. Maryland geological survey . agoon was silted in more andmore with mud derived from the surrounding basin, the advancing beachcame to rest on this lagoon deposit as a foundation and arrived at lengthat the point where the lagoon had been filled up to the level of wave baseor higher. When this place was reached, another process was added tothat of the beach advance. Heretofore the waves and wind had beensimply pushing forward material over the advancing front, but now that9 130 THE PLIOCENE AND PLEISTOCENE DEPOSITS OF MARYLAND the rrnid deposit in the lagoon had actually reached the level of
. Maryland geological survey . agoon was silted in more andmore with mud derived from the surrounding basin, the advancing beachcame to rest on this lagoon deposit as a foundation and arrived at lengthat the point where the lagoon had been filled up to the level of wave baseor higher. When this place was reached, another process was added tothat of the beach advance. Heretofore the waves and wind had beensimply pushing forward material over the advancing front, but now that9 130 THE PLIOCENE AND PLEISTOCENE DEPOSITS OF MARYLAND the rrnid deposit in the lagoon had actually reached the level of wavework and had transformed the lagoon from a pond to a marsh or meadow,the breakers attacked the upper portion of the lagoon deposit and denudedit down to the level of wave base as rapidly as they could reach it fromunder the superficial veneer of the beach sands. Cypress, ferns, sedges,and other vegetation which had taken up their abode in the marsh wouldbe overwhelmed with detritus by the advancing beach and a little later. Fig. 8.—Diagram showing later stage in advance of Talbot shore-line. ?would be destroyed by the breakers. In this way all traces of life musthave been removed from the deposit except such as happened to occupy aposition lower than wave base. One, therefore, finds preserved in theclay water-logged trunks and leaves, nuts, etc., and roots of huge treeslike the cypress which would tend to sink by their great weight furtherand further down into the soft mud as the trees increased in size. Theareas over which the waves had removed the upper portions of the lagoondeposit can be determined not only by the presence of truncated stumps MARYLAND GEOLOGICAL SURVEY 131 but also by the character of the contact itself (Plate XVI, Fig. 1, andPlate XVII). At this line there is a sharp division between the clayand the overlying sand and gravel while the area over which the beachadvanced without cutting would be indicated by a partial mingling of thebeach material with
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