Integrated Ocean Drilling Program Expedition 313 continuously cored uppermostEocene to Miocene sequences on the New Jersey shallow shelf (Sites M27, M28, and M29). Previously, 15 Miocene (ca. 23-13 Ma) seismic sequence boundaries were recognized on several generations of multichannel seismic profi les using criteria of onlap, downlap, erosional truncation, and toplap. We independently recognize sequence boundaries in the cores and logs based on an integrated study of core surfaces, lithostratigraphy and process sedimentology (grain size, mineralogy, facies, and paleoenvironments), facies successions, stacking patterns, benthic foraminiferal water depths, downhole logs, core gamma logs, and chronostratigraphic ages. We use a velocitydepth function to predict the depths of seismic sequence boundaries that were tested by comparison with major core surfaces, downhole and core logs, and synthetic seismograms. Using sonic velocity (core and downhole), core density, and synthetic seismograms, we show that sequence boundaries correspond with acoustic impedance contrasts, although other stratal surfaces (e.g., maximum fl ooding and transgressive surfaces) also produce refl ections. Core data are suffi cient to link seismic sequence boundaries to impedance contrasts in 9 of 12 instances at Site M27, 6 of 11 instances at Site M28, and 8 of 14 instances at Site M29. Oligocene sequences have minimal lithologic and seismic expression due to deep-water locations on clinoform bottomsets. Miocene sequences (ca. 23-13 Ma) were sampled across several unconformity clino-thems (prograding units) on topset, foreset, and bottomset locations. Excellent recovery allows core-seismic integration that confi rms the hypothesis that unconformities are a primary source of impedance contrasts. Our core-seismic-log correlations predict that key seismic surfaces observed in other sub surface investigations without core and/or well logs are stratal surfaces with sequence stratigraphic signifi cance.
The newly mapped Kapiti‐Manawatu Fault System (KMFS) in southern North Island, New Zealand, accommodated ∼3.5 km of basement throw over the last 3 Myr. Along‐strike throw profiles are generated using seven stratigraphic markers, interpreted from seismic reflection profiles acquired <3 km apart. The profiles are symmetrical about their point of maximum displacement, and cumulative profiles suggest that the reverse fault system behaves coherently. The KMFS originates from the reactivation of extensional structures, with fault lengths remaining constant over time. Contractional deformation started at circa 1750 ± 400 ka. Maximum dip‐slip rates along individual faults are 1.77 ± 0.53 and 0.74 ± 0.22 mm yr−1 for the 0–120 and 120–1350 ka periods, respectively. The maximum cumulative throw rates across the KMFS are 4.9 ± 1.5 and 1.5 ± 0.5 mm yr−1 for the same periods. Long‐term strain rates across the KMFS are 2–5 times smaller than strain rates in the forearc basin of the Hikurangi subduction margin located less than 100 km to the east. The faults of the KMFS may extend to depth and link with the subducted Pacific plate.
The Cretaceous and Palaeogene sediments of the basins in Central Asia include the remnants of the easternmost extent of a vast shallow epicontinental sea, which extended across the Eurasian continent before it retreated westwards and eventually isolated as the Paratethys Sea. To improve understanding of its long-term palaeogeographical evolution, we complement the well-constrained chronological framework of the Tarim Basin in China with stratigraphic records of the sea retreat from the Fergana Basin and the Alai Valley Basin in southern Kyrgyzstan and the Afghan–Tajik Basin in SW Tajikistan. By lithostratigraphic analyses and identification of bivalve assemblages, this study establishes for the first time a clear and detailed regional correlation of Palaeogene marine strata across Central Asia, showing that the basins share a similar palaeogeographical evolution characterized by a long-term stepwise retreat punctuated by short-term shallow-marine incursions. Our correlation shows that the last two marine incursions recognized in the Tarim Basin can be traced westwards. The permanent disappearance of the sea from Central Asia probably occurred with limited diachroneity in the late Eocene, before the isolation of the Paratethys Sea, shifting the easternmost margin of the sea hundreds of kilometres westwards and probably significantly reducing moisture supply to the Asian interior.
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