. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 3] ORGANIC TRANSPORTATION OF MARINE SEDIMENTS 777 first, the holdfast can break off and hft part of the bottom and the plant be set adrift. If one plant drifts against another, the combined pull of both may break the second one loose, finally tearing open a wide swath through a kelp bed. The anchor, buoyed by the plant, may be floated away from the kelp bed (Fig. 1), occasionally touching or dragging on the bottom to form markings which in geological strata sometimes have mistakenly been identified as plant. Fig. 1.
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 3] ORGANIC TRANSPORTATION OF MARINE SEDIMENTS 777 first, the holdfast can break off and hft part of the bottom and the plant be set adrift. If one plant drifts against another, the combined pull of both may break the second one loose, finally tearing open a wide swath through a kelp bed. The anchor, buoyed by the plant, may be floated away from the kelp bed (Fig. 1), occasionally touching or dragging on the bottom to form markings which in geological strata sometimes have mistakenly been identified as plant. Fig. 1. Two kelp holdfasts {Macrocystis pyrifera) afloat in 25 m depth off Coronado Islands, Mexico. Largest is about 40 cm long and both consist of probable Middle Miocene sandstone and conglomerate. Note that intermittent touching of the bottom can produce holes and other markings on the sand. ( Navj^ photograph by R. F. Dill.) impressions. Most of the rocks are drifted inshore, as shown by the fact that beaches near kelp beds usually contain many rocks having remnants of hold- fasts and encrustations of calcareous red algae, bryozoans, rock oysters, and other organisms which live below the low tide level (Emery and Tschudy, 1941), Single rocks rafted to beaches by kelp weigh as much as 10 kg, and one holdfast was found to contain an estimated 25,000 pebbles and granules coarser than one millimeter in diameter. Some plants also float seaward where masses of the larger ones have been. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hill, M. N. (Maurice Neville), 1919-. New York : Interscience Pub.
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