Late Cretaceous sediment provenance in the eastern Gulf Coastal Plain (U.S.A.) based on detrital-zircon U-Pb ages and Th/U values

Abstract

Detrital-zircon U-Pb geochronology documents a regional- to continental-scale drainage reorganization along the eastern Gulf Coastal Plain (USA) from the Late Cretaceous (Cenomanian) to the Paleocene–Eocene. We present detrital-zircon U-Pb ages and Th/U values from the Maastrichtian Ripley Formation to determine the sedimentary provenance and to provide spatiotemporal resolution of drainage reorganization. The Ripley Formation contains a 12.7% overall average abundance of detrital zircons with low (< 0.1) Th/U values relative to the underlying Cenomanian Tuscaloosa Group (3.6%), the overlying Paleocene–Eocene Wilcox Group (2.8%), an Appalachian foreland composite (2.1%), and the laterally equivalent McNairy Sandstone in the northern Mississippi Embayment (3.8%). Multidimensional scaling of detrital-zircon U-Pb spectra shows that the Ripley Formation is dissimilar from underlying and overlying Gulf Coastal Plain units, the McNairy Sandstone, and an Appalachian foreland composite sample because of differences in proportions of Appalachian (490–270 Ma) and Grenville (1250–900 Ma) zircons. We interpret the southern Appalachian Piedmont province as the principal sediment source region for the Ripley Formation to account for the elevated abundance of grains with low (< 0.1) Th/U values and unique detrital-zircon U-Pb age spectra. Results suggest a regional-scale (105 km2) drainage network, which delivered sediment to the Maastrichtian coast followed by northwestward littoral transport and eventual mixing with Appalachian foreland-derived sediment in the northern Mississippi Embayment. This study further brackets drainage reorganization along the eastern Gulf Coastal Plain and demonstrates how simple chemical–age relationships, such as zircon Th/U values coupled with U-Pb ages, can be used to evaluate sediment provenance.

Late Mesozoic sandstone volumes recorded in Gulf of Mexico subsurface depocentres: Deciphering long‐term sediment supply trends and contributions by paleo river systems

“…This and other lines of evidence are consistent with this model of dominant Late Mesozoic north‐directed sediment routing (Horner et al, 2019; Hubbard et al, 2011; Martin et al, 2019; Nardin et al, 2013). Jackson et al (2021) present provenance information from the Ripley Sandstone, suggesting that this pattern continued until the late‐Maastrichtian (about‐71 Ma). By the Paleocene, major expansion of western catchments and topographic elevation of Rocky Mountain source terranes during the Laramide orogeny shifted the bulk of sediment transport south to enter the Gulf Basin sediment repository (Blum et al, 2017; Blum & Pecha, 2014; Sharman et al, 2017).…”

“…Characteristic U‐Pb age spectra are available for the following fluvial axes: (1) Paleo‐Rio Grande River, (2) Paleo‐Red River (Blum & Pecha, 2014), (3) Paleo‐Mississippi River (Blum & Pecha, 2014; Kennedy, 2013), (4) Paleo‐Apalachicola River (Blum et al, 2017; Essex et al, 2016; Jackson et al, 2021; Weislogel et al, 2015) and (5) Peninsular River (Bovay, 2015; Snedden, Bovay, et al, 2016). Each of these paleo river samples indicate distinctive combinations of differing DZ U‐Pb age subsets linked to the source terrains from which the terrigenous sediments are derived.…”

“…A similar DZ U‐Pb age distribution is recognised in outcrop samples of the Santonian Eutaw Formation located in the Alabama Apalachicola drainage basin (Barrett, 2020). The Maastrichtian Ripley Formation of the eastern Gulf coastal plain shows increased Appalachian (490–270 ma) Piedmont contributions in much younger (Maastrichtian) strata, likely due to alongshore westerly paleo‐transport in a more wave‐dominated depositional system (Jackson et al, 2021). In general, the Paleo‐Apalachicola DZ U‐Pb age subset illustrated in Figure 4 is consistent with the composite Paleozoic Appalachian signature of DZ populations (Thomas et al, 2017).…”

“…The Pan‐African (Peri‐Gondwanan) DZ U‐Pb ages in each paleo river sample suggests tributaries in both catchments accessed the Suwannee terrane of northern Florida and southern Georgia. However, a drainage divide can logically be established during the HVB supersequence as the ratio of Laurentian (Grenville) to Gondwanan‐derived sediments decreases substantially to the east (Jackson et al, 2021). Our subsurface mapping indicates that the Paleo‐Apalachicola depocentre is one of the largest and longest in duration.…”

“…Using a much larger set of Cretaceous and Cenozoic outcrop samples, Blum and Pecha (2014) inferred northerly paleotransport into the Boreal Sea, likely from multiple contributing paleo rivers. Drainage reorganisation occurred sometime prior to the early Paleogene (Jackson et al, 2021) with the bulk of siliciclastics transported into the northern Gulf of Mexico to form large Wilcox submarine fans (Blum et al, 2017; Blum & Pecha, 2014; Sharman et al, 2017). The reconstructions of Blum and Pecha (2014) and Rahl et al (2003) both suggest diminished northern transport of sand‐size sediment at the same time.…”