deposits coupled with extensive radiocarbon dating can clarify the late Qua- 

 ternary marine sequence in the Gulf of Mexico, and will eventually allow more 

 satisfactory interpretations on a global basis. (Author). 



275 PORTER, S. C, STUVIER, M. , and HEUSSER, C. J. 1984. "Holocene Sea- 

 Level Changes Along the Strait of Magellan and Beagle Channel, Southernmost 

 South America," Quaternary Research . Vol 22, pp 59-67. 



Radiocarbon-dated marine sediments from five coastal sites along the 

 Strait of Magellan and Beagle Channel in southernmost Chile permit construc- 

 tion of a curve of relative sea- level fluctuations during the Holocene. 

 Morphologic and stratigraphic data point to coastal submergence during the 

 early Holocene as the sea rose to a maximum level at least 3.5m higher than 

 present about 5000 year ago. Progressive emergence then followed during the 

 late Holocene. Data from widely separated localities define a smooth curve, 

 the form of which is explainable in terms of isostatic and hydroisostatic 

 deformation of the crust resulting from changing ice and water loads. Appar- 

 ently anomalous data from one site located more than 100 km behind the outer 

 limit of the last glaciation may reflect isostatic response to deglaciation. 

 The sea-level curve resembles one derived by Clark and Bloom (1979) (Modified 

 Abstract) . 



276 POSAMENTIER, H. W. , JERVEY, M. T., and VAIL, P. R. 1988. "Eustatic 

 Controls on Clastic Deposition I - Conceptual Framework,' Wilgus, C. K. , 

 Hastings, B. S., Kendall, C. G., Posamentier, H. W. , Ross, C. A., and Van 

 Wagoner, J. C, eds . , Sea-Level Changes: An Integrated Approach . Special 

 Publication No. 42, Society of Economic Paleontologists and Mineralogists, 

 Tulsa, OK, pp 109-124. 



A conceptual framework for understanding the effects of eustatic control 

 on depositional stratal patterns is presented. Eustatic changes result in a 

 succession of systems tracts that combine to form sequences deposited between 

 eustatic-f all inflection points. Two types of sequences have been recognized: 

 (1) a type 1 sequence, which is bounded at the base by a type 1 unconformity 

 and at the tippee by either a type 1 or type 2 unconformity and has lowstand 

 deposits at its base, and (2) a type 2 sequence, which is bounded at the base 

 by a type 2 unconformity and at the top by either a type 1 or type 2 

 unconformity and has no lowstand deposits. Each sequence is composed of three 

 systems tracts; the type 1 sequence is composed of lowstand, transgressive- , 

 and highstand systems tract, and the type 2 sequence is composed of shelf - 

 margin, transgressive, and highstand systems tracts. The type 1 sequence is 

 associated with stream rejuvenation and incision at its base, whereas the type 

 2 sequence is not. 



Eustacy and subsidence combine to make the space available for sediment 

 to fill. The results of this changing accommodation are the onlapping and 

 of flapping depositional stratal patterns observed on basin margins. Locally, 

 conditions of subsidence and/or uplift and sediment supply may overprint but 

 usually will not mask the effects of global sea-level. Any eustatic 

 variation, however, (e.g., irregular eustatic rise or fall, asymmetric fall, 



' . 126 . ■ 



