Paleogene stratigraphy and sea-level history of the North Carolina Coastal Plain: Global coastal onlap and tectonics

Coastal onlap of Paleogene depositional sequences, mapped by stage, and compared to curves of global coastal onlap and eustasy facilitate differentiation of the effects of local uplift and subsidence from eustasy on the Onslow and Albemarle Blocks about the Neuse Hinge in North Carolina. Differential uplift and subsidence of these blocks has controlled the stratal geometries and patterns of relative coastal onlap on each block. Potential mechanisms to produce the uplift and subsidence include episodic flexural deformation resulting from sediment loading in the Salisbury Embayment, and horizontal compressional deformation resulting from plate motion. Danian sea-level rise produced the initial Paleogene siliciclastic sequences (TA1.2 and TA1.3) on both blocks. After deposition of the Danian sequences and prior to Thanetian inundation, the Onslow Block was elevated relative to the Albemarle Block. The Ypresian (TA2.5-2.9, one) is generally restricted to the downdip Albemarle Block, has a depositional updip limit, and represents a major basinward shift in local coastal onlap at a time when global coastal onlap and long-term eustatic curves predict a major landward shift. This suggests that both blocks were uplifted during the Ypresian. Lutetian-Bartonian sequences (TA3.3-TA3.5/3.6) represent the most extensive landward shift in coastal onlap during the Paleogene in North Carolina and show erosional updip limits on both blocks. Differences in the degree of overstepping on the two blocks reflects post-middle Eocene uplift, but greater relative uplift of the Albemarle Block. The Priabonian (TA4.1 and either the TA4.2 or TA4.3) has erosional updip limits on both blocks and represents a significant basinward shift in local coastal onlap. This shift occurs during a time when global coastal onlap and long-term eustasy indicate a landward shift as great as that during the Lutetian-Bartonian. Therefore, both blocks were uplifted, but the distribution of the Priabonian on the Albemarle Block indicates greater relative uplift. In North Carolina, the Rupelian (TA4.4) oversteps the Priabonian on both blocks but not as far as predicted by global coastal onlap and eustasy. Based on the offlapping relationship of the erosional updip limit on both blocks, both areas were uplifted prior to Rupelian deposition. Chattian sediments (TB1.1-1.4, lower part) reflect a downward shift in coastal onlap which is consistent with global coastal onlap and long-term eustatic fall.