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sand are often irregularly distributed through the limestone, and fossils, when 

 they do occur, appear to be limited to its basal portions. At Port Willunga 

 jetty, beds of this age occupy an intermediate position between the older marine 

 below, and the Pleistocene clays that overlie them, and slope gradually with the 

 dip to the level of the beach on the southern side of Snapper Point. 



This gradual inclination of the Tertiary beds to the southward brings 

 within reach, in succession, the upper beds and provides good hunting grounds 

 for the fossils of the Upper Marine Series. Many of the forms which are common 

 in the lower marine Tertiary, such as polyzoa, brachiopods, echinodermata, and 

 corals, are almost absent from the newer (Pliocene) Marine Series, but Ostrea 

 arenicola, Tate, is extremely common, many having the two valves attached; 

 Spondylus arenicola, Tate; Pecten antian sir alls, Tate; P. subbifrons, Tate; 

 and Laganimi platymodes, Tate, are characteristic forms and somewhat common. 

 Local silicification has cemented some portions of the matrix, while other parts 

 remain free, and, from this fact, many fossils can be easily cleared of the 

 matrix on one side while firmly held by the silicified rock at another. The 

 thickness of the beds averages about 20 feet. 



The white marly limestone, which forms the upper portions of these beds, 

 comes down to sea level on the southern side of Snapper Point, and exhibits some 

 interesting features. There is a sharp line of separation between the limestone 

 and the fossiliferous beds beneath. The latter have been greatly leached of 

 their lime content and, mostly, retain only external impressions and casts of their 

 organic remains. The composition and structure of the overlying limestone are 

 much in contrast from that of the fossiliferous bed, being often markedly nodular, 

 and the rock contains rounded and angular stones that are foreign to the rock 

 in which they occur. Among these included stones are examples of the fossili- 

 ferous rock on which the limestone rests. There are also in the limestone very 

 curious rope-like forms that are sometimes knotted and twisted, and, when 

 microscopically examined, appear to have a kind of cellular structure. They 

 vary in size from small twigs to large root-like masses, 4 to 5 inches in diameter. 

 These features are very suggestive of a travertine limestone, and, if so, supplies 

 important evidences concerning the hiatus which exists between the marine condi- 

 tions, indicated by the underlying bed, and the mottled clays ( ? Pleistocene) 

 which follow next in the order of succession. When the sea-bed was raised 

 to dry land (given suitable climatic conditions) a travertine would form on its 

 exposed surfaces, as occurs in this country at the present day on all calcareous 

 soils in dry situations, and would account for the leached condition of the fossili- 

 ferous marine bed, the lime having been extracted from such by circulating waters 

 and precipitated as a capping on its upper limits. The inclusion of stones and 

 fossils in the limestone near the plane of junction is what would naturally occur 

 in such a process, and the ropy, stem-like forms, found in certain positions in 

 the limestone, is paralleled by the sand-pipes and stem-casts which are constant 

 features of the surface travertine and calcareous sands at the present time. The 

 removal of the lime from the fossiliferous sands prepared the way for the 

 entrance of silicated waters which, in many instances, have filled up the inter- 

 stices with silica and produced siliceous pseudomorphs of the organic remains. 

 A newer travertine, of Recent age, occurs in the same section near the top of 

 the cliffs. 



On the southern side of Snapper Point the Tertiary limestones make a slight 

 show near the base of the cliffs and occupy most of the beach. They can be 

 traced along the littoral for about a mile from the Point, when they are no 

 longer visible, having dipped below the level of low-water mark. They are 

 not seen again until the wide and open valley of the former Onkaparinga outlet 

 is passed, when they reappear under new stratigraphical features. 



