Data Abstraction Mechanisms in Sina/st

This paper describes a new data abstraction mechanism in an object-oriented model of computing. The data abstraction mechanism described here has been devised in the context of the design of Sina/st language. In Sina/st no language constructs have been adopted for specifying inheritance or delegation, but rather, we introduce simpler mechanisms that can support a wide range of code sharing strategies without selecting one among them as a language feature. Sina/st also provides a stronger data encapsulation than most of the existing object-oriented languages. This language has been implemented on the SUN 3 workstation using Smalltalk

Timing of initiation of reverse displacement on the Taranaki Fault, northern Taranaki Basin: Constraints from the on land record (Oligocene Te Kuiti Group)

Structures associated with the wedge of basement overthrust into Taranaki Basin along the Taranaki Fault, are regarded as hydrocarbon plays and have been tested by drilling through the tip of the overthrust. The timing of initiation of reverse displace ment on Taranaki Fault is difficult to interpret from available seismic reflection data across it because the evidence has been masked by later movements. The record from the basin, as summarised in King & Thrasher (1996), suggests that the fault evolved from normal to reverse character during the mid-Oligocene. This was inferred from formation of a foredeep parallel to, and west of, Taranaki Fault and a marked increase in its paleo-water depth, as indicated by foraminiferal assemblages of Late Oligocene age. A comprehensive re-assessment of the lithostratigraphy and sequence stratigraphy of the Late Eocene-Oligocene Te Kuiti Group exposed on land east of Taranaki Fault in central-western North Island, between Port Waikato and Awakino, provides new constraints on the early history of Taranaki Fault displacement. New age control has been achieved by a review of existing foraminiferal biostratigraphy combined with determination of Sr isotope ages from macrofossil samples. Six unconformity-bound sequences have been identified and mapped within the Te Kuiti Group. A major subaerial unconformity between sequences TK3 and TK4 combined with a basinward shift in the position of onlap for sequence TK4 indicate a dramatic change in stratigraphic development and basin dynamics during the mid-upper Whaingaroan at c. 29 Ma, corresponding to the change from mild extension (sag basin) to shortening across the Taranaki Fault Zone. We consider sequences TK4 – TK6 to each represent tectonic cycles of subsidence and basin inversion and we attribute the origin of these cycles to periodic locking of the Taranaki Fault décollement in underlying Murihiku basement, the accumulating strain causing uplift in the basin east of the fault zone, followed by free displacement, relaxation in the upper crust and subsidence. A 1st order model is presented of the Late Oligocene to earliest Miocene vertical and horizontal displacement of basement on the Taranaki Fault Zone for a west –east transect through Awakino. It implies that the mid- to Late Oligocene displace¬ment on the fault zone in the vicinity of Awakino was episodic, and that the thrust belt was narrow (c. 15 km). North of Kawhia Harbour there will have been a different displacement history with most of the total displacement occurring during the devel opment of the c. 29 Ma unconformity at the base of Sequence TK4, whereas to the south between Awakino and Kawhia Harbour the majority of the total displacement occurred during the Otaian and at the end of it. The model also shows that the start of reverse/thrust displacement on Taranaki Fault must have involved the development of a completely new fault trace(s), rather than involving a change of sense of movement on the pre-existing normal fault. The Manganui Fault is part of the Taranaki Fault Zone and probably became active at c. 27 Ma during development of the unconformity between sequences TK4 & TK5. The model presented here has been validated against the subsurface Oligocene stratigraphy in Taranaki Basin

Te Kuiti Group (Late Eocene - Oligocene) lithostratigraphy east of Taranaki Basin in central-western North Island, New Zealand

This report presents a lithostratigraphy for the Late Eocene - Oligocene Te Kuiti Group that crops out in central-western North Island, New Zealand, between Port Waikato in the north and Awakino in the south. The Te Kuiti Group is a mixed carbonate-siliciclastic succession and includes extensive limestone development in its upper parts. The group is up to several hundred metres thick, and accumulated unconformably above indurated Triassic and Jurassic sedimentary basement. The Te Kuiti Group accumulated east of Taranaki Fault and contains a record of sequence and unconformity development that helps constrain the tectonic development of eastern Taranaki Basin. In particular, it records the timing of the mid-Oligocene transition from extension to crustal shortening. Most of the report is however concerned with rationalisation of the group’s lithostratigraphy to enable the geological signals within it to be inferred

Stratigraphic columns and correlations for the Late Eocene - Oligocene Te Kuiti Group, central-western North Island, New Zealand

This report presents a compilation of stratigraphic columns for geological sections and outcrops of Late Eocene – Oligocene Te Kuiti Group units in central-western parts of North Island, New Zealand, between Port Waikato and Awakino. The columns have been prepared as part of a basin analysis investigation undertaken by the Sedimentary and Petroleum Geology Research Group in the Department of Earth and Ocean Sciences at the University of Waikato, and have been compiled into a common format from recent MSc and PhD theses to make the information more readily available, principally to assist hydrocarbon exploration activities in the region. The columns represent a level of detail underpinning a rationalized lithostratigraphy of the Te Kuiti Group presented in a companion report (Tripathi et al. 2008). This report contains two enclosures, one show in the location of columns in relation to the distribution of the two subgroups (Okoko Subgroup, Castle Craig Subgroup) of the Te Kuiti Group, and the other shows a series of north-south and west-east column correlation panels

Basin analysis of the late Eocene - Oligocene Te Kuiti Group, western North Island, New Zealand

Paleogeography - Te kuiti group (Map 1-13) in print copyThe Late Eocene - Oligocene Te Kuiti Group crops out extensively in central-western North Island between Port Waikato and Awakino, providing a useful window for examination of a broadly transgressive shelfal to upper bathyal mixed carbonate-siliciclastic basin fill succession. The group accumulated during initiation of Cenozoic glaciations on Antarctica when there may have been associated eustatic changes in sea- level changes, and during the initiation of the Australia-Pacific plate boundary through the New Zealand region, which might also have caused relative changes in sea level in the Waikato Basin. As part of this study Te Kuiti lithostratigraphy in central-western North Island has been reviewed and rationalized. Special emphasis has been given to correlation of the significant stratigraphic discontinuities (erosional unconformities, depositional hiatuses) between units. Combined with a review of the foraminiferal biostratigraphy and new Sr isotope ages for the group, lithologically diverse formations have been able to be correlated across and along the outcrop belt. In the revised stratigraphic scheme, seven formations and 24 members of Kaiatian to Waitakian (Late Oligocene to Early Miocene) age are identified. The Te Kuiti Group is subdivided into two subgroups, a lower Okoko Subgroup, and an upper Castle Craig Subgroup. The Okoko Subgroup is dominated by calcareous siltstone and sandstone members, with limestone members commonly occurring at the base of formations, whereas the Castle Craig Subgroup is almost entirely comprised of limestone in the south and by calcareous siltstone in the northern parts of the basin. Six unconformity-bound sequences (TK1 - TK6) have been identified and mapped within the Te Kuiti Group using sequence stratigraphic principles. For several of these sequences (TK2, TK4, TK5 TK6) detailed facies and sequence analyses have been undertaken based on field characteristics, complemented with laboratory grain size and compositional (carbonate % and thin-section) data. The depositional paleoenvironments have been interpreted for these sequences, with the basin evolution for all sequences summarised in a series of 13 paleogeographic maps representing multiple horizons within the Te Kuiti Group. TK1 strata are mostly terrestrial coal measures (Waikato Coal Measures) of Late Eocene to earliest Oligocene age that accumulated in paleovalleys concurrent with minor extensional faulting. The upper beds are marginal marine and consist primarily of estuarine and shallow shelf mudstone (Mangakotuku Formation). The Early Oligocene (lower Whaingaroan) Glen Massey Formation (TK2) is entirely marine in origin, its lowermost member (Elgood Limestone Member) marking a significant marine flooding event across the basin with a landward shift in the position of stratal onlap. Whaingaroa Formation (TK3) comprises predominantly siltstone with some limestone (Awaroa Limestone Member) at its base in the south, which reflects expansion of a southern shelf area. An extensive subaerial unconformity between Whaingaroa Formation (TK3) and Aotea Formation (TK4), combined with a basinward shift in the position of onlap for sequence TK4, indicates a dramatic mid-upper Whaingaroan (c. 29 Ma) change in stratigraphic development and basin dynamics inferred to result from the start of reverse displacement on Taranaki Fault along the basin's western margin. Aotea Formation comprises lithologically diverse facies dominated by limestone (Waimai Limestone Member) in the north, calcareous sandstone (Hauturu Sandstone Member) in the southwest and muddy sandstone (Kihi Sandstone Member) in south-central and eastern areas. A condensed section in the upper parts of Aotea Formation, especially in the north, records relative deepening and reduction of clastic sediment supply into sediment-starved northern parts of the basin. A major erosional unconformity at the base of the Castle Craig Subgroup in the south and a depositional hiatus in the north reflects a second phase of inversion along the southwestern margin of the basin and reverse displacement on Manganui Fault at c. 27 Ma. The rocky shorelines that consequently formed along the eastern side of the Herangi High supported carbonate factories supplying reworked carbonate to the adjacent shelf (Orahiri Formation and Otorohanga Limestone). These formations pass northward into outer shelf-upper bathyal micritic limestone (Raglan Limestone Member) and calcareous siltstone (marl). Several additional phases of unconformity development are recorded in the Castle Craig Group, but these unconformities had limited extent in the basin, being mainly restricted to the area immediately west of the Herangi High. Early Miocene Waitemata Group strata unconformably overlie the Te Kuiti Group in the north, reflecting basin inversion and erosion driven from a developing subduction zone to the northeast, whereas early Miocene Mahoenui Group strata in southern parts of the basin are mostly conformable on the Te Kuiti Group, having accumulated in a piggy-back basin carried westward on underlying Taranaki and related faults. Tectonic movements and cycles of subsidence and subtle basin inversion driven by the alternate accumulation and release of strain on Taranaki and related fault are regarded as the primary control on relative sea-level changes within the Te Kuiti Group, which led to sequences TK4-TK6. The accumulation of sequences TK1-TK3 resulted from tectonic subsidence in the Waikato region as the zone of extension widened to the east of Taranaki Basin coupled with progressive landward shifts in the position of coastal onlap. Glacio-eustatic sea- level changes driven from glaciations in Antarctica are not regarded as having generated sea-level changes of sufficient magnitude to impact upon the dynamics of late Eocene and Oligocene sedimentation in the Waikato Basin when the Te Kuiti Group accumulated

Petrologic evidence for earliest Miocene tectonic mobility on eastern Taranaki Basin margin

At Gibsons Beach on the west coast of central North Island, the earliest Miocene (Waitakian) Otorohanga Limestone, the top-most formation in the Te Kuiti Group, is unconformably overlain on an undulating, locally channelised erosion surface by the Early Miocene (Otaian) Papakura Limestone at the base of the Waitemata Group. The basal facies of the Papakura Limestone is a conglomerate composed exclusively of tightly packed pebble- to cobble-sized clasts of skeletal limestone sourced from the underlying Otorohanga Limestone. This petrographic and geochemical study demonstrates that the Otorohanga Limestone was partially lithified during marine and shallow-burial cementation at subsurface depths down to a few tens of metres prior to uplift, erosion and cannibalisation of the limestone clasts into the Papakura Limestone. Strontium isotope dating of fossils from both the Otorohanga and Papakura Limestones at Gibsons Beach yield comparable ages of about 22 Ma, close to the Waitakian/Otaian boundary, indicating very rapid tectonic inversion and erosion of the section occurred in the earliest Miocene. We envisage the clasts of Otorohanga Limestone were sourced from a proximal shoreline position and redeposited westwards by episodic debris flows onto a shallow-shelf accumulating mixed siliciclastic-skeletal carbonate deposits of the Papakura Limestone. Subsequent burial of both limestones by rapidly accumulating Waitemata Group sandstone and flysch instigated precipitation of widespread burial cements from pressure dissolution of carbonate material at subsurface depths from about 100 m to 1.0 km. The vertical tectonic movements registered at Gibsons Beach can be related to the oblique compression associated with the development of the Australian-Pacific plate boundary through New Zealand at about this time and coincide with overthrusting of basement into Taranaki Basin between mid-Waitakian (earliest Miocene) and Altonian (late Early Miocene) times