Abstract Limestones whose constituents were deposited in shallow water are useful indicators of post-depositional uplift, subsidence and latitudinal changes through time. A review of such limestones, drilled at several dozen DSDP sites in all of the major ocean basins, demonstrates their utility in deciphering the geologic history of major structural features and in contributing to our knowledge of paleoceanographic conditions. Drilling in the northeast Providence Channel of the Bahamas, on the Blake Nose and off the Grand Banks of Newfoundland has extended our knowledge of the Cretaceous reef trends and carbonate shelf margins in the Atlantic passive margin province and has demonstrated subsidence of several kilometers there since Cretaceous time. The Rio Grande Rise and the Walvis Ridge both had Late Cretaceous and Eocene shallow-water histories related to their subsidence as paired aseismic ridges. On Orphan Knoll and Rockall Bank, Jurassic to Paleogene shallow-water sediments containing rich Paleocene bryozoan faunas confirm plate reconstructions for the early opening of the Atlantic. On the aseismic Ninetyeast Ridge in the Indian Ocean shallow-water sediments, including lignite deposits, directly above the basalt basement indicate a progressive subsidence history for the ridge similar to that of an island-seamount chain. In the Pacific Ocean the widespread occurrence of Campanian-Maestrichtian reef faunas from the Line Islands to the Nauru Basin-Marshall Islands leads to an interpretation of central Pacific bathymetric history reminiscent of the Darwin Rise of Menard in that mid-plate volcanism resulted in regional uplift in the central Pacific between ~ 115-110 and 70 m.y.BP. This uplift contributed to the major Cretaceous transgression during that period. Invocation of a spreading rate increase along mid-ocean ridges as the sole explanation for this transgression may not be necessary. The large benthic foraminifers of Late Cretaceous age recovered along the Line Islands and in the Nauru Basin have affinities to those of the Caribbean, indicating that the mid-Pacific atoll scene was not dominated by an Indo-Pacific fauna until Cenozoic time. Further, the Caribbean affinities of the central Pacific Late Cretaceous reef faunas lends credence to earlier suggestions that the Caribbean plate is a relic of the Farallon plate. Analysis of vertical tectonics in the Pacific shows that estimates of paleo-CCD levels should take into account periods of uplift which interrupted normal plate subsidence. Cenozoic reef debris found in turbidite units in deep-water fan deposits adjacent to the Line and Marshall islands chains record global sealevel changes. Drilling on the Emperor Seamounts has revealed Paleogene bryozoan- algal limestones whose latitude of deposition confirms paleomagnetic data from Suiko Seamount which indicate that this seamount did not form at the latitude of the present Hawaiian hot spot.

Abstract A combination of geophysical studies and deep-sea drilling have in the past suggested that orthogonally rifted margins fall into two end-members: volcanic-rifted margins (e.g. eastern Greenland) and non-volcanic rifted margins (e.g. Iberia–Newfoundland conjugate). This paper explores the rifted margins of the Eastern Tethys stretching from the Eastern Mediterranean, through Oman to the Himalayas. Rifting in these area was typically pulsed, extending over more than 50 Ma. The timing of final continental breakup ranged from Late Permian in the east, in Oman and the Himalayas, to latest Triassic–earliest Jurassic in many parts of the Eastern Mediterranean (e.g. Antalya in SW Turkey; Pindos in Greece). Rifting in the Himalayas and Oman gave rise to a proximal to a distal ramp geometry with scatted seamounts (continental fragments and atolls) located adjacent to the rifted margin. The Eastern Mediterranean was palaeogeographically varied, and was characterized by a number of mainly elongate continental fragments (tens to several hundreds of kilometres long by tens of kilometres wide). These microcontinents subdivided the Eastern Tethys in the Eastern Mediterranean region into several small ocean basins, which rifted at more or less the same time in latest Triassic–earliest Jurassic time. All of the rifted margins of the Eastern Tethys are associated with rift-related volcanic rocks. However, with the exception of the Permian Panjal Traps in the Himalayas, the volumes of magma and corresponding thermal doming were less than for the ideal Volcanic-rifted margin (i.e. eastern Greenland). None of the Eastern Tethyan rifted margins show evidence of features characteristic of Non-volcanic rifted margins (e.g. sea-floor serpentinite exhumation), in contrast to the Iberia–Newfoundland conjugate or the Alps. Most of the Eastern Tethyan rifted margins appear to correspond to an ‘intermediate’ type, characterized by pulsed rifting, limited rift volcanism and a narrow continent–ocean transition zone. Such ‘intermediate-type’ rifted margins may remain to be explored in the modern oceans by deep-sea drilling. There is little evidence to support previous suggestions that the Eastern Tethyan rifts can be considered as back-arc basins above either northward- or southward-dipping subduction zones. Here it is suggested that the Eastern Tethys documents a fundamentally different type of rifting from either the ‘Volcanic-related’ or ‘Non-volcanic’ intracontinental rifts known from the Alps or the North Atlantic region. The dominant controls of rifting are seen as the traction of rising asthenosphere on the base of the lithosphere, related deviatoric tensional stresses, inherited and thermally induced weaknesses in the crust, and slab-pull. Specifically, in the Eastern Tethyan region continental breakup was probably triggered by a combination of long-term asthenosphere flow, slab-pull related to subduction beneath Eurasia and melt-induced crustal weakening associated with pulsed rifting or plume effects. Final continental breakup corresponds to a major (‘Cimmerian’) convergent phase along the opposing Eurasia margin, which further supports the role of plate boundary forces in Eastern Tethyan rifting. The early Mesozoic oceanic basins opened, probably associated with northwestward propagation of a spreading centre through the already weakened periphery of Gondwana, adjacent to less deformable Palaeotethyan oceanic crust. After a lengthy period of passive margin subsidence, locally punctuated by crustal extension and related volcanism, or plume effects, the rifted margins were finally tectonically emplaced during mid-Mesozoic, late Mesozoic or early Cenozoic time in different areas.