account for sea level cycles in an ice‐free world (Sames et al, 2020).…”

An early Pangaean vicariance model for synapsid evolution

“…3 and 4). Thus, as recently proposed by the aquifer-eustasy 92 and arido-eustasy 42 models of sea-level change, dry global climates correspond to sea-level rises, and wet global climates correspond to sea-level falls (due to excess accumulation of fresh water in continental aquifers). Such 1.4 to 1.6 million years Milankovitch-forced sedimentary cycles correlating very well with the eccentricity oscillations of earth's orbit 136 and the oscillations of the reference sea level curve (see Fig.…”

“…3 and 4). Thus, as recently proposed by the aquifer-eustasy 92,93 and the arido-eustasy 42 models of sea-level change, dry global climates correspond to sea-level rises and wet global climates correspond to sea-level falls (due to excess accumulation of fresh water in continental aquifers).…”

“…According to the arido-eustasy 42 and the aquifer-eustasy 92 , 93 models of sea-level change, dry global climates seem to correspond to sea-level rises and wet global climates correspond to sea-level falls. Accordingly, the long-term high sea-level trend that characterised the Carboniferous–Permian transition could coincide with a long-term dry period; this may have caused the reported rainforest collapse event (Fig.…”

Quantitative analysis of the sedimentary architecture of eolian successions developed under icehouse and greenhouse climatic conditions

“…Although the greenhouse geological record testifies to temporal variations in humidity (e.g., Sames et al, 2020), the greenhouse Earth did not generally experience large-magnitude shifts in global climate, relative to the glacial-interglacial oscillations of icehouse periods. As such, greenhouse conditions are generally associated with consistently elevated water tables, which experience only minor temporal changes in elevation relative to the accumulation surface (Fig.…”