PALEOCENE / EOCENE POLLEN ASSEMBLAGES FROM THE LIGORIO MÁRQUEZ FORMATION , CENTRAL PATAGONIA , XI REGION , CHILE
PALEOCENE / EOCENE POLLEN ASSEMBLAGES FROM THE LIGORIO MÁRQUEZ FORMATION , CENTRAL PATAGONIA , XI REGION , CHILE
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发表时间：
2006
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影响因子：
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通讯作者：
M. Okuda;H. Nishida;K. Uemura;Atsushi Yabe
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作者：
M. Okuda;H. Nishida;K. Uemura;Atsushi Yabe
智利XI地区(智利巴塔哥尼亚中部)的Ligorio Márquez组(Suárez等人，2000)是古近纪/始新世的河流-沼泽起源。该地层厚度不超过60m，由煤层和洪泛平原沉积组成，具有丰富的植物化石，是试图了解南美洲南部早第三纪植物群和气候历史的焦点。这项孢粉学研究的目的是确认Nothofagus花粉的存在或不存在，并重建Ligorio Márquez组的孢粉植物群。对这一问题的考虑始于一份初步的花粉报告(Yoshida，1990)，该报告表明存在温带分类群，如Nothofagus和Podocarpaceae，这与同一组中已知的热带/亚热带巨藻不一致(Suárez等人，2000年)。如果吉田(1990)的假说是正确的，他将重新组织智利奇科南部第三纪的古植物群和/或年代学框架，以便与由所谓的新生代气候最佳时期衍生的晚古新世/早始新世的区域超级热带气候相协调(例如Bowen等人，2004；Svensen等人，2004)。从自然地理上讲，巴塔哥尼亚中部(包括米纳·利戈里奥·马尔克斯地区)对于了解诺索法格斯通过贡多纳大陆迁徙的历史至关重要。Nothofagus(或Nothofagaceae)最早出现于晚白垩世，并在第三纪向赤道扩展。巴塔哥尼亚中部的Nothofagus记录(约40°S)始于始新世晚期(见Tanai，1986；Uemura，1990)，许多记录只包含零碎的花粉证据，需要系统的花粉分析和植物大化石挖掘相结合，以获得更可靠的Nothofagus历史文件。Yoshida(1990)的花粉证据表明，根据总共815个孢粉计数，存在Nothofagidites、Podocarpidites和Myrtaceidites。虽然吉田(1990)没有注意到准确的采样层位，但他的材料是基于Mina Ligorio Márquez第二层的岩石(图1，2)。特隆科索等人。然而，(2002)指出，吉田(1990)的花粉和孢子组合在组成和特征花粉种类上与它们的分析结果不同，并建议吉田的组合的年龄更早。为了确认这些问题，我们对Ligorio Márquez组进行了重新采样，加强了对地层的控制。特别是(1)对来自不同相的数十个层位进行了多次分析；(2)提供了一个岩性柱和采样层位的描述。还应该指出的是，植物巨型化石的挖掘和年龄确定是由合著者同时进行的(见Terada等人，2006年；Yabe等人，两者都在本卷中)，从而产生了多重代理分析方法。
The Ligorio Márquez Formation (Suárez et al., 2000) in the XI region of Chile (Chilean central Patagonia) is of fluvial to backmarsh origins of the Paleogene/Eocene. This strata is no more than 60 m thick and is composed of coal seams and flood plain deposits with abundant plant fossils, which have been the focus of attention in attempting to understand the floristic and climate history of southern South America during the early Tertiary period. The purpose of this palynological research is to confirm the presence or absence of Nothofagus pollen and to reconstruct the palynoflora of the Ligorio Márquez Formation. The consideration of this matter originated with a preliminary pollen report (Yoshida, 1990) suggesting the presence of temperate taxa such as Nothofagus and Podocarpaceae, which was inconsistent with the known tropical/subtropical megaflora from the same Formation (Suárez et al., 2000). Yoshida’s (1990) hypothesis, if he was right, would reorganise the paleofloral and/or chronological frameworks during the Tertiary period south of Chile Chico, in order to reconcile with regional supertropical climate of the Late-Paleocene/Early-Eocene derived from the so-called Cenozoic Climate Optimum (e.g. Bowen et al., 2004; Svensen et al., 2004). Phytogeographically, central Patagonia (which includes the Mina Ligorio Márquez area) is vital to an understanding of the history of Nothofagus migration through the Gondowana continent. Nothofagus (or Nothofagaceae) first appeared during the late Cretaceous period, and expanded toward the equator through the Tertiary period. Nothofagus records in central Patagonia (ca. 40°S) started in the late Eocene (see Tanai, 1986; Uemura, 1990) and many of the records consisted of only fragmentary pollen evidence, requiring a combination of systematic pollen analyses and plant megafossil excavations to obtain a more reliable documentation of Nothofagus history. The pollen evidence derived by Yoshida (1990) showed the presence of Nothofagidites, Podocarpidites and Myrtaceidites based on a total of 815 counts of sporopollen. Although Yoshida(1990) did not noted the precise sampling horizon, his material was based on rocks from the layer 2 at Mina Ligorio Márquez (Figs. 1, 2). Troncoso et al. (2002), however, pointed out that Yoshida’s (1990) pollen and spores assemblage differ in composition and characteristic pollen species from those of their analysis, and suggested a yonger age for Yoshida’s assemblage. In order to confirm these matters, we carried out a resampling with greater stratigraphic control of the Ligorio Márquez Formation. In particular (1) multiple analyses for tens of horizons from different facies and (2) a lithological column with descriptions of sampled horizons were presented. It should also be noted that a plant megafossil excavation and age determination were performed in parallel by the coauthors (see Terada et al., 2006; Yabe et al., both in this volume), resulting in a multiproxy analytical approach.