Vb THE PLIOCENE AND PLEISTOCENE DEPOSITS OF MARYLAND 



ward across Maryland, the District of Columbia, Delaware, Pennsylvania, 

 and New Jersey to Earitan Bay, they are divisible into four formations, 

 corresponding with the terraces previously described, which have been 

 called, beginning with the oldest, the Lafayette, Sunderland, Wicomico, 

 and Talbot. If the deposits now forming beneath the surface and along 

 the shores of Chesapeake and Delaware Bays and the Atlantic Ocean 

 are taken into consideration, they will form a fifth formation which is 

 known as the Eecent. The formations are developed one above the other 

 in distinct terraces as earlier described, the oldest lying topographically 

 highest and the others respectively lower in order of their age. These 

 terrace-formations will now be discussed, beginning with the oldest. 



THE PLIOCENE PEEIOD. 



The only formation which has been referred to this period within the 

 State of Maryland is the Lafayette. Its age has long been in doubt and 

 there is not yet sufficient data to correlate it definitely with any period. All 

 that can be said is that it is younger than the Miocene which it covers 

 and older than the oldest Pleistocene beds found in the same vicinity. 

 Within this region no fossils have been found and elsewhere the fossil 

 plants and animals alleged to have been discovered within the Lafayette 

 are not of a character sufficiently definite to determine its age. It is, 

 however, certain that, after the deposition of the Miocene beds, there was 

 a long interval of erosion before deposition of the Lafayette beds began. 

 Likewise, at the close of Lafayette deposition, another long period of 

 erosion occurred before the Columbia deposits which are of Pleistocene 

 age were laid down. The Lafayette formation thus occupies a strati- 

 graphic position between the youngest known Miocene and the oldest 

 known Pleistocene in the vicinity and is separated from each by a long 

 period during which erosion was in progress. These facts, together with 

 the absence of any undoubted Pliocene deposits in this region, have led to 

 the reference of the Lafayette formation to the latter period. This is, 

 however, only a provisional correlation and more positive evidence is 

 needed before the question can be regarded as settled. 



