Mark Feigenson

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Papers by Mark Feigenson

Wilson Lake site

Proceedings of the Ocean Drilling Program, Jul 24, 2017

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Mantle source heterogeneity in a Neoproterozoic back-arc basin: Geochemical and thermodynamic modeling of the volcanic section of Wadi Ghadir ophiolite, Egypt

Precambrian Research, 2022

Wadi Ghadir ophiolite in the Egyptian Eastern Desert, which forms the northern part of the Nubian... more Wadi Ghadir ophiolite in the Egyptian Eastern Desert, which forms the northern part of the Nubian Shield, is considered as one of the best-preserved segments of the Neoproterozoic oceanic lithosphere on Earth. Primary melt calculations and thermodynamic modeling of new geochemical data for the Wadi Ghadir pillow lavas and dike complexes, integrated with comprehensive petrographic investigations, are here employed to unravel the geodynamic evolution of this ophiolitic section. Whole-rock geochemical and clinopyroxene data indicate that the pillow lavas and sheeted dike complexes preserve geochemical signatures of N-MORB, E-MORB and OIB-like basalts. Less abundant, discrete dikes have a distinctly LILE-enriched island arc tholeiite (IAT) composition. The pillow lavas and sheeted dike complexes replicate mixed liquid lines of descent, whereas the discrete dikes exhibit a calc-alkaline differentiation trend. The pillow lavas were produced by limited (5-7%) mantle partial melting as a result of isothermal decompression over a wide pressure range (5 -19 kbar) and restricted mantle potential temperatures (Tp ≈ 1260-1300 • C), suggesting ponding of rising melts from depths of ~60 to 15 km in dry mantle. Primary melts of the sheeted dike complexes were produced by 9-11% partial melting at P ≈ 9.7 ± 2.5 kbar, Tp ≈ 1290 • C, and P ≈ 14.7 ± 1.4 kbar, Tp ≈ 1325 • C, suggesting a role of varying hydrostatic pressure. The magma source for the discrete dikes occurred at 10.7 ± 0.6 kbar and Tp of 1230-1300 • C by 11-13% partial melting of a metasomatized mantle region. The calculated Tp ranges for the different melts are consistently lower than temperatures of sub-ridge ambient mantle. Together with the variable concentrations of K 2 O and other incompatible elements, the estimated low temperatures of melt generation emphasize mixed sources and wet peridotite melting. The modeled primary melts designate crustal growth during back-arc basin opening and closure. During the basin opening, decompression melting of mildly enriched mantle produced high-Ti tholeiitic (pillow lavas) and transitional (sheeted dike complexes) melts, whereas subduction initiation during basin closure promoted melt-peridotite interaction. Lowering of the solidus by subduction-related components triggered melting of a spinel lherzolitic mantle and produced low-Ti calc-alkaline melts that sourced the discrete dikes. The mixed MORB and SSZ geochemical characteristics of the studied volcanic rocks, coupled with the various modeled melts and lack of significant thermal anomalies in the mantle conditions, are here interpreted as manifestations of mantle source heterogeneity in a marginal oceanic basin during the accretionary stages of the Arabian-Nubian Shield.

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Sr-isotopic evidence for leakage of pore water from clay-silt confining units to the Atlantic City 800-foot sand, Atlantic City, New Jersey

Proceedings of the Ocean Drilling Program, 150X Scientific Results, 1997

The evolution of water quality in confined aquifers in the New Jersey Coastal Plain may be affect... more The evolution of water quality in confined aquifers in the New Jersey Coastal Plain may be affected by leakage of pore water from the adjacent confining units. We investigated the distribution and sources of solutes, particularly Sr, in pore water mechanically extracted from clay-silt core samples collected from depths of 552-840 ft (168-256 m) in the lower Miocene Kirkwood Formation at Atlantic City, New Jersey (Ocean Drilling Program Leg 150X). The sampled sediments consist of thin clay-silt stringers in the upper part of the Atlantic City 800-ft sand, a major aquifer, and the massive clay-silt units above and below it. The distribution of Sr and the ratio of 87 Sr to 86 Sr in the pore water and adjacent shell material were used to identify the possible sources of, and physical processes that may affect the distribution of, Sr in the pore water. Concentrations of Sr in 14 pore-water samples from the clay-silt unit above the aquifer and the clay-silt interbeds in the upper part of the aquifer ranged from 2.74 to 28.19 µM/L; those in the four pore-water samples from the clay-silt unit below the aquifer ranged from 0.52 to 7.30 µM/L. Concentrations of Sr in the samples varied with depth but correlated strongly with pore-water concentrations of Ca, Mg, Na, and SO 4 . Cation-exchange processes may be responsible, in part, for the lower concentrations of Sr, Ca, and Mg in pore water from the clay-silt unit below the aquifer than in that above the aquifer. 87 Sr/ 86 Sr values in 11 samples of aragonitic mollusk shells (bearing no visible evidence of recrystallization) collected from depths in the clay-silt unit similar to those from which the pore-water samples were collected ranged from 0.708468 to 0.708713 , and decreased (Sr in the shells was less radiogenic) with depth. This trend is consistent with the decrease in the 87 Sr/ 86 Sr value in seawater through time during the early Miocene. The 87 Sr/ 86 Sr values in 12 pore-water samples from the studied stratigraphic interval ranged from 0.708257 to 0.708527 and also decreased with depth. The Sr-isotope ratios in the pore water were lower than those in the shell material from nearby or adjacent sediments for all samples but one. Because the only known source of Sr with an isotope ratio this low is shell material from sediments deeper than the strata from which the pore-water samples were collected (including pre-Miocene stratigraphic units), the isotope ratio in the pore-water samples from the lower Miocene claysilt units may result from upward movement of pore water into lower Miocene strata through geologic time, which could create the observed difference in Sr isotope ratios between the pore water and shells.

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Strontium-isotopic correlation of Oligocene to Miocene sequences, New Jersey and Florida

Proceedings of the Ocean Drilling Program, 150X Scientific Results, 1997

We use Sr-isotopic age estimates to date siliciclastic, carbonate, and mixed siliciclastic-carbon... more We use Sr-isotopic age estimates to date siliciclastic, carbonate, and mixed siliciclastic-carbonate Oligocene and Miocene sequences for the New Jersey Coastal Plain and Florida Peninsula and to correlate sequence boundaries with the deep-sea δ 18 O record and the inferred eustatic record of Exxon. The New Jersey onshore Oligocene to lower Miocene sequences correlate reasonably well with the Florida Miocene sequences. However, the majority of middle Miocene sequences mapped in New Jersey are missing from central Florida. The age of Oligocene to Miocene sequence boundaries determined in continuous boreholes from New Jersey, Alabama, and Florida show excellent correlation with deep-sea δ 18 O increases, which are inferred glacioeustatic lowerings. This is strong confirmation that global sea-level change is a primary control on the timing of Oligocene to Miocene sequence boundaries for the coastal plain sections studied here. Whereas global sea level has a significant influence on coastal plain sequences, there are major differences in the preservation of sequences within the same depositional basin (e.g., Salisbury Embayment) and between basins (e.g., Florida basins vs. Salisbury Embayment). These intra-and interbasinal differences must be ascribed to noneustatic processes such as tectonics or differential erosion. Tectonic mechanisms include faulting of crustal blocks, mobile basins with evolving arches and depocenters, local flexural subsidence, or differential subsidence caused by sediment loading.

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Oligocene to Middle Miocene Sr-Isotopic Stratigraphy of the New Jersey Continental Slope

Proceedings of the Ocean Drilling Program, 150 Scientific Results, 1996

We analyzed specimens of mixed planktonic foraminifer species for Sr isotopes from the Oligocene ... more We analyzed specimens of mixed planktonic foraminifer species for Sr isotopes from the Oligocene to middle Miocene sections from boreholes (Ocean Drilling Program Sites 902, 903, 904, and 906; and outcrops on the New Jersey continental slope. We concentrated on the upper Oligocene-middle Miocene at Sites 903 and 904 (444 and 1129 m present water depth, respectively), the upper Oligocene-lowermost Miocene at Site 902 (811m water depth), and slope outcrops in Carteret and Lindenkohl canyons. Sr-isotopic age estimates of the Ocean Drilling Program boreholes provide a good stratigraphic framework for upper Oligocene to middle Miocene sections, overcoming problems with rare calcareous plankton zonal markers. When integrated with ongoing biostratigraphic and magnetostratigraphic studies, the Leg 150 sites will provide a precise chronology of slope reflectors that also correlate with sequences boundaries traced under the continental shelf. Preliminary integration is encouraging: (1) nine of the 10 Oligocene to middle Miocene slope reflectors (sequence boundaries) correlate with global δ 18 θ increases and with sequence boundaries in the onshore New Jersey coastal plain, arguing for a causal link between formation of sequence boundaries and glacioeustatic lowerings; and (2) several hiatuses on the slope also correlate with reflectors and the major δ 18 θ increases, although many of the seismic reflectors appear to be conformable at the slope boreholes. Outcrop studies date a major change in depositional regime in the earliest Oligocene; this "siliciclastic switch" from an Eocene carbonate ramp to a starved siliciclastic early Oligocene margin correlates with a global δ 18 θ increase and a regional cooling. Sediment starvation in the early Oligocene resulted in a poorly preserved record on the slope. Sedimentation rates subsequently increased in the middle Oligocene on the entire margin, when prograding clinoforms appeared beneath the modern shelf and rates increased again in the early to middle Miocene. We attribute this progradational change to lower long-term sea level, although hinterland tectonics may have played an important role.

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Cape May Zoo Site

Proceedings of the Ocean Drilling Program|174AX (Suppl.) Initial Reports, 2007

Geochemistry and magmatic evolution of explosive tephras et3 and et4 from Arenal Volcano, Costa Rica

Revista Geológica de América Central, 2011

An outcrop at El Cruce, 5.7 km from the vent of Arenal volcano, exposes thick sequences of two re... more An outcrop at El Cruce, 5.7 km from the vent of Arenal volcano, exposes thick sequences of two recent tephras, ET4 (silicic) and, immediately above, ET3 (mafic). The ET4 to ET3 transition is abrupt, with no soil between the layers. Therefore, they appear to be part of one eruptive phase. A petrological model is inferred from the detailed stratigraphic record of these eruptions. The ET4 sequence can be modeled by crystal fractionation via gravity settling. ET4 is most mafic at the top of the section. The silicic tephra at the bottom of this unit is aphyric. Compatible elements increase and incompatible elements decrease moving down through the magma chamber. The percentage of phenocrysts increases through the top. Models of crystal fractionation, using the most mafic and phenocryst enriched tephra as the parent magma, produce the most silicic tephra by removal of 37% phenocrysts. The ET3 sequence shows the opposite trend of that seen in the ET4 sequence, becoming less enriched in incompatible elements down through the section. Some crystal sorting, followed by the removal of a silicic melt from the top of the magma chamber, could generate the reversed trend for the ET3 sequence.

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Integrated sequence stratigraphy of the postimpact sediments from the Eyreville core holes, Chesapeake Bay impact structure inner basin

The ICDP-USGS Deep Drilling Project in the Chesapeake Bay impact structure: Results from the Eyreville Core Holes, 2009

The Eyreville core holes provide the fi rst continuously cored record of postimpact sequences fro... more The Eyreville core holes provide the fi rst continuously cored record of postimpact sequences from within the deepest part of the central Chesapeake Bay impact crater. We analyzed the upper Eocene to Pliocene postimpact sediments from the Eyreville A and C core holes for lithology (semiquantitative measurements of grain size and composition), sequence stratigraphy, and chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, and planktonic foraminifers); age resolution is approximately ±0.5 Ma for early Miocene sequences and approximately ±1.0 Ma for younger and older sequences. Eocene-lower Miocene sequences are subtle, upper middle

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Petrology and geochemistry of lavas

Central America, 2007

This continuity disappears, however, if one considers individual parts of the [Central American] ... more This continuity disappears, however, if one considers individual parts of the [Central American] chain and examines separate groups of volcanoes within a restricted volcanic field. It then becomes apparent that the continuity of the province as a whole is the result of grouping excessively large segments of the chain." A.R. McBirney: Compositional variations in Cenozoic calcalkaline suites of Central America. Intern. Upper Mantle Sci. Rept. 16, 1969.

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RU_CAGeochem, a database and sample repository for Central American volcanic rocks at Rutgers University

Geoscience Data Journal, 2014

The Rutgers University Central American geochemical dataset focuses on the active volcanoes relat... more The Rutgers University Central American geochemical dataset focuses on the active volcanoes related to the Cocos‐Caribbean convergent plate boundary that extends from Guatemala to Costa Rica in Central America. The RU prefix signifies that the data and samples are primarily from the long‐term Central American research project started at Dartmouth College in 1970 and continued at Rutgers University from 1974 to the present. The database is decidedly uneven because of the impressive improvement of analytical techniques over the span of data collection. Further complications arose because most of the sampling and analysis were part of the educational process for many different undergraduate and graduate students using different types of instruments. This note presents, as a reasonably coherent whole, geochemical data and metadata for about 1400 samples collected by at least 40 students and colleagues. Many unpublished Sr, Nd, and Pb isotopic ratios are included here but most of the new...

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Postimpact deposition in the Chesapeake Bay impact structure: Variations in eustasy, compaction, sediment supply, and passive-aggressive tectonism

The ICDP-USGS Deep Drilling Project in the Chesapeake Bay impact structure: Results from the Eyreville Core Holes, 2009

The Eyreville and Exmore, Virginia, core holes were drilled in the inner basin and annular trough... more The Eyreville and Exmore, Virginia, core holes were drilled in the inner basin and annular trough, respectively, of the Chesapeake Bay impact structure, and they allow us to evaluate sequence deposition in an impact crater. We provide new high-resolution geochronologic (<1 Ma) and sequence-stratigraphic interpretations of the Exmore core, identify 12 defi nite (and four possible) postimpact depositional sequences, and present comparisons with similar results from Eyreville and other mid-Atlantic core holes. The concurrence of increases in δ 18 O with Chesapeake Bay impact structure sequence boundaries indicates a primary glacioeustatic control on deposition. However, regional comparisons show the differential preservation of sequences across the mid-Atlantic margin. We explain this distribution by the compaction of impactites, regional sediment-supply changes, and the differential movement of basement structures. Upper Eocene strata are thin or missing updip and around the crater, but they thicken into the inner basin (and offshore to the southeast) due

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Lead isotopes reveal bilateral asymmetry and vertical continuity in the Hawaiian mantle plume

Nature, 2005

The two parallel chains of Hawaiian volcanoes ('Loa' and 'Kea') are known to have statistically d... more The two parallel chains of Hawaiian volcanoes ('Loa' and 'Kea') are known to have statistically different but overlapping radiogenic isotope characteristics. This has been explained by a model of a concentrically zoned mantle plume, where the Kea chain preferentially samples a more peripheral portion of the plume. Using high-precision lead isotope data for both centrally and peripherally located volcanoes, we show here that the two trends have very little compositional overlap and instead reveal bilateral, non-concentric plume zones, probably derived from the plume source in the mantle. On a smaller scale, along the Kea chain, there are isotopic differences between the youngest lavas from the Mauna Kea and Kilauea volcanoes, but the 550-thousand-year-old Mauna Kea lavas are isotopically identical to Kilauea lavas, consistent with Mauna Kea's position relative to the plume, which was then similar to that of present-day Kilauea. We therefore conclude that narrow (less than 50 kilometres wide) compositional streaks, as well as the larger-scale bilateral zonation, are vertically continuous over tens to hundreds of kilometres within the plume. Correspondence and requests for materials should be addressed to W.A.

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Plume–subduction interaction in southern Central America: Mantle upwelling and slab melting

Lithos, 2011

The volcanic front in southern Central America is well known for its Galapagos OIB-like geochemic... more The volcanic front in southern Central America is well known for its Galapagos OIB-like geochemical signature. A comprehensive set of geochemical, isotopic and geochronological data collected on volumetrically minor alkaline basalts and adakites were used to better constrain the mantle and subduction magma components and to test the different models that explain this OIB signature in an arc setting. We report a migration of back-arc alkaline volcanism towards the northwest, consistent with arc-parallel mantle flow models, and a migration towards the southeast in the adakites possibly tracking the eastward movement of the triple junction where the Panama Fracture Zone intersects the Middle America Trench. The adakites major and trace element compositions are consistent with magmas produced by melting a mantle-wedge source metasomatized by slab derived melts. The alkaline magmas are restricted to areas that have no seismic evidence of a subducting slab. The geochemical signature of the alkaline magmas is mostly controlled by upwelling asthenosphere with minor contributions from subduction components. Mantle potential temperatures calculated from the alkaline basalt primary magmas increased from close to ambient mantle (~1380-1410 °C) in the Pliocene to ~1450 °C in the younger units. The calculated initial melting pressures for these primary magmas are in the garnet stability field (3.0-2.7 GPa). The average final melting pressures range between 2.7 and 2.5 GPa, which is interpreted as the lithosphere-asthenosphere boundary at ~85-90 km. We provide a geotectonic model that integrates the diverse observations presented here. The slab detached after the collision of the Galapagos tracks with the arc (~10-8 Ma). The detachment allowed hotter asthenosphere to flow into the mantle wedge. This influx of hotter asthenosphere explains the increase in mantle potential temperatures, the northwest migration in the back-arc alkaline lavas that tracks the passage of the hotter asthenosphere, and the presence of a slab melting signature in the volcanic front caused by recycling of Galapagos Hotspot tracks.

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Flux versus decompression melting at stratovolcanoes in southeastern Guatemala

Journal of Volcanology and Geothermal Research, 2003

The major and trace element geochemistry of lavas erupted from four volcanic front (VF) stratovol... more The major and trace element geochemistry of lavas erupted from four volcanic front (VF) stratovolcanoes in southeastern Guatemala show differences in the relative importance of flux and decompression melting in a continental arc setting. The VF stratovolcanoes exhibit a wide compositional range from basalt to dacite, although modern Pacaya erupts basaltic lavas. The VF basalts have relatively low MgO contents and plot outside the field of primary arc magmas defined by melting experiments on hydrous peridotite. After subtracting the effects of the fractionation, assimilation, and alteration of some VF lavas, separate partial melting and mixing trends were identified for Agua^Pacaya and Tecuamburro^Moyuta. The distinct chemical signatures of the hemipelagic and carbonate sediments subducted off Guatemala provide constraints on material transfer processes that occurred between the slab and mantle wedge. Model fluids and melts from the subducted slab were calculated using recently published mineral^aqueous fluid partition coefficients. Wide separation of the model fluid and melt compositions on a U/La versus Ba/Th diagram creates diagnostic mixing curves with an enriched mid-ocean ridge basalt source. Fluid from mature ocean crust has high U/La, fluid from carbonate sediment has high Ba/Th, and fluid and melt from hemipelagic sediments have both high U/La and Ba/Th. In a simple single-stage model, a mantle metasomatized by fluid originating largely from the oceanic crust with only minor sediment fluid contributions best explains the overall large ion lithophile element composition of the VF lavas. (Th/Rb) N ratios of V1 in the VF lavas from southeastern Guatemala require a component of sediment melting. Therefore, a more realistic two-stage model to describe the Guatemalan arc data involves an initial hemipelagic sediment melt input to the wedge followed by minor fluid additions from the oceanic crust or sediments. Correlation between measures of slab input and extent of melting in the older VF lavas from Tecuamburro and Moyuta favors flux-dominated melting near the base of the mantle wedge. In sharp contrast, the lack of a relationship between slab additions and melting in younger lavas from Agua and Pacaya volcanoes implies a significant role for decompression

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Rheology of melts and magmatic suspensions: 1. Design and calibration of concentric cylinder viscometer with application to rhyolitic magma

Journal of Geophysical Research: Solid Earth, 1988

Accurate rheological data for silicate melts and crystal‐melt, melt‐vapor, and crystal‐melt‐vapor... more Accurate rheological data for silicate melts and crystal‐melt, melt‐vapor, and crystal‐melt‐vapor suspensions of both natural compositions and simple binary and ternary systems are useful in constraining theories of momentum transport in magmatic systems and theories of melt structure. Data addressing these problems are presented in a series of papers of which this is the first. A high‐torque wide‐gap concentric cylinder viscometer has been constructed and used for characterization of the rheometric properties of rhyolitic magma under conditions of varying temperature (1100°–1350°C) and shear rate (0.05–13 s−1) at 105 Pa total pressure. Two natural rhyolitic starting materials were used in these experiments. Four independent temperature‐shear rate cycles were performed on composition RlA (∼76% SiO2) and two independent cycles on composition R2A (∼74% SiO2). Each run had a small (3–8 vol %) fraction of vapor present during viscometric testing. A power law model of the form τ = m (T) ...

U‐series disequilibria in Guatemalan lavas, crustal contamination, and implications for magma genesis along the Central American subduction zone

Journal of Geophysical Research: Solid Earth, 2007

New U‐series results indicate that Guatemalan volcanic rocks display both 238U and 230Th excesses... more New U‐series results indicate that Guatemalan volcanic rocks display both 238U and 230Th excesses. 230Th excess is restricted to volcanoes in central Guatemala, both along and behind the front. 230Th excess correlates with a number of incompatible element ratios, such as Th/Nb and Ba/Th. It also shows a negative correlation with MgO. Guatemalan volcanic rocks have (230Th/232Th) ratios that overlap those of Costa Rican volcanics and are therefore considerably lower than the unusually high ratios characterizing volcanic rocks from Nicaragua. Along‐arc variations in (230Th/232Th) therefore mirror those of a number of diagnostic geochemical parameters, such as Ba/La, which are symmetrical about a peak in west central Nicaragua. The one siliceous lava analyzed, from the Cerro Quemado dome complex, has a recognizable crustal imprint, distinguished, for instance, by high Th/Nb and low Ba/Th. In mafic samples, 238U excess is attributed to addition of a U‐enriched fluid component from the su...

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

Geosphere, 2013

Integrated Ocean Drilling Program Expedition 313 continuously cored and logged latest Eocene to e... more 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 signifi cance of sequence boundaries. We provide a chronology for these sequences using integrated strontium isotopic stratigraphy and biostratigraphy (primarily calcareous nannoplankton, diatoms, and dinocysts [dinofl agellate cysts]). Despite challenges posed by shallowwater 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.

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Dynamical model for temporal variation in magma type and eruption interval at Kohala volcano, Hawaii

Geology, 1981

Dynamical model for temporal variation '\"==D-F@ig@"S°"* in magma type and er... more Dynamical model for temporal variation '\"==D-F@ig@"S°"* in magma type and eruption interval De°@"""fGe°'PQ'@a' 10 —-o at Kohala volcano, Hawa and Geophysical Sciences Princeton University Frank J. Spera Princeton, New Jersey 08544 ABSTRACT At Kohala ...

Uppermost Campanian–Maestrichtian strontium isotopic, biostratigraphic, and sequence stratigraphic framework of the New Jersey Coastal Plain

Geological Society of America Bulletin, 1995

Firm stratigraphic correlations are needed to evaluate the global significance of unconformity bo... more Firm stratigraphic correlations are needed to evaluate the global significance of unconformity bounded units (sequences). We correlate the well-developed uppermost Campanian and Maestrichtian sequences of the New Jersey Coastal Plain to the geomagnetic polarity time scale (GPTS) by integrating Sr-isotopic stratigraphy and biostratigraphy. To do this, we developed a Maestrichtian (ca. 73-65 Ma) Sr-isotopic reference section at Deep Sea Drilling Project Hole 525A in the southeastern Atlantic Ocean. Maestrichtian strata can then be dated by measuring their 87 Sr/ 86 Sr composition, calibrating to the GPTS of S. C. Cande and D. V. Kent (1993, personal commun.), and using the equation Age (Ma) ‫؍‬ 37 326.894 ؊ 52 639.89 ( 87 Sr/ 86 Sr). Sr-stratigraphic resolution for the Maestrichtian is estimated as ؎1.2 to ؎2 m.y. At least two unconformity-bounded units comprise the uppermost Campanian to Maestrichtian strata in New Jersey. The lower one, the Marshalltown sequence, is assigned to calcareous nannofossil Zones CC20/21 (ϳNC19) and CC22b (ϳNC20). It ranges in age from ϳ74.1 to 69.9 Ma based on Sr-isotope age estimates. The overlying Navesink sequence is assigned to calcareous nannoplankton Zones CC25-26 (ϳNC21-23); it ranges in age from 69.3 to 65 Ma based on Sr-isotope age estimates. The upper part of this sequence, the Tinton Formation, has no calcareous planktonic control; Sr-isotopes provide an age estimate of 66 ؎ 1.2 Ma (latest Maestrichtian). Sequence boundaries at the base and the top of the Marshalltown sequence match boundaries elsewhere in the Atlantic Coastal Plain (Owens and Gohn, 1985) and the inferred global sea-level record of Haq et al. (1987); they support eustatic changes as the mechanism controlling depositional history of this sequence. However, the latest Maestrichtian record in New Jersey does not agree with Haq et al. (1987); we attribute this to correlation and time-scale differences near the Cretaceous/Paleogene boundary. High sedimentation rates in the latest Maestrichtian of New Jersey (Shrewsbury Member of the Red Bank Formation and the Tinton Formation) suggest tectonic uplift and/or rapid progradation during deposition of the highstand systems tract.

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Upper Cretaceous sequences and sea-level history, New Jersey Coastal Plain

Geological Society of America Bulletin, 2004

We developed a Late Cretaceous sealevel estimate from Upper Cretaceous sequences at Bass River an... more We developed a Late Cretaceous sealevel estimate from Upper Cretaceous sequences at Bass River and Ancora, New Jersey (ODP [Ocean Drilling Program] Leg 174AX). We dated 11-14 sequences by integrating Sr isotope and biostratigraphy (age resolution ؎0.5 m.y.) and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses. Sequences generally shallow upsection from middle-neritic to inner-neritic paleodepths, as shown by the transition from thin basal glauconite shelf sands (transgressive systems tracts [TST]), to medial-prodelta silty clays (highstand systems tracts [HST]), and finally to upperdelta-front quartz sands (HST). Sea-level estimates obtained by backstripping (accounting for paleodepth variations, sediment loading, compaction, and basin subsidence) indicate that large (Ͼ25 m) and rapid (K1 m.y.) sea-level variations occurred during the Late Cretaceous greenhouse world. The fact that the timing of Upper Cretaceous sequence boundaries in New Jersey is similar to the sea-level lowering records of Exxon Production Research Company (EPR), northwest Euro-

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Mark Feigenson

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