BP Gulf of Mexico Neogene Astronomically-tuned Time Scale BP Gulf of Mexico Neogene Astronomically- tuned Time Scale (BP GNATTS) J.A. Bergen1, S. Truax III2, E. de Kaenel3, S. Blair4, E. Browning5,†, J. Lundquist6, T. Boesiger7, M. Bolivar5, and K. Clark5 1Paleo at the Hill Country, Brenham, Texas 77833, USA 2Houston, Texas 77070, USA 3DeKaenel Paleo Research, Mont-sur-Rolle, Switzerland 4Blair Biostratigraphy, Cypress, Texas 77429, USA 5BP America, 200 Westlake Park Blvd., Houston, Texas 77079, USA 6Lundquist Stratigraphic, LLC, Houston, Texas 77065, USA 7Nebraska Oil and Gas Conservation Commission, Sidney, Nebraska 69162, USA ABSTRACT This step change in Neogene resolution, now sponse to exploration focus (Martin, 2013). To- at the level of cyclostratigraphy (the orbital day, planktonic foraminifera and nannofossils This paper introduces an integrated Neo- periodic ity of eccentricity) and the magneto- are the primary groups used for time correla- gene microfossil biostratigraphic chart de- stratigraphic chron, demonstrates the poten- tion in deep water wells and the construction of veloped within post-merger BP for the Gulf tial for calcareous microfossil biostratigraphy global Cenozoic timescales. Integrated Gulf of of Mexico Basin and is the first published to more consistently reinforce correlations of Mexico (GoM) industrial biostratigraphies and industrial framework “fully-tuned” to or- these time scale parameters. The integration published global biozonations utilizing these bital periodicities. Astronomical-tuning was of microfossil disciplines, consistent taxono- two planktonic groups date back half a century, accomplished through a 15-year research mies, and rigorous analytical methodologies near the inception of a research coring program program on the Ocean Drilling Program’s are all critical to obtaining and reproducing in the world’s deep-sea basins (Deep Sea Drill- (ODP) Leg 154 sediments (offshore NE Bra- this new level of biostratigraphic resolution. ing Project). During this time, many industrial zil) with sampling resolution for calcareous staffs dedicated to the GoM developed their own nannofossils and planktonic foraminifera INTRODUCTION internal Cenozoic biostratigraphic frameworks. ~20 k.y. and 40 k.y. (thousand year), respec- The Deep Sea Drilling Project (DSDP) was later tively. This framework extends from the Late Microfossils are an important, arguably inte- rebranded the Ocean Drilling Program (ODP) in Oligocene (25.05 Ma) to Recent at an aver- gral tool in subsurface petroleum exploration. 1983 and the Integrated Ocean Drilling Program age Chart Horizon resolution for the Neo- Conventional exploration has reached into new (IODP) from 2003 to 2013. gene of 144 k.y., approximately double that regions and basins, while further development Low oil prices from the mid-1980s through of published Gulf of Mexico biostratigraphic takes place in stratigraphically- and structurally- most of the 1990s impacted specialties such charts and a fivefold increase over the high- complicated fields with increased requirements as biostratigraphy. Maintenance of taxonomic est resolution global calcareous microfossil for finer correlation in reservoir intervals (i.e., concepts and methodologies were challenged biozonation. Such resolution approximates the need for increased resolution in the expanded in this business environment. Foraminiferal and that of fourth to fifth order parasequences sections that are typically targeted in offshore nannofossil taxonomic equivalency projects and is a critical component in the verification exploration). Application of published Cenozoic were formed through the Gulf Coast section of of seismic correlations between mini-basins global biozonations (Blow, 1969; Martini, 1971; the Society for Sedimentary Geology (SEPM) in the deep-water Gulf of Mexico. Its utility Okada and Bukry, 1980) in deep-water explora- amidst concerns about biostratigraphic data and in global time-scale construction and correla- tion was not ideal, especially with the combined terminologies (Picou et al., 1999). Around this tion has been proven, in part, by application effects produced by sediment dilution on micro- time, Shell (Styzen, 1996) and Texaco (Law- of the scheme in full to internal research for fossil recovery, different taxonomic concepts, less et al., 1997) published their GoM Ceno- the Oligocene–Miocene boundary interval and varied methodologies. This necessitated zoic charts. The post-Eocene Shell Offshore on the global boundary stratotype section improvement beyond published global bio zona- Inc. biozonation established separate enumera- and point (GSSP) in northern Italy and off- tions and stimulated petroleum companies to tions for surfaces represented by the tops of shore wells in the eastern Mediterranean Sea. support research that improved their biostrati- nannofossils and combined benthic-plank- graphic databases and frameworks. tonic forami nif era events (Neogene resolution †Corresponding author e-mail: emily .browning@ The first industrial applications of micro- 307 k.y.) and was related to the time scale of bp .com. Other: jbnanno@ att .net, stephentruax@ fossil biostratigraphy along the U.S. Gulf of Berggren et al. (1995a, 1995b). The Cenozoic comcast .net, edekaenel@ bluewin .ch, stacie .blair81@ gmail .com, JasonLundquist@ comcast .net, tboesiger@ Mexico Coast began with benthic foraminifera Texaco zonation utilized fossil bases and more nogcc .ne .gov, Maria .Bolivar@ bp .com, Kendra. Clark@ nearly a century ago (Loutit et al., 1988) and down-hole abundance increases in wells to en- bp .com. progressed from onshore to deep-water in re- hance resolution (271 k.y. for the Neogene). GSA Bulletin; November/December 2019; v. 131; no. 11/12; p. 1871–1888; https://doi.org/10.1130/B35062.1; 7 figures; 7 tables; Data Repository item 2018407; published online 16 April 2019. Geological Society of America Bulletin, v. 131, no. 11/12 1871 © 2018 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/131/11-12/1871/4861016/1871.pdf by guest on 27 September 2021 Bergen et al. The Texaco chart referred to the Berggren et al. unified internal framework, completed in 2007, Ceará Rise in the western tropical Atlantic (1985) time scale for the Neogene, but did not aided exploration and development efforts Ocean during ODP Leg 154 recovered an im- specify ages for biostratigraphic markers. Both within the stratigraphically and structurally portant composite cyclostratigraphic reference charts were founded on sequence stratigraphy, complex GoM deep-water (DW). section. The age model derived from ODP showing comparisons to the coastal onlap curve It had long been realized that there were only a Leg 154 cores is based on the astronomically- of Haq et al. (1988), and related to global plank- limited number of published geologic ages avail- tuned cycles (Shackleton and Crowhurst, 1997; tonic foraminifera (Blow, 1969) and nannofossil able for bioevents in GoM industrial schemes. Shackleton et al., 1999; Pälike and Shackleton (Martini, 1971) biozonations. Coupled with the late twentieth century “cyclo- 2000; Zachos et al., 2001) recalibrated to the Cenozoic stratigraphic research was in the stratigraphic revolution” and the availability of orbital solution of Laskar et al. (2004). This midst of a revolution during the 1990’s. Re- such reference sections, an internal research pro- composite section was sampled by de Kaenel search on, and formal ratification of, reference gram was initiated in 2002 with the goal to de- from the lower Oligocene (30.679 Ma) through outcrop sections known as global boundary rive astronomically-calibrated geologic ages for lower Pleistocene (1.595 Ma) for nannofossils stratotype section and point (GSSP) resulted the entire BP Neogene biostratigraphic frame- (1357 samples) and foraminifera (633 samples) in precise global definitions of stratotype work. Efforts culminated in the first “BP Gulf between 2003–2011. We realize continued boundaries (see stratigraphy .org). The scaling of of Mexico Neogene Astronomically-tuned Time improvements of the ODP Leg 154 astronom- geologic time shifted from geomagnetic polar- Scale” (BP GNATTS) in early 2007. Subsequent ical-tuning have been published for the up- ity time scales (GPTS) with the first applications research through 2012 extended calibration into per Miocene to Pliocene since 2011 (Zeeden of astronomical “tuning” (Lourens et al.,1996; the lower Oligocene through sampling and study et al., 2013; Drury et al., 2017; Wilkens et al., Laskar et al., 2004) of sedimentary cycles in the of the base Neogene GSSP in northern Italy and 2017) and that problems remain with the or- construction of higher temporal resolution Late ODP Leg 154 cores, offshore NE Brazil (Fig. 1). bital tuning of the Early Miocene (see Hilgen Neogene timescales (see Hilgen et al., 1997). In 2016, efforts were refocused on publication et al., 2012; Ogg et al., 2016), both of which Today, Neogene calcareous microfossil bio zona- of BP GoM taxonomy and biostratigraphy, in- could affect age estimates for the ODP Leg 154 tions (e.g., Backman et al., 2012) are founded cluding new research on ODP Leg 154 materials samples by as much as 100 k.y. We have main- almost entirely by astronomical ages. Although to more thoroughly document biostratigraphic tained the integrity of the astronomically-tuned the accuracy and precision of ages for Neogene events for