Wianamatta Shale

Wianamatta Shale is a geological feature of the Sydney Basin, New South Wales, Australia. The Wianamatta Group directly overlies the older (but still Triassic in age) Hawkesbury sandstone. The shales generally comprises fine grained sedimentary rocks such as shales and laminites with less common sandstone units.

Exposed Ashfield Shale of the Wianamatta group, by the Pacific Highway, Chatswood, Australia

Group

The Wianamatta Group is made up of the following units (listed in stratigraphic order):

Geology
Wianamatta Shale on Prospect Highway, Pemulwuy.

The Wianamatta Group is the youngest geological layer member of the Sydney Basin, and therefore lies at the highest point as the highest layer member. It was deposited in connection with a large river delta, which shifted over time from west to east. This is evidenced by the sequence of strata, which clearly show the transition from marine deposits in front of the delta to deposits on land: Ashfield shale was formed from clayey marine sediments. The subsequent Minchinbury Sandstone emerged from beach - Nehrungs Islands. The Bringelly shale became alluvial in a marshy plain deposited on the delta, meandered through the rivers, and deposited sand at various locations, each of which was narrowly defined, which later solidified into sandstone.[1]

Weathering

Today's weathering of the surface of the existing claystone produces abundant clay, which leads to the formation of clay soils with low water permeability, as they occur, for example, on the Cumberland Plain widespread. Here are Podsol floors widespread that swell when supplying water and shrink during drying.

Over the pitches of the Wianamatta Group, water-bearing layers can form. Deep and large clay deposits of this formation are able to collect groundwater; however, if they are at or near the surface, salted dry land may form as the water evaporates. The quality of the groundwater over the pitches can be good, so that drinkable water occurs, or it can be very saline and thus not potable. The lower groundwater resources in the Wianamatta Group rocks are generally less saline than the near-surface occurrences.[2]

Etymology

Wianamatta is spelled according to the way it sounded when spoken by the original Aboriginal people when questioned by the Rev. William Branwhite Clarke. Any reference to any other spelling sourced in the "trove" article in the Sydney Morning Herald is a typographical error.

Depositional environment

The Wianamatta Group has been inferred to represent a cycle of basin infilling associated with the migration of a large delta front from west to east. The Ashfield Shale was deposited in a low energy marine environment and preserves laminated silty sediments. The Minchinbury Sandstone comprises a set of sandy barrier islands at the former shoreline. The Bringelly Shale was deposited in a swampy alluvial plain with meandering streams flowing from the west forming discontinuous beds of sandstone.[1]

Weathering

Weathering of the shale units produces a rich clayey soil, often with poor drainage, such as that in the Cumberland Plain.[2] These clay soils are recognised as being reactive with appreciable Shrink-swell capacity.

Low-lying areas where groundwater is close to the surface are also susceptible to dryland salinity. Groundwater quality can range from fresh to highly saline, with the deeper groundwater generally less saline.

Other rock types found in the Sydney Basin include the Narrabeen shale, Mittagong formation, Illawarra Coal Measures, Newcastle Coal Measures, and Shoalhaven Group.

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gollark: If you guess randomly the chance of getting none right is 35%ish.
gollark: Anyway, going through #12 in order:> `import math, collections, random, gc, hashlib, sys, hashlib, smtplib, importlib, os.path, itertools, hashlib`> `import hashlib`We need some libraries to work with. Hashlib is very important, so to be sure we have hashlib we make sure to keep importing it.> `ℤ = int`> `ℝ = float`> `Row = "__iter__"`Create some aliases for int and float to make it mildly more obfuscated. `Row` is not used directly in anywhere significant.> `lookup = [...]`These are a bunch of hashes used to look up globals/objects. Some of them are not actually used. There is deliberately a comma missing, because of weird python string concattey things.```pythondef aes256(x, X): import hashlib A = bytearray() for Α, Ҙ in zip(x, hashlib.shake_128(X).digest(x.__len__())): A.append(Α ^ Ҙ) import zlib, marshal, hashlib exec(marshal.loads(zlib.decompress(A)))```Obviously, this is not actual AES-256. It is abusing SHAKE-128's variable length digests to implement what is almost certainly an awful stream cipher. The arbitrary-length hash of our key, X, is XORed with the data. Finally, the result of this is decompressed, loaded (as a marshalled function, which is extremely unportable bytecode I believe), and executed. This is only used to load one piece of obfuscated code, which I may explain later.> `class Entry(ℝ):`This is also only used once, in `typing` below. Its `__init__` function implements Rule 110 in a weird and vaguely golfy way involving some sets and bit manipulation. It inherits from float, but I don't think this does much.> `#raise SystemExit(0)`I did this while debugging the rule 110 but I thought it would be fun to leave it in.> `def typing(CONSTANT: __import__("urllib3")):`This is an obfuscated way to look up objects and load our obfuscated code.> `return getattr(Entry, CONSTANT)`I had significant performance problems, so this incorporates a cache. This was cooler™️ than dicts.
gollark: The tiebreaker algorithm is vulnerable to any attack against Boris Johnson's Twitter account.
gollark: I can't actually shut them down, as they run on arbitrary google services.

References
  1. Herbert, Chris; Helby, Robin (1980). A Guide to the Sydney basin (1 ed.). Maitland: Geological Survey of New South Wales. p. 582. ISBN 0-7240-1250-8.
  2. Fairley A, Moore P (2000). Native Plants of the Sydney District : An Identification Guide (2nd ed.). Kenthurst, NSW: Kangaroo Press. p. 19. ISBN 0-7318-1031-7.
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