Abstract By comparing new detrital zircon provenance analysis of Triassic synrift sediments from the Tallahassee graben (FL), the South Georgia rift basin (GA), and Deep River rift basin (NC) with our previous detrital zircon provenance data for the Jurassic Norphlet Formation erg in the Eastern Gulf of Mexico, we have developed a regional model of Triassic-Jurassic erosion and sediment transport. In the Eastern Gulf of Mexico, detrital zircon ages observed in Triassic synrift clastics from the Tallahassee graben and southern South Georgia rift system contain not only Gondwanan-aged and Grenville-aged zircon grains but also an abundance of Paleozoic detrital zircon grains, reflecting sediment influx from rocks associated with the Paleozoic orogens of eastern Laurentia. Although Paleozoic detrital zircon grains are present in the younger Norphlet deposits, they are less abundant than in Triassic rift sediments. In southwest Alabama, the most abundant detrital zircon age population in the Norphlet Formation is Grenville-aged (950-1,250 Ma). In the Conecuh embayment of southeastern AL and western FL panhandle, Norphlet samples show a marked decrease in Grenville detrital zircon and an increase in 525-680 Ma zircon ages, interpreted to represent influx from rocks associated with the Gondwanan Suwannee terrane. In the Apala-chicola Basin, the proportion of Gondwanan zircon ages increases to nearly 40% of the total population and Grenville-aged grains constitute just ~20% of the population. We suggest that the difference between Triassic and Jurassic detrital zircon signatures in the Eastern Gulf of Mexico reflects significant unroofing of Paleozoic rocks during early Mesozoic rifting of the easternmost Eastern Gulf of Mexico, possibly including rocks equivalent with those exposed in the Talladega slate belt units. Subsequent erosion of rift-flanking highlands to expose older Gondwanan and Grenville rocks and/or input from northern sediment sources supplied the older Grenville-aged detrital zircon grains present in the Norphlet erg in the area to the west and within the Conecuh embayment.

Abstract Although the Upper Jurassic Haynesville Formation is a proven hydrocarbon reservoir in the onshore eastern Gulf of Mexico, the unit remains understudied because exploration has been focused on the older and more productive Norphlet and Smackover Formations. In this study, we use cores, gamma ray logs, and spontaneous potential logs from 49 wells in southern Alabama to analyze the Haynesville Formation. We point-counted 18 sandstone samples from seven cores, and six sandstone samples from four of those cores were analyzed for detrital zircon age distributions. Core and well log analyses indicate that the Haynesville Formation can be subdivided into anhydrite, sandstone, and carbonate lithofacies. The thickness and distribution of these lithofacies suggests that relict basement topography derived from the opening of the eastern Gulf of Mexico during Late Triassic-Early Jurassic time is the primary influence on Upper Jurassic sediment distribution. Framework grain compositions indicate that the sandstone lithofacies was derived from a recycled orogenic provenance, indicating a primarily Laurentian terrane source with some mixing from the Gondwanan Suwannee terrane. Detrital zircon age distributions from Haynesville Formation sandstones contain major age populations that correspond with derivation from both the Laurentian Grenville Province and Appalachian Mountain source rocks, with some mixing from the Gondwanan Suwanee terrane. Haynesville Formation detrital zircon ages and sandstone compositions are similar to that of the underlying Norphlet Formation, indicating that the provenance and sediment transport pathways remained similar through deposition of the Upper Jurassic units.

Subsurface sandstone samples of the Upper Jurassic (Oxfordian) Norphlet Formation erg deposits and (Kimmeridgian) Haynesville Formation sabkha deposits were collected from wells in the eastern Gulf of Mexico for U-Pb detrital zircon provenance analysis. Norphlet Formation samples in southwestern Alabama are characterized by detrital zircon ages forming two dominant populations: (1) 265–480 Ma, associated with Paleozoic Taconic, Acadian, and Alleghanian orogenic events of eastern Laurentia, and (2) 950–1250 Ma, associated with the Grenville orogenies of eastern Laurentia. These detrital zircon ages indicate derivation from Laurentian and Laurentian-affinity sources, including erosion of Paleozoic strata of the remnant Alleghanian fold-and-thrust belt and Black Warrior foreland basin, as well as Laurentian cratonic rocks exposed in remnant Appalachian orogenic highlands and eastern Gulf of Mexico rift-related horst blocks. In contrast, Norphlet Formation samples from the offshore Destin Dome exhibit a major population of 540–650 Ma zircon grains, along with a small population of 1900–2200 Ma zircon grains; these ages are interpreted to indicate contribution of sediment to the Norphlet erg from peri-Gondwanan terranes sutured to eastern Laurentian, as well as from the Gondwanan Suwannee terrane, which remained attached to North America after the rifting of Pangea. Samples from south-central Alabama yield subequal proportions of four major age populations: 250–500 Ma, 520–650 Ma, 900–1400 Ma, and 1950–2250 Ma. These ages indicate sediment was sourced by both Laurentian/Laurentian-affinity and Gondwanan/Gondwanan-affinity rocks, either through a combination of these rocks in the source area, or intrabasinal mixing of Laurentian/Laurentian-affinity sediment with Gondwanan/Gondwanan-affinity sediment. Detrital zircon provenance data from the overlying Haynesville Formation clastics of the Destin Dome offshore federal lease block also show the signature of Gondwanan/Gondwanan-affinity sediment input into the eastern Gulf of Mexico, suggesting that paleotopography affecting Norphlet Formation deposition persisted throughout much of the Late Jurassic. However, samples from the Pennsylvanian Pottsville Formation synorogenic fill of the Black Warrior Basin and Middle Cretaceous Rodessa Formation marginal marine sandstone lack evidence for any significant contribution of Gondwanan or Gondwanan-affinity detritus to the basin, indicating that transport of Gondwanan/Gondwanan-affinity zircon to the eastern Gulf of Mexico was due to early Mesozoic uplift, erosion, and/or paleodrainage pattern development. These results, along with previously reported detrital zircon provenance of Triassic and Jurassic sandstone of the southern United States, suggest that early Mesozoic sediment supply in southern North America was closely associated with erosion of Gondwanan/peri-Gondwanan crust docked along the Suwannee-Wiggins suture, which likely extended westward from the Suwannee terrane to the Yucatan-Campeche terrane; much of this Gondwanan/peri-Gondwanan crust remained docked along the Suwannee-Wiggins suture after the rifting of Pangea and prior to opening of the Gulf of Mexico.

The late Eocene to early Miocene Renova Formation records initial post-Laramide sediment accumulation in the intermontane basin province of southwest Montana. Recent studies that postulate deposition of the Renova Formation were restricted to a broad, low-relief, tectonically quiescent basin on the eastern shoulder of an active rift zone vastly differ from traditional models in which the Renova Formation was deposited in individual intermontane basins separated by basin-bounding uplands. This study utilizes detrital zircon geochronology to resolve the paleogeography of the Renova Formation. Detrital zircon was selected as a detrital tracer that can be used to differentiate between multiple potential sources of similar mineralogy but with distinctly different U-Pb ages. Laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) U-Pb detrital zircon ages were determined for 11 sandstones from the Eocene-Oligocene Renova Formation exposed in the Sage Creek, Beaverhead, Frying Pan, Upper Jefferson, Melrose, and Divide basins. Detrital zircon ages, lithofacies, paleoflow, and petrography indicate that provenance of the Renova Formation includes Paleogene volcanics (Dillon volcanics and Lowland Creek volcanics), Late Cretaceous igneous intrusions (Boulder batholith, Pioneer batholith, McCartney Mountain pluton), Mesozoic strata (Blackleaf Formation, Beaverhead Group), Belt Supergroup strata, and Archean basement. The oldest deposits of the Renova are assigned Bridgerian to Uintan North American Land Mammal (NALM) ages and contain detrital zircons derived from volcanic, sedimentary, and metamorphic rocks constituting the “cover strata” to uplift-cored Late Cretaceous plutonic bodies. Regional unroofing trends are manifested by a decreased percentage of cover strata–sourced zircon and an increased percentage of pluton-sourced zircon as Renova deposits became younger. Zircon derived from Late Cretaceous plutonic bodies indicate that initial unroofing of the McCartney Mountain pluton, Pioneer batholith, and Boulder batholith occurred during Duchesnean time. Facies assemblages, including alluvial fan, trunk fluvial, and paludal-lacustrine lithofacies, are integrated with detrital zircon populations to reveal a complex Paleogene paleotopography in the study area. The “Renova basin” was dissected by paleo-uplands that shed detritus into individual intervening basins. Areas of paleo-relief include ancestral expressions of the Pioneer Range, McCartney Mountain, Boulder batholith–Highland Range, and Tobacco Root Range. First-order alluvial distributary systems fed sediment to two noncontiguous regional-trunk fluvial systems during the Chadronian. A “Western fluvial system” drained the area west of the Boulder batholith, and an “Eastern fluvial system” drained the area east of the Boulder batholith. Chadronian paleodrainages parallel the regional Sevier-Laramide structural grain and may exhibit possible inheritance from Late Cretaceous fluvial systems. Detrital zircons of the Renova Formation can be confidently attributed to local sources exposed in highlands that bound the Divide, Melrose, Beaverhead, Frying Pan, Upper Jefferson, and Sage Creek basins. The data presented in this study do not require an Idaho batholith provenance for the Renova Formation.

Abstract The Triassic Songpan-Ganzi Complex (SGC) of central china is one of the world’s largest ancient turbidite systems, containing a thick succession of Anisian through Norian (∼240-210 Ma) turbidites. Geotectonically, the Songpan-Ganzi complex is situated at the juncture of several tectonic blocks: North china, Qiadam, South china, and North Tibet (i.e., Qiangtang; Figure 1 ). Songpan-Ganzi basin closure and inversion occurred during early Jurassic time and was later intruded and locally metamorphosed by Jurassic to Cretaceous plutons. Few studies document the nature of these turbidites due to the limited nature of outcrop exposures, steep topography, steep dip angles (70-90°) associated with isoclinal folds, and thick vegetation. A stratigraphic framework has recently been established for the Songpan-Ganzi terrane based on field mapping, lithology, and fossils. The fossils are sufficiently abundant to permit stage-level age assignments and correlation throughout much of the SGC basin (Figure 2). The succession of Middle to Upper Triassic turbidites within the Songpan-Ganzi complex is an estimated >10 km (>6 mi) thick, locally reaching a thickness of 15 km (9 mi), and cover a triangular area >200,000 km 2 (77,000 mi 2 ), an area about the size of the U.S. state of Colorado.