Textural transition in an aragonite travertine formed under various flow conditions at Pancuran Pitu, Central Java, Indonesia
Textural transition in an aragonite travertine formed under various flow conditions at Pancuran Pitu, Central Java, Indonesia
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DOI：
10.1016/j.sedgeo.2012.04.010
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发表时间：
2012-07-15
影响因子：
2.8
通讯作者：
Kano, Akihiro
中科院分区：
文献类型：
--
作者：
Okumura, Tomoyo;Takashima, Chizuru;Kano, Akihiro
在印度尼西亚中爪哇的潘库兰皮图，一个巨大的石灰华丘，显示出不同类型的层压，反映了不同的水文条件。为了了解层状石灰华的地球微生物过程，我们研究了土丘的水文、水化学、结构、微生物组成和碳酸盐矿物（VPC）的体积百分比。我们确定了四种类型的石灰华：致密石灰华（80% VPC，流速接近200 cm/s），石化微生物石灰华（60% VPC，流速接近70 cm/s），脆弱微生物石灰华（30% VPC，流速接近10 cm/s），以及未石化微生物毡（< 10% VPC，流速小于5 cm/s）。前两种类型表现出规则的亚毫米层压，这与蓝藻和有机物的分布有关。密集的石灰华由结晶层和带状层交替组成，间隔约为160 μ m，类似于日本西南部文石石灰华的日常层压。带状层在白天形成，表现出多孔性，并含有有机物质。石化微生物石灰华中的层压可能是由丝状蓝藻的日常生长周期形成的。白天的石灰华表面是一层亚毫米厚的蓝藻生物膜，上面有文石的球状聚集体，覆盖着一层由放射状扩张的针状晶体组成的结晶层。晶体层很可能是在蓝藻生长中断的夜间形成的。这些有规律的层压石灰华织物似乎与某些前寒武纪叠层石相似。另外两种富微生物类型在低流量部位层压的规律性较差。大多数文石以球形聚集体的形式出现在微生物垫中，尽管脆弱的微生物石灰华中的薄（10-50 μ m）晶体层可能显示出每日的间隔。从文石的VPC、流速和沉淀速率之间的关系可以看出，随着水动力能的增加，碳酸盐沉淀的激活和厚蓝藻生物膜的发育受到抑制，钙华更加固结。(c) 2012 Elsevier B.V.版权所有
A large travertine mound at Pancuran Pitu, Central Java, Indonesia, displays various types of lamination reflecting different hydrological conditions. To understand the geomicrobiological processes of the laminated travertines, we investigated the mound's hydrology, water chemistry, texture, microbial composition, and volume percentage of carbonate mineral (VPC). We identified four types of travertines: dense travertine (80% VPC, flow rate similar to 200 cm/s), lithified microbial travertine (60% VPC, flow rate similar to 70 cm/s), fragile microbial travertine (30% VPC, flow rate similar to 10 cm/s), and poorly lithified microbial mat (< 10% VPC, flow rate < 5 cm/s). The first two types exhibited regular lamination at sub-mm intervals that was associated with the distribution of cyanobacteria and organic substances. The dense travertine consisted of alternation of crystalline and banded layers at similar to 160-mu m intervals, which resembles the daily lamination of an aragonite travertine from southwest Japan. The banded layer formed during the day, exhibited porosity, and contained organic substances. Lamination in the lithified microbial travertine was likely formed by the daily growth cycles of filamentous cyanobacteria. The daytime surface of this travertine appeared to be sub-mm-thick cyanobacterial biofilm with spheroidal aggregates of aragonite, which covered a crystalline layer consisting of radially expanded needle crystals. The crystalline layer was likely formed during the night when the cyanobacterial growth was interrupted. These regularly laminated travertines fabrics appeared to be similar to certain Precambrian stromatolites. Regularity of the lamination was less in the other two microbe-rich types at low-flow sites. The majority of the aragonite occurred as spherical aggregates within the microbial mat, although thin (10-50 mu m) crystal layers in the fragile microbial travertine may indicate daily intervals. As represented in the relationship among the VPC, flow rate, and precipitation rate of aragonite, the travertines were more consolidated with increasing hydrodynamic energy because of the activation of carbonate precipitation and the inhibition of thick cyanobacterial biofilm development. (c) 2012 Elsevier B.V. All rights reserved.