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- Title
Extensive Early Marine Seafloor Cementation in a Modern Epeiric Sea Induced by Seawater Properties and a Shallow Redox Boundary Below the Seafloor.
- Abstract
Extensive early marine cementation at the seafloor has important environmental implications (e.g., ocean chemistry and atmosphere pCO2), but its driver remains controversial, because many factors have been proposed to affect early marine cementation. At the Abu Dhabi coastal area of the Persian Gulf, extensive early marine cementation at the seafloor provides a good modern study case for ancient analogs. Based on petrological (thin section, cathodoluminescence and scanning electron microscope) and geochemical (e.g., δ13CDIC, alkalinity, aragonite saturation) analyses, this study investigates integrated factors from seawater to sediment properties and tests previously proposed explanations about extensive early marine cementation at the seafloor. Results suggest multiple factors involved in the early marine cementation. CaCO3 saturation, small CaCO3 saturation gradient and higher sea level in the early Holocene are consistent with former explanations. A new finding is shallow redox boundary within the seafloor sediment promoting extensive early marine cementation. The formation of shallow redox boundary is unrelated to anoxic bottom water and/or enhanced organic influx, but rather is related to: (a) high salinity under hot and arid climate, and (b) low‐energy and restricted shallow marine settings., These conditions undoubtedly occurred in past shallow and warm epeiric marine seas. This provides new insights into formation mechanism and paleoenvironmental interpretation of ancient extensive early marine cementation at the seafloor on epeiric seas. Plain Language Summary: Although nowadays (sub) tropical surface seawater is typically CaCO3 oversaturated, extensive early marine cementation is relatively uncommon at the seafloor. This is more complicated by the geological fact that early marine cementation at the seafloor is more common in Calcite seas with lower CaCO3 saturation than Aragonite seas. Understanding key factors controlling early marine cementation at the seafloor is important in many geological aspects, such as sequence stratigraphy, paleoenvironmental interpretation and hydrocarbon exploration. Based on research on a modern subtropical epeiric sea, this study suggests early marine cementation at the seafloor is controlled by both seawater properties and shallow redox boundary within seafloor sediment. The shallow redox boundary is linked to shallow, restricted marine settings and warm, arid climate. The findings herein shed new lights on ancient analogs and related environmental interpretation. Key Points: Provide insitu seawater and sediment properties associated with extensive early marine seafloor cementation on a modern epeiric seaBoth seawater properties and shallow redox boundary within the seafloor sediment are important for extensive early marine seafloor cementationThe formation of shallow redox boundary is linked to climate and topography of the seafloor, and not necessarily related to ocean oxygen level and organic influx
- Subjects
PERSIAN Gulf; ABU Dhabi (United Arab Emirates); SEAWATER; ANOXIC waters; SCANNING electron microscopes; SEQUENCE stratigraphy; ATMOSPHERIC oxygen; SUBMARINE topography; ARTIFICIAL seawater
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2022, Vol 23, Issue 8, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2022GC010444