The stratigraphic and paleoenvironmental significance of the regressive Monte Observación Member, Early Miocene of the Austral Basin, Patagonia
The stratigraphic and paleoenvironmental significance of the regressive Monte Observación Member, Early Miocene of the Austral Basin, Patagonia
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巴塔哥尼亚南方盆地早中新世海退Monte Observación 段的地层和古环境意义
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发表时间：
2019
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通讯作者：
J. Cuitiño
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作者：
Ana Parras;J. Cuitiño
巴塔哥尼亚南部渐新世-中新世海相沉积的地层学已被广泛讨论。然而，Monte Observacion成员(MOM)的定义并不明确，与其边界、分布、岩性和沉积古环境有关的许多方面仍不确定。本文介绍了对圣克鲁斯省南部大西洋海岸(南方-马格伦盆地)几个早中新世露头的实地调查结果。沉积学分析确定了研究层的6个相组合：FA-1对应于陆棚-下滨相沉积，FA-2对应于前三角洲-远三角洲前缘沉积，FA-3对应于近端三角洲-前缘沉积，FA-4对应于三角洲平原的末端分流河道和曲流河道，FA-5对应于分流间海湾和潮坪；化石浓度的分析可以确定三种主要成因类型：生物型、沉积型和生物-沉积型混合型。边缘海洋牡蛎Crassostreorbignyi(Ihering)是一种典型的过渡性沉积物中重要的无脊椎动物化石，也是最后一种受海洋影响的无脊椎动物。沉积学和生物成因-沉积学混合浓度表现出不同的属性和证据，表明不同过程的作用，包括主要是单一的栖息地内重新加工的浓度，很少有后现代干扰多个特定的浓度带有不同的挖掘过程的印记。FAs的分布表明，一个海退系统，以三角洲沉积体系的形式进积陆架沉积，具有潮汐影响。这一分析可以更好地确定MOM，因为它表明：1)零到很低的生物扰动程度；2)原生无脊椎动物动物群含量减少；3)交替岩性给出了良好的层状格局；4)丰富的灰色到绿色砂岩夹层。MOM的快速积累可能是由于早中新世巴塔哥尼亚安第斯山脉南部快速折返产生的硅质碎屑和火山碎屑进入南方盆地的高峰，这将是蒙特莱昂建造退化期的一部分。
The stratigraphy of the Oligocene-Miocene southern Patagonia marine deposits has been extensively discussed. However, the Monte Observacion Member (MOM) was vaguely defined and many aspects related to its boundaries, distribution, lithology and paleoenvironments of deposition remain uncertain.In this paper we present results obtained from the field survey of several early Miocene outcrops exposed along the Atlantic coast of southern Santa Cruz Province (Austral-Magallanes Basin). They correspond to the transitional interval between the marine shelf Monte Leon Formation and the terrestrial Santa Cruz Formation.Sedimentological analysis allowed to define six Facies Associations (FAs) for the studied beds: FA-1 corresponds to inner shelf to lower shoreface deposits; FA-2 corresponds to prodelta to distal delta-front deposits; FA-3 corresponds to proximal delta-front deposits; FA-4 corresponds to terminal distributary channels and meandering channels in the delta plain; FA-5 corresponds to inter-distributary bays and tidal flats; and finally FA-6 corresponds to the upper delta plain deposits.In turn, analysis of fossil concentrations allowed defining three main genetic types: biogenic, sedimentologic, and mixed biogenic-sedimentologic concentrations. Biogenic concentrations are represented by beds and lenses of the marginal marine oyster Crassostreaorbignyi (Ihering), which is a significant fossil invertebrate typical of the transitional deposits and is the last invertebrate showing marine influence in all the studied sections and beyond.Sedimentologic and mixed biogenic-sedimentologic concentrations exhibit different attributes and evidence the action of different process, including from mostly monospecific within-habitat reworked concentrations, with little post-morten disturbance to polyspecificconcentrations bearing the imprint of various taphonomic processes.The distribution of FAs suggest a regressive system that prograded over shelf deposits in the form of deltaic depositional systems with tidal influence. This analysis allowed to define better the MOM because it shows: 1) null to very low bioturbation degrees; 2) a reduced autochthonous invertebrate faunal content; 3) a well stratified pattern given by the alternating lithologies; and 4) abundant decimetric intercalations of gray to greenish sandstone beds.The fast accumulation of the MOM,which would be part of the regressive phase of the Monte Leon Formation,could be the consequence of a peak of siliciclastic and volcaniclastic input into the Austral Basin, produced as a result of rapid exhumation in Southern Patagonian Andes during the early Miocene.
早期中新世圣克鲁斯地层（阿根廷南方麦哲伦盆地）的古土壤和相关土壤生物群：重建古代陆地景观的多学科方法
影响因子：
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作者：
Raigemborn, Maria Sol;Krapovickas, Veronica;Zucol, Alejandro F;Zapata, Luciano;Beilinson, Elisa;Toledo, Nestor;Perry, Jonathan;Lizzoli, Sabrina;Martegani, Lucia;Tineo, David E
通讯作者：
Tineo, David E