Deep Drilling on Midway Atoll GEOLOGICAL SURVEY PROFESSIONAL PAPER 680-A Deep Drilling on Midway Atoll By HARRY S. LADD, JOSHUA I. TRACEY, JR., and M. GRANT GROSS GEOLOGY OF THE MIDWAY AREA, HAWAIIAN ISLANDS GEOLOGICAL SURVEY PROFESSIONAL PAPER 680-A Two cores recovered from the reef cap and the basaltic foundation establish a Tertiary section for the Hawaiian Islands UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1 (paper cover) DEEP DRILLING ON MIDWAY ATOLL The windward reef, Kure. The irregular red-brown buttresses, composed of living algae, are bordered to seaward by irregular submarine grooves and ridges; the reef flat, built of corals and algae (right), extends toward the lagoon. CONTENTS Page Page Abstract._______________________________ Al Lithology of the sedimentary section________---_-_____ A8 Introduction. ___________________________ 1 Organic composition and age of the sedimentary section- 14 Regional relations ____________________ 2 Basaltic foundation.___________________-_--__---_-__ 18 Location. ___________________________ 4 Comparable reef drilling elsewhere.___________________ 18 Acknowledgments.----... ____________ 4 Geologic history of Midway_______-____-------_--_-_- 20 Equipment, supplies, and personnel._______ 5 References cited.______________-_____---_-_--_--_--_ 21 Operations----____-_--_______-__________ 7 Drilling. ____________________________ 7 Tests before, during, and after drilling-_ 7 ILLUSTRATIONS Frontispiece. The windward reef, Kure. f&ge PLATE 1. Bathymetric chart of Midway area_____--______--_--__________________________________________ In pocket FIGURE 1. Index map of the Hawaiian chain_____________________________________----____-_-_---_----_-______ A2 2. Map of the Pacific basin, showing major tectonic features-___-_-__-_-__---___-_______------_------_--__ 3 3. Photograph showing mass of living coral on floor of Midway lagoon._____-----__________--__-_-----_____ 4 4. Map of Midway atoll, showing location of drill holes.___-___________-______--_____--___-___------___-_ 4 5. Aerial photograph of Sand Island.________-___-___--______________--____------__---_-_-_-_-----__-__ 5 6. Photographs showing drilling preparations and operations______-___-__--_----..__--_-----------_---_-_-- 6 7. Logs of drill holes_____________________________________________-___-_---_____-__----_----_--_____ 9 8-17. Photographs showing cores from the Reef hole: 8. Reef limestone at 119 feet___________-____-_-_______-___-__--_-_-_--__-__--_---_---------_ 12 9. Fragmental limestone at 414 feet_------_---_--------------------------_---_----------------- 12 10. Dolomite at 474 feet_______________-_-_-_-_-___-_--__-_-----_-------___-_-_---------_---- 13 11. Dolomitic limestone breccia at 588 feet____-__--_______--___-______-________--___------..___-_ 13 12. Extensively leached limestone at 646 feet____________________________________________________ 14 13. Variegated limy dolomite at 914 feet_______________--____________-________-----__-_-_-_____ 14 14. Fragments of mollusk shells in clay at 987 feet__________________-----_______-_-_-_--__----____ 14 15. Light-gray tuffaceous limestone containing molds of corals and mollusks at 993 feet________^______ 15 16. Light-gray to medium-light-gray tuffaceous limestone containing molds and coral fragments at 1,030 feet-_______________________________________________________________________ 15 17. Dark clay containing bivalve shells at 1,046 feet______________________________________________ 16 18. Photographs showing cores from the Sand Island hole_________________________________________________ 17 19. Map showing sites of deep holes drilled on five atolls in the open Pacific Ocean.__________________________ 19 20. Graphic summary of results of deep drilling on five atolls in the open Pacific Ocean_______________________ 20 TABLES Page TABLE 1. Summary of depths, casing depth, and core recovery for two diamond drill holes_ A7 2. Major lithologic units of the Sand Island and Reef drill holes-________________ 8 3. Description of cores and cuttings from the Sand Island and Reef drill holes. _ 10 4. Data from deep drilling on five atolls in the open Pacific Ocean.______________ 19 in GEOLOGY OF THE MIDWAY AREA, HAWAIIAN ISLANDS DEEP DRILLING ON MIDWAY ATOLL By HARRY S. LADD, JOSHUA I. TRACEY, JR., and M. GRANT GROSS ABSTRACT could not find satisfactory descriptions of the small Two deep drill holes through reef limestones and underlying islands and reefs of Kure, then called Ocean Island. clays into basalts establish a geologic section for the Hawaiian This atoll was described by Couthouy (1842),-whose Islands that extends back through the Miocene. Chemical analy­ paper was also published in 1842, but Darwin had seen ses indicate that tholeiitic basalts were covered by flows of Couthouy's writings in a pamphlet sent to him earlier alkalic basalts, and aa and pahoehoe structures indicate that by Charles Lyell. Couthouy's description of the atoll the volcanic mound was built above the sea. The exposed part of the volcanic mound was partly truncated by wave action led Darwin to color Kure blue on his reef map, thus in pre-Miocene time, after which subsidence began. As the indicating subsidence; on the same map Darwin colored mound sank, weathered clays were reworked in shallow water the larger Hawaiian (Sandwich) Islands red to indicate and eventually were covered by reef limestones. Overall sub­ emergence. mergence was interrupted three or more times by emergence Dana (1843, p. 134-135) referred to the small rocky during the middle Miocene, at the end of the Miocene, and at and coral islets beyond the main islands of Hawaii. least once during the Pleistocene. During periods of emergence, the limestones were leached and recrystallized. The Miocene He noted that they evidently belonged to one series, limestone is irregularly dolomitized. This alteration may have adding, "I will not say that there is a connection between occurred at the time the lower part of the post-Miocene section the trend of these groups and the area of subsidence; was deposited and extensively dolomitized. The altered lime­ yet it looks much like it." In the larger islands he noted stones were covered by 200 feet of younger reef limestones. The last-recorded event was the growth of a now emergent reef, that igneous eruptions became more recent toward the eroded remnants of which are found on most of Midway's southeast. Dana expressed the opinion that subsidence rim. was no longer in progress and suggested that it may INTRODUCTION have taken place in the latter part of the Tertiary and Midway atoll and its neighbor Kure lie at the north­ succeeding ages. Later, in his main report as geologist west end of the Hawaiian chain, which stretches for for the United States Exploring Expedition under more than 1,600 miles across the central Pacific (fig. 1). Charles Wilkes, Dana (1849, p. 280) stated that the The entire chain can be conveniently divided into three Hawaiian eruptions might date as far back as "the early major subdivisions according to the type of island found carboniferous or Silurian epoch," but he never stated in each (Palmer, 1927, p. 5). The southeast segment what he considered evidence for this conclusion, as far includes the large volcanic islands and their associated as we can determine. In this same report Dana noted small islets. The middle segment includes several shoals, (p. 396-397) that the western islands were coral islands, in addition to small islands, on which volcanic rock is indicating participation in subsidence, and concluded exposed. The northwest segment stretches over a greater that the change of level was greatest at the west ex­ distance than the other two and includes a dozen or more tremity of the Hawaiian chain. Dana also referred shoals and reefs; some of these reefs, like Midway and (1849, p. 282-283) to a manuscript by Couthouy in Kure, have low-lying carbonate-sand islets, but no vol­ which that author recognized that the progress of vol­ canic material is exposed. cano extinction in the Hawaiian chain was from the This overall distribution of high-altitude volcanic west to the southwest. rocks and sea-level reefs impressed early observers, and Geologists working later in the Hawaiian Islands significant interpretations resulted. Charles Darwin have found no reason to question the general theory of (1842), in his volume on coral reefs, referred to the progressive volcanism and subsidence from northwest smaller islands and reefs that form the northwest seg­ to southeast. They have recognized, as did Dana (1849, ment (p. 158-159). Darwin had not visited the area and p. 281), that the chain is not a single line of vents but Al A2 GEOLOGY OF THE MIDWAY AREA, HAWAIIAN ISLANDS )0° >5° 30° 1 75° 1 70° If3 5° 16 IE 30"It y iff Us o n Midway Is Kure ° /(Ocean 1) "I 1j Pearl and B *MIDWAY ^ Hermes Ree ^lg ' °<, Lisianski 1 / Lc 0 0 0 Laysan 1 reefs8g 0'c*n,c /Gardner 'Pinnacles a/s / French / r* Frigate / ^ QShoals TROPIC OF CANCER oNeckerl / Nihoa./ >v/ 55 Ka ua i '''c r ^ / Niihaun ^ Kaula" Oahu^fc Molokai (^3 ^. Lanai jllp 20° Hawaiillp // 100 200 300 400 500 MILES FIGURE 1. The Hawaiian chain, showing the three major physiographic subdivisions (bounded by dashed lines). Modified from Palmer (1927). that there are transverse fissures along which eruptions REGIONAL RELATIONS have occurred. The order of extinction has probably not The Hawaiian chain compares favorably in size with been a simple northwest-southeast series, nor has prog­ older and more complex mountain chains in other parts ress necessarily been uniform. Nevertheless, a general of the world. Since the mid-19th century, when Couth- trend is discernible the atolls on the west reflect ouy, Darwin, and Dana speculated about submergence greater subsidence than the reef-fringed high-altitude and the migration of volcanic action in the Hawaiian volcanic islands on the east.