Upper Devonian carbonates deposited through the Frasnian/Famennian (F/F) stage boundary in the Xom Nha Formation, Central Vietnam, were studied. The section is mainly composed of fossiliferous, brecciated, and laminated limestone beds, while shale beds occur in a subordinate number. Microfacies generally suggests a hemipelagic setting on an outer shelf environment with low sedimentation rates. A sediment accumulation rate of 0.217 cm/kyrs for this section is calculated. The Xom Nha section does not exhibit characteristic black shales or black limestones through the F/F boundary, but instead shows a similar lithology in comparison to other F/F sections in Southeast Asia. The carbonates yielded abundant conodonts, which represent mainly cosmopolitan species but the section differs from most sections in Europe in showing relatively high numbers of Palmatolepis linguiformis species. Deposition through the F/F boundary interval reported here for the Xom Nha section appears to have occurred during a ~1.2 Ma, and shows well-defined climate cyclicity.

研究了通过位于越南中部 Xom Nha 组的 Frasnian/Famennian (F/F) 阶段边界沉积的上泥盆纪碳酸盐岩。该剖面主要由化石层、角砾岩层和层状灰岩层组成，页岩层次之。微相通常表明位于外陆架环境中沉积速率低的半远洋环境。计算出该部分的沉积物堆积率为 0.217 cm/kyrs。Xom Nha 剖面没有通过 F/F 边界表现出特征性的黑色页岩或黑色石灰岩，而是与东南亚其他 F/F 剖面相比显示出相似的岩性。碳酸盐岩产生了丰富的牙形石，主要代表世界性物种，但该部分与欧洲的大多数部分不同，显示出相对较高的数量Palmatolepis linguiformis种。通过此处报告的 Xom Nha 剖面的 F/F 边界区间的沉积似乎发生在 ~1.2 Ma 期间，并显示出明确定义的气候周期性。