Both Shiva and Shakti are called Turiya.
The Fourth (Turiya) is thought of as that which is not conscious of the internal world, nor conscious of the external world, nor conscious of both the worlds, nor dense with consciousness, nor simple consciousness, nor unconsciousness, which is unseen, actionless, incomprehensible, un-inferable, unthinkable, indescribable, whose proof consists in the identity of the Self (in all states), in which all phenomena come to a cessation, and which is unchanging fourth (Turiya), peaceful (Shanta), auspicious Shiva, and non-dual. That is the Self; that is to be known. 7.
Pancha Brahma Upanishad.:
10-13. Tatpurusha is said to be covered by the sphere of air. It has five fires, protects effects of mantras, personification of the fifty consonants, has the form of Atharva Veda, is the chief of several crores of Ganas, has the shape which is extremely big, red coloured, gives whatever is asked for, medicine for worry and diseases and the root of Srishti (creation), Sthithi (upkeep) and Laya (merging). It is the basis of all strengths. It is the Turiya which is beyond the three common states and is the thing called Brahman. It is worshipped by Brahma, Vishnu, etc. It is the Supreme Father from which all others originate.
Om. The Goddess was indeed one in the beginning. Alone she emitted the world-egg. (She) is known as Love’s Part (IM). (She) is known as the half-syllabic instant after OM. 1.
Srimad Devi Bhagwatam 5.1.:
The letter A is Bhagvān Brahmā ; the letter “U” is Bhagvān Hari; the letter “M” is Bhagvān Rudra and the half letter ma is Maheśvarī, the Supreme Mother of the universe. The sages, therefore, consider Viṣṇu superior to Brahmā; they again consider Rudra superior to Viṣṇu and Māheśvarī (Turīya State) again superior to Rudra. The speciality of the half letter is that it can never be uttered; it is the symbol of the Eternal Devī.
Again, Both Shiva and Shakti are Turiyateeta.:
Sri Shiva Purana 2.1:1:8.:
4-5. “What shall be this great sound?” thinking like this I stood perplexed. Viṣṇu who is worthy of respect from all the Gods, who is free from all inimical thoughts, saw with the delightful heart, the eternal being’s manifestation on the right side of the liṅga. First, he saw the syllable “A” and he saw the syllable “U” thereafter.
6-10. He saw the syllable “M” in the middle and Nāda (the mystical sound) in the form “Oṃ” in the end. He saw the first syllable on the right like the blazing sphere of the sun. O foremost of sages, thereafter he saw the syllable “U” dazzling like fire. In the middle he saw the syllable “M” glittering like the lunar sphere. Above that what he saw was the supreme Brahman, the greatest refuge. It had the lustre of the pure crystal. It was the pure Being beyond (atita) the Fourth (Turīya), the unsullied & free from extraneous harassment. It was free from mutually clashing opposites. It was single (isolated), void, free from exterior and interior though stationed in the exterior and the interior, devoid of beginning, middle and end, the primordial cause of Bliss, the truth, The Bliss and the Nectar.
Pancha Brahma Upanishad.:
14-18a. You should understand that Ishana is the witness for intelligence and is the activator of the brain. It is the aspect of sky and cannot be seen. It is decorated by the sound of “Aum”. All the Devas are its forms. It is peaceful. It is beyond peace (Shantateeta). It is beyond sound. It is Aa and occupies the headship of vowels. It is the form of Pancha Brahma which is everywhere and activates the five actions of creation, upkeep, destruction, disappearance and blessing. It hides the Pancha Brahmas within itself and exists as itself and shines beyond the Pancha Brahmas (Pancha Brahmateeta) by its light. It shines in the beginning, middle and end without any causative reason.
III-4. I am devoid of honour and dishonour, I am without attributes (nirguna), I am Shiva, I am beyond duality (dvaita/1st, 2nd, 3rd) and non-duality (advaita/4th), I am free from the pairs (of opposites), I am He.
Brahmanda Purana.: Lalita Sahasranama: verse 226.:
“She is the fifth, the lordess of the five elements, and worshiped with methods comprising five”.
Srimad Devi Bhagwatam 12.8.:
O King! Hearing this, the Umā Parvatī Maheśvarī Bhagavatī replied to Indra.,
62-83. ". . Brahmā, Viṣṇu and Maheśa are of the nature of the three guṇas. Brahmā has the Rājo guṇa in Him preponderating; in Viṣṇu, the Sāttva guṇa preponderates and in Maheśa, the Cause of all Causes, is said to reside the Tāmo guṇa. Brahmā is known as of the Gross Body; Viṣṇu is known as of the Subtle Body; and Rudra is known as of the Causal Body and I am known as Turīya, transcending the Guṇas.
This Turīya Form of Mine is called the state of equilibrium of the Guṇas. It is the Inner Controller of all. Beyond (Atīta) this there is another state of Mine which is called the Formless Brahmā (Brāhmaṇ having no Forms). Know, verily, that my Forms are two, as they are with or without attributes (Saguṇa or Nirguṇa). That which is beyond Māyā and the Māyic qualities is called Nirguṇa (without Prākritic attributes) and that which is within Māyā is called Saguṇa. . ."
In the above verses, Mata Uma described Lord Indra about the nature of Brahman (Yaksha/Maya), which is an extension of the Kena Upanishad.
As for the Chakras.:
Srimad Devi Bhagwatam 7.35.:
44-45. Above that is situated betwixt the eyebrows the exceedingly beautiful Ajñâ Chakra with two petals comprising the two letters "Ha," and Ksa. The Self resides in this lotus. When persons are stationed here, they can see everything and know of the present, past and future. There one gets the commands from the Highest Deity (e. g. now this is for you to do and so on); therefore it is called the Ajñâ Chakra.
46-47. Above that is the Kailâs'a Chakra; over it is the Rodhinî Chakra. O One of good vows! Thus I have described to you all about the Âdhâra Chakras. The prominent Yogis say that above that again, is the Vindu Sthân, the seat of the Supreme Deity with thousand petals. O Best of Mountains! Thus I declare the best of the paths leading to Yoga.
Now, Turiya state is not in Sahasrara Chakra but is in the Rodhini/Nirvana/Bodhini Chakra present in the Brahmarandhra region above the end of Sushuma nadi. The State of Turiya in yoga is called the state of Unmani where the dissolution of Manas takes place.
Above Ajna Chakra is Manas (Sun) Chakra, then Indu (Soma) Kailasha Chakra and then Nirvana/Bodhini/Shanta (Fire) Chakra. These 3 Chakras are called as Trikutas and here is the seat of Shakti with Shiva.
Note.: Bodhini is both a Chakra and Shakti and both are different.
It has been stated that there are three pithas
(literally seats, but technically chakras) named
bindu, nada and shakti as the lotuses in the
forehead. (Shiva Sanghita, 5.149).
So, the 3 kutas are Nada (Manas Chakra), Shakti (Indu Chakra), Bindu (Bodhini Chakra).
Note.: Don't confuse the above Bindu with the Para Bindu present in Sahasrara Chakra.
Manas Chakra is mentioned as Jnananetra (knowledge-light),
in the Soubhagya Lakshmi Upanishad, 3.7.
67-69. Pierces the Brahmagranthi formed of rajas and flashes at once like lightning at the mouth of Susumna. Then it goes up at once through Vishnugranthi to the heart. Then it goes up through Rudragranthi and above it to the middle of the eyebrows; having pierced this place (Ajna Chakra), it goes up to the Mandala (sphere) of the moon (Indu Chakra). It dries up the moisture (amrita/soma) produced by the moon in the Anahata (Indu) Chakra having sixteen petals.
Note.: Don't confuse this Anahata Chakra with the Heart Chakra of 12 Petals.
Mandala Brahmana Upanishad.:
1.3. Know that Yoga is twofold through its division into the Purva (earlier) and the Uttara (later). The earlier is Taraka and the later is Amanaska (the mindless). Taraka is divided into Murti (with limitation) and Amurti (without limitation). That is Murti Taraka which goes to the end of the senses (or exist till the senses are conquered in Ajna Chakra). That is Amurti Taraka which goes beyond the two eyebrows (above the senses in Indu Kailasha Chakra). Both these should be performed through Manas. Antar-Drishti (internal vision) associated with manas comes to aid Taraka. Tejas (spiritual light) appears in the hole between the two eyebrows. This Taraka is the earlier one. The later is Amanaska (in Bohini Chakra). The great Jyotis (light) is above the root of the Talu (Sikha/Crown/Palate). By seeing it, one gets the Siddhis Anima, etc. Sambhavi-Mudra occurs when the Lakshya (spiritual vision) is internal while the (physical) eyes are seeing externally without winking. This is the great science which is concealed in all the Tantras. When this is known, one does not stay in Samsara. Its worship (or practice) gives salvation. Antar-Lakshya is of the nature of Jala-Jyotis (or water-Jyotis). It is known by the great Rishis and is invisible both to the internal and external senses.
103-105. When it (Nada) goes to the hole of Akasa, it resembles that of the peacock. In the middle of the cave of the skull/kapala (Forehead) between the four doors (Turiya state) shines Atman, like the sun in the sky. Here, in between the two kodanda bows (eyebrows) and the Brahma-hole (Brahmarandhra), the Shakti is situated. After absorbing the manas (mind) there (in Brahmarandhra) and becoming an amanasa, one will see the Purusha as his own Atman (Self) in a place brightening with Gems, Nada and Bindu, which is the seat (param padam) of Maheshvara (The Great Lord). That man who understands this attains Kaivalya. Thus, is the Upanishad.
5.0. "The Manas influenced by worldly objects is liable to bondage; and that (Manas) which is not so influenced by these is fit for salvation. Hence the entire world becomes an object of Chitta; whereas the same Chitta when it is supportless and well-ripe in the state of Unmani, becomes worthy of Laya (absorption in Brahman). This absorption you should learn from me who am the all-full. I (Sun) alone am the cause of the absorption of Manas.The Manas is within the Jyotis (spiritual light) which again is latent in the spiritual sound which pertains to the Anahata (heart) sound. That Manas which is the agent of creation, preservation and destruction of the three worlds - that same Manas becomes absorbed in that which is the highest seat of Vishnu”.
So, in Ajna Chakra the yogi gets Ajna (Taraka Mantra) then goes to Manas Chakra and gets divine knowledge there then gets Soma in Indu Chakra (Lalata Desa) and in Nirvana (Bodhini/Ridhini) Chakra his Manas gets destroyed and he gets the Amanasa Turiya State.
The above 4 Chakras comes under the Ajna Chakra System.
7 casual forms present in this place are.: 2nd Bindu, Ardha Matra (Turiya) Bodhini/Nirodhika/Maya, Cresent Moon Nada (Shiva + Shakti), Plough Shaped Maha Nada (Nadatmata/Shivatmata), Vyapika Anji Shakti, Samani [Indu (Not Chakra)], Unmani (Amanasa Stage).
Unmani have 2 states one Varnavali Akshara Mala Rupa in Nirvana Chakra and other Nirvana Kala Rupa in Sahasrara Chakra in 17th Kala.
2 more stages in Sahasrara are not Vishnuvaktra and Guruvaktra. (Face of Bindu and Nada).
Beyond this is the Sahasrara System which is present in the Void without nadis and divided into 3 parts.:
Lower is the Guru Chakra (where guru resides) connected with Brahmarandhra through the Power Bridge Visarga (:), two vertical dots.
Middle is the Pericarp of the Sahasrara where the Kailasha/Manidweepa is present.
Upper is the Para Bindu in the Maha Shunya (Dhruva Mandala/Sunya Desa). Here Maha Sankhini Kundalini (not to be confused with Sankhini Nadi) coils Shakala Shiva (Shunya) in 3 and half coils and sometimes 8 and get absorbs in the Para Shiva (Parama Akasa) and again returns to the Muladhara Chakra.
A Bindu is like the numer "0", where the outer circumference (vritta) is Kundalini and inner void is Shiva.
98b-101a.: “Raising the breath along the region of Akasa, he should contemplate on Sadashiva in the following manner, as producing happiness, as of the shape of Bindu, and the great god (Mahadeva), as having the shape of Parama Akasa, as shining like pure crystal, as wearing the rising crescent of moon on his head, as having five faces, ten hands and three eyes, as being of a pleased countenance, as armed with all weapons, as adorned with all ornaments, as having Uma (the goddess) in one-half of his body, as ready to grant favours and as the cause of all the causes”.
Mandala Brahmana Upanishad.:
1.4. Sahasrara (viz., the thousand-petalled lotus of the pineal gland) Jala-Jyotis is the Antar-Lakshya. Some say the form of Purusha in the cave of Buddhi beautiful in all its parts is Antar-Lakshya. Some again say that the all-quiescent Nilakantha accompanied by Uma (his wife) and having five faces and latent in the midst of the sphere in the brain is Antar-Lakshya. Whilst others say that the Purusha of the dimension of a thumb is Antar-Lakshya. A few again say Antar-Lakshya is the One Self made supreme through introvision in the state of a Jivanmukta. All the different statements above made pertain to Atman alone. He alone is a Brahma-Nishtha who sees that the above Lakshya is the pure Atman. The Jiva which is the twenty-fifth Tattva, having abandoned the twenty-four Tattvas, becomes a Jivanmukta through the conviction that the twenty-sixth Tattva (viz.,) Paramatman is ‘I’ alone. Becoming one with Antar-Lakshya (Brahman) in the emancipated state by means of Antar-Lakshya (introvision), Jiva becomes one with the partless sphere of Param-Akasa. Thus ends the first Brahmana.
Yoga Kundalini Upanishad.:
Kundalini assumes the eight forms of Prakriti (matter) and attains Shiva by encircling him and dissolves itself in Shiva (in Sahasrara). 74.
A little summary to the inside of Sahasrara Chakra according to the various tantras.:
Sahasrara Kamala is the Surya Mandala where Ka means Sun and Mala means Rays.
In the pericarp of Sahasrara is the circular moon-region or chandra mandala (Ocean of Nectar). Then, the luminous triangle/Kailasha/Manidweepa (inside the moon-region) and ama-kala (inside the triangle), then ama-kala is subtle, shining in colour and crescent-shaped (in one-half coil) and nirvana-kala (inside ama-kala) and nirvana-kala is very subtle, shining red in colour, and crescent-shaped (in one-half coil), then nirodhika-fire/agni-mandalam (within nirvana-kala), matrika mandala inside it, nirvana shakti (inside niridhika-fire), nirvana shakti is extremely subtle and is the Matrika Shakti, and shining red in colour void (above Matrika Loka), void (Sunya Desa/Dhruva Mandala/Jala Bindu) is in the form of a circle and is the centre of Supreme Bindu. Visarga; its first point is just beyond ama-kala, and the second point is just below Supreme Bindu. Divine Sharikhini who is above the second point of Visarga, and extends from Supreme Bindu, passing through Supreme Nada, Shakti principle to Sakala Shiva in coils, and then is absorbed into Parama Shiva [the Absolute].
Note.: It can be confusing as terms like bindu, kala, nada, triangle, Brahmarandhra, Sankhini, Bodhini, Niridhika, Surya, Chandra, Agni Mandalas, Kailasha, Manidweepa, etc keeps on repeating. Especially some in almost every chakras. .
Anyways, the fact of the matter is except the primary 7 chakras the rest of the chakras are either skipped or have different names and sometimes position in different texts. But, One thing is for sure that every stage has Shiva and Shakti in it. So, it doesn't matter even that stage belongs to either or both of them.
I hope this helps. Prd..