THE WEST POINT, TEXAS, SALT DOME 659 



Below the Gulf series of the Upper Cretaceous come the Washita, 

 Fredericksburg, and Trinity groups of the Comanchean, but it 

 would probably require a well more than 3,500 feet deep to reach 

 the uppermost of these formations on the West Point dome. 



There is no information regarding the dome material, the salt, 

 gypsums, or limestones of secondary origin, other than the report 

 that rock salt was found at a depth of 300 feet and penetrated to a 

 depth of some 700 feet in the well drilled at Llewellyn Gin. It is 

 not known whether or not there is a cap rock present over the salt. 



Structurally this dome is very symmetrical, as is indicated by 

 the dip of the outcropping formations. From one's general knowl- 

 edge of salt-dome structure he would suspect that the upper part 

 of the salt mass, the intrusion of which gives rise to this structure, 

 has the form of a very regular truncated cone. The very steep 

 dips and outcrop of the older shale (Midway?) formation south- 

 west of Llewellyn Gin indicate that the southwestern edge of the 

 dome is the point of greatest upthrust and consequently the point 

 where the salt lies at the shallowest depth from the surface. The 

 upthrust in this dome has been 800 to i ,000 feet. 



The rocks over the top of the salt mass are probably level- 

 lying or nearly so. Around the perimeter the dips are very high, 

 25°-8o°, and away from the center of the dome. They decrease 

 rapidly as one goes away from the dome. 



Only the central part of the area affected by the uplift of this 

 dome is shown on the attached map. The entire uplift doubtless 

 has a diameter of 3 to 4 miles and an area of 7 to 1 2 square miles. 



AGE OF DOME FORMATION 



The Mount Selman beds of lowest Claiborne (Eocene) age, and 

 the youngest rocks outcropping in this immediate region, dip away 

 from the West Point dome in all directions. Since these beds were 

 involved in the folding which resulted from the formation of this 

 dome, it is evident that the intrusion of the salt mass was not 

 completed before early Claiborne time and the entire process may 

 have occurred at some period since then and down to quite recent 

 time. In fact, the formation of this and similar domes may be a 

 very slow and continuous process now going on. 



