THE STRUCTURAL EVOLUTION OF THE GOLDEN LANE, TAMPICO EMBAYMENT, MEXICO

Abstract

The Golden Lane oilfields of Mexico will always hold a place of prominence in the annals of petroleum geology. The most prolific oil‐well ever drilled, Cerro Azul No. 4, was one of a string of wildcats which defined a Cretaceous carbonate ridge that lay buried below gently‐dipping Neogene clastics on the Tampico coastal plain. Continued drilling showed that the buried ridge had an arcuate shape, and this led to the interpretation that the feature was a Lower Cretaceous reef. When the Poza Rica “giant” was discovered in detrital Cretaceous limestones west of the ridge, these were naturally considered to be forereef talus. Later drilling offshore discovered another string of Cretaceous carbonate traps which joined the onshore fields to complete the circlet that became renowned as the “Golden Lane atoll.”An abundance of rudists in Cretaceous reservoirs of the Golden Lane and Poza Rica gave rise to the concept of the rudist reef build‐up. A presumed analogue for the rudist reef of the Golden Lane was discovered in Lower Cretaceous rudistid limestones exposed at Sierra El Abra, NW of the oilfields. The foregoing interpretation has become entrenched in geological literature, even though an integrated structural‐stratigraphic synthesis of the Golden Lane is lacking.Time‐stratigraphic control of Cretaceous formations in the Tampico embayment is complicated by scarcity of documented marker fossils, and confused by the common occurrence of reworked detritus. It is ussumed herein that Cretaceous volcanicity in the Tampico embayment, as in the Gulf of Mexico generally, commenced in the Late Cenomanian. From this, it is concluded that much of the Golden Lane and Poza Rica reservoir sequences in which bentonite layers occur are of Late Cretaceous age. The El Abra outcrops, on the other hand, are undoubtedly Early Cretaceous. Structural analyses show that the Golden Lane area has an active and complex structural history. Strong faulting along NE‐SW trends was active in Late Cretaceous time, giving rise to syntectonic débris flows. At the same time, a major positive feature developed to the east in the Gulf of Mexico.By Middle Eocene time, the Gurf of Mexico positive was stripped‐down to metaphoric basement and subsequently collapsed as regional extension sundered the basement and allowed the injection of oceanic crust. A salt basin formed during the Oligocene eustatic low‐stand. Cretaceous carbonates of the Golden Lane were incorporated in a westward‐plunging synform in pre‐Oligocene time, but thereafter were rotated by regional downwarping into the Gurf of Mexico. In Holocene time, the synform was inverted, and these latest stresses were accompanied by injection of numerous dykes and plugs that cut the Golden Lane.From, this structural and stratigraphic synthesis, it is concluded that the Golden Lane anomaly is the product of a complex sequence of post‐Lower Cretaceous structural events. It is bounded on the west by a buried Middle Eocene fault, and on the east by a Neogene growth fault, and is not a Lower Cretaceous carbonate build‐up.