Abstract We cannot hope to predict Mesozoic depositional processes and sediment properties well enough to plan effective regional exploration strategies without considering the big picture of Gulf of Mexico deposystem evolution. The two critical big picture elements are the kinematics and timing of the Yucatan Block's detachment and separation from North America and the various major expansions and contractions and the ultimate disappearance of the Western Interior Seaway. Although a number of authors, including this one, have speculated on the timing of separation of Yucatan from North America ( Fillon, 2007a ), no definitive evidence exists: i.e. , drilled samples of the ocean crust and the sediments directly overlying it. Without that unambiguous information we must infer the paleogeographic evolution of the early Gulf of Mexico Basin from deposystem architecture by asking questions such as when do Gulf of Mexico deposystems transition from architectures consistent with deposition in a youthful blockfaulted basin underlain by actively attenuating continental crust to deposition in a mature basin having stable margins surrounding a central region underlain by subsiding ocean crust. An understanding of the paleogeography and paleoceanography of the Gulf of Mexico Basin derived from deposystem architecture can help provide answers to crustal kinematic questions and to more exploration focused questions such as: where, and in section of what age should we look to find facies similar to the organic rich, generative Haynesville Shale facies of eastern Texas and western Louisiana. Although we all know something about the Western Interior Seaway, most of us working on the Mesozoic of the Gulf of Mexico Basin have not spent much time considering what effects it might have had on the prospectivity of Gulf of Mexico deposystems. Through much of Albian and Late Cretaceous time the Western Interior Seaway connected the Gulf of Mexico Basin with the Arctic Ocean Basin. The effects of the establishment and intermittent blocking of this major seaway connecting arctic and tropical water masses on global paleoceanography, on global paleoenvironments, and locally on onshore and offshore Gulf Basin deposystems cannot be ignored in our quest to understand the Mesozoic of the Gulf Rim. This paper is a “big picture” review of Gulf of Mexico Basin deposystem evolution within the Late Jurassic (Oxfordian)–Late Cretaceous (Maastrichtian) interval. Seventeen Mesozoic chronosequences are defined therein based on chronostratigraphic data garnered from over 130,000 industry well and pseudowell penetrations of Mesozoic section in the Gulf of Mexico Basin region. Examination of the collected data suggests that grouping the seventeen Gulf of Mexico Mesozoic chronosequences into seven super-chronose-quences optimally distinguishes key phases of deposystem and basin evolution. The oldest super-chronosequence defined in this study, dubbed “MG,” encompasses ca. 16.45 Ma of Norphlet through lowermost Cotton Valley Late Jurassic deposition. Sediment distribution and accumulation rates within the MG interval clearly define the rectilinear configuration of the earliest Gulf of Mexico Basin. This early basin geometry is consistent with fault controlled attenuation and foundering of North American continental crust, associated flooding, and rapid depositional infill concurrent with the earliest detachment of the Mayan (Yucatan) crustal block from North America. The Yucatan block, although showing an affinity with South American (Amazonian) terranes ( Martens, 2009 ), was left attached to the North American plate when North America began pulling away from Gondwana during the initial breakup of Pangea ( Fillon, 2007a ). The next younger super-chronosequence, “MF,” contains a. ca. 13.47 Ma record of Cotton Valley, Bossier, Knowles limestone., Late Tithonian through mid Hauterivian, deposition. The “MF” interval reflects the same rectilinear outline as the “MG,” but is marked by decreased accumulation rates, suggesting that the fault bounded crustal attenuation, rapid sediment infill phase had markedly slowed. The ca. 9.4 Ma of Hosston, Sligo, Sunniland limestone, James limestone, mid-Hauterivian through Early Aptian section contained within the succeeding “ME” super-chronosequence records modification of the early rectilinear basin outline by a temporary reactivation of attenuation and foundering in the western portion of the Gulf of Mexico Basin. “ME” sediment distribution patterns also indicate development of a depositional continental margin and accumulation of true continental margin type deltaic and reef systems. These observations suggest that during this interval a deep continental basin, probably floored by ocean crust, was beginning to form outboard of the attenuated continental crust. Sediment distribution and accumulation rates within the ca. 23.5 Ma Rodessa through lower Washita, Early Aptian through Early Cenomanian “MD” super-chronosequence reflect growth of the Wisconsin interior seaway and a stable phase of relatively low accumulation rates throughout the entire Gulf of Mexico Basin deposystem. During this interval, deposition was very likely influenced by a vigorous tidal and thermohaline current circulation driven by strong temperature contrasts within the Gulf of Mexico–Wisconsin interior seaway–Arctic Ocean connection. The next younger super-chronosequence, “MC,” contains a ca. ca. 16.0 Ma record of Dantzler, Washita, Lower Pine Key, Eutaw, Woodbine, Eagle Ford, Austin, and Early Cenomanian through Late Santonian (Late Cretaceous) deposition. During this phase, there is a marked reduction of accumulation rates in the north-western portion of the basin, attributable perhaps to expansion of the Western interior seaway and continued subsidence of the old Gulf of Mexico Basin margin. Associated small, perhaps tidal submarine delta-like depopods developed, perhaps in response to the regional Western interior seaway transgression ( Blakey, 2014 ). These delta-like depocenters appear to define a new basin margin presaging the modern curved shape of western Gulf of Mexico so familiar to us today. Here also we see the first unambiguous evidence of abyssal deposition in the deepest portion of the Gulf of Mexico Basin underlain by ocean crust. The succeeding ca. 12.82 Ma interval of Late Santonian through Early Maastrichtian upper Pine Key, upper Selma, upper Austin, Taylor, Olmos, Saratoga, and low accumulation rate mainly chalk and marl deposition contained within the “MB” super-chronosequence provides evidence of transgressive onlap associated with an expanding and deepening interior seaway during “MB” time. “MB” onlap has the effect of temporarily reemphasizing structural trends inherited from crustal attenuation that took place during “ME” time. Finally, the ca. 5.4 Ma long terminal Mesozoic “MA” super-chronosequence consists of Maastrichtian, Navarro equivalent, low accumulation rate marls deposited along the basin margin. These low accumulation rate basin rim sediments and low accumulation rate slope sediments are punctuated by high accumulation rate canyon fill and lobe-shaped slope depopods which are probably attributable to sediment reworking, transport and deposition by transitional Cretaceous-Paleogene (K/P) interval mega-tsunami backwash flows immediately following the Chicxulub impact. Higher accumulation rates in the deeper parts of the basin underlain by ocean crust are also consistent with high volume backwash flows.

Prior to the early 1990s, nearly all surface faults recognized in south Louisiana were faults of the Baton Rouge system. Since then, the number of surface fault traces interpreted in the region has increased dramatically, owing to a combination of (1) application of traditional analysis of cues on topographic maps and aerial- photographic imagery over increasingly large areas, particularly in southwest Louisiana, (2) the employment of geophysical surveying techniques in the Holocene delta plain where surface scarp relief is negligible, and (3) the advent of light detection and ranging (LiDAR) digital elevation models (DEMs). Like faults of the Baton Rouge system, newly recognized surface faults of the Tepetate system show distinctive depth-displacement relations in Quaternary and pre-Quaternary strata indicating that they are active and are the surface expressions of deep-subsurface older Cenozoic growth faults that have been reactivated following extended periods of quiescence. The differential displacement of older relative to younger Pleistocene terrace surfaces characteristic of individual Tepetate–Baton Rouge system faults also characterizes surface faults of the other systems, suggesting they may share similar movement histories. Commonplace recognition of active surface faults throughout south Louisiana now suggests that many of the known deep-subsurface growth-fault systems have surface expression reflecting their reactivation in the late Cenozoic. The recently amplified picture of surface faulting in this region highlights an important aspect of coastal tectonics in the northern Gulf of Mexico setting, and can provide useful constraints for modeling tectonics in this and other coastal settings characterized by reactivation of growth faults following lengthy intervals of quiescence.

Abstract The petroleum geology of the Mississippi Canyon, Atwater Valley, western DeSoto and western Lloyd Ridge protraction areas, offshore northern Gulf of Mexico, is controlled by the interaction of salt tectonics and high sedimentation rate during the Neogene, and has resulted resulting in a complex distribution of reservoirs and traps. Seventy-eight fields/discoveries are evaluated and comprise structures with four-way closures (18), three-way closures (46), and stratigraphic traps (14). Three of these discoveries are in Upper Jurassic eolian reservoirs, the remainder are in Neogene deep-water reservoirs. The tectonic-stratigraphic evolution of the area is analyzed at eleven discrete intervals between 24 Ma and Present. The analyses show how the allochthonous salt systems evolved over time, and their effect on sedimentation patterns and sub-basin evolution. The study area includes some of the largest fields in the northern deep Gulf of Mexico. Thunder Horse produces from an anticlinal (turtle) structure that developed with a basement-controlled allochthonous system. The greater Mars-Ursa sub-basin has nine fields with > 1.5 BBBOE EUR, including Mars, Ursa and Princess, that developed with a counterregional allochthonous salt system. The remaining fields have considerably smaller reserves, which are controlled by the area within closure and number of reservoir intervals. Many of the smaller fields are produced from one well subsea tiebacks. Most of fields in the study area are contained within sheet-like or wedge-shaped stratigraphic intervals and have four-way or three-way trapping configurations. These findings reflect the profound effect that mobile salt has had on the petroleum geology of the region.