Local to global controls on the deposition of organic-rich muds across the Late Jurassic Laurasian Seaway

Abstract

Muds deposited in large-scale epicontinental seaways provide deep insights into palaeoclimates, biogeochemical cycles, sedimentation processes and organic carbon burial during exceptionally warm periods throughout the Phanerozoic. Temporal changes can be monitored at single locations but the key, larger scale oceanographical and related biogeochemical processes are likely to be more clearly revealed by comparisons between individual sub-basins within seaways. Here, we compare inorganic geochemical records from the Jurassic (upper Pectinatites wheatleyensis to lower Pectinatites pectinatus ammonite zones) of the Swanworth Quarry 1 Core from the Wessex Basin (Dorset, UK) to time-equivalent records from the Ebberston 87 Core in the Cleveland Basin (Yorkshire, UK), 400 km apart. Our synthesis shows that while the Dorset sediments were deposited in an energetically more dynamic setting than the Yorkshire sediments, the overarching climatic and oceanographical processes responsible for variations in organic carbon enrichment and sedimentation were similar. Intervals of coeval organic carbon-rich sedimentation occurred in both basins, and a particulate shuttle was intermittently active in both basins. Consistent with recent climate simulations, we conclude that tropical climate conditions, associated with enhanced nutrient supply, were key drivers of sedimentation between the Jurassic Wessex and Cleveland Basins.

Early Cretaceous subsidence of the Naturaliste Plateau defined by a new record of volcaniclastic-rich sequence at IODP Site U1513

“…The interpretation of an unstable depositional environment is furthermore supported by the highly variable Mg/Al and Rb/Al ratios (Fig. 5C), which can be used to infer changes in environmental conditions (e.g., Atar et al, 2019;Martin-Puertas et al, 2010;Schnetger et al, 2000). Mg and Rb enrichments are associated with increases in terrigenous/detrital input, fluvial runoff or precipitation.…”

“…3B). Alternatively, a winnowing effect induced by bottom currents may lead to heavy mineral enrichments (e.g., zircon) compared to clay minerals (e.g., Atar et al, 2019;Schnetger et al, 2000).…”

Sedimentation of the Kimmeridge Clay Formation in the Cleveland Basin (Yorkshire, UK)

“…This log was drawn by inspecting hand samples of the core, soon after the core was drilled. Sedimentation rates (uncorrected for compaction) for the studied interval of the EB87 core were calculated using the ammonite zonal boundaries from the Geological Timescale [67] and are 6.6 cm/ky for the Pectinatus wheatleyensis zone, 5.1 cm/ky for the Pectinatus hudlestoni zone, and 4.1 cm/ky for the Pectinatus pectinatus zone [15]. It is important to note that the calculated [36] reproduced with permission after Atar et al (2019b) [15].…”

“…As such, it has been the subject of great interest over the past century [1][2][3][4][5][6][7]. Geoscientists continue to study the KCF using techniques ranging from sedimentology [8][9][10], geochemistry [6,[11][12][13][14][15], to palaeontology [16][17][18][19], and climate modelling [20][21][22][23], in an effort to correlate deposits, elucidate depositional controls and reconstruct global climate conditions. Characterisation of the sediment facilitates the interpretation of ancient depositional environments, which provide a unique and important insight into global climate and carbon cycle dynamics [24].…”

“…Characterisation of the sediment facilitates the interpretation of ancient depositional environments, which provide a unique and important insight into global climate and carbon cycle dynamics [24]. However, lateral sediment transport and potentially multiple episodes of sediment remobilisation prior to deposition means that mudstones may record palaeoenvironment conditions from other areas of the ocean with little or no evidence of long-range transport; therefore, [36] reproduced with permission after Atar et al (2019b) [15]. (b) Geological map of the Cleveland Basin (Yorkshire, UK) after Powell (2010) [52], reproduced with permission after Atar et al (2019a) [14].…”