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The effect of seasonally reversing monsoons in the northern Indian Ocean is to impart significant changes in surface salinity (SS). Here, we report SS changes during the last 32 kyr in the Lakshadweep Sea (southeastern Arabian Sea) estimated from paired measurements of δ 18 O and sea surface temperature (SST) utilizing Globigerinoides sacculifer, an upper mixed layer dwelling foraminifera. The heaviest δ 18 OG.sacculifer (- 0.07±0.08‰) is recorded between 23 - 15 ka BP, which could be defined as the last glacial maximum (LGM). The δ 18 OG.sacculifer shift between the LGM and Holocene is 2.07 ‰. The SST shows an overall warming of 2 °C from the LGM to Holocene (28 °C to 30 °C). However, coldest SSTs are observed prior to LGM, i.e., ~27 ka BP. The SS was higher (~ 38 psu) throughout most of the recorded last glacial period (32.5 - 15 ka BP). This high salinity together with generally lower SSTs suggests a period of sustained weaker summer or stronger winter monsoons. The deglacial warming is associated with rapid reorganization of monsoons and is reflected in decreased salinity to a modern level of ~ 36.5 psu, within a period of ~ 5 kyr. This indicates intensification of summer monsoons during cold to warm climate transition.

Several generations of sand blows and sand dikes, indicative of significant and recurrent liquefaction, are preserved in the late Holocene alluvial deposits of the Cibao Valley in northern Dominican Republic. The Cibao Valley is structurally controlled by the Septentrional fault, an onshore section of the North American-Caribbean strike-slip plate boundary. The Septentrional fault was previously studied in the central part of the valley, where it sinistrally offsets Holocene terrace risers and soil horizons. In the eastern and western parts of the valley, the Septentrional fault is buried by Holocene alluvial deposits, making direct study of the structure difficult. Liquefaction features that formed in these Holocene deposits as a result of strong ground shaking provide a record of earthquakes in these areas. Liquefaction features in the eastern Cibao Valley indicate that at least one historic earthquake, probably the moment magnitude, M 8, 4 August 1946 event, and two to four prehistoric earthquakes of M 7 to 8 struck this area during the past 1100 yr. The prehistoric earthquakes appear to cluster in time and could have resulted from rupture of the central and eastern sections of the Septentrional fault circa A.D. 1200. Liquefaction features in the western Cibao Valley indicate that one historic earthquake, probably the M 8, 7 May 1842 event, and two prehistoric earthquakes of M 7-8 struck this area during the past 1600 yr. Our findings suggest that rupture of the Septentrional fault circa A.D. 1200 may have extended beyond the central Cibao Valley and generated an earthquake of M 8. Additional information regarding the age and size distribution of liquefaction features is needed to reconstruct the prehistoric earthquake history of Hispaniola and to define the long-term behavior and earthquake potential of faults associated with the North American-Caribbean plate boundary. Manuscript received 6 September 2002.

From abstract: This report is one of a series of publications on the geology and mineral resources of the Appalachian Plateaus. The areas described are the Butler and Zelienople quadrangles, which together include about 450 square miles in Butler, Beaver, and Lawrence Counties, western Pennsylvania.

From abstract: This report is one of a series of publications by the United States Geological Survey on the Appalachian coal, oil, and gas fields. The area described occupies 227 square miles in Allegheny, Butler, and Westmoreland Counties, in western Pennsylvania, immediately north of Pittsburgh.

From abstract: This report briefly describes the geology and mineral resources of the Randolph quadrangle, which covers an area of 892 square miles in northeastern Utah and southwestern Wyoming.