Jersey Shallow Shelf Research Articles

New Jersey's paleoflora and eastern North American climate through Paleogene–Neogene warm phases

Pollen of middle Oligocene to early Miocene age from core sediments from the New Jersey Shallow Shelf (Atlantic Coastal Plain: IODP-Expedition 313, Site M0027A), was analyzed using light- and scanning electron microscopy, and a pollen-based bioclimatic analysis was performed. The microflora is dominated by Quercus pollen. Pollen ornamentations indicate that Quercus pollen most likely originated from species of sections Quercus, Lobatae, Quercus/Lobatae and aff. section Protobalanus. Eotrigonobalanus, an extinct Fagaceae lineage, was present in the coastal plain. Relative abundances of several tree taxa (e.g., Carya) did not change significantly between the Oligocene warm phases, but contrast to late middle Miocene (comprising most of the Langhian and Serravallian) records from the same area.By assigning terrestrial palynomorphs to paleovegetation units, topographic movements of these units were identified. The mesophytic forest was the most widespread and zonal vegetation type in the hinterland through the analyzed interval. Periodic changes in the relative abundances of paleovegetation units suggest altitudinal vegetation movements responding to global climate change. Observed movement signals are generally weak, but increases in bisaccate pollen, representing spread of high- and mid-latitude forest, probably reflect the onset of cold intervals such as cooling phases at ~29.1, ~28.5, and 23.5 Ma. Spread of edaphically controlled forest formations during regression phases also indicates climate change. The onset of the Mi-1 event at ~23.03 Ma is probably reflected by a decrease in pollen-inferred paleotemperatures, although the event itself occurred during a sedimentation hiatus. Pollen-based paleoclimate reconstructions indicate long-term stability in temperature and precipitation within the humid warm temperate zone.

Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027)

Abstract. We investigated the palynology of sediment cores from Site M0027 of IODP (Integrated Ocean Drilling Program) Expedition 313 on the New Jersey shallow shelf to examine vegetation and climate dynamics on the east coast of North America between 33 and 13 million years ago and to assess the impact of over-regional climate events on the region. Palynological results are complemented with pollen-based quantitative climate reconstructions. Our results indicate that the hinterland vegetation of the New Jersey shelf was characterized by oak–hickory forests in the lowlands and conifer-dominated vegetation in the highlands from the early Oligocene to the middle Miocene. The Oligocene witnessed several expansions of conifer forest, probably related to cooling events. The pollen-based climate data imply an increase in annual temperatures from ∼11.5 °C to more than 16 °C during the Oligocene. The Mi-1 cooling event at the onset of the Miocene is reflected by an expansion of conifers and mean annual temperature decrease of ∼4 °C, from ∼16 °C to ∼12 °C around 23 million years before present. Relatively low annual temperatures are also recorded for several samples during an interval around ∼20 million years before present, which may reflect the Mi-1a and the Mi-1aa cooling events. Generally, the Miocene ecosystem and climate conditions were very similar to those of the Oligocene. Miocene grasslands, as known from other areas in the USA during that time period, are not evident for the hinterland of the New Jersey shelf, possibly reflecting moisture from the proto-Gulf Stream. The palaeovegetation data reveal stable conditions during the mid-Miocene climatic optimum at ∼15 million years before present, with only a minor increase in deciduous–evergreen mixed forest taxa and a decrease in swamp forest taxa. Pollen-based annual temperature reconstructions show average annual temperatures of ∼14 °C during the mid-Miocene climatic optimum, ∼2 °C higher than today, but ∼1.5 °C lower than preceding and following phases of the Miocene. We conclude that vegetation and regional climate in the hinterland of the New Jersey shelf did not react as sensitively to Oligocene and Miocene climate changes as other regions in North America or Europe due to the moderating effects of the North Atlantic. An additional explanation for the relatively low regional temperatures reconstructed for the mid-Miocene climatic optimum could be an uplift of the Appalachian Mountains during the Miocene, which would also have influenced the catchment area of our pollen record.

Sea-level control of New Jersey margin architecture: Palynological evidence from Integrated Ocean Drilling Program Expedition 313

Integrated Ocean Drilling Program Expedition 313 recovered Miocene sequences at Holes M0027A and M0029A on the New Jersey shallow shelf that contain a characteristic acid-resistant organic component. The palynofacies within each sequence reflects variations in terrigenous versus authigenic flux through the Miocene that are associated with sea-level change. Very high ratios of terrigenous versus marine palynomorphs and of oxidation-resistant versus susceptible dinocysts are associated with seismic sequence boundaries, consistent with their interpretation as sequence-bounding unconformities generated at times of low sea level. Comparison of palynological distance from shoreline estimates with paleodepth estimates derived from foraminiferal data allows relative sea level to be reconstructed at both sites. Ages assigned using dinocyst biostratigraphy are consistent with other chronostratigraphic indicators allowing sequence boundaries to be correlated with Miocene oxygen isotope (Mi) events. Paleoclimatic evidence from the pollen record supports the global climate changes seen in the oxygen isotope data. Although chronological control is relatively crude, Milankovitch-scale periodicity is suggested for parasequences visible in thick sequences deposited in relatively deep water where substantial accommodation existed, such as during the early Langhian at Site 29 (Middle Miocene Climatic Optimum). Palynological analysis thus supports the long-held hypothesis that glacioeustasy is a dominant process controlling the architecture of continental margins.

Chronology of Eocene-Miocene sequences on the New Jersey shallow shelf: Implications for regional, interregional, and global correlations

Integrated Ocean Drilling Program Expedition 313 continuously cored and logged latest Eocene to early-middle Miocene sequences at three sites (M27, M28, and M29) on the inner-middle continental shelf offshore New Jersey, providing an opportunity to evaluate the ages, global correlations, and significance of sequence boundaries. We provide a chronology for these sequences using integrated strontium isotopic stratigraphy and biostratigraphy (primarily calcareous nannoplankton, diatoms, and dinocysts [dinoflagellate cysts]). Despite challenges posed by shallow-water sediments, age resolution is typically ±0.5 m.y. and in many sequences is as good as ±0.25 m.y. Three Oligocene sequences were sampled at Site M27 on sequence bottomsets. Fifteen early to early-middle Miocene sequences were dated at Sites M27, M28, and M29 across clinothems in topsets, foresets (where the sequences are thickest), and bottomsets. A few sequences have coarse (∼1 m.y.) or little age constraint due to barren zones; we constrain the age estimates of these less well dated sequences by applying the principle of superposition, i.e., sediments above sequence boundaries in any site are younger than the sediments below the sequence boundaries at other sites. Our age control provides constraints on the timing of deposition in the clinothem; sequences on the topsets are generally the youngest in the clinothem, whereas the bottomsets generally are the oldest. The greatest amount of time is represented on foresets, although we have no evidence for a correlative conformity. Our chronology provides a baseline for regional and interregional correlations and sea-level reconstructions: (1) we correlate a major increase in sedimentation rate precisely with the timing of the middle Miocene climate changes associated with the development of a permanent East Antarctic Ice Sheet; and (2) the timing of sequence boundaries matches the deep-sea oxygen isotopic record, implicating glacioeustasy as a major driver for forming sequence boundaries.

Microbial community analysis of deeply buried marine sediments of the New Jersey shallow shelf (IODP Expedition 313)

The investigated deeply buried marine sediments of the shallow shelf off New Jersey, USA, are characterized by low organic carbon content and total cell counts of < 10(7) cells per mL sediment. The qPCR data for Bacteria and Archaea were in the same orders of magnitude as the total cell counts. Archaea and Bacteria occurred in similar 16S rRNA gene copy numbers in the upper part of the sediments, but Bacteria dominated in the lowermost part of the analyzed sediment cores down to a maximum analyzed depth of c. 50 meters below seafloor (mbsf). The bacterial candidate division JS1 and the classes Anaerolineae and Caldinilineae of the Chloroflexi were almost as highly abundant as the total Bacteria. Similarly high dsrA gene copy numbers were found for sulfate reducers. The abundance of the Fe(III) and Mn(IV) reducers comprising Geobacteraceae in the upper c. 15 mbsf correlated with concentrations of manganese and iron in the pore water. The isolated 16S rRNA gene sequences of Archaea in clone libraries could be allocated to the phyla Thaumarchaeota, Euryarchaeota, and Crenarchaeota with 1%, 14%, and 85%, respectively. The typical deep subsurface sediment-associated groups MBG-B, MBG-D, MCG, and SAGMEG were represented in the sediment community. MCG was the dominant group with a high diversity of the isolated 16S rRNA gene sequences.

Magnetostratigraphic importance of secondary chemical remanent magnetizations carried by greigite (Fe3S4) in Miocene sediments, New Jersey shelf (IODP Expedition 313)

Paleomagnetic and mineral magnetic analyses were carried out on Miocene clays from upper unit II at Sites M0027 and M0028 recovered during Integrated Ocean Drilling Program Expedition 313 on the New Jersey shallow shelf. A zone of mixed polarity in the lower section of Hole M0028A and dual overlapping magnetization components in upper Hole M0027A indicate that the sediments may have been chemically remagnetized during one or several events. Mineral magnetic investigations reveal that the magnetization is carried by the ferrimagnetic iron-sulfide greigite (Fe3S4), possibly with traces of titano-magnetite. We find that several changes in polarity coincide with variations in magnetic mineral grain size and/or concentration. We interpret these variations as different stages of greigite growth, which were triggered by changes in pore-water chemistry and/or upward migration of methane.

Stable isotope geochemistry of pore waters and marine sediments from the New Jersey shelf: Methane formation and fluid origin

Interstitial water and sediment samples of Integrated Ocean Drilling Program (IODP) Expedition 313 (New Jersey Shallow Shelf) were analyzed for chemical composition and stable isotope ratios. The analyses indicate a previously unknown complex geometry of the underlying fresh-water lens with alternating fresh-water–salt-water intervals divided by sharp boundaries in the upper part of the cores. Three fluid sources were identified: (1) meteoric fresh water, (2) marine seawater, and (3) brine. The pore-fluid stable isotope values define a mixing line with end members that have δ18O and δ2H values of –7.0‰ and –41‰ for fresh water, and –0.8‰ and –6‰ for salt water, respectively. This is similar to the modern mean value of New Jersey precipitation and today’s New Jersey shelf water. For fresh water, this either indicates modern meteoric recharge via aquifers that crop out on mainland New Jersey or emplacement at a time with climatic and hydrologic conditions similar to modern. An origin from Pleistocene glacial meltwaters with depleted isotope values is not confirmed by stable isotope data of this study. Salt water also represents modern isotope values suggesting an infiltration along permeable, coarse-grained sandy units. The lower core parts are characterized by mixing with brine fluids that originate from evaporites in the deep underground. Stable carbon isotope analyses of gas and fluids prove the existence of methane formation from degradation of marine organic matter and CO2 reduction in the lower core parts below ∼350 m below seafloor. Methane concentrations above 10000 ppm and δ13Cmethane values of ∼–80‰ were measured. Methane formation is also indicated by authigenic carbonates with low δ13Ccarbonate values. Although not reaching the surface at present conditions, the venting out of variable fluxes of methane from passive continental margins due to sea-level fluctuations is significant for the long-term carbon cycle. Authigenic carbonates indicate the precipitation from pore fluids with marine oxygen stable isotope ratios at low temperatures. The geochemical data and interpretations presented in this study supply the missing link between existing onshore and offshore data and may provide the basis for an integrated approach to construct a geochemical transect across the New Jersey shallow shelf.

Sequence boundaries are impedance contrasts: Core-seismic-log integration of Oligocene–Miocene sequences, New Jersey shallow shelf

Integrated Ocean Drilling Program Expedition 313 continuously cored uppermost Eocene 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 profiles 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 velocity-depth 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 flooding and transgressive surfaces) also produce reflections. Core data are sufficient 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 clinothems (prograding units) on topset, foreset, and bottomset locations. Excellent recovery allows core-seismic integration that confirms the hypothesis that unconformities are a primary source of impedance contrasts. Our core-seismic-log correlations predict that key seismic surfaces observed in other subsurface investigations without core and/or well logs are stratal surfaces with sequence stratigraphic significance.

Testing sequence stratigraphic models by drilling Miocene foresets on the New Jersey shallow shelf

We present seismic, core, log, and chronologic data on three early to middle Miocene sequences (m5.8, m5.4, and m5.2; ca. 20–14.6 Ma) sampled across a transect of seismic clinothems (prograding sigmoidal sequences) in topset, foreset, and bottomset locations beneath the New Jersey shallow continental shelf (Integrated Ocean Drilling Program Expedition 313, Sites M27–M29). We recognize stratal surfaces and systems tracts by integrating seismic stratigraphy, lithofacies successions, gamma logs, and foraminiferal paleodepth trends. Our interpretations of systems tracts, particularly in the foresets where the sequences are thickest, allow us to test sequence stratigraphic models. Landward of the clinoform rollover, topsets consist of nearshore deposits above merged transgressive surfaces (TS) and sequence boundaries overlain by deepening- and fining-upward transgressive systems tracts (TST) and coarsening- and shallowing-upward highstand systems tracts (HST). Drilling through the foresets yields thin (

Seismic Prediction While Drilling (SPWD): Looking Ahead of the Drill Bit by Application of Phased Array Technology

No abstract available. doi:10.2204/iodp.sd.9.08.2010