Mesozoic long-term eustatic cycles and their uncertain hierarchy

Abstract

a b s t r a c tGlobal sea-level has changed in a cyclic manner through geologic history, but the regularities of these changes are yet to be fully understood. Despite certain (and sometimes significant) differences, the available Mesozoic eustatic curves permit the outlining of long-term eustatic cycles, which are provisionally defined as cycles recognizable at the stage level and higher. Interpretation of the Triassic eustatic curves indicates two orders of long-term cycles and a 1st-order sea-level rise throughout the entire period. The Jurassic eustatic curves imply cyclicity of one or two orders, and a 1st-order eustatic rise during the entire period is also evident. Most challenges are interpretations for the Cretaceous; two to four orders of long-term eustatic cycles can be established for this period. Generally, the hierarchy of the long-term eustatic cycles might have changed through the Mesozoic. If so, and if one considers differences of cycles of the same order between the periods of this era, it is difficult to apply "standard" hierarchical classifications to the documented cycles. The hypothetical uncertainty of the hierarchy of the Mesozoic long-term eustatic cycles is an important challenge for modern researchers.

Long-term shoreline shifts on continental blocks during the Bajocian: an updated interpretation based on synthetic stratigraphical and palaeogeographical developments on regional scales

“…Hypothetically, such a transgression could be related to a global sea level rise. Ruban's (2015) interpretation raises doubts over a eustatic rise during the Bajocian, and this concern is supported by data supplied by Ruban & Sallam (2016) for northeast Africa, which also implies the doubtful nature of such a rise. Below, we attempt to update current knowledge on long-term shoreline shifts on major continental blocks during the Bajocian.…”

“…Two main alternative reconstructions of Jurassic global sea level changes were proposed by Hallam (1978Hallam ( , 1988 and Haq et al (1987), respectively. Both of these have been updated subsequently, by Hallam (2001) and Haq & Al-Qahtani (2005), respectively, with further reinterpretation by Ruban (2015). Finally, Haq (2018) presented another revised version of the Jurassic global sea level curve.…”

Genetic sequence stratigraphy on the basis of ichnology for the Middle Jurassic basin margin succession of Chorar Island (eastern Kachchh Basin, western India)

“…The thick argillaceous shales overlain by micritic sandstone represent a gradual increase in the base level, interrupted by a short-term decrease in local accommodation space with a change in hydrodynamic conditions which allowed deposition of coarse-grained micritic sandstone towards the end of the Bajocian. Haq et al (1988) and Ruban (2015) also depicted the worldwide gradual transgression during the Bajocian, with short-term changes as regression. The intercalated sequence of mixed siliciclastic-carbonate sediments indicates an increase in carbonate content.…”

Did plate tectonics control the generic diversity of Jurassic brachiopods? One point of view

“…Moreover, it still remains unclear how correct the curve proposed by Haq & Al-Qahtani (2005) is. Some evidence that questions the accuracy of this curve and its predecessors is available (Hallam, 1988(Hallam, , 2001Ruban & Sallam, 2016; see also discussions in Ruban, 2015Ruban, , 2016. However, Hypothesis 3 cannot be fully rejected.…”

“…1. Global Jurassic brachiopod diversity dynamics (after Curry & Brunton, 2007) in the light of tectonic processes (curves adapted from Matthews et al, 2016) and eustatic changes (curve adapted from Haq & Al-Qahtani, 2005; see also Ruban, 2015 1995; Harries & Little, 1999;Wignall et al, 2005;Caswell et al, 2009;Baeza-Carratalá et al, 2016, 2017, 2018Vörös et al, 2016;Caswell & Frid, 2017;Ruban, 2018). However, it is questionable whether the mass extinction was the sole cause of such a long diversity lowstand; probably, some other factor(s) was (were) also responsible for the latter.…”