The trace fossils Rhizocorallium is abundant in the Upper Devonian Wangguangou Formation in Xichuan, southwestern Henan Province.It consists of U-shape spreite burrows and more or less parallel or slight incline to the bedding of marling limestone.Scanning electron microscope images show that abundant pyrite and iron framboids (iron framboids were mostly oxygenated from pyrite framboids) were found within the Rhizocorallium burrow, including (pyritohedral, octahedron, cube and nearly spherical and irregular shape).No similar framboids were observed outside Rhizocorallium except a few single pyrite crystals.Most of iron framboids were sheathed within the Rhizocorallium burrow.At the same time, the diameter of the submicron crystals in the marginal tube (0.672~1.603 μm, the average diameter of is 1.063 μm) was bigger than that in the spreite (0.376~0.877 μm, the average diameter is 0.5 μm).Therefore, it is likely that sulphate-reducing bacteria colonized the Rhizocorallium spreite and marginal tube within a dysoxic environment.The results indicated that Rhizocorallium would represent a burrow for multifunctional purpose, where the trace maker has utilized available conditions (such as substrate type, food supply, dysoxic to oxic environment) for cultivation of microbes.%豫西南淅川上泥盆统王冠组地层中发育大量与层面平行且具有蹼纹的U形遗迹化石Rhizocorallium.利用环境扫描电镜对Rhizocorallium进行微观观察,发现在其边缘管和蹼纹内部发育大量不同形态的莓状黄铁矿及莓状铁氧化物(单晶为五角十二面体,八面体,立方体和近球形),与之对应的围岩中仅见少量黄铁矿单晶颗粒.表面具有覆盖膜的莓状黄铁矿大多存在于潜穴内部,其中边缘管中莓状黄铁矿的单晶直径(0.672~1.603 μm,平均直径1.063 μm)较之蹼纹中部的(0.376~0.877 μm,平均直径0.5 μm)的大.上述特征显示出潜穴中莓状黄铁矿的存在可能与硫酸盐类还原菌有关.Rhizocorallium边缘管和蹼纹中高丰度莓状黄铁矿的发现表明:遗迹化石Rhizocorallium可能是造迹者精心构筑的觅食-花园.由于食物供应和氧化还原条件的不同,Rhizocorallium造迹者在其潜穴内部培植不同的微生物,形成一个互利共生的群落.
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