Jose F. Longoria

Chapter 5 Stratigraphic evidence for northwest to southeast tectonic transport of jurassic terranes in central Mexico and the caribbean (western Cuba)

Abstaract Jurassic and Early Cretaceous stratigraphic data from terranes in Central Mexico situated southwest of the Walper Megashear demonstrate similar records of paleobathymetry and tectonic transport. In general, each of these terranes shows the same paleobathymetric fingerprint: (1) marine deposition at inner neritic depths during the Callovian to early Oxfordian (Middle to Late Jurassic); (2) marine deposition at outer neritic depths during the late Oxfordian (Late Jurassic); (3) sudden deepening to bathyal or upper abyssal depths (ACD = aragonite compensation level) from the early Kimmeridgian (Late Jurassic) until the end of the Cretaceous. This paleobathymetric fingerprint differs markedly from that occurring to the east-northeast of the Walper Megashear in the Coahuiltecano terrane (emended herein: Sierra Madre Oriental terrane). In the Coahuiltecano terrane (e.g., Peregrina Canyon near C. Victoria, Tamps.), no Mesozoic marine deposits older than late Oxfordian occur. The paleobathymetric fingerprint of this terrane was (1) inner neritic during the late Oxfordian (Late Jurassic) to Barremian (Early Cretaceous) and (2) bathyal to abyssal during the remainder of the Cretaceous (Aptian to Maastrichtian). Though varying in detail, each succession that has been examined in the mosaic of suspect terranes to the southwest of the Walper Megashear shows evidence of tectonic transport from higher latitudes to lower latitudes during the late Middle Jurassic, the Late Jurassic, and the Early Cretaceous. For example, the paleolatitudinal signature of the San Pedro del Gallo terrane (Durango) supplied by faunal data (radiolarians and megafossils) and preliminary paleomagnetic data indicates that this terrane was transported tectonically from higher paleolatitudes (Southern Boreal Province: 40°N) during the Late Jurassic (Oxfordian) to lower paleolatitudes (Tethyan Realm: Northern Tethyan Province) by the Early Cretaceous (Berriasian). The Jurassic and Lower Cretaceous successions at Mazapil (Zacatecas), Sierra de la Caja (Zacatecas), Sierra de Zuloaga (Zacatecas), Symon (Durango), and Sierra de Catorce (San Luis Potosi) are all genetically related to that at San Pedro del Gallo. They are regarded as representing dismembered remnants of the San Pedro del Gallo terrane. Faunal data (radiolarians and megafossils) from the Mazapil succession (Sierra Santa Rosa) indicate that this remnant of the San Pedro del Gallo terrane was situated at Southern Boreal paleolatitudes (>30°N) during the Oxfordian and Kimmeridgian and at Northern Tethyan paleolatitudes (22 to 29°N) during the Tithonian and Berriasian. Preliminary paleomagnetic data from the upper Tithonian to Berriasian part of the Mazapil succession indicates 25°N. Farther to the southeast (San Luis Potosi, Hidalgo, Veracruz, Puebla) in the Huayacocotla segment of the Sierra Madre Oriental, previous investigations indicate tectonic transport from Southern Boreal paleolatitudes (>30°N) during the Callovian to Northern Tethyan paleolatitudes (22° to 29°N) during the Kimmeridgian and Tithonian and to Central Tethyan paleolatitudes ( Jurassic and Early Cretaceous successions in western Cuba (Sierra del Rosario and Sierra de los Organos, Pinar del Rio Province) show lithostratigraphic, paleobathymetric, and paleolatitudinal signatures which are nearly identical to those of San Pedro del Gallo terrane remnants in central Mexico. They clearly represent portions of the North American Plate and are treated as remnants of the San Pedro del Gallo terrane herein. The Cuban remnants of the San Pedro del Gallo terrane were carried to eastern Yucatan by the Walper Megashear. By the Middle Cretaceous terrane amalgamation had occurred between the San Pedro del Gallo and Coahuiltecana terranes and all movement along the Walper Megashear had ceased. Subsequent southwest to northeast movement of the Caribbean Plate during the Late Cretaceous and Early Tertiary bulldozed the Cuban remnants of the San Pedro del Gallo terrane into their present position. Once the Cuban San Pedro del Gallo remnants were carried northward by the advancing Caribbean Plate, it is likely that they became part of an Atlantic-type margin.

Stratigraphy and structure of the Lower Cretaceous of Lampazos, Sonora, (northwest Mexico) and its relationship to the Gulf Coast succession

The stratigraphy and structure of the Lower Cretaceous (Aptian-Albian) rocks exposed in the area of Lampazos, Sonora, are redefined and correlated to well-known stratigraphic successions of Chihuahua and northeast Mexico (Coahuila and Nuevo Leon). Originally, seven stratigraphic units were proposed for the Cretaceous rocks exposed in the Lampazos area, but in this article only five units (El Aliso, Agua Salada, Lampazos, Espinazo del Diablo, and Los Picachos formations) have been used, and we propose herein to discontinue usage of the other two (Nogal and La Mesa formations). This Aptian-Albian succession of east-central Sonora yields facies and fossil content remarkably similar to coeval sequences in the Gulf of Mexico realm (Chihuahua, Coahuila, and Nuevo Leon). These sections contain abundant microfossils (benthic and planktonic foraminifera, colomiellids, nannoconids, and radiolarians) that permit detailed biostratigraphic determinations. A complete Aptian-lower Albian section (base of K-6 through top of K-15 of the biochronologic scheme of Longoria, 1984) was identified. Abrupt lithic changes through the Aptian-Albian section of Lampazos revealed three major paleoceanographic events having an overall regional marine transgression, including an early Aptian (K-6 to K-7) event, a late Aptian (K-10 to K-11) event, and an early Albian (K-13 to K-14) maximum flooding phase. We used physical and biochronologic data to tie the aforementioned events to geochemically constrained Aptian-Albian oceanic anoxic events (OAEs) in Santa Rosa Canyon of Nuevo Leon. The close correlation between the oceanic events in east Sonora (northwest Mexico) and central Nuevo Leon (northeast Mexico) invokes the closer paleogeographic development of the two regions and undoubtedly links the area of Lampazos to a rapid encroachment of the paleo-Gulf of Mexico through north-central Mexico (the Mexican Sea) into northwestern Mexico (Chihuahua trough and Sonoran basin). The early Aptian (biozones K-6 to K-7) transgression has its maximum extension during the early Albian (biozones K-13 to K-14), culminating with the drowning of the carbonate platforms. The Lower Cretaceous rocks exposed in the Lampazos area are complexly folded and faulted. The more conspicuous structures are isoclinal and box-shaped folds and thrust faults, mostly oriented north-south and northwest-southeast, having vergences to both the northeast and southwest. A very conspicuous feature is the opposite vergence of thrust faults, either converging or diverging. Two dextral strike-slip faults (northeast-southwest and east-west) separate the area into three large blocks that have different patterns of folds and thrust faults. Also, it is evident that the area was affected by at least two episodes of normal faulting. Furthermore, the structural style of deformation present in the Lampazos succession is remarkably similar to the style of deformation of coeval rocks in northeastern Mexico, especially to the structure of the Chihuahua tectonic belt. The Lampazos succession is paleogeographically and tectonically related to the Chihuahua tectonic belt, and it is considered to be the westernmost extension of the ancestral Gulf of Mexico. The fact that the Lampazos succession can be lithocorrelated to known sequences in northeastern Chihuahua (Lucero, Ahumada, and Loma Plata formations) and northeast Mexico (Cupido, San Angel, La Pena, and Tamaulipas formations), which are know to be source rocks in exploration wells in Nuevo Leon and Coahuila, makes the Lampazos area of Sonora potentially attractive as an exploration target.

Tectonic Transpression in Northeastern Mexico: Its Relation to Sea-Floor Spreading in Gulf of Mexico: ABSTRACT

The visual analysis of the SIR-A images (Shuttle Imaging Radar) of the folded belt located between Saltillo, Coahuila, and Galeana, in northeastern Mexico, revealed the existence of several geologic features including: (1) a well-developed pattern of en echelon folds, (2) juxtaposition of tectono-stratigraphic domains, (3) fold structures ranging from fan-shaped asymmetric to recumbent doubly plunging anticlines, and (4) anticlinal-synclinal trends displaying marked morphologic variations, associated to regional plunging, twisting, and tilting of the structures. These structures are interpreted as the result of transpressive forces related to a complex, anastomosed wrench-faulting system in the basement, reactivated in the Late Jurassic during active sea-floor spreading i the Gulf of Mexico. The Saltillo-Galeana orogenic belt is interpreted as the early Tertiary culmination of an ancient Mesozoic (Jurassic and Cretaceous) transpressive deformation generated from an oblique-slip mobile zone in the Gulf of Mexico. This transpressive tectonic model gives the adequate paleogeographic scenario to integrate all previously postulated, apparently incompatible, deformational models for northeastern Mexico, and conciliates the differences in fold vergences observed in the region. End_of_Article - Last_Page 1426------------