Pebbles overlain

In other parts of the world, a synthetic grass mat has been used to collect current-borne sediments enabling a protective mat of sand to accumulate. In Boa Vista, Cape Verde Islands the natural seabed is composed of water-worn pebbles of volcanic rock. These are easy to handle underwater and a layer of 100 mm pebbles overlain with some well-chosen boulders protects the site from marine and human interference. The insertion of a short tail of orange cord serves as buried marker. It is discrete, moving gently in the current, and to the casual intruder is much like other marine growth and debris. 

Unconsolidated cover at Pebble consists of 0-50 m of a variety of glacial deposits over Pebble West, where the deposit is partially exposed. At Pebble East, the deposit was partially eroded and is unconformably overlain by an eastward thickening wedge of post-mineralization Late Cretaceous to Eocene volcanosedimentary rocks, up to 600 m in thickness, which in turn are overlain by the glacial deposits. 

The Pebble deposit is located in the Kahiltna terrane, near the boundary between two lithologic packages Jurassic and older magmatic-metamorphic rocks to the southeast, and an assemblage of Mesozoic volcaniclastic and sedimentary rocks overlain by Tertiary volcanic rocks, to the northwest. An extended discussion of the regional geology is given in Kelley etal. (this volume). 

The phosphate rock deposits in the Florida region are in the form of small pebbles embedded in a matrix of phosphatic sands and clays [31]. These deposits are overlain with lime... 

The Queen Maud Formation is a coarse grained conglomeratic sandstone that lies unconformably on the rocks of the Weaver Formation. This unit is about 25 m thick and is equivalent to the basal quartz-pebble conglomerate of the Queen Maud Formation on Mt. Weaver. On Tillite Ridge in the Wisconsin Range the Queen Maud Formation is overlain by indurated till more than 30 m thick. This till is probably of Pleistocene or even of Pliocene age and thus is one of the many late Cenozoic glacial deposits in theTransantarctic Mountains that are collectively included in the Sirius Group. 

The site comprises a sequence of beds from the Grahamstown Lake Formation of late Carboniferous/ early Permian age (Ofifler et al, 1974). The section exposed in the quarry consists of 3 beds a very thick (>20 m) bed of conglomerate, overlain by a thin unit ( 4 m) of shaley and pebbly tuff, and then by a thick (>20 m) layer of daeitie ignimbrite. 

Paleoseismic Trenching, Fig. 7 Earthquake indicators used in the identification of paleo-events. On-fault structures (a) upward termination of a fault, which is overlain by undeformed stratum (b) difference in thickness of strata at each side of the fault and downward growth of the displacement along the fault trace (c) scarp-derived colluvium (d) formation of monoclinal folding, where fast sedimentation covers the fault scarp (e) open surface cracks, infilled with material of the overlying unit (f) disordered pebbles covered by undeformed layer, and (g) sheared layer covered with unsheared one. Off-fault structures ... 

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