Carbonate sediments reflect the physico-chemical and biological circumstances of their formation; thus, features of limestones and dolomites may provide insights into both environmental and evolutionary change through geological time. The Upper Proterozoic (approx 800-700 Ma) Akademikerbreen Group, Spitsbergen, comprises 2000 m of carbonates, with only minor intercalations of quartz arenite and shale. Although Proterozoic carbonates are often seen as predominantly dolomitic, the Akademikerbreen Group is about 45 percent limestone. Stromatolites are conspicuous in outcrop but constitute only 25 percent of the total section. Micrites and coarser intraclastic carbonates derived mainly from micritric precursors comprise 60 percent of the group, while oolites make up the remaining 15 percent. Distinctive sedimentary features of the group include giant (up to 16 mm) ooids, very early diagenetic calcite nodules and cements, micrites containing subaqueous shrinkage cracks filled with equant microspar cement, and strong 13C enrichment in both carbonates and co-occurring organic matter. The principal features of Akademikerbreen carbonates are widely distributed in coeval successions. However, these rocks appear to differ from older limestones and dolomites in their relative abundance of grainstones and, perhaps, micrites, as well as their paucity of tufa-like laminates and columnar or coniform stromatolites that preserve petrographic evidence of in situ precipitation as a dominant means of carbonate accretion. Upper Proterozoic carbonates also differ from Paleozoic accumulations, but the transition is not abrupt. Most changes accompanying the Proterozoic/Phanerozoic transition can be interpreted in terms of the consequences rather than the causes of metazoan and metaphyte evolution, including the evolution of biomineralization. Carbonate sedimentology reinforces data from other sources which indicate the last 200 to 300 Ma of the Proterozoic Eon was a distinctive interval of Earth history.

中文翻译：

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晚元古代的碳酸盐沉积：以斯匹次卑尔根为例。

碳酸盐沉积物反映了其形成的物理化学和生物学环境。因此，石灰岩和白云岩的特征可以提供有关地质时期环境和演化变化的见解。斯匹次卑尔根的上元古代（大约800-700 Ma）的Akademikerbreen组包含2000 m的碳酸盐，只有少量的石英砂岩和页岩夹层。尽管通常认为元古代碳酸盐岩主要为白云岩，但Akademikerbreen集团的石灰岩含量约为45％。露头石在露头中很明显，但仅占总断面的25％。主要来自微晶前体的微晶岩和较粗的碎屑碳酸盐占该组的60％，而橄榄石占其余的15％。该组的独特沉积特征包括巨大的卵石（最大16毫米），非常早的成岩方解石结节和胶结物，含有水下收缩裂缝的微晶石，并填充有相当数量的微晶石胶结物，以及碳酸盐和共生有机物中的13C富集。Akademikerbreen碳酸盐的主要特征广泛分布于近代。但是，这些岩石似乎与较老的石灰岩和白云岩在相对丰富的花岗石和微晶石以及稀有的类似石灰岩的层压板和柱状或圆锥形叠层石方面有所不同，这些岩石学证据保留了原位降水的优势。碳酸盐增加的手段。上元古界的碳酸盐也与古生界的储集层不同，但转变并不突然。伴随元古生代/杂生代转变的大多数变化都可以用后果来解释，而不是用后生动物和植物的演化原因，包括生物矿化的演化来解释。碳酸盐沉积学强化了其他来源的数据，这些数据表明，元古代的最后200至300 Ma是地球历史的一个独特间隔。