The UNIVERSITY of WISCONSIN

Home , Eights Coast, George VI Sound, Jones Mountains

Geophysical & Polar Research Center

DEPARTMENT OF GEOLOGY

ANTARCTIC PENINSULA TRAVERSE GEOPHYSICAL RESULTS RELATING TO GLACIOLOGICAL AND GEOLOGICAL STUDIES by John C. Behrendt

RESEARCH REPORT NO. 64-1-MARCH, 1964

Research Report Series Number 64-1 March 1964

ANTARCTIC PENINSULA TRAVERSE GEOPHYSICAL RESULTS

RELATING TO GLACIOLOGICAL AND GEOLOGICAL STUDIES

John C. Behrendt

The University of Wisconsin Geophysical and Polar Research Center 6021 South Highland Road Madison, Wisconsin 53705 SUMMARY

This report presents the results of geophysical measurements relating to glaciology and geology made during the Antarctic Peninsula Traverse of 1961-1962. Maps of snow surface and bedrock elevation, free-air and Bouguer anomalies, and total magnetic intensity anomalies are presented. The Antarctic Peninsula is an island separated from the Sentinel Range by a channel 1000 m below sea level and from the Eights Coast of Ellsworth Land by a channel 500 m deep.

Seismic velocity variations in the upper 50 m of the firn,of approximately constant mean annual temperature, show correlations with the widely ranging annual accumulation values; these relationships are used to obtain estimates of accumulation where only seismic data are available. A reflection horizon 450 m above the base of the ice near Eights Station was observed. Wide-angle reflections showed the existence of a low- velocity layer below this reflecting horizon which is interpreted as a result of moraine within the ice.

Numerous high amplitude magnetic anomalies with sources close to the base of the ice characterize the southern Antarctic Peninsula. The Jones Mountains area also has many magnetic anomalies whose origin near the base of the ice is consistent with the shallow "magnetic basement" measured in Marie Byrd Land to the southwest. The few magnetic anomalies in a central area of Ellsworth Land suggest a deeper basement and possibly a thick metasedimentary section associated with that of the Ellsworth Mountains. Several lines of evidence indicate that in spite of some structural similarities, the Antarctandean geology of the southern Ant- arctic Peninsula is noc continuous with the Ellsworth Mountains. Diurnal variations observed in the magnetic field have a standard deviation from diurnal variations measured at Eights Station of ± 15y. Standard deviations for individual days show a correlation with magnetic anomalies observed in the field.

An 18 km refraction profile showed a velocity of 3.87 km/sec in the top 0.9 km of ice, a velocity of 4.4 km/sec in the next 0.2 km, a velocity of 5.3 km/sec in the next 3L- km, and a possible velocity of 6.0 km/sec in the rock below.

The rough subglacial topography precludes the use of gravity data to provide quantitative information on density variations in the underlying geology in most places. At one location on the Antarctic Peninsula where good subglacial topographic control exists from seismic soundings, theoretical free-air anomaly profiles constructed by the line integral method show that more accurate bedrock elevations can be obtained from closely spaced gravity data than has previously been possible using infinite slab assumptions with the usual 6 km spacing. The method requires station spacing closer than the topographic "wave length" and seismic reflection soundings close enough to determine the regional gravity gradient. The mean free-air anomaly in Ellsworth Land is +11 mgals indicating that the area is approximately in isostatic equilibrium. Although high free-air anomalies were observed on several crossings, the southern Antarctic Penin- sula is shown to be regionally compensated. Bouguer anomalies suggest several kilometers of crustal thickening beneath the Antarctic Peninsula when compared with Ellsworth Land.

The data tabulated or presented in graphical form include: position, elevation of snow and rock surfaces, observed gravity, free-air anomaly, and total magnetic intensity at 6 km intervals; Bouguer anomalies at all seismic soundings or rock outcrops; detailed surface elevation and total magnetic intensity values at 0.75 km intervals; reflection travel times for each seismic sounding of ice thickness; geology observations at 11 nunataks; P-wave velocity in the firn vs. depth and distance data, and density vs. depth curves in the firn at all reflection stations; graphs of diurnal variation of magnetic total intensity for 20 days compared with Eights Station diurnal curves; and reproductions of portions of reflection seismograms at all reflection stations.

I I I I I I

I I I PREFACE

This report contains the geophysical results of the 1961-1962 Antarctic Peninsula Traverse. Discussions of many of the data included in the tabulations have previously been published by Behrendt (1963 and 1964). CONTENTS

Page

Introduction ......

Observation and Analysis of Data 5

Results...... 13

Discussion of Glaciological Results 19

Snow Densification ...... 23

Basal Low Velocity Layer . . . 31

Discussion of Geological Results 37

Summary of Surface Geology . 38

Magnetic Anomalies...... 41

Long Refraction Profile . . . 55

Gravity Anomalies ...... 59

Acknowledgements ...... 65

References ...... 67

Appendix I: Tabulated Data . 71

Table A: General Data Summary 72

Table B: Detailed Elevation an d Magnetic Data...... 76

Table C: Distance, Velocity, and Depth from Seismograms 84

Appendix II: Reproductions of Seismograms ...... 87 ILLUSTRATIONS

Page

Figure 1. Map of Antarctica .... a 0 a 0 • ...... • 2

Figure 2. Surface Elevation Map . .

Figure 3. Velocity-Depth Curves . .

Figure 4. Profiles of Data, Stations 0-320...... 12

Figure 5. Profiles of Data, Stations 320-940...... 14

Figure 6. Profiles of Data, Stations 432-700...... 15

Figure 7. Profiles of Data, Stations 700-940...... 16

Figure 8. Bedrock Elevation Map ...... a17 ...

Figure 9. Density-Depth Curves 20

Figure 10. Density-Depth Curves 20 ...

Figure 11. Density-Depth Curves ...... 021 ...

Figure 12. Density-Depth Curves ...... 6. .. 21 ...

Figure 13. Density-Depth Curves ...... 022 ...

Figure 14. Accum. vs. Density at h = 40m...... 27

Figure 15. Accum. vs. V at X = 50 m 27 p Figure 16. Accum. vs. V at X = 00 m 28 p Figure 17. Accum. vs. V at X = 200 m 28 p Figure 18. p vs.-ln p at h = 40 m 29 1 -cosh-vs. Figure 19. -In p at h 40m...... 29 A G Figure 20. Eights Station (432) Trave 1-Time Curve ...... 30 X2 . 2 Figure 21. x vs. T , Station 432 ...... 032 ...

Figure 22. Temperature vs. Depth, Sta tion 432...... 32

Figure 23. Station 432 Profile .4.9. 32

Figure 24. Magnetic Anomaly Map .. 42 Page

Figure 25. AK vs. AD...... 43

Figure 26. Magnetic Anomaly Model ...... 43

Figure 27. Magnetic Anomaly Model...... 43

Figure 28. Diurnal Magnetic Variation Curves...... 49

Figure 29. Diurnal Magnetic Variation Curves...... 50

Figure 30. Diurnal Magnetic Variation Curves...... 51

Figure 31. Diurnal Magnetic Variation Curves...... 52

Figure 32. Diurnal Magnetic Variation Curves...... 53

Figure 33. a vs. Distance from Eights...... 54

Figure 34. a vs. A ...... 54

Figure 35. Travel Time Curve, Station 796...... 56

Figure 36. Profile, Station 796...... 58

Figure 37. Free-Air Anomaly Map...... 61

Figure 38. Bouguer Anomaly Map ...... 62

Figure 39. Bouguer Anomaly Section AA'...... 64

Table 1. Reflection Travel Time Data...... 8 Table 2. Accumulation Determined from Seismic Data and Near Surface Glaciology . 26

Table 3. Summary of Rocks Collected .. . 40 INTRODUCTION

Oversnow traverses in West Antarctica before the 1961-1962 austral summer showed great irregularities in the subglacial topography (Bentley, 1962). The sub-sea-level Byrd Basin separates the Ellsworth Mountains from the mountains of contrasting geology in northern Marie Byrd Land. The Antarctic Peninsula appeared to extend southward to connect with the Ellsworth Mountains (Bentley et al., 1960) separating the Ross and Filch- ner Ice Shelves. A rather critical gap remained in the part of Ellsworth Land and the part of the Antarctic Peninsula south of George VI Sound. Consequently a seven-man party, airlifted to the jones Mountains with vehicles, carried out 1700 km of geophysical, glaciological and limited geological traverse observations between 30 November, 1961 and 5 February, 1962. The map of Antarctica (Fig. 1) shows the region studied. (The name "Antarctic Peninsula" as used herein refers to the grounded ice or rock above sea level, east and north of Eights Station.)

This report presents the results including the reduced data, of the altimetric, seismic, gravimetric, and magnetic observations. Deductions about the glaciology and crustal geology of the area are attempted using these data and other glaciologic, topographic, geophysical, and geological information available.

The route is shown in Figure 2, a map of snow surface elevation constructed from surface altimetry observations made on the Antarctic Penin- sula traverse (APT) and on the Ellsworth Highland traverse (EHT) (Bentley, 1962), using the usual interval system common to the antarctic traverses.

Measurements were also taken on two flights using radio and aneroid altimeters, which provided additional control. Maximum surface relief in the area is 2 km. North and west of Eights Station is a featureless snow surface about 1000 m in elevation; south of the station the surface drops down toward the Filchner Ice Shelf and approaches sea level. To the east there is an abrupt rise; numerous mountains and nunataks protrude through the snow. Ice sheet elevations in excess of 2000 m exist; the maximum elevation of the peaks observed is about 2400 m. This eastern area was studied in the most detail.

Throughout the traverse ice thickness was measured at 25 locations by seismic reflection shooting at approximately 40 km intervals; these observations showed that there is no continuous topographic connection between the Antarctic Peninsula and the Ellsworth Mountains and that probably a sub-sea-level channel connects the Ross and Weddell Seas.

Refraction profiles were shot at five stations in the eastern section to determine the maximum P wave velocity in the ice and to study the variation of velocity with depth in the upper transition zone from snow I

-2- I 90oW I I I I I I Q0 I I I I I

Fig. 1. Map of Antarctica showing area studied. 1. Antarctic Peninsula; 2. Ellsworth Land; 3. Marie Byrd Land; 4. Ross Ice Shelf; 5. Ellsworth Mountains; 900 E 6. Filchner Ice Shelf. I mm-m-m -- m m m -= = - -I

950 900 850 800 750 70 -/ _ BELLINGSHAUSEN SEA do.I

J0 NEES MT SA 40>\EIGHTS COAST coo

740 75W 2 2 ~SCATTEREO

ELLSWORTH LAND 740

/#0 . IrOo 76, 14STATION&£ @ 56 £To 0do9p,a

/ #

750

950 90 ° 85 ° 800

Fig. 2. Snow surface elevation map showing traverse routes. APT stations numbered at approximately 1.45 km intervals. -4-

to ice. Wide-angle reflection profiles with shots fired up to distances of 5 km from the geophone line were also attempted in order to study the velocity variation at depth within the ice. Unfortunately, the rock topography was quite rough in most places, and wide-angle reflection profiles were successful only at Eights Station (station 432). At station 796 the refraction profile was extended to 18 km to study the velocity structure of the upper crust.

Gravity observations were made and free-air anomalies were calculated at 6 km intervals throughout the traverse. Bouguer anomalies were determined where the ice thickness was known from reflection shooting and at bedrock outcrops. A nearly continuous record of total magnetic intensity was measured. These data will be discussed in detail.

I I -5-

I OBSERVATION AND ANALYSIS OF DATA

Seismic data. The reflections obtained on the traverse were quite good throughout the area. A Texas Instruments 7000 B seismograph system was used with twelve or twenty-four 20-cps geophones spaced 30.5 m apart. Good reflections were observed at wind speeds of 17 m/sec with a low- pass filter of 215 cps. Linear gain with 10-db steps was always used to allow comparison of amplitudes. High-pass filters of 90 cps were some- times used at the higher elevations to remove persistent shot noise associated with colder firn. The charges varied in size from 70 g of prima- cord to 2.5 kg of Nitramon, but usually a 500-g Nitramon primer was fired at 2- to 4-m depths. The thickness of the ice varied between 440 and 2110 m. Appendix II presents the portion of a typical record containing the reflected arrivals from each station. Behrendt (1963) presented 10 of these records in their entirety but at a much reduced scale.

As can be seen from examination of the seismograms reflections were very sharp, and shallow sub-bottom reflections were common throughout the area (e.g., the record from station 404). The topography of the area was quite rough; apparent dips in excess of 200 were not uncommon. The steep dip of the ice-rock interface is evident in the record of station 764 by the large stepout of the reflection. In addition to the first reflection from the rock surface nearest the shot point, a second reflection of about equal amplitude can be seen. It is likely that this is an echo from another portion of the glacier bed rather than from a lower layer. Second reflections of poorer quality can be seen on the same record behind both echoes. It was always possible, by examining the frequency, relative amplitudes, stepout, and time interval of the arrivals, to distinguish between sub- bottom reflections and later echoes from more distant topography. At least two seismograms showing bottom reflections were recorded at each station.

The portion of the record at station 432 (Eights Station) shows a phenomenon frequently encountered in West Antarctica. An early reflection of poor quality can be observed about 0.2 sec before the main reflection. Al- though the reflection is difficult to see in the figure, it was substan- tiated by a number of shots at several locations in the area. This reflection from a horizon within the ice has been termed Re and will be discussed in tiore detail later.

"elocity-depth curves were constructed by numerical integration from the P wave arrival times at the five refraction stations by assuming a continuous velocit, increase with depth as described by Slichter (1932) (Fig. 3). The maximum velocities are reached at about 150 m below the snow surface, which is shallower than the 250 m observed in the colder areas of Marie Byrd Land (C. R. Bentley, personal communication). From these velocity-depth curves, a correction of 0.057 ±0.001 sec, for a ray traveling vertically through the upper 200 m, was obtained; this was used in the computation of the ice thicknesses from the reflection records. The maximum P wave velocities were: station 432, 3870 m/sec; station 604, 3840 m/sec; station 700, 3840 m/sec; station 796, 3870 m/sec; station 908, 3840 in/sec. The small variation in the maximum velocities is probably the result of the fairly 5000

______4000 ______I__ __ -~ ___

(I) \300C

Q)oo200C "% -_j !

1000

0 0 20 40 60 80 100 120 140 160 180 200

DEPTH (M) Fig. 3. Velocity-depth curves for the five refraction stations.

- -mm ------m m I~--- I = -7-

constant mean annual temperatures which average -22 ±2.6'C using Shimizu's data (personal communication). Velocity-depth curves were also calculated to the depth the refracted wave penetrated on the 330 m reflection spreads. These results are tabulated in the appendix and will be discussed in the section on glaciology.

Throughout the traverse ice thickness was calculated from the measured reflection time (corrected for the velocity gradient in the upper 200 m) using the average or maximum velocity in ice below the firn layer as discussed in a following section. The expression used was

H = (T/2 - 0.057) Vp + 200 where H ice thickness, T = reflection time, and Vp = P wave velocity below 200 m. Table 1 gives the principal facts for each of the seismic reflection stations. TABLE I Antarctic Peninsula Traverse Seismic Stations

Surface Reflection Ice Bedrock Apparent Station Latitude Longitude Elevation Time Thickness Elevation Dip ±1' ±4' ±50m ±0.001 sec +20m +70m ±10

0 224 74014'S 84 46'W 1055 0.562 1070 -20 5 *1500O ' 256 74013 83015' 928 0.648 1230 -300 ' 803300o 288 74011' 81041 918 0.604 1150 -230 17 SE 320 74003' ' 80030 857 0.700 1330 -470 60S 352 74022' 79027 ' 1179 0.580 1100 80 ' 6 OSW 382 74041' 78037 820 0.553 1050 -230 7 ONE 404.4* 74056' 78000 ' 560 0.906 1710 -1150 0 ' 14 N 432 75014 77009' 442 1.114 2110 -1670 10 ' 464 74051' 76000 715 0.279 520 200 130S 496* ' ' 74052 74028 1041 0.238 440 600 IE 604 ' 74038 71003' 1802 0.399 750 1050 17 0N 636 74016' 70010 ' 1434 1.073 2050 -620 ' 4 ONE 668.1 73054 69026 ' 1215 0.825 1570 -360 1 0 6 SW I 700 73032' 68040' 1045 00 0.647 1230 -180 130S I ' 732 73043 67017 ' 1575 0.665 1260 320 0 ' 1 E 764-1 74004 66036 ' 2120 0.576 890 1230 3 796 ' 0 7 74027 67008' 2150 0.610 1160 990 7 N ' 808 74037 67028' 2029 0.568 1080 950 1 ' 60S 840 74058 68011' 1721 0.253 470 1250 130SE 864. 75001' 68052 ' 1623 0.475 900 720 2 ' 8 OE 908 75016' 70050 1253 0.300 560 690 ' ' 5 OSW 940 75027 72002 777 1.020 1930 -1150 6 ONE ' 976 75034' 73037 524 0.878 1660 -1140 60E 1008 75022' 74054' 520 0.732 1380 -860 20 SE 1028 75018' 75054' 438 1.019 1930 -1490 1.20 SE

Ice velocity refraction station ,Eights Station 1 Long refraction profile True dip

-m mm- m ----m- = -m -m-I I = -9-

Gravity and elevation data. LaCoste and Romberg Geodetic Gravimeter #5 was read at 6 km intervals throughout the traverse. Primary bases at McMurdo and Byrd Stations (Behrendt et al., 1962) were used and direct ties were made by aircraft to Camp Minnesota at the start of the traverse, and to Eights Station at its terminus. The station at Camp Minnesota is 73029'21"S, 940 25'00"W, elevation 558 m, about 30 m east of the presently buried Jamesway hut; G = 982.6483 gals. The station at Eights is 75*14'41"S, 77*06'22"W, elevation 452 m, 8 m west of the Camp Sky-Hi magnetic hut; G = 982.7038 gals. Ties to these secondary base stations were not repeated so an accuracy of ±0.3 mgal is estimated on the basis of a statistical study, including this gravimeter, over the North American calibration range (Behrendt, 1962). The estimated accuracy for the observed gravity on the traverse is ±1 mgal or better. Elevation uncertainty is the greatest source of error in using the gravity data, as position location is accurate to ±1' of latitude or better, corresponding to ±1 mgal in theoretical gravity.

The elevations were determined by the usual interval method common to antarctic traverses. This consisted of simultaneously reading four pairs of Wallace and Tiernan aneroid altimeters at 6-km intervals (travel time about one hour) with a 6-km separation between the four instruments in the lead vehicle and the four with the remainder of the party. In this manner each station was occupied twice and corrections were made for temporal changes in pressure. Intermediate altimeter observations were made using one instrument while underway at 0.75 km intervals. These data were tied to the 6 km stations and provide a detailed picture of snow surface undula- tions along the route. They are tabulated in the appendix. The estimated standard deviation for the measurement accuracy of the change in elevation over a 6 km interval is jAh = ±2.36 m neglecting the pressure error. The cumulative error in elevation at Eights is ±25 m, UH = a,hjn, where n = number of intervals. The elevation of 452 m determined for Eights is 11 m higher than that obtained by comparing observed and theoretical mean sea level pressures computed for several months by the U. S. Weather Bureau (data personally communicated by W. S. Weyant). As the portion of the traverse beyond Eights is a closed loop, the cumulative error at the farthest point (station 740) is ±28 m relative to Eights where H = G2t4 - This is the maximum error; the errors at stations closer to Eights are correspondingly smaller.

Semi-stationary pressure systems may have introduced systematic errors. Although the elevations were corrected with the 700 mb pressure maps published for each day by the International Antarctic Analysis Center, Melbourne, sizeable errors could still remain as these maps are compiled from sparsely scattered data in this area. During the period of the traverse the only persistent system shown was a low pressure cell in the Weddell Sea present about two thirds of the time,which was corrected for using the 700 mb maps. Estimating the total elevation error from both random meas- uring error and pressure error as the maximum measurement error at the farthest station, of about ±50 m, a corresponding error in free-air anomaly of ±15 mgal results. The relative error between two adjacent stations is about ±-0.7 mgal. The cumulative error in free-air anomaly between two adjacent seismic reflection stations about 40 km apart is ±2 mgal. -10-

Reflections were shot at approximately 40-km intervals, except in mountainous areas where direct measurement of rock elevation was possible. Gravity readings were made at 6-km intervals between reflection stations. Bedrock elevation at each gravity station was calculated by multiplying the difference in free-air anomaly from the previous seismic station by the empirically determined factor of 20 m/mgal. This factor was used instead of the theoretical 13.5 m/mgal for an infinite slab and I densities of 0.9 and 2.67 g/cm 3 for ice and rock. It was obtained by basing all depths and differences in free-air anomaly on one station (Eights Station) and trying various factors to find the best fit to all of the seismic reflection depths. The resultant factor is an indication I of the departure of the rough topography from infinite slab theory since it is unlikely that variations in rock density could account for the in- creased factor. The error of closure at the following seismic station, based on the difference in free-air anomaly from the previous seismic station, was spread linearily over the intervening gravity stations.

The maximum cumulative error in bedrock elevation calculated from differences in free-air anomaly between adjacent reflection soundings due to elevation error is only ±40 m, which is well within the limit of accuracy imposed by the gravity effect of the sub-ice topography. Bentley (in press) has estimated the average error due to topography in determining bedrock elevation from gravity as ±300 m for all Antarctic traverses.

Bouguer anomalies were calculated only at seismic reflection stations or at rock outcrops. The Bouguer anomalies used in this study were computed by correcting the free-air anomalies for the ice or rock mass between the surface and sea level and the mass deficiency, if any, between ice and rock below sea level assuming densities for ice and rock of 0.9 and 2.7 g/cm3 respectively as in the calculation of Bouguer anomalies at sea. The error due to the ±50 m elevation uncertainty is -13 mgal for a total ice column I or ±9 mgal for a total rock column. The uncertainty in the reflection measurement of ice thickness is ±20 m which corresponds to ±1.5 mgal in the Bouguer anomaly. Combining these errors gives an estimates of about ±13 mgal accuracy, neglecting the topographic error. Because reflection soundings are made at a point and the gravimeter averages the mass attraction over an area, the effects of the surrounding topography may be appreciable. For this reason it is not usually possible to use Bouguer anomalies meas- I ured on ice sheets for quantitative studies of density variations due to local changes in geology. In the area covered by the APT the bottom relief is too large to allow anything but a few qualitative inferences as to local I mass distributions. A more complete treatment of this problem is given below for one area where detailed seismic soundings were available. When large areas are studied, the regional Bouguer anomalies can provide useful information on variations of general crustal structure, as will be des-n cribed later in this paper. I I I I -11-

Magnetic data. The earlier oversnow traverses in Antarctica, begun during the IGY, yielded magnetic data of only limited value, as the instruments used measured only relative changes in vertical intensity and suffered from calibration changes, temperature effects, and instrument drift. Data were spaced at 5- and 9-km intervals and could not be corrected for temporal changes, as the observations were made too far from base stations. Aeromagnetic profiles were an improvement as they gave rapid, absolute, and continuous measurements of total field and largely eliminated storm effects by their short time duration. Position uncer- tainties and smoothing out of geologic effects by the flight height above the terrain limit the aeromagnetic method.

On the APT a different system of magnetic observations was used. The party used two Varian M49 proton precession magnetometers which measured absolute total field to 10 y accuracy and were read to ± 5 y. An interval method similar to that used for the altimetry was employed. The lead vehicle traveled about 6 km and 1 hour ahead of the remainder of the party. The sensing head, filled with heptane, was towed on a small, fiberglass, non-magnetic sled about 30 m behind. The instrument was read while underway at 0.75-km intervals (or less when over thin ice). An identical procedure in the following vehicle allowed reoccupation of every station. At 6 km intervals simultaneous observations were made (together with the altimeter observations) using radios for communication. The method allowed correction for diurnal change and recognition of magnetic storms. Crossing each anomaly twice gave a much greater degree of confidence in the existence of individual anomalies. On the basis of these comparisons, the data from stations 64 through 112 had to be re- jected. When the party was stopped for the night or other extended pe- riods, the U. S. Coast and Geodetic Survey observer made a series of observations of all components of the magnetic field (Wasilewski, 1963).

The averages of the traverse data and the U.S.C.G.S. data were used as bases for the overnight stations. The standard deviation of these absolute values is ± 25 y. The relative accuracy of the intermediate stations was estimated by computing the standard deviation of the data used for the diurnal curve from the smoothed diurnal curve drawn through them; this was ± 7 Y Figures 28-32 show some of the diurnal curves constructed from the interval data. This paper discusses only residual profiles constructed by removing the regional field arbitrarily by hand. The absolute data together with aeromagnetic data will be used with the aeromagnetic data collected during the 1963-64 field season to study long wave length anomalies as described by Behrendt and Wold (1963). -12-

K. I Zi W E +500 I - I

A^ 0 I" c=J-e_ _ _ . : -, I I + 5 I -qX I I I I I I I I

L-L I

I I I I I 0 100 200 KM I Fig. 4. Data profile from stations 0 to 320. Flags indicate reflection soT,ndings of ice thickness. I I -13-

RESULTS

The data have been plotted in profile form and are shown in four sections (Figs. 4-7). Figure 4 show-s the section from stations 0 (Camp Minnesota) to 320. The residual magnetic intensity profile shows a number of anomalies up to 200 y with a central area of few anomalies. The abrupt change in the magnetic field just east of station 224 is coin- cident with a rise in the bedrock from a valley as shown by the free-air anomaly. The next section, Figure 5, extends from stations 320 to 940. At stations 1008 and 976 the bedrock rises to about 1000 m below sea level, and the free-air anomaly indicates that it becomes higher. A positive Bouguer anomaly and 800 and 900 y magnetic anomalies are associated with these features. Figure 6 is a section from Eights to station 700 which crosses the southern portion of the base of the Antarctic Peninsula and drops down toward George VI Sound on the north. The Bouguer anomaly shows a regional decrease with an increase in elevation as would be expected from the isostatic compensation of this higher rock mass. The magnetic field shows many irregularities with two anomalies of about 1000 y amplitude. Again there is a correlation between these large positive anomalies and free-air anomalies. No Bouguer anomalies were measured directly over these features. Figure 7 shows another crossing of the peninsula from stations 700 to 940. The Bouguer anomaly fluctuates because of the rough topography and possible rock density variations but shows the regional isostatic compensation of the higher elevation. There is a sharp magnetic anomaly of about 1700 gammas total variation associated with a positive Bouguer anomaly probably indicating higher density, higher susceptibility rock.

Figure 8 is a map of bedrock elevation in the area constructed from the reflection and gravity data. There are three main topographic prov- inces. The subsea-level area observed in Marie Byrd Land continues north around the Sentinel Range and curves south of Eights Station toward the Filchner Ice Shelf; its depths are in excess of 1000 m below sea level. To the north along the coast of the Bellingshausen Sea the rock surface is about at sea level. The eastern section is very rugged. A large portion of the area is higher than 1500 m and peaks which extend up to 2400 m protrude through the ice. If the ice were removed, the Antarctic Peninsula would be an island, separated from the Eights Coast area by a narrow sub- sea-level channel as shown in Figure 8.

The seismic investigations at station 432 which studied the Re reflection phenomenon and at station 796 which measured upper crustal velocities will be discussed in the following sections on glaciology and geology respectively. -14-

K N S + 1000- I I +500- I 0- PM a,a I + 54 I I

-54 I I +100 I I

LLJ K .,ll I I i I

0 100 200 KM I Fig. 5. Data profile from stations 320 to 940. Flags indicate reflection soundings of ice thickness. I I -15- NV +1000 A A E +500

(p3

q~zt 0 cz,t

LkQj

QSz

Q)Cr

A +IOC_ I (~ I ApfAA i A - n

+5C

604 C -5553 585

496505 IC E 63668 464'-A'A700 i i - n - rY-- -H--- 1 - '-- - 1l 9 -AZA M- :I'.]- +1000--50 I -r- 432 NEIGHTS STA.

-L- 0 L -AM L\1 -AIAv'\\\\',¢,CROC " i l 4x'--!PUl-ROC Kb

I I I I I I I I I I x I . -1000 Lqvlc--v-qc--Ic r I x I I I I ------I - - I - I'd-

-2000 x x xx N-x -,,, x \ x -, - N\ \ - - I

m a I I I I I 0 100 200 KM Fig. 6. Data profile from Eights Station to station 700. Flags indicate reflection soundings of ice thickness or rock outcrops. -16- K N S I I I K, I I I I I I I I I I I I tij

I II I I 0 100 I 200 KM I Fig. 7. Data profile from stations 700 to 940. Flags indicate reflection soundings of ice thickness or rock outcrops. Reflection soundings at points between 796 and 808. I n mmm m m m m m - m - I mm

85 3' 7

E O RG E I S OU

9LG RTOE N GL IS H qD E I GH T SE 500

ST "50. SCATTERED

-500

I .. STATION... I,ec

EI G HT , STATION // F I

Figure 8.

-19-

DISCUSSION OF

GLACIOLOGICAL RESULTS -20- A P T DENSITY VS DEPTH I N . I .9c 2 I ~256 .8c) 224 I .7C) () I .6C ) I ) .5C I 4.C I

.3CIf 20 40 60 80 DEPTH METERS I

Fig. 9. Density-depth curves for reflection stations 224-320. I

_APT DENSITY VS DEPTH I 1.00 I .90 464 38249-,6 4-04.1-

i I 4-- N) .80 28~ (~) 70 old-- i i I 7 .60 o/ I K -i -l .50 LU I 40 I

.30 6 S L 20 40 60 80 I DEPTH METERS I Fig. 10. Density-depth curves for reflection stations 382-528. -21- APT DENSITY VS DEPTH 1.001

5 7 2 _ _ .9 0

3.70 - / ...o-w ..... 764

).60 - ~.80 .50-

.40

20 40 60 80 DEPTH METERS Fig. 11. Density-depth curves for reflection stations 572-764.

APT DENSITY VS DEPTH .9011

.940 8164

v.50

Kn .50

I. b40

20 40 60 80 DEPTH METERS

Fig. 12. Density-depth curves for reflection stations 840-1028. APT DENSITY VS DEPTH I.-OC 796904 .9c

N) .8C ) .7C

.6C rI. K ) .5C cz~ .4C

.3C 20 40 60 80 100 120 140 DEPTH METERS

Fig. 13. Density-depth curves for refraction stations.

m mm m m m m I mm-- SNOW DENSIFICATION

From the compressional wave velocity vs. depth curves calculated for each reflection station, density vs. depth curves were constructed using the empirical expression Robin (1958) showed to be valid below depths of 15 m:

P0 2.21 x 00061 V + .059, (1) where p = density, g/cm3; Vp = compressional wave velocity, m/sec; and T = temperature, 'C. Figures 9-13 show the results of these calculations using the 10 m temperatures (Shimizu, personal communication). The variations in these curves are probabl the result of the wide range in annual accumulation values (20 to 50 g/cm yr) since the standard deviation of the mean annual (10 m) temperatures is only ±2.6'C. This suggests a method of determining quantitative estimates of mean annual accumulation from the seismic data.

Pit measurements of accumulation values for 12 stations (Table 2), furnished the author by Shimizu, were used with a value for Eights Sta- tion determined from one season's observed snow accumulation. Figure 14 is a graph of accumulation (A) vs. the density (p) at 40 m depth (h). The straight line shown was fitted by least squares to the data and the standard deviation of the points is ±4.7 g/cm2 yr in terms of accumulation. This graph shows an inverse relation between accumulation and the density at 40 m at this relatively constant temperature.

Another empirical study was carried out using the velocity vs. distance curves (Appendix I) constructed directly from the travel time curves. Figures 15-17 compare accumulation with compressional wave velocities recorded at distances of 50, 100, and 200 m from the shot point, respectively. Assuming linear relationships for these graphs also, the standard deviations in terms of measured accumulations from the least square straight lines are ±6.0 g/cm2 yr, 5.8 g/cm2 yr, and ±4.5 g/cm 2 yr for 50, 100, and 200 m distances respectively, the percentages being relative to the average accumulation of 38 cm. The depths corresponding to the velocities ateach of these distances (X) were measured and averaged from the velocity-depth curves with the following results: X = 50 m, h = 11 m, the standard deviation s = +-3.3 m; X = 100 m, h = 21 m, s = -4.2 m; and X = 200 m, h = 41 m, s = +2.7 m. The least scatter from the straight lines of these three figures, was for X = 200 m (Fig. 17) corresponding to a mean depth of 41 m; this is essentially equivalent to Figure 15 for accumulation vs. density at 40 m depth.

I attempted an explanation of these empirical results on a theoretical basis. Bader (1962) and Landauer (1957) gave the following relations for the rate of snow densification (-v):

-v =- = c sinh o__(2 p dt o -24-

a = At (3)

2 where t = time; a = load, g/cm = p h, p = average density from the surface to a depth h; ao 700 g/cm 2 ; and c is a constant depending on snow type and temperature.

CI = c sinh At dt (4)

P T0 integrating and rearranging gives

In p =c CI cosh - + k (5) AGO o where k is a constant of integration. Using the 2 m pit density data furnished by Shimizu and the density-depth curves of Figures 9-13, values of a at 40 m depth were calculated for each of the 13 stations of Figure 14 by numerical integration. These were found to show the following apparently linear relation with p at 40 m depth (Fig. 18):

P = .54p + .215 (6)

Using this expression introduced an error of ±0.9% in p. Within the range of densities of Figure 14,

1 = 1.445 In p + .919 (7) P with an introduced error ±0.4% in 7. (The error introduced by the assumption a linear relation between and In p is less than that between p and In p in the density range from 0.7 to 0.8 g/cm 3 .) From these relationships a theoretical curve of cosh a- vs. in was calculated and plotted on a 1 graph of the observed data in°Figure 19. The standard deviation of points from the curve is ±3.0% and from the least square fit of a straight line is ±2.7%. Thus the approximation of the linear relationship

cosh _ = 46.93 In oIp + 30.87 (8) has an error of ±3%.

From equations 5, 7, 8: 3

=(1.99 x 104) c + .692A (9 P=(3.88 x 104) c + A (k-.636) 39 with a combined error in p of ±+3.4% where p is in the range 0.7 - 0.8 3 g/cm . The best fit to the observed data was found to be c = 3.9 x 10 4 yr - I and k = -. 42. These gave the expression 3

7.78 - 15. 2 p(0) .69 - 1.06p ( I I -25-

from which the curve of Figure 14 was drawn. The standard deviation from the observed data is ±6.8 g/cm 2 yr compared with ±4.7 g/cm2 yr for the linear fit and ±4.5 g/cm 2 yr from Vp at X = 200 m (Fig. 17).

This discussion leads to the conclusion that in the APT area, at least, where the scatter in mean annual temperatures is small, the compressional wave velocity at 200 m distance from the shot point or the density at 40 m depth can be used to obtain reasonably reliable values of accumulation. The graph of accumulation vs. velocity at 200 m is preferred over the graph of accumulation vs. density because it is much less time consuming to determine a velocity (which can be taken directly from a seismogram) at a given distance than a density at a specific depth.

Determinations of the accumulation were made for all of the seismic stations as shown in Table 2 using Figures 14 and 17. AL and AC refer to values from the straight line and curve of Figure 14; AV refers to the values from Vp at X = 200 m. The standard deviation is ±2.9 g/cm2 yr for the comparison of the three methods. This should be regarded as an indication of the internal agreement of the data rather than an indication of absolute accuracy of the accumulation values. -26-

TABLE 2 I Accumulation Determined From Seismic Data and Near Surface Glaciology I AL from p AC from p AV from Vp Mean Seismic Measuredl Station at h = 40 m at h= 40 m at X = 200 m Accumulation Accumulation lp 9 I 224 47 g /cm-yr 48 g/cm2yr 49 g/cm2yr 48 g/cm2yr 256 44 42 44 43 48 g/cm2yr 288 41 39 45 42 I 320 43 41 40 41 352 44 43 46 44 I 382 37 34 33 32 404 44 43 37 41 I 432 40 42 34 39 40 464 24 28 23 24 I 496 37 34 36 36 26 528 35 32 43 37 I 604 38 35 37 37 46 636 39 37 42 39 34 668 38 36 41 38 41 I 700 40 38 39 39 45 732 47 49 47 48 50 I 764 50 57 51 53 48 796 37 34 37 39 I 840 28 28 27 28 28 864 24 27 23 24 908 29 28 30 29 I 940 23 27 25 25 20 976 40 37 43 40 I 1008 36 33 32 33 35 1028 35 35 24 31

IH. Shimizu (personal communication). I I I -27-

701 1T

ACCUMULATION VS. DENSITY AT h=40m 60 J%d i AL =2.36 (.913 -0) 7.78-15.12 P Ac- .6 9-I.06/P T74 32 256- *0 0 mmmm~,32*668 -,me 6 008

, 30. --m._ A A A i i i cw-)p I--Qd 0i * ~ f 94C k- 4 4- + 1 \50

ni i_I _ I_II_ I I I I I I ".69 .70 71 72 73 .74 .75 .76 .77 .78 .79 .80 .81 .82 DENSITY (GM/CM3)

Fig. 14

(~)

(z~

Z2Z,

01 i 2000 2100 2200 2300 2400 2500 2600 2700 VELOCITY (METERS/SEC)

Fig. 15 60

50 I

C 0 4 I

~30

I0 I

0 I 2500 3300 VELOCITY (METERS /SEC) I Fig. 16 I I I

C\J

ZZ:~

(.3 I 3000 3100 3600 I VELOCITY (METERS/SEC)

Fig. 17 I -29-

1 .760 .780 .820 3 DENSITY (GM/CM )

Fig. 18

0 (~)

.20 .25 .30 .35 40 .45

Fig. 19 -30-

3.01

2.0

LLJt.,

1.0

0 2 3 4 5 6 D ISTANCE (KM) Fig. 20. Travel time curve for wide-angle-reflection profile near Eights Station. -31-

BASAL LOW-VELOCITY LAYER

The Re reflection was first observed on the Sentinel traverse (Bentley and Ostenso, 1960) during the IGY; it was found in very thick ice (up to 4300 m). Since then, reflections of Re have been observed on the Ellsworth Highland traverse (Bentley, 1963) and on the Antarctic Peninsula traverse in thinner ice. As previously mentioned, a wide-angle reflection profile was recorded at Eights Station to study this phenomenon. Shot time was transmitted by radio; tellurometer distance measurements are accurate to +1 m. The travel-time curve is shown in Figure 20. Station 432, the southern end of the profile, is 2.4 km north along the traverse route from Eights Station proper. Re, was observed about 0.2 sec before the vertical bottom reflection; this was not observed at wider angles. The reflected compressional wave and the compressional wave converted to a shear wave at the ice- rock interface, Rpp and Rps, respectively, were observed out to a distance of 5.6 km. Vertical reflections shot at distances of 1 and 3 km along the line showed that the bedrock was essentially horizontal beneath the 2110 m thick ice and that the R reflecting horizon extended throughout the profile. The Re reflection arrivea 0.241 + 0.004 sec before the R 1 reflection at these shot points. A time-squared versus distance-squared plot was made for the wide-angle.Rpp reflections which were corrected for the curved ray path through the firn layer integrated by Simpson's rule. The least-squares fit of a straight line to these data gave an average velocity in the ice section of 3814 + 15 m/sec as shown in Figure 21. The maximum P wave velocity was found to be 3870 + 5 m/sec. Because this is a velocity decrease of only 1.3 per cent, the possibility of anisotropy was examined. Thiel and Ostenso (1961) discussed the results of several investigators and gave an average of 4 per cent higher P wave velocity along the c axis of an ice crystal than perpendicular to the c axis. Analysis of the 300 m deep hole at Byrd Station showed no anisotropy when velocities of the vertically and horizontally measured P waves were compared (C. R. Bentley, personal communication), nor was any preferred crystal orientation observed in the ice core (Gow, 1963). Calculations were made using the geometry of the profile shown in Figure 22, and assuming a random orientation of crystals at the depth at which maximum velocity was measured. Eighty per cent orientation below the zone of maximum velocity with the c axes horizontal and perpendicular to the plane of the profile would be necessary to give the observed velocity decrease. This is highly unlikely, particularly since vertical orientation of the c axes might be expected if recrystallization at depth had occurred (Rigsby, 1960). From these arguments I conclude that there is a lower velocity in the basal layer below the Re reflecting horizon.

An average thickness of 450 m for the layer below the Re reflection was determined from the three separate Re reflections along the line. The P wave velocity in this layer was calculated to be 3640 + 8 in/sec by assuming that there was no decrease in maximum velocity above the Re horizon. Considering the errors in the other velocities, this would probably be accurate to +60 in/sec. The maximum Vs was observed to be 1990 + 10 m/sec, which gave a Poisson ratio of 0.320. From the time intercept of theRp -32- Up I I TEMPERATURE 3.0 VS DEPTH A PT #432 I 500 (EIGHTS STATION)- 2.5_ (r) I

(I* LL K32.0 1000 I

5 I\ I

1500 I.WI.oz______0 5 10 15 20 25 30 I 2 2 X KM

Fig. 21. Time-squared vs. distance- squared of travel times at Sta- I S 000 tion 432 corrected for velocity variations in upper 200 m. -25 -15 -5 TEMPERATURE OC I

Fig. 22. Theoretical depth vs. temperature curve calculated for equilibrium ice sheet using I mean annual temperature, accumulation, and ice thickness at Station 432. I

+1- - I I I L4 I I I I I I I I I 0 2 3 4 5 6 DISTANCE KM Fig. 23. Interpreted veloCJty structure in ice sheet at I Station 432. Flags indicate vertical reflection shots; dashes beneath these indicate reflecting horizons. I I -33-

reflection line an average velocity for the S wave was determined to be 1970 m/sec. After correction for the velocity variation in the firn layer near the surface, an S wave velocity of 1880 m/sec was determined for the section below the R reflection. The Poisson ratio of 0.32 calculated for the basal layer is essentially the same as that measured from the maximum velocities and is a confirmation that the Re reflecting horizon is within the ice and not at the base of it.

The temperature should increase with depth; therefore calculations of the amount of warming that might be expected from geothermal heat flow were made by Robin's (1955) method for an assumed equilibrium ice sheet as thick as that at Eights Station. As shown in Figure 23, the decrease in average velocity due to warming in the zone above Re to a depth of a- bout 1700 m would amount to an average of only 2 m/sec, assuming -2.3 m/sec 0 C (Robin, 1958) for the upper 1700 m; therefore it was neglected. In the lower 400 m of the section, warming could decrease the velocity only about 10 m/sec, which is within the error of the velocity determination. The theoretical temperature at the base of the ice is -120C, or well below the pressure melting point of -1.40 C. It was assumed in the calculation that the ice was frozen to the bottom and, consequently, that there was no heating by sliding at the base; this assumption was verified by means of the theory outlined by Weertman (1961). The geothermal heat flow is assumed to be Qg = 39 cal/cm2yr, and the heat of sliding is

Qs = VT/J

where V = velocity of sliding in m/yr, T = sheer stress at the base of the ice, in bars, and J = 4.185 x 107 ergs/cal, the mechanical equivalent of heat. The sheer stress is given by

T = pgh sin a

where p = average density of ice, g = gravitational field strength, h ice - thickness (2100 m), and C6 = slope of upper surface of ice sheet (2.6 x 10 3) along the profile. The velocity of sliding is given by m V = BT

where B = 81 m/yr bar2 and m = 2 are reasonable values for these constants. Solving these equations, we get 2 Qs = 19 cal/cm yr

A theoretical ice thickness where the bottom surface is at the melting point and no freezing or thawing takes place is given by

ho kL T/(Qg + Qs)

where k = conductivity of ice (1.7 x l05 cal/cm yr °C) and A T = the difference between the surface temperature (i.e., temperature at 10 m depth) and 0 the freezing point. When AiT = 25° C we get h o = 730 m. -34-

In order for the 2100 m thick ice to be at the melting point at the base, the accumulation would have to be

a = hTk/2ch o where c = specific heat of ice (0.45 cal/cm3 OC). When this equation is solved, a value of a = 23 cm/yr is obtained. Since the actual accumulation is about 45 cm/yr ice equivalent, the base of the ice at Eights Sta- tion should be below the freezing point.

A likely cause of the low velocity in the basal layer would be the presence of morainal material. From the following equations we would ex- pect that the average density would increase more rapidly than the average moduli of elasticity for small inclusions of rock particles in the ice. The velocity for the compressional wave is given by V2 = (K + 4 /P I P )3 where K = bulk modulus, t = modulus of rigidity, and p = density. Follow- ing Wood (1941) and Sutton et al. (1957) I assumed the following relations:

1/K x = fi/Ki + fr/Kr

I/Lx = fi/k4Li + fr/lur

Px = f.PI i + frrr r 3 wh e Kx = bulk modulus of basal layer, K i = bulk modulus of ice (8.93 x 2 10 6 dynes/cm 2 ), Kr = bulk modulus of rock (35 x 1010 dynes/cm ), fi = fraction of basal layer that is ice, fr = fraction of basal layer that is 3 rock, px = density of basal layer, pi = density of ice (0.92 g/cm ), Pr = 3 density of rock (2.67 g/cm )2 Ix= rigidity of basal layer, ii = ridity of ice (3.64 x 1010 dynes/cm ), and p.r = rigidity of rock (21 x 0 dynes/ cm2 ). When these equations were solved a value of 13 + 3 per cent was obtained for the amount of included morainal material.

For this amount of included rock particles, the ratio of the difference I to the sum of the acoustic impedances for the ice and basal layers requires that 7 per cent of the incident vertical energy be reflected. The amplitude ratio of the Re reflection to the bottom reflection if 0.18 + 0.04 as deter- I mined from the three vertical reflection stations along the profile. If this material had a compressional-wave velocity of 4.4 km/sec, as measured at station 796 (discussed below), and a density of 2.67 g/cm3 , the ratio I of the amplitudes of the Re reflection to the bottom reflection would equal the observed value of 0.18, allowing for a 7 per cent loss of energy at the R horizon for both the rays incident to and reflected from the bottom. Thus the amplitudes are not inconsistent with the results of the velocity I determinations. The interpreted structure of the ice sheet at Eights Sta- tion is shown in Figure 23. The locations of the vertical reflection shots are indicated by small flags. I

Since no deep drilled holes have been made to the depths required to determine experimentally the existence of this material in the ice at Eights 3 I -35-

Station, the interpretation cannot be positively verified at the present time; however, it seems to be the only reasonable pcssibility. Cores taken in the area of the antarctic ice sheet near Mirny Station where the ice is very thin (about 40 m) (Yevteyev, 1959) have shown 9 per cent of morainal material in the lower 20 m of the ice.

Weertman (1961) discussed a possible mechanism for the formation of inner moraines in ice. His method requires the existence of areas at the base of the ice sheet where melting takes place adjacent to areas where the ice is frozen to the base. The meltwater could pick up morainal material, flow outward under pressure to the area where the base of the ice is below the melting point, and refreeze. He showed that if the border separating the freezing and thawing areas oscillated laterally owing to climatic changes, bands of morainal material could be built into the ice from beneath.

Using the same relations that showed that the base of the ice at Eights Station is below the freezing point, I examined the area about 100 km up- stream (NNW) from Eights Station. Figure 2 shows that there is a steeper average surface slope in this area than at Eights Station, and a greater heat of sliding at the base would be expected if the ice were not frozen to the bottom. Since the ice is twice as thick at station 432 as at 382 (see Table 1), in order to conserve mass the velocity of flow should be twice as fast at station 382 as at station 432 across a section of equal width that is parallel to the contour lines. For sin c = 8 x 10 - 3 and h = l0 0 m, as determined at station 382, the heat of sliding is Qs = 67 cal/ cm yr, or over 3 times as great as at Eights Station. Since the surface temperature is -250 C, the theoretical accumulation should be 39 cm/yr for the bottom to be at the melting point.

Table 2 gives 30 cm/yr for the accumulation at station 382 which suggests that the bottom temperature may be at the melting point. At any rate this accumulation rate is close enough to the theoretical value of 39 cm/yr that the basal temperature could fluctuate from freezing to thawing with relatively small changes in accumulation. Of course, the fluctuations would have to persist for several thousand years for the effect to reach the bottom of the ice. Thus it is conceivable that Weertman's mechanism could have produced included morainal material in the'basal layer of the ice which has since flowed down to where it was observed at Eights Station. Even if this mechanism could explain the morainal material in the interpreted section discussed here, it has not been shown that it would explain the presence of the Re reflection in other parts of West Antarctica. The mechanism by which morainal material could be carried and introduced into the ice throughout large portions of West Antarctica to thicknesses greater than 400 m is not explained here. Since this phenomenon, if existent, would be intimately involved in the mechanics of glacial erosion, it is certainly worth further investigation.

No other wide-angle reflection profiles were successfully completed because of the very rough bottom topography throughout the eastern area of the traverse, although four others were attempted. It seems possible that a significant amount of morainal material is not included in the ice sheet -36-

of the Antarctic Peninsula east of Eights Station since no Re reflections were observed on this section of the traverse. When the calculations of ice thickness were made from the reflection records for the high portion of the Antarctic Peninsula, the maximum velocity was assumed to extend to the bedrock. In the area near Eights Station where the ice is thickest, the average velocity of 3815 m/sec below the firn layer observed at Eights Station was used in calculating the ice thickness. The maximum error which could result from using the wrong velocity is +20 m.

U I I I I

I I I -37-

DISCUSSION OF GEOLOGICAL RESULTS -38-

SUMMARY OF SURFACE GEOLOGY

Before the 1961-1962 austral summer no rock specimens had been collected in the region covered by the APT, and the geology was essentially unknown. This area is in the center of a triangle whose apexes are in areas of known but contrasting geology. The geology of the Jones Mountains, Ellsworth Mountains, and northern Antarctic Peninsula will be summarized briefly before describing the rocks of the APT area.

The Jones Mountains, discussed by Craddock, Bastien, and Rutford (1963) (Fig. 2), are adjacent to Camp Minnesota, the starting point of the APT. They consist of a basement complex overlain by a volcanic series. The basement complex includes a granite with a minimum K/A age of late Triassic, felsitic dikes with a minimum K/A age of middle Cretaceous, basaltic dikes, and highly altered igneous rocks. The volcanic series is made up of olivine-basalt tuffs, agglomerates, flows and hypabyssal bodies of late Cenozoic age at least 500 m thick. The basalt may contain up to 5% titaniferous magnetite. Numerous outcrops of geologically young volcanic rocks occur to the south and west of the Jones Mountains in West Antarctica (Doumani and Ehlers, 1962; T. S. Laudon, personal communication). Craddock, Bastien, and Rutford, (1963) point out that this area of West Antarctica cannot be considered a simple volcanic archipelago, as the late Cenozoic olivine basalts rest with marked unconformity on a Mesozoic or older plutonic basement. Rocks as old as late Paleozoic and character- istic of oroginic regions occur in this area.

The Sentinel Range (Figs. I and 2) is part of the Ellsworth Mountains extending north-south for 350 kIn. Craddock, Anderson and Webers (1963) describe these mountains as being composed of deformed metamorphosed sedimentary rocks with an exposed section probably greater than 14,000 m. Clastic rocks, especially quartzite, conglomerate, and pelite, predominate with no established unconformity. They observed a thick carbonate unit near the base of the section. The fold axes are roughly parallel to the trend of the range. Fossils are scarce but indicate that most of the exposed section is of Paleozoic age, with the youngest formation being probably no older than middle Paleozoic. Cambrian fossils were collected in the center of the section implying that the lowest portion of the section is possibly Precambrian. A few basic dikes and sills were observed in the sedimentary rocks of the Heritage Range in the southern Ellsworth Mountains.I There was a minimum uplift of 7000 m. The age of the orogenesis is later than middle Paleozoic or younger (C. Craddock, personal communication).

Adie (1962) has discussed the geology of the Antarctic Peninsula north and east of the area covered by the APT. He cites a "basement complex" of unknown age (Adie, 1963) south of Marguerite Bay (69 0 S), and3

I I -39-

occurrencesof intrusive and volcanic rocks. No Ordovician-Devonian rocks are presently known in the Antarctic Peninsula. According to Adie, the Carboniferous was characterized by the development of the Andean geosyn- cline with associated rapid deposition of the Trinity Peninsula graywacke facies sediments. Halpern (1963) states that this mobile belt was present in the Cretaceous based on fossils and K/A age determinations in the northern part of the peninsula. He sites eugeosynclinal characteristics, including a minimum of 4000 m of clastic sediments, the regional occurance of Jurassic and Tertiary volcanic and hypabyssal rocks, and acidic and basic plutons. Adie (1962) states that the Antarctic Peninsula achieved much of its present elevation in late Cretaceous - early Tertiary, at which time large scale batholithic intrusion belonging to the Andean intrusive suite took place. There has been volcanic activity intermittently since early Miocene time which he considers related to that in the Jones Mountain area and further west.

On the APT, time for geologic field work was quite limited; I made reconnaissance observations and collected rock specimens at 11 locations. Because of the lack of time most of the many accessible peaks and nunataks in the area east of Eights were not visited. Laudon, et al., (1964) have described these results, which Table3 summarizes briefly. They con- lude that the peaks in this area are part of a chain of fold mountains occupying the site of a former Cretaceous mobile belt. Volcanic rocks postdate sediments where relations are determinable.

I conducted an aerial reconnaissance which showed the Antarctic Peninsula ranges in the APT area (Fig. 2) to be continuous to the north- east with the mountains of the northern Antarctic Peninsula. Since the lithologies and structure are similar to those reported further north in the peninsula it is likely that the depositional, volcanic, and intrusive history of the area is related to chat of the northern portion of the Antarctic Peninsula. No examples of the basement complex discussed by Adie (1962) were observed on the APT; it is certainly possible that there may be outcrops of basement in some of the hundred or so peaks that were not visited. -40-

TABLE 3

1 Summary of Rocks Collected on the Antarctic Peninsula Traverse

2 Peak S. lat. W. long. Stk. Dip Rock types V (km/sec) (U.S.G.S. Designation)

DIM 74055 ' 76000 ' 1230 NE Dacite

ElM Mt. Rex 740561 75058 1230 NE 3 Dacite 5.6

HIM (Johnson 74052 ' 74002 ' 0890 700S Quartz wacke Nun.) (Cretaceous)

' IIM (Barnes 74059 72049 ' 0510 400SE4 Dacite, 5.2 Nun.) 0210 70ONW andesite

NiM 75002' 72018 ' 1450 70ONE Quartz monzo- nite, hornfels, argillite, andesite

' D2M 74050 71035' 0790 30ON arkose, dacite

0 U2M (Shimizu 7506 68 20' 1230 850 SW lithic wacke, 5.85 Nun.) feldspathic wacke, basic dikes

' P3M 75003 69015 ' 0900 65 0N arkosic wacke, 5.51 black shale

E4M 75010 ' 70011 ' 1680 30 0E dacite

B4M 75010 ' 70009 ' 0380 andesite, dacite

15M 75021 ' 71026' 0840 650 N conglomerate, arkosic wacke

IFrom Laudon et al., in press. 2 Velocities measured by M. Manghnani (personal communication).

3 Dip varies, 430 to 840. 4Dips and strikes of two intersecting sets of quartz veins. -41-

MAGNETIC ANOMALIES

Figure 24 shows the residual magnetic intensity from the APT and EHT and also includes 3 aeromagnetic flights. Parts of Flights 1, and B from Behrendt and Wold (1963) are shown as well as a portion of Pro- ject Magnet Flight 701 furnished me by the U. S. Naval Oceanographic Office. EHT vertical intensity data at 6 km intervals were obtained from C. R. Bentley. The smoothing of the anomalies along the aeromagnetic profiles compared with the APT data, because of the elevation of the aircraft, is apparent. Flight 701 was flown at 5000 m elevation; Flights I and B were at about 1700 m. The position of Flight 1 in the area of the 75'S parallel between 850 and 90'W has been adjusted somewhat to the north from that shown in Behrendt and Wold (1963) on the basis of snow surface elevations determined in flight compared with those measured along the EHT (Bentley, 1962). There appears to be a possible error in position of Flight B where it crosses Flight 1. No elevation data or notes are available for this flight (flown by Thiel), that would allow any adjustment. No depths were computed using the data from Flight B or the widely spaced data of the EHT.

In the volcanic Jones Mountains there are many anomalies. To the east of this area there is an abrupt decrease in anomaly amplitudes. This is a continuation of the area of few magnetic anomalies in Marie Byrd Land to the west of the Sentinel Mountains shown by previous studies (Behrendt and Wold, 1963). The anomalies increase in amplitude over the Antarctic Peninsula; east of Eights Station several anomalies exceed 1000 y. The data from Flight 701 clearly show the numerous anomalies of the Antarctic Peninsula.

Approximate depths to the sources of 54 of the APT magnetic anomalies were calculated using the Peters (1949) half slope method. Behrendt and Wold (1963) have discussed the limitations of a method such as this when used with profile data. Single anomalies are not very reliable bases for deductions about the subglacial geology, but patterns revealed by examination of groups of anomalies may yield useful information. Depths calculated to the sources of the anomalies were compared with the depths to rock obtained from the seismic and gravity data. Previously we inter- polated depths to the base of the ice from bedrock elevation contour maps for use with the aeromagnetic data (Behrendt and Wold, 1963). In the present case a more or less continuous profile of bedrock elevation was available within the errors imposed by the gravity method. Consequently in the following discussion of magnetic depths, only the APT data were compared.

A method, such as the one used here, based on the assumption of narrow, infinitely deep, two dimensional bodies with vertical sides will, in general, give maximum depths to sources of anomalies. Since minimum depths are known from the ice thickness data, depths to "magnetic basement" can be bracketed. Seventy-eight percent of these anomalies had sources shallower than 1 km below the bedrock surface; 57% had sources shallower than 0.5 km. The only anomaly (at station 163), used for a depth calculation I I

1000T

4[AAAA NUNATAKS 500t MMONTAINS OL

100 i

Fig. 24. Residual aeromagnetic profiles. All total magnetic intensity except EHT which is vertical intensity. Continuous data except EHT which has 6 km intervals.

- - - - - m - m - - - -m - I = -4- .0150 ,906

*988 445 0 1021

.0100- -Q21

.0050 - ..

x • X X xl o Xx i

0 " I -5 • -6 -4 -3 -2 -I 0 +1 A D (KM)

Fig. 25. Apparent magnetic susceptibility contrasts vs. difference in bedrock elevation and calculated elevation of anomaly source. X indicates anomalies west of Station 112; triangle anomaly near Station 163; dots indicate anomalies east of Station 224.

1000--W E

1000- -NW SE IW

IL MODEL MODEL A69 A69 K= .004 cgs K=.004 cgs 500-- 500+ (~5 K LL

p..o .1 000

a00100 008•o° r 0 / 0- _0 976 - 1028 IE 008 ,ICE r 4- 1 - -717 ?1-

I i I I I l I I I I I -1 FPrl111 I I -2 00 I 10I 20I 30 KM -2 o 10 20 30 KM

Figs. 26 and 27. Models fitted to residual total magnetic intensity between Stations 976 and 1008 and between Stations 1008 and 1028. The observed profiles are indicated by dots. Flags indicate reflection soundings of ice thickness. Bedrock elevations at 6-km interval intermediate points from free-air anomalies. -44-

within the central area of few anomalies, gave a depth close to the base of the ice. The calculated depths were divided into two groups: those in the Jones Mountains area and those in the area of the Antarctic Pen- insula (Fig. 25). In the first group 100% were shallower than I km below the ice rock interfaces and 52% were shallower than 0.5 km. Within the Antarctic Peninsula area, east of station 224, there was a larger scatter; 76% were shallower than I km and 52% were shallower than 0.5 km below the ice-rock interface.

Vacquier, et al. (1951) gave the following equation for calculating the susceptibility for anomaly producing bodies assuming induction by the earth's f ield.

AF\F K VF F c where: K = susceptibility, cgs units

AF = amplitude of anomaly,

F = total field, T

AF is a dimensionless constant which is a function c of the assumed model amplitude.

Within the APT area (Fig. 24) from west to east the inclination varies from 68' to 66'S (Wasilewski, 1963) and the total field varies from 55,300 ( to 50,000 y with a declination of 33°E at Eights (Wasilewski, 1963). Apparent susceptibilities (-\Ka) were calculated for all anomalies used in the depth determinations assuming AFc = 1.5 from models A 50, 53, 64, and 67 (all narrow vertical sided bodies at various orientations with 600 and 750 inclinations of the total field) of Vacquier, et al. (1951). These results are shown in Figure 25, a plot of -AKa vs AD, the difference between the depths to bedrock and anomaly source. The apparent susceptibilities range from 0.0006 to 0.0147 cgs, and the depth differences range from +.17 to -6.05 km. This graph illustrates several points. The con- centration of most depths within I km of the ice-rock interface is obvious. The points indicating sources within the ice are an indication of the combined errors of the method and of the bedrock elevation. An apparent trend towards higher susceptibilities for deeper sources is indicated. While some systematic increase in susceptibility with increasing depth might beI possible, an order of magnitude within 5 km or less is hardly likely, particularly since the anomaly is produced by the susceptibility contrast relative to the surrounding rock. Rather, I believe that this graph shows the departures of some anomalies from the geometric assumptions of thin vertical sided models used to calculate both depths and susceptibilities and can be used as a warning against such errors. The anomalies giving the highest apparent susceptibilities are those about 1000 y amplitude inI Figure 24.

Attempts were made to fit more realistic models to some of the apparently deep high susceptibility examples of Figure 25. Figures 26 and 27 -45-

show reasonable approximations to the two anomalies centering about stations 988 and 1021. A similar model would fit the anomaly at station 445 (Fig. 6). The susceptibilities corresponding to these wider models are .004 cgs and AD is shallower in each case. The existence of these three similar anomalies in the same area (see Figs. 5, 6, and 24) suggests a relationship which is being investigated further by aeromagnetic flights. The narrow high susceptibility anomaly at station 906 (Figs. 7 and 25) has Aka =0.014 cgs and zD = 0, indicating that its susceptibility is probably actually greater than the bulk of the anomalies.

The scatter in ,D of Figure 25 for values within 2 km of the ice-rock contact may be real variations in depth or may be errors resulting from nonperpendicular crossings of the bodies or departures from the geometry assumed. (A 45' crossing of a linear body would result in only a 29% increase in calculated depth.) In spite of these limitations it can be seen that "magnetic basement" is not very far beneath the ice in the Jones Moun- tains and Antarctic Peninsula areas. Throughout the preceding discussion, the term "magnetic basement" has been used to indicate the surface at some depth beneath the ice at which the majority of anomalies have their origin.

Behrendt and Wold (1963) observed an area of few magnetic anomalies extending westward from the Sentinel Range about half the distance to Byrd (80OS, 120OW). They suggested that it was the result of an extension of the thick metasedimentary section exposed in the Sentinel Range. Their data included several flights in the Ellsworth Mountain area which showed few or no anomalies although no actual traverses across the 5000 m high Sentinel Range were flown. The present data (Fig. 24) show a continuation of this terrane north to the track of the APT. Seismic refraction measurements in the vicinity of the Sentinel Range showed about 1.3 km of 5.2 km/sec rock above 6.1 km/sec rock (Bentley and Ostenso, 1961). This was interpreted as a metasedimentary rock by Behrendt and Wold (1963), in consideration of the lack of magnetic anomalies and the observed quartzite in the adjacent mountains (Anderson, et al., 1962).

Depths were calculated from 5 anomalies on the southern segment of Flight I (Fig. 24). The 250 C anomaly at 91'W gave a depth of 5 km below sea level (Behrendt and Wold, 1963). The other depths were calculated from a downward continuation of the field using Henderson's (1960) method. The depths were -4.2, -4.4, -4.1, and -4.2 relative to sea level from west to east for the easternmost anomalies on the southern segment of Flight 1. Their apparent susceptibilities average about 0.002 cgs, which is not indicative of the type of error discussed above for apparently deep anomalies. Admittedly these depths are open to greater uncertainty than the shallow sources to the east and west discussed previously, but they do give some indication of the possible thickness of sedimentary rock in this area. Comparison of these depths with the bedrock elevation map (Fig. 8) gives 3-4 km for a possible thickness of the sedimentary section in this area. If these scattered anomalies are caused by intrusive bodies within the sedimentary section its thickness would be greater still.

The anomalies associated with the Antarctic Peninsula shown on Flight 701 in Figure 24 do not continue south of the segment shown where the flight line crosses the Filchner Ice Shelf. The gradients of the anomalies -46-

on this segment are steepest over the region covered by the APT and appear to decrease southward towards the Filchner Ice Shelf. Eight depth determinations, along 70'W, show sources which are shallow in the APT area and which progressively deepen to the south: 73'25'S, 0.8 km elevation of source relative to sea level; 74'45'S, 0.8 km; 74'58'S, 1.5 km; 75003'S, 1.5 km; 750 57'S, -0.3 km; 76050'S, -3.8 km; 770 15'S, -3.4 km; 770 34'S3 -5.5 km. It seems likely that the basement deepens to the south; the thick metasedimentary section of the Sentinel Range possibly continues to the east beneath the Filchner Ice Shelf.

Two depths given by Behrendt and Wold (1963) are located within the postulated area of sedimentary rock. These occur on the part of Flight 1 about 74'20'S between 870 and 89'W (Fig. 9), and are within 0.5 km of the base of the ice. The anomaly at APT station 163 in this vicinity also gave a shallow depth, as mentioned previously (see Fig. 25). These shallow depths could be indicative of basic intrusive bodies within the sedimentary rock such as observed to the south by Craddock, Anderson, and Webers (1963) or volcanic rocks similar to the Jones Mountains to the west.

We will turn now to the shallow "magnetic basement" observed in the area of the Antarctic Peninsula. Table 3 shows the various extrusive and metasedimentary rocks collected at outcrops throughout the area. The magnetic anomalies probably have their sources in the dacite and andesite which contain magnetite (Laudon et al., 1964). No susceptibility measurements for the rocks collected are available. The steep dips, which were observed at outcrops, probably extend throughout the ice-covered areas, as indicated by the general structure of the mountains and the shallow depths to the sources of the magnetic anomalies, as the depths were calculated assuming narrow vertical sided bodies.

Although the rocks in the Ellsworth Mountains and the mountains of the southern Antarctic Peninsula are steeply folded, other considerations suggest that these areas are not geologically continuous. The general structural trends are at approximately right angles, which suggests a different age for the folding, although the trend could curve sharply to contain both areas. The area of sub sea level bedrock shown on the subglacial topography map (Fig. 8) separates the two areas. The sedimentary section of the Ellsworth Mountains is Paleozoic as far as is known, whereas only Mesozoic rocks have been definitely dated from the southernI Antarctic Peninsula. The area of the Ellsworth Mountains is characterized by a magnetic field showing infrequent anomalies with mostly deep sources whereas the Antarctic Peninsula has many high amplitude anomalies causedI predominantly by shallow extrusive rocks. The area of few magnetic anomalies associated with the Ellsworth Mountains appears to trend to the west of the Antarctic Peninsula, separating it from the volcanic JonesI Mountains and Marie Byrd Land. In combination these differences, no one of which is conclusive in itself, do indicate that the Ellsworth Moun- tains are not a simple continuation of the geology of the Antarctic Pen- insula as was suggested by Bentley et al. (1960). -47-

During a portion of the traverse the U. S. Coast and Geodetic Survey operated horizontal and vertical intensity magnetographs at Eights Station. From these data the author computed total intensity diurnal variation curves which were compared with the diurnal curves measured in the field as shown in Figures 28-32. The standard deviation between the two sets of data is ±15 y for the 20 days studied. The standard deviation for each day between the station and field data was examined as a function of radial distance from Eights Station, as shown in Figure 33, but no correlation was observable.

The average amplitude of the anomalies crossed during a day's travel was computed and compared with the standard deviation of the diurnal curve for that day from the diurnal curve at Eights Station. Eighteen days showed a good correlation through a range of mean anomaly amplitudes from 30-600 y. The standard deviation of the daily standard deviations from the least square line fitted through these data is ±2.8 y. The low standard deviations were observed over the area of hypothesized metasedimentary rock and the high values over the extrusives of the Antarctic Peninsula.

The two points corresponding to A 950 y shown in Figure 34 do not fit the line and were omitted in the least square fit. On each of these days, only one anomaly was crossed one of which is shown in Figure 26. The char- acters of both of these anomalies are similar and as discussed previously could not be easily accounted for by thin dike models as could the bulk of the anomalies. The model of Figure 26 showed that the amplitudes of these anomalies were not indicative of the susceptibilities of their sources using the simple assumptions. The similar anomaly of Figure 27 was averaged with several others in computing the points of Figure 34 and does not appear to depart from the general scatter of the data. Eights Station was not established at the time the field party was in the Jones Mountains area so no comparisons with these anomalies are possible.

The susceptibilities shown in Figure 25 were compared with respect to the southern Antarctic Peninsula and Jones Mountains areas. The Jones Mountains anomalies with sources within I km of the base of the ice have a mean AKa = 0.0015 ±.0007 cgs compared with the Antarctic Peninsula AKa = 0.0036 J.0018 cgs. These values might suggest a difference in the amount of magnetic material in the shallow anomaly-producing rock bodies between these two areas.

An alternative explanation of the difference in average apparent susceptibility lies in the geometry of the anomaly-producing bodies. The apparent susceptibility was calculated assuming infinite thickness of the source bodies. The steeply dipping extrusives of the southern Antarctic Peninsula fit this assumption more closely than the volcanics of the Jones Mountains, which are about 500 m thick on a flat granitic complex (Craddock, Bastien and Rutford, 1963). Calculations were made using the equations of Heirtzler et al.,(1962) assuming the mean apparent susceptibility of 0.0036 cgs obtained over the southern Antarctic Peninsula and the average ice thickness of 0.5 km (see Figure 4) in the Jones Mountains area. A theoretical -48-

body about 3 km wide would produce the average observed anomaly in this area of 125 T. Thus the conclusion is reached that a significant difference in average susceptibility of the source rock is not required by the significantly higher anomaly amplitudes in the area east of station 224 compared with the Jones Mountains area.

On the basis of these arguments I believe that the suggested geologic continuity (Craddock, Bastien, and Rutford, 1963) of the Antarctic Penin- sula orogenic belt into the Jones Mountains area is not denied because of the higher amplitude magnetic anomalies of the southern Antarctic Peninsula. The break in the continuity of anomalies between these two areas and the absence of sedimentary rock does require further explanation before a continuation of the Andean structure of the Antarctic Peninsula into Marie Byrd Land can be completely accepted.

The geology in the southern Antarctic Peninsula does appear to be reasonably continuous with that known farther north throughout its 1800 km length. Apparently a marine mobile belt was continuous through this distance during the Cretaceous (Halpern, 1963; Laudon et al., 1964; Craddock, Bastien, and Rutford. 1963). Possibly this mobile belt as suggested by Adie was existent in the southern area of the Antarctic Peninsula during part of the Paleozoic but none of the rocks collected in the area covered by the APT furnished any evidence for this. Probably the Tertiary volcanics in the Jones Mountains are related to the more or less contemporaneous volcanic activity in the northern Antarctic Peninsula and South Shetland Islands as suggested by Adie (1962); all of these lie on the seaward side of the Cretaceous mobile belt. Griffiths (1963) reported high amplitude magnetic anomalies at the northern extremity of the peninsula and in the Scotia Arc area; these are probably of similar origin to the anomalies discussed here. The "magnetic basement" at or near the base of the ice in the Jones Mountains area is continuous with that of northern Marie Byrd Land, which was also shown to be shallow (Behrendt and Wold, 1963).

I I I m m - mm m m m m m - - - - - I m

A PT AND EIGHTS STATION DAILY TOTAL INTENSITY VARI \TION

DECEMBER 8 ,1961 DECEMBER t0 +40 4- (f) Qr) 0

-40 -40

LOCAL TIME LOCAL TIME

DECEMBER 12 DECEMBER 15 +40 +4

o (0

-40 -40 1000 1500 1000 1500 -- 2000 0100 LOCAL TIME LOCAL TIM E

0 LEAD INSTRUMENT 0 FOLLOWING

% -" EIGHTS Fig. 28. APT AND EIGHTS STATION DAILY TOTAL INTENSITY VARIATION

DECEMBER 17,1961 DECEMBER 18 +40- +4

0 0 - (10 S0- -0

0 LEAD INSTRUMENT -40- I I 40 1 0 FOLLOWING 1500 2000 0100 e.0 . EIGHTS 0500 LOCAL TIME LOCAL TIME

DECEMBER 23 DECEMBER 26 +40 +

(Jo 0 (r +40

-40 0 IT5

-40k 0500 1000 1500 0100 0600 11.00 1600 LOCAL TIME LOCAL TIME

Fig. 29

m - m m m mmmm m m mm - m m -- I = APT AND EIGHTS STATION DAILY TOTAL INTENSITY VAPIA TION

DECEMBER 27, 1961 JANUARY 3 AND 4,1962 +4 +40 (.o! 0 0 0 0

-40 1000 1500 2000 1000 1500 2000 LOCAL TIME LOCAL TIME

0 LEAD INSTRUMENT

0 FOLLOWING WI -E IG H T S JANUARY 7 JANUARY 9 +40 +40

-40 ,-40 1000 1500 2000 LOCAL TIME -80

1200 700 LOCAL TIME Fig. 30. A PT AND EIGHTS STATION DAILY TOTAL INTENSITY VARIATION

JANUARY II JANUARY 13 + +40 Q)

-40

1000 1500 LOCAL TIME

LOCAL TI ME 0 LEAD INSTRUMENT

0 FOLLOWING YI %*ftaoo#E IGHTS

JANUARY 14 JANUARY 15 480

440

(1)

0 ,qzqS-40

-40 S-40 1000 1500 " 2000 LOCAL TIME 000 1500 2000 LOCAL TIME Fig. 31

- m - - m - m = m - m m m m -im I = m~m-mm mm - M m -ml

APT AND EIGHTS STATION DAILY TOTAL INTENSITY VARIATION

JANUARY 17 JANUARY 8 440 +40

0 ------'N --- - - 0 -4o-0--- - -...

-8o0ILI-80- I 10( O0 1500 000 1500 2000 2000 LOCAL TIME LOCAL TIME

FEBRUARY 2,1962 FEBRUARY 3

(f)

I (0 L.) I

LOCAL TIME

1000 1500 2000 FEBRUARY 4 LOCAL TIME FEBRUARY 5 AND 6

4-0 QJ) M.as - A^)

- C+UUi

1000 1500 -80 I I I LOCAL TIME 2 1000 1500 200 * LEAD INSTRUMENT LOCAL TIME o FOLLOWING -%dr~.'".,E IG H T S Fig. 32. I 30 f 4 4 -L I 251 I -l~ 20 --- 404-432 -0-908-940 0700-732 0 0 :1008-1052 668-700 LF 0976-1008 I

(.Ib 15 0432-464 496-528 * @528-538 256-288 I 352- 4040 0 10 18572-604 192-224 732-764 940-976 0 0288-, 320 0 :320-352 •0 o224-256 I 5 112-144

09 I

0 100 200 300 400 50C

DISTANCE FROM EIGHTS STATION (KM) N Fig. 33. Standard deviation of APT diurnal curves and simultaneous Eights Station diurnal curves vs. radial distance from Eights Station. I I 30 t -1------~ 4 + I I 908-940 700-732 20 2Os .668-700 C:) 404-432 1008-1052 976 -1008 I

15 432-464-

49-2 0528-538.5 I 940-976 10 I i2, _i 572--bO41 0352-404 ;11 572 604' ck 6 192-22401732-764 @3201-352 I 88to20 ~0604-636 224-F 256 5 2-1044 - 0 256-2d8 __ I 0 1111 0 100 200 300 400 500 600 700 800 900 1000 I

Fig. 34. Standard deviation of APT diurnal curves and simultaneous Eights I Station diurnal curves of total intensity vs. means of anomaly amplitudes traversed during these days. I -55-

LONG REFRACTION PROFILE

At station 796 the seismic refraction profile was extended to 18 km in order to measure the compressional-wave velocities in the underlying rock. Three charges of 50, 200, and 250 kg were fired at distances of 9, 13, and 18 km from the spread. The time of the shot was transmitted by radio. Distances were measured by Tellurometer and are accurate to ±4 m or better. Reflection measurements of ice thickness along the profile were made at eleven locations. Gravity readings were used to interpolate between the reflection stations, so that a nearly continuous profile of the ice thickness was available. Figure 35 is a travel-time curve of the refraction results. The arrivals have been corrected for elevation of the snow surface and for the topography of the bedrock surface using the Sutton and Bentley (1953) topographic correction curves.

The 5.3 km/sec layer was observed as a strong first arrival on each of the three records. The 4.4 km/sec layer was observed as second or third arrivals of good quality on each of the three records. The 6.0 km/sec arrival shown in the figure was observed only as a poor second arrival on the 18 km shot and is the least-squares fit of the cross-spread arrival times for the 700 m long line of geophones. The intersection of this line with the 4.4 km/sec arrival at 13 km is believed to be accidental, as no correction was made for possible topography on the surface separating the 5.3 and 6.0 km/sec layers. These later arrival velocities must be regarded with somewhat more caution than the 5.3 km/sec first arrivals. Figure 36 is the interpreted section along this refraction profile. Small flags indicate the locations at which reflection measurements of ice thickness were made. The double flags show the shot points of the three large charges. The other points along the profile show the gravity depth determinations which are discussed more fully in the next section. Sub-bottom vertical reflections were observed at all stations along the profile. These are interpreted as coming from the horizon separating the 4.4 and 5.3 km/sec layers. The thickness of this layer has been shown on the profile for an assumed velocity of 4. 4 km/sec in the material. Examination of the figure makes it obvious why the 4.4 km/sec arrival was not observed as a first arrival on any of the three large charges. Least-squares cross- spread velocities, of 4.3 and 5.5 km/sec were obtained which provide a pseudo-reversed profile. In this particular case no corrections for dip beneath the spread were made to the cross-spread velocities because the ice to rock interface and the 4.4 km/sec to 5.3 km/sec interface in the area of the emergent rays are horizontal, as determined from reflection measurements (Fig. 36). The ice thickness to which the topographic corrections were made was 0.92 km, as determined from reflection soundings. The ice thickness determined by the refraction method from the time distance curve was 0.82 kin, which is in fairly good agreement, considering the topography. The average thickness of the 4.4 km/sec layer as calculated from the reflection and refraction methods was 0.2 km. A thickness of about 31 km was determined for the 5.3 km/sec layer from the apparent 6.0 km/sec velocity. As a horizontal boundary was assumed, this thickness is only an approxima tion. 7

0 L

0 4 8 12 16 20 Fig. 35. Long refraction travel time graph for Station 796 (740 27'S, DISTANCE KM 67*08'W). Arrival times corrected for elevation and topography.

Sm m mm m m m m m m m I = -57-

The 4.4 km/sec layer directly beneath the ice could be frozen moraine or a thin layer of sedimentary rock. Cretaceous sandstones, black shales, arkose, conglomerate, argillite, dacite, and andesite were collected at several outcrops on the traverse (Laudon et al., 1963). Dr. Murli Manghnani is making ultrasonic velocity measurements on some of these samples and has kindly furnished the author with some preliminary results (see Table 3). For an andesite sample from 11M, Vp = 5.2 km/sec; for a dacite from Mt. Rex, V= 5.6 km/sec; for a metamorphosed graywacke from Shimizu Nunatak, Vp = 5.85 km/sec; and for a black shale from P3M, Vp = 5.51 km/sec. Since these values are all similar to the 5.3 km/sec measured by the refraction method, we cannot determine whether this velocity represents an extrusive or meta- sediment, but it is probably from one or the other of these rock types.

The 6 km/sec arrival, if real, is a typical velocity of the upper crust for other parts of Antarctica (Woollard, 1962) which has been previously interpreted as granitic rock by Bentley and Ostenso (1961). At one profile location in West Antarctica, to the east of Byrd Station, they measured about 1.3 km of 5.2 km/sec rock above a 6.1 km/sec rock. In the area of the Sentinel Mountains they measured a 5.3 km/sec layer about 1.3 km thick above 6.3 km/sec rock. The 31 km of 5.3 km/sec rock measured here is significantly thicker than that measured anywhere else in West Antarctica. -583

N S

QZ S+120---4zo,O

-00"- 0 Lki

t±50T 4I

--4 00 weswo. "m-..o .. --- + ....- _

:::::bSIMPL -00

+3-

k + 2-- " "_ p44(tO2 2.7T .

_ _ E_ __IC _ _ _ _ qAL

0-. 52 I

RC l v i ad gt

files between Stations 796 at left and 808 at right. The theoretical free-air anomaly curve was computed from the model shown. I Flags indicate reflection soundings of ice thickness. Dots and dashes on topography profile indicate gravity determinations and sub-bottom reflections, respectively. 3 I -59-

GRAVITY ANOMALIES

Terrain effect. The limitations on the use of gravity data due to the effects of buried topography were mentioned in an earlier section; Figure 36 illustrates this point. The reflections along the 18 km refraction profile provided a quite detailed picture of the rock topography. Gravity observations were made at 18 locations along the profile. The bottom profile shown was constructed using the empirically determined constant of 20 m/mgal from comparisons of differences in free-air anomaly vs. differences in bedrock elevation for all Antarctic traverses (Bentley, 1964) and closing the errors at adjacent reflection stations for free air anomalies not at reflection stations.

It was stated above that the 4.4 km/sec layer could be either frozen moraine or sedimentary rock. Since detailed bottom topography was available for this profile an attempt was made to determine which of these pos- sibilities was the more likely. Theoretical terrain and Bouguer corrections (complete Bouguer corrections) were calculated using the line integral method of Talwani et al. (1959) for an assumed two dimensional structure as shown in Figure 36 using densities of P2 and P3 = 2.7 g/cm 3 . The regional slope is -11.7 mgal to the south along the 18 km profile. This was obtained from the least squares fit of a straight line to the complete Bouguer anomalies. The standard deviation of the complete Bouguer anoma- 3 lies from this line is ±3.4 mgal. A density of p2 = 2.0 g/cm gave a similar result with a standard deviation of ±3.7 imgal, showing that it is not possible to determine which of these two densities best fits the 4.4 km/sec layer even with the detailed seismic reflection control.

The simple Bouguer anomalies (without the terrain corrections) calculated from the gravity data at the reflection stations along the profile are shown in Figure 36, together with the complete Bouguer anomalies. The average of the simple Bouguer anomalies along the profile is -63 mgal, with a standard deviation from the regional slope of ±15 mgal. The average of the complete Bouguer anomaly is -61 mgal. The terrain correction ranged from +20 to -19 mgal, averaged +2 mgal and had a standard deviation of ±15 mgal. The regional trend is hardly observable over this profile from the simple Bouguer anomaly values alone. It is in agreement with the expected isostatic compensation, as discussed below.

A theoretical free-air anomaly curve is shown in Figure 36 with the observed free-air anomalies. This curve was obtained by adding the average complete Bouguer anomaly (-61 mgal) to the absolute value of the complete Bouguer correction for each point and adjusting for the regional slope. The standard deviation of the observed free air anomalies from the theoretical curve is ±3.6 mgal. This corresponds to an uncertainty in the bedrock elevation in the order of 80 m instead of : 300 m as gen- erally obtained using the infinite slab hypothesis (Bentley, 1964).

The topography shown in Figure 36 has relief of the order of the ice thickness (about 1 kin) and a "wavelength" about 2-4 times the ice thickness. The data spacing is about equal to the ice thickness. The topography in -60-

the third dimension was ignored in the line integral calculation but apparently does not have a large effect, implying that the topographic "wavelength" away from the profile is approximately equal to or greater than that along the profile. These calculations show that it is possible to obtain fairly accurate determinations of bedrock elevation beneath a glacier from free-air anomalies by the line integral method. The main require- ment for this is closely spaced gravity stations so that an essentially continuous curve could be drawn through them. Of course seismic reflection stations spaced closely enough to determine the regional gravity gradient would still be required for control.

This profile has been discussed at some length, not because of the importance of a relatively obscure 18 km section extending to a depth of only 41 km below the surface, but because it illustrates the difficulties and dangers inherent in basing a geophysical interpretation in a glacier- ized area solely upon one type of data.

Crustal structure. Figure 37 is a free-air anomaly map of the area. C. R. Bentley supplied the EHT gravity data used in this figure and in Figure 38. In Ellsworth Land west of Eights Station the average free air anomaly is +11 mgal, indicating that the area is probably in isostatic equilibrium within the limits of error. The relatively narrow high area of the Antarctic Peninsula east of Eights Station has an average free-air anomaly of +60 ±30 mgal which is illustrative of the rough subglacial topography and suggests that the peninsula is not entirely locally compensated. Figure 38 is the Bouguer anomaly map. Terrain corrections have not been made, and a certain amount of smoothing was necessary in drawing the con- tours of the two gravity maps. The average Bouguer anomaly in Ellsworth Land is +22 mgal. A crustal model was assumed based on Woollard's (1962) mean sea level crustal column for all continents of 31.7 km obtained from averaging all available crustal refraction determinations. If the average crustal and mantle densities are 2.86 and 3.31 g/cm 3 , respectively, (Woollard, 1962) a crust with its base 31 km below sea level will produce the observed +22 mgal Bouguer anomaly. This depth is reasonable for a continental marginal area such as this and is in general agreement with the results of crustal thickness estimated from gravity and surface wave dispersion to the south and west in Marie Byrd Land (Bentley, et al., 1960; and Kovach and Press, 1961). For the area of the Antarctic Peninsula east of Eights_Station modelsI were constructed again using the line integral method (Talwani et al., 1959) for calculating the gravitational effect of two dimensional bodies. Bou- guer anomalies to the east and west were projected to the profile A-' inI Figure 38. Figure 39 shows the results of these calculations. The elevation for the surface shown in the profile is corrected for the density dif- ferential of ice (0.9 g/cm3 ) and rock (2.7 g/cm3 ) used in the Bouguer reduction. Two regionally compensated models are shown in this figure con-I structed by assuming 120 and 160 km radii of compensation. All surface elevations, projected to the profile, were averaged over these intervals; Archimedes principle was assumed with the density relationship shown, and the same standard sea level crustal column of 31.7 km was used as in Ells- worth Land. The Bouguer anomalies calculated from these two models are - - -- - m m m -mI =m

Fig. 37. !

BOUGUER ANOMALY CONTOUR INTERVAL 20 MGAL rELLSWORTH HIGHLAND TRAVERSE 1960-1961 /' A - - ANTARCTIC PENINSULA TRAVERSE 1961-1962 MOUNTAINS MUTIS0 1/ 50 100 KM AA AAA~A NUNATAKS SCALE 0a 50I IOO.Kj

Fig. 38.

- - -m m- m -ml- I-- -63-

shown, together with the actual Bouguer anomalies projected to the profile. Considering the scatter in observed Bouguer anomalies due to topography, local density variations, and the projection, the use of a more detailed crustal model was not considered justified. It is concluded that this part of the Antarctic Peninsula is regionally compensated.

The models of Figure 39 indicate that the crust is several kilometers thicker beneath the Antarctic Peninsula than in Ellsworth Land. Steinhart and Meyer (1961), Woollard (1962) and Pakiser (1963) have shown that isostatic compensation is not achieved solely by crustal thickening but may also result from variations in crustal or mantle densities. Pakiser (1963) showed that compensation within the Basin and Range province of the United States is the result of crustal thickness variations but in crossing the boundary into another geologic province the compensation is partially a- chieved by variations in the thickness of an intermediate layer. Similar situations no doubt occur throughout many areas of the earth. Since it appears possible from the previous discussion of the magnetic data that the Antarctic Peninsula is not within the same geologic province as Ells- worth Land, it would be naive to accept crustal thickening as the only possible explanation of its more negative Bouguer anomaly. Other models could be constructed to account for the Bouguer anomalies of Figures 38 an,' 39, but without any refraction determinations of deep crustal or upper mantle compressional wave velocities anywhere on the continent, such attempts do not appear justified. In any case the crustal structure and/or upper mantle beneath the Antarctic Peninsula is somewhat different from that of Ellsworth Land. -64-

+ 0

-50

10 0R

-2

LAPC Q=2.86 gm./cm

0 50 R001KM I I I

Fig. 39. Isostatically compensated crustal Profile models along A-A' of Fig. 38, for 120 and 160 km radii I of compensation and their associated theoretical Bouguer anomaly curves. Observed data shown as points. I I I I -65-

ACKNOWLEDGEMENTS

I would like to thank the other traverse party members: Perry E. Parks, Jr. and Lee W. Kreiling, University of Wisconsin; Hiromu Shimizu, Hokkaido University, Japan; John R. T. Molholm, Ohio State University; Conrad G. Merrick, U. S. Geological Survey; and Peter J. Wasilewski, U. S. Coast and Geodetic Survey, for their assistance in making the geophysical observations. Merrick determined positions of the major stations and peaks. C. R. Bentley made available unpublished gravity and magnetic data from the Ellsworth Highland Traverse. The U. S. Coast and Geodetic Survey provided Eights Station magnetograms. The U. S. Naval Oceanographic Office furnished magnetograms from a Project Magnet survey flight. The CDC 1004 computer of the University of Wisconsin Numerical Analysis Laboratory was used for the line integral computations. A grant from the National Science Foundation supported field work and data analysis. Air Development Squadron 6 (VX6), U. S. Navy effi- ciently provided the vast amount of logistic support required to conduct field operations in this inaccessible area of Antarctica. This consisted of 57,000 km of Hercules, C130 flights and 21,000 km of Dakota, C47 flights for support of the 1700 km traverse. Finally, I wish to thank my colleagues for their many helpful criticisms and suggestions in the course of the work represented by this report.

-67-

REFERENCES

Adie, R. J., The geology of Antarctica, Antarctic Research, Geophysical Monograph No. 7, American Geophysical Union, Washington, D. C., 1962.

Adie, R. J., The basement complex of Neny Fjord, Graham Land, British Antarctic Surv. Rept. 43, 49 pp, 1963.

Anderson, J. J., T. W. Bastien, P. G. Schmidt, J. F. Splettstoesser, and C. Craddock, Antarctica; Geology of the Ellsworth Mountains, Science, 138, 824-825, 1962.

Bader, Henri, The theory of densification of snow on high polar glaciers, II, Research Report 108, U. S. Army C.R.R.E.L., Hanover, N.H., 1962.

Behrendt, J. C., A statistical comparison of five geodetic gravimeters, Geophys. 27, 889-891, 1962.

Behrendt, J. C., Seismic measurements on the Ice Sheet of the Antarctic Peninsula, J. Geophys. Res., 68, 5973-5990, 1963.

Behrendt, J. C., Crustal geology of Ellsworth Land and the southern Antarctic Peninsula from gravity and magnetic anomalies, J. Geophys. Res., in press, 1964.

Behrendt, J. C., R. J. Wold, and T. S. Laudon, Gravity base stations in Antarctica, Geophys. J., 6, 400-405, 1962.

Behrendt, J. C., and R. J. Wold, Depth to magnetic basement in West Antarctica, J. Geophys. Res., 68, 1145-1153, 1963.

Bentley, C. R., Glacial and subglacial geography of Antarctica, Antarctic Research, Geophysical Monograph 7, American Geophysical Union, Wash- ington, D. C., 1962.

Bentley, C. R., Structure of Antarctica and its ice cover, Proceedings of the Los Angeles 1963 IGY Symposium, in press.

Bentley, C. R., A. P. Crary, N. A. Ostenso, and E. C. Thiel, Structure of West Antarctica, Science 131, 131-136, 1960.

Bentley, C. R., and N. A. Ostenso, Glacial and subglacial topography of West Antarctica, J. Glaciol. 3, 882-911, 1961.

Craddock, C., J. J. Anderson and G. F. Webers, Geological outline of the Ellsworth Mountains, paper presented at Symposium on Antarctic Geol- ogy Capetown, 1963. -68-

Craddock, C., T. W. Bastien, and R. H. Rutford, Geology of the Jones Moun- tains area, paper presented at Symposium on Antarctic Geology, Cape- town, 1963.

Doumani, G. A. and E. G. Ehlers, Petrography of rocks from mountains in Marie Byrd Land, West Antarctica, Bull. Geol. Soc.Am., 877-882, 1962.

Gow, A. J., Results of measurements in the 309 meter bore hole at Byrd Station, Antarctica, J. Glaciol. 4, 771-784, 1963.

Griffiths, D. H., Geophysical investigations in the Scotia Arc, paper presented at Symposium on Antarctic Geology, Capetown, 1963.

Halpern, M., Cretaceous sedimentation in Base O'Higgins area of northwest Antarctic Peninsula, Ph.D. Thesis, University of Wisconsin, 1963.

Henderson, R. G., A comprehensive system of automatic computation and its applications, Geophysics, 25, 569-585, 1960.

Heirtzler, J. R., G. Peter, M. Talwani and E. G. Zurflueh, Magnetic anomalies caused by two-dimensional structure: Their computation by dig- ital computers and their interpretation, Lamont Geological Observa- tory, Technical Report No. 6, 1962.

Kovach, R. L., and F. Press, Surface wave dispersion and crustal structure in Antarctica and the surrounding oceans, Annali di Geofisica, 14, 213-224, 1961.

Landauer, J. K., Creep of snow under combined stress, Research Report 41, U. S. Army S.I.P.R.E., Wilmette, Ill., 1957. I

Laudon, T. S., J. C. Behrendt and N. J. Christensen, Petrography of rocks collected on the Antarctic Peninsula Traverse, J. Sediment. Petrol., in press.

Pakiser, L. C., Structure of the crust and upper mantle in the western 3 United States, J. Geophys. Res., 68, 5747-5756, 1963. Peters, L. J., The direct approach to magnetic interpretation and its application, Geophysics, 14, 290-320, 1949.

Rigsby, G. P., Crystal orientation in glacier and experimentally deformed ice, J. Glaciol., 3, 589-606, 1960.i

Robin, G. de Q., Ice movement and temperature distribution in glaciers and ice sheets, J. Glaciol., 2, 523-532, 1955. I

Robin, G. de Q., Glaciology 3, Seismic Shooting and Related Investigations, Norsk Polar Institutt, Oslo, 1958.

Slichter, L. B., The theory of the interpretation of seismic travel-time curves in horizontal structures, Physics, 3, 273-295, 1932. 3 I -69-

Steinhart, J. S., and R. P. Meyer, Explosion studies of continental structure, Carnegie Inst. Wash. Publ., 622, 409 pp., 1961.

Sutton, G. H., and C. R. Bentley, Topographic correction curves, Tech. Rept. 3, Lamont Geological Observatory, Palisades, N. Y., 1953.

Sutton, G. H., H. Berkhemer, and J. E. Nafe, Physical analysis of deep sea sediments, Geophyscis, 22, 779-812, 1957.

Talwani, M., J. L. Worzel, and M. Landisman, Rapid gravity computations for two-dimensional bodies with application to the Mendocino Submar- ine Fracture zone, J. Geophys. Res., 64, 49-59, 1959.

Thiel, E., and N. A. Ostenso, Seismic studies on Antarctic ice shelves, Geophysics, 26, 706-715, 1961.

Vacquier, V., N. C. Steenland, R. G. Henderson, and I. Zietz, Interpreta- tion of Aeromagnetic Maps, Geol. Soc. of Amer. Memoir, 47, New York,

Wasilewski, P. J., Magnetic results Antarctic Peninsula Traverse, U. S. Coast and Geod. Survey, Washington, D. C., 13 pp., 1963.

Weertman, J., Mechanism for the formation of inner moraines found near the edge of cold ice caps and ice sheets, J. Glaciol., 3, 765-978, 1961.

Wood, A. B., A Textbook of Sound, G. Bell and Sons, London, 1941.

Woollard, G. P., Crustal structure in Antarctica, Antarctic Research, Geophysical Monograph 7, American Geophysical Union, Washington, D. C., 1962.

Woollard, G. P., The relation of gravity anomalies to surface elevation, crustal structure, and geology, Geophysical and Polar Res. Cent. Report 62-9, University of Wisconsin, 1963.

Yevteyev, S., Determination of the amount of morainal material carried by glaciers of the East Antarctic coast, Info. Bull. of the Soviet Antarctic Expedition, 11, 1959.

-71-

APPENDIX I

TABULATED DATA I

TABLE A GENERAL DATA SUMMARY I

Total Bed Rock Ice Observed Free Air Bouguer Magnetic Elevation Thickness Gravity Anomaly Anomaly Intensity Station Latitude Longitude Elevation + I mgal +15mgal +13 mgal + 25 ' + 1' + 4' + 50 m +70 or +300m +20 or +300m 94025'W 19.0 3.9 55285 Camp Minn., EHT 1215 1 0* 73029'S ' 558 - 80 640 982.6483 4 73027' 94020 750 .6537 11.8 55155 ' ' 512 -240 8 73025 94013 421 50 470 .6901 21.8 55170 ' 94002' 460 .6613 29.0 55185 12 73024 ' 535 80 ' 93052 640 .6636 18.0 55095 16 73024 492 -150 ' ' 93040 150 .6631 48.4 55245 20 73024 ' 592 440 ' 93029 .6134 33.9 55020 I 570 24 73024 ' 706 140 ' 93022 700 .5754 34.9 54955 28 73026 ' 838 140 ' 93018 909 130 780 .5559 34.9 55002 32 73029 ' 93013 .5360 32.3 55045 36 73032' 973 70 900 ' ' 93009 920 .5253 34.4 54980 40* 73034' 1020 100 44 73036 92058' 1041 - 40 1080 .5142 28.2 54780 ' ' I .5482 48.5 54755 48 73038 92047 1002 350 650 ' 49.9 54670 52 730401 92039 972 360 610 .5605 ' 51.5 54660 56 73041' 92028 936 380 560 .5741

92017' 931 200 730 .5679 42.7 54765 60 730421' ' 92006 908 -340 1250 .5495 16.7 64 73043' 91056' 909 - 40 950 .5656 32. 3 68 73044' ' I 32.2 72 73045 91045' 947 - 60 1010 .5546 ' 91035 39.2 76 73047 998 70 930 .5474 ' ' 80 73048 91025' 1039 50 990 .5352 38.7 ' 91015 .5436 55.7 84 73050 1072 380 690 91004' .5330 62.5 88 73051' ' 1131 500 630 ' 90°53 53.0 92 73052 ' 1208 290 920 .5005 I ' 90043 43.5 96 73053 1238 90 1150 .4836 ' ' 23.6 100 73054 90032 ' 1235 -320 1560 .4654 ' 90021 1229 -490 1720 .4591 15.7 104 73055' 108 73056 90 11' 1200 -550 1750 .4666 13.4 ' 90001 54300 112 73058 1194 -520 1710 .4722 15.6 ' 2.3 54345 EHT 1116 115.6* 73959' 89058 1214 -240 1450 .4816 30.3 I ' ' 1245 54315 120** 74001 89045 ' ' 1227 54290 124 74002 89035 ' 1191 54245 128 74003' 89023' 89011 1155 54210 132 74'04' ' 136 74005' 88000 1131 54185 I ' ' 140 74006 88048 1113 54140 1115 .4937 5.5 54120 144 74007' 88038'' 88027 1125 53955 148 74007'' ' 152 74008 88015 1160 54050 ' ' 54010 156 74009 88004 1156 ' ' 53970 160 74009 87052 1141 I ' ' 164 74010 87041 1162 53970 ' ' 87029 1217 53975 168 74011 ' ' 1228 53995 172 74012' 87017 ' 176 74012 87006 1249 53960 ' ' 1245 53920 180 74013' 86055 ' 184 74014 86043 1242 53895 I ' ' 1260 53825 188 74014' 86032 1250 .5089 56.0 53770 192 74015' 86021'' 196 74014 86009 1245 53720 ' ' 200 74015 1229 53695 ' 85057 ' 1220 53670 204 74016' 85045 ' 1189 - 90 1280 .5154 50.8 12.8 53645 EHT 1044 I 208 74016' 85034 ' 1164 80 1080 .5371 57.7 53635 212 74015' 85022' 216 74015 85010 1133 160 970 .5494 60.4 53630

' 220 74015' 1091 30 1060 .5545 52.6 53610 ' 84058 ' 1055 - 20 1080 .5608 48.6 10.3 53560 224* 74014' 84046 ' 1001 -710 1710 .5388 9.9 53485 228 74014' 84035 ' -1200 2200 .5094 -19.5 53435 I 1001 232 74014' 84024 ' 236 74014 84012 970 -1200 2170 .5148 -23.7 53350 ' 240 74014 84001' 948 -810 1760 .5365 - 8.7 53305 ' ' 950 -330 1280 .5551 11.2 53430 244 74013' 83049 ' 940 -330 1270 .5538 6.8 53420 248 74°13' 83038 ' 252 74013 83026 933 -460 1390 .5447 - 4.5 53460 ' ' -0.7 -13.1 53355 I 256* 74013 83015 928 -300 1230 .5500

' ' 972 -320 1290 .5386 1.4 53305 260 74013' 83004 264 74012 820511 977 -330 1310 .5381 3.3 53275 ' ' 268 74012 960 -310 1270 .5474 7.4 53245 ' 82040 ' 272 74012 963 -240 1200 .5527 13.6 53205 ' 82028 ' 276 74012 82016 955 - 80 1040 .5664 24.8 53100 I ' ' -210 .5816 20.8 53240 280 74011' 82004 897 1110 284 74011 908 -100 1010 .5848 29.5 53030 810521' 288* 740i1l 81041 918 -230 1150 .5779 25.7 8.4 52970 ' 292 740101 81030 891 -180 1070 .5881 28.4 52880 843 -350 1190 .5928 19.8 53000 I 787 -480 1270 .6009 13.1 52990 758 -420 1180 .6106 16.2 52890 ' 713 52920 80052 -600 1310 .6142 7.5 ' 744 -420 1160 .6144 16.5 52855 316 74002 800491 836 -550 1390 .5803 10.0 52705 I I 1 -73-

TABLE A (con't)

GENERAL DATA SUMMARY

Bouguer MagneticTotal Bed Rock Ice Observed Free Air Elevation Thickness Gravity Anomaly Anomaly Intensity Elevation 3 0 0 25y Station Latitude Longitude +70 or + m +20 or +300m -± 1 regal ± 15 rgal +13 mgal + + I' + 4' + 50 m -470 1330 982.5786 14.0 17.1 52725 857 320* 74003'S 80030'W' -320 1231 .5716 22.0 52780 911 324 74005' 80023' -400 1370 .5508 18.2 52765 971 328 74007' 80015' 60 950 .5647 41.7 52905 80007 1009 52915 332 74010'' ' 230 840 .5583 50.7 336 74012 80059 1065 52820 ' ' 50 1060 .5385 42.3 ' 79050 1107 29.9 52645 340 74014 1132 -210 1340 .5208 344 74017 79°43' 52545 ' ' -330 1490 .5082 24.4 79035 1160 -5.3 52650 348 74019' ' 80 1100 .5255 45.2 79027 1179 352* 74022 ' 350 820 .5434 60.0 52865 356 74024' 79020 1174 59.3 52665 ' ' 310 830 .5546 360 74027 79013 114. 53060 ' ' 710 380 .5946 80.8 74029 79007 1088 67.2 53005 364 ' ' 410 620 .6009 1031 368 74032 79001' 120 890 .6008 54.1 52710 74035' 78053 997 52805 372 ' ' 640 290 .6504 81.4 376 74038 78047 932 52860 ' ' 100 760 .6479 55.5 380 74040 78040 861 26.9 52830 ' ' -230 1050 .6463 40.5 382* 74041 78037 820 52815 ' ' -670 1470 .6308 16.0 74043 78034 796 10.2 52885 384 ' ' -730 1490 .6374 388 74045 78027 761 4.2 52945 ' ' -960 1030 .6441 - 392 74048 78020 700 52950 ' ' -1250 1930 .6348 -21.0 396 74051 78014 683 -16.9 52920 ' ' -1110 1740 .6571 78007 629 44.1 52905 400 74053' ' -1150 1710 .6762 -21.4 404* 74056 78100 560 -36.7 52960 ' ' -1480 2020 .6686 74058 77053 540 52945 408 ' ' -1920 2450 .6513 -58.0 412 75*01 77*46 534 52945 ' ' -1860 2360 .6695 -53.8 416 75*04 77039 496 -49.5 52915 ' ' -1790 2290 .6755 ' 77031' 495 52845 420 75006 -1620 2090 .6954 -40.0 424 75009 77024 469 68.1 52880 ' ' -1670 2050 .7064 -38.4 75012 77016 446 68.4 52940 428 ' -1670 2110 .7068 -40.7 432* 75014' 77009 442 53050 -1680 2130 .7038 -41.3 Eights Station 75015' 77006' 452 52870 433.5 ' ' -1860 2300 .6982 -47.3 436 75011' 77001' 444 52685 441 -1790 2230 .7026 -41.4 440 75009 76053 53045 ' ' -1160 1600 .7354 - 7.0 75006 76*46 439 53275 444 ' ' +90 390 .7878 +58.3 448 75*04 7639 476 52965 ' ' -1830 2400 .6646 -34.4 75002 76030 570 52790 452 ' -100 730 .7318 54.1 456 750001 76019 634 ' ' -250 930 .7125 49.5 52575 460 74058 76010 677 32.6 52405 ' ' +200 520 .7253 74.8 464* 74057 76000 715 52400 ' ' -640 1470 .6465 31.8 468 74055 75052 826 52315 ' ' -1880 2720 .5798 -31.0 472 74054 75041 836 52415 ' ' -1550 2400 .5901 -15.7 74053 75*29 850 476 ' ' -1280 2140 .6000 - 3.0 52320 859 480 74053' 75016 -800 1690 .6150 20.3 52275 484 74o53 75004' 886 52285 ' ' -270 1170 .6368 46.1 488 74*53 74052 899 ' ' 280 .6588 93.3 52215 492 74052 74040 978 700 ' ' 600 440 .6326 87.6 3.2 52165 74052 74028 1041 496* ' ' 430 660 .6159 84.4 52245 74916 1086 500 74051' ' 600 500 .6277 98.6 52099 74052 74005 1096 -5.6 52060 504 ' ' 1200 0 .6263 130.0 505.2*** 74052 74002 1202 HIM ' ' 1030 .6180 66.8 52140 74053 74005 1027 0 52185 508 ' ' -1480 2520 .5399 -10.9 74057 74002 1038 52345 512 ' ' -1000 2030 .5661 9.9 516 75100 73058 1028 4.3 52270 ' ' -1040 2100 .5498 520 74059 73044 1060 52685 ' ' -300 1400 .5731 38.4 524 74059 73034 1095 ' ' 52670 528 74059 73022 1163 260 900 .5762 62.5 ' ' 630 .5644 77.5 52395 532 74059 73010 1250 620 ' ' 240 1060 .5283 54.8 51995 536 75000 73000 1296 -42.3 51980 ' ' 1320 0 .5729 106.9 lm 538.5** 75100 72°53 1320 51725 ' ' 190 1090 .5288 50.0 544 75*01 72046 1281 51635 ' ' -340 1620 .5655 84. 1 72034 1275 548 75002' ' 460 810 .5466 62.4 51815 552 75002 72022 1266 -32.9 52345 ' ' 1374 0 .5694 118.5 NlM 72018 1374 -41.2 52135 NIM 553.5*** 75002' ' 1340 0 .5755 114.1 72018 1340 51965 553.7*** 75002 ' ' 720 670 .5186 74.6 556 74059 72017 1389 52190 ' ' 1030 370 .5279 89.3 74058 72006 1404 52400 560 ' ' -240 1590 .4795 25.3 71059 1346 564 74055' ' -680 2050 .4471 2.6 74052 71051 1370 568 ' ' 310 1130 .4722 51.7 51800 572 74050 71042 1443 16.1 51710 ' ' -390 1860 .4275 576 74"47 71044 1465 51755 ' ' -50 1560 4306 32.6 580 74048 71039 1511 51790 ' ' 470 1040 .4567 58.0 74049 71037 1511 -44.5 51920 D2M 584 ' ' 1240 - 20 .4857 96.4 585.4* 74050 71035 1544 51810 ' ' 860 210 .4559 76. 7 588 74048 ' 71030' 1572 56.0 51715 592 74145 71124 1625 450 1180

' 46.6 51575 596 741431 71117 1o63 280 1380 .3938 ' 69.9 -51.•0 51620 600 74040 7101 1712 750 960 .3997 ' . 84.1 -62.8 51690 604* 74°381 71103 1802 1050 750 3846 ' ' 72.3 51805 *00 74135 70156 1851 840 1010 .3554 ' .3636 79.2 51755 2 74°321 70150 1839 1000 040 I

TABLE A (con't) GENERAL DATA SUMMARY I

Total Bed Rock Ice Observed Free Air Bouguer Magnetic Station Latitude Longitude Elevation Elevation Thickness Gravity Anomaly Anomaly Intensity + 1' + 4' + 50 m +70 or +300m +20 or +300m ± I mgal + 15 mgal 13 mgal + 25 y 70043'W I 1797 1230 570 982.3851 89.3 52090 616 74030'S ' 70037 1747 930 820 .3819 73.0 51550 620 74027'' ' 1665 1120 550 .4132 81.3 51465 624 74o24' 70030 ' 70024 1561 260 1300 .3991 36.7 51180 628 74022' ' 632 74o19 70017 1483 -120 1600 .4004 16 3 51085 ' ' 70010 1434 -620 2050 .3871 - 9.8 -16.6 51305 636* 74o16 ' I 70005 1415 -940 2360 .3758 -24.6 -16.7 51215 640 74013'' ' 644 74011 69059 1394 - 50 1440 .4264 21.1 51095 ' .4607 648 74008' 69054 ' 1328 -250 1080 37.4 51190 652 74005' 69048 1323 -290 1610 .4343 11.9 51260 ' ' 69043 656 74002 ' 1309 -640 1950 .4201 -4.2 51240 ' 69038 660 74000 1266 -750 2020 .4275 - 8.5 51025 ' ' I 664 73057 69032' 1248 -430 1680 .4479 8.7 51000 ' 69026 73°54 ' 1215 -360 1580 .4605 13.5 - 5.7 51045 668* 69021 672 730511 1177 -300 1480 .4761 19.8 51165 ' ' 1153 -510 1660 .4736 12.3 50911 676 73048' 69015 ' 69010 1132 -J10 1640 .4817 15.6 50831 680 73046' ' 684 73043 69004 1128 -470 1600 .4855 20.6 50735 ' I 688 73040' 68058' 1132 -330 1460 .4922 30.9 50825 692 73037' 68052 1112 -420 1530 .4944 29.5 50865

' ' .5128 40.2 50690 696 73035' 68046' 1082 -260 1340 ' 1230 .5291 47.6 21.7 50785 700* 73032 68040' 1045 -180 704 73033 1131 -110 .5050 49.2 50680 ' 68029 1240 708 73035 68019, 1174 -160 1330 .4885 44.3 51255 ' ' I 712 73036 68009 1208 280 930 .4991 64.6 50790

' ' .4844 73.8 50925 716 73037' 67058' 1288 510 780 720 73038 67048' 1354 370 980 .4560 64.9 51055 ' 67038 724 73040 ' 1442 410 1030 .4305 64.9 50785 67027 728 73041' ' 1488 480 1010 .4183 66.1 50590 732* 73943' 67017 1575 320 1260 .3833 56.3 -27.3 50505 I ' ' ' 67006 1680 - 20 1700 .3329 37.5 50200 736 73044 ' 740 73°45 50280 66056 ' 1711 - 60 1770 .3209 34.3 744 730481 50320 ' 66052 ' 1766 +160 1610 .3159 43.8 748 73051' 66049' 1828 640 1190 .3213 65.9 50365 752 73054 66046 1925 900 1030 .3055 77.7 50405 ' ' I 756 73058 1974 640 1330 .2788 ' 66042 ' 62.9 50460 2036 1070 970 83.1 50880 760 74'01' 66040 ' .2823 764* 74o04 66036 ' 2120 1230 890 .2651 89.4 -83.1 50585 50495 768 74°007' 66037' 2185 1310 880 .2543 96.3 772 74010 66041 2256 1540 720 .2492 110.7 50635 ' ' 66045 776 74o13' ' 2269 940 1330 .2209 84.0 50455 I 780 74016 66050 2288 1000 50720 ' ' 1290 .2228 89.5 784 74'19' 66054 2282 1270 1010 .2438 106.2 50775 788 74021 66o59' 2238 870 1370 .2418 89.0 50850 ' ' 792 74024 67004 2210 850 1360 .2546 90.9 50590 ' 796* 74027' 670081' 2150 990 1160 .2855 101.0 -54.6 50660 799.1* 74029' 67013 2119 450 1670 .3216 75.9 -37.8 50700 I 802.06* 74031 67019, ' 2113 1240 870 .2922 93.1 -80.5 50870 805.06* 740341 67024 2063 968 1100 .3075 -60.0 51040 ' ' 90.6 808.09* 74037 67028 2029 950 1080 .3207 91.8 -56.3 51060 ' ' ' 812 74039' 67031 1978 600 1380 .3197 72.7 50915 816 74042 67037 ' ' 1969 920 1050 .3395 87.4 51145 820 74044 67042 ' 1896 1090 810 .3711 95.0 51245 I ' 67048 824 74047' 1821 950 870 .3886 87.1 51285 828 74)50 670541 1800 800 1000 .3891 78.8 51500 ' 832 74053 67 59' ' ' 1738 990 750 .4190 87.2 51370 836 74055 ' 68005 ' 1679 - 60 1740 .3852 33.7 51225 840* 74058 ' 68011' 1721 1250 470 .4393 98.5 -60.5 51540 844 75001 68018 1724 1250 470 .4462 104. 1 51840 I 848 75°04' 68018' 1651 850 800 .4564 89.5 51910 ' ' 850.36*** 75006 ' 68021 ' 1637 1620 20 .5042 131.5 -51.5 51620 U2M 852 75o04 52035 ' 68020' 1653 1200 450 .4749 108.6 856 75002 ' 68028 ' 1705 1280 430 .4565 107.8 52095 860 75002 68039 1644 980 660 .4558 88.2 51575 864* 75001, I 68052. 1623 720 980 .4439 70.7 -44.6 51430 ' ' 868 75001' 69003 ' 1584 1240 340 .4826 97.3 51955 872 75003 69014 ' 1562 1390 170 .4987 105.1 51495 872.36*** 75003'' 69015 1568 1568 0 .5121 120.4 -56.9 51535 P3M 876 75)03 69027'' 1449 1190 260 .5237 95.3 51585 880 75004' 69038 1399 310 1090 .4967 52.0 51630 I ' ' 884 75006' 69049 ' 1354 -530 1880 .4704 10.3 51720 888 75007 70001 ' 1356 -290 1650 .5118 51.7 51820 70009 52095 892 75009'' ' 1462 1310 150 .5417 112.8 70011 1414 1410 0 .5533 108.8 -50.5 52025 892.7*** 75010' E4M 896 75011 70019 1296 400 9O0 5425 60. 6 51800 ' 900 75012 ' 70030' 1340 690 650 .5468 77.9 51875 I 904 75014 70041. ' 1313 700 610 5601 81.4 51955 908* 75016 ' 70°50'' 1253 690 560 .5820 83.3 -15.8 51640 912 75o18 71002 1175 530 650 .5917 67.5 50865 I I I -75-

TABLE A (con't)

GENERAL DATASUMMARY

Total Bed Rock Ice Observed Free Air Bouguer Magnetic Station Latitude Longitude Elevation Elevation Thickness Gravity Anomaly Anomaly Intensity +if' + 4' + 50 m +70 or +300m +20 or +300m + I mgal + 15 egal + 13 egal + 25 y 75019'S 916 ' 71013'W' 1106 660 450 982.6125 66.2 75021 71026 51870 920.5*** ' 1052 1020 30 .6556 91.9 -24.5 75022 52070 15M 924 ' 71035'' 939 70 870 .6360 36.0 52040 75023 71046 -390 928 ' 872 1260 .6368 15.4 52110 75024' 71058 932 842 -890 1730 .6244 -7.1 52045 ' ' 75026 72010 936 ' ' 815 -1150 1970 .6235 -17.8 75*27 72002 52115 940* ' 777 -1150 1930 .6381 -15.6 75*28' 72033 41.7 52205 944 ' 712 -690 1400 .6809 + 6.4 75031 720281 52400 948 ' ' 674 -1450 2120 .6558 -32.6 75034 72021 52255 952 654 -1680 2330 .6513 -45.5 52300 ' ' 75035 72033 956 ' ' 615 -1880 2500 .6534 -56.1 72045 52350 960 75035 ' ' 604 -1830 2430 .6578 75034 72059 -55.1 52370 964 ' ' 592 -1610 2200 .6711 75034 73010 -44.8 52465 968 ' ' 573 -1400 1970 .6864 -35.4 75034 73023 52465 972 542 -1260 1800 .7018 -29.5 52445 ' ' 75034 73037 976* ' ' 524 -1140 1660 .7123 -24.6 75034 73049 41.5 52480 980 ' 583 -410 990 .7355 16.8 75*34 74004' 52595 984 ' ' 584 -300 880 .7455 27.1 75034 74016 52935 988 ' ' 472 -720 1190 .7641 75034 74029 11.2 53460 992 486 -810 1300 .7602 11.6 52935 ' ' 75031 74039 996 ' 507 -990 1500 .7472 75028' 74042 7.3 52730 1000 ' ' 500 -1230 1730 .7402 75025 74048 0.3 52635 1004 ' ' 497 -1080 1580 .7513 12.7 75022 74054 52565 1008* ' 520 -860 1380 .7578 28.5 75021 75006' 73.7 52545 1012 507 -460 970 .7787 46.1 52730 ' 75020' 75018 1016 ' 485 -690 1180 .7707 32.1 75*19 75*31' 52885 1020 ' ' 439 -900 1340 .7715 19.4 75018 75042 53360 1024 ' ' 427 -1250 1680 .7545 - 0.5 75018 75054 53135 1028* ' ' 438 -1490 1930 .7365 -15.1 80.6 52675 75017 76006 1032 453 -1600 2050 .7230 -23.3 52600

1036 75016' 76019' ' ' 445 -1580 2030 .7230 -25.1 52610 1040 75015 76031 ' ' 445 -1660 2110 .7154 -31.9 52615 1044 75014' 76043 450 -1800 2250 .7037 -41.3 52720 1048 75*13 76054' ' ' 441 -1800 2240 .7031 -43.9 52815 1052.7 75015 77006 452 -1680 2130 .7038 -41.3 53050 Eights Station

*Seismic reflection station **Stations 120-204 overlap E.H.T. ***Nunatak, USGS designation of peak -76- I

TABLE B I DETAILED ELEVATION AND MAGNETIC DATA (Values adjusted to tabulation in Table A) Integral numbered stations at 1.45 km intervals; decimals indicate proportional intermediate spacing I Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Elation Elevation Intensity Oration Elevation -Intensity

0 558 m 55285 y 40.0 1020 m 54980 2 80.0 1039 m 0.5 553 52280 40.5 1023 54960 80.5 1027 1.0 549 52230 41.2 1026 54900 81.0 1027 1.5 542 52190 41.5 1032 54900 81.5 1031 I 2.0 536 52150 42.0 1040 54860 82.0 1038 2.5 531 52120 42.5 1048 54850 82.5 1051 3.0 525 52120 43.0 1043 54820 83.0 1057 3.5 518 52130 43.5 1043 54800 83.5 1058

4.0 512 55155 44.0 1041 54780 84.0 1072 4.5 469 55175 44.5 1045 54775 84.5 1077 I 5.0 462 55155 45.0 1045 54790 85.0 1075 5.5 451 55165 45.5 1037 54800 85.5 1110 6.0 434 55140 46.0 1030 54800 86.0 1127 6.5 427 55140 46.5 1019 54780 86.5 1135 7.0 421 55155 47.0 1011 54785 87.0 1133 7.5 430 55195 47.5 1006 54760 87.5 1137 I 8.0 421 55170 48.0 1002 54755 88.0 1131 8.5 433 55180 48.5 993 54780 88.5 1146 9.05 442 55165 49.0 983 54760 89.0 1170 9.5 458 55150 49.5 966 54720 89.5 1185 10.05 476 55185 50.0 962 54695 90.0 1189 10.6 503 55185 50.5 960 54695 90.5 1194 11.0 513 55185 51.0 966 54675 91.0 1197 I 11.5 532 55185 51.5 971 54680 91.6 1198

12.0 535 55185 52.0 972 54670 92.0 1208 12.5 507 55200 52.5 972 54685 92.5 1214 13.0 486 55170 53.1 962 54675 93.0 1219 13.5 476 55210 53.5 963 54670 93.5 1224 14.0 457 55115 54.0 970 54665 94.0 1226 I 14.5 473 55160 54.5 959 54680 94.5 1224 15.0 474 55180 55.0 943 54690 95.0 1227 15.5 483 55145 55.5 944 54680 95.5 1232

16.0 492 55095 56.0 936 54660 96.0 1238 16.6 506 55075 56.5 931 54680 96.5 1241 17.0 506 55065 57.0 939 54680 97.0 1243 I 17.5 510 55050 57.5 947 54710 97.5 1241 18.0 529 55035 58.0 948 54750 98.0 1238 18.5 546 55035 58.5 948 54810 98.5 1237 19.0 558 55050 59.0 948 54780 99.0 1231 19.5 570 55135 59.6 944 54800 99.5 1228

20.0 592 55245 54765 U 60.0 931 100.0 1235 20.5 612 55240 60.5 920 100.5 1234 21.0 619 55210 61.0 916 101.0 1235 21.5 637 55120 61.5 916 101.5 1235 22.3 656 55035 62.0 914 102.0 1234 22.5 666 55015 62.5 911 102.5 1230 23.2 690 55000 63.0 909 103.0 1232 23.6 705 I 55000 63.5 912 103.5 1229

24.0 706 55000 64.0 908 104.0 1229 24.5 735 55020 64.5 900 104.5 1227 25.0 754 55010 65.0 895 105.0 1224 25.5 772 54995 65.5 889 105.5 1223 26.0 778 55025 66.0 893 106.0 1219 I 26.5 787 55045 66.5 895 106.5 1213 27.0 808 55015 67.0 898 107.0 1205 27.5 829 54990 67.5 904 107.5 1201

28.0 838 54995 68.0 909 108.0 1200 28.5 850 54935 68.5 911 108.5 1193 29.0 862 54930 69.0 915 109.0 1190 I 29.6 873 54930 69.5 923 109.5 1183 30.0 884 54930 70.0 929 110.0 1178 30.5 896 54940 70.5 935 110.5 1173 31.0 900 54960 71.0 940 111.0 1165 31.5 903 54980 71.5 946 111.5 1160 32.0 909 55000 72.0 947 112.0 1194 I 32.5 916 55045 72.5 949 112.4 1195 54305 33.0 55085 73.0 947 113.0 1197 54310 33.5 928 55100 73.5 953 113.5 1201 54315 34.0 944 55085 74.0 963 114.0 1201 54325 34.6 947 55060 74.5 972 114.5 1201 54335 35.0 55080 75.0 984 115.0 1207 54340 35.5 959 55075 75.5 991 115.6 1214 54345 I 36.0 973 55045 76.0 998 116.0 1213 54340 36.5 985 55020 76.5 1003 116.5 1215 54340 37.0 990 54985 77.0 1002 117 0 1220 54335 37.5 998 54965 77.5 1009 117.5 1227 54335 38.0 1004 54945 78.0 1006 118.0 1233 54330 38.5 1005 54935 78.5 1010 118.5 1239 54330 I 39.0 1003 54945 79.0 1029 119.0 1249 54325 54950 39.5 1008 79.5 1040 119.5 1242 54320 I I I TABLE B (con't)

Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Station Elevation Intensity Station Elevation Intensity

120.0 1245 m 54315 y 164.0 1162 m 53970 208.0 1.189o 53645 y 120.5 1247 54315 164.5 1182 53955 208.5 1184 53640 121.0 1246 54310 165.0 1198 53955 209.0 1181 53640 121.5 1240 54310 165.5 1201 53945 209.5 1177 53640 122.0 1240 54310 166.0 1202 53960 210.0 1178 53640 122.5 1240 54305 166.5 1207 53965 210.5 1174 53640 123.0 1235 54305 167.0 1210 53965 211.0 1172 53640 123.5 1230 54300 167.5 1217 53965 211.5 1171 53640

124.0 1227 54290 168.0 1217 53975 212.0 1164 53635 124.5 1224 54280 168.5 1211 53980 212.5 1160 53635 125.0 1219 54270 169.0 1207 53980 213.0 1156 53625 125.5 1217 54270 169.5 1206 53985 213.5 1153 53620 126.0 1209 54270 17C.0 1211 54000 214.0 1147 53630 126.5 1205 54255 170.5 1223 54010 214.5 1145 53625 127.0 1202 54250 171.0 1227 54015 215.0 1140 53635 127.5 1199 54250 171.5 1235 53995 215.5 1137 53630

128.0 1191 54245 172.0 1228 53995 216.0 1133 53630 128.5 1183 54245 172.5 1232 53990 216.5 1125 53630 129.0 1173 54240 173.0 1235 53995 217.0 1126 53630 129.5 1167 54230 173.5 1239 54000 217.5 1118 53635 130.0 1165 54230 174.0 1242 54010 218.0 1113 53630 130.5 1162 54225 174.5 1244 54000 218.5 1110 53620 131.0 1158 54225 175.0 1247 53980 219.0 1107 53615 131.5 1158 54215 175.5 1248 53975 219.5 1099 53610

132.0 1155 54210 176.0 1249 53960 220.0 1091 53610 132.5 1154 54215 176.5 1251 53955 220.5 1091 53600 133.0 1150 54205 177.0 1249 53955 221.0 1085 53600 133.5 1147 54200 177.5 1249 53955 221.5 1081 53590 134.0 1145 54190 178.0 1247 53945 222.0 1075 53575 134.5 1140 54190 178.5 1247 53940 222.5 1071 53570 135.0 1139 54190 179.0 1244 53935 223.0 1069 53570 135.5 1137 54185 179.5 1244 53925 223.5 1064 53570

136.0 1131 54180 180.0 1245 53920 224.0 1055 53560 136.5 1126 54175 180.5 1247 53915 224.5 1049 53550 137.0 1121 54170 181.0 1246 53915 225.0 1044 53535 137.5 1118 54165 181.5 1242 53905 225.5 1038 53530 138.0 1117 54165 182.0 1243 53905 226.0 1032 53525 138.5 1117 54165 182.5 1244 53905 226.5 1021 53520 139.0 1119 54160 183.0 1243 53900 227.0 1010 53505 139.5 1118 54150 183.5 1243 53900 227.5 1003 53500

140.0 1113 54140 184.0 1242 53895 228.0 1001 53485 140.5 1112 54140 184.5 1242 53885 228.5 1004 53485 141.0 1117 54140 185.0 1245 53885 229.0 1008 53475 141.5 1117 54130 185.5 1252 53875 229.5 1012 53470 142.0 1119 54130 186.0 1259 53850 230.0 1015 53465 142.5 1118 54120 186.5 1259 53850 230.5 1015 53455 143.0 1120 54120 187.0 1257 53835 231.0 1010 53455 143.5 1122 54120 187.5 1258 53830 231.5 1006 53445

144.0 1115 54120 188.0 1260 53830 232.0 1001 53430 144.5 li 54120 188.5 1261 53810 232.5 997 53415 145.0 1110 54130 189.0 1259 53805 233.0 992 53410 145.5 1113 54135 189.5 1255 53800 233.5 987 53405 146.0 1116 54115 190.0 1253 53785 234.0 983 53390 146.5 1123 54040 190.5 1256 53780 234.5 981 53385 147.0 1126 191.0 1254 53780 235.0 977 53375 147.5 1126 53955 191.5 1253 53770 235.5 972 53360

148.0 1125 53955 192.0 1250 53770 236.0 970 53350 148.5 1134 53955 192.5 1244 53760 236.5 967 53340 149.0 1143 53925 193.0 1245 53750 237.0 962 53345 149.5 1148 53915 193.5 1259 53750 237.5 962 53320 150.0 1152 53955 194.0 1246 53745 238.0 966 53305 150.5 1149 54010 194.5 1242 53730 238.5 966 53300 151.0 1148 54030 195.0 1240 53730 239.0 965 53300 151.5 1157 54050 195.5 1244 53725 239.5 964 53300

152.0 1160 54050 196.0 1245 53720 240.0 948 53305 152.5 1159 54050 196.5 1242 53710 240.5 937 53330 153.0 1158 54050 197.0 1243 53695 241.0 941 53340 153.5 1151 54050 197.5 1243 53695 241.5 943 53355 154.0 1148 54035 198.0 1243 53710 242.0 944 53380 154.5 1148 54030 198.5 1244 53700 242.5 946 53390 155.0 1152 54030 199.0 1242 53700 243.0 949 53405 155.5 1153 54015 199.5 1232 53700 243.5 952 53430

156.0 1156 54010 200.0 1229 53700 244.0 950 53430 156.5 1158 54010 200.5 1227 53690 244.5 948 53430 157.0 1156 54005 201.0 1225 53690 245.0 944 53430 157.5 1154 53995 201.5 1225 53665 245.5 942 53450 158.0 1156 53990 202.0 1224 53670 246.0 940 53455 158.5 1149 53990 202.5 1220 53670 246.5 940 53465 159.0 1148 54050 203.0 1221 53665 247.0 939 53450 159.5 1148 53975 203.5 1217 53670 247.5 940 53435

160.0 1141 53970 204.0 1220 55670 248.0 940 53420 160.5 1139 53970 204.5 1216 53670 248.5 941 53410 161.0 1141 53910 205.0 1214 53665 249.0 939 53410 161.5 1146 53990 205.5 1207 53670 249.5 937 53410 162.0 1143 54010 206.0 1203 53660 250.0 934 162.5 1140 54070 206.5 1199 53660 250.5 943 53440 163.0 1147 54120 207.0 1209 53670 251.0 940 53480 163.5 1132 54025 207.5 1199 53670 251.5 935 53490 I

TABLE B (con't) I Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Station Elevation Intensity Sta tion Elevation Intensity

252.0 933 m 53460 y 296.0 843 m 53000 340.0 1107 m 52820 r 25. 933 53385 296.5 831 53005 340.5 1116 52840 253.0 938 53320 297.0 824 53020 341.0 1125 52845 I 253.5 939 53285 297.5 827 53040 341.5 1124 52850 254.0 945 53260 298.0 825 53070 342.0 1121 52850 254.5 947 53265 298.5 822 53075 342.5 1129 52840 255.0 945 53285 299.0 813 53055 343.0 1129 52865 255.5 938 53305 299.5 794 53000 343.5 1130 52855 256.0 928 53355 300.0 787 52990 344.0 1132 52645 I 256.5 917 53375 300.5 771 52960 344.5 1135 52625 257.0 926 53395 301.0 770 52935 345.0 1138 52620 257.50 934 53405 301.5 754 52925 345.5 1138 52560 258.0 938 53400 302.0 756 52940 346.0 1145 52600 756 258.5 947 53380 302.5 52920 346.5 1151 52600 259.0 951 53355 303.0 757 52920 347.0 1151 52590 259.5 965 53320 303.5 758 52900 347.5 1156 52560 I 260.0 972 53285 304.0 758 52890 348.0 1160 52545 260.5 977 53270 304.5 756 52875 348.5 1166 52565 261.0 980 53250 305.0 747 52915 349.0 1170 52570 261.6 977 53250 305.5 731 52940 349.5 1172 52575 262.0 974 53260 306.0 722 52970 350.0 1172 52585 262.5 969 53275 306.5 716 52970 350.5 1172 52595 I 263.0 971 53280 307.0 714 52965 351.0 1174 52600 263.5 976 53280 307.5 712 52945 351.5 1176 52650

264.0 977 53275 308.0 713 52920 352.0 1179 52650 264.5 976 53270 308.5 700 52875 352.5 1182 52630 265.0 974 53265 309.0 681 52855 353.0 1182 52670 265.5 973 53265 309.5 688 52900 353.5 1183 52710 I 266.0 969 53245 310.0 710 52880 354.0 1182 52750 266.5 965 53240 310.6 736 52900 354.5 1178 52765 267.0 968 53240 311.0 740 52905 355.0 1173 52800 267.5 965 53240 311.5 732 52825 355.5 1174 52840

268.0 960 53245 312.0 744 52855 356.0 1174 52865 268.5 964 53245 312.62 766 52820 356.5 1171 52880 I 269.0 965 53245 313.0 770 52815 357.0 1173 52905 269.5 971 53250 313.5 788 52810 357.5 1173 52940 270.1 972 53245 314.0 799 52825 358.0 1170 52940 270.5 972 53240 314.5 793 52800 358.5 1162 52875 271.0 967 53220 315.0 808 52775 359.0 1156 52780 52685 271.5 964 53220 315.5 818 52750 359.5 1152 I 272.0 963 53205 316.0 836 52705 360.0 1143 52665 272.5 968 53185 316.5 843 52675 360.5 1137 52705 273.0 968 53180 317.0 840 52675 361.0 1134 52805 273.5 965 53165 317.5 836 52685 361.5 1129 52940 274.0 957 53155 318.0 833 52695 362.0 1120 53000 274.5 952 53135 318.5 835 52715 362.5 1107 53010 275.0 952 53130 319.0 844 52720 363.0 1109 53045 I 275.5 952 53110 319.5 852 52725 363.5 1102 53080

276.0 955 53100 320.0 857 52725 364.0 1088 53060 276.5 959 53090 320.5 860 52755 364.5 1071 53040 277.0 956 53090 321.0 867 52755 365.0 1067 53000 277.5 957 53090 321.5 873 52765 365.5 1069 53010 278.0 932 53105 322.0 885 52785 366.0 1066 53020 I 278.5 914 53160 322.5 896 52795 366.5 1060 53040 279.0 901 53185 323.0 906 52775 367.0 1054 53040 279.5 898 53200 323.5 908 52765 367.5 1050 53025

280.0 897 53240 324.0 911 52780 368.0 1031 53005 280.5 894 53225 324.5 918 52795 368.5 1019 52985 325.0 922 52795 369.0 1005 52930 I 281.0 891 53185 281.5 885 53155 325.4 920 52800 369.5 1000 52870 282.0 894 53125 326.1 930 52810 370.0 998 52810 282.5 902 53095 326.5 945 52815 370.5 996 52750 283.0 899 53070 327.0 958 52795 371.0 998 52710 283.5 903 53050 327.5 970 52750 371.5 1002 52695 I 284.0 908 53030 328.0 971 52765 372.0 997 52710 284.5 914 53025 328.5 961 52810 372.5 993 52750 285.0 928 53005 329.0 975 52850 373.0 989 52765 285.5 930 52985 329.5 991 52850 373.5 985 52790 286.0 929 52980 330.0 993 52835 374.0 976 52800 286.5 928 52970 330.5 990 52855 374.5 968 52805 287.0 928 52970 331.0 992 52915 375.0 956 52805 I 287.5 925 52970 331.5 1000 52925 375.5 946 52805

288.0 918 52970 332.0 1009 52905 376.0 932 52805 288.5 911 52980 332.5 1018 52885 376.5 914 52810 289.0 902 52970 333.0 1024 52865 377.0 908 52810 289.5 895 52960 333.57 1031 52895 377.5 903 52830 290.0 893 52940 334.0 1039 52835 378.0 891 52850 I 290.5 895 52920 334.58 1045 52875 378.5 878 52860 291.0 891 52920 335.0 1051 52915 379.0 871 52860 291.5 891 52900 335.5 1060 52935 379.5 847 52860

292.0 52880 336.0 1065 52915 380 0 861 52860 292.5 885 52865 336 .5 1074 52890 380 5 853 52850 293.0 885 5286S 337.0 1078 52875 381.0 838 52850 293.5 884 1083 52855 I 52865 337.5 381.5 824 52845 294.0 877 52890 338.0 1088 52830 382.0 807 52835 294.5 872 52925 338.5 1095 52815S 382.5 797 52825 295.0 867 52955 339 .c 1101 528B0S 791 52820 295.5 855 52975 339.5 1106 52810 383.5 792 52815 I I I _79-

TABLE B (con't)

Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Station Elevation Intensity Station Elevation Intensity

384.0 996 m 52815 V 428.0 446 m 52880 468.0 826 m 52400 384.5 798 52830 428.5 453 52895 468.5 829 52395 385.0 796 52835 429.0 456 52925 469.0 829 52375 385.5 789 52850 429.5 453 52945 469.5 830 52370 386.0 782 52860 430.0 446 52955 470.0 828 52355 386.5 773 52880 430.5 437 52975 470.5 832 52340 387.0 769 52885 431.0 428 52985 471.0 837 52330 387.5 768 52885 431.5 422 53000 471.5 837 52320 388.0 761 52885 432.0 442 53020 472.0 836 52315 388.5 750 52905 432.5 449 53020 472.5 833 52320

389.0 743 52915 433.0 451 53020 473.0 833 52310 389.5 739 52925 433.5 452 53015 473.5 836 52360 390.0 734 52930 (Eights Station) 474.0 838 52400 390.5 728 52940 474.5 843 52425 391.0 717 52950 432.5a 450 53010 475.0 846 52445 391.5 708 52945 433a 453 53000 475.5 846 52440 433.5a 458 52985 392.0 700 52945 The above 3 stations progress east from 476.0 850 52415 392.5 696 52945 432 to 434. 476.5 852 52385 393.0 688 52955 434.0 455 52955 477.0 850 52360 393.5 681 52960 434.5 454 52930 477.5 849 52350 394.0 680 52965 435.0 454 52920 478.0 851 52350 394.5 682 52960 435.5 452 52820 478.5 854 52350 395.0 684 52960 479.0 856 52350 395.5 685 52955 436.0 52870 479.5 860 52320 436.5 442 52850 396.0 683 52950 437.0 441 52830 480.0 859 52320 396.5 678 52955 437.5 447 52795 480.5 859 52290 397.0 681 52955 438.0 444 52775 481.0 864 52285 397.5 685 52955 438.5 444 52750 481.5 864 52280 398.0 688 52945 439.0 445 52720 482.0 868 52280 398.5 684 52940 439.5 445 52700 482.5 870 52275 399.0 671 52945 483.0 873 52280 399.5 653 52920 440.0 441 52685 483.5 881 52285 440.5 437 52660 400.0 629 52920 441.0 435 52660 484.0 886 52275 400.5 619 52910 441.5 435 52680 484.5 889 52275 401.0 621 52910 442.0 435 52710 485.0 892 52270 401.5 628 52905 442.5 436 52770 485.5 897 52270 402.0 610 52900 443.0 436 52870 486.0 898 52280 402.5 619 52895 443.5 437 52985 486.5 899 52290 403.0 595 52900 487.0 897 52290 403.5 579 52900 444.0 439 53045 487.5 897 52285 444.5 443 53350 404.0 560 52905 445.0 445 53515 488.0 899 52285 404.5 558 52870 445.5 450 53600 488.5 899 52330 405.0 557 446.0 452 53585 489.0 905 52370 405.5 556 52900 446.5 516 53520 489.5 921 52365 406.0 548 52915 447.0 466 53440 490.0 939 52310 406.5 544 52935 447.5 470 53375 490.5 945 52250 407.0 549 52945 491.0 955 52230 407.5 541 52955 448.0 476 53325 491.5 962 52230 448.5 505 53280 408.0 540 52960 449.0 519 53210 492.0 978 52215 408.5 540 52950 449.5 527 53155 492.5 988 52205 409.0 542 52945 450.0 537 53125 493.0 997 52200 409.5 542 52930 450.5 551 53085 493.5 999 52195 410.0 542 52940 451.0 562 53050 494.0 1004 52185 410.5 539 52925 451.5 571 53000 494.5 1016 52180 411.0 536 52970 495.0 1033 52180 411.5 534 52965 452.0 570 52965 495.5 1040 52175 452.5 563 52930 412.0 534 52945 453.0 556 52920 496.0 1041 53165 412.5 539 52960 453.5 556 52880 496.5 1051 53185 413.0 539 52955 454.0 556 52880 497.0 1060 53200 413.5 540 52960 454.5 571 52865 497.5 1064 53240 414.0 537 52960 455.0 582 52835 498.0 1071 53285 414.5 532 52960 455.5 612 52805 498.5 1070 53290 415.0 521 52950 499.0 1082 53280 415.5 510 52945 456.0 634 52790 499.5 1087 53260 456.5 646 52750 416.0 496 52945 457.0 657 52710 500.0 1086 52245 416.5 484 52955 457.5 662 52675 500.5 1082 52225 417.0 480 52945 458.0 669 52645 501.0 1078 52215 417.5 483 52940 458.5 676 52620 501.5 1078 52210 418.0 489 52935 459.0 679 52600 502.0 1081 52165 418.5 490 52935 459.5 675 52590 503.0 1089 52100 419.0 492 52940 503.5 1090 52110 419.5 495 52920 460.0 677 52575

464.5 640 52400 508.0 1027 521400 424.0 49 52840 465.0 830 52400 508.5 1024 52145 I424.5 466 52840 465.5 724 52400 509.0 1028 52145 425.0 466 52830 46.0 869 52530 509.5 1029 52165 425.5 468 52835 466.5 853 52390 50.0 1035 52160 426.0 467 52840 467.0 803 52350 50.5 1036 52160 426.5 46 52865 467.5 826 52390 511.0 1035 52170 427.0 452 52855 511.5 1036 52175 U427.5 446 52870 439 1 20 I T 80 o

TABLE B (con't) I Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Station Elevation Intensity Station Elevation Intensity

512.0 1038 m 52185 v 556.0 1389 m 51965 600.0 1712 m 51620 y 512.5 1035 52190 556.5 1384 51890 600.5 1729 51695 513.0 1035 52210 557.0 1380 51845 601.0 1747 51705 I 513.5 1034 52225 557.5 1383 51950 601.5 1752 51700 514.0 1033 52245 558.0 1388 51885 602.0 1754 51700 514.5 1033 52275 558.5 1412 52040 602.5 1762 51755 515,0 1030 52305 559.0 1432 52260 603.0 1779 51760 515.5 1028 52325 559.5 1415 52090 603.5 1794 51725 516.0 1028 52345 560.0 1404 52190 604.0 1802 51690 I 516.5 1024 52325 560.5 1385 52550 604.5 1814 51665 517.0 1029 52305 561.0 1380 52580 605.0 1820 51665 1822 517.5 1039 52285 561.5 1363 52720 605.5 51660 518.0 1045 52275 562.0 1358 52670 606.0 1828 51690 518.5 1049 52300 562.5 1357 52615 606.5 1833 51740 519.0 1053 52300 563.0 1354 52580 607.0 1839 51810 519.5 1059 52300 563.5 1350 52495 607.5 1840 51840 I 520.0 1060 52270 564.0 1346 52400 608.0 1851 51805 520.5 1062 52245 564.5 1344 52285 608.5 1851 51750 521.0 1063 52230 565.0 1339 52210 609.0 51735 521.5 1062 52230 565.5 1337 52095 609.5 1852 51725 522.0 1063 52275 566.0 1333 52050 610.0 1854 51715 522.5 1070 52365 566.5 1339 51985 610.5 1854 51720 I 523.0 1077 52485 567.0 1347 51935 611.0 1856 51715 523.5 1085 52585 567.5 1356 51910 611.5 1862 51720

524.0 1095 52685 568.0 1370 51875 612.0 1839 51745 524.5 1100 52780 568.5 1380 51850 612.5 1834 51740 525.0 1110 52850 569.0 1389 51825 613.0 1833 51725 525.5 1119 52740 569.5 1394 51810 613.5 1838 51735 I 526.0 1129 52720 570.0 1397 51805 614.0 1837 51815 526.5 1140 52525 570.5 1401 51815 614.5 1831 51945 527.0 1154 52585 571.0 1405 51810 615.0 1819 52110 527.5 1158 52730 571.5 1416 51805 615.5 1802 52130

528.0 1163 52670 572.0 1443 51800 616.0 1797 52090 528.5 1176 52640 572.5 51740 616.5 1798 52130 I 529.0 1184 52390 573.0 1404 51725 617.0 1787 52055 529.5 1187 52245 573.5 1424 51730 617.5 1795 51950 530.0 1190 52140 574.0 1440 51725 618.0 1780 51850 530.5 1192 52235 574.5 1450 51730 618.5 1757 51740 531.0 1225 52210 575.0 1449 51720 619.0 1761 51670 531.5 1224 52455 575.5 1460 51720 619.5 1758 51625 I 532.0 1250 52395 576.0 1465 51710 620.0 1747 51545 532.5 1269 52225 576.5 1467 51700 620.5 1738 51585 533.0 1273 52125 577.0 1474 51700 621.0 1722 51585 533.5 1273 52175 577.5 1482 51700 621.5 1707 51575 534.0 1277 52355 578.0 1483 51690 622.0 1708 51525 534.5 1285 52290 578.5 1477 51690 622.5 1699 51485 535.0 1287 52195 579.0 1471 51710 623.0 1685 51465 I 535.5 1296 52090 579.5 1482 51730 623.5 1692 51465

536.0 1296 51995 580.0 1511 51755 624.0 1665 51465 536.5 1290 51895 580.5 1510 51725 624.5 1621 51465 537.0 1290 51840 581.0 1510 51745 625.0 1610 51390 537.5 1295 51780 581.5 1511 51760 625.5 1605 51325 1307 51765 582.0 51775 626.0 1591 51300 I 538.0 538.54 1320 51980 582.5 1509 51795 626.5 1566 51265 539.0 1288 51635 583.0 1502 51790 627.0 1562 51225 539.5 1278 51670 583.5 1503 51790 627.5 1564 51200

540.0 1277 51735 584.0 1511 51790 628.0 1561 51180 540.5 1279 51785 584.5 1520 51820 628.5 1556 51150 I 541.0 1278 51805 585.0 1528 51900 629.0 1546 51135 541.5 1278 51850 585.36 1544 51925 629.5 1531 51115 542.0 1281 51870 586.0 1544 51870 630.0 1517 51115 542.5 1283 51835 586.5 1544 51820 630.5 1509 51100 543.0 1285 51800 587.0 1546 51820 631.0 1504 51100 543.5 1282 51770 587.5 1558 51820 631.5 1497 51095 I 544.0 1281 51735 588.0 1572 51810 632.0 1483 51085 544.5 1279 51735 588.5 1587 51815 632.5 1475 51075 545.0 1281 51735 589.0 1611 51780 633.0 1468 51000 545.5 1279 51735 589.5 1620 51770 633.5 1467 51120 546.0 1285 51735 590.0 1620 51745 634.0 1465 51145 546.5 1286 51710 590.5 1620 51735 634.5 1459 51180 547.0 1285 51690 591.0 1623 51720 635.0 1452 51220 I 547.5 1284 51665 591.5 1628 51720 635.5 1445 51260

548.0 1275 51635 592.0 1625 51715 636.0 1434 51315 548.5 1268 51615 592.5 1629 51710 636.5 1432 51360 549.0 1261 51645 593.0 1630 51695 637.0 1431 51370 549.5 1252 51680 593.5 1632 51675 637.5 1426 51370 550.0 1251 51745 594.0 1634 51670 638.0 1422 51350 I 550.5 1255 51770 594.5 1644 51670 638.5 1419 51320 551.0 1253 51775 595.0 1656 51640 639.0 1409 51290 551.5 1254 51805 595.5 1665 51625 639.5 1412 51255

552.0 1266 51815 596.0 1663 51585 640.0 1415 51215 552.5 1280 51790 596.5 1670 51570 640.5 1417 51175 553.0 1297 51890 597.0 1679 51565 641.0 1414 51135 I 553.5 1308 52030 597.5 1683 51555 641.5 1408 51110 554.0 1333 52015 598.0 1683 51575 642.0 1400 51080 554.5 1353 52000 598.5 1693 51580 642.5 1398 51070 555.0 1368 51060 599.0 1702 51595 643.0 1395 51065 555.5 1384 51905 599.5 1707 51615 643.5 1398 51075 I I I -81-

TABLE B (con't)

Total Magnetic Total Magnetic Total Magnetic Station Elevation Intensity Intensity Station Elevation Intensity Station Elevation 50825 Y 50505 y 1394 m 51095 5 688.0 1132 a 732.0 1575 m 644.0 50825 732.5 1599 50420 1380 51125 688.5 1134 644.5 50845 733.0 1620 50365 1372 51140 689.0 1136 645.0 50875 733.5 1640 50395 1334 51185 689.5 1134 645.5 50930 734.0 1657 50260 1334 51190 690.0 1133 646.0 50950 734.5 1664 50235 1336 51170 690.5 1125 646.5 691.0 1120 50945 735.0 1671 50220 647.0 1338 51140 691.5 1121 50925 735.5 1678 50210 647.5 1330 51145 692.0 1112 50865 736.0 1680 50200 648.0 1328 51190 692.5 1115 50825 736.5 1676 50205 648.5 1307 51270 693.0 1118 50720 737.0 1688 50225 649.0 1307 51265 693.5 1112 50680 737.5 1693 50225 6495 1311 51225 694.0 1107 50640 738.0 1692 50245 650.0 1313 51210 694.5 1098 50600 738.5 1697 50255 650.5 1315 51205 695.0 1094 50600 739.0 1698 50275 651.0 1318 51230 695.5 1091 50595 739.5 1700 50275 651.5 1322 51250 696.0 1082 50690 740.0 1711 50280 652.0 1323 51260 696.5 1083 50775 740.5 1720 50285 652.5 1321 51265 697.0 1076 50830 741.0 1726 50290 653.0 1324 51260 697.5 1058 50845 741.5 1735 50295 653.5 1323 51265 698.0 1039 50880 742.0 1743 50290 654.0 1320 51285 698.5 1039 50880 742.5 1753 50295 654.5 1318 51330 699.0 1041 50865 743.0 1763 50285 655.0 1314 51330 699.5 1042 50825 743.5 1766 50300 655.5 1312 51285 50320 51240 700.0 1045 50785 744.0 1766 656.0 1309 50360 51195 700.5 1045 50720 744.5 1773 656.5 1308 50375 51135 701.1 1092 50700 745.0 1773 657.0 1302 50395 51100 701.5 1108 50695 745.5 1773 657.5 1298 50395 51085 702.0 1116 50695 746.0 1792 658.0 1296 50390 51080 702.5 1117 50675 746.5 1806 658.5 1283 747.0 1821 50375 51070 703.0 1114 50655 659.0 1274 50370 703.5 1112 50665 747.5 1824 659.5 1270 51040 1828 50365 51025 704.0 1131 50680 748.0 660.0 1266 50385 51030 704.5 1148 50700 748.5 1838 660.5 1270 50405 51020 705.0 1154 50705 749.0 1848 661.0 1276 50425 705.5 1152 50790 749.5 1853 661.5 1280 51010 50465 706.0 1152 50900 750.0 1852 662.0 1275 51010 706.5 1156 51005 750.5 1861 50495 662.5 1271 51010 707.0 1166 51090 751.0 1861 50490 663.0 1264 51005 707.5 1168 51220 751.5 1944 50430 663.5 1252 51005 51255 752.0 1925 50405 1248 51000 708.0 1174 664.0 51350 752.5 1931 50390 1245 51005 708.5 1183 664.5 1917 50395 51010 709.0 1189 51450 753.0 665.0 1239 50410 51030 709.1 51460 753.5 1931 665.5 1238 50460 51030 710.0 1189 51265 754.0 1952 666.0 1232 50480 710.5 1188 51050 754.5 1955 666.5 1236 51030 50490 711.0 1191 50885 755.0 1958 667.0 1225 51035 50480 711.5 1193 50805 755.5 1965 667.5 1221 51040 1974 50460 51045 712.0 1208 50790 756.0 668.0 1215 1980 50450 51060 712.5 1234 50830 756.5 668.5 1208 757.0 1978 50445 51090 713.0 1243 50810 669.0 1206 1982 50485 51105 713.5 1246 50840 757.5 669.5 1201 1999 50540 51110 714.0 1261 50880 758.0 670.0 1198 2018 50600 51125 714.5 1275 50870 758.5 670.5 1190 50695 715.0 1279 50865 759.0 2013 671.0 1184 51135 50785 715.5 1288 50870 759.5 2028 671.5 1182 51140 50880 716.0 1288 50925 760.0 2036 672.0 1177 51165 50860 716.5 1293 50965 760.5 2067 672.5 1179 51185 50710 717.0 1295 51020 761.0 2076 673.0 1178 51190 50650 717.5 1311 51070 761.5 2082 673.5 1167 51195 50705 718.0 1318 51125 762.0 2090 674.0 1149 51160 50885 718.5 1323 51200 762.5 2079 674.5 1150 51080 50825 719.0 1349 51190 763.0 2095 675.0 1152 51010 50655 719.5 1356 51125 763.5 2119 675.5 1150 50955 50585 720.0 1354 51055 764.0 2120 676.0 1153 50910 50555 720.5 1366 50980 764.5 2137 676.5 1155 50895 721.0 1373 50920 765.0 2147 50490 677.0 1147 50885 50480 721.5 1380 50875 765.5 2155 677.5 1149 50885 50510 722.0 1392 50905 766.0 2155 678.0 1133 50880 50525 722.5 1416 50925 766.5 2163 678.5 1131 50880 50515 723.0 1427 50905 767.0 2176 679.0 1129 50870 50515 723.5 1436 50845 767.5 2174 679.5 1127 50865 50495 724.0 1442 50785 768.0 2185 680.0 1132 50830 50495 724.5 1455 50720 768.4 2186 680.5 1139 50835 50520 725.0 1462 50690 769.0 2189 681.0 1139 50820 50530 725.5 1461 50675 769.5 2198 681.5 1142 50800 50530 726.0 1471 50675 770.0 2211 682.0 1144 50780 50570 726.5 1476 50675 770.5 2201 682.5 1143 50770 2225 50500 727.0 1472 50655 771.0 683.0 1144 50755 2243 50625 727.5 1475 50620 771.5 683.5 1134 50765 50635 728.0 1488 50590 772.0 2256 1128 50735 50625 684.5 1122 50720 728.5 1502 50615 772.5 2262 2268 50575 685.0 1119 50825 729.0 1539 50655 773.0 2278 50525 685.5 1118 50830 729.5 1570 50685 773.5 2283 50490 686.0 1120 50825 730.0 1583 50695 774.0 2278 50470 686.5 1122 50825 730.7 1581 50670 774. 5 50430 687.0 1125 50840 731.0 1586 50635 775.0 2273 50425 687.5 1131 50830 731.5 1566 50560 775.5 2272 I -82-

TABLE B (con't) I Total Magnetic Total Magnetic Total Magnetic Btation Elevation Intensity Station Elevation Intensity Station Elevation Intensity

776.0 2269 m 50455 y 828.0 1800 m 51500 f 872.0 1562 m 51495 Y 776.5 2271 50500 828.5 1802 51550 872.5 1553 51500 777.0 2271 50535 829.0 1807 51595 873.0 1494 51490 I 777.5 2273 50570 829.5 1803 51655 873.7 1490 51505 778.0 2272 50610 830.0 1781 51555 874.0 1497 51525 778.5 2276 50655 830.5 1766 51435 874.5 1489 51545 779.0 2286 50690 831.0 1760 51415 875.0 1465 51550 779.5 2290 50700 831.5 1747 51395 875.5 1456 51575 780.0 2288 50720 832.0 1738 51370 876.0 1449 51585 I 780.5 2283 50740 832.5 1731 51335 876.5 1440 51625 781.0 2280 50760 833.0 1721 51295 877.0 1438 51635 781.5 2277 50760 833 9 1712 51265 877.5 1428 51640 782.0 2277 50760 834.0 1700 51245 878.0 1423 51640 782.5 2280 50770 834.5 1692 51220 878.5 1416 51660 783.0 2282 50805 835.0 1689 51220 879.0 1408 51660 783.5 2284 50805 835.5 1685 51220 879.5 1407 51640 I 784.0 2282 50775 836.0 1679 51225 880.0 1399 51630 784.5 2281 50730 836.5 1680 51235 880.5 1397 51630 785.0 2274 50705 837.0 1682 51265 881.0 1395 51635 785.5 2271 50730 837.5 1681 51285 881.5 1390 51635 786.0 2265 50785 838.0 1686 51325 882.0 1381 51655 786.5 2258 50855 838.5 1697 51365 882.5 1377 51670 I 787.0 2250 50880 839.0 1706 51410 883.0 1372 51670 787.5 2243 50880 839.5 1717 51520 883.5 1366 51690

788.0 2238 50850 840.0 1721 51540 884.0 1354 51720 788.5 2233 50825 840.5 1733 51575 884.5 1349 51765 789.0 2228 50815 841.0 1743 51495 885.0 1343 51795 789.5 2227 50815 841.5 1749 51515 885.5 1342 51825 I 790.0 2225 50800 842.0 1752 51570 886.0 1338 51855 790.5 2220 50745 842.5 1750 51550 886.5 1336 51865 791.0 2203 50690 843.0 1748 51720 887.1 1356 51825 791.5 2202 50630 843.5 1734 51820 887.5 1363 51820

792.0 2210 50590 844.0 1724 51840 888.0 1356 51820 792.5 2206 50570 844.5 1704 51930 888.5 1361 51870 I 793.0 2193 50570 845.0 1683 51800 889.0 1373 51865 793.5 2189 50600 845.5 1683 51750 889.5 1396 51865 794.0 2184 50610 846.0 1675 51720 890.0 1398 51915 794.5 2175 50635 846.5 1665 51755 890.5 1421 51950 795.0 2158 50640 847.0 1658 51810 891.0 1441 51985 795.5 2154 50640 847.5 1651 51880 891.5 1451 52040 I 796.0 2150 50660 848.0 51910 892.0 1462 52095 799.1 2119 50700 848.5 1651 52080 892.5 1436 51935 802.04 2113 50870 849.0 1644 51830 893.0 1371 51925 805.51 2063 51090 849.5 1637 51500 893.5 1326 52145 850.0 1647 894.0 1294 52125 808.09 2029 51060 850.4 1649 51620 894.5 1284 51925 808.50 2023 51020 851.0 1638 51500 895.0 1278 51855 I 809.18 2016 50970 851.5 1644 51550 895.5 1278 51800 809.5 2009 50890 810.0 2000 50865 852.0 1653 52035 896.0 1272 51800 810.5 1994 50900 852.5 1656 52190 896.5 1303 51900 811.0 1986 50950 853.0 1660 52170 897.0 1316 52115 811.5 1975 50935 853.5 1674 52010 897.5 1353 51940 854.0 1678 51945 898.0 1368 51820 I 812.0 1978 50915 854.5 1686 51930 898.5 1372 51970 812.5 1976 50940 855.0 1699 51970 899.0 1370 52225 813.0 1978 50975 855.5 1706 51975 899.5 1354 52015 813.5 1978 51010 814.0 1979 51050 856.0 1705 52095 900.0 1350 51875 814.5 1975 51080 856.5 1726 52025 900.5 1340 51995 815.0 1968 51090 857.0 1725 52055 901.0 1342 52070 I 815.5 1970 51125 857.5 1720 51895 901.5 1326 52040 858.0 1716 51705 902.0 1301 51780 816.0 1969 51145 858.5 1709 51675 902.5 1294 51720 816.5 1960 51150 859.0 1677 51675 903.0 1292 51775 817.0 1938 51130 859.5 1668 51625 903.5 1299 51885 817.5 1927 51045 818.0 1916 51045 860.0 1644 51575 904.0 1313 51955 I 818.5 51065 860.5 1636 51515 904.5 1324 51975 819.0 1892 51110 861.0 1628 51475 905.0 1339 52240 819.5 1893 51165 861.5 1624 51455 905.5 1350 52845 862.0 1622 51435 906.0 1337 52380 820.0 1896 51245 862.5 1619 51420 906.5 1324 52365 820.5 1889 51490 863.0 1620 51420 907.0 1283 52010 821.0 1869 51510 1622 907.5 1263 51745 I 863.5 51440 821.5 1864 51510 864.0 1623 51430 822.0 1853 51375 864.5 1615 51450 908.0 1253 51640 822.5 1848 51240 865.0 1611 51500 908.5 1247 51690 823.0 1848 51215 865.5 1615 51530 909.0 1235 51745 823.5 1838 51260 866.0 1615 51575 909.5 1225 51785 866.5 1596 51645 910.0 1210 51800 824.0 1821 51285 867.0 1585 51725 910.5 1203 51820 I 824.5 1817 51325 867.5 1584 51825 911.0 1197 51825 825.0 1816 51350 911.5 1188 51850 825.5 1809 51370 868.0 1584 51955 912.0 1175 51865 826.0 1807 51390 868.5 1594 52020 912.5 1171 51865 826.5 i804 51410 869.0 1588 52005 913.0 1166 51865 827.0 1798 51435 869.5 1593 51890 913.5 1162 51865 827.5 1796 51455 870.0 1580 51760 I 914.0 1160 51865 870.6 1549 51655 914.5 1146 51870 871.0 1545 51575 915.0 1119 51860 871.6 1540 51520 915.5 1112 51860 I I I TABLE B3(con't)

Total Magnetic Total Magnetic Total Magnetic Stat ion Elevation Intensity Station Elevat ion Intensity Station Elevation Intensity

916.0 1106 m 51870 r 962.0 593 52395 y 1008.0 520 m 52545 v 916.5 1099 51910 962.5 594 52415 1008.5 519 52515 917.0 1090 51940 963.0 597 52425 1009.0 525 52545 917.5 1087 51960 963.5 595 52445 1009.5 522 52565 918.0 1090 51980 1010.0 510 52600 918.5 1088 51990 964.0 592 52465 1010.5 499 52645 919.0 1077 51995 964.5 586 52480 1011.0 496 52680 919.5 1082 52010 965.0 581 52470 1011.5 500 52710 965.5 578 52470 920.0 1081 52030 966.0 578 52460 1012.0 507 52730 920.5 1052 52045 966.5 580 52460 1012.5 508 52750 921.0 1014 52050 967.0 580 52435 1013.0 499 52775 921.5 994 52055 967.5 578 52455 1013.5 487 52810 922.0 967 52015 1014.0 485 52815 922.5 946 51995 968.0 573 52465 1014.5 484 52845 923.0 945 52010 968.5 570 52470 1015.0 492 52855 923.5 943 52025 969.0 564 52475 1015.5 493 52865 969.5 556 52475 924.0 939 52040 970.0 550 52475 1016.0 485 52885 924.5 922 52050 970.5 549 52475 1016.5 475 52920 925.0 923 52055 971.0 550 52465 1017.0 465 52980 925.5 916 52050 971.5 550 52455 1017.5 466 53060 926.0 904 52045 1018.0 457 53140 926.5 895 52060 972.0 542 52445 1018.5 450 53220 927.0 889 52070 972.5 536 52440 1019.0 448 53270 927.5 881 52100 973.0 533 52440 1019.5 447 53330 973.5 532 52440 928.0 872 52110 974.0 528 52440 1020.0 439 53360 928.5 864 52130 974.5 528 52440 1020.5 439 53405 929.0 859 52115 975.0 526 52465 1021.0 436 53405 929.5 855 52085 975.5 530 52465 1021.5 432 53385 930.0 852 52075 1022.0 431 53370 930.5 850 52055 976.0 524 52480 1022.5 430 53330 931.0 849 52055 976.5 533 52510 1023.0 429 53275 931.5 850 52045 977.0 546 52540 1023.5 429 53225 977.5 547 52560 932.0 842 52045 978.0 546 52575 1024.0 427 53135 932.5 839 52055 978.5 544 52595 1024.5 430 53075 933.0 828 52060 979.0 553 52620 1025.0 431 52975 933.5 828 52065 979.5 566 52645 1025.5 430 52905 934.0 827 52075 1026.0 434 52835 934.5 828 52085 980.0 583 52595 1026.5 433 52785 935.0 820 52105 980.6 585 1027.0 432 52725 935.5 812 52115 981.0 590 52685 1027.5 431 52695 981.5 592 5271.0 936.0 815 52115 982.0 591 52750 1028.0 438 52675 936.5 817 52130 982.5 590 52765 1028.5 443 52645 937.0 809 52150 983.0 588 52825 1029.0 449 52635 937.5 806 52170 983.5 583 52885 1029.5 452 52615 938.0 805 52165 1030.0 455 52615 938.5 797 52170 984.0 584 52935 1030.5 457 52605 939.0 793 52185 984.5 576 52990 1031.0 455 52600 939.5 783 52200 985.0 564 53055 1031.5 458 52600 985.5 548 53145 940.0 777 52205 986.0 532 53220 1032.0 453 52600 940.6 761 52220 986.5 515 53300 1032.5 458 52610 941.0 736 22240 987.0 498 53375 1033.0 457 52600 941.5 750 52255 987.5 483 53445 1033.5 456 52595 942.0 759 52275 1034.0 455 52590 942.5 736 52315 988.0 472 53460 1034.5 451 52600 943.0 738 52375 988.5 469 53445 1035.0 449 52605 943.5 733 52400 989.0 474 53395 1035.5 446 52610 989.5 482 53325 944.0 712 52400 990.0 482 53250 1036.0 445 52610 944.5 706 52350 990.5 482 53165 1036.5 441 52610 945.0 691 52390 991.0 481 53090 1037.0 441 52610 945.6 677 52235 991.5 482 53010 1037.5 442 52580 946.5 681 52270 1038.0 445 52600 947.0 675 52280 992.0 486 52935 1038.5 445 52605 947.5 682 52290 992.5 492 52870 1039.0 445 52605 993.0 500 52825 1039.5 445 52615 948.0 674 52255 993.5 504 52800 948.5 672 52280 994.0 506 52785 1040.0 445 52615 949.0 672 52295 994.5 508 52765 1040.5 446 52630 949.5 669 52295 995.0 508 52750 1041.0 450 52640 950.0 663 52295 995.5 509 52745 1041.5 451 52660 950.5 662 52295 1042.0 453 52665 951.0 658 52295 996.0 507 52730 1042.5 449 52675 951.5 648 52300 996.5 507 52720 1043.0 447 52695 997.0 505 52720 1043.5 449 52700 952.0 654 52300 997.5 503 52720 952.5 650 52310 998.0 503 52715 1044.0 450 52720 953.0 644 52320 998.5 502 52715 1044.5 451 52730 953.5 639 52325 999.0 500 52695 1045.0 451 52740 954.0 634 52335 999.5 503 52685 1045.5 451 52750 954.5 628 52345 1046.0 457 52760 955.0 620 52345 1000.0 500 52655 1046.5 454 52780 955.5 617 52345 1000.5 501 52615 1047.0 453 52785 1001.0 501 52600 1047.5 441 52795 956.0 615 52350 1001.5 500 52590 956.5 616 52350 1002.0 500 52580 1048.0 441 52815 957.0 615 52350 1002.5 499 52580 1048.5 442 52840 957.5 615 52360 1003.0 495 52565 1049.0 441 52860 958.0 615 52370 1003.5 494 52560 1049.5 444 52890 958.5 615 52370 1050.0 452 52910 959.0 611 52370 1004.0 497 52565 1050.5 .454 52930 959.5 609 52370 1004.5 503 52565 1051.0 459 52950 1005.0 505 52565 1051.5 453 52985 960.0 604 52370 1005.5 510 52565 960.5 602 52375 1006.0 515 52555 1052.0 450 53015 961.0 596 52385 1006.5 519 52545 1052 .7 452 53050 961.5 592 52385 1007.0 518 52545 (Eights 1007.5 520 52545 Station) I

TABLE C DISTANCE, VELOCITY AND DEPTH U From Seismograms Station 224 Station 320 (con't) Station 404 (con't)

Distance From V Distance From Vp Distance From p VP Shot Point Depth Shot Point Depth Shot Point Depth I 60 m 2305 m/sec 10 m 190 m 3125 m/sec 43 m 310 m 3571 m/sec 70 m 90 2607 18 220 3279 50 330 3767 82 120 2740 24 250 3383 57 Station 432 150 2765 26 280 3493 64 180 2959 35 310 3576 70 I 60 m 2073 m/sec 8m 210 3005 39 330 3682 77 90 2200 14 240 3053 43 120 2864 29 Station 352 270 3113 48 150 3080 38 Inm 300 3152 53 10 1300 m/sec 180 3216 44 I 3 330 3176 56 15 1495 210 3272 48 20 1670 4 240 3320 51 Station 256 25 1875 6 270 3352 54 10 m 1280 m/sec in 30 2000 7 300 3380 57 15 1520 3 40 2180 9 330 3416 61 I 2 1740 5 50 2270 11 360 3425 63 25 1900 6 60 2355 12 390 3433 64 30 2005 7 70 2420 15 420 3477 70 40 2145 9 100 2600 19 450 3504 75 I 50 2260 10 130 2755 25 480 3567 83 60 2330 13 160 2880 31 510 3592 87 70 2390 15 190 3000 36 540 3600 89 100 2575 19 220 3115 43 600 3625 93 130 2735 25 250 3210 49 660 3640 97 I 160 2895 32 280 3305 56 720 3672 105 190 3035 39 310 3385 62 780 3704 114 220 3150 45 330 3460 68 840 3725 120 250 3250 52 900 3748 127 Station 382 280 3345 59 960 3769 134 I 310 3435 66 10 1216 m/sec 1 1020 3788 141 2 330 3505 71 15 1323 1080 3792 143 20 1425 3 1140 3795 145 Station 288 25 1518 4 1200 3800 148 I 10 m 1365 m/sec 2 m 30 1620 6 1260 3820 158 15 1640 3 40 1800 8 Station 464 20 1805 4 50 1975 12 25 2105 7 60 2148 15 10 - 1160 m/sec 2 n 30 2210 8 70 2285 18 15 1380 3 I 40 2350 9 100 2720 25 20 1575 5 50 2450 11 130 3020 34 25 1740 6 60 2500 13 160 3245 42 30 1880 8 70 2535 14 190 3415 49 40 2120 10 100 2655 17 220 3525 I 55 50 2335 14 130 2775 22 250 3620 60 60 2505 17 160 2895 28 280 3684 65 70 2660 19 190 3005 35 310 3730 69 100 3015 25 220 3120 41 330 3751 71 130 3220 32 I 250 3246 48 160 3360 36 Station 404 280 3355 57 190 3465 41 310 3470 64 15 1588 m/sec 1 m 220 3540 46 330 3585 73 20 1629 2 250 3600 50 3 25 1702 280 3650 54 I Station 320 -30 1760 4 310 3690 58 2 10 m 1512 m/sec 40 1908 0 330 3710 60 20 1611 3 50 2002 8 25 1730 4 60 2071 10 Station 496 I 30 1846 6 -70 2242 14 10 i 1380 m/sec i m 40 1902 7 100 2455 19 15 1565 2 50 1952 8 130 643 ?o 20 1710 3 2229 60 13 150 2962 3b 25 1835 4 70 2367 17 180 3159 44 30 1940 5 I 10 2500 20 220 3289 5l 40 2115 130 2832 29 250 3389 57 50 2260 10 160 3013 37 280 3431 ol 60 2380 13 I I I -85-

TABLE C (con't)

Station 496 (con't) Station 604 (con't) Station 700 (con't)

DistanceShot Point From Vpp Depth Distance From V Distance From Shot Point p Depth Shot Point p Depth 960 m 3884 m/sec 70 m 2470 m/sec 15 m 540 n 3608 m/sec 81 m 131 m 100 2685 19 600 3654 90 1020 3891 134 130 2870 26 660 3705 100 Station 732 160 3040 33 720 3793 116 190 3200 40 780 3840 126 10 M 1420 m/sec im 220 3330 47 15 1535 2 Station 636 250 3455 54 20 1640 3 2 m 280 3560 60 10 m 1125 m/sec 25 1730 4 310 3660 67 15 1340 3 30 1810 5 330 3725 74 20 1535 5 40 1960 7 6 25 1700 50 2095 9 Station 528 30 1855 8 60 2210 12 14 10 m 1618 m/sec 3 m 40 2110 10 70 2310 15 1848 4 50 2335 13 100 2545 19 20 2068 5.7 60 2470 16 130 2720 26 25 2130 6.4 70 2590 18 160 2860 32 30 2292 8 100 2790 22 190 2975 38

40 2518 10 130 2905 27 220 3075 44 50 2542 11 160 3000 31 250 3160 50 60 2590 12 190 3085 37 280 3245 56 70 2688 15 220 3165 42 310 3320 62 100 2866 19 250 3240 48 330 3395 69 130 2972 24 280 3310 53 Station 764 160 3020 27 310 3380 59 190 3064 30 330 3420 62 10 m 1380 m/sec im 220 3148 36 15 1515 2 Station 668 250 3228 42 20 1630 3 280 3316 49 10 s 1370 m/sec im 25 1740 5 310 3342 50 20 1715 3 30 1830 6 25 1840 4 40 2005 8 Station 572 30 1945 5 50 2145 10 7 10 m 1320 m/sec I m 40 2130 60 2280 13 15 1510 3 50 2280 10 70 2375 15 20 1685 4 60 2400 13 100 2615 20 25 1870 6 70 2500 15 130 2760 26 30 2040 7 100 2740 19 160 2855 31 40 2390 10 130 2895 25 190 2915 35 50 2630 13 160 3005 31 220 2950 38 60 2800 16 190 3100 36 250 2975 42 70 2920 18 220 3205 42 280 2980 43 100 3180 22 250 3305 49 310 2985 45 130 3350 28 280 3410 56 330 2990 46 160 3490 33 310 3520 63 Station 796 190 3605 39 330 3600 70 220 3710 44 60 n 2373 m/sec 10 m Station 700 250 3800 50 90 2564 17 280 3860 54 60 m 2255 m/sec 7m 120 2933 26 310 3900 58 90 2488 14 150 3033 32 330 3920 60 120 2720 22 180 3185 38 Crevasses underlying shot point and spread. 150 2897 29 210 3231 42 180 3086 37 240 3281 46 Station 604 210 3163 42 270 3333 50 60 m 2375 m/sec 9 m 240 3331 51 300 3400 56 90 2541 15 270 3472 59 330 3440 6O 120 2760 22 300 3560 65 360 3467 65 150 2971 30 360 3624 70 390 3520 69 180 3135 37 420 3633 73 420 3542 73 210 3240 43 480 3650 77 450 3576 77 240 3341 50 540 3683 83 480 3608 81 270 3384 53 600 3727 92 510 3727 95 I300 3438 57 660 3790 104 540 3742 98 330 3472 60 720 3837 114 570 3758 101

360 3504 64 780 3854 119 600 3805 108

420 3520 67 040 3866 123 660 3825 111 I480 3584 76 900 3876 127 720 3843 -86- I

TABLE C (con't) I Station 796 (con't) Station 908 (con't) Station 1028

Distance From V Distance From v Distance From Shot Point P Depth Shot Point Vp Depth Shot Point Depth 118 m 15 m 780 0 3852 m/sec 1020 m 3825 m/sec 127 m 1320 m/sec 2 m I 900 3870 125 1080 3845 135 25 1450 3 30 1515 4 Station 840 Station 940 40 1660 6 10 1220 m/sec 1 m 10 m 1040 m/sec 2 m 50 1825 9 15 1425 3 15 1305 4 60 1995 13 I 20 1610 4 20 1540 6 70 2166 16 25 1770 8 6 25 1730 100 2697 25 7 30 1910 30 1905 10 130 3110 35 2170 40 10 40 2200 12 160 3330 43 50 2380 13 50 2460 I 16 190 3430 48 2560 60 16 60 2665 19 220 3476 52 70 2695 19 70 2850 22 258 3515 55 100 2955 23 100 3240 27 280 3580 60 130 3135 29 130 3400 33 310 3665 66 I 160 3280 35 160 3440 36 330 3720 71 190 3385 41 190 3460 38 220 3485 46 220 3475 40 250 3565 52 250 3485 42 280 3640 57 280 3490 43 I 310 3710 62 310 3500 45 330 3745 66 330 3510 47

Station 864 Station 976

1m I 10 m 1360 m/sec 15 m 1940 m/sec im 2 15 1540 20 2000 2 20 1710 4 25 2055 3 25 1855 5 30 2105 4 7 40 3M 1990 2200 5 I 40 2230 9 50 2290 7 50 2420 12 60 2360 9 60 2580 15 70 2435 11 70 2715 18 100 2630 15 100 3015 22 130 2785 22 U 130 3220 29 160 2925 28 160 3360 35 190 3050 35 190 3470 40 220 3170 42 220 3555 46 250 3286 49 I 250 3625 50 280 3390 56 280 3680 54 310 3495 63 310 3730 59 330 3535 67 330 3760 62 Station 1008 I Station 908 10 0 1405 m/sec inm 60 a 2443 m/see S0 15 1555 2 90 2804 20 20 1680 4 120 3042 28 25 1795 15 150 3259 I 35 30 1890 6 180 3350 40 40 2065 8 210 3398 43 50 2220 240 3461 48 60 2350 14 270 3487 50 70 2465 16 I 35 300 3523 54 100 2730 21 360 3581 60 130 2940 28 420 3594 63 160 3120 35 480 3607 66 190 3275 43 540 3651 75 220 3415 49 I 600 3694 84 250 3550 57 660 3712 89 280 3675 64 720 3738 99 310 3825 72 780 3761 103 330 3860 108 I 840 3775 900 3793 114 960 3815 122 I I I -87-

APPENDIX II

REPRODUCTIONS OF SEISMOGRAMS

Portions of representative seismograms are presented for each reflection station. The geophone separation is 30.5 m. Timing lines are 0.01 sec apart. Gain is in lO-db steps, with maximum gain (10) at the level where instrument noise becomes apparent. The notation for each record is: station number, charge weight, depth, gain, frequency passband, and remarks. Dual refers to a 12-geophone, 24-trace record; the output of each geophone is recorded on two traces. Traces I and 13, 2 and 14, etc., correspond to the same geophone. (See Table I for travel times.) 5 / r\ 7> 6 .7 'I \ A '-N VN ~Ad \J / v K V V

\ 'N A IN ,, \~ V K

I ~ 'A K-, 'A ., T_/\\! (N A V K."

V \\J. I> ~2V> I> V V "p - V I At K 224.2 11 Dec. 1961 'V 500 g 4 m sprung hole A Gain 1-12:8, 13-24:7 / K.' K K A 215 cps 'V low pass V V p.; L spread, shot point 15 m A & from #12 and #13 'K' NJ V & V K.' I0 V v 'K' "V A f\J k-I f\f J.v f'~'p -----y V V 44 VIV,VN

& / A /V A 'V

ooo K.'

"p (

'AK 0 V . ~V'. K- / AA V "V

- ~7N A

A. A '4 "A L,,

m m m m - - mmm m m I m SIi ' '

I--

° 'ii:l ] O%i jj"'

25. 162De. II. 1/ II ,.IK ,,- OOg 4m 1"e

I ' . / i 1 t l l q ! ,

,, .. I , J 'Al' "

IVV Ii, I ,I ' I' ,i , i I I ' i . I i " I,li I "Ii " ' I

256.1 196 12 De.

500 . m-.----~-.--.~ ______- -_ L,t!ii

' I" I -\ -...... I I- v a I ... = - , .. . - I -- v I I I - . 6 '17 8

A--- .- ...... 7-- ~~7N

w.of

A -I 7--

/ A '~N ,-- I -7- A A JN. A A A A I-N -N I-' -. J V -I Vi ..... V jlV - -2

i/ A- 1~ A ,f", vl v/ f~N V~ KgK/AJ \7N 1~ A -- 7- 7--- V '-7 vt-

7>~

A -A

!...... ,0 ...... 0 ...... 00......

- A

--- A- 288.1 15 Dec. 1961 500 g 4 m Gain 8, 215 cps low pass -N V

'N'- -'-A-- -I I - |- -

-t

- S I-

____ I - -

- - -m=m m m-s I - ~ ------m - - - - I--

T •w- ,.~tt ~.j- I.i: I. .1--- Ii 2

ne s Ak'AlA V 320.1 19 Dec. 1961 m 50Og '4 ~ ,~ ~ .. \'\t N Gain 8, 21.5 cps low pass 00, - In-line sp?read, even geophones #1, #13, verticalL, #5, #9, I ' It #17, and1 #21 horizontal 1. I' longitudlinal, others hori- ''-I. .1' zontal t:ransverse, #7 out 'A A' , 16m/sec wind

V^\

'tI ~

N.,' 14 ! r-.- 'A^ _- ,e,,A 14

...... '.V'~.'N~,.' -~,--I ' ~ ~pi I. 4-

-. ~1.".' 0./1~I II I I 106 iI 1 352.1 23 Dec. 1961 500 g 4 m Gain 8, 215 cps low pass L spread, shot point 15 m 'I'll--4 #12 and #13 from

I / I N 129 A~A~

IV/ A A Nj> A ~A. A A> N_

A A VJ\ V ~r\3 'A 7> p I

IN;

!Ml

v~ //~N 'V. VI

- /

2 A

4'R~ H

- - m m m m - - - I m m -m--m -m -m -- I I m

V *4 V '08 J

...... 382.1 26 Dec. 1961 -0~-r ------500 g 4 m Gain 9, 215 cps low pass Dual, shot point 15 m from #12

Axi' J "I TV-\ I /, A A I kIN1 'NV, A

P. A ~ A Az' I': Al v, V., 4" "N, I) I I , A ~ ( A WA vf A.'

} (fkI~A\\ V V A A II V Ar' Vi JA "C A, JA A A" AA A A, ~AA if., A 'A' ~AI I J I A A A' A"' F At\ * ~1~ 0' KQ> 'A ,, A K'. I & F 'V A' p IA. A, A (KA A/A '.1 [4 A A A, ./. w C' A ''.4 V/X2 A' A 'A V

I! 'I 'A .4-- ' WA 'A A' \-A -, Y AA A N ' A'. A A A A A, I V~IA A'

'A'.,

. r I ,, ! ' 1 I ' I . ! I ' -I' 1 !

I I fly --V I., (I V Y J V is ~-' 1.1 v J2 160 / -V t -I-N

A (I

(N Vt K' K,, ( V 4~KNk~IJVk~- VTh\ / V A / A / p ---" / A (/ (V~ (NV ~Nf\ A V 'I A (

I- V f y V V N \N A -I / I- \7

......

A V

A A!> -I-, V V' (

V V -7-> A 404.1 26 Dec. 1961 500 g 4 m Gain 1-12:9, 13-24:8 215 cps low pass A -I K Dual, shot point 15 m from #12. #5 and #7 out 4RIJ KA...... i

- m m -m--m m - - - I m m m m m - - - I m

.9 1.0 II' 1.2 (A A A ^ yA " iI

I A -A

.> AN A\

~vA\ A vv V

A VA V V -N An V V 0 '-N VyA I- A\ -v (N A '-A, N A / "! /

i r v , 1/ V' 'N'

A- A/ -v-Ag A : '

A A v' A H AA PA~ A.

432.2 28 Dec. 1961 500 g 4 m sprung Gain 9, 215 cps low pass In-line spread, #1-#12 geophones vertical, #13-#23 - odd geophones vertical, #14 - I- t- - and #22 horizontal transverse,- 1~~F~1 #12, #16, and #20 horizontal longitudinal, #18 out TIRJI jP1~e -1.__ I 1 1 1 I 1' I .1 .2 .3

I fv 'A -J V I> 'I / K & A' 'N-

A' 'V '-A ~ NA ,/ • .7 VN VA A-I PJK A'> (4, 4, p (N 'V /- p AJY JV

A-A/A K Aj A 'N -A-A \AI A"'' A, VA'' N .\A A As As AN/A-NA A,- 'I J 464.9 4 Jan. 1962 '-'NA/V A's V J >1-v., 70 g 4 m sprung / Gain 8, 120-320 cps passband -I-v L spread, shot point 15 m A" J4 "V/ from #12 and #13 A' V / V.0 ON

& VA/A •/1." V^

N A 'A % A' '-7' ' A/A A VA A A/V v/A\f\ A' *~ 'N V., K '

N A'\/Ai VJ 'A-A' A] A' 'V, A

,.A A'w A A> TA' A'/- ANAA 'v-A *~/A A., 1

AK* VI JA~ I

I -~'

- - -m - - I I m m -m -m-m- -I-m-m-=-m-I I =

- NJ-

-NJ $

NJ (N K/NY" vv/

N-' .NJ NP V ,/7N

~ A K'(N "V N-i 'N--'.'

'-NI

496.4 6 Jan. 1962 70 g 4 m sprung Gain 7, 90-215 cps passband , j 'NI ,NN Y>IN iir . L spread, shot point 15 m from #12 and #13 " " "/ ,I-

jK+~t .5 / / 604.2 11 Jan. 1962 500 g 4 m sprung Cain 1-12:9, 13-24:7; 1-12:215 cps low pass, 13-24:90-320 cps passband Dual, shot point at #12

AAAAN

A\VA

I 9/A' ('A I 41/ A' A/A, A/A' - A,A /IAAA'A

A/A A 4 Af r A' 'A' V (A N.

'VA I A, I'. N.!'

Co 'AA\

'AA~ ~ 'N' V "A"> IV

'N 7' A/f' I> 'NJ

~7N /~AAA~I ~~~JXA'

A\AfA'v yAA~AXA' AAYNA~ A/ AAAAAAA/A /N.A' NA~' w J\A/N

NA/A' V x

A A

N A/VN N AK ~A ~NA'N

IA I A AX 4-NA~%f /A~A *1 R 1 4L, I

- m w -mo - m - I Im m m m m m m m - - - I m

.I.- 1 .. I...... 1.. 1.I I I -

636.1 13 Jan. 1962 500 g 4 m Gain 1-12:7, 13-24:9; 90-215 cps passband Dual, shotpoint at #12

I I I I I I I I .8 ,,

--- 7

N , , N~7 -- N

--- -7-'--

7 '-N. 1~ //

C' ,7 >7

yNj

'---V v-NI

I ----..-.,- r . ..--- 7------~~1~

-7---

7-N \J

10"

- ' N-

iii7K K ------

lii I

668.1 14 Jan. 1962 500 g 4 m Cain 1-12!9, 13-24:8; 90-215 cps passband Dual, II RII I shot point at # 12 I I I I

- m -m ------I - m mm m - mmm m -m -m -mn _ m - -

-. 61 K .' 7 .8 .9

...-.. I -...

30 mfrm

- AI . ...- ...... ~L) ...... A K !0 1'j ......

A-/ - \ /' 4, 16 20 #1,-. K- Lnserse.V~\Afan.d.....2

A Z'IL ...... 'h 0 .2t r t l70

...... f ------. . ... --__- ..- ...... 1_16. . J an...

SOO 3 .7 .8

A\f~ A i "I.

!.l_ . I A K \,.. K If / IV NA/ II 1,,,.,.

A ~ , A / i.* AN A' I .,, V I, " ' . J AV V

A I '7. A'' A' (N J A A) !,( I/ IN J A-A & '>1 /.. i17 A' A IJ 1... .. 1 K ...i!I ...-A..... Ki_7 h V KK i Ln at #1I2 ~ & r'l 'A V' -!...... ] .!:l. "1.; --I;1 ; 2 V.1/ K.._

A'. Ai

& ANA AN yN S i I 1j Vi N,--

It'. /

500Og 4 m Gain 1-12: 9, 90-215 cps p Dual.,shot poi Jan 16 Iii 13-24:8;i N. " A ., I, I IAA

- - i -- , m m - - - I m - .- m- m- m - m - I- t m

.6 .8 Az

-/ NA K V

-I/ A 'V V/N, ', I V Y/ (7 A' /x,- IV/ ('I iN.

...... K! 2A A I' -N y/ A/ V / \ r_ ~7N I '; t V "V Ii , N.I. A /7 A I jN A . 1 JAN V ,^J ~~~>1 -iN V .

-I .. I.-I . .. . " 7N~~ N, 7N~ 7N~ /V N7~

-NV 1\Ak-'V~J '-N NXN

7N~

IN--- A "'/- A '~~\ (\ -AN A>' -A '1 ~>7

"1" 764.4 18Jan. 1962 500 g, 2 m /N !\ ' Gain 1-12:8, 13-24:7; 90-215 cps passband A' V IV V ., IV Dual, shot point at #12 S...... -1. 7,, -v I.

I,.

7-.,i V

796.1 19 Jan. 1962 500 g 2 m Gain 1-12:9, 13-24:7; 90-215 cps passband Dual, shot point 15 m from #12

TRIIK yd- 1 mJ fm m m ,_ m - - - -!m - m m m

.5 .6 I I .71

~.1

'N '-'N 1~

A ,~

N-, V,,

A i -'--'N"

-'N -N'-'

-- "N--'-

id " 4 - i- ~' -- '- wI I """m .f-r. . m.. .. - ,-'o...... " . .. .. - .---- . _: -, . . ., _ - -,...... - . , .,- . . . . .- - "- .. . .

808.1 29 Jan. 1 500 g 3 m Gain 1-12:8, 13-24 : 7;II 90-215 cps passbar Dual, shot point 30 #12 K.... ,I

'IN' .2 A I A .3.

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K 976.2 3 Feb. 1962 $500 g 3 m sprung Gain 9; 1-12: 36-320 cps passband, 13-24:90-215 cps passband Dual, shot point 15 m from #12

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