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Cryogenian glaciostatic and eustatic fluctuations and massive Marinoan-related deposition of Fe and Mn in the Urucum District, Brazil
Geology ( IF 5.8 ) Pub Date : 2021-12-01 , DOI: 10.1130/g49134.1
B.T. Freitas 1 , I.D. Rudnitzki 2 , L. Morais 3, 4 , M.D.R. Campos 1 , R.P. Almeida 3 , L.V. Warren 5 , P.C. Boggiani 3 , S. Caetano-Filho 3 , C. Bedoya-Rueda 3 , M. Babinski 3 , T.R. Fairchild 3 , R.I.F. Trindade 4
Affiliation  

Global Neoproterozoic glaciations are related to extreme environmental changes and the reprise of iron formation in the rock record. However, the lack of narrow age constraints on Cryogenian successions bearing iron-formation deposits prevents correlation and understanding of these deposits on a global scale. Our new multiproxy data reveal a long Cryogenian record for the Jacadigo Group (Urucum District, Brazil) spanning the Sturtian and Marinoan ice ages. Deposition of the basal sequence of the Urucum Formation was influenced by Sturtian continental glaciation and was followed by a transgressive interglacial record of >600 m of carbonates that terminates in a glacioeustatic unconformity. Overlying this, there are up to 500 m of shale and sandstone interpreted as coeval to global Marinoan glacial advance. Glacial outwash delta deposits at the top of the formation correlate with diamictite-filled paleovalleys and are covered by massive Fe and Mn deposits of the Santa Cruz Formation and local carbonate. This second transgression is related to Marinoan deglaciation. Detrital zircon provenance supports glaciostatic control on Cryogenian sedimentary yield at the margins of the Amazon craton. These findings reveal the sedimentary response to two marked events of glacioeustatic incision and transgression, culminating in massive banded iron deposition during the Marinoan cryochron.

中文翻译:

巴西乌鲁库姆地区的低温冰期和静水波动以及与 Marinoan 相关的大量 Fe 和 Mn 沉积

全球新元古代冰川作用与极端环境变化和岩石记录中铁形成的重现有关。然而,由于对包含铁矿床的低温纪层序缺乏狭窄的年龄限制,因此无法在全球范围内对这些矿床进行关联和了解。我们的新多代理数据揭示了 Jacadigo Group(巴西乌鲁库姆区)跨越 Sturtian 和 Marinoan 冰河时代的长期低温记录。Urucum 组基底层序的沉积受 Sturtian 大陆冰川作用的影响,随后是超过 600 m 的碳酸盐的海进间冰期记录,其终止于冰川不整合面。在此之上,有多达 500 米的页岩和砂岩被解释为与全球 Marinoan 冰川进展同时期。地层顶部的冰川冲刷三角洲沉积物与混积岩填充的古山谷相关,并被圣克鲁斯地层的大量铁和锰沉积物和当地碳酸盐覆盖。第二次海侵与马里诺冰川消退有关。碎屑锆石来源支持对亚马逊克拉通边缘低温纪沉积产量的冰川控制。这些发现揭示了对两个显着的冰川切割和海侵事件的沉积反应,最终导致了在 Marinoan 冰冻年代期间的大量条带状铁沉积。碎屑锆石来源支持对亚马逊克拉通边缘低温纪沉积产量的冰川控制。这些发现揭示了对两个显着的冰川切割和海侵事件的沉积反应,最终导致了在 Marinoan 冰冻年代期间的大量条带状铁沉积。碎屑锆石来源支持对亚马逊克拉通边缘低温纪沉积产量的冰川控制。这些发现揭示了对两个显着的冰川切割和海侵事件的沉积反应,最终导致了在 Marinoan 冰冻年代期间的大量条带状铁沉积。
更新日期:2021-11-23
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