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首页> 外文期刊>Facies >Three-dimensional burrow systems and taphofacies in shallowing-upward parasequences, lower Jurassic carbonate platform (Calcari Grigi, Southern Alps, Italy)
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Three-dimensional burrow systems and taphofacies in shallowing-upward parasequences, lower Jurassic carbonate platform (Calcari Grigi, Southern Alps, Italy)

机译：浅层-向上副层序，下部侏罗系碳酸盐台地中的三维洞穴系统和塔基相（意大利南部阿尔卑斯山的卡萨里格里吉）

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Analysis of parasequences of carbonate platform origin from the Calcari Grigi Formation (Rotzo Member, Lower Jurassic) in the Venetian Pre-Alps of Northern Italy reveals intense burrowing affecting warm lagoonal and protected shelf environments of the Trento carbonate platform. The trace fossil pattern suggests a strong biogenic activity by many unknown organisms (episodic surficial bioturbation) and by decapod crustaceans (deep burrowing) during the Sinemurian—Pliensbachian. Burrow networks ofThalassinoides (T. suevicus, type I to IV) andOphiomorpha form three-dimensional systems (3DBS), up to 150 cm in thickness, that reveal well developed taphonomic characteristics. Occasionally, also rare body fossil remains (exuvia) ofPhlyctisoma (Erymidae) are preserved, although it is very difficult to attribute to this decapod crustacean a real tracemaker activity. In a total of 18 shallowing-upward taphosequences, each 2.3–2.6 m in thickness, the lower, subtidal part (BOP: base of parasequence), is invariably characterized by 3DBS. Three parts of a 3DBS are taphonomically relevant: a) the enlargement at bifurcation points (the so-called turning chambers) with related tunnel sections in horizontal networks; b) the distribution of vertical tunnels and their openings, locally associated with biogenic mounds; and c) the infilling with coarse-grained skeletal debris of abandoned burrows (tubular tempestites). Case (a), although well known in the literature, is nevertheless peculiar because of the exceptional diameter (up to 22 cm) and shape of bifurcations ofThalassinoides suevicus. Therefore their taphonomic analysis helps to refine shallowing-upward taphosequences. Case (b) and (c), instead, are exceptional because traces of the activity of decapod crustaceans at the sea-floor are very rare in the geologic record. The 3DBS involve taphofacies that are peculiar of the upper part of the Calcari Grigi across western Venetian Prealps. The analysis of 3DBS in all Lower Jurassic para-sequences will aid sequence stratigraphy and the paleoenvironmental reconstruction of the carbonate platform setting.
机译：对意大利北部威尼斯人前阿尔卑斯山Calcari Grigi组（下侏罗统Rotzo成员）的碳酸盐台地副层序的分析显示，强烈的洞穴活动影响了特伦托碳酸盐台地的温暖泻湖和受保护的陆架环境。痕迹化石模式表明，在Sinemurian-Pliensbachian时期，许多未知生物（周期性的表面生物扰动）和十足类甲壳动物（深穴）具有很强的生物活性。拟南芥（T. suevicus，I至IV型）和麦冬的洞穴网络形成了厚度达150 cm的三维系统（3DBS），显示出发达的胶束特性。有时，尽管很难将这种鳞足甲壳动物归因于真正的示踪者活动，但仍保留了Phlyctisoma（Erymidae）的稀有化石遗体（exuvia）。在总共18个浅向上的自斜序中，每一个的厚度为2.3-2.6 m，下部的潮下部分（BOP：准序列的底部）始终以3DBS为特征。 3DBS的三个部分在理论上是相关的：a）在分叉点（所谓的转向室）处的扩大以及水平网络中相关的隧道截面； b）与生土丘局部相关的垂直隧道及其开口的分布； c）用废弃的洞穴（管状的狂暴者）的粗粒骨骼碎片填充。案例（a）尽管在文献中广为人知，但由于其独特的直径（最大22厘米）和拟南芥的分叉形状而特别。因此，他们的离子色谱分析有助于完善浅层向上的离子色谱序列。相反，情况（b）和（c）例外，因为在地质记录中很少发现十足纲甲壳类动物在海底活动的痕迹。 3DBS涉及横穿威尼斯西部前阿尔卑斯山脉的Calcari Grigi上部特有的茶花。在所有下侏罗纪副层序中对3DBS的分析将有助于层序地层学和碳酸盐台地环境的古环境重建。

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