Sediment core IR-GC1, from the abyssal basin of the Indian Ocean off Sumatra, may provide important information on depositional events related to earthquakes and tsunamis. In this study, based on a combination of grain-size analysis with lithological studies and oxygen isotope stratigraphy, seven deep-sea turbidite layers were identified, corresponding to seven turbidity events that occurred at 128–130, 105–107, 98–100, 86–87, 50–53, 37–41 and 20–29 ka. The sediments of the turbidite deposits are characterized by coarse grain sizes, poor sorting, wide kurtosis, bimodal frequency distributions and clear depositional variations. Particle size grading is also an important signature of deep-sea turbidite deposits and can be used as an indicator to identify turbidite layers. Possible triggering mechanisms for the turbidite events include tsunamis, earthquakes, volcanic eruptions and sea-level changes.