Geology
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The relatively newly formed Geology Group meets on the Fourth Friday of each month at 2 pm in the Magnolia Room, 12 Gumfield Drive, Warkworth.
Our group currently comprises approximately 50 enthusiastic, mainly ‘citizen scientists,’ and new members are welcomed.
Our sessions are varied and cover a wide range of geological topics. While subjects of general geological interest are addressed, talks and lectures concentrate primarily on the geological history of New Zealand, with focus being placed on the complex but fascinating geological evolution of Northland, and the Auckland-Whangarei area in particular.
While monthly presentations and regular field trips are led mainly by our convenor, Dr Willo Stear, guest speakers and excursion guides also include invited specialists in their respective fields of geology. Member participation as presenters is encouraged and, as our group grows, it is anticipated that this form of session will become increasingly popular. The sessions finish with afternoon tea and discussion.
Our objective is to have vibrant interaction and fun while learning about the origins and characteristics of the rocks that constitute the foundations of our natural environments.
Convenor: Dr Willo StearEmail Willo
“The world is the geologist's great puzzle-box;
he stands before it like the child to whom the separate pieces of his puzzle remain a mystery till he detects their relation and sees where they fit, and then his fragments grow at once into a connected picture beneath his hand.”
- Alexander Agassiz
2024 Events
September 27 The Earth’s Earliest Archean Continent, its Life-forms and their role in making the World’s Largest Gold Deposit – Dr Willo Stear
August 23 The Structure and Landforms of Sedimentary Rocks in Morocco – Lorraine Nelson
July 26 Marine Limestone Deposits and The Aurora/Te Anau-Au Limestone Caves – Adrienne Wright
June 28 Volcanoes of New Zealand – Dr Ian Smith
May 24 Trace fossil evidence of the passage of early humans and animals across cemented beach and dune deposits in South Africa – Dr Willo Stear
April 26 Geological Observations at Baylys Beach - Marilyn Goodwin (Coastal & Shallow Marine Deposits)
March 22 Engineering geology consideration for the next Waitamata harbour crossing - Roger Williams
March 10 Field Trip - Exploring sandstone coastal rock outcrops at Tawharanui Regional Park - Leader Bruce Hayward
March 2 Field Trip - Exploring turbidity deposits at Waiwera - Leader Dr Willo Stear
February 23 Deep marine sediments - Turbidites
January 26 Sedimentary depositional environments - Alluvial system
2 March 2024:
A field trip under Willo’s guidance was undertaken to the wave-cut platform and coastal cliffs at Waiwera, where a submarine canyon-derived, mass flow deposit (debris flow conglomerate - so-called ‘Parnell Grit’) and related soft sediment folding and slump structures in the turbidite sedimentary rock sequence are particularly well exposed.
23 February 2024:
The subject of Dr Willo Stear’s presentation was: Sedimentary Rocks and their Depositional Systems (Part 2). This talk focussed on sedimentary deposits formed by turbidity currents in deep marine environments (turbidites). Typical sedimentary structures occurring in such deposits were illustrated, including text-book examples in freshly exposed road cuttings along the new Puhoi-Warkworth highway.
26 January 2024:
The subject of Dr Willo Stear’s presentation was: Sedimentary Rocks and their Depositional Systems (Part 1). The talk covered the various types of sedimentary rocks,their classification and respective environments of deposition, focussing on alluvial systems and fluvial (river-derived) deposits.
26 November 2023:
A field trip along the coastal cliffs south of Omaha Beach to view deep water turbidite deposits of the Waitemata Group was led by renowned New Zealand geologist and author, Dr Bruce Hayward.
27 October 2023:
The subject of Dr Willo Stear’s presentation was; Climate Change – What Does Geology and the Anthropocene Epoch’s History Tell Us? The talk dealt with some of the geological and other evidence put forward by a body of earth scientists who, on geological grounds, challenge the assertion by climate scientists that humans are the primary culprits responsible for global warming through their polluting of the atmosphere with greenhouse gases.
22 September 2023:
The subject of Dr Ian Smith’s presentation was: What is a Volcano? The talk provided an insight into the geology of volcanoes, describing the many different shapes that volcanoes take. It explained what magma is and what eruption styles and types of volcanoes are formed when magma reaches the Earth’s surface.
26 August 2023:
A field trip to Goat Island was led by Dr Willo Stear, where the basal rocks of the Waitamata Group are exposed in the coastal cliffs below the marine research station. Here, shallow water deposits and trace fossils that had formed in the subtidal zone of the Waitemata Basin’s ancient coastal zone were examined.
28 July 2023:
The subject of Dr Willo Stear’s presentation was: Determining the Ages of Rocks and Fossils. The talk dealt with some of the methods used to date rocks and how geologists, palaeo-anthropologists and archaeologists determine the ages of fossils. It included a discussion on the dating of fossilised tracks (prehistoric animal and human), also highlighting the recent discovery in South Africa of the world’s oldest fossilised human footprint, and its age confirmation.
1 July 2023:
A field trip to Matheson Bay was led by Dr Ian Smith, where the geological contact zone between the basement (foundation) greywackes of the Waipapa Terrane and the basal sedimentary deposits of the Waitemata Group were examined. The latter comprise shallow water conglomerates, breccias and gritty sandstones that were deposited along a rocky shoreline of the Waitemata Basin some 20 million years ago.
26 May 2023:
The subject of the presentation by Dr Ian Smith was: The Geology of Northland. The talk provided a more detailed insight into the geological evolution of the Northland region than had been covered in the previous lectures, focussing on the basement greywacke rocks of the Waipapa Terrane, the extent and complex geology of the Northland Allochton, the sedimentary environments and internal structures of the Waitemata Group and the role that various volcanoes played during the formation of Northland’s geological framework over the past 20 million years. Examples were given of prominent rock outcrops demonstrating some of the pertinent features of the depositional and eruptive history of the region.
28 April 2023:
The subject of Dr Willo Stear’s presentation was: Aotearoa New Zealand: A Geological Tale of Two Islands. The talk dealt with the origin of New Zealand’s basement (foundation) rocks and how the geological events that took place after the breakaway of Zealandia from Gondwana determined that rocks exposed on surface in the South Island are generally older (and more mountainous) than those in the North Island. Examples were given of when and how some of the commonly known rock formations on both islands formed as New Zealand’s two island landmasses adjusted to plate tectonic movements along the collision boundary between the Australian and Pacific Plates
24 March 2023:
The subject of Dr Willo Stear’s presentation was: Continental Drift and the Birth of New Zealand. The talk described how the theory of Continental Drift was proved, how continents were made and broken through geological time and how plate tectonic movements determine what types of sedimentary basins form in oceans and on continents. Reconstruction of the ancient continent of Gondwana was explained as a prelude to describing how ancestral New Zealand was born from out of the ocean under the forces of plate tectonics along Gondwana’s southern margin.
24 February 2023
The inaugural meeting of the Geology Group comprised two presentations, respectively by Dr Willo Stear (convenor) and Dr Ian Smith (former professor of geology at Auckland University). Willo’s presentation was entitled; Introduction to the Principals of Geology, a talk which covered Earth’s layered structure, Plate Tectonics and Continental Drift, Rock Types and the Rock Cycle, Geological Time and the Stratigraphic Column and Fossils, Time and Biostratigraphy. Ian’s presentation, entitled; The Dating Game, explained how Geological Time and the Geological Time Scale were determined.