Two Cretaceous Volcanic Episodes in the Western Pacific Ocean
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Two Cretaceous volcanic episodes in the western Pacific Ocean DAVID K. REA Oceanography Program, Department of Atmospheric and Oceanic Science, The University of Michigan, Ann Arbor, Michigan 48109 TRACY L. VALLIER Pacific-Arctic Branch of Marine Geology, U.S. Geological Survey, Menlo Park, California 94025 ABSTRACT many of the volcanic forms of the central and the Magellan, Shatsky, and Hess Rises. and western Pacific (Menard, 1964). Later All oceanic plateaus of the western Pacific Stratigraphic analyses of cores recovered results of the Deep Sea Drilling Project may be the result of spreading-ridge vol- by the Deep Sea Drilling Project from the (DSDP) from drill holes in the region (Fig. canic activity (Watts and others, 1980), and western Pacific Ocean confirm that Cre- 1) confirmed a Cretaceous age for most of all except the Shatsky Rise, which is in part taceous volcanic activity in that region was these features. The problem of the sudden older, appear to be Early to middle Cre- common, and that two separate major epi- drowning of the guyot-atolls in middle to taceous in age. It is evident that the western sodes of activity can be distinguished. The Late Cretaceous time, however, remains Pacific has had a complex tectonic history older episode, Aptian to Cenomanian in unresolved (Matthews and others, 1974; in terms of both sea-floor spreading (Larson age, resulted in the formation of most of the Winterer, 1980; Schlager, 1981). and Chase, 1972; Larson, 1976; Hilde and oceanic plateaus in the western Pacific. In Volcanic activity in the western Pacific others, 1977) and volcanic activity (Jack- the younger, Santonian to Maastrichtian Ocean has produced four major types of son, 1976; Winterer, 1976a; Watts and oth- episode, several island and seamount chains geomorphic features: (1) island arcs; (2) lin- ers, 1980; Schlanger and others, 1981). formed, especially those in the west-central ear, oceanic island and seamount chains; (3) Most of the information on volcanism in Pacific that trend north-northwest. These oceanic islands, seamounts, and guyots that the western Pacific has been obtained from volcanic events, among the most extensive are isolated or occur in irregular groups; examinations of dredged rocks, piston in the marine geologic record, covered an and (4) oceanic plateaus (aseismic rises). cores, drill holes, and geophysical data. 6 2 area of at least 30 xlO km . Possibly, the Morgan's (1972a, 1972b) hypothesis that Information from volcanogenic sediments older episode was responsible for a Cre- linear island and seamount chains were has not been used to attempt a coherent taceous sea-level high and concomitant epi- formed by the migration of the Pacific plate story of volcanism on the Pacific plate, continental transgression. The younger epi- over a (fixed) melting point in the Earth's although its potential significance has been sode of volcanism certainly covered an mantle stimulated a variety of investigations recognized for some time (Nayudu, 1964; extensive area, but its effect upon sea level into the age of those features. Morgan's Horn and others, 1969; Scheidegger, 1973; may not have been as great as that of the hypothesis appears to hold for many of the Kennett and Thunell, 1975). older event. west-northwest-trending chains but, except Attempts to synthesize data from the for the Emperor Seamounts, not for the results of the DSDP have been both gratify- INTRODUCTION north-northwest-trending chains (Duncan ing and frustrating (Moore, 1972). The most and McDougall, 1976; Jackson, 1976; Jar- common frustration involves the incom- The ages of guyots, seamounts, and oce- rard and Clague, 1977; Jackson and others, plete recovery of the drilled section. During anic islands of the central and western Paci- 1980). earlier legs of the project, many sections fic Ocean have been a topic of discussion Linear island and seamount chains, such were spot-cored, and large parts of the sed- since Hess (1946) presumed that guyots are as the Line Islands and the Marshall- imentary column were not sampled. Con- Precambrian in age. Hess reasoned that the Gilbert-Ellice chain that appear to be iso- tinuous coring improved recovery marked- guyots must have submerged before the evo- chronous along their length, may have ly, but several problems remain. For exam- lution of carbonate-secreting organisms; formed by offridge volcanic extrusion ple, rotary drilling commonly churns un- otherwise, atolls would have formed. Sub- along pre-existing fracture zones (Hilde and consolidated sediments into a thick slurry sequent sampling of guyots during the early others, 1977). Isolated and irregular groups and displaces initially horizontal boundar- 1950s resulted in recovery of a suite of of volcanic islands and seamounts number ies through several metres of core. Particu- Aptian and younger Cretaceous, shallow- in the thousands and volumetrically consti- larly low recovery occurs in holes that water fossils (Hamilton, 1953, 1956). Two tute a large part of the oceanic crust (Batiza, encounter chert. The Pacific Cretaceous holes were drilled on Eniwetok Atoll in 1977). These volcanic forms vary greatly in sections contain abundant chert, and in 1952; the recovered section included shal- size, shape, distribution, age, relation to tec- some holes thick sequences of cored sedi- low-water Eocene limestone overlying ba- tonic features, and petrology. The several ments yielded nothing but chert fragments. salt (Ladd and others, 1953). Thus, by the broad oceanic plateaus of the western When recovery is not total (100%), the mid-1950s, the Cretaceous and younger Pacific include the Manihiki and Ontong- materials brought on deck in the 9.5-m core ages were reasonably well established for Java Plateaus, the Mid-Pacific Mountains, barrel are, by convention, stratigraphically Geological Society of America Bulletin, v. 94, p. 1430-1437, 5 figs., 1 table, December 1983. 1430 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/94/12/1430/3444663/i0016-7606-94-12-1430.pdf by guest on 25 September 2021 CRETACEOUS VOLCANIC EPISODES, PACIFIC OCEAN 1431 150° 160° 170° E 180° 170° W 160° 150° 50° 50° 40° Figure 1. Map of the western Pacific Ocean show- ing the locations of the 35 DSDP sites where Creta- 30° 30° ceous sediments were recov- ered. 20° 20° 10° N 10° N 0° 0° I0°S 10° s 150° 160° 170° E 180° 170° W 160° 150° "hung" from the top of that 9.5-m interval. relied primarily on the descriptions given in VOLCANOGENIC SEDIMENTS There is no way to determine what is miss- the DSDP Initial Reports. ing and thereby position the recovered We studied sediment data from 73 sites of Volcanogenic sediments are volumetri- material more accurately. As a result of 16 DSDP legs (6, 7, 8, 9, 16, 17, 19, 20, 21, cally important in the total sediment vol- these mechanical problems, the positions of 30, 32, 33, 55, 60, 61, and 62) in a region ume in the world's oceans. Sediment aprons biostratigraphic boundaries are commonly bounded approximately by 160°W, 40° N, and fans along some island arcs and large only approximate. This unavoidable impre- 20°S, and the west Pacific trenches, an area chains or groups of oceanic islands can be ssion is carried over in determining linear of about 40 x 106 km2. Within this region, several kilometres thick. Volcanogenic sedimentation rates and all values based on cores at 35 drill sites (Table 1 and Fig. 1) material also is found in deep-sea sediments those rates. penetrated Cretaceous sediments. We exam- far from landmasses, where its contribution In this study, however, we are more inter- ined the relevant data in order to unravel may be masked by biogenic sediment. red in the age of a specific stratigraphic the temporal and spatial records of volcan- Sources for most of these volcanogenic unit and less so in the rates of sedimenta- ism and constructed a plot of the strati- components in deep-sea sediment are island ;ion. We assigned ages to volcanogenic graphic position of volcanogenic material at volcanoes, from where the products of materials on the basis of the associated each site versus the age of that occurrence explosive volcanism are transported by nicrofossils (van Hinte, 1976), and we did (Fig. 2) to show that volcanic activity took wind and, in places, probably by turbidity lot specifically re-examine any samples but place episodically during the Cretaceous. and other bottom currents. Studies of mod- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/94/12/1430/3444663/i0016-7606-94-12-1430.pdf by guest on 25 September 2021 1432 REA AND VALUER TABLE 1. DRILL SITES WHERE CRETACEOUS SEDIMENT WAS RECOVERED. GROUPED AS WITH OR WITHOUT em (Cook and others, 1981) and past ash VOLCANOGENIC MATERIAL deposits (Huang and others, 1975; Kennett and Thunell, 1975) show that most ash is Time interval recovered deposited within 500 or 1,000 km of the 65-80 m.y. ago 80-95 m.y. ago 95-110 m.y. ago 110-125 m.y. ago 125-140 m.y. ago source. Only the largest eruptions result in deep-sea ash layers at greater distances (Ninkovich and Shackleton, 1975; Ninko- 47 66 66 164 164 196 166 164 vich and others, 1978). It is unlikely, then, 48 163 169 167 166 305 194 167 61 164 170 196 167 306 288 196 that more than a small percentage of the 165 167 171 305 169 307 289 303 169 288 288 310 170 307 304 volcanogenic sediment now in the western 170 289 462 317 171 317 305 Pacific came from beyond that general 171 317 463 194 462 306 192 464 288 463 region. Submarine volcanism on seamounts 196 465 289 198 466 310 and other parts of the sea floor also 199 317 accounts for some of the volcanic sediment, 305 462 310 463 but the amount is difficult to assess (Mob- 313 464 315 465 erly and Jenkyns, 1981).