Physical Sciences and Mathematics Commons^™

Visualizing Object Oriented Software In Three Dimensions, Colin Ware, David Hui, Glenn Franck

Center for Coastal and Ocean Mapping

There is increasing evidence that it is possible to perceive and understand increasingly comple x information systems if they are displayed a s graphical objects in a three dimensional space . Object-oriented software provides an interestin g test case - there is a natural mapping fro m software objects to visual objects . In this paper we explore two areas. 1) Information perception : we are running controlled experiments to determine empirically if our initial premise is valid; how much more (or less) can be understoo d in 3D than in 2D? 2) Layout: our strategy is to combine partially …

Characteristics Of Ion Flow In The Quiet Inner Plasma Sheet, V. Angelopoulos, C. F. Kennel, F. V. Coroniti, R. Pellat, Harlan E. Spence, Margaret G. Kivelson, Raymond J. Walker, W. Baumjohann, W. C. Feldman, J. T. Gosling, C. T. Russell

Physics & Astronomy

Abstract

We use AMPTE/IRM and ISEE 2 data to study the properties of the high beta (β_i > 0.5) plasma sheet, the inner plasma sheet (IPS). Bursty bulk flows (BBFs) are excised from the two databases, and the average flow pattern in the non-BBF (quiet) IPS is constructed. At local midnight this ensemble-average flow is predominantly duskward; closer to the flanks it is mostly earthward. The flow pattern agrees qualitatively with calculations based on the Tsyganenko [1987] model (T87), where the earthward flow is due to the ensemble-average cross tail electric field and the duskward flow is the diamagnetic drift …

Instrument Description And Performance Of The Imaging Gamma-Ray Telescope Comptel Aboard The Compton Gamma-Ray Observatory, V. Schonfelder, H. Aarts, K Bennett, H Deboer, J. Clear, W Collmar, A Connors, A. Deerenberg, R Diehl, A. Von Dordrecht, J W. Den Herder, W Hermsen, R M. Kippen, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, G. Simpson, M. Snelling, G Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, C De Vries, C Winkler

Space Science Center

The COMPTEL instrument aboard the COMPTEL Gamma-Ray Observatory and its performance capabilities are described. Calibration data are used to determine the angular and energy response, and the effective detection area. The imaging properties of COMPTEL are demonstrated, and the sensitivity of Comptel to celestial gamma-ray sources are estimated from flight data.

Acoustic Properties Of Fine‐Grained Sediments From Emerald Basin: Toward An Inversion For Physical Properties Using The Biot–Stoll Model, Robert C. Courtney, Larry A. Mayer

Affiliate Scholarship

Acoustic data from two long cores, comprising marine clays and silts taken from Emerald Basin off Nova Scotia, are presented. High‐resolution measurements of compressional wavevelocity,attenuation, and power law exponent are made using ultrasonic frequencies between 100 to 1000 kHz. The observed values of the frequency dependence of attenuation suggest that a nonconstant Q mechanism is needed to explain these data, and Biot–Stoll theory is used to model the experimental results. An inversion scheme is used to constrain physical parameters in the Biot–Stoll dispersion relation. The inversion shows that there is a restricted range of permeability and grain size. By assigning …

Calculation Of Acoustic Parameters By A Filter-Correlation Method, Robert C. Courtney, Larry A. Mayer

Affiliate Scholarship

This paper presents the filter correlation method, a technique for extracting consistent and accurate estimates of attenuation parameters from acoustic waveform data. The method minimizes problems associated with short time windows and multipath secondary arrivals. The method comprises two stages: a causal passband filter stage followed by a cross-correlation step. The results of the filter-correlation estimator are compared to those of the spectral difference approach for short time series with and without a secondary multipath arrival. Preliminary analyses of acoustic data collected on cored marine silts and clays show the attenuation properties of these materials cannot be described by a …

Comptel Gamma Ray And Neutron Measurements Of Solar Flares, James M. Ryan, D J. Forrest, J Lockwood, M Loomis, Mark L. Mcconnell, D Morris, W Webber, G Rank, V Schonfelder, B Swanenburg, K Bennett, L O. Hanlon, C Winkler, H Debrunner

Space Science Center

COMPTEL on the Compton Gamma Ray Observatory has measured the flux of x‐rays and neutrons from several solar flares. These data have also been used to image the Sun in both forms of radiation. Unusually intense flares occurred during June 1991 yielding data sets that offer some new insight into of how energetic protons and electrons are accelerated and behave in the solar environment. We summarize here some of the essential features in the solar flare data as obtained by COMPTEL during June 1991.

Search For Gamma‐Ray Emission From Agn With Comptel, W Collmar, R Diehl, G G. Lichti, V Schonfelder, H Steinle, A W. Strong, H Bloemen, J W. Den Herder, W Hermsen, B Swanenburg, C De Vries, Mark L. Mcconnell, James M. Ryan, G Stacy, K Bennett, O R. Williams, C Winkler

Space Science Center

The COMPTEL data (∼0.7–30 MeV) were searched for emission from AGN. Four sources have been detected so far: the quasars 3C 273, 3C 279, PKS 0528+134, and the radio galaxy Centaurus A. 3C 273 and 3C 279 were detected in CGRO observation period 3 with quite different spectral shapes. There is also evidence for 3C 273 at a weak flux level in observation period 11. The quasar PKS 0528+134 was detected above 3 MeV as part of a search for AGN already observed by EGRET. Cen A was seen up to 3 MeV by combining data from different observation periods.

Comptel Observations Of Cygnus X‐1, Mark L. Mcconnell, A Connors, D J. Forrest, James M. Ryan, W Collmar, R Diehl, V Schonfelder, H Steinle, A W. Strong, H Bloemen, R Van Dijk, W Hermsen, L Kuiper, B Swanenburg, C Winkler

Space Science Center

We report on the latest results from an analysis of data on Cygnus X‐1 as collected by the COMPTEL experiment on the Compton Gamma‐Ray Observatory (CGRO). COMPTEL detected the source around 1 MeV during two separate one‐week observations in 1991. The measured flux levels indicate variability on a time scale of weeks. The results also indicate flux levels which are well below the levels reported by some investigators for an excess of emission in the energy range ≥1 MeV.

An Overview Of First Results From Comptel, V. Schonfelder, H Aarts, K Bennett, H Bloemen, H Deboer, M Busetta, W Collmar, A Connors, R Diehl, J W. Den Herder, W Hermsen, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, C Winkler

Space Science Center

COMPTEL is the first imaging telescope to explore the MeV gamma-ray range (0.7 to 30 MeV). At present, it is performing a complete sky survey. Targets of special interest in the COMPTEL energy range are radio pulsars, X-ray binaries, novae, supernovae, supernova remnants, mulecular clouds, the interstellar medium within the Milky Way, active galactic nuclei, and the diffuse cosmic background radiation. The data from the first half year of the mission have demonstrated that COMPTEL performs as expected. The Crab is clearly seen at its proper position in the first images of the anticenter region of the galaxy. The Crab …

Laboratory And Well-Log Velocity And Density Measurements From The Ontong Java Plateau: New In-Situ Corrections To Laboratory Data For Pelagic Carbonates, Jozsef Urmos, Roy H. Wilkens, Frank Bassinot, Mitchell Lyle, Janice C. Masters, Larry A. Mayer, David Mosher

Affiliate Scholarship

During Ocean Drilling Program Leg 130, sonic velocity and bulk density/porosity well logs were measured in five separate holes drilled through the sequence of pelagic carbonate oozes, chalks, and limestones that comprise the thick, continuous sedimentary cover on the Ontong Java Plateau. An internally consistent and continuous suite of shipboard laboratory velocity and sediment physical properties measurements were made from the top of each hole down through the entire logged interval. Because of the high quality of the data, extensive overlap of 500 m or more between the log and laboratory measurements at each hole, and the homogeneous nature of …

Evolution Of Pliocene Climate Cyclicity At Hole 806b (5-2 Ma); Oxygen Isotope Record, Eystein Jansen, Larry A. Mayer, Jan Backman, R. Mark Leckie, Toshiaki Takayama

Affiliate Scholarship

A detailed Pliocene oxygen isotope record from the Ontong Java Plateau, based on measurements of the surface-dwelling planktonic foraminifer Globigerinoides sacculifer, was produced for the period from 5 to 2 Ma. The record documents major long and short-term climate changes. The results show periods of enhanced ice volume at 4.6 to 4.3 Ma and after 2.85 Ma, a long-term warming trend from 4.1 to 3.7 Ma, and a distinct cooling trend that was initiated at 3.5 Ma and progressed through the initiation of large-scale Northern Hemisphere glaciation after 2.85 Ma (according to the time scale of Shackleton and others proposed …

Seismic Stratigraphy Of The Ontong Java Plateau, David Mosher, Larry A. Mayer, Tom H. Shipley, Edward L. Winterer, Rick A. Hagen, Janice C. Marsters, Frank Bassinot, Roy H. Wilkens, Mitchell Lyle

Affiliate Scholarship

The Ontong Java Plateau, a large, deep-water carbonate plateau in the western equatorial Pacific, is an ideal location for studying responses of carbonate sedimentation to the effects of changing paleoceanographic conditions. These carbonate responses are often reflected in the physical properties of the sediment, which in turn control the appearance of seismic reflection profiles. Seismic stratigraphy analyses, correlating eight reflector horizons to each drill site, have been conducted in an attempt to map stratigraphic data. Accurate correlation of seismic stratigraphic data to drilling results requires conversion of traveltime to depth in meters. Synthetic seismogram models, using shipboard physical properties data, …

Velocity Anisotropy In Calcareous Sediments From Leg 130, Ontong Java Plateau, Frank Bassinot, Janice C. Marsters, Larry A. Mayer, Roy H. Wilkens

Affiliate Scholarship

During Leg 130, an intensive program of P-wave velocity measurements was conducted on calcareous sediments of varying induration (ranging from ooze to limestone) that cover the Ontong Java Plateau (west equatorial Pacific). The high quantity and quality of shipboard acoustical property measurements seemed to be particularly appropriate for gaining a better understanding of acoustic anisotropy in calcareous sediments. Major results can be summarized as follows: 1. In calcareous oozes, acoustic anisotropy exists even at shallow depths of burial. Values are low, ranging from -0.5% to 3.5% and averaging 1.2%. Anisotropy profiles are affected by coring disturbances, but they still roughly …

Preliminary Results From Comptel On A Search For Gamma-Ray Line Emission From Sn 1991t, G G. Lichti, K Bennett, H Bloemen, H Deboer, M Busetta, W Collmar, A Connors, R Diehl, R Van Dijk, J W. Den Herder, W Hermsen, L Kuiper, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, M Varendorff, C De Vries, C Winkler

Physics & Astronomy

The COMPTEL experiment aboard the Compton Gamma-Ray Observatory is designed to image celestial gamma-radiation in the energy range from 0.7-30 MeV. With a field of view of 1 sr it is capable of locating strong point sources with an accuracy of better than 0.5 deg. From June 15 to 28, 1991 and a second time from October 3 to 17, 1991 the region containing the supernova SN 1991T was observed by COMPTEL. Here preliminary results from these observations are presented, with special attention to a search for gamma-ray line emission from the supernova.

Contributions Of The Low-Latitude Boundary Layer To The Finite Width Magnetotail Convection Model, Harlan E. Spence, M. G. Kivelson

Physics & Astronomy

Convection of plasma within the terrestrial nightside plasma sheet contributes to the structure and, possibly, the dynamical evolution of the magnetotail. In order to characterize the steady state convection process, we have extended the finite tail width model of magnetotail plasma sheet convection. The model assumes uniform plasma sources and accounts for both the duskward gradient/curvature drift and the earthward E × B drift of ions in a two-dimensional magnetic geometry. During periods of slow convection (i.e., when the cross-tail electric potential energy is small relative to the source plasma's thermal energy), there is a significant net duskward displacement of …

Comptel Observations Of The 1.809 Mev Gamma-Ray Line From Galactic 26al, R Diehl, C. Dupraz, K Bennett, H Bloemen, H Deboer, W Hermsen, G G. Lichti, Mark L. Mcconnell, D Morris, James M. Ryan, V. Schonfelder, H Steinle, A W. Strong, B Swanenburg, M Varendorff, C Winkler

Physics & Astronomy

No abstract provided.

Comptel Detections Of The Quasars 3c 273 And 3c 279, W Hermsen, H Aarts, K Bennett, H Bloemen, H Deboer, W Collmar, A Connors, R Diehl, R Vandijk, J W. Den Herder, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, James M. Ryan, V. Schonfelder, G. Simpson, H Steinle, A W. Strong, B Swanenburg, C De Vries, W Webber, O R. Williams, C Winkler

Physics & Astronomy

The COMPTEL experiment aboard the Compton Gamma Ray Observatory, sensitive in the energy range from about 0.7 to 30 MeV, observed the high-latitude region containing 3C 273 and 3C 279 during a 2-week period in June, 1991. A search for sources using a maximum likelihood analysis revealed two statistically significant point-like excesses, the positions of which are consistent with those of 3C 273 and 3C 279. These sources are the first QSOs detected at MeV energies. In the COMPTEL energy domain their spectra appear to be greatly different. A comparison with earlier and simultaneous measurements in neighboring energy ranges indicates …

First Results From Comptel Measurement Of The Al-26 1.8 Mev Gamma-Ray Line From The Galactic Center Region, R Diehl, K Bennett, H Bloemen, H Deboer, M Busetta, W Collmar, A Connors, J W. Den Herder, C. Devries, W Hermsen, J Knodlseder, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, M Varendorff, P. Von Ballmoos, W Webber, C Winkler

Physics & Astronomy

The COMPTEL instrument on GRO is designed to image celestial gamma radiation in the approximately 0.7-30 MeV region of nuclear lines. Within a large field of view of about 1 sr its angular resolution of about 1 deg enables mapping of extended emission and location of (strong) point sources to an accuracy of better than 0.5 deg. The Galactic center region was observed by COMPTEL for a 2-week period in July 1991. Here we report the detection of the line at 1.8 MeV attributed to Al-26, addressing in particular the extent of the emission and the 1.8 MeV line flux.

The Crab And Galactic Anticentre Region Observed By Comptel, A W. Strong, K Bennett, H Bloemen, H Deboer, R Buccheri, M Busetta, W Collmar, A Connors, R Diehl, J W. Den Herder, W Hermsen, L Kuiper, J Lockwood, G G. Lichti, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, B Swanenburg, M Varendorff, C Winkler, C De Vries

Physics & Astronomy

The Galactic anticenter region including the Crab nebula has been observed with the COMPTEL gamma-ray telescope on the Gamma Ray Observatory. A map of the region in the 1-30 MeV energy range is presented. The total spectrum of the Crab is derived as well as that of the pulsed and unpulsed components. Upper limits on the pulsar Geminga are also presented.

Comptel Observations Of The Crab And Vela Pulsars, K Bennett, H Aarts, H Bloemen, R Buccheri, M Busetta, W Collmar, A Connors, A Carramiñana, R Diehl, H Deboer, J W. Den Herder, W Hermsen, L Kuiper, J Lockwood, G G. Lichti, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, C Winkler

Physics & Astronomy

The COMPTEL gamma-ray telescope, sensitive in the range 0.7-30 MeV, has viewed the Crab and Vela Pulsars. The light curves observed from both objects have been derived in several energy bands. Features of these light curves and some spectral details are discussed.

Gamma‐Ray Burst Studies By Comptel During Its First Year Of Operation, C Winkler, K Bennett, L O. Hanlon, O R. Williams, W Collmar, R Diehl, V Schonfelder, H Steinle, M Varendorff, J W. Den Herder, W Hermsen, L Kuiper, B Swanenburg, C De Vries, A Connors, D J. Forrest, R M. Kippen, Mark L. Mcconnell, James M. Ryan

Space Science Center

During the first year of Compton GRO operations, more than 20 cosmic gamma‐ray burst‐detected by the BATSE instrument ‐ occurred inside the 1 sr field of view of the imaging gamma‐ray telescope COMPTEL. Using COMPTEL’s primary mode of operation (the telescope mode) direct images (with ∼1° GRB location accuracy) and event spectra (0.7 MeV – 30 MeV) with spectral resolution better than 10% FWHM have been obtained. In its secondary mode of burst operations, COMPTEL has recorded time resolved spectra (0.1 MeV – 10 MeV) from its large NaI detectors. This paper summarises the results on cosmic GRB sources obtained …

The Design Of A Gamma‐Ray Burst Polarimeter, Mark L. Mcconnell, D J. Forrest, K Levenson, W T. Vestrand

Space Science Center

The study of the polarization properties of the gamma‐ray bursts is the one remaining unexplored avenue of research which may help to answer some of the fundamental problems regarding the nature of these mysterious objects. We have designed an instrument to measure linear polarization in cosmic gamma‐ray bursts at energies ≳50 keV. Here we describe the design of this instrument, which we call the Gamma‐ray Burst Polarimeter Experiment (GRAPE).

Comptel Observations Of The Inner Galaxy, H Bloemen, H Deboer, R Van Dijk, J W. Den Herder, W Hermsen, L Kuiper, B Swanenburg, C De Vries, W Collmar, R Diehl, G G. Lichti, V Schonfelder, H Steinle, A W. Strong, Mark L. Mcconnell, A Connors, D Morris, G Stacy, K Bennett

Space Science Center

This paper presents a first global study of COMPTEL observations of the inner Galaxy in the energy range 0.75–10 MeV. Preliminary findings demonstrate COMPTEL’s capabilities for mapping the observed gamma radiation and disentangling the contributions from point sources and diffuse emission.

Initial Results From Comptel—An Overview, V Schonfelder, W Collmar, R Diehl, G G. Lichti, H Steinle, A W. Strong, M Varendorff, H Bloemen, H Deboer, R Vandijk, J W. Den Herder, W Hermsen, L Kuiper, B Swanenburg, C De Vries, A Connors, D J. Forrest, Mark L. Mcconnell, D Morris, James M. Ryan, G Stacy, K Bennett, C Winkler, B G. Taylor

Space Science Center

COMPTEL is presently completing the first full sky survey in MeV gamma‐ray astronomy (0.7 to 30 MeV). An overview of initial results from the survey is given: among these are the observations of the Crab and Vela pulsars with unprecedented accuracy, the observation of the black hole candidates Cyg X‐1 and Nova Persei 1992, an analysis of the diffuse Galactic continuum emission from the Galactic center region, the broad scale distribution of the 1.8 MeV line from radioactive ^{2 6}Al, upper limits on gamma‐ray line emission from SN 1991T, observations of the three quasars 3C273, 3C279 and PKS 0528+134 …

Comptel Observations Of Gamma-Ray Bursts - Imaging And Localization, A Connors, H Aarts, K Bennett, H Bloemen, H Deboer, M Busetta, W Collmar, R Diehl, R Van Dijk, L O. Hanlon, J W. Den Herder, W Hermsen, R M. Kippen, L Kuiper, A. Klumper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, G. Simpson, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, O R. Williams, C Winkler

Space Science Center

The COMPTEL experiment on GRO images 0.7-30 MeV celestial gamma-radiation that falls within its 1 steradian field of view. During the first eleven months of orbit, preliminary lozalizations from BATSE triggers indicated that about 1 in 6 cosmic events could have fallen within COMPTEL's field of view. WE present COMPTEL positions for four of the brighter of these gamma-ray bursts.

Comptel Observations Of Gamma-Ray Bursts - Time Profiles And Spectra, W Collmar, K Bennett, H Bloemen, H Deboer, M Busetta, A Connors, R Diehl, J Greiner, L O. Hanlon, J W. Den Herder, W Hermsen, L Kuiper, G G. Lichti, J Lockwood, John R. Macri, Mark L. Mcconnell, D Morris, R Much, James M. Ryan, V. Schonfelder, J G. Stacy, H Steinle, A W. Strong, B Swanenburg, B G. Taylor, M Varendorff, C De Vries, W Webber, O R. Williams, C Winkler

Space Science Center

The COMPTEL experiment aboard CGRO is designed to image celestial gamma-radiation in the energy range from 0.7-30 MeV, and also to accumulate time-resolved NaI detector spectra (0.1-10 MeV) upon receipt of a BATSE burst trigger signal. During the early phases of the GRO mission several bursts have been observed. In this paper we present time profiles and first results from spectral analysis for GRB 910425, GRB 910601, and GRB 910814.

Climatic Cyclicity At Site 806; The Grape Record, Larry A. Mayer, Eystein Jansen, Jan Backman, Toshiaki Takayama

Affiliate Scholarship

We used the continuous saturated bulk density records collected by the gamma-ray attenuation porosity evaluator (GRAPE) at Ocean Drilling Program Site 806 on the top of the Ontong Java Plateau to evaluate the continuity of the recovered cores and to splice together a complete section from the multiple holes drilled at the site (for the upper 165 m, this is equivalent to approximately 0-5 Ma). The lack of offset in core breaks (between the 9.5-m-long, successive cores) from hole to hole made splicing difficult, and the results are not unambiguous. The composite section was converted to a time series by …

Variations Of Porosity In Calcareous Sediments From The Ontong Java Plateau, Frank Bassinot, Janice C. Marsters, Larry A. Mayer, Roy H. Wilkens

Affiliate Scholarship

Based on index properties measurements made on board the JOIDES Resolution, we studied porosity changes with depth in the fairly homogeneous deep-sea calcareous sediments cored during Ocean Drilling Program Leg 130 on the Ontong Java Plateau. Using Leg 130 data, we present evidence that the rate of porosity decrease with burial in calcareous oozes and chalks is related to the depth of deposition and thus probably depends on the "conditioning" of calcareous sediments by winnowing or dissolution processes during the time of deposition. The ooze-to-chalk transition is not clearly reflected in porosity profiles. In the ooze-chalk sections studied (the upper …

Basement Structure Of The Northern Ontong Java Plateau, Rick A. Hagen, Larry A. Mayer, David Mosher, Loren W. Kroenke, Tom H. Shipley, Edward L. Winterer

Affiliate Scholarship

Site surveys conducted in conjunction with Leg 130 on the Ontong Java Plateau reveal a strong seismic reflector at 0.8 to 1.0 s below the seafloor that drilling at Sites 803 and 807 confirmed is Cretaceous basalt. This reflector is generally smooth, except for the northeastern margin of the plateau, where it forms a series of small, irregularly shaped depressions. Correlatable reflectors present at the bottom of the depressions are also present on the adjacent highs, suggesting that these depressions are original volcanic topography. A strong sub-basalt reflector occurs on many seismic profiles on the northeastern portion of the plateau. …

Detailed Stratigraphic Correlation Of The Neogene Sedimentary Sequences On The Ontong Java Plateau By Well Logging; Odp Sites 803, 805, 806, 807, And Dsdp Site 586, Mitchell Lyle, Roy H. Wilkens, Larry A. Mayer

Affiliate Scholarship

We used well logs, in some cases combined with shipboard physical properties measurements to make more complete profiles and to correlate between sites on the Ontong Java Plateau. By comparing sediment bulk density, velocity, and resistivity logs from adjacent holes at the same site, we showed that even subtle features of the well logs are reproducible and are caused by variations in sedimentation. With only minor amounts of biostratigraphic information, we could readily correlate these sedimentary features across the entire top of the Ontong Java Plateau, demonstrating that for most of the Neogene the top of the plateau is a …