The Lingam Purana states

The Lingam Purana states 

गंध-वर्ण-रसहिंनं शब्द-स्पर्शादिवर्जितं ॥

meaning:

The foremost Lingam which is devoid of colour, taste, hearing, touch etc is spoken of as Prakriti or nature.

The nature itself is a Lingam (or symbol) of Shiva. When we see nature, we infer the presence of its creator – Shiva. Shiva Lingam is the mark of Shiva the creator, Shiva the sustainer and Shiva the destructor. It also dispels another myth in which Shiva is considered only as a destructor.

Another authentic reference comes from Skanda Purana where lingam is clearly indicated as the supreme Shiva from where the whole universe is created and where it finally submerges.

आकाशं लिंगमित्याहु: पृथ्वी तस्य पीठिका।
आलय: सर्व देवानां लयनार्लिंगमुच्यते ॥
(स्कन्द पुराण)

The endless sky (that great void which contains the entire universe) is the Linga, the Earth is its base. At the end of time the entire universe and all the Gods finally emerge in the Linga itself.

Now this should clarify the settle the doubts once and forever.

Om Namah Shivay.