EXTENSION, SEDIMENTATION AND MODIFICATION OF THE GREATER GULF OF MEXICO BASIN

Transcription

1 EXTENSION, SEDIMENTATION AND MODIFICATION OF THE GREATER GULF OF MEXICO BASIN --AND THE PLACE OF THE EAST TEXAS BASIN WITHIN IT Thomas E. Ewing, Frontera Exploration Consultants, San Antonio TX FOR ETGS TECH EXPO, March 2018

2 ABSTRACT The Northern Gulf of Mexico Basin is a complex set of Mesozoic-Cenozoic passive margin basins distinctive for the role of salt-related structuring. The basin formed by two phases of extension: Phase I (Norian-Callovian, Ma) extended continental crust over 200km in a NW-SE direction as North America 'pulled out' of Pangea; Phase II (Oxfordian-Valanginian) created new oceanic crust during a 42 o counterclockwise rotation of Yucatan. Phase I extension has formed the basic structural grain of the northern margins of the basin, including the East Texas - Sabine Uplift area. Northwest-oriented intracontinental transform zones form the northeastern margin of the basin complex, and separate zones within the basin. Stretching left blocks of thick crust surrounded by regions of thin, highly extended crust. The thick-crust blocks became the later 'arches' or 'uplifts' characteristic of the northeastern and western sectors of the Gulf of Mexico Basin, The intervening basins, along with the main Texas-Louisiana-Campeche Basin, probably sank below sea level, may have accumulated Jurassic presalt sediments, and then were covered with salt up to 2km thick during the initial contact of the basin with the world ocean. The East Texas salt basin is a linear NE-trending trough, which once contained thick salt that has now gone into pillows and diapirs. The geometry is quite different from North Louisiana; it may have formed in the lee of the Sabine block as it was pulled relative southeastward. Later modifications include thermal doming in the Cretaceous and Laramide-induced arching in the Eocene. The major Jurassic source rocks of the Gulf basins are at the base of the postrift subsidence, and are matured by further subsidence. Later Cretaceous source rocks (Eagle Ford) are mostly immature in East Texas but mature on the margins of the main Gulf of Mexico basin. The younger Cenozoic shelf-margin succession yields gas and some oil formed during outbuilding of the shelf margin by Cenozoic deltaic progradation.

3 WHAT IS THE GREATER GULF OF MEXICO (GGOM) BASIN? Location: Southern North America and southward to southern Mexico A complex of basins associated with opening of the Gulf of Mexico, Ma Interior basins are failed rifts and their postrift basins Much sedimentation due to filling of Gulf with sediment and subsequent loading In this talk: Northern GGOM only (N of Tampico) is considered.

4 THE GULF OF MEXICO TODAY BATHYMETRY, CRUSTAL BLOCKS; MAYBE OIL AND GAS? Bathymetry and Topography

5 GULF OPENING IN WORLD CONTEXT Triassic 225 Ma Mid-Jurassic 165 Ma Mid-Cretaceous 100 Ma Courtesy of Ian Norton, UTIG / PLATES Project

6 TWO PHASES OF EXTENSION Phase I: ~60 m.y. (~ Ma, Nor-Clv) NW-SE extension; NW-trending linears Thick blocks and thinner extended areas of continental crust in NE Mexico and US Phase II: ~22 m.y. ( Ma, Oxf-Bar) Enhancement of west end of GOM spreading center leads to 42 o rotation of Yucatan Enhanced magma production due to back-arc position Contemporaneous with Border Rift (back-arc)

7 OPENING OF THE GULF OF MEXICO

8 PHASE I: NW-trending transfer zones separate rifts and blocks Pearl River (Florida of Klitgord) Tunica ( Cuban ) SW Sabine Generation of East Texas Trough and North Louisiana extension around Sabine block Freeport (Brazos of Hudec) Frio River zones Mexican linears: La Babia-Zapata, San Marcos-San Carlos, Parras-Galeana Most transfer zones are diffuse and complex

9 GGOM: 220 Ma (the Closed Configuration)

10 CRUST TYPES AND PHASE I LINEARS

11 NAMAG MAGNETIC MAP

12 PHASE 1 EXTENSION: East Texas, North Louisiana Sligo to Gilmer Isopach, from Cicero and Steinhoff (2013)

13 FT WORTH EAST TEXAS SECTION

14 PHASE I EXTENSION: South Texas

15 PHASE I EXTENSION: Linears in Mexico NW zones of translation in Jurassic, rejuvenated in Laramide Ewing, 2011

16 GGOM: 162 Ma (end of crustal extension)

17 EAST TEXAS, ABOUT 170 MA? 170 Ma - Jurassic, Texas Gulf Coast

18 PHASE II: Rotation of Yucatan and seafloor spreading Ocean crust forms at seam generated by Phase I extension More magma produced in western Gulf than in eastern a back-arc effect More crust produced; allows/forces Yucatan to rotate counterclockwise 42 o Transition is same time as Nazas-Border Rift transition at Nazas (Lawton and Molina, 2014)

19 PHASE II EXTENSION: Rotational Spreading VGG Map, Sandwell et al. (2014)

20 PHASE II EXTENSION: Influence from a Mexican arc? Less magma 42 o of rotation Stern and Dickinson, 2010

21 GGOM: 140 Ma (end of ocean opening)

22 NORTHWESTERN GGOM SECTION: Llano Uplift To Perdido Foldbelt Peel et al., 1995, in Ewing 2016

23 NORTHERN GGOM SECTION: Toledo Bend To Sigsbee Escarpment Peel et al., 1995, in Ewing 2016

24 INFILLING SEDIMENTARY SEQUENCES Ewing and Galloway, in prep

25 TEXAS GEOHISTORY, MA 215 Ma Norian (Late Triassic) 162 Ma Callovian (Middle Jurassic) 160 Ma Oxfordian (Late Jurassic) 150 Ma Tithonian (Late Jurassic) 130 Ma Barremian (Early Cretaceous) 120 Ma Aptian (Early Cretaceous) 113 Ma Earliest Albian (Early Cretaceous) 105 Ma Albian (Early Cretaceous) 94 Ma Turonian (Late Cretaceous) Ewing, 2016

26 CRETACEOUS UPLIFTS and IGNEOUS FEATURES IN THE NORTHERN GULF

27 NORTHERN GULF GEOHISTORY, Ma Ewing and Galloway, in prep.

28 JUST ADD HYDROCARBONS

29 GULF COAST / GULF OF MEXICO LOCATION OF SOURCE ROCKS Jurassic source rocks (Smackover, Haynesville, Bossier) deposited at the beginning of the postrift subsidence They are matured by further subsidence. Postmature in large parts of main GOM Cretaceous source rocks (Eagle Ford) deposited late in the postrift subsidence Mature in the main GOM basin, immature on margins Lie near the bottom of the thick sedimentary package in main GOM. Cenozoic source rocks are mostly gas-generative formed during outbuilding of the shelf margin by Cenozoic deltaic progradation, assisted by regional transgressions No cap is present on the basin (except for subsalt plays), and seepage is widespread.

30 SOURCE ROCKS IN THE SEDIMENTARY FILL Ewing and Galloway, in prep

31 PETROLEUM SYSTEMS, NORTHERN GGOM 1) 2) 3) 4) Three main sources, two low in section (Jurassic, mid-cretaceous) Generation continuing at present Repetition of oil window by salt nappe(s) Strong vertical migration, no superseal; leaky basin

32 GULF OF MEXICO SOURCE ROCKS Hood et al., 2002

33 QUESTIONS?

34 REFERENCES Cicero, A.D., and Steinhoff, I., 2013, Sequence stratigraphy and depositional environments of the Haynesville and Bossier shales, east Texas and north Louisiana: in AAPG Memoir 105, p Ewing, T.E., 2011, Tectonic domains in the Rio Grande / Rio Bravo border region, Texas and Mexico: Laramide structures suggest earlier history: GCAGS Transactions v. 61, p Ewing, T.E., 2016, Texas Through Time: Lone Star geology, landscapes and resources. Austin, University of Texas Bureau of Economic Geology Udden Series 6, 431p. Ewing, T.E., and W.E. Galloway, in prep, Evolution of the Northern Gulf of Mexico sedimentary basin: in Basins of North America, 2 nd ed. (A. Miall, ed.). Elsevier Hood, K.C., L.M. Wenger, O.P. Gross and S.C. Harrison, 2002, Hydrocarbon systems analysis of the northern Gulf of Mexico: delineation of hydrocarbon migration pathways using seeps and seismic imaging: in AAPG Studies in Geology 48, p Lawton and Molina, 2014 Peel, F.J., C.J Travis and J.R. Hossack, 1995, Genetic structural provinces and salt tectonics of the Cenozoic offshore U.S. Gulf of Mexico: in AAPG Memoir 65, p Sandwell, D.T., Müller, R.D., Smith, W.H.F., Garcia, E., and Francis, R., 2014, New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure: Science, v.346, p Sawyer, D.S., R.T. Buffler, and R.H. Pilger, Jr., 1991, The crust under the Gulf of Mexico basin; in The Gulf of Mexico Basin. Boulder, Geological Society of America, Geology of North America, v.j, p Stern, R.J., and Dickinson, W.R., 2010, The Gulf of Mexico is a Jurassic backarc basin: Geosphere, v.6, p