Geoscience Australia seismic survey 310: revealing stratigraphy and structure of the outer northern Perth Basin margin

2013 ◽  
Vol 53 (2) ◽  
pp. 481
Author(s):  
George Bernardel ◽  
Chris Nicholson
Keyword(s):  
Late Jurassic ◽  
Field Data ◽  
Strike Slip ◽  
Source Rocks ◽  
Seismic Survey ◽  
The South ◽  
Potential Field Data ◽  
Reflection Seismic ◽  
The North ◽  
Seismic Lines

Geoscience Australia acquired seismic survey GA 310 in 2008–09, across the southwest margin of Australia, as part of the Australian government’s Energy Security Program. Deep reflection seismic and potential field data were recorded across sparse 2D grids located on the Wallaby Plateau in the north, Mentelle Basin in the south, and the intervening Houtman and Zeewyck sub-basins of the northern Perth Basin. The offshore northern Perth Basin extends for about 700 km along the Western Australia margin, from the towns of Carnarvon in the north to Cervantes in the south. The largely Paleozoic-Mesozoic tectonostratigraphic framework is dominated by Permian and Early-Middle Jurassic rifting, followed by Late Jurassic-Early Cretaceous rifting leading to Valanginian breakup between Australia and Greater India. Underlying Precambrian Pinjarra Orogen structuring, in conjunction with rifting, has resulted in the development of several complex depocentres and basement highs. A recent re-evaluation of the offshore northern Perth Basin well-based lithostratigraphy into a new chronostratigraphic sequence framework has been carried outboard, on the GA 310 seismic lines, into the margin bounding the Zeewyck and northern Houtman sub-basins. The main sequences hosting source rocks—Kockatea and Cattamarra—are widely present in the expansive northern Houtman Sub-basin, and are likely to be present in the deep Zeewyck Sub-basin. The mapping of a thick Late Jurassic Yarragadee Sequence in the Zeewyck Sub-basin indicates a major pre-breakup locus of relatively rapid deposition. The structural interpretation across the sub-basin highlights breakup-drift unconformities and strike-slip faulting and suggests a probable along-margin sheared crustal sliver; tectonic elements commensurate with an evolving rift-shear breakup margin.

scholarly journals Crustal variability along the rifted/sheared East African margin: a review

2021 ◽  
Vol 41 (2) ◽  
Author(s):  
Maren Vormann ◽  
Wilfried Jokat
Keyword(s):  
East Africa ◽  
Shear Zone ◽  
Structural Changes ◽  
The South ◽  
East African ◽  
The North ◽  
Rifted Margins ◽  
Continental Block ◽  
Seismic Lines ◽  
Southeastern Madagascar

AbstractThe East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.

scholarly journals South Anyui suture: tectono-stratigraphy, deformations, and principal tectonic events

2009 ◽  
Vol 4 ◽  
pp. 201-221 ◽  
Author(s):  
S. D. Sokolov ◽  
G. Ye. Bondarenko ◽  
P. W. Layer ◽  
I. R. Kravchenko-Berezhnoy
Keyword(s):  
Active Continental Margin ◽  
Strike Slip ◽  
Passive Margin ◽  
The South ◽  
Asian Continent ◽  
Oblique Collision ◽  
North Asian Craton ◽  
The North ◽  
Continental Block ◽  
South Anyui Suture

Abstract. Geochronologic and structural data from the terranes of the South Anyui suture zone record a protracted deformational history before, during and after an Early Cretaceous collision of the passive margin of the Chukotka-Arctic Alaska continental block with the active continental margin of the North Asian continent. Preceding this collision, the island arc complexes of the Yarakvaam terrane on the northern margin of the North Asian craton record Early Carboniferous to Neocomian ages in ophiolite, sedimentary, and volcanic rocks. Triassic to Jurassic amphibolites constrain the timing of subduction and intraoceanic deformation along this margin. The protracted (Neocomian to Aptian) collision of the Chukotka passive margin with the North Asian continent is preserved in a range of structural styles including first north verging folding, then south verging folding, and finally late collisional dextral strike slip motions which likely record a change from orthogonal collision to oblique collision. Due to this collision, the southern passive margin of Chukotka was overthrust by tectonic nappes composed of tectono-stratigraphic complexes of the South Anyui terrane. Greenschists with ages of 115–119 Ma are related to the last stages of this collision. The postcollisional orogenic stage (Albian to Cenomanian) is characterized by sinistral strike slip faults and an extensional environment.

The arc of the Western Alps : understanding its kinematics and formation mechanisms based on new structural and paleomagnetic datas, and thermo-mechanical modelling.

2021 ◽  
Author(s):  
Quentin Brunsmann ◽  
Claudio Rosenberg ◽  
Nicolas Bellahsen ◽  
Laetitia Le Pourhiet
Keyword(s):  
Western Alps ◽  
Strike Slip ◽  
Rheological Parameters ◽  
The South ◽  
Adriatic Plate ◽  
The North ◽  
Field Evidence ◽  
Internal Zone ◽  
The Alps ◽  
East West

<p>The Alps have an overall East-West orientation, which changes radically in their western termination, where they rotate southward into a N-S strike, and then eastward into an E-W strike, forming the arc of the Western Alps. This arc is commonly inferred to have formed during collision, due to indentation of the Adriatic plate into the European continental margin. Several models attempted to provide a kinematic explanation for the formation of this arched, lateral end of the Alps. Indeed, the radial nature of the transport directions observed along the arc of the Western Alps cannot be explained by a classic convergence model.<br>For more than 50 years the formation of this arc was been associated to westward-directed indentation of Adria, accommodated along East-West oriented strike-slip faults, a sinistral one in the South of the arc and a dextral one in the North. The dextral one correspond to the Insubric Fault. The sinistral strike-slip zone, inferred to be localized along the «Stura corridor» (Piedmont, Italy) would correspond to a displacement of 100 to 150 km according to palaeogeographical, and geometric analyses. However, field evidence is scarce and barely documented in the literature.<br>Vertical axis rotations of the Adriatic indenter also inferred to be syn-collisional could have influenced the acquisition of the morphology of the arc. Paleomagnetic analyses carried out in the Internal Zone and in the Po plain suggest a southward increading amount of counter-clockwise rotation of the Adriatic plate and the Internal Zone, varying from 20°-25° in the North to nearly 120° in the South.<br>Dextral shear zones possibly accommodating this rotation in some conceptual models is observed in several places below the Penninic Front and affect the Argentera massif to the south. However, the measured displacement quantities do not appear to be equivalent to those induced by such rotations.<br>The present study aims to constrain the kinematic evolution of the arc of the Western Alps through a multidisciplinary approach. The first aspect of this project is the structural analysis of the area (Stura corridor) inferred to accommodate large sinistral displacements allowing for the westward indentation of the Adriatic indenter. We discuss the general lack of field evidence supporting sinistral strike-slip movements, in contrast to large-scale compilation of structures suggesting the possible occurrence of such displacement. The second part consists of a palaeomagnetic study, in which new data are integred with a compilation of already existing data. This compilation shows that several parts of the arc in the External Zone did not suffer any Cenozoic rotations, hence suggesting that a proto-arc already axisted at the onset collision, as suggested by independent evidence of some paleogeographic reconstruction. Finally, 2D and 3D thermo-mechanical modeling in using the pTatin3D code is used to test which structural (geometrical), and rheological parameters affected the first-order morphology of the Western Alpin arc and its kinematics. The synthesis of these different approaches allows us to propose a new model explaining the kinematics and the mechanisms of formation of the Western Alps arc.</p>

Archaeological Operations

2018 ◽  
pp. 126-193
Author(s):  
Jonathan Kaplan ◽  
Federico Paredes Umaña
Keyword(s):  
Control System ◽  
Hierarchical Structure ◽  
Field Data ◽  
The South ◽  
Water Control ◽  
Long Distance ◽  
The North ◽  
Ancient Society ◽  
Preclassic Period

Chapter 4 abstracts and summarizes the very copious field data from the three lengthy field seasons at Chocolá, including the specific evidence obtained about the very extensive water control system that was discovered. Intensive grid excavations were undertaken in five operations: Mound 15, the northernmost part of the elite north sector, Mounds 6 and 7, in the southern part of the north sector, Mound 2, in the central administrative sector, and Mound 5, in the south sector. Accordingly, our three field seasons provide the specific evidence and artifacts we have been able to use to understand the clearly hierarchical structure of the ancient society and city. Of particular importance for a better understanding of the material underpinnings of Chocolá is our research at Mound 5, in the south, where we believe cacao arboriculture was developed for long-distance trade in the Preclassic period.

The discovery of a new sedimentary basin: offshore Raukumara, East Coast, North Island, New Zealand

2008 ◽  
Vol 48 (1) ◽  
pp. 53 ◽  
Author(s):  
Chris Uruski ◽  
Callum Kennedy ◽  
Rupert Sutherland ◽  
Vaughan Stagpoole ◽  
Stuart Henrys
Keyword(s):  
New Zealand ◽  
Oil And Gas ◽  
East Coast ◽  
Plate Boundary ◽  
Source Rocks ◽  
Fault System ◽  
Northern Coast ◽  
The South ◽  
Petroleum Potential ◽  
The North

The East Coast of North Island, New Zealand, is the site of subduction of the Pacific below the Australian plate, and, consequently, much of the basin is highly deformed. An exception is the Raukumara Sub-basin, which forms the northern end of the East Coast Basin and is relatively undeformed. It occupies a marine plain that extends to the north-northeast from the northern coast of the Raukumara Peninsula, reaching water depths of about 3,000 m, although much of the sub-basin lies within the 2,000 m isobath. The sub-basin is about 100 km across and has a roughly triangular plan, bounded by an east-west fault system in the south. It extends about 300 km to the northeast and is bounded to the east by the East Cape subduction ridge and to the west by the volcanic Kermadec Ridge. The northern seismic lines reveal a thickness of around 8 km increasing to 12–13 km in the south. Its stratigraphy consists of a fairly uniformly bedded basal section and an upper, more variable unit separated by a wedge of chaotically bedded material. In the absence of direct evidence from wells and samples, analogies are drawn with onshore geology, where older marine Cretaceous and Paleogene units are separated from a Neogene succession by an allochthonous series of thrust slices emplaced around the time of initiation of the modern plate boundary. The Raukumara Sub-basin is not easily classified. Its location is apparently that of a fore-arc basin along an ocean-to-ocean collision zone, although its sedimentary fill must have been derived chiefly from erosion of the New Zealand land mass. Its relative lack of deformation introduces questions about basin formation and petroleum potential. Although no commercial discoveries have been made in the East Coast Basin, known source rocks are of marine origin and are commonly oil prone, so there is good potential for oil as well as gas in the basin. New seismic data confirm the extent of the sub-basin and its considerable sedimentary thickness. The presence of potential trapping structures and direct hydrocarbon indicators suggest that the Raukumara Sub-basin may contain large volumes of oil and gas.

Uncovering the Canning Basin: a new comprehensive SEEBASE® model

2018 ◽  
Vol 58 (2) ◽  
pp. 793
Author(s):  
Karen Connors ◽  
Cedric Jorand ◽  
Peter Haines ◽  
Yijie Zhan ◽  
Lynn Pryer
Keyword(s):  
Western Australia ◽  
Potential Field ◽  
Field Data ◽  
Regional Scale ◽  
Structural Evolution ◽  
Potential Field Data ◽  
Canning Basin ◽  
The North ◽  
Wide Range ◽  
Order Of Magnitude

A new regional scale SEEBASE® model has been produced for the intracratonic Canning Basin, located in the north of Western Australia. The 2017 Canning Basin SEEBASE model is more than an order of magnitude higher resolution than the 2005 OZ SEEBASE version — the average resolution is ~1 : 1 M scale with higher resolution in areas of shallow basement with 2D seismic coverage — such as the Broome Platform and Barbwire Terrace. Post-2005 acquisition of potential field, seismic and well data in the Canning Basin by the Geological Survey of Western Australia (GSWA), Geoscience Australia and industry provided an excellent opportunity to upgrade the SEEBASE depth-to-basement model in 2017. The SEEBASE methodology focuses on a regional understanding of basement, using potential field data to interpret basement terranes, depth-to-basement (SEEBASE), regional structural geology and basement composition. The project involved extensive potential field processing and enhancement and compilation of a wide range of datasets. Integrated interpretation of the potential field data with seismic and well analysis has proven quite powerful and illustrates the strong basement control on the extent and location of basin elements. The project has reassessed the structural evolution of the basin, identified and mapped major structures and produced fault-event maps for key tectonic events. In addition, interpretative maps of basement terranes, depth-to-Moho, basement thickness, basement composition and total sediment thickness have been used to calculate a basin-wide map of basement-derived heat flow. The 2017 Canning Basin SEEBASE is the first public update of the widely used 2005 OZ SEEBASE. All the data and interpretations are available from the GSWA as a report and integrated ArcGIS project, which together provide an excellent summary of the key features within the Canning Basin that will aid hydrocarbon and mineral explorers in the region.

GEOPHYSICAL EXPLORATION IN TORRES STRAIT

1965 ◽  
Vol 5 (1) ◽  
pp. 188
Author(s):  
E. W. Vind ◽  
C. R. Harwood
Keyword(s):  
Seismic Survey ◽  
Survey Area ◽  
The South ◽  
North East ◽  
The North ◽  
Geophysical Surveys ◽  
Arafura Sea ◽  
Cape York ◽  
Torres Strait ◽  
Marine Seismic

Torres Strait is the narrow waterway on the Continental Shelf which connects the Arafura Sea to the Coral Sea and separates the Cape York Peninsula from South-western Papua. Within Torres Strait and the Arafura Sea the marine seismic survey area specifically discussed here covers the north-western part of Authority to Prospect 104P held by Marathon Petroleum Australia Ltd. Except for a few small islands this area is covered by a shallow tropical sea not more than 160 feet deep which is studded with coral reefs.Four regional structural features influence the area. These are the Cape York-Oriomo Ridge to the east, the Carpentaria Basin to the south and the Morehead and Papuan Basins to the north. These features are indicated by regional geology and have been confirmed by the combined interpretations of reconnaissance geophysical surveys conducted by various exploration organisations during the past 30 years.The A.T.P. 104P (West) Marine Seismic Survey, consisting of 618 miles of subsurface coverage, was carried out for Marathon between November 8 and November 28, 1964.Several operational problems prevented completion of the survey as originally planned. Shallow water and reefing prevented shooting in the north-east portion of the proposed area.Shooting 300 per cent subsurface coverage commenced in the south-eastern part of the survey area, but, due to shallow basement at less than one second, multiple coverage was not feasible. Production shooting which gave 100 per cent subsurface coverage on the short spreads was continued throughout the remainder of the survey.Two reflection horizons and a resultant isochron were mapped in the area. A "deep" reflector is interpreted as originating from granitic basement, while a "shallow" reflector is tentatively correlated with a horizon in the Cretaceous section.The "shallow" horizon mapped is essentially conformable with the "deep" horizon. Both show a regional west dip with thinning of section to the east. Some north and south components of the regional west dip are established. The resultant isochron comparisons based on this work appear too limited in scope to establish any definite local structural control of deposition.

THE ELANG OIL DISCOVERY ESTABLISHES NEW OIL PROVINCE IN THE EASTERN TIMOR SEA (TIMOR GAP ZONE OF COOPERATION)

1995 ◽  
Vol 35 (1) ◽  
pp. 44
Author(s):  
I. F. Young ◽  
T.M. Schmedje ◽  
W.F. Muir
Keyword(s):  
Seismic Data ◽  
Late Jurassic ◽  
Joint Venture ◽  
Seismic Survey ◽  
Normal Faults ◽  
Commercial Development ◽  
The North ◽  
3D Data ◽  
Porosity And Permeability ◽  
Timor Sea

The Elang-1 oil discovery in the Timor Gap Zone of Cooperation (ZOC) has established a new oil province in the eastern Timor Sea. The discovery well, completed in February 1994, recorded a flow of 5,800 BOPD (5,013 STBOPD) from marine sandstone of the Late Jurassic Montara beds. The oil is a light (56° API), undersaturated oil with a GOR of approximately 550 SCF/STB. Elang-1 was the first well drilled by the ZOCA 91-12 Joint Venture and only the fifth well in the ZOC since exploration of this frontier area resumed in 1992.The Elang Prospect, initially mapped by Petroz in the late 1970s on the basis of regional seismic data, was detailed by the 1992 Walet Seismic Survey. The prospect is the main crestal culmination on the Elang Trend, a prominent structural high to the north of the Flamingo High that was established during continental break-up in the Late Jurassic. The Elang Trend is bounded to the south by a series of en-echelon normal faults and connecting relay ramps and comprises a number of horst and tilted fault blocks.Elang-1 tested a near crestal culmination on the Elang Prospect and intersected a 76.5 m gross oil column below 3,006.5 m RT. At time of drilling this oil column was the thickest that had been encountered by any well in the Northern Bonaparte Basin. Good quality reservoir sandstone in six discrete bodies were intersected within the Montara beds. Core-measured porosity and permeability range up to 17 per cent and 2.2 Darcies within the oil column.Subsequent to the Elang discovery, the Joint Venture recorded a 402 km2 3D survey over the Elang Trend. Elang-2, an appraisal well spudded in September 1994 prior to receipt of the 3D data, established the lateral continuity of the Montara beds reservoirs. Flow rates of 6,080 BOPD (5,300 STBOPD) and 7,500 BOPD (5,970 STBOPD) from separate intervals have confirmed that high deliverabilities can be expected from individual sandstones. Further appraisal drilling is planned in the first half of 1995. This is expected to lead to commercial development of the field.

scholarly journals New Insights on the Impact of Tidal Currents on a Low-gradient, Semi-enclosed, Epicontinental Basin—the Curtis Formation, East-central Utah, USA

2018 ◽  
Vol 5 ◽  
pp. 131-165 ◽  
Author(s):  
Valentin Zuchuat ◽  
Arve R.N. Sleveland ◽  
Douglas A. Sprinkel ◽  
Algirdas Rimkus ◽  
Alvar Braathen ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Seismic Activity ◽  
Late Jurassic ◽  
The South ◽  
East Central ◽  
The North ◽  
Facies Associations ◽  
Composite Nature ◽  
Sandy Substratum ◽  
Deformational Event

Based on a methodic sedimentological analysis, the Late Jurassic (Oxfordian) Curtis Formation unravels the intricate facies variability which occurs in a tide-dominated, fluvially starved, low-gradient, semi-enclosed epicontinental basin. This unit crops out in east-central Utah, between the eolian deposits of the underlying Middle Jurassic (Callovian) Entrada Sandstone, from which it is separated by the J-3 unconformity, and the conformable overlying supratidal Summerville Formation of Oxfordian age. A high-resolution sedimentary analysis of the succession led to the recognition of eight facies associations (FA) with six sub-facies associations. Based on the specific three-dimensional arrangement of these eight facies associations, it is proposed to separate the Curtis Formation into three sub-units: the lower, middle and upper Curtis. The J-3 unconformity defines the base of the lower Curtis, which consists of upper shoreface to beach deposits (FA 2), mud-domi­nated (FA 3a) and sand-dominated heterolithic subtidal flat (FA 3b), sand-rich sub- to supratidal flat (FA 4a) and correlative tidal channel infill (FA 4c). It is capped by the middle Curtis, which coincides with the sub- to intertidal channel-dune-flat complex of FA 5, and its lower boundary corresponds to a transgressive surface of regional extent, identified as the Major Transgressive Surface (MTS). This surface suggests a potential correlation between the middle and the upper Curtis and the neighboring Todilto Member of the Wanakah Forma­tion or Todilto Formation. The upper Curtis consists of the heterolithic upper sub- to intertidal flat (FA 6) and coastal dry eolian dunes belonging to the Moab Member of the Curtis Formation (FA 7), and it conformably overlies the middle Curtis. The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis Formation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation. This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over­pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis. The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis For­mation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation. This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over­pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis.

scholarly journals Last Cretaceous Geology of Taranaki Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Glenn Paul Thrasher
Keyword(s):  
New Zealand ◽  
Late Cretaceous ◽  
Coastal Plain ◽  
New Caledonia ◽  
Strike Slip ◽  
Source Rocks ◽  
Petroleum Exploration ◽  
Petroleum Reservoir ◽  
The North ◽  
Potential Source Rock

<p>Taranaki Basin is a large sedimentary basin located along the western side of New Zealand, which contains all of this countries present petroleum production. The basin first formed as the late-Cretaceous Taranaki Rift, and the first widespread sediments are syn-rift deposits associated with this continental rifting. The Taranaki Rift was an obliquely extensional zone which transferred the movement associated with the opening of the New Caledonia Basin southward to the synchronous Tasman Sea oceanic spreading. Along the rift a series of small, en-echelon basins opened, controlled by high-angle normal and strike-slip faults. These small basins presently underlie the much larger Taranaki Basin. Since the initial rift phase, Taranaki Basin has undergone a complex Cenozoic history of subsidence, compression, additional rifting, and minor strike-slip faulting, all usually involving reactivation of the late-Cretaceous rift-controlling faults. One of the late-Cretaceous rift basins is the Pakawau Basin. Rocks deposited in this basin outcrop in Northwest Nelson as the Pakawau Group. Data from the outcrop and from wells drilled in the basin allow the Pakawau Group to be divided into two formations, the Rakopi Formation and the North Cape Formation, each with recognizable members. The Rakopi Formation (new name) is a sequence of terrestrial strata deposited by fans and meandering streams in an enclosed basin. The North Cape Formation is a transgressive sequence of marine, paralic and coastal-plain strata deposited in response to regional flooding of the rift. The coal-measure strata of the Rakopi Formation are organic rich, and are potential petroleum source rocks where buried deeply enough. In contrast, the marine portions of the North Cape Formation contain almost no organic matter and cannot be considered a potential source rock. Sandy facies within both formations have petroleum reservoir potential. The Rakopi and North Cape formations can be correlated with strata intersected by petroleum exploration wells throughout Taranaki Basin, and all syn-rift sediments can be assigned to them. The Taranaki Rift was initiated about 80 Ma, as recorded by the oldest sediments in the Rakopi Formation. The transgression recorded in the North Cape Formation propagated southwards from about 72 to 70 Ma, and the Taranaki Rift remained a large marine embayment until the end of the Cretaceous about 66.5 Ma. Shortly thereafter, a Paleocene regression caused the southern portions of Taranaki Basin to revert to terrestrial (Kapuni Group) sedimentation. The two distinct late Cretaceous sedimentary sequences of the Rakopi and North Cape formations can be identified on seismic reflection data, and the basal trangressive surface that separates them has been mapped throughout the basin. This horizon essentially marks the end of sedimentation in confined, terrestrial subbasins, and the beginning of Taranaki Basin as a single, continental-margin-related basin. Isopach maps show the Rakopi Formation to be up to 3000m thick and confined to fault- controlled basins. The North Cape Formation is up to 1500m thick and was deposited in a large north-south embayment, open to the New Caledonia basin to the northwest. This embayment was predominantly a shallow-marine feature, with shoreline and lower coastal plain facies deposited around its perimeter</p>

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