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Septarian concretions (or septarian nodules) are carbonate-rich concretions containing angular cavities or cracks (septaria; sg. septarium, from the Latin septum "partition, separating element", referring to the cracks or cavities separating polygonal blocks of hardened material).
Nodule is also used for widely scattered concretionary lumps of manganese, cobalt, iron, and nickel found on the floors of the world's oceans. This is especially true of manganese nodules. Manganese and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are concretions instead of nodules ...
During the Triassic, central Virginia was a rift basin. [1] Brachiopods were still present in Virginia during the Mesozoic. [4] On land, the early Mesozoic plants of Virginia included Equisetales, gymnosperms, Cycadeles, cycads, and conifers. This flora is almost identical to that from contemporary deposits in North Carolina. [4]
The geology of Virginia began to form at least 1.8 billion years ago. The oldest rocks in the state were metamorphosed during the Grenville orogeny , a mountain-building event beginning 1.2 billion years ago in the Proterozoic , which obscured older rocks.
Mazon Creek flora includes: lycopsids, related to modern club moss, with arborescent forms named Lepidophloios, Sigillaria and Lepidodendron, and herbaceous forms called Lycopodites and Cormophyton; sphenopsids like Calamites a tree-like horsetail relative, with common foliage names of Annularia and Asterophyllites, and a vine-like form called ...
The sedimentary walls of the crater progressively slumped in, widened the crater, and formed a layer of huge blocks on the floor of the ring-like trough. The slump blocks were then covered with the rubble or breccia. The entire bolide event, from initial impact to the termination of breccia deposition, lasted only a few hours or days.
Sedimentary structures include all kinds of features in sediments and sedimentary rocks, formed at the time of deposition.. Sediments and sedimentary rocks are characterized by bedding, which occurs when layers of sediment, with different particle sizes are deposited on top of each other. [1]
Large septarian concretions, produced by microbial activity (oxidation of organic matter) in the ancient seafloor during clay early diagenesis, are also common. These have been used in the past for making cement.