Structure of the Guadalupe Box area, Sandoval County, New Mexico
Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico.
Stratigraphy and regional tectonic implications of part of Upper Cretaceous and Tertiary rocks, east-central San Juan Basin, New Mexico
_ _____--_--_-_____--________________.___ Introduction.___----------_---_-___________________ Previous work__________________________________ Present work-._________________________________ Acknowledgments__ _ __________________________ Physiography __________________________________ Drainage._________________________________ Landf orrns.________________________________ Penistaja Cuestas_____________________ Largo Plains.__________________________ Tapicitos Plateau.______________________ Yeguas Mesas._________________________ San Pedro Foothills.____________________ Northern Hogback Belt_________________ Climate. ____________________________________ Vegetation._---------__-___-___________________ Stratigraphy _______________________________________ Rocks of Cretaceous age_________________________ Mesaverde Group_________________________ Lewis Shale._______________________________ Pictured Cliffs Sandstone.___________________ Fruitland Formation and Kirtland Shale undivided __________________________________ Rocks of Tertiary age.__________________________ Ojo Alamo Sandstone.______________________ Nacimiento Formation. _____________________ San Jose Formation.________________________ Definition___ _ ________________________ Extent and thickness____________________ Lithology_ _____________________________ Cuba Mesa Member._______________ Regina Member.___________________ Llaves Member___________________ Tapicitos Member._________________ Page 1 2 4 4 4 5 5 5 5 7 7 10 10 10 13 13 15 16 21 30 30 35 44 44 45 46 46 48 50 52 Stratigraphy Continued Rocks of Tertiary age Continued San Jose Formation Continued Contacts __ _ ____-_-_-___---_-_------__ Age and correlation___________--__--__Igneous rocks. ___________-____-_--___-_--__ Deposits of Tertiary or Quaternary age highterrace gravel_____-_-_---______-----_-------Deposits of Quaternary age______-___----------__ Terrace gravel, colluvium, and streamchannel gravel. _ _________-__________----_-__--_-_ Alluvium. _________________________________ Geologic structure. _________-__-_-____---__---_-_--Regional setting. _______________________________ Description of structure. ___________-_-_-_-_-_-__ Structure contours. _________________________ Joints. __________________________ Analysis of regional Laramide structure. _____ General problems. ____.____________--Nacimiento fault____________________ Overturned beds__ _ _--___-____--_Synclinal bend_ ______________--_Evidence of strike-slip movement. __ Gallina fault.--. __ -_ ----_--_---San Pedro Mountain fault. _________-_Archuleta anticlinorium. ______________ Salado-Cumbres structural discontinuity. Conclusions. __________-___-_-_____--Summary of depositional and tectonic history Descriptions of type sections. ___________--_ References. _-_________-_-_-------_------Index. _________________-_-----_-_-_---Page
History of nomenclature and stratigraphy of rocks adjacent to the Cretaceous-Tertiary boundary, western San Juan Basin, New Mexico
Dinosaur-bearing shale and sandstone exposed along Ojo Alamo Arroyo in the western part of the San Juan Basin were first called the Ojo Alamo Beds of Cretaceous age in 1910 by Barnum Brown, who wrote that these beds were overlain unconformably by the Puerco Formation of Tertiary age. W. J. Sinclair and Walter Granger differentiated four lithologic units in the ·rocks that had been descri'bed as the Ojo Alamo Beds and lower part of the Puerco Formation by Brown. Their units are, in ascending order: (1) "shales with dinosaurs, lower horizon" (Brown's Ojo Alamo Beds); (2) lower conglomerate; (3) "shales with dinosaurs, upper horizon"; ( 4) conglomeratic sandstone with fossil logs (lower part of Brown's Puerco Formation). Units 1-4 were called the Ojo Alamo Beds by Sinclair and Granger, who reported that unit 4 was overlain unconforma·bly by shale of the Puerco Formation, with the reported unconformity probably marking the boundary between Cretaceous and Tertiary ·rocks. C. M. Bauer assigned the "shales with dinosaurs, lower horizon'' to the upper part of the Kirtland Shale of Cretaceous age and defined the Ojo Alamo Sandstone to include the lower conglomerate, the "shales with dinosaurs, upper horizon" and the conglomeratic sandstone with fossil logs. Bauer reported that the upper dinosaur-bearing shale is a local lens enclosed between the two conglomerates of his Ojo Alamo Sandstone, and he placed the Cretaceous-Tertiary boundary at Sinclair and Granger's reported unconformity between his Ojo Alamo and the Puerco Formation. The dinosaur faunas of the Kirtland Shale and of Bauer's Ojo Alamo Sandstone were considered to be of Montana (Late, but not latest Cretaceous) age by Barnum Brown and C. W. Gilmore. J. B. Reeside, Jr., correlated the uppermost part of Bauer's Kirtland Shale with the McDermott Formation of Cretaceous age and stated that Bauer's Ojo Alamo Sandstone was unconformable with both the underlying McDermott and the overlying Puerco. Reeside assigned the Ojo Alamo Sandstone to the Tertiary(?), although it contained dinosaurs of Late (but not latest) Cretaceous age. Later, Reeside reassigned the Ojo Alamo Sandstone to the Cretaceous. The Puerco and Torrejon Formations in the vicinity of Ojo Alamo ·were distinguished from each other by Sinclair and Granger only on the basis of their early and middle Paleocene mammal faunas. G. G. 'Simpson pointed out that no one has found a lithologic basis for mapping the rocks containing the two faunas as two separate formations. He proposed bhat the rocks containing the Puerco and Torrejon faunas be called, collectively, the Nacimiento Formation, as used by C. H. Dane. 'The present writers found that the upper conglomeratic sandstone of Bauer's Ojo Alamo Sandstone rests on a widespread deeply channeled erosion surface cut in his medial dinosaurbearing shale which is a persistent unit, rather than being a lens as reported by Bauer. The present writers found also that the upper conglomeratic sandstone intertongues with the overlying Nacimiento Formation of Tertiary (Paleocene) age. The dinosaur-bearing medial shale and the lower conglomerate of Bauer's Ojo Alamo Sandstone are here named the Naashoibito Member of the Kirtland Shale of Montana age, because of lithologic and faunal similarity to the Kirtland. The name Ojo Alamo Sandstone is here restri.cted to the upper conglomerate of Bauer's Ojo Alamo. The restricted Ojo Alamo Sandstone is classified as Paleocene because it intertongues with the overlying Nacimiento Formation. Pollen and spore florules from the restricted Ojo Alamo Sandstone and the basal part of the Nacimiento Formation near Barrel Spring are similar, and both florules also are similar to the Ojo Alamo and Nacimiento pollen and ·spore florules of Roger Y. Anderson from the eastern side of the San Juan Basin. The restricted Ojo Alamo Sandstone of the type locality is the Ojo Alamo Sandstone of most other workers in the western, southern, and eastern parts of the Central basin of the San Juan Basin. Throughout this region the Ojo Alamo rests with erosional and regional angular unconformity on rocks of Montana age. This unconformity represents a hiatus during whioch rocks of latest Cretaceous age either were not deposited or were eroded from these parts of the San Juan Basin. The exact position and nature of the Cretaceous-Tertiary boundary in the northern and northeastern parts of the basin have not been