Abstract
Sedimentological and geochemical records are presented for an upper Paleocene to middle Eocene deep-water pelagic succession of the Pabdeh Formation in the Paryab section, Zagros Mountains, NW, Iran. In this study, grain-size statistical parameters, cumulative curves, and bivariate analysis on twenty-five sediment samples were used to decipher depositional processes and paleoenvironments. XRD analysis of the fine-grained silt to clay sediments indicates that quartz, calcite, ankerite/dolomite, and clay minerals such as illite, chlorite, and kaolinite constitute the main minerals within these sediments. Elemental and isotopic chemostratigraphies are used to infer depositional conditions and sea level trends through time. TOC-CaCO3 trends of the samples are used to interpret the type of deposition and sediment accumulation rates, rhythmic bedding, and identification of regressional and transgressional phases. In the studied section, the manganese contents exhibit a declining trend along the lowstand systems tract that terminates in a sea level lowstand and the subsequent start of a transgressive trend. Some geochemical parameters such as Mn values and δ13C contents of sediments along a sequence can be used as potential sea level proxies that are tested in this study. The Paleocene-Eocene Thermal Maximum (PETM) interval of the Pabdeh Formation coincides with increasing Mn contents and Mn/Al ratios. Ti/Al and Si/Al ratios show contrasting trends to Mn values and Mn/Al ratios. Generally, elemental and isotopic results of the Pabdeh Formation confirm the presence of a long-term three-stage sea level cycle in the studied interval that is related to the PETM event. Based on elemental analyses such as Co, Mo, Ni, V, and Cr contents, the Pabdeh Formation sediments were deposited in suboxic to slightly anoxic conditions.
Highlights
The early Paleogene was characterized by a climatically dynamic cooling greenhouse period (e.g., Kidder and Worsley 2010) with a relatively sudden global warming event known as the Paleocene-Eocene Thermal Maximum (PETM; Kennett and Stott 1991; Thomas and Shackleton 1996; Zachos et al 2008), characterized by a worldwide 5–8 °C warming of Earth’s surface, as well as of the deep oceans (McInerney and Wing 2011; Dunkley Jones et al 2013)
Statistical parameters result on Paryab section shows no significant overall trend in grain size and shows the consistent depositional process during which the sediment particles settled through the water column
Grain size analysis indicates mean values range from clay to coarse silt to very finegrained sand
Summary
The early Paleogene was characterized by a climatically dynamic cooling greenhouse period (e.g., Kidder and Worsley 2010) with a relatively sudden global warming event known as the Paleocene-Eocene Thermal Maximum (PETM; Kennett and Stott 1991; Thomas and Shackleton 1996; Zachos et al 2008), characterized by a worldwide 5–8 °C warming of Earth’s surface, as well as of the deep oceans (McInerney and Wing 2011; Dunkley Jones et al 2013). Grain size constitutes one of the important and classical descriptive aspects of sediments and sedimentary rocks that is widely used to determine hydrodynamic conditions and depositional processes and to interpret depositional environments (Boggs 2009; Baiyegunhi et al 2017)
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