Neoproterozoic Nafun Group Sediments from Oman Affected by an Active Continental Margin

Liang Yue,Veerle Vandeginste

doi:10.3390/min10060511

Abstract

The Neoproterozoic era is a time of major environmental change in Earth history. The Ediacaran period (635–541 Ma), the uppermost division of Precambrian time, is characterized by the remarkable Shuram excursion (largest C isotope negative excursion), a deep ocean water oxidation event, and Ediacaran biota. The Nafun Group of Oman provides a well-preserved and mostly continuous section of an Ediacaran succession. Based on geochemical data from the Nafun Group, the Shuram excursion (SE) and deep ocean oxidation hypotheses were proposed. Now, we sampled this section at high stratigraphic resolution, and present here the petrographical and geochemical analysis of the Khufai, Shuram and Buah Formations. The major and trace element analysis of shales from the Shuram Formation indicates that northern Oman was an active continental margin environment in Neoproterozoic times. The provenance of the Shuram Formation was primarily mafic and intermediate igneous rocks. With the unsteady tectonic setting, the development of the Nafun Group was influenced by hydrothermal supply and volcaniclastic input. Based on the V/Cr and U/Th ratio of the samples from the Nafun Group, our study reveals the transition of the ocean water redox environment, which is connected to the rise and fall of the Ediacaran biota. Our study constrains the tectonic setting of northern Oman and the petrography and geochemical data from the Nafun Group for the hydrothermal and volcaniclastic supply. Thus, our study acknowledges more factors for the explanation of the Ediacaran conundrums.

Highlights

Marine carbon isotope changes provide direct information on the global carbon cycle.The Ediacaran Shuram Formation (Nafun Group in Oman) is well known for the Shuram NegativeExcursion (SE), which represents the largest carbon isotope excursion in geological history [1,2,3,4], with carbonate carbon isotopes values down to −12% VDB
Grotzinger et al [20] considered that an Andean margin developed in eastern Oman and that the Nafun Group is related to subsidence of the lithosphere caused by the subduction of oceanic lithosphere beneath the Arabian plate
For the regional subsidence in the Ediacaran period, Grotzinger et al [20] and Hisham and John [70] considered that an Andean margin developed in eastern Oman and that the Nafun Group was related to subsidence of the lithosphere caused by the subduction of oceanic lithosphere beneath the Arabian plate

Summary

Introduction

Marine carbon isotope changes provide direct information on the global carbon cycle.The Ediacaran Shuram Formation (Nafun Group in Oman) is well known for the Shuram NegativeExcursion (SE), which represents the largest carbon isotope excursion in geological history [1,2,3,4], with carbonate carbon isotopes values down to −12% VDB. The Ediacaran Shuram Formation (Nafun Group in Oman) is well known for the Shuram Negative. The SE may have been caused by the oxidation of marine dissolved organic carbon (DOC) [5,6,7,8], water column stratifications [9,10], burial diagenesis alteration [11], methane-derived 13 C-depleted authigenic carbonate [4,5,12,13,14], and terrestrial organic carbon through weathering [15,16]. Grotzinger et al [20] considered that an Andean margin developed in eastern Oman and that the Nafun Group is related to subsidence of the lithosphere caused by the subduction of oceanic lithosphere beneath the Arabian plate. By the lack of outcrops and an incomplete understanding of tectonic evolution of the Huqf Supergroup (including Abu Mahara, Nafun and Ara Group), the tectonic models of Oman are hampered [21]

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