Ambuja Cements Ltd reported a 90 per cent year-on-year plunge in consolidated net profit to Rs 236 crore for the September quarter, as higher fuel and logistics costs and seasonal weakness squeezed operating margins at the Adani Group company. EBITDA per tonne fell to ₹770 from ₹1,061 a year earlier, while the EBITDA margin contracted to 13.8 per cent from 19.2 per cent.