14 CALIK*)UNIA At'ADKMY OK SCIENCES. 



.">. l*M<H"i:XK. 

 Diiidtniin Isldiid. — Ovorly iiij; llic Minct'iie sIiaK' of Deatliiiaii Isliiiid (xee 

 tliiij;rani />', IM. XXII) is a lU-posit of hrowii, clayey saiulstoiu', varyin<; in tiiiok- 

 iiess from twoiity to forty-five feet. 'Piic (li.>«tiiict strata of this formation will l)o 

 tlescribed iii tletjiil. Tlie surface of jointed sliale on wliicli the sandstone rests is 

 worn and uneven, hut the contact conforms nearly to the dip of the shale, wliieh is 

 between 'JO and oU northeast. Other evidence hesidc the worn condition of the 

 shnles at the contact goes to show that the erosion took place while the shales formed 

 the sea bottom near the shore. Worm horin<i;s are common, and in one place a 

 pholas hole was found in the sliale. The contact stratum, which is only aliout a foot 

 thick, is composed almost wholly of hoach-worn pebbles of the Miocene shale, all 

 containing to some extent holes of worms and mollusks. It contains also many well 

 preserved shells and shell fragments. All of the fossils common in this layer are 

 found in the sandstone just above it, so its fauna will he taken up with that of the 

 overlying sandstf>nc in a later part of this paper. 



This Ixtltom riiocene layer dips northeast at an angle of about 25°. Towards 

 the top of the formation the bedding planes become more nearly horizontal, those at 

 tlie top having a dip of only 8" or 10°. This could be accounted for in one of two 

 way.s — cither the lowest layer was deposited horizontally and then during the deposi- 

 tion of the subsequent layers there was a gradual uplift toward the southwest, or else 

 the lowest layer was deposited on a sloping bottom, and the general tendency of 

 sediments to settle in the lower portions of their basins and to form horizontal beds 

 gradually overcame the dip. 



About eight feet of fine, brownish yellow, clayey sand rests on the pebbly low- 

 e.st Pliocene stratum. In some of the places exposed to the action of the sea-water 

 this second Pliocene stratum consists of bluish gray clay, and in some places is filled 

 with well preserved fossils. In the .southwest corner of the island the second layer 

 is a hard, fine, brown sandstone containing onh' a few fossils. 



Overlying the second stratum is a fine, dark brown sandstone about four feet 

 thick. The most fossiliferous places are hard, but porous. The fos.sils in these hard 

 places are well preserved, while those in the softer parts of the layer, which is lighter 

 colored, are poorly preserved and fragile. Pieces of the hard portions of the Plio- 

 cene stratum have broken ofT and have fallen araong the fragments of shale along the 

 beach. This has caused some people to report the fossils found in this Pliocene bed 

 as occurring in the Miocene shale. On account of the great abundance of llujasira 

 ( Cryptodon ) hisecta in this stratum it has been given the local name of "Cryptodon 

 bed." Lucina ncuiilineata is also very common in the Cryptodon stratum. 



Above this very fossiliferous stratum is a bed of browMi .sandstone from twenty- 

 five to thirty-five feet in thicknes.s, only slightly laminated, and varying somewhat in 

 structure and appearance in different parts of the layer. The lower part is uni- 

 formly soft, while toward the top the color is lighter and the rock much harder. 

 Only a few fossils, such as Lucina acuti/ineatn and Pecten caurlnus, have been found 

 in the upper brown sandstone stratum. The total thickness of the Pliocene beds at 

 Deadman Island is about fortv-five feet. 



