the relations between marsh vertical accretion rates and sea-level rise in a 

 relatively small geographic area. Estuarine marshes, occurring along the 

 meanders in the sediment trap portions of major Bay tributaries, appear at 

 least to be keeping abreast of rising sea-levels. In some marshes, vertical 

 accretion rates may be exceeding local rates of sea-level rise. Although 

 little data are presently available on the actual processes in these marshes, 

 the increased sediment yield of the estuaries following European settlement, 

 probably has helped maintain the accretionary balance with respect to 

 sea-level rise. 



The other general type of Chesapeake Bay marsh, submerged upland 

 marshes, may be experiencing an accretionary deficit. These marshes, formed 

 by the gradual submergence of low- lying terraces on the Delmarva mainland, are 

 often characterized by large interior ponds. Studies at Blackwater Wildlife 

 Refuge on Maryland's Eastern Shore, where dramatic losses of marsh from pond 

 enlargement have occurred, indicate that local marshes are not maintaining 

 elevation with sea-level rise. Low vertical accretion rates of these and 

 possibly other submerged upland marshes is a function of the reliance on peat 

 deposition as the primary mechanism of accretion. The physiological conse- 

 quence of increasing marsh submergence is a decline in marsh production 

 leading to the disintegration of the peat material, and eventually to the 

 formation of interior ponds which enlarge with time. (Modified Abstract). 



165 KELLER, G., HERBERT, T., DORSEY. R. , D'HONDT, S., JOHNSON, M. and CHI, 

 W.R. 1987. "Global Distribution of Late Paleogene Hiatuses," Geology . 

 Vol 15, pp 199-203. 



Six global late Paleogene hiatuses )PHa to PHe ) have been identified 

 from deep-sea sequences. These hiatuses occurred at the middle/late Eocene 

 boundary, late Eocene, Eocene/Oligocene boundary, late early Oligocene, late 

 Oligocene, and Oligocene/Miocene boundary horizons. 



Paleodepth distribution of hiatuses shows hiatus maxima characterized by 

 major mechanical erosion below 4800 m, at mid-depth between 2000 and 3000 m, 

 and in shallower water suggest that flow paths of major water masses and 

 currents are the principal cause. Wide spread short hiatuses due to carbonate 

 dissolution or nondeposition occurred primarily during global cooling trends 

 or climatic instability and appear to correlate to sea- level transgressions or 

 onlap sequences. These hiatuses may have been caused by basin-shelf 

 fractionation of carbonates. (Authors). 



166 KELLETAT, D. 1988. "Zonality of Modern Coastal Processes and Sea-Level 

 Indicators," Palaeogeography. Palaeoclimatology . Palaeoecolopy . pp 219-230. 



Unlike textbooks on inland geomorphology , most of those on coastal 

 geomorphology give the impression that the formation of the coasts is 

 influenced by processed that are azonal or ubiquitous. Based on quite wide- 

 ranging field studies all over Europe, North Africa, the Middle East, North 

 America, Australia and New Zealand some deductions are presented which in 

 several ways indicate that coastal formation is subject to zonal dynamics. As 

 indicators of the presently active processes a variety of minor forms can be 



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