. Calvert county. Geology. 118 THE GEOLOGY OF CALVERT COUNTY the level of wave-base or higher. When this place was reached another process was added to that of beach andvance. Heretofore the waves and wind had been simply pushing forward material over the advancing front but now the mud deposit in the lagoon had actually reached the level of wave-work and had transformed the lagoon from a pond to a marsh or to a meadow, the breakers attacked the upper portion of the lagoon deposit and eroded it down to the level of wave-base as rapidly as they could reach it from under the superficial veneer o
. Calvert county. Geology. 118 THE GEOLOGY OF CALVERT COUNTY the level of wave-base or higher. When this place was reached another process was added to that of beach andvance. Heretofore the waves and wind had been simply pushing forward material over the advancing front but now the mud deposit in the lagoon had actually reached the level of wave-work and had transformed the lagoon from a pond to a marsh or to a meadow, the breakers attacked the upper portion of the lagoon deposit and eroded it down to the level of wave-base as rapidly as they could reach it from under the superficial veneer of the beach-sands. Cypress, cat-tails, sedges, and other vegetation which had taken up their abode in the marsh would be overwhelmed with detritus by the advancing beach and a little later be destroyed by the breakers. In this way all traces of life must be removed from the deposit except such as happened to B ^^ __^ ..^^ -_^. Fig. 7.—Ideal section showing advance of Talbot shore-line. occupy a position lower than wave-base. One, therefore, finds preserved in the clay water-logged trunks and leaves, nuts, etc., and roots of huge trees like the cypress. The area over which the waves had removed the upper portions of the lagoon deposit can be determined not only by the presence of truncated stumps but also by the character of the contact. Here there is a sharp division between the clay and the overlying sand and gravel while the area over which the beach advanced without cutting would be indicated by a partial mingling of the beach material with lagoon mud. A still later stage in the process is illustrated in the accompanying diagram (Fig. 6) which represents a stage where the waves have so far advanced as to largely destroy the original stream channel. A small portion of the old lagoon still exists at the head of the swamp but its lower portions have long since been submerged and covered over by the. Please note that these images are extracted from scanned page images that may
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